We appreciate the interest of Shah and colleagues in our recent article. They have made some excellent suggestions regarding our study and its application in clinical practice. They point out, as we did in our original study, that contact ultrasonic methods to determine axial lengths may give erroneous axial measurements due to deformation of the globe by the probe. They also comment that we did not analyze the data in relation to intraocular pressure (IOP). However, in Figure 2 of our article, we showed that among eyes with preoperative IOP below 8 mm Hg, the most myopic refractive surprise occurred in eyes that had the largest increases in postoperative IOP. If the myopic surprise were due to erroneous axial length measurement by contact ultrasound alone, the myopic surprise should occur in all eyes with low IOP, regardless of the postoperative change in IOP. Furthermore, In a response to another letter to the editor, we reported a new analysis of our data that showed that of the 39 cases in which the preoperative IOP was 8 mm Hg or lower, the correlation between IOP changes and extent of refractive surprise was statistically significant (r = −0.47, r 2 = 0.22, P = 0.003).
We wholeheartedly agree with Shah and colleagues’ recommendation to use newer noncontact techniques for axial length measurements. Indeed, we are now using these newer devices in our own practices. We are also in support of the suggestion to measure the axial length prior to trabeculectomy surgery in anticipation of subsequent cataract development. However, we caution that changes in axial lengths may be unpredictable, and some eyes may not regain their original axial length after cataract surgery. Although using the original axial length may reduce the likelihood of a myopic surprise, if the axial length remains less than the original measurement, the result would be a hyperopic surprise, which may be more intolerable to the patient.