{"id":1882,"date":"2026-10-20T08:51:55","date_gmt":"2026-10-20T08:51:55","guid":{"rendered":"https:\/\/laseristanbulclinic.com\/eye-tests-diagnostics\/vep-erg-tests\/"},"modified":"2026-10-20T12:57:48","modified_gmt":"2026-10-20T12:57:48","slug":"vep-erg-tests","status":"publish","type":"page","link":"https:\/\/laseristanbulclinic.com\/en\/eye-tests-diagnostics\/vep-erg-tests\/","title":{"rendered":"VEP &#038; ERG electrophysiology tests"},"content":{"rendered":"<!-- Hero (Photo + summary card) Start -->\n<section class=\"page-hero\" id=\"top\">\n\t<div class=\"phero-inner pad with-media container-fluid\"><div class=\"row\">\n\t\t<div class=\"phero-left col-12 col-lg-7\">\n\t\t\t<div data-hero-in><ol class=\"crumbs\" aria-label=\"Breadcrumb\"><li><a href=\"https:\/\/laseristanbulclinic.com\/en\/\">Home: eye surgery in Istanbul<\/a><\/li><li><a href=\"https:\/\/laseristanbulclinic.com\/en\/treatments\/\">All eye treatments<\/a><\/li><li><a href=\"https:\/\/laseristanbulclinic.com\/en\/eye-tests-diagnostics\/\">Eye examinations &#038; diagnostic tests<\/a><\/li><li><span aria-current=\"page\">VEP &#038; ERG electrophysiology tests<\/span><\/li><\/ol><\/div>\t\t\t<h1 class=\"t64 hero-title phero-title\" data-lines>VEP Test Eye Check and ERG Test: What They Measure and Show<\/h1>\n\t\t\t\t\t\t<p class=\"t22 phero-lead\" data-hero-in>A VEP test eye check (visual evoked potential) records how well the signal from your eye travels along the optic nerve to the vision centre at the back of your brain. An ERG (electroretinogram) records the electrical response of the retina itself. Together they are called visual electrophysiology: painless tests that measure how the visual system works rather than how it looks. At Laser Istanbul Clinic they are used when the cause of reduced vision is not clear from the examination and scans, and your surgeon explains the result with you.<\/p>\n\t\t\t\t\t\t<div class=\"phero-ctas\" data-hero-in><a class=\"pill pill-white\" href=\"https:\/\/laseristanbulclinic.com\/en\/free-consultation\/\"><span class=\"pill-dot\" aria-hidden=\"true\"><\/span><span class=\"pill-label\">Send us your reports for a free review<\/span><\/a><a class=\"pill pill-line\" href=\"https:\/\/wa.me\/4915783739465?text=Hello%20Laser%20Istanbul%20Clinic%2C%20I%20would%20like%20some%20information%20about%20eye%20treatment.%20Sent%20from%3A%20https%3A%2F%2Flaseristanbulclinic.com%2Fen%2F\" target=\"_blank\" rel=\"noopener\"><span class=\"pill-dot\" aria-hidden=\"true\"><\/span><span class=\"pill-label\">WhatsApp us: +49 157 8373 9465<\/span><\/a><\/div><ul class=\"phero-meta\" data-hero-in><li><svg width=\"16\" height=\"16\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg>Medically reviewed by <span class=\"ph\">{{surgeon}}<\/span> \u00b7 Last reviewed <span class=\"ph\">{{date}}<\/span><\/li><\/ul>\t\t<\/div>\n\t\t<div class=\"phero-right has-media col-12 col-lg-5\">\n\t\t\t\t\t\t<figure class=\"phero-media\" data-hero-in><img decoding=\"async\" width=\"603\" height=\"675\" src=\"https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/slit-lamp-eye-examination.webp\" class=\"attachment-large size-large\" alt=\"Eye examination at a slit lamp\" fetchpriority=\"high\" srcset=\"https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/slit-lamp-eye-examination.webp 603w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/slit-lamp-eye-examination-268x300.webp 268w\" sizes=\"(max-width: 603px) 100vw, 603px\" \/><\/figure>\n\t\t\t\t\t\t\t\t\t<div class=\"inshort\" data-hero-in><p>A VEP test eye check measures the electrical signal your brain produces in response to a flashing or checkerboard pattern, which shows whether the optic nerve and visual pathway are conducting normally. An ERG test measures the retina&#8217;s electrical response to light flashes, showing whether the rods and cones work. Both use small sensor electrodes, neither is painful, and a specialist reads them alongside your examination, OCT scan and visual field test, not on their own.<\/p><\/div>\n\t\t\t\t\t<\/div>\n\t<\/div><\/div>\n<\/section>\n<!-- Hero (Photo + summary card) End -->\n\n\n<!-- Heading (Text without a heading) Start -->\n<section class=\"psec pad\" id=\"safety-box\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\"><div class=\"gen-intro prose\"><p data-reveal><strong>Sudden loss of vision, a dark curtain over part of your sight, or new pain on moving the eye is an emergency.<\/strong> Do not wait for a trip abroad: see an eye casualty department or your doctor the same day. VEP and ERG are specialist tests for finding out why vision is reduced, not for urgent care.<\/p><\/div><\/div><\/div><\/div><\/section>\n<!-- Heading (Text without a heading) End -->\n\n\n<!-- FAQ (Question and answer rows) Start -->\n<section class=\"psec pad\" id=\"what-do-vep-and-erg-tests-measure\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\">\n\t\t<h2 class=\"t48 sec-title\" data-reveal>What do VEP and ERG tests measure?<\/h2>\n\t\t\t<p class=\"t22 sec-lead\" data-reveal>Your visual system has several links: the retina, where light is turned into electrical signals; the optic nerve, which carries them; and the brain, which interprets them. Visual electrophysiology tests each link by recording the electrical activity it produces. NHS patient information describes this as measuring how your eyes or brain react to on-screen patterns and flashing lights.<\/p>\n\t\t\t<div class=\"prose sec-pre\"><div class=\"tbl-wrap\" data-reveal><table class=\"tbl rsp\"><thead><tr><th scope=\"col\">Test<\/th><th scope=\"col\">What it records<\/th><th scope=\"col\">Part of the visual system<\/th><th scope=\"col\">Typical question it answers<\/th><\/tr><\/thead><tbody><tr><th scope=\"row\"><strong>VEP<\/strong> (visual evoked potential)<\/th><td data-label=\"What it records\">Signals from the back of the head (occipital scalp) after each eye is stimulated<\/td><td data-label=\"Part of the visual system\">Retina to optic nerve to visual cortex<\/td><td data-label=\"Typical question it answers\">Is the optic nerve or visual pathway conducting normally?<\/td><\/tr><tr><th scope=\"row\"><strong>Full-field ERG<\/strong><\/th><td data-label=\"What it records\">Mass response of the whole retina to flashes in the dark and in the light<\/td><td data-label=\"Part of the visual system\">Rods and cones, bipolar cells<\/td><td data-label=\"Typical question it answers\">Is there widespread retinal disease?<\/td><\/tr><tr><th scope=\"row\"><strong>Pattern ERG<\/strong><\/th><td data-label=\"What it records\">Response to a reversing checkerboard<\/td><td data-label=\"Part of the visual system\">Central retina (macula) and retinal ganglion cells<\/td><td data-label=\"Typical question it answers\">Is the central retina or ganglion-cell layer affected?<\/td><\/tr><tr><th scope=\"row\"><strong>Multifocal ERG<\/strong><\/th><td data-label=\"What it records\">A map of 61\u2013103 small responses across the central 30 degrees<\/td><td data-label=\"Part of the visual system\">Macula<\/td><td data-label=\"Typical question it answers\">Where in the macula is function reduced?<\/td><\/tr><\/tbody><\/table><\/div><p data-reveal>The International Society for Clinical Electrophysiology of Vision (ISCEV) publishes the standards for these tests, so that results can be compared between laboratories. Its 2025 update for the VEP defines three standard stimuli: a pattern-reversal checkerboard, a pattern onset\/offset checkerboard and a flash.<\/p><\/div>\n\t\t\t<div class=\"qa-list\">\n\t\t\t\t<div class=\"qa-row\" data-reveal><div class=\"row\"><h3 class=\"qa-q col-12 col-lg-4\">What is a VEP test?<\/h3><div class=\"qa-a prose col-12 col-lg-8\"><p data-reveal>A VEP test records the electrical signal that your brain generates in response to vision. According to EyeWiki, it measures the signal at the visual cortex in response to visual stimulation, which assesses the whole path from the eye to the cortex. A small electrode is placed on the back of your head (position Oz), a reference sensor on the forehead (Fz) and a ground electrode elsewhere. Each eye is tested separately while you look at the centre of a screen showing a black-and-white checkerboard that flips pattern. The computer averages many responses to pull a clear signal out of the background brain activity.<\/p>\n<p data-reveal>The main part of the trace is a positive peak called <strong>P100<\/strong>, which appears roughly 100 milliseconds after the pattern changes. Its timing (latency) and size (amplitude) are what your specialist measures.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"qa-row\" data-reveal><div class=\"row\"><h3 class=\"qa-q col-12 col-lg-4\">What is an ERG test?<\/h3><div class=\"qa-a prose col-12 col-lg-8\"><p data-reveal>An ERG test records the retina&#8217;s electrical response to light. The ISCEV 2022 standard describes the full-field ERG as a way of assessing generalised retinal function. The key parts of the trace are:<\/p>\n<ul data-reveal>\n<li><strong>a-wave:<\/strong> the first, downward wave, generated by the rod and cone photoreceptors<\/li>\n<li><strong>b-wave:<\/strong> the following upward wave, generated mainly by bipolar cells<\/li>\n<li><strong>Dark-adapted responses:<\/strong> measured after at least 20 minutes in the dark, mainly reflecting the rods<\/li>\n<li><strong>Light-adapted responses:<\/strong> measured after at least 10 minutes in steady light, reflecting the cones<\/li>\n<\/ul>\n<p data-reveal>Because the rods and cones are tested separately, an ERG can show which kind of photoreceptor function is reduced, which helps in naming the type of retinal disease.<\/p><\/div><\/div><\/div>\n\t\t\t<\/div>\n\t<\/div><\/div><\/div><\/section>\n<!-- FAQ (Question and answer rows) End -->\n\n\n<!-- Heading (Intro: heading left, text right) Start -->\n<section class=\"panel\" id=\"what-is-a-vep-test-used-to-diagnose\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\"><div class=\"intro-grid row\"><div class=\"intro-side col-12\"><h2 class=\"t48\" data-reveal>What is a VEP test used to diagnose?<\/h2><\/div><div class=\"copy prose col-12\"><p data-reveal>A VEP test is used to find out whether the optic nerve or the visual pathway behind it is working properly, especially when the eye itself looks healthy. The American Academy of Ophthalmology lists optic neuropathies (demyelinating, compressive, toxic, traumatic, ischaemic, inflammatory and hereditary), albinism, amblyopia, unexplained vision loss and suspected chiasmal or retrochiasmal problems among the indications.<\/p>\n<p data-reveal><strong>Optic neuritis and other optic nerve disease.<\/strong> A review of VEP methods states that a delayed P100 in one eye is typically a sign of optic nerve or pre-chiasmal dysfunction. In optic neuritis, the delay often persists after vision has recovered: a review of multifocal VEP in optic neuritis notes significant residual latency delay even 12 months after the attack.<\/p>\n<p data-reveal><strong>Unexplained vision loss.<\/strong> When vision is worse than the examination explains, a normal VEP is reassuring about the optic nerve and pathway, while an abnormal one points the search towards the nerve.<\/p>\n<p data-reveal><strong>Hidden optic nerve disease.<\/strong> The same review notes that VEP can detect lesions that imaging may miss, particularly within the optic nerve.<\/p>\n<p data-reveal><strong>Glaucoma.<\/strong> VEP is sometimes used alongside OCT and visual fields to follow functional change.<\/p>\n<p data-reveal><strong>Babies, young children and people who cannot respond.<\/strong> Flash VEP is useful when there is media opacity (such as a dense cataract), limited cooperation or an inability to fixate, as the ISCEV 2025 standard notes. EyeWiki also lists monitoring of infant vision among the uses of VEP.<\/p>\n<p data-reveal><strong>Albinism.<\/strong> VEP shows an asymmetry of the response across the scalp caused by misrouting of nerve fibres at the optic chiasm.<\/p>\n<p data-reveal>An ERG test, by contrast, is used to find or confirm:<\/p>\n<ul data-reveal>\n<li>inherited retinal disease: retinitis pigmentosa, cone and rod dystrophies, Leber congenital amaurosis<\/li>\n<li>toxic retinopathy from medicines such as hydroxychloroquine, chloroquine or vigabatrin<\/li>\n<li>acquired retinal conditions, including cancer-associated retinopathy<\/li>\n<li>unexplained vision loss, giving an objective measure when symptoms do not match the examination<\/li>\n<\/ul><div class=\"links-row\" data-reveal><a class=\"link-arrow\" href=\"https:\/\/laseristanbulclinic.com\/en\/optic-neuropathy-treatment\/\">Optic neuropathy and neuro-ophthalmology in Istanbul <svg width=\"18\" height=\"18\" aria-hidden=\"true\"><use href=\"#i-arrow\"\/><\/svg><\/a><\/div><\/div><\/div><\/div><\/div><\/div><\/section>\n<!-- Heading (Intro: heading left, text right) End -->\n\n\n<!-- Process (Step cards: 4 columns) Start -->\n<section class=\"psec pad\" id=\"why-vep-and-erg-may-be-requested-before-treatment\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\">\n\t<div class=\"sec-head is-center row\"><div class=\"col-12\"><h2 class=\"t48 sec-title\" data-reveal>Why VEP and ERG may be requested before treatment<\/h2><\/div><div class=\"col-12\"><p class=\"t22 sec-lead\" data-reveal>These tests are not part of every examination. They are asked for when the standard tests leave a question open. Typical reasons are:<\/p><\/div><\/div>\t\t<ol class=\"steps four row row-cols-1 row-cols-lg-4\" data-stagger>\n\t\t\t\t<li class=\"col\"><div class=\"step h-100\">\n\t\t\t\t\t\t<h3>Vision is poorer than the eye looks<\/h3>\n\t\t\t\t\t\t<p>If the retina looks normal on the OCT scan and the visual field test is unclear, electrophysiology helps separate a retinal cause (ERG) from an optic nerve cause (VEP).<\/p>\n\t\t<\/div><\/li>\n\t\t\t\t<li class=\"col\"><div class=\"step h-100\">\n\t\t\t\t\t\t<h3>Before cataract or lens surgery in an eye with other disease<\/h3>\n\t\t\t\t\t\t<p>A dense cataract hides the back of the eye. If the retina or optic nerve may also be damaged, your surgeon needs to know how much vision can realistically be restored. Flash VEP does not need a clear view of the retina, and EyeWiki lists prognostication before surgery among the uses of VEP.<\/p>\n\t\t<\/div><\/li>\n\t\t\t\t<li class=\"col\"><div class=\"step h-100\">\n\t\t\t\t\t\t<h3>Monitoring medicines that can affect the retina<\/h3>\n\t\t\t\t\t\t<p>The Royal College of Ophthalmologists recommends multifocal ERG in hydroxychloroquine screening when structural changes on OCT or autofluorescence imaging are not matched by a visual field defect.<\/p>\n\t\t<\/div><\/li>\n\t\t\t\t<li class=\"col\"><div class=\"step h-100\">\n\t\t\t\t\t\t<h3>Second opinions<\/h3>\n\t\t\t\t\t\t<p>Patients who have been told their vision loss is unexplained often bring earlier VEP and ERG reports, which we can review without repeating the test.<\/p>\n\t\t<\/div><\/li>\n\t\t\t<\/ol>\n\t\t<div class=\"sec-foot-flow prose\"><p data-reveal>Your surgeon will only request these tests if they could change your advice. If they would not, we will not ask you to have them.<\/p><\/div><\/div><\/div><\/div><\/section>\n<!-- Process (Step cards: 4 columns) End -->\n\n\n<!-- Heading (Intro: heading left, text right) Start -->\n<section class=\"psec pad\" id=\"what-to-expect-the-vep-and-erg-procedure\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\"><div class=\"intro-grid row\"><div class=\"intro-side col-12\"><h2 class=\"t48\" data-reveal>What to expect: the VEP and ERG procedure<\/h2><\/div><div class=\"copy prose col-12\"><div class=\"list-card\" data-reveal><h3>Before the test<\/h3><ul class=\"check-list\"><li><svg width=\"18\" height=\"18\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg><span><strong>Wash your hair<\/strong> and avoid gel, spray or oils; electrodes are stuck to the scalp. Hair weaves and wigs cannot be used.<\/span><\/li><li><svg width=\"18\" height=\"18\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg><span><strong>Avoid heavy eye make-up and false lashes<\/strong> if you are having an ERG.<\/span><\/li><li><svg width=\"18\" height=\"18\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg><span><strong>Bring your glasses<\/strong> and your prescription. ISCEV states that optimal refraction is needed for pattern VEP, but not for flash VEP.<\/span><\/li><li><svg width=\"18\" height=\"18\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg><span><strong>Take your regular medicines<\/strong> as usual.<\/span><\/li><li><svg width=\"18\" height=\"18\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg><span><strong>Bring sunglasses<\/strong> if you will have dilating drops, and arrange not to drive afterwards.<\/span><\/li><li><svg width=\"18\" height=\"18\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg><span><strong>Tell us if you have epilepsy.<\/strong> NHS patient information notes a small theoretical risk that flashing lights could provoke a seizure, though no case has been reported.<\/span><\/li><\/ul><\/div><div class=\"list-card\" data-reveal><h3>During a VEP test<\/h3><ol class=\"plain-ol\"><li>Small disc electrodes are attached to your scalp with a conductive paste.<\/li><li>You sit in front of a screen and look at a fixed spot in the centre of a checkerboard pattern. One eye is covered at a time.<\/li><li>The pattern flips repeatedly while the computer records and averages your brain&#8217;s response. The test is painless and has no after-effects.<\/li><\/ol><\/div><div class=\"list-card\" data-reveal><h3>During an ERG test<\/h3><ol class=\"plain-ol\"><li>You may have numbing drops, and often dilating drops so the retina is evenly lit. The 2022 ISCEV standard now makes dilation optional if the stimulus is corrected for pupil size.<\/li><li>A recording electrode is placed on or close to the eye: a fine thread resting along the lower eyelid, a contact-lens electrode, or a skin pad under the eye. A thread electrode can feel unusual but should not hurt, and it can be adjusted or removed.<\/li><li>You sit in the dark for at least 20 minutes before the dark-adapted flashes, and in steady light for at least 10 minutes before the light-adapted flashes. Keep your phone away, because screen light interrupts dark adaptation.<\/li><li>You look into a dome that delivers flashes of light of different strengths.<\/li><\/ol><\/div><p data-reveal><strong>How long does it take?<\/strong> One NHS leaflet states that testing does not normally last longer than two and a half hours, and another says a full session typically takes about two hours. A VEP alone is shorter than a full ERG session, since it does not need dark adaptation. The time we need for your visit is <span class=\"ph\">{{VEP \/ ERG appointment length}}<\/span>.<\/p>\n<p data-reveal><strong>Risks and after-effects.<\/strong> Scalp electrodes cause none. A contact-lens or thread electrode on the eye can very rarely scratch the cornea (a corneal abrasion), which is avoided by not rubbing your eyes while it is in place. Dilating drops blur near vision and make light uncomfortable, and NHS guidance says you should not drive for around three to five hours.<\/p><\/div><\/div><\/div><\/div><\/div><\/section>\n<!-- Heading (Intro: heading left, text right) End -->\n\n\n<!-- FAQ (Question and answer rows) Start -->\n<section class=\"psec pad\" id=\"how-vep-results-are-read\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\">\n\t\t<h2 class=\"t48 sec-title\" data-reveal>How VEP results are read<\/h2>\n\t\t\t\t\t<div class=\"qa-list\">\n\t\t\t\t<div class=\"qa-row\" data-reveal><div class=\"row\"><h3 class=\"qa-q col-12 col-lg-4\">VEP test normal range<\/h3><div class=\"qa-a prose col-12 col-lg-8\"><p data-reveal>The normal VEP is not a single number. The P100 typically appears at about 100 milliseconds in pattern-reversal recording, but the exact normal limits depend on the stimulus, the equipment and your age. ISCEV therefore advises each laboratory to establish its own reference values rather than rely on figures from elsewhere. The elements your specialist checks are:<\/p><div class=\"tbl-wrap\" data-reveal><table class=\"tbl rsp\"><thead><tr><th scope=\"col\">Measure<\/th><th scope=\"col\">What it shows<\/th><th scope=\"col\">Notes<\/th><\/tr><\/thead><tbody><tr><th scope=\"row\">P100 latency<\/th><td data-label=\"What it shows\">How quickly the signal travels from retina to cortex<\/td><td data-label=\"Notes\">Around 100 ms is typical; compared with the laboratory&#8217;s own normal limits<\/td><\/tr><tr><th scope=\"row\">P100 amplitude<\/th><td data-label=\"What it shows\">How strong the response is<\/td><td data-label=\"Notes\">Varies more between people than latency; measured from the preceding N70 trough<\/td><\/tr><tr><th scope=\"row\">Difference between the two eyes<\/th><td data-label=\"What it shows\">Whether one nerve is slower or weaker<\/td><td data-label=\"Notes\">Very useful in suspected optic neuritis, because each eye serves as the other&#8217;s control<\/td><\/tr><tr><th scope=\"row\">Waveform shape<\/th><td data-label=\"What it shows\">Whether the response is clean and repeatable<\/td><td data-label=\"Notes\">Poor fixation, blinking or uncorrected sight can distort it<\/td><\/tr><\/tbody><\/table><\/div><p data-reveal class=\"note-sm\">These descriptions come from published reviews and standards. They are a guide only; your specialist interprets your own traces against a reference range.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"qa-row\" data-reveal><div class=\"row\"><h3 class=\"qa-q col-12 col-lg-4\">Abnormal VEP test results: what do they mean?<\/h3><div class=\"qa-a prose col-12 col-lg-8\"><p data-reveal>An abnormal VEP does not name a disease by itself. It says that something along the visual pathway is affecting the signal, and the pattern gives clues:<\/p>\n<ul data-reveal>\n<li><strong>Delayed P100 with a reasonably preserved amplitude<\/strong> points towards slowed conduction, as in demyelination (loss of the insulating myelin around nerve fibres).<\/li>\n<li><strong>Reduced amplitude<\/strong> means fewer working nerve fibres or a weaker signal, which may be seen with nerve damage from compression, toxic injury, poor blood supply or glaucoma.<\/li>\n<li><strong>An absent or very small response<\/strong> may reflect severe loss of conduction, but it can also reflect poor fixation, an unsuitable stimulus or dense media opacity, so flash VEP and ERG are used to check.<\/li>\n<li><strong>Asymmetry between the two eyes<\/strong> is often more informative than the absolute value.<\/li>\n<\/ul>\n<p data-reveal>The American Academy of Ophthalmology notes that VEP abnormalities must be correlated with clinical findings and do not by themselves specify a diagnosis.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"qa-row\" data-reveal><div class=\"row\"><h3 class=\"qa-q col-12 col-lg-4\">Reasons for an abnormal VEP test<\/h3><div class=\"qa-a prose col-12 col-lg-8\"><div class=\"tbl-wrap\" data-reveal><table class=\"tbl rsp\"><thead><tr><th scope=\"col\">Group of reasons<\/th><th scope=\"col\">Examples<\/th><\/tr><\/thead><tbody><tr><th scope=\"row\">Optic nerve inflammation or demyelination<\/th><td data-label=\"Examples\">Optic neuritis, multiple sclerosis, neuromyelitis optica spectrum disorder<\/td><\/tr><tr><th scope=\"row\">Compression or injury<\/th><td data-label=\"Examples\">A tumour pressing on the nerve or chiasm, trauma<\/td><\/tr><tr><th scope=\"row\">Poor blood supply or toxins<\/th><td data-label=\"Examples\">Ischaemic optic neuropathy, medicine or nutritional toxicity<\/td><\/tr><tr><th scope=\"row\">Hereditary conditions<\/th><td data-label=\"Examples\">Inherited optic neuropathies, albinism<\/td><\/tr><tr><th scope=\"row\">Eye disease<\/th><td data-label=\"Examples\">Advanced glaucoma, severe retinal disease, dense cataract<\/td><\/tr><tr><th scope=\"row\">Technical or patient factors<\/th><td data-label=\"Examples\">Uncorrected refractive error, poor fixation, small pupil, tiredness or eye movement<\/td><\/tr><\/tbody><\/table><\/div><p data-reveal>Because the technical group is so common, a mildly abnormal VEP is often repeated or checked against an ERG and scans before conclusions are drawn.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"qa-row\" data-reveal><div class=\"row\"><h3 class=\"qa-q col-12 col-lg-4\">ERG test results<\/h3><div class=\"qa-a prose col-12 col-lg-8\"><p data-reveal>An ERG is read by comparing wave sizes and timings with normal limits, and by comparing dark-adapted with light-adapted responses. EyeWiki notes that retinitis pigmentosa typically shows severely abnormal or undetectable dark-adapted responses, while an &#8220;electronegative&#8221; pattern (a normal a-wave but a markedly reduced b-wave) is seen in conditions such as congenital stationary night blindness and X-linked retinoschisis. In hydroxychloroquine toxicity, multifocal ERG can show early changes in the ring of retina just around the central fovea.<\/p><\/div><\/div><\/div>\n\t\t\t<\/div>\n\t<\/div><\/div><\/div><\/section>\n<!-- FAQ (Question and answer rows) End -->\n\n\n<!-- Image + Text (Image left, text right) Start -->\n<section class=\"psec pad split-sec\" id=\"vep-test-for-neurology-and-ms\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\"><div class=\"split\"><div class=\"row\">\n\t\t<div class=\"split-media col-12 col-lg-6\" data-reveal><div class=\"media\" data-parallax><img loading=\"lazy\" decoding=\"async\" width=\"640\" height=\"800\" src=\"https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/corneal-topography-map-819x1024.webp\" class=\"attachment-large size-large\" alt=\"Corneal topography map\" sizes=\"auto, (max-width: 991px) 100vw, 50vw\" srcset=\"https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/corneal-topography-map-819x1024.webp 819w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/corneal-topography-map-240x300.webp 240w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/corneal-topography-map-768x960.webp 768w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/corneal-topography-map.webp 1200w\" \/><\/div><\/div>\n\t\t<div class=\"split-copy col-12 col-lg-6\">\n\t\t\t\t\t\t<h2 class=\"t48\" data-reveal>VEP test for neurology and MS<\/h2>\n\t\t\t\t\t\t<p class=\"t22 lede\" data-reveal>A VEP test is used in neurology as well as ophthalmology, because the optic nerve is part of the central nervous system. It can show whether the visual pathway has been affected by demyelination, even when you have not noticed symptoms.<\/p>\n\t\t\t\t\t\t<div class=\"prose\" data-reveal><p data-reveal>About one quarter of people with multiple sclerosis (MS) have optic neuritis as their first symptom. The 2024 revisions of the McDonald criteria for diagnosing MS, published in <em>The Lancet Neurology<\/em> in 2025, add the optic nerve as a fifth location where the disease can be shown, using MRI of the optic nerves, visual evoked potentials and\/or OCT.<\/p>\n<p data-reveal>Published research shows how useful the VEP can be. In a review of multifocal VEP, 20\u201340% of MS patients&#8217; eyes without a known attack of optic neuritis had signs of a silent episode in the visual pathway. In one small group of 46 people with optic neuritis, 36.4% of those with a delayed VEP developed MS within a year, compared with 0% of those with a normal one. These figures come from specific studies and cannot predict what will happen to one person.<\/p>\n<p data-reveal><strong>An important limit:<\/strong> the diagnosis of MS is made by a neurologist from your history, examination, MRI and other tests together. A VEP result alone neither confirms nor rules out MS. If a VEP raises that question, we will explain the finding and advise you to see a neurologist, ideally in your home country where follow-up is easiest.<\/p><div class=\"links-row\" data-reveal><a class=\"link-arrow\" href=\"https:\/\/laseristanbulclinic.com\/en\/optic-neuropathy-treatment\/\">Optic neuropathy and neuro-ophthalmology in Istanbul <svg width=\"18\" height=\"18\" aria-hidden=\"true\"><use href=\"#i-arrow\"\/><\/svg><\/a><\/div><\/div>\n\t\t\t\t\t\t\t\t\t\t\t<\/div>\n<\/div><\/div><\/div><\/div><\/div><\/section>\n<!-- Image + Text (Image left, text right) End -->\n\n\n<!-- Heading (Intro: heading left, text right) Start -->\n<section class=\"psec pad\" id=\"vep-and-erg-test-price\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\"><div class=\"intro-grid row\"><div class=\"intro-side col-12\"><h2 class=\"t48\" data-reveal>VEP and ERG test price<\/h2><\/div><div class=\"copy prose col-12\"><p data-reveal><strong>Our price for VEP and ERG testing is <span class=\"ph\">{{\u00a3 price for VEP and ERG electrophysiology testing}}<\/span><\/strong>, which covers the tests, the specialist&#8217;s report and an explanation of your results by your surgeon, with an interpreter if you wish. Where the tests are requested as part of treatment planning, <span class=\"ph\">{{whether VEP\/ERG is included in the treatment price or charged separately}}<\/span>. Hotel and transfers are not included; they are a separate charge if you would like us to arrange them.<\/p>\n<p data-reveal><strong>What about the VEP test price in the UK?<\/strong> On the NHS, these tests are normally arranged by a hospital eye clinic or neurology service on referral, and patients are not usually asked to book them directly. Private clinics set their own fees, which depend on how many tests are done. We do not quote UK private prices on this page; send us your reports and we will tell you honestly whether a repeat test is needed at all.<\/p><\/div><\/div><\/div><\/div><\/div><\/section>\n<!-- Heading (Intro: heading left, text right) End -->\n\n\n<!-- Image + Text (Text left, image right) Start -->\n<section class=\"psec pad split-sec\" id=\"who-reads-your-vep-and-erg-results\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\"><div class=\"split rev\"><div class=\"row\">\n\t\t<div class=\"split-media col-12 col-lg-6\" data-reveal><div class=\"media\" data-parallax><img loading=\"lazy\" decoding=\"async\" width=\"640\" height=\"640\" src=\"https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/eye-surgeons-reviewing-scans-istanbul.webp\" class=\"attachment-large size-large\" alt=\"Eye surgeons reviewing scans together in a diagnostic room\" sizes=\"auto, (max-width: 991px) 100vw, 50vw\" srcset=\"https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/eye-surgeons-reviewing-scans-istanbul.webp 1024w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/eye-surgeons-reviewing-scans-istanbul-300x300.webp 300w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/eye-surgeons-reviewing-scans-istanbul-150x150.webp 150w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/eye-surgeons-reviewing-scans-istanbul-768x768.webp 768w\" \/><\/div><\/div>\n\t\t<div class=\"split-copy col-12 col-lg-6\">\n\t\t\t\t\t\t<h2 class=\"t48\" data-reveal>Who reads your VEP and ERG results<\/h2>\n\t\t\t\t\t\t\t\t<div class=\"prose\" data-reveal><p data-reveal>Your traces are recorded by <span class=\"ph\">{{electrophysiology specialist \/ clinical scientist}}<\/span> and then reviewed by the surgeon treating you. <strong>Do\u00e7. Dr. Muhammet Derda \u00d6zer<\/strong> (Do\u00e7. means Associate Professor), who treats retina, uveitis and other inflammatory eye disease, reviews retinal and inflammatory cases and speaks English and Turkish. <strong>Op. Dr. Aysan Bayram<\/strong>, who treats retinal disease, cataract and laser patients and speaks English, also reviews retinal results. <strong>Prof. Dr. Ahmet Sat\u0131c\u0131<\/strong>, whose practice includes glaucoma, cataract and lens surgery, reviews results that affect surgical planning or glaucoma care. Results come with a plain-language explanation and a recommendation, through your interpreter if you wish. <span class=\"ph\">{{Turnaround for the written electrophysiology report}}<\/span>.<\/p>\n<p data-reveal>If your tests point to a neurological cause, we say so plainly and advise you to see a neurologist rather than pretending we can provide neurological care.<\/p><\/div>\n\t\t\t\t\t\t\t\t\t\t\t<\/div>\n<\/div><\/div><\/div><\/div><\/div><\/section>\n<!-- Image + Text (Text left, image right) End -->\n\n\n<!-- Table (Table on a dark panel) Start -->\n<section class=\"panel dark\" id=\"treatments-and-care-vep-and-erg-support\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\">\n\t\t<h2 class=\"t48 sec-title\" data-reveal>Treatments and care VEP and ERG support<\/h2>\n\t\t\t\t<div class=\"tbl-flow\"><div class=\"tbl-wrap\" data-reveal><table class=\"tbl rsp\"><thead><tr><th scope=\"col\">Situation<\/th><th scope=\"col\">How VEP \/ ERG is used<\/th><\/tr><\/thead><tbody><tr><th scope=\"row\"><a href=\"\/en\/optic-neuropathy-treatment\/\">Optic neuropathy and neuro-ophthalmology<\/a><\/th><td data-label=\"How VEP \/ ERG is used\">Shows whether the optic nerve is conducting normally and tracks change over time<\/td><\/tr><tr><th scope=\"row\">Cataract and lens surgery with other eye disease<\/th><td data-label=\"How VEP \/ ERG is used\">Helps judge how much vision the retina and nerve can support once the cataract is removed<\/td><\/tr><tr><th scope=\"row\">Retinal disease and inherited retinal dystrophy<\/th><td data-label=\"How VEP \/ ERG is used\">Confirms the diagnosis and separates rod from cone problems<\/td><\/tr><tr><th scope=\"row\">Medicine monitoring (for example hydroxychloroquine)<\/th><td data-label=\"How VEP \/ ERG is used\">Multifocal ERG confirms or clarifies early macular toxicity<\/td><\/tr><tr><th scope=\"row\">Second opinions on unexplained vision loss<\/th><td data-label=\"How VEP \/ ERG is used\">Provides objective data when scans and examination do not explain symptoms<\/td><\/tr><\/tbody><\/table><\/div><\/div>\t<\/div><\/div><\/div><\/section>\n<!-- Table (Table on a dark panel) End -->\n\n\n<!-- List (Checklist cards) Start -->\n<section class=\"psec pad\" id=\"other-tests-in-your-eye-examination\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\">\n\t<div class=\"sec-head is-center row\"><div class=\"col-12\"><h2 class=\"t48 sec-title\" data-reveal>Other tests in your eye examination<\/h2><\/div><div class=\"col-12\"><p class=\"t22 sec-lead\" data-reveal>VEP and ERG are specialist tests that add to, rather than replace, the usual scans:<\/p><\/div><\/div>\t\t\t\t<ul class=\"checklist row row-cols-1 row-cols-lg-2\" data-stagger>\n\t\t\t\t<li class=\"col\"><div class=\"ck-item h-100\"><svg width=\"20\" height=\"20\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg><span><em>Corneal topography<\/em>: maps the shape of the cornea (\/en\/eye-tests-diagnostics\/corneal-topography\/)<\/span><\/div><\/li>\n\t\t\t\t<li class=\"col\"><div class=\"ck-item h-100\"><svg width=\"20\" height=\"20\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg><span><em>OCT scan (optical coherence tomography)<\/em>: cross-section scans of the retina and optic nerve (\/en\/eye-tests-diagnostics\/oct-scan\/)<\/span><\/div><\/li>\n\t\t\t\t<li class=\"col\"><div class=\"ck-item h-100\"><svg width=\"20\" height=\"20\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg><span><em>FFA (fundus fluorescein angiography)<\/em>: imaging of the blood vessels at the back of the eye (\/en\/eye-tests-diagnostics\/fluorescein-angiography\/)<\/span><\/div><\/li>\n\t\t\t\t<li class=\"col\"><div class=\"ck-item h-100\"><svg width=\"20\" height=\"20\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg><span><em>Eye ultrasound (B-scan)<\/em>: imaging when the inside of the eye cannot be seen (\/en\/eye-tests-diagnostics\/eye-ultrasound\/)<\/span><\/div><\/li>\n\t\t\t\t<li class=\"col\"><div class=\"ck-item h-100\"><svg width=\"20\" height=\"20\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg><span><em>Visual field test (perimetry)<\/em>: checks your side vision (\/en\/eye-tests-diagnostics\/visual-field-test\/)<\/span><\/div><\/li>\n\t\t\t\t<li class=\"col\"><div class=\"ck-item h-100\"><svg width=\"20\" height=\"20\" aria-hidden=\"true\"><use href=\"#i-check\"\/><\/svg><span><em>Tonometry (eye pressure measurement)<\/em>: important for glaucoma checks (\/en\/eye-tests-diagnostics\/tonometry\/)<\/span><\/div><\/li>\n\t\t\t<\/ul>\n\t\t\t<div class=\"sec-foot-flow prose\"><div class=\"links-row\" data-reveal><a class=\"link-arrow\" href=\"https:\/\/laseristanbulclinic.com\/en\/eye-tests-diagnostics\/\">All eye examinations and diagnostic tests <svg width=\"18\" height=\"18\" aria-hidden=\"true\"><use href=\"#i-arrow\"\/><\/svg><\/a><\/div><\/div>\n\t\t<\/div><\/div><\/div><\/section>\n<!-- List (Checklist cards) End -->\n\n\n<!-- FAQ (FAQ accordion) Start -->\n<section class=\"faq pad\" id=\"faq\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\"><div class=\"faq-grid\">\n\t<div class=\"faq-side\">\n\t\t\t\t<h2 class=\"t48\" data-reveal>VEP and ERG tests: frequently asked questions<\/h2>\n\t\t\t\t\t\t\t<\/div>\n\t\t<div class=\"acc\" data-stagger>\n\t\t\t\t<div class=\"acc-item is-open\"><h3><button type=\"button\" class=\"t32\" aria-expanded=\"true\" aria-controls=\"faq-f4863782-a1\" id=\"faq-f4863782-q1\">What is a VEP test eye check?<svg width=\"24\" height=\"24\" aria-hidden=\"true\"><use href=\"#i-plus\"\/><\/svg><\/button><\/h3><div class=\"acc-panel\" id=\"faq-f4863782-a1\" role=\"region\" aria-labelledby=\"faq-f4863782-q1\"><div class=\"acc-body\"><p data-reveal>A VEP (visual evoked potential) test records the electrical signal your brain produces when each eye is shown a flashing or checkerboard pattern. It shows whether the optic nerve and visual pathway are carrying the signal at a normal speed and strength. It is painless and uses small sensors on the scalp.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"acc-item\"><h3><button type=\"button\" class=\"t32\" aria-expanded=\"false\" aria-controls=\"faq-f4863782-a2\" id=\"faq-f4863782-q2\">What is an ERG test?<svg width=\"24\" height=\"24\" aria-hidden=\"true\"><use href=\"#i-plus\"\/><\/svg><\/button><\/h3><div class=\"acc-panel\" id=\"faq-f4863782-a2\" role=\"region\" aria-labelledby=\"faq-f4863782-q2\"><div class=\"acc-body\"><p data-reveal>An ERG (electroretinogram) test records the electrical response of the retina to flashes of light. It shows how well the rods and cones and the cells connected to them are working, and is used for inherited retinal disease, medicine toxicity and unexplained vision loss.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"acc-item\"><h3><button type=\"button\" class=\"t32\" aria-expanded=\"false\" aria-controls=\"faq-f4863782-a3\" id=\"faq-f4863782-q3\">What is a VEP test used to diagnose?<svg width=\"24\" height=\"24\" aria-hidden=\"true\"><use href=\"#i-plus\"\/><\/svg><\/button><\/h3><div class=\"acc-panel\" id=\"faq-f4863782-a3\" role=\"region\" aria-labelledby=\"faq-f4863782-q3\"><div class=\"acc-body\"><p data-reveal>It is used to find problems of the optic nerve and visual pathway, such as optic neuritis, compressive or toxic optic neuropathy, hereditary conditions and albinism, and to assess vision when a person cannot respond to a standard test. It supports a diagnosis; it does not make one on its own.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"acc-item\"><h3><button type=\"button\" class=\"t32\" aria-expanded=\"false\" aria-controls=\"faq-f4863782-a4\" id=\"faq-f4863782-q4\">Does a VEP test hurt?<svg width=\"24\" height=\"24\" aria-hidden=\"true\"><use href=\"#i-plus\"\/><\/svg><\/button><\/h3><div class=\"acc-panel\" id=\"faq-f4863782-a4\" role=\"region\" aria-labelledby=\"faq-f4863782-q4\"><div class=\"acc-body\"><p data-reveal>No. Scalp electrodes are attached with paste and cause no pain. You watch a screen for a series of short recordings. For an ERG, numbing drops may be used, and a thread electrode on the lower lid can feel strange but should not hurt.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"acc-item\"><h3><button type=\"button\" class=\"t32\" aria-expanded=\"false\" aria-controls=\"faq-f4863782-a5\" id=\"faq-f4863782-q5\">How long do VEP and ERG tests take?<svg width=\"24\" height=\"24\" aria-hidden=\"true\"><use href=\"#i-plus\"\/><\/svg><\/button><\/h3><div class=\"acc-panel\" id=\"faq-f4863782-a5\" role=\"region\" aria-labelledby=\"faq-f4863782-q5\"><div class=\"acc-body\"><p data-reveal>NHS leaflets say a full visual electrophysiology session takes about two hours and normally not more than two and a half, because an ERG requires 20 minutes in the dark and 10 minutes in the light before recording. A VEP alone is shorter. We will confirm the length of your appointment: <span class=\"ph\">{{VEP \/ ERG appointment length}}<\/span>.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"acc-item\"><h3><button type=\"button\" class=\"t32\" aria-expanded=\"false\" aria-controls=\"faq-f4863782-a6\" id=\"faq-f4863782-q6\">What is the VEP test normal range?<svg width=\"24\" height=\"24\" aria-hidden=\"true\"><use href=\"#i-plus\"\/><\/svg><\/button><\/h3><div class=\"acc-panel\" id=\"faq-f4863782-a6\" role=\"region\" aria-labelledby=\"faq-f4863782-q6\"><div class=\"acc-body\"><p data-reveal>There is no single universal range. The P100 wave usually appears at about 100 milliseconds, but normal limits depend on the equipment, the stimulus and your age, and ISCEV advises that each laboratory use its own reference values. Specialists also compare the two eyes with each other.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"acc-item\"><h3><button type=\"button\" class=\"t32\" aria-expanded=\"false\" aria-controls=\"faq-f4863782-a7\" id=\"faq-f4863782-q7\">What do abnormal VEP test results mean?<svg width=\"24\" height=\"24\" aria-hidden=\"true\"><use href=\"#i-plus\"\/><\/svg><\/button><\/h3><div class=\"acc-panel\" id=\"faq-f4863782-a7\" role=\"region\" aria-labelledby=\"faq-f4863782-q7\"><div class=\"acc-body\"><p data-reveal>They mean that the signal from the eye to the brain is slowed or weakened. A delayed P100 typically points to slowed conduction, such as demyelination, while a reduced amplitude suggests fewer working nerve fibres. The result must be read alongside your examination and scans; it does not name a disease by itself.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"acc-item\"><h3><button type=\"button\" class=\"t32\" aria-expanded=\"false\" aria-controls=\"faq-f4863782-a8\" id=\"faq-f4863782-q8\">What are the reasons for an abnormal VEP test?<svg width=\"24\" height=\"24\" aria-hidden=\"true\"><use href=\"#i-plus\"\/><\/svg><\/button><\/h3><div class=\"acc-panel\" id=\"faq-f4863782-a8\" role=\"region\" aria-labelledby=\"faq-f4863782-q8\"><div class=\"acc-body\"><p data-reveal>Causes include optic neuritis, multiple sclerosis, compression or injury of the nerve, poor blood supply, toxic or hereditary optic neuropathies, glaucoma, severe retinal disease and dense cataract. Technical factors such as uncorrected glasses, poor fixation or a small pupil can also change the trace, so borderline results are often repeated.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"acc-item\"><h3><button type=\"button\" class=\"t32\" aria-expanded=\"false\" aria-controls=\"faq-f4863782-a9\" id=\"faq-f4863782-q9\">Is a VEP test used for MS?<svg width=\"24\" height=\"24\" aria-hidden=\"true\"><use href=\"#i-plus\"\/><\/svg><\/button><\/h3><div class=\"acc-panel\" id=\"faq-f4863782-a9\" role=\"region\" aria-labelledby=\"faq-f4863782-q9\"><div class=\"acc-body\"><p data-reveal>Yes, as one of several tests. It can show silent optic nerve involvement even without symptoms, and the 2024 McDonald criteria allow the optic nerve to count as a fifth location when MS is diagnosed, shown by MRI, VEP and\/or OCT. The diagnosis itself is made by a neurologist using all of your results.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"acc-item\"><h3><button type=\"button\" class=\"t32\" aria-expanded=\"false\" aria-controls=\"faq-f4863782-a10\" id=\"faq-f4863782-q10\">Do I need dilating drops, and can I drive afterwards?<svg width=\"24\" height=\"24\" aria-hidden=\"true\"><use href=\"#i-plus\"\/><\/svg><\/button><\/h3><div class=\"acc-panel\" id=\"faq-f4863782-a10\" role=\"region\" aria-labelledby=\"faq-f4863782-q10\"><div class=\"acc-body\"><p data-reveal>Many ERG sessions use dilating and numbing drops, although the current ISCEV standard makes dilation optional. NHS guidance advises you not to drive for around three to five hours after dilating drops, so arrange a lift and bring sunglasses.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"acc-item\"><h3><button type=\"button\" class=\"t32\" aria-expanded=\"false\" aria-controls=\"faq-f4863782-a11\" id=\"faq-f4863782-q11\">How much does a VEP test cost?<svg width=\"24\" height=\"24\" aria-hidden=\"true\"><use href=\"#i-plus\"\/><\/svg><\/button><\/h3><div class=\"acc-panel\" id=\"faq-f4863782-a11\" role=\"region\" aria-labelledby=\"faq-f4863782-q11\"><div class=\"acc-body\"><p data-reveal>Our price for VEP and ERG testing is <span class=\"ph\">{{\u00a3 price for VEP and ERG electrophysiology testing}}<\/span>, with the specialist&#8217;s report and explanation of results included. Hotel and transfers are not included.<\/p><\/div><\/div><\/div>\n\t\t\t\t<div class=\"acc-item\"><h3><button type=\"button\" class=\"t32\" aria-expanded=\"false\" aria-controls=\"faq-f4863782-a12\" id=\"faq-f4863782-q12\">Can I send VEP or ERG results I already have?<svg width=\"24\" height=\"24\" aria-hidden=\"true\"><use href=\"#i-plus\"\/><\/svg><\/button><\/h3><div class=\"acc-panel\" id=\"faq-f4863782-a12\" role=\"region\" aria-labelledby=\"faq-f4863782-q12\"><div class=\"acc-body\"><p data-reveal>Yes. Send your reports, traces if you have them, scans and prescription for a free review. Often earlier results are enough, and we will tell you if a repeat test would add anything.<\/p><\/div><\/div><\/div>\n\t\t\t<\/div>\n\t<\/div><\/div><\/div><\/div><script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[{\"@type\":\"Question\",\"name\":\"What is a VEP test eye check?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"A VEP (visual evoked potential) test records the electrical signal your brain produces when each eye is shown a flashing or checkerboard pattern. It shows whether the optic nerve and visual pathway are carrying the signal at a normal speed and strength. It is painless and uses small sensors on the scalp.\"}},{\"@type\":\"Question\",\"name\":\"What is an ERG test?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"An ERG (electroretinogram) test records the electrical response of the retina to flashes of light. It shows how well the rods and cones and the cells connected to them are working, and is used for inherited retinal disease, medicine toxicity and unexplained vision loss.\"}},{\"@type\":\"Question\",\"name\":\"What is a VEP test used to diagnose?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"It is used to find problems of the optic nerve and visual pathway, such as optic neuritis, compressive or toxic optic neuropathy, hereditary conditions and albinism, and to assess vision when a person cannot respond to a standard test. It supports a diagnosis; it does not make one on its own.\"}},{\"@type\":\"Question\",\"name\":\"Does a VEP test hurt?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"No. Scalp electrodes are attached with paste and cause no pain. You watch a screen for a series of short recordings. For an ERG, numbing drops may be used, and a thread electrode on the lower lid can feel strange but should not hurt.\"}},{\"@type\":\"Question\",\"name\":\"How long do VEP and ERG tests take?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"NHS leaflets say a full visual electrophysiology session takes about two hours and normally not more than two and a half, because an ERG requires 20 minutes in the dark and 10 minutes in the light before recording. A VEP alone is shorter. We will confirm the length of your appointment: {{VEP \/ ERG appointment length}}.\"}},{\"@type\":\"Question\",\"name\":\"What is the VEP test normal range?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"There is no single universal range. The P100 wave usually appears at about 100 milliseconds, but normal limits depend on the equipment, the stimulus and your age, and ISCEV advises that each laboratory use its own reference values. Specialists also compare the two eyes with each other.\"}},{\"@type\":\"Question\",\"name\":\"What do abnormal VEP test results mean?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"They mean that the signal from the eye to the brain is slowed or weakened. A delayed P100 typically points to slowed conduction, such as demyelination, while a reduced amplitude suggests fewer working nerve fibres. The result must be read alongside your examination and scans; it does not name a disease by itself.\"}},{\"@type\":\"Question\",\"name\":\"What are the reasons for an abnormal VEP test?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Causes include optic neuritis, multiple sclerosis, compression or injury of the nerve, poor blood supply, toxic or hereditary optic neuropathies, glaucoma, severe retinal disease and dense cataract. Technical factors such as uncorrected glasses, poor fixation or a small pupil can also change the trace, so borderline results are often repeated.\"}},{\"@type\":\"Question\",\"name\":\"Is a VEP test used for MS?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Yes, as one of several tests. It can show silent optic nerve involvement even without symptoms, and the 2024 McDonald criteria allow the optic nerve to count as a fifth location when MS is diagnosed, shown by MRI, VEP and\/or OCT. The diagnosis itself is made by a neurologist using all of your results.\"}},{\"@type\":\"Question\",\"name\":\"Do I need dilating drops, and can I drive afterwards?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Many ERG sessions use dilating and numbing drops, although the current ISCEV standard makes dilation optional. NHS guidance advises you not to drive for around three to five hours after dilating drops, so arrange a lift and bring sunglasses.\"}},{\"@type\":\"Question\",\"name\":\"How much does a VEP test cost?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Our price for VEP and ERG testing is {{\u00a3 price for VEP and ERG electrophysiology testing}}, with the specialist's report and explanation of results included. Hotel and transfers are not included.\"}},{\"@type\":\"Question\",\"name\":\"Can I send VEP or ERG results I already have?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Yes. Send your reports, traces if you have them, scans and prescription for a free review. Often earlier results are enough, and we will tell you if a repeat test would add anything.\"}}]}<\/script><\/section>\n<!-- FAQ (FAQ accordion) End -->\n\n\n<!-- List (Sources and medical review) Start -->\n<section class=\"psec pad tight\"><div class=\"container-fluid px-0\"><div class=\"row g-0\"><div class=\"col-12\"><details class=\"sources\" data-reveal><summary class=\"t22\">Sources for the facts on this page<\/summary><ol>\n\t\t<li>ISCEV, <em>ISCEV standard for clinical visual evoked potentials (2025 update)<\/em>: three standard VEP stimuli (pattern reversal, pattern onset\/offset, flash); P100 as the most robust component; electrode placement Oz\/Fz; flash VEP for media opacity or limited cooperation; refraction needed for pattern VEP, not flash; laboratory-specific reference values. https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC12436483<\/li>\n\t\t<li>ISCEV, <em>ISCEV Standard for full-field clinical electroretinography (2022 update)<\/em>, Doc Ophthalmol 2022: minimum 20 min dark adaptation and 10 min light adaptation; DA\/LA stimuli; mydriasis optional; response origins; electrodes; paediatric testing. https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC9192408<\/li>\n\t\t<li>EyeWiki (AAO), <em>Electroretinogram<\/em>: indications (inherited retinal disorders, toxic retinopathies, unexplained vision loss); full-field, multifocal (61\u2013103 responses, central 30 degrees) and pattern ERG; electrodes; waveform origins; retinitis pigmentosa and electronegative patterns; hydroxychloroquine mfERG. https:\/\/eyewiki.org\/Electroretinogram<\/li>\n\t\t<li>EyeWiki (AAO), <em>Visual Evoked Potential\/Response (VEP\/VER)<\/em>: VEP measures the cortical signal to assess the whole visual pathway; Oz\/Fz electrodes; P100 near 100 ms; uses including infant vision, prognostication before surgery and optic neuropathy; albinism misrouting. https:\/\/eyewiki.org\/Visual_Evoked_Potential\/_Response_(VEP\/VER)<\/li>\n\t\t<li>American Academy of Ophthalmology, <em>Clinical visual electrophysiology: visual evoked potentials<\/em>: indications (optic neuropathies, albinism, amblyopia, unexplained vision loss, chiasmal anomalies); flash, pattern-reversal and onset\/offset stimuli; delayed peak times and reduced amplitude; results must be correlated clinically. https:\/\/www.aao.org\/education\/disease-review\/clinical-visual-electrophysiology-visual-evoked-po<\/li>\n\t\t<li><em>A Comprehensive Review on Methodologies Employed for Visual Evoked Potentials<\/em> (PMC4789528): P100 near 100 ms and its robustness; factors affecting VEP; P100 delay in one eye indicating optic nerve or prechiasmal dysfunction; detection of occult lesions imaging may miss. https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC4789528\/<\/li>\n\t\t<li><em>The contribution of multifocal visual evoked potentials in patients with optic neuritis and multiple sclerosis: a review<\/em> (PMC8116218): residual latency delay 12 months after optic neuritis; 20\u201340% of MS eyes without optic neuritis have subclinical involvement; 36.4% vs 0% conversion in a cohort of 46. https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC8116218<\/li>\n\t\t<li>Montalban X, et al. <em>2024 revisions of the McDonald criteria<\/em>, Lancet Neurology 2025;24(10):850\u2013865 (optic nerve as a fifth location), reported at https:\/\/practicalneurology.com\/news\/2024-mcdonald-criteria-revisions-published-in-the-lancet-neurology\/2483516\/ ; Vall d&#8217;Hebron Research Institute summary (optic nerve assessed by MRI, VEP and\/or OCT; about a quarter of MS patients present with optic neuritis): https:\/\/vhir.vallhebron.com\/en\/society\/news\/2024-revision-mcdonald-criteria-will-allow-even-earlier-diagnosis-multiple-sclerosis<\/li>\n\t<\/ol><\/details><\/div><\/div><\/div><\/section>\n<!-- List (Sources and medical review) End -->\n\n\n<!-- Call to Action (Assessment band) Start -->\n<section class=\"cta-band\" id=\"assessment\">\n\t<div class=\"contact-bg\" aria-hidden=\"true\"><span><\/span><span><\/span><span><\/span><\/div>\n\t<div class=\"cta-inner pad container-fluid\"><div class=\"row\">\n\t\t<div class=\"col-12 col-lg-7\"><div class=\"cta-copy\">\n\t\t\t\t\t\t<h2 class=\"t64\" data-reveal>Unexplained vision loss? Let a surgeon look at your results, free<\/h2>\n\t\t\t\t\t\t<p class=\"t22\" data-reveal>Upload your VEP or ERG reports, OCT scans, visual field results and prescription. Do\u00e7. Dr. \u00d6zer, Prof. Dr. Sat\u0131c\u0131 or Op. Dr. Bayram will tell you what they show and whether any further test could help, with no obligation.<\/p>\t\t\t\t\t\t<div class=\"cta-actions\" data-reveal><a class=\"pill pill-white\" href=\"https:\/\/laseristanbulclinic.com\/en\/free-consultation\/\"><span class=\"pill-dot\" aria-hidden=\"true\"><\/span><span class=\"pill-label\">Upload my reports for a free consultation<\/span><\/a><a class=\"pill pill-line\" href=\"https:\/\/wa.me\/4915783739465?text=Hello%20Laser%20Istanbul%20Clinic%2C%20I%20would%20like%20some%20information%20about%20eye%20treatment.%20Sent%20from%3A%20https%3A%2F%2Flaseristanbulclinic.com%2Fen%2F\" target=\"_blank\" rel=\"noopener\"><span class=\"pill-dot\" aria-hidden=\"true\"><\/span><span class=\"pill-label\">WhatsApp: +49 157 8373 9465<\/span><\/a><a class=\"pill pill-line\" href=\"tel:+905416390785\"><span class=\"pill-dot\" aria-hidden=\"true\"><\/span><span class=\"pill-label\">Call: +90 541 639 07 85<\/span><\/a><\/div>\n\t\t\t\t\t<\/div><\/div>\n\t\t\t\t<div class=\"col-12 col-lg-5\"><div class=\"proof-card\" data-reveal>\n\t\t\t\t\t\t<div class=\"proof-text\">\n\t\t\t\t\t\t\t\t<h3 class=\"t48\">3 eye surgeons<\/h3>\n\t\t\t\t\t\t\t\t\t\t\t\t<p class=\"t22\">Your case is reviewed by a named surgeon, not a salesperson. Reply within <span class=\"ph\">{{response time}}<\/span>.<\/p>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t<ul class=\"avatars\" aria-label=\"Our surgeons\">\n\t\t\t\t\t\t\t\t<li><img decoding=\"async\" width=\"150\" height=\"150\" src=\"https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/prof-dr-ahmet-satici-ophthalmologist-istanbul-150x150.webp\" class=\"attachment-thumbnail size-thumbnail\" alt=\"Prof. Dr. Ahmet Sat\u0131c\u0131\" loading=\"lazy\" srcset=\"https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/prof-dr-ahmet-satici-ophthalmologist-istanbul-150x150.webp 150w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/prof-dr-ahmet-satici-ophthalmologist-istanbul-300x300.webp 300w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/prof-dr-ahmet-satici-ophthalmologist-istanbul-768x768.webp 768w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/prof-dr-ahmet-satici-ophthalmologist-istanbul.webp 806w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><span class=\"tip\">Prof. Dr. Ahmet Sat\u0131c\u0131<\/span><\/li>\n\t\t\t\t\t\t\t\t<li><img decoding=\"async\" width=\"150\" height=\"150\" src=\"https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/doc-dr-muhammet-derda-ozer-cornea-specialist-istanbul-150x150.webp\" class=\"attachment-thumbnail size-thumbnail\" alt=\"Do\u00e7. Dr. Muhammet Derda \u00d6zer\" loading=\"lazy\" \/><span class=\"tip\">Do\u00e7. Dr. Muhammet Derda \u00d6zer<\/span><\/li>\n\t\t\t\t\t\t\t\t<li><img decoding=\"async\" width=\"150\" height=\"150\" src=\"https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/op-dr-aysan-bayram-eye-surgeon-istanbul-150x150.webp\" class=\"attachment-thumbnail size-thumbnail\" alt=\"Op. Dr. Aysan Bayram\" loading=\"lazy\" srcset=\"https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/op-dr-aysan-bayram-eye-surgeon-istanbul-150x150.webp 150w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/op-dr-aysan-bayram-eye-surgeon-istanbul-300x300.webp 300w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/op-dr-aysan-bayram-eye-surgeon-istanbul-768x768.webp 768w, https:\/\/laseristanbulclinic.com\/wp-content\/uploads\/2026\/10\/op-dr-aysan-bayram-eye-surgeon-istanbul.webp 806w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><span class=\"tip\">Op. Dr. Aysan Bayram<\/span><\/li>\n\t\t\t\t\t\t\t<\/ul>\n\t\t\t\t\t<\/div><\/div>\n\t\t\t<\/div><\/div>\n<\/section>\n<!-- Call to Action (Assessment band) End -->\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":0,"featured_media":0,"parent":1760,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-1882","page","type-page","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/laseristanbulclinic.com\/en\/wp-json\/wp\/v2\/pages\/1882","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/laseristanbulclinic.com\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/laseristanbulclinic.com\/en\/wp-json\/wp\/v2\/types\/page"}],"replies":[{"embeddable":true,"href":"https:\/\/laseristanbulclinic.com\/en\/wp-json\/wp\/v2\/comments?post=1882"}],"version-history":[{"count":2,"href":"https:\/\/laseristanbulclinic.com\/en\/wp-json\/wp\/v2\/pages\/1882\/revisions"}],"predecessor-version":[{"id":3027,"href":"https:\/\/laseristanbulclinic.com\/en\/wp-json\/wp\/v2\/pages\/1882\/revisions\/3027"}],"up":[{"embeddable":true,"href":"https:\/\/laseristanbulclinic.com\/en\/wp-json\/wp\/v2\/pages\/1760"}],"wp:attachment":[{"href":"https:\/\/laseristanbulclinic.com\/en\/wp-json\/wp\/v2\/media?parent=1882"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}