Cataract Surgery (Intra-Ocular) Lens Options

Dr Ben Wild

Overview

For vision to be in clear and in focus, light must pass through the cornea, the clear tissue at the front of the eye, the pupil, the black hole in the center of the colored iris, and the lens, the clear tissue inside the eye, to the tissue responsible for detecting light, the retina. The lens sits inside a bag (capsule) attached to strings (zonules) that are controlled by muscles (ciliary body).

The eye on the left, shows a clear lens. The eye on the right shows a nuclear sclerotic cataract.

Cataracts refer to the fogging/clouding of the natural lens. Cataract surgery, usually, involves dilating the pupils, creating two small incisions in the cornea, creating a hole in the front of the capsule (capsulorhexis), separating the rest of the capsule from the lens inside (hydrodissection), cutting the lens into small fragments (phacoemulsification), vacuuming up the fragments, and inserting a new synthetic lens into the capsule. Usually the corneal incisions are small enough that stitches are not required. This process often takes under 10 minutes and the patient is sedated but still awake.

The most difficult part, before surgery, is choosing the type of lens that gets inserted into the eye. There are many options!

Single Vision

Single vision lenses, simply put, correct vision for one focal distance. Most people choose either to be fully corrected for distance vision (the patient will need computer/reading glasses) or to be corrected for near (the patient will need glasses for distance). Single vision lenses can be spherical or aspherical. Aspheric lenses produce better optics and cause less light and colour distortions. Single vision lenses can also be spherical or toric. Toric lenses correct a patient's astigmatism. If a patient had astigmatism and asked for a spherical lens, they would need glasses for distance and near (to correct the astigmatism)

Single Vision Distance

This option can correct nearsightedness, farsightedness and astigmatism so that the patient can see well far away, potentially without glasses. The patient will need glasses to see the computer and to read.

Single Vision Near

This option can correct nearsightedness, farsightedness and astigmatism so that the patient can see well up close without glasses. This means the patient could potentially use a computer (positioned fairly close) and read (pushing the book a little further away) without any glasses and would need correction, such as glasses or contact lenses, to see far away.

Single Vision Monovision

This option can correct nearsightedness, farsightedness and astigmatism so that the patient can see well at distance in one eye, often the dominant eye, and see well up close with the other. This does negatively affect depth perception and leads to glare at night (coming from the nearsighted eye), but works well in people who do not want glasses most of the time. Often, these patients benefit from night-time driving glasses to reduce the glare and reading glasses for dimly lit environments like reading a menu at a restaurant.

Multifocal

Multifocal lenses, simply put, correct more than one focal distance. This does not necessarily mean every focal distance, as explained by the options below. Multifocal lenses require two fully functioning eyes to work well. This means, if a patient has amblyopia, experienced decreased vision after trauma, or has conditions like glaucoma, macular degeneration, diabetes, and more, they are unlikely to be good candidates. Some ophthalmologists would consider extended depth of focus lenses in these cases but some would not.

Trifocal Lenses

This option can correct nearsightedness, farsightedness and astigmatism so that the patient can see well far away, intermediate distances, and up close. These lenses work by having concentric rings in the lens, with each ring being a different prescription for either distance, intermediate or near. Because these lenses have many rings, there is a considerable amount of light scatter which causes glare. Some patients are 100% free of glasses, whereas, most patients require a very small prescription for near. This is a great option for people who don't mind sacrificing glare and optical clarity at all distances in order to not wear glasses.

Extended Depth of Focus Lenses

This option can be further broken down into 1) distance and mid range vision such as a TV, 2) distance and intermediate such as a computer, and distance and almost near vision such as the dash in a car. These lenses are built without most of the rings you see on a trifocal lens. This means, there is considerably less light scatter and glare.

Option 1 has minimal glare but has the shallowest depth of focus.

Option 2 has a small amount of glare but can provide someone with decent distance and desktop computer vision.

Option 3 also has a small amount of glare but can correct distance, computer, and a little bit of near vision.

Patients, in all 3 cases, would still require reading glasses, but, to varying degrees. This is a great strategy for people who want to be free of glasses for 90% of the day yet not sacrifice much vision compared to single vision lenses. All 3 options can correct nearsightedness, farsightedness and astigmatism.