Cataract Surgeon

Monofocal intraocular lenses offer the highest quality vision but are limited to a particular focal length. Therefore, patients set for clearer unaided distance vision would require glasses for reading and computer tasks.

Monovision describes the situation where one eye is set for distance vision and the other for reading vision. There is only so much difference in focal length between the eyes that the brain will tolerate. Therefore, monovision is preferred in patients who already have a prescription where one eye sees more clearly in the distance and the other eye sees more clearly for reading tasks. Otherwise, it is recommended to have a contact lens trial simulating monovision before committing to this arrangement in cataract surgery.

Multifocal intraocular lenses have more than one focal length to reduce dependence on glasses. Trifocal intraocular lenses aim to offer clear unaided vision for reading, computer and distance vision. Extended depth of focus lenses aim to offer clear distance and computer vision but glasses are still required for reading tasks. Multifocal lenses have to split the light between different focal lengths and so although there is less dependence on glasses, there is lower quality of vision with more haloes and glare. These symptoms are most prominent with trifocal intraocular lenses but also occur to a lesser degree with extended depth of focus intraocular lenses. These unwanted visual phenomena can be particularly troubling when driving at night. Trifocal lenses are not recommended in patients with macular disease.

Toric intraocular lenses are designed to reduce the amount of astigmatism in the visual system. Astigmatism decreases the quality of vision. Patients with significant astigmatism are offered toric intraocular lenses. These toric intraocular lenses are precisely aligned during cataract surgery to reduce the amount of astigmatism. Either monofocal or multifocal lenses can be designed to have a toric component to reduce astigmatism.