Abstract
Abstract: :
Purpose: Conductive keratoplasty (CK) steepens the cornea centrally. This study is the first to look at elevation changes of the cornea over time, as well as the optical zone size change over time. Methods: Sixty–five patients who had CK were screened to enter the study, and 25 were excluded due to missing data or prior surgery. All patients had BCVA of 20/20 or better. Treatments ranged from 8 to 24 spots. Orbscan topography was performed pre–operatively as well as postoperatively at 1 week, 1 month and 2 month visits. Data collected included central anterior elevation (AE) as well as the highest point on the anterior elevation map (AEH), posterior elevation (PE) as well as the highest point on the posterior elevation map (PEH), spherical equivalent and optical zone size. Results: Eighteen right eyes and 22 left eyes were entered into the study. Mean age of patients was 53 years (+/– 3.9 years). Thirteen patients had retreats (32.5%). Mean spherical equivalent pre–operatively was +0.58 diopters (S.D.+0.54). When comparing the highest point in the anterior elevation over time (AEH), there was a large mean increase (0.029 mm) in elevation at 1 week (p<0.01), which decreased slightly at 1 month by a mean of 0.003 mm (p=0.005) and then stabilizes at the 2 month visit, with no statistically significant difference compared to the 1 month values. Similar results are seen in the AE group. Interestingly, when groups are split into 8, 16 and 24 spots of treatment in the AEH group, values showed a statistically significant increase in height in the 16 and 24 spot groups, yet in the 8 spot group, the mean post–operative elevation was not statistically different compared to pre–op values. Similar results are seen with the AE group. Results for the PE and PEH groups will be presented. Spherical equivalent changed by a mean of – 1.7 D at 1 week, with no statistically significant change from 1 week to 1 month. However, there was a decrease in the myopic change from 1 month to 2 months follow–up. Again the 8 spot group had no statistically significant change in spherical equivalent when comparing pre–operative and post–operative refraction. Effective optical zone size increased in size from 1 week to 1 month (p=0.003), and slightly again from 1 month to 2 months (p=0.05). Conclusions: In CK, corneal elevation increases at the 1 week post–operative visit, and stabilizes or decreases slightly thereafter. This is only true for the 16 and 24 spot treatment groups. Eight spot treatments did not show a statistically significant change in elevation after treatment which may suggest a less effective treatment pattern. Loss of elevation over time correlated with regression and the need for retreatment.
Keywords: refractive surgery • refractive surgery: other technologies • refractive surgery: corneal topography