Extraocular Muscle Imbalance and Outcomes of Scleral Buckling Surgery for Primary Rhegmatogenous Retinal Detachment

Objective: The objective was to study the muscle imbalance, restrictive motility in unlike gazes and the outcomes of the scleral buckling surgery for rhegmatogenous retinal detachment. Study design: Prospective follow-up study Settings and duration: The study was conducted at Al-Shifa Trust Eye Hospital Rawalpindi from Aug 2015 to Jan 2016. Methodology: The patients were checked prior to surgery and two follow up visits were done afterwards. Thorough history was taken along with full orthoptic assessment and ocular motility in all four main gazes including elevation, depression, adduction and abduction. Vision, type and position of explants, site of detachment, and risk factors of detachment were also observed. Results: A total of 48 eyes of 46 patients were taken. Mean age of the study participants was 37.16±20.37 years. Horizontal, vertical and combined deviations were observed in study population. Exo deviation was most common deviation among patients. Most reported risk factors of retinal detachment included trauma, pseudophakia, aphakia and myopia. Motility limitations of all four gazes was observed and it was found out that after buckling the squint and restriction is been increased up till two months. Conclusion: Ocular restriction among the patients was observed over a period of 2 months and it depicted that encircling with sclera buckling elicited an increase in restrictive ocular motility from pre-operative to 1 week and 2 months after surgery.

North America and Europe have more frequent appearance of detachments in contrast to India and Africa. It is a state which can result in total loss of vision if left untreated. Retinal detachment is a major reason for low acuity in wealthy countries while in developing countries due to scarcity of resources its treatment is not well looked upon. (4) The main reason for late treatment is that, it presents at a very later stage therefore projection of the problem is variable in accordance with its appearance and presentation. (2) The treatments used for retinal detachment are pars plana vitrectomy pneumatic retinopexy and conventional scleral buckling surgery. Scleral clasping comprises of setting a scleral clasp or adaptable band a bit of silicone wipe, elastic, or semi-hard plastic) around the equator of the eye to adjust any force that is being put upon the retina along these lines. This whole process relieves the traction on retina. An exterior entry point is made in the sclera and choroid to drain the sub-retinal liquid, if necessary. (4) Scleral buckling for major rhegmatogenous detachment can end in severe consequences that include an increase in pressure, muscle imbalance, diplopia and post-operative restricted motility. (1) It is of utmost importance to take into consideration the form and degree of changes that are brought about by retinal surgery in Outpatient Department (OPD) of Retina Clinic undergoing scleral buckling. It is also important to put a figure on the side effects and muscle limitation. Another most crucial subject is to quantify the success rate of post-operative attachments and to raise proficient professional awareness. The present study addressed the presence and quantification of muscles imbalance before and after retinal surgery along with restrictive motility in different gazes. The key outcome of this study was

Significance:
Scleral buckling for major rhegmatogenous detachment can end in severe consequences that include an increase in pressure, muscle imbalance, diplopia and post-operative restricted motility. The present study addressed presence and quantification of muscles imbalance before and after retinal surgery along with restrictive motility in different gazes. The key outcome of this study was amount of imbalance, type of deviation, macular status and restrictions in different gazes.

Outcomes of Scleral Buckling
amount of imbalance, type of deviation, macular status and restrictions in different gazes.

Methodology
A prospective follow up study was conducted at Retina Clinic of Al-Shifa Trust Eye Hospital Rawalpindi. Data for the study was collected from August 2015 to January 2016. A total of 48 eyes of 46 patients were included in the study through nonprobability convenient sampling. Patients included in the study presented retinal detachment and were advised scleral buckling surgery during the study duration. Patients were informed about the procedure and the follow up visits. A verbal informed consent was taken from each patient. Silicon was used as a material for buckling surgery in all cases. All patients were programmed to be examined pre-operatively and after 1 week and 2 months post-surgery. Anatomical reattachment of retina at 1-week postoperation follow-up visit was considered as the main outcome variable for the surgery. Detailed history including family history, history of trauma, history of strabismus when presented for surgery, eye status and previous history of surgery were included in pre-designed questionnaire. Visual acuity of RD eye and normal eye of each patient was measured by Snellen acuity chart at six meters. Muscle imbalance was checked by cover test. Imbalance was measured as heterotopias or heterophoria. Muscle restriction was measured in four major gazes; "elevation, depression, adduction and abduction". Restriction was labeled from 0 "normal motility" to -4.0 "fully restricted". Details of all patients were routinely recorded for the abovementioned variables. Data analysis was done using SPSS version 17.0. Frequencies and percentages of categorical variables were reported, a Chi-square test was applied to find out the association between ocular motility of groups divided on basis of age while repeated measures ANOVA test was applied for comparison between preoperative and post-operative data. P-value < 0.05 was taken as significant.

Results
A total of 48 eyes of 46 patients were included in the study. Mean age of the study participants was 37.16±20.37 years (ranging from 15-90 years). Out of the 46 patients 34 (75%) were males while 12 (25%) were females. Eye status of patients was variable with 25 males and 10 females having Phakic eyes, 10 males and 2 females had Pseudophatic eyes and only 1 male was Aphakic.
Patients were asked about ocular history. Out of the 46 patients, 10.4% had a positive ocular family history, 29.2% had a positive history of ocular surgery, 50% had a positive history for Strabismus while 39% of the patients had history of trauma that resulted in retinal detachment. Location of retinal detachment was also taken into consideration; figure 1 shows the location of detached retina in all cases that were included in the study.  Table 1 shows the globe motility of patients.

Discussion
Scleral buckling is a method used to connect retina by indenting sclera with surrounding explants. The present study emphasized on estimating muscle imbalance, restrictive motility in different gazes and outcomes of scleral buckling surgery for retinal detachment. Figure 3: Visual Outcomes among Population on all Three Follow-ups There are several mechanical reasons for postoperative muscles imbalance following buckling surgery. The most frequently addressed reasons include globe shape deformation by the collective effect of explants, damage to the extraocular muscles by traction sutures, reduction of buckling material, Tenon's capsule scaring from periocular anesthesia and orbital fat. (5,6,7,8,9) The differences seen in total deviation in the area of maximal deviation among our cohorts deduced that of the small number of different mechanisms, that participate in development of strabismus, the buckle if present increases the deviation in the extreme of gazes. The cause of this may be the tethering effect of buckling material on the vector forces of the muscles with which they are in direct contact, and this effect is multiplied in extremes of gaze. In our study, all cases were treated with full 360 encirclement and the 360 band was in contact with all the four muscles, as the buckle was not removed in any case. The deviation horizontal, vertical and combined were present and restrictions of all four major gazes elevation, depression, adduction and abduction were seen and increased somewhat in two months duration. Table 2 Some authors have suggested that post-operative muscles imbalance induced by the buckling is temporary (10,11), however the limitations of our study was that follow up period was too short to infer any such conclusion. Anatomical success rates are generally higher at specialized clinics in developed countries than in the third world countries. Comer and his colleagues reported a final success rate of 97.4% at Cambridge UK 29, but in current study the success rate was about 79.1%. (12) A study conducted in Iran by Ahmadieh H and his colleagues and documented the visual outcomes as, 44% achieved visual acuity better than 6/60. (11) Another study conducted in Zaire, out of 34 eyes that were reattached at the last clinic visit, 21 (62%)

Outcomes of Scleral Buckling
achieved a vision of 6/60 or better but that represents only 27% of the total number of eyes operated. One more study in Andhra Pradesh, 65% of eyes achieved 6/60 or better postoperatively. Among successfully reattached eyes, 80% could see at least 6/60 31 and in current study under discussion 47.91 % of the study population achieved 6/60 to 6/36 and about 10.41% achieved 6/24 or better. (13) In this study, the risk factors of retinal detachment are also studied. Trauma was the biggest risk factor, others were pseudophakia, aphakia, and myopia. (14) Another study stated that trauma is an imperative cause of RD in Africa. Trauma was considered to contribute to the detachment in 30% of eyes in South Africa and 23% in Zaire. In Minnesota trauma was responsible for 7% of detachments and in Japan blunt trauma accounted for only 1.6%. (8) Another study suggested that male sex, young age, myopia, and increased axial length were all correlated with an increased risk of retinal detachment. (10)

Conclusion
Ocular restriction among the patients was observed over a period of 2 months and it depicted that encircling with sclera buckling elicited an increase in restrictive ocular motility from pre-operative to 1 week and 2 months after surgery

Limitations of Study
• The duration of both study and follow-up was very short. • Sample size was small. • Resources were limited.