{"id":1831,"date":"2026-10-20T08:52:25","date_gmt":"2026-10-20T08:52:25","guid":{"rendered":"https:\/\/laseristanbulclinic.com\/eye-glossary\/intraocular-pressure\/"},"modified":"2026-10-20T12:56:54","modified_gmt":"2026-10-20T12:56:54","slug":"intraocular-pressure","status":"publish","type":"page","link":"https:\/\/laseristanbulclinic.com\/en\/eye-glossary\/intraocular-pressure\/","title":{"rendered":"Intraocular Pressure (IOP): What It Is, Normal Range and High Eye Pressure"},"content":{"rendered":"\n
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  1. Home<\/a><\/li>
  2. Knowledge centre<\/a><\/li>
  3. Eye glossary A\u2013Z<\/a><\/li>
  4. Intraocular Pressure (IOP): What It Is, Normal Range and High Eye Pressure<\/span><\/li><\/ol><\/div>\t\t\t

    Intraocular Pressure (IOP): What It Is, Normal Range and High Eye Pressure<\/h1>\n\t\t\t\t\t\t

    Medically reviewed by {{surgeon}}<\/span><\/strong>, {{surgeon’s title and specialty}}<\/span>, on {{review date}}<\/span>. Last updated {{date}}<\/span>.<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

    \"Illustration<\/figure><\/div>\n\t\t\t<\/div><\/div>\n<\/section>\n\n\n\n\n
    \n\t\t<\/svg>Definition<\/span>\n\t\t\t

    Intraocular pressure (IOP)<\/strong> (noun, abbreviated IOP; also called eye pressure)<\/em>: the pressure of the fluid inside the eye, measured in millimetres of mercury (mmHg). A normal intraocular pressure is roughly 10 to 21 mmHg and changes through the day. Pressure that is too high for your optic nerve can damage the nerve and lead to glaucoma, which is why glaucoma care at Laser Istanbul Clinic, led by Prof. Dr. Ahmet Sat\u0131c\u0131, centres on lowering it.<\/p>\n\t\t<\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

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    Intraocular pressure: key facts<\/h2><\/div>\n\t\t\t\t\t<\/div>\n\t\t\t
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    <\/svg>What it is<\/span><\/dt>
    The fluid pressure inside the eye, which keeps the eye in shape<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Unit<\/span><\/dt>
    Millimetres of mercury (mmHg)<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Normal range<\/span><\/dt>
    About 10 to 21 mmHg (some sources give 10 to 20); it varies through the day and from person to person<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>What makes it<\/span><\/dt>
    A clear fluid, the aqueous humour, made just behind the iris and drained where the iris meets the cornea<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>High IOP without nerve damage<\/span><\/dt>
    Called ocular hypertension; the optic nerve looks normal and vision is not affected<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Link with glaucoma<\/span><\/dt>
    Pressure is the risk factor that treatment can change, but glaucoma also occurs at normal pressure<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Symptoms<\/span><\/dt>
    Usually none; a sudden, very high pressure (angle-closure attack) causes severe pain and is an emergency<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Measured by<\/span><\/dt>
    Tonometry: a quick test, usually by air puff or a gentle touch after numbing drops<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Specialist<\/span><\/dt>
    Ophthalmologist; at Laser Istanbul Clinic, glaucoma is treated by Prof. Dr. Ahmet Sat\u0131c\u0131<\/dd><\/dl><\/div>\n\t\t\t<\/div>\n\t\t<\/div><\/div><\/div><\/section>\n\n\n\n\n
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    \"Illustration<\/div><\/div>\n\t\t
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    What is intraocular pressure?<\/h2>\n\t\t\t\t\t\t\t\t

    Intraocular pressure is the pressure of the fluid inside your eye. The front part of the eye, between the iris (the coloured part) and the cornea, is filled with a clear fluid called the aqueous humour. The American Academy of Ophthalmology (AAO) explains that this fluid is made just behind the iris, circulates through the front of the eye and then drains out where the iris meets the cornea. As long as the fluid is made and drained in balance, the pressure stays steady and the eye keeps its shape.<\/p>\n

    You can think of it like a tap and a drain. If the drain works well, the pressure stays in its normal range. If the drain is partly blocked, fluid builds up and the pressure rises. The NHS describes glaucoma in the same way: it usually results from fluid building up in the eye because it cannot drain properly, which can damage the optic nerve that connects the eye to the brain.<\/p>\n

    Eye pressure is not the same thing as blood pressure. Having diabetes or high blood pressure is, however, listed among the risk factors for raised eye pressure.<\/p><\/div>\n\t\t\t\t\t\t\t\t\t\t\t<\/div>\n<\/div><\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

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    What is a normal eye pressure?<\/h2>\n\t\t\t

    A normal eye pressure is about 10 to 21 mmHg, according to the AAO. Another AAO page rounds this to 10 to 20 mmHg, so you will see both figures. The number changes during the day, which is why a single reading is only a snapshot.<\/p>\n\t\t\t

    The important point is that “normal” is not exactly the same for everyone. The US National Eye Institute (NEI) notes that normal eye pressure varies by person, so what is normal for one person could be high for another. Some people with pressure above the usual range never develop glaucoma, and some people develop glaucoma with pressure inside the usual range.<\/p>

    Eye pressure situation<\/th>What it means<\/th>What usually happens<\/th><\/tr><\/thead>
    About 10 to 21 mmHg, healthy optic nerve<\/th>Within the usual range<\/td>Routine checks<\/td><\/tr>
    Higher than normal, healthy optic nerve and normal vision<\/th>Ocular hypertension (a “glaucoma suspect”)<\/td>Monitoring, sometimes eye drops<\/td><\/tr>
    Higher than normal, optic nerve damage and loss of side vision<\/th>Glaucoma with raised pressure<\/td>Treatment to lower the pressure<\/td><\/tr>
    Within the usual range, optic nerve damage and loss of side vision<\/th>Normal-tension glaucoma<\/td>Treatment to lower the pressure further<\/td><\/tr><\/tbody><\/table><\/div><\/div>\t<\/div><\/div><\/div><\/section>\n\n\n\n\n
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    What causes high intraocular pressure?<\/h2><\/div>

    High intraocular pressure is usually the result of fluid that does not drain well enough through the eye’s drainage angle. The AAO lists these risk factors for ocular hypertension:<\/p><\/div><\/div>