We read with great interest the prospective study by Wong and associates regarding biometric stability after scleral buckling (SB) surgery. The authors reported that SB surgery resulted in significantly longer axial length (AL) (26.09 ± 1.46 mm vs 26.51 ± 1.96 mm; P = .01) at 12 months after surgery compared with preoperative values. In other words, a mean increase in AL of 0.58 mm (0.32-0.83, P < .001) and a mean myopic shift of 1.04 diopters (0.03-2.05 diopters, P = .04) were reported, and these findings are consistent with other reports. However, 47.1% of eyes (8/17 eyes) had a macular detachment at baseline, and we believe it would be better to exclude patients with preoperative macular detachment in such a biometric study.
Because patients with macula-off retinal detachment have a poor fixation and shortened distance between the corneal vertex and foveal vitreoretinal interface, their inclusion to the present study is problematic. In their study of 145 consecutive patients who had combined phacoemulsification and retinal detachment repair, Jeoung and associates reported that several factors can induce an error in the preoperative determination of the true axial length, such as poor fixation, retinal detachment, and posterior staphyloma. Similarly, a recent prospective biometric study assessed the accuracy of axial length measurements in 100 macula-off retinal detachment cases, using different methods. The authors reported a postoperative IOLMaster mean AL that was significantly longer than the IOLMaster preoperative mean by 0.79 mm ( P = .048). Thus, this AL variation could be secondary to the reapplication of the macular detachment alone and we must be careful about the reliability of preoperative measurement in case of macular detachment. It would be interesting to extract data by excluding cases with retinal detachment involving the macula.
Furthermore, Wong and associates reported a series of cases with high AL at baseline (mean 26.09 ± 1.46 mm), whereas the difficulty of getting reliable measurements for patients with high myopia or high AL is widely reported. As Jeoung and associates reported in their case series, myopic shifts could be developed in patients with long axial lengths, poor preoperative visual acuity, and preoperative foveal detachment. According to this study, patients with preoperative foveal detachment had a significant postoperative myopic shift ( P = .024 and P = .002). To reduce bias, it would be wise to conduct a subgroup analysis.
Moreover, for eyes with high myopia or retinal detachment, we can be helped by ultrasound biometric measuring. Thus, the axial length could be manually adjusted to the anterior choroidoscleral band and the axial length can also be corrected in case of decentration induced by myopic staphyloma.
Finally, the surgical technique reported by the authors consisted of a MIRA 360-degree scleral buckling, which would likely result in greater biometric changes than a localized solid silicon segmented scleral buckle. In the future it would also be interesting to compare biometric changes between the different surgical procedures.