Opposite Clear Corneal Incisions
Reply: We are well aware that astigmatism can be corrected by arcuate keratotomy (AK). In fact, one of us (Dahan) has 14 years of experience with these incisions, having learned them from Umberto Merlin,1 one of the pioneers of AK. Dahan has abandoned AK for opposite clear corneal incisions (OCCIs) because of their superior efficacy and reliability. Arcuate keratotomies are similar to radial keratotomies (RKs) in many respects. They often create unstable wounds that may not heal. When they heal too well, their astigmatic effect vanishes. The results of RK and AK are inconsistent and may vary over the years.2 Dr. Nichamin states that “a ‘grooved’ or corneal-perpendicular incision, for a given arc length, is more effective at flattening the meridian in which it is placed.” Does he mean that a 3.2 mm AK (less than 30 degrees of arc) is more effective than 3.2 mm OCCIs? Definitely not. A 3.2 mm AK will not correct 2.0 diopters (D) of astigmatism, but 3.2 mm OCCIs will; 4.2 mm OCCIs will correct more than 3.0 D of astigmatism, where a 4.2 mm AK will hardly correct 2.0 D.
Opposite clear corneal incisions are based on the fact that a penetrating corneal wound creates astigmatism that becomes permanent once the healing period has passed. This is the primary advantage of OCCIs over AK. We have extended our indications for OCCIs and are applying them to all forms of astigmatism: congenital astigmatism, postcataract surgery astigmatism, post-penetrating trauma astigmatism and, finally, postkeratoplasty astigmatism. Opposite clear corneal incisions are a powerful and reliable method of correcting astigmatism, and our report is just the beginning of a series of articles on this new method. Obviously, the penetrating nature of OCCIs raises the question of their safety, and we strongly recommend suturing any OCCIs longer than 3.2 mm. The sutures can be removed within a week or two, according to the surgeon's clinical judgment. In high-risk cases, we even recommend suturing 3.2 mm OCCIs. The quest for a first-day postoperative result is superfluous when the safety and efficacy of astigmatic correction are at stake. With further longitudinal studies, the present controversy will be elucidated.
Elie Dahan MD
Jeffrey Lever FRCS
1. Merlin U. Curved keratotometry procedure for congenital astigmatism. J Refract Surg 1987; 3:92-97
© 2001 by Lippincott Williams & Wilkins, Inc.
2. Waring GO III, Lynn MJ, Nizam A, et al. Results of the Prospective Evaluation of Radial Keratotometry (PERK) study five years after surgery. Ophthalmology 1991; 98:1164-1176