Having cataract surgery when you have had previous Radial Keratotomy (RK) surgery offers some challenges. The traditional formulas used to calculate the new lens power are inaccurate. Special attention to using the correct equipment to measure the cornea such as Pentacam and ATLAS topographers and using adjusted formulas are necessary to get the best result after cataract surgery.
Radial Keratotomy (RK) was a popular refractive procedure to correct myopia between 1973 and 1994. It was developed by the Russian ophthalmologist Svyatoslav Frodorov. He removed glass from the cornea of a boy who fell off his bike and broke his glasses. He made radial incisions to remove the glass fragments and when it had healed he discovered the boys short sightedness had also greatly improved.
Radial Keratotomy (RK) surgery involved the radial incisions at 90% depth into the cornea. Incisions were either 4, 8, 12, 16 or 32 in number. The cornea heals with fibroblasts and collagen and causes an overall flattening of the central cornea which gives the improvement in vision for myopia (short-sightedness). In New Zealand this type of eye surgery was only done in Auckland and Hastings.
Some side effects were observed which include scattering of light at night giving a flare of starburst effect on lights. A progressive hyperopia (long-sightedness) can occur and patients eventually develop cataracts.
Although Radial Keratotomy surgery was effective at treating myopia it has now been replaced by laser eye surgery techniques using excimer lasers to reshape the cornea. These techniques are much more accurate and have less complications and side effects than RK.
Having cataract surgery when you have had previous RK surgery offers some challenges. The traditional formulas used to calculate the new lens power are inaccurate. The usual equipment used to measure the cornea curvature are also inaccurate. Special attention to using the correct equipment to measure the cornea such as Pentacam and ATLAS topographers and using adjusted formulas are necessary to get the best result after cataract surgery.
During cataract surgery the main incision needs to be placed between the old RK incisions and if this is not possible then changing to a scleral tunnel technique is required. Attention to keeping the eye pressure low during the procedure is also very important. This can be achieved with using a low bottle height with low flow and a small phaco tip.
Following cataract surgery the cornea can remain swollen for a longer period than normal. This can cause a transient hyperopia (long sightedness) for up to 3 months. Prescribing new glasses after cataract surgery therefore should wait until 3 months after surgery.
Sometimes despite getting good measurements and adjusting with the correct lens formula the target vision after cataract surgery is outside what is expected. Normally this would still be corrected with glasses or contact lenses. It may be possible in some of these cases to consider a Lens exchange or a piggy back lens to reduce this effect.
When planning for second eye surgery the eye measurements need to be repeated prior to planning surgery.
If you have had RK surgery and now have cataracts contact Bowen Eye Clinic on 0800 69 2020 for an assessment and discussion on how your vision can be improved.