AMERICAN JOURNAL OF OPHTHALMOLOGY
Extreme Corneal Flattening After Radial Keratotomy Richard E. Damiano, M.D., and S. Lance Forstot, M.D. Corneal Consultants of Colorado, P.c. Inquiries to Richard E. Damiano, M.D., Corneal Consultants of Colorado, P.e., 8381 South Park Ln., Littleton,
CO 80120. Progressive flattening of the cornea after radial keratotomy has been well documented.' The final extent of this flattening has not been determined." In our corneal and refractive referral practice, we have seen patients who have continued postoperatively to have corneal flattening, approximately 1.0 diopter per year for up to ten years. This flattening results in Humphrey automated keratometry readings below 30.0 diopters in one primary meridian. A 45-year-old woman underwent bilateral eight-incision radial keratotomies elsewhere in 1984. Preoperative, cycloplegic, manifest refraction was R.E.: -5.75 + 1.00 x 85 degrees and L.E.: -6.00 + 0.50 x 65 degrees. Preoperative keratome try readings were R.E.: 41.00/ 42.37 x 86 degrees and L.E.: 41.25/42.37 x 80 degrees. Eight-incision radial keratotomies with an optical zone of 3.5 mm without re-deepening were performed with a diamond knife in 1984. One year postoperatively, the patient's visual acuity without correction was R.E.: 20/20 and L.E.: 20/25 +1. Keratometry readings were R.E.: 37.00/38.75 x 85 degrees and L.E.: 36.25/35.87 x 113 degrees. The cycloplegic, manifest refraction was R.E.: - 0.50 + 0.50 x 90 degrees and L.E.: +0.25 + 0.75 x 165 degrees. During the next seven years, the corneas gradually flattened and, on April 24, 1989, keratometry readings were R.E.: 35.25/36.25 x 68 degrees and L.E.: 33.87/29.00 x 91 degrees. Cycloplegic, manifest refraction was R.E.: +2.50 + 0.50 x 155 degrees and L.E.: +5.25 + 2.25 x 167 degrees. Uncorrected visual acuity was R.E.: 20/30 and L.E.: 20/100. Corrected visual acuity was 20/20 in both eyes. A 43-year-old man had an initial, cycloplegic, manifest refraction of R.E.: -9.75 + 0.75 x 105 degrees with 20/30 visual acuity and L.E.: -10.25 + 0.50 x 75 degrees with 20/30 visual acuity. Keratometry readings were R.E.: 43.00/ 43.87 and L.E.: 43.37/44.37.
In 1980, one of us (R.E.D.) performed bilateral 16-incision radial keratotomies with 3-mm optical zones and peripheral re-deepenings by using a diamond blade. One year postoperatively, visual acuity without correction was R.E.: 20/60 +1 and L.E.: 20/40 +1. Keratometry readings were R.E.: 34.87/31.25 x 103 degrees and L.E.: 34.37/ 30.12 x 87 degrees. A manifest refraction was R.E.: +0.50 + 2.25 x 5 degrees and L.E.: plano +1.25 x 154 degrees. Ten years postoperatively, keratometry readings were 32.75/29.25 x 123 degrees and L.E.: 32.25/27.75 x 97 degrees. Cycloplegic, manifest refraction was R.E.: +4.00 + 6.00 x 15 degrees and L.E.: +4.50 + 4.00 x 155 degrees. Visual acuity in each eye without correction was 20/200 and, with correction, 20/30. It appears that after eight- and 16-incision radial keratotomies for severe myopia, corneas may continue to flatten dramatically over the ensuing years. Using the Humphrey automated keratometer, it is possible to document this excessive flattening. These measurements are obviously well beyond the range of the conventional Haag-Streit and Bausch & Lomb keratometers. The readings taken with the automated keratometer are not exactly comparable to the readings taken with conventional keratometers using additional lenses. However, in conjunction with the documented progression of the hyperopia, it is clear that in these two cases, progression of the corneal flattening reached levels not previously documented."
References 1. Dietz, M. R., Sanders, D. R., and Raanan, M. G.: Progressive hyperopia in radial keratotomy. Long-term follow-up of diamond knife and metal blade series. Ophthalmology 93:1284,1986. 2. Waring, G. 0., Lynn, M. J., Fielding, B., Asbell, P. A., Balyeat, H. D., Cohen, E. A., Culbertson, W., Doughman, D. J., Pecko, P., McDonald, M. B., and the PERK Study Group: Results of the prospective evaluation of radial keratotomy (PERK) study four years after surgery for myopia. JAMA 263:1083,
3. Barraquer, J.: Radial keratotomy. Refractive surgery. In Jaffe, N. (ed.): Atlas of Ophthalmic Surgery, Chap. 7. Philadelphia, J. B. Lippincott, 1990, p. 7.6.