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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 113  |  Issue : 3  |  Page : 118-123

Optical coherence tomography study of macular structural changes in silicone oil-filled eyes


Department of Ophthalmology, Faculty of Medicine, Tanta University, Tanta, Egypt

Date of Submission09-Apr-2020
Date of Acceptance24-Jun-2020
Date of Web Publication07-Sep-2020

Correspondence Address:
MD, FRCS (Glasg) Amin E Nawar
Department of Ophthalmology, Faculty of Medicine, Tanta 31516
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ejos.ejos_21_20

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  Abstract 

Introduction Silicone oil (SO) has been used in complex cases of retinal detachment with proliferative vitreoretinopathy (PVR), giant retinal tear, and traumatic cases. This study aimed to assess macular structural changes in SO filled eyes after pars plana vitrectomy (PPV) for rhegmatogenous retinal detachment with PVR.
Patients and methods This is a prospective interventional study that was conducted on 60 SO-filled eyes after successful PPV for rhegmatogenous retinal detachment with grade C PVR; SO was left in all eyes for a duration of 3 months. Thorough ophthalmic evaluation in Ophthalmology Department, Tanta University, Egypt was performed including best corrected visual acuity (BCVA), fundus examination, and anterior segment examination. Optical coherence tomography was done for all patients at presentation to assess the macular area.
Results Epiretinal membrane (ERM) was detected in 14 (23.3%) eyes, cystoid macular edema (CME) in 21 (35%) eyes, photoreceptor disruption in 21 (35%) eyes, macular hole in one (1.7%) eye, and foveal thinning in 18 (30%) eyes. The BCVA was positively correlated with the presence of ERM, CME, and photoreceptor disruption and the results were statistically significant with ERM and photoreceptor nonintegrity with P values of 0.049 and 0.001 respectively. In addition, there is no significant correlation between changes in central retinal thickness and BCVA.
Conclusion Visual loss after successful PPV in SO filled eyes can occur due to macular changes like CME, ERM, photoreceptor disruption, foveal thinning, and macular hole.

Keywords: best corrected visual acuity, central retinal thickness, cystoid macular edema, epiretinal membrane, pars plana vitrectomy, proliferative vitreoretinopathy, rhegmatogenous retinal detachment, silicone oil


How to cite this article:
Nawar AE. Optical coherence tomography study of macular structural changes in silicone oil-filled eyes. J Egypt Ophthalmol Soc 2020;113:118-23

How to cite this URL:
Nawar AE. Optical coherence tomography study of macular structural changes in silicone oil-filled eyes. J Egypt Ophthalmol Soc [serial online] 2020 [cited 2020 Sep 22];113:118-23. Available from: http://www.jeos.eg.net/text.asp?2020/113/3/118/294445


  Introduction Top


Silicone oil (SO) was first described by Cibis for the treatment of complicated cases of retinal detachment [1]. SO has been used in cases with complex retinal detachments, trauma, giant retinal tears, and proliferative vitreoretinopathy (PVR) [2],[3],[4],[5],[6]. Multiple complications were recorded with the use of SO such as cataract, glaucoma, and band-shaped keratopathy [7],[8],[9],[10]. SO removal is recommended as soon as possible to avoid its complications that can affect the final visual acuity (VA) [11],[12],[13]. The anatomical success after pars plana vitrectomy (PPV) for rhegmatogenous retinal detachment (RRD) is mostly not correlated with functional results; in one study, macular changes were detected in 87% of cases after PPV for complicated RRD with PVR [14].

The present study evaluates macular changes that occur in SO filled eyes after successful PPV for RRD.


  Patients and methods Top


Study design

This is a prospective interventional study in which optical coherence tomography (OCT) was conducted on 60 eyes of 60 patients with a history of RRD of 3 months duration, Patients were treated with 23-G PPV with SO endotamponade (5000 Centistokes, FCI Ophthalmic Community) by a single experienced surgeon. The indication of SO tamponade was complicated cases of retinal detachment with grade C PVR according to Retinal Society Classification.

All procedures in the present study were performed according to the Ethical Standards of the Institutional and/or National Research Committee and with the 1964 Helsinki Declaration and its later amendments. Informed consent was obtained from all individuals who participated in the study.

Participants

The study included 60 eyes of 60 patients with macula-off retinal detachment with grade C PVR. The duration of retinal detachment was about 3 months. The 23-G PPV was performed; at first, core vitrectomy was done followed by triamcinolone-assisted posterior vitreous detachment. Perfluorocarbon was injected into the vitreous cavity to flatten the retina till the posterior edge of the retinal break, followed by shaving of the vitreous base and 360 endolaser barrage of moderate intensity burns. Finally, air perfluorocarbon exchange was done followed by silicone (5000 Centistokes) injection. Internal limiting membrane peeling using brilliant blue stain was only performed in cases presented with retinal detachment associated with posterior PVR or epimacular membrane. Three months later, thorough ophthalmic evaluation for all patients was done including best corrected visual acuity (BCVA) using the Landolt C chart that was converted to logMAR for statistical analysis, anterior segment examination using slit lamp, intraocular pressure (IOP) measurement using applanation tonometry, posterior segment examination by slit-lamp bimicroscopy using +78 D lens, and indirect ophthalmoscopy. Spectral Domain OCT (TOPCON 3D OCT, Hasunuma-cho, Itabashi-Ku, Tokyo, Japan) was performed for all cases using vertical seven-line raster protocol to assess the macula 3 months after PPV with SO endotamponade and before SO removal. The central retinal thickness (CRT) in microns was measured manually by a caliber. Cystoid macular edema (CME) was defined as increased retinal thickness with loss of foveal depression, subretinal fluid (SRF) as fluid involving the neurosensory space of the macular area. An informed consent was obtained to participate and to publish the results of the study from all participants.

Patients with a history of other intraocular surgery (except uneventful cataract surgery), diabetes mellitus/diabetic retinopathy, coincident retinal pathology as choroidal neovascularization and age-related macular degeneration, previous laser photocoagulation therapy, intravitreal injection of triamcinolone acetonide or antivascular endothelial growth factor agents, prior ocular inflammation, presence of retinal degeneration, and retinal neovascularization or rubeosis were excluded from the study.

Data were analyzed using the Statistical Package for the Social Sciences (SPSS). χ2-test of significance was used for comparison between groups. Spearman’s correlation coefficient was used to calculate the correlation between variables (P<0.05 was considered statistically significant. r≥0.5 indicated good correlation).


  Results Top


Baseline demographic data is shown in [Table 1]. The BCVA − by logMAR was positively correlated with epiretinal membrane (ERM), CME, and ellipsoid zone (photoreceptor or IS/OS) disruption; and the results were statistically significant in ERM and ellipsoid zone disruption with P values 0.049 and 0.001, respectively ([Table 2] and [Figure 1]a).
Table 1 Illustrating demographic data (age and sex) of the patients

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Table 2 Illustrating BCVA in different cases and its relation with the presence of ERM, CME, ellipsoid zone disruption

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Figure 1 (a) Illustrating the relation between BCVA and ERM, CME and ellipsoid disruption. (b) Illustrating correlation between BCVA and CRT. BCVA, best corrected visual acuity; CME, cystoid macular edema; CRT, central retinal thickness; ERM, epiretinal membrane.

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Furthermore, it was found that there is no significant correlation between BCVA and CRT, so BCVA does not depend on changes of CRT ([Table 3] and [Figure 1]b).
Table 3 Illustrating correlation between BCVA and CRT

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As shown in [Table 4], normal macula was detected in 16 eyes only, SRF in one eye which was associated with CME ([Figure 2]a), full thickness macular hole was reported in one eye only ([Figure 2]b), ellipsoid zone disruption was reported in 21 eyes and foveal thinning (<200 μm) in 18 eyes ([Figure 3]a and b); however, ERM was detected in 14 eyes in whom internal limiting membrane peeling was not performed and CME in 21 eyes. Combined ERM and CME was present in six eyes; combined ERM and foveal thinning was present in five eyes and mixed photoreceptor disruption with foveal thinning was reported in 16 eyes.
Table 4 Illustrating central retinal thickness, number of patients with epiretinal membrane, cystoid macular edema, ellipsoid zone disruption, and macular hole formation

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Figure 2 (a) Illustrating eye with cystoid macular edema and subretinal fluid. (b) Illustrating eye with full thickness macular hole.

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Figure 3 (a, b) Illustrating two eyes with foveal thinning and photoreceptor disruption.

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The mean IOP in the cases of the present study was 12.53±1.77 mmHg, which is considered within the normal range of IOP.


  Discussion Top


Despite the toxic effects of SO, it has been widely used in cases of rhegmatogenous RD with PVR, giant retinal tear, traumatic cases, and other cases with complicated retinal detachment [11],[13],[15],[16]. Many studies have reported the possible toxicity of SO [17],[18]; others explained the toxic consequences of SO by mechanical stress or biochemical reactions [19],[20],[21]. One laboratory study that was done on cases of SO removal detected the presence of certain growth factors between the oil and the retina like the fibroblast growth factor, interleukin-6, and protein; these factors were accused to cause CME and retro-oil epiretinal proliferation and membrane formation [22].

Other studies have evaluated the possible causes of retinal toxicity in SO filled eyes. According to several authors [23],[24], SO can induce ionic flux across the retina with subsequent neuronal apoptosis [25]. Müller cells have the ability to transfer excess K+ into the vitreous cavity [26]. Long-term intraocular SO tamponade can abolish the ability of Müller cells to move K+ into the vitreous resulting in increased level of K+ in the subretinal space [27].

Visual loss after successful vitrectomy for RRD was mainly due to macular abnormalities like macular fold, pigmentary abnormalities, macular hole, and foveal thinning [28],[29]. This study aimed to assess structural macular changes in 60 SO filled eyes in whom PPV for RRD with grade C PVR was performed and to evaluate the possible toxic effects of SO; in the present study the duration of SO inside the eye was 3 months.

Regarding the present study, the macula was free in 16 eyes that represents 26.6% of cases and this percentage was much higher than the Kiss et al. [14] study that detected normal macula in only 12.5% of cases. Furthermore, the present study reported ellipsoid zone disruption in 21 eyes and this is quite similar to other studies that detected photoreceptor non-integrity and atrophy in SO filled eyes [30],[31].

The finding of foveal thinning and photoreceptor disruption in this study agrees with other experimental studies in which SO injection resulted in damage of the photoreceptors with accumulation of vacuoles in the photoreceptor outer segments, thinning, and disappearance of the outer plexiform layer [21],[32].

In respect to this study, 14 eyes were presented with ERM representing 23.3% of cases and 21 eyes with CME representing 35% of cases; this was different from other studies that reported macular microstructure changes before and after SO removal by spectral domain (SD) OCT. In this study, ERM was detected in 26.1%, CME in 19.6%, and SRF in 8.7% of the patients. In this study, the causes of PPV were RRD, proliferative diabetic retinopathy, and macular hole. the authors attributed these macular changes to the primary cause of vitrectomy rather than silicone-oil itself [33]. Another study detected the presence of CME in SO filled eyes that resolved spontaneously after 1 month of SO removal, hence macular changes were attributed to SO [34].

Regarding the present study, SRF was detected in one eye and this was quite similar to Benson et al. [35] who performed a study on 100 patients to define the incidence, duration, and clinical outcomes of persistent SRF after PPV for RRD; 15 patients were found to have SRF after 6 weeks of the surgery. SRF was associated with significantly worse VA.

According to our study, it was found that the BCVA worsened with the presence of ERM, CME, and photoreceptor non-integrity and the results were statistically significant as regards ERM and photoreceptor disruption. This was nearly similar to other studies that stated that CME and ERM formation are one of the most important factors that negatively affect VA in SO filled eyes [36],[37]. On the other hand, CRT did not correlate significantly with BCVA; therefore, CRT is not a factor that affects BCVA.

Regarding the IOP in our cases, the mean IOP was 12.53±1.77 mmHg, which is not coincident with Marti et al. [38], who reported that increased IOP during SO tamponade was the most important risk factor for unexplained visual loss in their series.

The limitations of this study are the absence of comparison between different tamponades like air and gas tamponades and the small number of eyes included and also the lack of studying the effect of the duration of SO on the structure of the macula.


  Conclusion Top


CME, ERM, ellipsoid zone disruption, foveal thinning, macular hole, or combination between these findings can occur in SO filled eyes after successful PPV for RRD; all these changes can explain visual loss in SO filled eyes. Further studies are needed to know if early removal of SO can protect against such changes.

Acknowledgements

The article has been read and approved by the author and he believes that the manuscript represents honest work.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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