topography topics

Refractive Surgery Complications: Central Islands

BY KENNETH A. LEBOW, OD, FAAO
August 2000

Central islands are a commonly encountered post-operative complication of laser refractive surgery procedures and represent an abnormal ablation pattern. Topographically, a central island is defined as an area of central or paracentral corneal steepening at least 1 diopter to 3 diopters with a diameter of 1mm to 3mm, which is measured at least one month post-operatively and is usually associated with clinical symptoms such as monocular diplopia, ghosting of images or qualitative visual changes.

While several theories have been postulated regarding the formation of central islands, central islands generally resolve with time and often do not require additional treatment. However, during their resolution, the patient may be visually compromised.

Central Island Formation

Patient LZ underwent an uncomplicated PRK procedure in his right eye to correct 6.00D of myopia. One month after surgery, uncorrected visual acuity was 20/40, which could be corrected to 20/20 with -1.25D sphere with complaints of glare and poor vision.

Figure 1 demonstrates a central island formation approximately 3mm in diameter with a magnitude of 2.2 diopters. (The central curvature was 42.30 diopters and the apex of the central island measured 44.50 diopters ­ plus sign.) Although the patient wanted an immediate resolution, over the period of 21 months his vision returned to normal levels with a flattening of the central island.

Central Island Resolution

Figure 2 demonstrates a comparison between the average flat curvatures of the eye and the apex of the central island. Over time, not only does the appearance of the central island dissipate, but it also reduces from 3.0 diopters to 1.7 diopters. This reduction of the apex reduced the patient's visual complaints and enabled him to function remarkably well.

Figure 1. Central island formation about 3mm in diameter with 2.2 diopters of magnitude.	Figure 2. Comparison of the average flat curvatures and central island apex.

 Dr. Lebow is a member of the AOA and a Fellow of the AAO. He is in private practice in Virginia Beach, Virg.