Retinal vascular changes after Silicon Oil removal in the Eye with Rhegmatogenous Retinal detachment

Abstract

Background

This study aims to examine vessel density changes in the optic nerve and macula following silicone oil removal (SOR) surgery in eyes with rhegmatogenous retinal detachment (RRD) at different time points by Optical Coherence Tomography Angiography (OCTA) in compared to the contralateral eye.

Methods

A total of 43 eyes from 43 patients with silicone oil in their eyes for 3–9 months underwent OCT-A using AngioVue and optic disc-associated vessel density (VD) and thickness, macular-associated VD and thickness, Foveal avascular zone (FAZ) area, FAZ perimeter (PERIM), Acircularity index (AI), vessel density within a 300 μm wide region of the FAZ were compared between eyes. OCTA scans were performed one week before SOR and one month and three months after SOR.

Results

The mean age of participants was 52.8 years (SD = 15.85) and a median visual acuity was 0.8 (range: 0.5-1.0). Notably, male participants constituted 67.4% of the sample. The preoperative mean value BCVA (logMAR) of patients was 0.73, and 3 months post-oil removal was 0.7727. Regarding optic disc parameters, RNFL thickness and vessel density (VD) measurements Peripapillary, whole disc, inside disc, and Disc Angio (superior, Nasal, inferior, temporal) did not change.

In analyzing macular thickness parameters, all of them (Whole and Fovea, parafoveal, and Perifovea) remained unchanged. Examining macular vessel density parameters revealed no significant changes across superficial and deep retinal layers. Finally, the comparison of the foveal avascular zone (FAZ) area and flow density (FD) parameters demonstrated consistent measurements with non-significant alterations observed in FAZ size (p = 0.6) and FD values (p = 0.49) over the monitored duration.

Conclusion

There was no change in peripapillary VD and macular vessel density of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) after silicone oil removal. FAZ and full retinal thickness  remained stable 3 month after SOR. 

Clinical trial number: Not applicable.

Introduction

Silicone oil (SO) is commonly used to treat various retinal illnesses such as rhegmatogenous retinal detachment and proliferative retinopathy. Silicone oil is utilized as a tamponade in cases of diabetic retinopathy, severe retinal damage, and endophthalmitis. Silicone oil can be utilized as an efficient intraocular tamponade because of its high viscosity and surface tension [1,2,3].

Several studies argue that this therapeutic procedure may have potential adverse effects. Complications including cataracts, keratopathy, glaucoma, and optic neuropathy have been documented after silicone oil injection [4,5,6].

Silicone oil tamponade might cause unexplained visual impairment as a secondary effect. Research utilizing Spectral-domain optical coherence tomography (SD-OCT) has demonstrated that silicone oil can induce alterations in the thickness of the inner retinal layer, potentially leading to visual impairment [7, 8].

Nowadays, Optical Coherence Tomography Angiography (OCTA) allows for non-invasive imaging of the retinal and choroidal vascular anatomy in three dimensions without the need for a contrast agent injection. The technique characterizes the microvascular and macrovascular circulation of the retina and optic nerve in patients with ocular vascular disorders [9]. Our study examined and contrasted alterations in superficial and deep macular vascular density and in patients who underwent pars plana vitrectomy with silicone oil removal using OCTA.

Materials and methods

Study design

The prospective cross-sectional study was conducted at the Department of Ophthalmology in Feiz Hospital, Isfahan, Iran between April and December 2023. The study protocol was accepted by the ethical committee of Isfahan University of Medical Sciences. All participants received written informed consent.

This study included 43 eyes from 43 participants with Unilateral RRD that were successfully repaired using pars plana vitrectomy (PPV) with light SO tamponade for 3–9 months and followed for more than 3 months after SOR surgery. These patients had a history of total RRD with up to grade 1 Proliferative Vitreoretinopathy without other ocular pathology. People with a history of glaucoma, ischemic optic neuropathy, or uveitis, or with systemic disorders such as hypertension or diabetes were not included in the study. Patients with a follow-up period of less than 3 months, the presence of recurrent retinal detachment, or simultaneous silicone oil removal surgery with epiretinal membrane (ERM) or internal limiting membrane (ILM) removal and had a history of ocular trauma or ocular surgery during follow-up period, were excluded from the study.

Intervention

Patients who were candidates for silicone oil removal surgery at Feiz Hospital in Isfahan and met the criteria of our study were invited to participate in this study after giving detailed explanations. A complete medical record including past eye problems and general health was taken from each patient. Participants received various eye tests, including auto-refractometry, uncorrected and corrected distance visual acuity evaluation, slit lamp examination, Goldman and Tonopen tonometry for measuring intraocular pressure and dilated fundus examination with a 78-diopter lens. The evaluations took place one week before the silicone oil removal procedure and were repeated, one month, and three months after the operation. Macular and optic disc Optical Coherence Tomography Angiography (OCTA) scans were performed using the RTVue XR Avanti AngioVue system (Optovue Inc, Fremont, CA, USA) with AngioVue OCTA software by a single operator, one week before removing the silicone oil and after, one month, and three months after the surgery for all participants. All macular OCTA was performed by acquiring a 6 mm × 6 mm scan pattern which was automatically centered on the fovea. A three-dimensional projection artifact removal technique was applied to improve the accuracy of the data. PR-OCTA algorithms are designed to reduce projection artifacts by recognizing that the reflectance-normalized signal in these artifacts is weaker than the true in situ flow signal in the same axial line. The algorithm uses the structural OCT signal to weight the flow signal in the OCTA volume, keeping the highest in situ flow values and suppressing the rest to background levels. This process performed volumetrically, removes projection artifact tails from cross-sectional images, providing cleaner volumes compared to slab subtraction, though some limitations remain. All the investigated parameters were automatically calculated. The scans were evaluated by two ophthalmology specialists skilled in interpreting retinal OCT images. We analyzed the RNFL thickness, disc VD, macular (fovea, parafovea, perifovea) thickness, macular (fovea, parafovea, perifovea) superficial and deep capillary plexus (SCP and DCP) VD, FD and FAZ. All OCTA scans were reviewed to ensure their quality was sufficient (Scan Quality Indicator > 6/10). The same vitreoretinal surgeons performed SO (Oxane 5700 and 1300, Bausch & Lomb, Rochester, NY, USA) removal surgery. Fluid-air exchange was applied to reduce the number of emulsified SO droplets. The opposite eye was used as a control. The unaffected fellow eye was used in analyses for comparison with post-operative eyes.

Statistical analysis

Data analysis utilized SPSS version 22 software. The statistical analysis employed descriptive statistics to characterize the patient.

Comparative analyses, including repeated measures tests, assessed changes in measured parameters before and after silicone oil removal. Significance was determined at P-values of < 0.05.

Results

The present research was conducted on 43 eyes with silicone oil removal and 43 healthy contralateral ones. The study investigated patient demographics and clinical characteristics, revealing a mean age of 52.8 years (SD = 15.85) and a median visual acuity of 0.8 (range: 0.5-1.0). Notably, male participants constituted 67.4% of the sample. Due to poor patient compliance and lack of regular visits, the follow-up period was determined to be 3 months. The basic characteristics of the patients are summarized in Table 1. Analysis of visual acuity measured in Log MAR units at baseline, month 1, and month 3 demonstrated a progressive increase in mean values from 0.7386 to 0.7727 over the three months. Regarding optic disc parameters before and after silicone oil tamponade removal, fluctuations in mean values were observed across various parameters from baseline to month 1 and month 3. Affected eyes had lower whole disc, and peripapillary vessel density compared to unaffected eyes in baseline (p < 0.05). Also affected eyes had lower superficial VD (whole, parafovea in temporal and inferior) and deep VD (parafovea in temporal and perifovea temporal) compared to unaffected eyes (p < 0.05). No statistically significant differences were found for FAZ or macular thickness ( foveal, parafoveal, and perifoveal) between the affected and contralateral healthy eyes. The results are shown in Tables 2, 3 and 4.

Table 1 Demographic and clinical characteristics of the patients

Table 2 Comparison of circumpapillary retinal nerve fiber layer (RNFL) thickness and vessel density between affected eyes and unaffected eyes

Table 3 Comparison of macular thickness between affected eyes and unaffected eyes

Table 4 Comparison of macular vessel density  between affected eyes and unaffected eyes

The repeated escarpment tests for the affected eyes and healthy eyes revealed no statistically significant changes over time for the following measurements: RNFL, and RPC density (whole, inside, peripapillary -superior, temporal, nasal, inferior), superficial and deep macular vessel density and macular thickness. In the case of deep vessel density, significant mean differences were observed in the parafovea superior region between preoperative time and one month after silicone oil tamponade removal time (mean difference = −1 μm, p = 0.04) and in the parafovea inferior region between the preoperative and three months after silicone oil tamponade removal (mean difference = −5 μm, p = 0.03). Finally, the comparison of the foveal avascular zone (FAZ) and flow density (FD) parameters before and after silicone oil tamponade removal demonstrated consistent measurements with non-significant alterations observed in FAZ size (p = 0.6) and FD values (p = 0.49) over the monitored duration. Changes in retinal vessel density and thickness before and after surgery in affected and unaffected eyes are shown in Fig. 1.

Fig. 1

Changes in retinal vessel density and thickness before and after surgery in affected and unaffected eyes. As shown in figure, no significant changes occurred after so removal. A Peripapillary vessel density at optic nerve head   B Superficial  macular vessel density C Deep macular vessel density D Peripapillary RNFL    E Total macular thickness  F Total  Foveal thickness

Discussion

Silicone oils are commonly used in vitreoretinal surgery due to their long-lasting properties, biocompatibility, and inertness to chemicals [11]. These attributes help maintain the connection between the retina and the retinal pigment epithelium, blocking harmful substances from the healing area, and making them essential in such operations [12]. However, because silicone oils are less dense than water, they float in the eye, potentially providing insufficient support for the lower retina if the vitreous cavity isn’t filled [13]. Silicone oils can emulsify and disperse, leading to complications like inflammation, vision changes, increased intraocular pressure, and glaucoma, often necessitating removal surgery. Despite removal, tiny droplets can persist for up to 11 years, though about 30% of patients see improved visual acuity post-removal [14].

Optical Coherence Tomography Angiography (OCTA) revolutionizes optic nerve and macula evaluation by offering precise, non-invasive imaging of retinal blood vessels, aiding in early disorder detection and treatment decisions with high-resolution images without the need for contrast chemicals [15]. In our study, we focused on evaluating the optic nerve and macula, finding no statistically significant changes over time for the optic disc and macular parameters in OCT angiography, consistent with previous studies [10, 16]. Xiang et al. [10] and Nassar GA [16]. showed that SO use for less than six months has no significant effect on the macular capillary vessel density (VD) of the superficial capillary plexus (SCP) and deep capillary plexus (DCP). However, we observed significantly lower peripapillary optic disc and superficial and deep macular vessel densities in silicone oil removal eyes compared to healthy eyes, with no significant changes over three months. Previous studies regarding the analysis of OCTA findings in SO removal are summarized in Table 5 [10, 16,17,18,19,20,21,22,23].

Table 5 Summery of recent studies of silicone oil removal effect retina

In the current study, the average total retinal thickness (whole, fovea, parafovea, and perifovea) was higher in eyes with silicone oil compared to healthy eyes but not significantly so, which aligns with a previous study [23]. There was no significant change in average total retinal thickness after silicone oil removal, consistent with prior findings [23]. We noted a decrease in the fovea, parafovea, and perifovea thickness measurements between baseline and three months post-operation, but these changes were not significant. This is the first study to separately evaluate these macular regions. After silicone oil removal macular thickness(whole, fovea, parafovea, perifovea) was not significantly different over three months which is consistent with Karakosta C [23].

The findings showed no significant changes in superficial and deep macular vessel density pre- and post-silicone removal. Prior studies demonstrated significant reductions in SCP and DCP densities in individuals after SO removal [10, 16, 20], but other reports indicated changes in vessel density [16, 23]. In our study, optic disc vessel densities decreased over time in the control group, but increased in the patient group but not significantly.

Our study observed a greater size and perimeter of the foveal avascular zone (FAZ) in the SO group compared to the control group, suggesting higher vascular impairment, though insignificant. FAZ parameters remained stable across different groups. These findings of our study were consistent with previous studies [10, 16, 19, 23] The FAZ parameters (area, perim, and FD) remained stable across different groups.

Our studies indicate that peripapillary vessel density increased over time in affected eyes, similar to findings by Karakosta C and Hue Y [22, 23]. , but. Nassar G A [16]reported a significant increase in postoperative VD of the whole disc and peripapillary capillary plexus. Our study showed different trends over time in control versus patient eyes. Vessel density decreased over time in the control group but increased in the patient group. These results collectively suggest that patients experienced an increase in vessel density over time, contrasting with the control group where a decrease was observed.

Lee et al. [24]found that SO tampon duration significantly correlates with VD in the DCP. Discrepancies between our findings and others may be due to differences in SO tamponade durations, inclusion and exclusion criteria, OCTA devices, sample sizes, follow-up periods, and study designs. Our study had several limitations: the cross-sectional methodology, small sample size, short duration of follow-up, and lack of investigation into systemic medication effects. Prospective studies with larger sample sizes could provide more insights into the effect of SO on OCT angiography.

Conclusion

Silicone oils are essential in vitreoretinal surgery for their longevity, biocompatibility, and chemical inertness, but they can float in the eye and cause complications like inflammation and increased intraocular pressure. Our study found no significant changes in retinal thickness or vessel density over time after silicone oil removal, with observed trends consistent with previous research.

Availability of data and materials

No datasets were generated or analysed during the current study.