Anatomical and functional factors influencing the results of scleral buckling procedure for macula-off rhegmatogenous retinal detachments

Background/Aim. Rhegmatogenous retinal detachment is a potentially blinding condition of the posterior segment of the eye. Currently, the only treatment modality is surgery and surgical options include scleral buckling, pars plana vitrectomy and pneumoretinopexy. Many factors may influence the outcome of the surgery. Well defined indications are essential for achieving the best postoperative results. The aim of this study was to assess anatomical and functional outcome of treatment with scleral buckling for macula-off rhegmatogenous retinal detachments. Methods. This prospective, nonrandomized, interventional study included consecutive patients underwent scleral buckling for macula-off retinal detachment in the tertiary centre for vitreoretinal surgery. Results. A total of 168 consecutive patients (mean age 58.2 ± 13.9 years) were included in the study. Postoperatively, anatomical success was achieved in 152 (90.5%) of the patients. Parameters that influenced the anatomical success included the number of retinal breaks (p = 0.040), lens status (p = 0.041), preoperative proliferative vitreoretinopathy (p < 0.001), patients’ age (p = 0.049), and marginally, the presence of typical symptoms (p = 0.057). Duration of macular detachment, previous ocular trauma and refraction of the eye did not affect the anatomical result. Functional success was evaluated using the postoperative visual acuity and depended mainly on the duration of macular detachment prior the surgery. Visual acuity 0.4 or better was significantly more often achieved if duration of macular detachment was up to seven days (p < 0.001). Refraction and patients’ age did not influence the functional result. Conclusion. Scleral buckling is an efficient surgical procedure for treatment of patients with retinal detachment. Optimal results are achieved if operation is performed within the first seven days of duration of macular detachment.

As mentioned, precisely defined indications and excellent surgical technique are essential for successful postoperative results.There is a long tradition of RD surgery in Serbia, with the first surgical procedure performed in 1926.The most prominent vitreoretinal surgeons that were masters of those methods and teachers of nowadays Serbian ophthalmologists are Milan Blagojević, Zlatimir Kecmanović, Vasilije Misita and Miloš Ignjačev [9][10][11] .
The aim of this study was to evaluate the results of SB for the repair of rhegmatogenous macula-off RD, with the emphasis on the influence of DMD on postoperative anatomical results and visual function.

Methods
A prospective, nonrandomized, interventional study included consecutive patients hospitalized for macula-off RD between January 1, 2013 and December 31, 2013, who had SB performed at the single referral centre for vitreoretinal surgery in Serbia.The patients underwent complete ophthalmological examination including medical history, best corrected visual acuity (BCVA) assessment (measured by Snellen chart at 6 m and converted to decimal notation), applanation tonometry, slit lamp examination and indirect ophthalmoscopy with 90D and 20D lens.DMD was established for each patient, as the period between the onset of decreased vision and surgery.
Only patients with uncomplicated rhegmatogenous RD involving macula were analyzed in the study.The exclusion criteria were complicated cases of RD [multiple retinal breaks in more than two quadrants, giant tears, posterior breaks unreachable for SB or extensive proliferative vitreoretinopathy (PVR), who were operated by PPV], ocular pathology that might affect visual acuity (amblyopia, glaucoma, corneal pathology, macular diseases, previous vitreoretinal surgery), and persons in whom visual function could not be assessed (neurological or psychiatric diseases).The last two groups were operated either by SB or PPV, but were not analyzed in the study (19 and 5 cases, respectively).
SB was performed under general anesthesia, according to a standardized protocol which included localization of the retinal breaks using indirect ophthalmoscopy, transscleral cryopexy of the breaks and suturing of an encircling silicone band and silicon explant, that corresponded in size and localization to the position of the breaks, to the sclera.External drainage of subretinal fluid was not performed due to the risk of potential complications 12 .
The postoperative outcome was evaluated three months after surgery and included anatomical and functional results.Anatomical result of the surgery was classified as retina reattached to the RPE or persistent RD.The functional result was assessed using the difference in pre-and postoperative best corrected visual acuity.
The study followed the tenets of the Declaration of Helsinki, and was approved by the Ethics Committee of the Clinical Centre of Serbia.
Data were analyzed using SPSS 15.0.Comparison of categorical variables, such as DMD groups, history of eye trauma, symptoms of RD, number of retinal breaks, the presence of PVR, lens status, refraction of the eye and age groups, was carried out using χ 2 or Fisher test (as appropriate).Comparison of numerical variables, such as change in pre-and postoperative BCVA, was performed using the general linear model for repeated measures (with Bonferroni's adjustment).The level of statistical significance was 0.05.

Results
The study involved a total of 168 patients who underwent SB for macula-off RD and fulfilled other inclusion criteria.Demographic and clinical findings of patients are presented in Table 1.
According to the anatomical outcome, the majority of the patients (90.5%) had retinal reattachment achieved, while 9.5% patients had persistent RD (Table 1).Comparative analysis of their characteristics (  patients with a single retinal break (p = 0.040), without PVR (p < 0.001), with a transparent lens (p = 0.041) and in those 50-65 years old (p = 0.049).The outcome in the patients presenting typical symptoms (flashes of light, floaters and visual field defects) was better but this difference was only close to statistically significant (p = 0.057).On the other hand, parameters including DMD, the history of ocular trauma and refraction of the eye did not affect the anatomical result of SB (p > 0.05).
Among 152 of the patients who achieved retinal reattachment, we further investigated functional outcome.
The change in the BCVA between admission and 90 days post-SB was used as a parameter of functional recovery.Overall, a significant increase in visual acuity was observed (p < 0.001) (Table 1).The patients with shorter DMD (≤ 10 days) had significantly better both preoperative and post-SB BCVA compared to those with DMD 11-30 days (p = 0.001) or > 30 days (p < 0.001) (Table 3).On the other hand, there was no difference in post-SB BCVA between patients with DMD 11-30 and > 30 days.The DMD group 1 was further divided into subgroups with DMD 1-4, 5-  8-10 days (comprising 7, 12 and 18 patients respectively), among which no difference in post-SB BCVA was observed (Table 3), presumably due to a small number of patients and consequential lack of statistical power.As the BCVA was quite similar in DMD subgroups 1-4 and 5-7 days, they were aggregated and compared to the 8-10 days DMD subgroup, and significantly higher both preoperative and post-SB visual acuities were observed in the 1-7 days subgroup (Table 3).Therefore, patients from DMD subgroup 8-10 days were added to those in DMD 11-30 days group, and BCVA was analyzed in the transformed groups (1-7, 8-30 and > 30 days).The patients with the shortest DMD had a significantly better visual recovery (p < 0.001) (Table 3).
The functional results of SB were the same in patients with different refractive errors (p > 0.05).Emmetropic (including one hyperopic patient) and myopic patients alike achieved significantly better post-SB BCVA (p < 0.001).The patients below 50 years of age had better preoperative BCVA when compared to those older than 65 years (p = 0.047).Postoperative BCVA, although better than the initial one in all age groups, did not differ significantly.

Discussion
SB is a conventional surgical procedure for the repair of uncomplicated RD.The rate of anatomical success in the presented series was 90.5%.This is comparable to 94% and 88.5% the data of bicenter studies by Pastor et al. 13 , and Falkner-Radler et al. 14 respectively, and even better 80.4% than the large multicenter MUSTARD study 1 .
The anatomical success rate did not depend on DMD, ocular trauma and refraction of the eye, but depended on the number of retinal breaks, the presence of PVR, lens status and patients' age and marginally on the presence of typical symptoms.These results, with small differences, confirm previous findings 7, [15][16][17][18][19] .We did not find any difference in anatomical success in the groups of patients with different refractive errors.Interestingly, the MUSTARD study reported better anatomical results in moderate myopes (-2.75 to -8 dioptres, 86.7%) 18 .The presence of a single retinal break when compared to multiple breaks, was associated with better anatomical result, confirming that multiple breaks increase the risk for failure of SB 8,16,19 .It is more likely to overlook a retinal break or fail to seal them all, in cases with multiple breaks.Early PVR was a significant predisposing factor for unfavourable anatomical outcome 7,17 .PVR restricts the retina and SB cannot prevent this process.In cases with extensive proliferative vitreoretinopathy, PPV should be performed.
An association of anatomical success with the presence of typical symptoms may be expected since those patients were operated earlier and had a lower chance of developing retinal changes including PVR.Indeed, significantly better anatomical results in the presence of typical symptoms (82% and 77% respectively, p = 0.014), were shown in the MUS-TARD study 1 .We achieved anatomical success in 96.5% of the patients with typical symptoms vs 87.4% of those who did not present symptoms.However, this difference was only marginally significant.
Patients with a transparent lens had a significantly higher rate of retinal reattachment than those with cataract or previous cataract surgery.The presence of cataract in phakic or capsule opacities in pseudophakic eyes can reduce visualisation of peripheral retina and make the detection of retinal breaks more difficult.Therefore, those patients can have poorer surgical outcomes, as shown by Vukosavljević et al. 20 .However, Thelen et al. 1 reported equal success in patients with a natural lens, aphakia and pseudophakia (80.49%, 79.18% and 81.95% respectively), but the results could not be compared since their study did not analyze patients with natural lens according to its transparency.
The best anatomical results were achieved in patients of 50-65 years of age.In contrast, in the study of Hassan et al. 21o significant difference was observed in the rate of retinal reattachment in different age groups (≤ 60, 61-75 and > 75 years of age).Thelen et al. 1 reported that the best anatomical results were achieved in the younger age group (21-30 years; 87.79%) and poorest in children up to 10 years (77%) and very old patients (71-80 and 81-90 years; 74.07%and 70.48% respectively).The great diversity of reported results warrants further investigations.
In patients with anatomical success, functional results were analysed.Many preoperative factors including visual acuity 6,7,19,22 , DMD 6,8,19,21 , height of RD 22 , vitreomacular traction 12 , as well as postoperative factors including epireti-nal membranes 23 and persistent submacular fluid [22][23][24] can influence visual recovery.Functional results mainly depend on the time lapse between the separation of neurosensory retina from the RPE in the macular area and surgical repair.In our series, the best functional recovery was achieved if SB was performed within the first 7 days after the symptoms occured.After that period postoperative BCVA decreased significantly.Postoperative visual acuity was significantly higher than preoperative BCVA in all patients irrespective of DMD, except for the patients with 1-4 days of DMD.In this group, improvement in visual acuity did not reach statistical significance due to good initial BCVA.Postoperative visual acuity was equally good within the period of 1-7 days of DMD and the majority of these patients (72%) achieved visual acuity of 0.4 or better (mean BCVA 0.52).Previous studies reported shorter, equal or longer DMDs as critical for the satisfactory postoperative results, including 3 25 , 6 8 , 7 3,7,15 and 10 days 21 .In a series of 96 patients, Liu et al. 15 reported a BCVA ≥ 0.4 achieved in 68% of patients with DMD of 1-7 days (mean BCVA 0.45) and concluded that postoperative BCVA was the same within this period.On the other hand, Hassan et al. 21analyzed 94 patients with maculaoff RD and concluded that DMD of 1-10 days was a significant period for satisfactory functional results (when compared to DMD groups 11 days to 6 weeks and > 6 weeks).In our study, the patients with DMD 1-10 days had overall better visual recovery, but when stratified into subgroups of 1-7 and 8-10 days, a significantly better postoperative BCVA was observed in favor of DMD 1-7 days.Diederen et al. 8 reported similar findings, concluding that the critical DMD was 6 days.
Refraction of the eye did not affect the postoperative BCVA and in all groups significant improvement was achieved.However, Yang et al. 26 reported that low grade myopic patients (up to -6 D) regained significantly better postoperative visual acuity as compared to both high grade myopic (> -6 D) and emmetropic patients.
Functional outcome of SB did not differ among the age groups, although it was slightly better in younger patients due to the best preoperative BCVA.The fact that functional results are better in younger patients has been shown in studies of Pastor et al. 13 and Hassan et al. 21.

Conclusion
SB is an efficient surgical procedure for uncomplicated macula-off rhegmatogenous RD cases with a single retinal break, transparent lens and without PVR.The presented results show that equally good postoperative results are achieved if operation is performed at any time within the first seven days of DMD, whereas after this period functional recovery significantly decreases.

Table 2 )
showed that significantly better anatomical results were achieved in Vol.74, No. 3