Mild myopic regression after refractive surgery is not rare and is occasionally due to a small lens opacity. A cataract should be suspected in an eye that develops any significant myopic shift some time after refractive surgery, particularly if the patient is over 40 years of age and especially if the refractive surgery was many years prior.

All patients complaining of decreased vision after refractive surgery should undergo a dilated posterior segment examination. At the same time, the lens needs to be carefully evaluated. The oil-drop cataract may easily be
overlooked. Both the oil-drop cataract and the PSC are often best seen in retro-illumination. Small nuclear cataracts can also be seen by placing a fine slit beam through the center of the lens. Retinoscopy may also highlight an oil-drop cataract.

If a visually significant cataract is identified and the patient feels functionally impaired, cataract surgery should be considered. A few important issues need to be emphasized in the setting of the post-keratorefractive patient. One is the concept of accommodation. Patients who have become accustomed to excellent uncorrected distance and near vision must be educated about the impact of cataract surgery on accommodation. It is possible that lens-induced myopia has helped to preserve uncorrected near function. Patients who retain reasonable accommodation need to understand that it will disappear after standard cataract surgery. Potential solutions should be discussed, for example, monovision, accommodating and multifocal intraocular lenses (IOLs).

The second issue to discuss is the impact of refractive surgery-induced higher order aberrations and decreased contrast sensitivity on the IOL choice. Since multifocal IOLs also decrease contrast sensitivity, their use after keratorefractive surgery is controversial. The potential benefit of continued spectacle independence must be tempered by the risk of decreasing the quality of vision after cataract surgery. The pros and cons of multifocal IOLs need to be discussed with patients and thoroughly understood before proceeding.^2,3

The third issue involves the possibility of surprise astigmatism appearing postoperatively. Corneal refractive surgery is based on refraction and not on corneal astigmatism. This means that the refractive surgery may have corrected lenticular astigmatism even in the absence of corneal astigmatism. Refractive astigmatism should be anticipated to return in this situation following cataract extraction because of the original astigmatism correction that now resides in the cornea. This astigmatism can be anticipated if the cataract surgeon reviews the pre-LASIK medical record just prior to the initial surgery. Specifically compare the refractive astigmatism to the corneal astigmatism as measured by keratometry or corneal topography. The difference is lenticular astigmatism, which will disappear after cataract surgery. This potential problem can be resolved by inserting a toric IOL or by performing limbal relaxing incisions at the time of cataract surgery in order to correct regular corneal astigmatism. See Chapter 10 for additional information and (See Video 10). Residual astigmatism can also be managed postoperatively using limbal relaxing incisions, surface ablation, or LASIK.

The fourth challenge in managing the post-refractive surgery cataract is the fact that IOL power calculations are less accurate after keratorefractive surgery than in unoperated eyes.⁴ This is because our current methods of measuring the corneal power are not as accurate after corneal refractive surgery. Standard biometry performed on a myopic LASIK patient will underestimate the IOL power and if used, would result in postoperative hyperopia and an unhappy patient. Alternative strategies are necessary for predicting proper IOL power (see below). Patients need to understand the inherent difficulty in predicting IOL power after keratorefractive surgery and that they may need further correction postoperatively to achieve their best visual function. In addition to glasses or contact lenses, they may need to consider either more refractive surgery, such as surface ablation or LASIK, or lens-based surgery, such as a piggyback lens implant or an IOL exchange in order to achieve better uncorrected vision.^5,6

A wide variety of methods have been developed to improve the accuracy of IOL calculations after refractive surgery; however, none of them is perfect. When preoperative information, such as manifest refraction and keratometry readings prior to LASIK surgery, and a stable refraction several months after the refractive surgery are available, then the “clinical history method” can be used.