Retinal Sensitivity before and after silicone oil removal using microperimetry

Session Details

Session Title: Free Paper Session 21: Imaging III

Session Date/Time: Sunday 10/09/2017 | 08:00-09:30

Paper Time: 08:54

Venue: Room 113

First Author: : M.Youssef EGYPT

Co Author(s): :    G. Azab                             

Abstract Details

Purpose:

Silicone oil is widely used as a tamponading agent in vitreoretinal surgery, especially in complicated retinal detachment. Removal of silicone oil, as early as possible, may reduce complications such as cataract, glaucoma, vision loss and may help avoid potential toxic effects. Aim of this work is to investigate possible toxic effect of silicone on retina through assessment of retinal sensitivity, using microperimetry, before and after silicone removal and to correlate the change in retinal sensitivity with duration of silicone tamponade. As a secondary outcome, change in overall retinal sensitivity will be correlated with change in best corrected visual acuity (BCVA).

Setting:

Prospective comparative study carried out in Ophthalmology department, Kasr Alainy Hospital, Cairo University in the period from May 2016 to August 2016.

Methods:

The study included 22 consecutive patients, admitted for silicone oil removal. All patients underwent 23-guage pars plana vitrectomy with silicone oil (5000 centistokes) injection. The initial pathology in all patients was myopic macula-off retinal detachment. Patients doing vitrectomy for proliferative diabetic retinopathy, recurrent detachments, macular holes, grade C and D proliferative vitreoretinopathy were excluded from study. Patients with chorioretinal degenerations involving macula and those who developed complications in form of visually significant cataract, glaucoma, silicone oil emulsification, recurrent detachment and hypotony following oil removal were excluded as well. Before silicone oil removal, all patients underwent full ophthalmological examination in form of measurement BCVA, intraocular pressure (IOP), slit-lamp examination and dilated fundus examination. Similar examination was carried out after silicone removal. Patients were divided into 2 groups according to duration of silicone tamponade: group A; silicone tamponade <3months and group B; silicone tamponade from 3-6 months. Microperimetry was done for all patients one day before silicone oil removal and one month after surgery. Retinal sensitivity was tested at 28 points: 4 stimuli at 1.0º, 12 stimuli at 3.5º and 12 stimuli at 5.5º. The overall retinal sensitivity and sensitivity of each ring (inner, middle and outer) were assessed.

Results:

There were 3 females and 7 males in Group A, 3 females and 9 males in Group B. The mean age was 36.7 ± 10.9 years and 39.4 ± 8.8 years in group A & B, respectively. In Group A, there were 3 phakic and 7 pseudophakic patients. In group B, all patients were pseudophakic. The BCVA was significantly improved postoperatively (0.69 versus 1.06 and 0.69 versus 1.07 in Groups A & B, respectively). IOP was significantly reduced postoperatively (12.89 ± 1.05 mmHg versus 14.89 ± 1.76 and 13.33 ± 1.30 mmHg versus 15.33 ± 3.11 mmHg in Groups A & B, respectively) The overall retinal sensitivity was significantly increased postoperatively. In group A, the mean postoperative overall retinal sensitivity was 8.70±2.56 dB versus 5.68±2.00 dB (p = 0.008). In group B, it was 9.83±3.36 dB versus 7.00±2.55 dB (p = 0.002). The retinal sensitivity at the inner, middle and outer rings was significantly improved postoperatively. Comparing the preoperative and postoperative microperimetric values between the two groups, no statistically significant difference was found in most parameters. Improvement in the postoperative BCVA was correlated with improvement in postoperative overall retinal sensitivity (r = 0.060). However, this correlation was not statistically significant.

Conclusions:

The overall retinal sensitivity measured by microperimetry, as well as retinal sensitivity at inner, middle and outer rings, was significantly increased following silicone oil removal in both groups. However, no statistical significance was found between the 2 groups when comparing most of microperimetric parameters. Several hypotheses have been proposed about pathophysiology of potential toxic effects of silicone. However, it is not well known which of these hypotheses could be reversible, in order to explain significant improvement in retinal sensitivity after silicone oil removal in our study. Several case series have reported visual loss in patients with macula-on retinal detachment after vitrectomy and silicone oil tamponade. The visual loss described in these series was found to be permanent in most patients. Larger prospective studies are required for better understanding the potential toxic effect of silicone on retina and determining the proper timing of silicone oil removal. These studies should combine both functional and structural evaluation of macula.

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