In cataract surgery, the natural lens of the eye, which is clouded by the cataract, is emulsified and removed. It is then replaced with a refractive lens implant. The strength (called power) of the implant is calculated by measuring the length of the eye and the steepness of the cornea. The instruments that are used to make these calculations have been created to calculate based on “virgin eyes”—eyes that have never had any surgery. LASIK and PRK, however, alter the steepness of the cornea, which means that the calculations tend to be less accurate for implants if a patient has had either of these surgeries in the past. Whereas I can achieve about 90 to 95% accuracy with an eye that has never had LASIK or PRK, the accuracy decreases to about 60-70% in an eye that has had previous LASIK or PRK. Luckily, new mathematical calculations are constantly being developed for calculating the power of a patient’s lens implant. This is especially true now that so many people who have had LASIK surgery will be getting older and developing cataracts.
I have the most modern equipment for performing the preoperative measurements including Lenstar Optical Biometry, Oculus Pentacam, Tomey Topographer, and Zeiss Cirrus HD Optical Coherence Tomography (OCT). Furthermore, I use the Alcon ORA during all post LASIK and post PRK cataract surgeries in order to get real time information to confirm or change the previously decided upon lens implant power. The good news, of course, is that even if the implant power is off a bit, an additional LASIK or PRK procedure can be done afterward to make corrections. PRK is the procedure that’s usually recommended as lifting the flap after so long a time puts the patient at too great a risk for epithelial ingrowth.
Please note that the cataract surgery itself is exactly the same whether or not the patient has had previous LASIK or PRK. The only difference is the accuracy of the results are not quite as good. Of course, cataract surgery is primarily about getting rid of the cloudy lens problem. With all of the modern equipment however, we can fortunately do our best to nail the precise outcome desired.