We would like thank Martiano and associates for their letter and interest in our study. As they rightly pointed out, axial length (AL) measurements with optical biometry in cases of macular detachment are prone to error from a shortened distance between the corneal apex and the vitreoretinal interface, poor foveal fixation, and problems with AL measurements in long eyes. We assessed the effects of these possible systematic errors on our findings. AL measurements between study eyes and fellow eyes were compared to ascertain accuracy. There were no significant differences in AL measurements between study and fellow eyes in either the macula-on (26.46 ± 1.41 mm vs 26.36 ± 1.44 mm) or the macula-off groups (25.12 ± 1.65 mm vs 24.95 ± 1.18 mm, P = .59). In a subgroup analysis of eyes without macula detachment, AL was still significantly longer at month 12 compared with preoperatively (27.25 ± 1.28 mm vs 26.62 ± 1.36 mm, P = .006). The mean difference was 0.63 mm (95% confidence interval 0.26 to 1.00, P = .006). A mean myopic shift of 2.17 diopters was seen in this subgroup, but the difference was not statistically significant ( P = .08), likely owing to the small sample size.

Despite the inherent problems of optical biometry, our main findings have not been significantly biased. This could be attributed to the following reasons: First, eyes with macular detachment in our study had relatively good preoperative visual acuity (VA) and, therefore, good foveal fixation. Only 3 eyes with macula detachment had VA of 6/60 or worse. Second, the height of foveal detachment, as measured on spectral-domain optical coherence tomography (Spectralis HRA-OCT; Heidelberg Engineering, Heidelberg, Germany) ranged from 21 μm to 439 μm and only 3 eyes had foveal detachment of >300 μm; thus any potential underestimation of AL would have been minimal.

To avoid measurement errors with optical biometry in cases of macula-off retinal detachment, accuracy of measurements should be ascertained by comparison with the known refraction and AL of the fellow eye. Further, Rahman and associates showed that accurate measurements may still be obtained with optical biometry by manually selecting the posterior signal peak instead of the default anterior peak for AL measurement. In patients with poor foveal fixation, we agree with Martiano and associates that ultrasound biometry may be more accurate for AL measurement than optical biometry.

Finally, we agree that a comparison of surgical techniques, as suggested by Martiano and associates, would provide greater clarity toward our goal of reducing biometric changes from scleral buckle surgery.

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Jan 5, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Reply

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