What is cataract? Cataract is an opacification of the eye’s lens. This lens is located inside the eye behind the pupil. The lens sits inside a lens bag. Cataract causes blurred vision by blocking light as it travels through the eye. It can also change the focal point of the eye, further blurring the vision.
How is cataract treated? The only proven treatment for cataract is surgery. Through micro-wounds in the cornea, a circular opening is made in the lens bag and the lens is emulsified with ultrasound and then aspirated out of the eye with a probe. With the natural lens (and thus the cataract) now removed, a folded artificial lens (intra-ocular lens: IOL) is inserted into the lens bag where it then unfolds to take a stable position. The focusing power of each lens implant is specific to each eye and highly precise measurements are taken of the eye before surgery to determine the exact lens for your eye.
Will I need glasses after cataract surgery? This depends on several factors, the main one being the type of lens implant inserted.
Option 1: The traditional approach has been to insert lens implants with a single focal point (monofocal IOL). This is usually set for distance though can be set for near. This usually results in excellent vision for the chosen focal point (distance or near) but spectacles are required to see objects at other distances.
Option 2: A second option to minimise spectacle dependence is with “monovision.” In monovision, a lens implant in one eye is inserted which focuses vision for distance and, in the other eye, a lens implant is inserted which focuses distance for near. With both eyes open, one is able to see clearly for distance and near. Before this is undertaken, a trial with contact lenses is required to ensure that the brain will be able to adapt to a different point of focus in each eye.
Option 3: Multifocal lens implants or extended depth of focus implants. In recent years there has been an dramatic improvement in designs of multifocal intraocular lenses. These lens implants work by splitting the light that travels through the eye into different focal points. The result is that one is able to see for distance, intermediate distance (for example the distance to a computer screen) and near.
Extended depth of focus IOL’s work by having a greater focal range and thus provides for distance and intermediate vision. With extended depth of focus IOLs, spectacles are often required for fine near vision.
So why aren’t multifocal IOl’s used in everyone? Multifocal IOL’s have some potential downsides which are unique to these lenses which don’t occur as commonly in monofocal IOL’s. The first is that there is usually a period of “neuro-adaptation” in which the brain needs to adjust to these lenses. The second is that glare and haloes are more commonly experienced by patients (need numbers here) than in monofocal lenses. The third is that because these lenses split light, the quality of distance vision, particularly in low contrast conditions (eg night driving) can be not as sharp as with a monofocal IOL. Very rarely these lenses need to be removed if they cannot be tolerated, which involves further surgery and its associated risk.
Which lens implant is right for me? This is a very individual decision and depends on several factors. The first is your visual requirements. If having excellent distance vision is your main priority and are happy to wear spectacles for near work then having monofocal lens implants is an excellent option. If you require excellent distance and intermediate vision, then an extended depth of focus lens implant is an excellent option, though spectacles are likely to be required for fine near work. If you are seeking very good vision for all distances without spectacles then a multifocal lens implant is the option most likely to achieve this.
What are the risks of cataract surgery? As with all surgery there is risk. Overall, cataract surgery is extremely safe though the following can occur.
Loss of vision
Endophthalmitis
The most feared complication of cataract surgery is Endophthalmitis. Endophthalmitis is a serious infection of the eye that can, in the most severe case, result in complete loss of vision or loss of the eye. The rates of endophthalmitis range from 0.023% to 0.17% (1/600 to 1/4300) in various published series worldwide (.
2)Retinal detachment
The retina is the inner lining of the eyeball which detects light (similar to a film in a camera). Following cataract surgery, there is the risk that this layer can detach from its normal position (retinal detachment). If this occurs, a further operation is required to repair this. The risk of retinal detachment is 0.6 – 0.9% (1/110 – 1/160) (article: retinal detachment after cataract surgery). After retinal detachment surgery, 80% of eyes have vision of 6/12 or better (vision which would meet the legal driving standards if this were one’s only eye) (anatomic and visual outcomes of 23-G vitrectomy without scleral buckling for primary RRD).
3)Sympathetic Ophthalmia.