Effects of depth of incision on final outcome in radial keratotomy

To assess the effect of depth of incision on the final outcome of radial keratotomy for correction of myopia.

Sixty-five eyes with preoperative uncorrected myopia between 2.5-6.0D in subjects with a mean age of 29.2 (+/-7) years underwent radial keratotomy between Sept 1999-July 2002 in department of Ophthalmology, Military Hospital, Rawalpindi. Based on their preoperative depth of incision the eyes were divided into group-A (twenty-five eyes), with an incision depth of 500-530 microm, and Group-B (forty eyes), with an incision depth of 531-560 microm. The comparison between the postoperative visual acuity of two groups was made at the end of study after one years' follow up.

A total of Sixteen eyes in Group-A (64%) that were within one diopter of emmetropia at first follow-up reverted back to their preoperative myopic state after one year of surgery as compared to only two eyes (5%) in Group-B (p<0.05). Hyperopic shift occurred in two eyes (8%) in Group-A, as compared to four eyes (10%) of Group-B (p>0.05). After one year, refraction showed that only 24% cases of Group-A were within 1 diopter of emmetropia as compared to 85% cases in Group-B. Similarly, 40% cases of Group-A were within 2 diopters of emmetropia as compared to 90% cases of Group-B. Glare and variation of vision in the initial four weeks were the most frequently reported complications in both groups.

Depth of corneal incision significantly affects the outcome of surgery, if central optical zone is kept the same in cases of low to moderate degrees of myopia.