Circumferential block resection to reduce myopia.
BACKGROUND
The surgical treatment of excessive myopia following penetrating keratoplasty has been largely ignored. Oversized corneal grafts can induce myopia and the Troutman wedge (block) resection has been used to correct astigmatism by removing tissue in a single corneal semimeridian. This study explores the use of block resections in opposing semimeridians to reduce myopia caused by a steep cornea.


METHODS
Six eyes received three different operations. One eye received 60-degree block resections in semimeridians located 90 degrees (procedure 1), two eyes received 0.5-millimeter semicircumferential (180 degrees) block resections (procedure 2), and three eyes underwent 0.5-millimeter 360-degree circumferential block resections (procedure 3). All patients were followed for at least 1 year.


RESULTS
Procedure 1 (two 60-degree block resections) developed approximately 2.75 D of myopic correction at 1 year. The average reduction of spherical equivalent was 4.50 D for procedure 2 (one 180-degree block resection) and 10.50 D for procedure 3 (one 360-degree block resection) at 1 year. Although all eyes regained best spectacle-corrected visual acuity, the postoperative course was prolonged by irregular astigmatism.


CONCLUSIONS
Circumferential and semicircumferential block resections can reduce myopia after penetrating keratoplasty and in naturally-occurring myopia, but the postoperative course can be prolonged, especially because of irregular astigmatism. Early removal of sutures results in regression of myopic correction.
Department of Surgery, University of Nevada, Reno.
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Buzard
D000328:Adult; D001251:Astigmatism / Q000209:etiology; D005139:Eyeglasses; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000601:surgery; D015948:Keratoplasty, Penetrating / Q000009:adverse effects; D008297:Male; D008722:Methods; D009216:Myopia / Q000209:etiology / Q000517:prevention & control* / Q000601:surgery; D012086:Reoperation; D013536:Suture Techniques; D014792:Visual Acuity