POST-RADIAL KERATOTOMY
Though once thought to be a safe and effective form of refractive surgery, radial keratotomy (RK) is now known to cause a long list of undesirable side effects that doctors and patients must work hard to overcome. The procedure was popular in the 1980’s and 90’s, but has since fallen out of favor.
RK sought to improve visual acuity by making incisions aimed at flattening the central cornea while steepening the periphery. Although many patients could more accurately read an eye chart following surgery, the procedure induced corneal changes that, in many cases, created more problems than it solved.
RK CHALLENGES
RK was approved for use in the United States to improve patients’ visual acuity. Indeed, most patients had positive visual outcomes that they enjoyed for many years. Unfortunately, long-term complications were not adequately studied prior to the approval of RK, and it was not until many years later that researchers discovered that the post-surgical cornea often continues to flatten with age creating far-sightedness, and is structurally compromised leading to visual fluctuations. Post-RK corneal ectasia can also develop into iatrogenic keratoconus, which can further impair vision.
RK also induces anisometropia, corneal scarring and irregular astigmatism, with patients frequently reporting glare, halos and fluctuating vision. To overcome these and other challenges, glasses, contact lenses or another surgical procedure is often required.
VISION CORRECTION OPTIONS AFTER RK
There is no one-size-fits-all solution for post-RK vision correction. If a patient struggles with early-stage ectasia only, glasses or soft contact lenses may suffice for visual correction. However, the type of corneal disfigurement that is caused by RK—namely irregular astigmatism—often cannot be managed with either of these entry-level options. There is also a question of safety when using soft lenses after RK. One study found that this modality may increase the risk for neovascularization.
Since RK causes the cornea to change in shape from prolate to oblate, it usually necessitates the use of a special type of contact lens—namely, a corneal gas permeable (GP) lenses or a scleral lens. Standard-diameter corneal GP lenses offer crisp vision that is stable throughout the day, making these lenses preferable in many cases compared to soft lens designs. However, some wearers struggle with discomfort when wearing standard GP lenses. In addition, RK incisions can create depressions and elevations on the cornea that make many corneal GP designs hard to fit. In these cases, a hybrid lens or a scleral lens may be a better choice.
A next-generation GP lens, called a scleral lens, offers the benefits of a GP design along with a number of other benefits that can address the unique concerns of people who have had RK. For instance, because scleral lenses don’t touch the cornea or the limbus, depressions and elevations at the incision sites no longer factor into vision or comfort. For this and other reasons, scleral lenses are growing in popularity. A scleral lens is a type of GP lens featuring a large-diameter that allows the lens edge to rest on the white part of the eye, known as the sclera. Unlike traditional, small diameter GP lenses that rest on the highly innervated and sensitive cornea, the scleral lens vaults over the cornea and is much more comfortable than its smaller diameter counterpart. Another feature that adds to comfort with a scleral lens is the liquid buffer that exists between the back of the lens and the front of the eye. Liquid fills this space and can help protect corneal tissue and create a smooth refractive surface. In this way, scleral lenses are often thought to offer the best of all possible worlds for patients who face challenges following RK procedures.
If you’ve had RK and struggle with corneal health issues, discomfort, or disappointing vision, contact our team at ACLI to schedule a consult and determine the most appropriate management strategy for you!
REFERENCES
Sawelson H, Marks RG.; Five-year results of radial keratotomy.Refract Corneal Surg. 1989 JanFeb;5(1):820.
Arrowsmith PN, Marks RG.; Visual, refractive, and keratometric results of radial keratotomy. Five-year follow-up. Arch Ophthalmol. 1989 Apr;107(4):50611.
Randleman JB, Woodward M, Lynn M, et al. Risk assessment for ectasia after corneal refractive surgery. Ophthalmol. 2008;115:37-50.
Waring GO 3rd, Lynn MJ, Culbertson W, Laibson PR, Lindstrom RD, McDonald MB, Myers WD, Obstbaum SA, Rowsey JJ, Schanzlin DJ.; Three-year results of the Prospective Evaluation of Radial Keratotomy (PERK) Study.Ophthalmology. 1987 Oct;94(10):133954.
McDonnell PJ, Nizam A, Lynn MJ, Waring GO., 3rd; Morning-to-evening change in refraction, corneal curvature, and visual acuity 11 years after radial keratotomy in the prospective evaluation of radial keratotomy study. The PERK Study Group. Ophthalmology. 1996 Feb;103(2):233–239.
Shivitz IA, Russell BM, Arrowsmith PN, Marks RG; Optical correction of postoperative radial keratotomy patients with contact lenses. CLAO J. 1986;12(1): 59-62.
Alio ́ JL, Belda JI, Artola A, et al.; Contact lens fitting to correct irregular astigmatism after corneal refractive surgery. J Cataract Refract Surg 2002; 28:1750–1757.
van der Worp E, Bornman D, Ferreira DL, Faria-Ribeiro M, Garcia-Porta N, Gonzalez-Meijome JM; Modern scleral contact lenses: A review. Cont Lens Anterior Eye. 2014 Aug;37(4):24050. doi: 10.1016/j.clae.2014.02.002. Epub 2014 Mar 12.