OCT Indicators of Visual Outcome after Silicone Oil Removal

Author Block: Daisy Liu  , Stephen Carrell, Mark Seamone, Mark Greve.  University of Alberta.

Author Disclosure Block: D. Liu:   None.  S. Carrell:   None.  M. Seamone:   None.  M. Greve:   None.

Abstract Title: OCT Indicators of Visual Outcome after Silicone Oil Removal

Abstract Body: Purpose:   Silicone oil (SO) is a tamponade agent used to surgically treat complex retinal detachments. With known complications including cataract, glaucoma, elevated intraocular pressure, it is generally not used long-term and requires removal in most cases. Vision commonly improves after SO removal compared to prior to placement, however the visual outcome may be unpredictable. The purpose of our study is to use optical coherence tomography (OCT) to evaluate whether there are features pre- and post-operatively that are associated with either good or poor visual outcomes after SO removal.   Study Design:   Retrospective cohort study   Methods:   Electronic medical records of patients seen at a Canadian retina specialty clinic (Alberta Retina Consultants) who received silicone oil tamponade for rhegmatogenous retinal detachment between January 1, 2016 to October 1, 2020 were collected and reviewed. Information about patient demographics, clinical and surgical history were recorded. Features of patients' OCTs (central subfield thickness, transverse foveal thickness, volume scan of macula, condition of the ellipsoid layer, appearance of retinal layers, presence of cystoid macular edema, and foveal contour) were documented and compared. Grading of OCTs was conducted by two independent masked retinal specialist physicians.   Results:   A total of 279 patients (283 eyes) were included in this study of which 71.7% were male with a mean age of 63.8 years. There were 88 (31%), 153 (54%), and 42 (14.8%) eyes in the good (20/40 or better), moderate (20/50 to 20/200), and poor (20/400 to NLP) final vision groups respectively. The average length of time eyes remained under SO in each group was 3.59 months, 4.72 months, and 6.78 months respectively. The poor vision group underwent the longest duration under oil tamponade; vision decreased as duration under oil increased. The delta visual acuity (Logmar) comparing last VA collected under SO and the final follow up VA was -0.48, -0.35, and 0.22 in the good, moderate, and poor vision groups, respectively. This indicates the good and moderate vision groups gained the most lines of vision after oil removal. 154 patients had OCTs acceptable for analysis. The central subfield thickness on OCT after oil removal in the good, moderate, and poor vision groups were 315.9, 306.7, and 305.2 micrometers respectively. Other parameters of retinal thickness including mean thickness of the transverse cut through the fovea, and mean volume scan of the macula were also reduced after SO tamponade. This reduction was greater in the moderate and poor vision groups and persisted after SO was removed.   Conclusions:   Silicone oil tamponade to treat rhegmatogenous retinal detachment yields good to moderate final visual acuity in 85% of patients. Preliminary data shows patients who underwent a longer duration of time under oil had worse visual outcomes. Those with poor vision have reduced central subfield thickness, transverse foveal thickness, and macular volume on OCT imaging.