Trifocal lens surgery is a lens replacement operation. Your surgeon removes the eye's natural lens through a tiny incision and places a clear trifocal intraocular lens (IOL) in the same position. The operation is identical whether it is done for a cataract or, in a clear lens, to reduce your need for glasses (refractive lens exchange, or RLE). The Royal College of Ophthalmologists (RCOphth) says the only difference is the reason for surgery.
How the lens focuses at three distances. A trifocal IOL has fine diffractive rings on its surface that split incoming light into three focus points. In the US Food and Drug Administration (FDA) approval document for the AcrySof IQ PanOptix, the rings sit in the central 4.5 mm of the optic and add +2.17 dioptres for intermediate and +3.25 dioptres for near vision. According to the American Academy of Ophthalmology's EyeWiki, this places the focus points at about 40 cm (reading), 60 cm (computer and arm's length) and distance, with roughly a quarter of the light sent to near, a quarter to intermediate and half to distance.
Trifocal and multifocal: the same family. "Multifocal lens" is the umbrella term for any IOL with more than one point of focus. Older bifocal multifocal lenses had two points, near and far. Trifocal lenses add a third for intermediate vision, and some newer multifocal designs, such as TECNIS Synergy, blend multifocal and extended-depth-of-focus optics to give a continuous range instead of three separate points.
Why there is a trade-off. Splitting light gives clear vision at several distances, but the brain also receives slightly out-of-focus images. At night, these show up as rings (halos) or rays (starbursts) around lights. Most people adapt over the first months as the brain learns to ignore them, a process called neuroadaptation.
Technology we use: {{trifocal / multifocal lens models actually offered, e.g. PanOptix / PanOptix Toric, TECNIS Synergy / Synergy Toric II}}, implanted in a fully equipped, Ministry of Health–licensed operating theatre in Istanbul. Before surgery, your examination includes optical biometry to calculate the lens power, corneal topography to measure astigmatism, and an OCT scan of the macula and optic nerve.