The effect of elective phacofragmentation on central corneal thickness in the dog.

OBJECTIVE To characterize the short- and intermediate-term effects of elective phacofragmentation on central corneal thickness (CCT) in the dog. METHODS Forty-three dogs (66 eyes) undergoing elective phacofragmentation cataract surgery over an 8-month period at a single private ophthalmology referral clinic were enrolled in the study. Central corneal thickness was measured by ultrasonic pachymetry just prior to surgery, 1 day following surgery, 1 week postoperatively, 1 month postoperatively, and more than 2 months postoperatively. Statistical comparisons were made using descriptive and inferential statistical methods with a level of significance set at P < 0.05. RESULTS The initial mean CCT of 611 microm increased dramatically to 741 microm 1 day postphacofragmentation. Mean CCT remained slightly elevated (666 microm) at 1 week postoperatively, but became indistinguishable from preoperative measurements by 1 month postsurgery (626 microm) and remained so at the > 2-month time period (618 microm). The change over time and trends remained statistically significant and remarkably similar, even when adjusted separately for age, gender, surgeon status, diabetic status, cataract type, and total surgery time (all P < 0.0001). Corneas of diabetic dogs were thicker than those of nondiabetic dogs at all time periods, and the overall effect of diabetic status was significant (P = 0.016). There was a sharper increase from the preoperative to 1-day postoperative CCT in the diabetic group compared to the nondiabetic group. The mean CCT of the pseudophakic group took longer to return to baseline than the aphakic group. The mean CCT of the foldable intraocular lens (IOL) group took longer to return to baseline than both the rigid IOL and aphakic groups. Dogs with documented in-hospital postoperative intraocular pressure spikes (> 25 mmHg) developed a greater 1-day postsurgical increase in CCT. It appears that there was a sharper decrease in mean CCT from 1 month to more than 2 months postoperatively in the postoperative hypertension group. CONCLUSIONS Elective phacofragmentation cataract surgery results in an increase in CCT in dogs, but this increase is transient. Particular care may be indicated to protect the endothelium of diabetic patients undergoing phacofragmentation. These data do not clearly support an advantage of the small-incision cataract surgery made possible by the use of foldable IOLs.