The present cross-sectional study showed that, compared to unoperated fellow eyes, scleral buckling for RRD induced an axial length increase of 0.83 mm with a mean myopic shift of 1.35 diopters. We also found a concomitant decrease in anterior chamber depth, while anterior corneal astigmatism was not significantly altered. Preoperative axial length was independently correlated with axial length increase after surgery. We found that for every 1-mm increase in baseline axial length, there was a mean axial length increase of 0.15 mm after surgery.
In the literature, there are only few reports that using optical biometry, addressed the issue of ocular biometric changes after scleral buckling for RRD [6–8], and there is only one study with a follow-up duration longer than 1 year. Herein, we report the results of ocular biometric changes after a mean of 51 months from surgery. Our data showed that axial length changes after SB are substantially stable even in the very long term. Indeed, the reported short-term AXL increase in previous studies range from 0.58 to 1.31 mm. These differences in AXL changes among studies are probably related to differences in the surgical technique as well as in the baseline characteristics of patients. For instance, all previous studies included a different percentage of macula-off detachment. Although optical biometry accuracy is not theoretically affected by retinal elevation, significant underestimation of AXL measurements was however observed in RRD eyes with macular involvement. [10–12] To address this potential bias in the present study only macula-on RRD were selected.
Lee et al. in a recent retrospective investigation comparing, as in our study, AXL change between operated and fellow eyes, found an axial length increase of 1.31 mm after a mean follow-up of 26 months that did not significantly differ between myopic and highly myopic eyes. On the contrary, our results showed that AXL change after surgery is strongly associated with preoperative AXL. However, in the study by Lee et al. it was not specified whether their evaluations were carried out in macula-on or macula off patients. In addition, no details were given regarding further surgical treatment performed in their cohort after RRD repair. These issues may have biased their results.
In contrast to our results, Wong et al, in a previous 12-month prospective study, found a significant association between AXL increase after surgery and the extent of segmental buckling. Of note, in their study, 9 out of 17 patients (53%) received more than 4 clock hours segmental buckling compared to 12% only (2 out of 17 patients) of our series. Therefore, this apparent discrepancy may be attributed to differences in the surgical procedure, that is the use of more extensive segmental buckling in Wong’s cohort.
Goezinne et al., in a prospective study, found transient ACD decrease after SB that returned to normal levels at 1 year after surgery. In contrast, in our series we observed that, especially when comparing operated with fellow eyes, AC shallowing after SB persists in the long term, up to 51 months after surgery. Our results are somehow in line with two previous studies that reported significant post-SB ACD decrease up to 12 months after surgery. [7, 8]
ACD decrease after scleral encircling has been attributed to the anterior rotation of ciliary body associated with surgically induced ciliary congestion and subsequent forward shift of the iris-lens diaphragm. Another potential mechanism should be the low IOP prior to surgery that may induce a transient deepening of AC.
In agreement with previous reports, that described transient corneal astigmatism increase up to 3 months after SB, we did not find any significant long-term postoperative change of anterior corneal astigmatism.[8, 14, 15] After a mean follow-up of 51 months we observed a mean increase of anterior corneal astigmatism of approximately 0.25 diopters from baseline.
The strengths of this work are the long follow-up, the comparison with fellow eye as well as the application of strict inclusion and exclusion criteria. Indeed, only eyes with macula-on RRD were selected and any further surgery before and after the SB procedure either in the operated or the fellow eye was an exclusion criterion. All SB surgeries were performed by the same experienced retinal surgeon using a standardized technique that involved a fixed 10-mm shortening of the encircling band and the use of the same buckle type in all cases. The shortcomings are the retrospective design and the small sample size.