We are grateful for the comments from Pahuja and associates on our article regarding long-term changes in corneal astigmatism with aging after sutureless cataract surgery. Although their comments seem to be theoretically appropriate, some important facts have been overlooked.
In our study, mean corneal astigmatism in the surgery group was greater than that in the nonsurgery group. Only eyes that underwent horizontal incision were included, and horizontal incisions are known to induce mainly with-the-rule changes in corneal astigmatism. Therefore, a horizontal incision usually increases the amount of corneal astigmatism in eyes that have with-the-rule or oblique corneal astigmatism, whereas it decreases the amount of corneal astigmatism in eyes with against-the-rule astigmatism. In addition, most cataract incisions have a torque effect on the cornea. In the current study, approximately 70% of eyes had with-the-rule or oblique corneal astigmatism, and 30% of eyes had against-the-rule astigmatism at the time of cataract surgery. Accordingly, it is reasonable that the mean corneal astigmatism in the surgery group was greater than that in the nonsurgery group throughout the follow-up, because the difference continues for a long time.
Visual acuity is related not only to the amount of corneal astigmatism, but rather is related to multiple factors. For example, the occurrence of posterior capsule opacification and the development of other ocular diseases impair visual acuity over time in eyes that undergo cataract surgery, whereas the progression of cataracts and other diseases decreases visual acuity in eyes that do not underwent surgery. The influence of these pathologic features may be more pronounced than that of the change in the corneal astigmatism. Indeed, in the present study, uncorrected and corrected distance visual acuity in the nonsurgery group were significantly worse than those in the surgery group, predominantly because of the presence of a slight cataract. Accordingly, the effect of changes in corneal astigmatism on visual acuity in relation to aging should be assessed using other analytical methods. We currently are examining corneal astigmatism and visual acuity in each decade of life. This ongoing study may provide useful information regarding the amount of corneal astigmatism that should be retained in middle-aged and younger patients.