Assessment of Retinal Vessel Tortuosity Index in Patients with Fabry Disease Using Optical Coherence Tomography Angiography (OCTA).

Vessel tortuosity (VT) is a parameter used to assess retinal involvement in patients affected by systemic diseases such as Fabry disease (FD). In this study, we assessed a retinal VT index (VTI) using optical coherence tomography angiography (OCTA) in a group of patients with FD (FD cohort) compared to a healthy control group (HC cohort). This is a single-center, retrospective study analysis of all consecutive patients with genetically tested and confirmed FD who underwent regular ophthalmological visits from December 2017 to January 2020 at the Department of Ophthalmology at the University Hospital of Zurich, Switzerland. VTI was calculated for each OCTA image and the results were compared between FD and HC cohort. A total of 56 participants, 32 (male:female ratio 12:20) in the FD cohort and 24 (male:female ratio 13:11) in the HC cohort. Classic onset was determined in 18 patients. Overall, mean VTI (±SD) was 0.21 (±0.07). Male patients with classic-onset FD had a significantly higher mean VTI (0.33, SD ± 0.35) compared to all other subgroups (p-value < 0.05). Further investigations of retinal VTI in patients with FD could be helpful to use OCTA as a noninvasive screening and follow-up modality to assess disease progression in affected patients.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY EVALUATION OF PERIPAPILLARY MICROVASCULAR CHANGES AFTER RHEGMATOGENOUS RETINAL DETACHMENT REPAIR.

PURPOSE: To evaluate the radial peripapillary capillary plexus (RPCP) vessel density (VD) and the retinal nerve fiber layer (RNFL) thickness in eyes successfully treated with pars plana vitrectomy for primary rhegmatogenous retinal detachment. METHODS: In this cross-sectional multicenter clinical study, eyes with a minimum 12-month follow-up were reexamined. The RPCP VD and RNFL thickness in the rhegmatogenous retinal detachment subfields of the affected eye (study group) were compared with the corresponding areas of the healthy fellow eyes (control group). RESULTS: Fifty-three eyes were included in the study. A significantly lower RPCP VD and RNFL thickness were observed in those subfields affected by rhegmatogenous retinal detachment compared with those of the control group (P < 0.001). No statistically significant differences were observed between undetached subfields in the study group and their corresponding images in the control group. In the study group, a significant correlation was found between RPCP VD and RNFL thickness in subfields with detached retina (r = 0.393, P < 0.001) and undetached retina (r = 0.321, P < 0.001). CONCLUSION: Radial peripapillary capillary plexus VD changes were found in the subfields of detached retina successfully treated with pars plana vitrectomy and they correlated with RNFL thinning. These data suggest a coexistence of neuronal and microvascular damage in patients affected by rhegmatogenous retinal detachment.

Safety and Efficacy of Intravitreal Chemotherapy (Melphalan) to Treat Vitreous Seeds in Retinoblastoma.

Background: Active vitreous seeds in eyes with retinoblastoma (Rb) adversely affects the treatment outcome. This study aimed to investigate the safety and efficacy of intravitreal melphalan chemotherapy (IViC) as a treatment for recurrent and refractory vitreous seeds in patients with Rb. Methods: We used a retrospective non-comparative study of patients with intraocular Rb who had vitreous seeds and were treated by IViC (20-30 µg of melphalan) using the safety-enhanced anti-reflux technique. Tumor response, ocular toxicity, demographics, clinical features, and survival were analyzed. Results: In total, 27 eyes were treated with 108 injections for recurrent (16 eyes) or refractory (11 eyes) vitreous seeds after failed systemic chemotherapy. A total of 15 (56%) were males, and 20 (74%) had bilateral disease. At diagnosis, the majority (n = 21) of the injected eyes were group D, and n = 6 were group C. Vitreous seeds showed complete regression in 21 (78%) eyes; 100% (n = 10) for eyes with focal seeds; 65% (n = 11/17 eyes) for eyes with diffuse seeds (p = 0.04); 7 (64%) eyes with refractory seeds; and 14 (87%) eyes with recurrent seeds showed complete response (p = 0.37). In total, 16 (59%) eyes developed side effects: retinal toxicity (48%), pupillary synechiae (15%), cataracts (30%), iris atrophy (7%), and retinal and optic atrophy (4%). Only one child was lost to follow-up whose family refused enucleation and none developed orbital tumor recurrence or distant metastasis. Conclusion: IViC with melphalan is effective (more for focal than diffuse seeding) and a relatively safe treatment modality for Rb that can improve the outcomes of eye salvage procedures. However, unexpected toxicity can occur even with the standard dose of 20-30 µg.

Impact on refractive surgery due to increasing use of personal protection equipment: Insights from EUROCOVCAT group.

Since the World Health Organization declared COVID-19 to be a pandemic on 11th March 2020, changes to social and sanitary practices have included significant issues in access and management of eye care during the COVID-19 pandemic. Additionally, the fear of loss, coupled with social distancing, lockdown, economic instability, and uncertainty, have led to a significant psychosocial impact that will have to be addressed. In the current COVID-19 pandemic, personal protective equipment such as face masks or face coverings have become a daily necessity. While "mass masking" along with hand hygiene and social distancing became more widespread, new issues began to emerge - particularly in those who wore spectacles as a means of vision correction. As we began to see routine patients again after the first lockdown had been lifted, many patients visited our clinics for refractive surgery consultations with a primary motivating factor of wanting spectacle independence due to the fogging of their spectacles as a result of wearing a mask. In this article, we report on new emerging issues in eye care due to the widespread use of masks and on the new unmet need in the corneal and cataract refractive surgery fields.

Ocular Involvement of SARS-CoV-2 in a Polish Cohort of COVID-19-Positive Patients.

The coronavirus SARS-CoV-2 responsible for the current human COVID-19 pandemic has shown tropism toward different organs with variable efficiency, eyes included. The purpose of this study has been to investigate the presence of detectable SARS-CoV-2 infection in ocular swabs in patients affected by COVID-19. A consecutive series of 74 COVID-19-positive patients (age 21-89) were enrolled at two Polish COVID-19 hospitals for 4 months and were characterized by PCR for the presence of the SARS-CoV-2 genetic material in nasopharyngeal (NP) and ocular swabs, while their respiratory and ocular symptoms were noted. Almost 50% of them presented with severe/critical respiratory involvement, and some degree of eye disease. No tight correlation was observed between the presence of ocular and respiratory symptoms. Three male patients presenting with severe/critical lung disease tested positive in ocular swab, however with mild/moderate ocular symptoms. In conclusion, our study lends further support to the view that overt ocular infection by the SARS-CoV-2 virus is not such a frequent occurrence.

Management and Outcomes of Unilateral Group D Tumors in Retinoblastoma.

PURPOSE: Retinoblastoma presents most commonly as advanced unilateral disease, particularly in developing countries for which primary enucleation has been the preferred method of treatment. However, with the evolution of newer treatment modalities including intravitreal chemotherapy, intra-arterial chemotherapy and newer chemotherapeutic combinations, a trend towards more conservative approaches is being observed. Our aim is to evaluate outcomes of group D eyes following conservative and non-conservative treatment options. PATIENTS AND METHODS: The ocular oncology database was used to identify eyes with unilateral retinoblastoma that fulfilled the International Intraocular Retinoblastoma Classification (IIRC) group D criteria from August 2010 to August 2018 and these were retrospectively reviewed. Overall, 39 eyes were identified. RESULTS: Nineteen (49%) eyes underwent primary enucleation and 20 (51%) received eye-conserving treatment. Eye salvage was possible in 15 (75%) eyes in the attempted salvage group. None of the patient revealed signs of metastasis. All eyes received conventional chemotherapy (carboplatin, vincristine, etoposide) and focal laser therapy. Additional treatment modalities offered included intravitreal chemotherapy, intra-arterial chemotherapy and topotecan. Three (11%) eyes in the primary enucleation group showed high-risk features on histopathology and none developed metastasis. CONCLUSION: The results of the study seem promising and conservative measures can be adopted in selected unilateral group D eyes.

Rethinking Elective Cataract Surgery Diagnostics, Assessments, and Tools after the COVID-19 Pandemic Experience and Beyond: Insights from the EUROCOVCAT Group.

The progressive deterioration of the visual function in patients on waiting lists for cataract surgery has a negative impact on their quality of life, especially in the elderly population. Patient waiting times for cataract surgeries in many healthcare settings have increased recently due to the prolonged stop or slowdown of elective cataract surgery as a result of coronavirus disease 19 (COVID-19). The aim of this review is to highlight the impact of such a "de-prioritization" of cataract surgery and to summarize some critical issues and useful hints on how to reorganize cataract pathways, with a special focus on perioperative diagnostic tools during the recovery phase and beyond. The experiences of a group of surgeons originating from nine different countries, named the European COVID-19 Cataract Group (EUROCOVCAT), have been combined with the literature and recommendations from scientific ophthalmic societies and healthcare institutions. Key considerations for elective cataract surgery should include the reduction of the number of unnecessary visits and examinations, adoption of precautionary measures, and implementation of telemedicine instruments. New strategies should be adopted to provide an adequate level of assistance and to guarantee safety conditions. Flexibility will be the watchword and regular updates would be necessary following scientific insights and the development of the pandemic.

Pain Following the Use of Anesthesia Formulation Among Individuals Undergoing Cataract Surgery: A Randomized Controlled Trial.

PURPOSE: To assess the pain intensity of two intracameral anesthetic solutions in patients undergoing cataract surgery and evaluate the factors influencing the patients' postoperative activities. METHODS: Sixty-two patients undergoing cataract surgery were randomized to receive the study drug - a manufactured solution of 0.02% tropicamide/0.31% phenylephrine/1% lidocaine (Mydrane) or a traditional anesthetic formulation - solution of 1% lidocaine/0.025% adrenaline as an intraocular anesthetic. The pain intensity was assessed by Visual Analog Scale for Pain (VAS Pain) and Brief Pain Inventory-short form (BPI) on the next day after the surgery. RESULTS: The mean pain score measured preoperatively with VAS Pain was 0.34 in Mydrane group and 0.09 in the reference group (p = 0.51). There were no statistically significant differences between the two anesthetic methods with respect to pain intensity during the surgery (p = 0.94) and the influence of pain during the last 24 h on activity (p = 0.79), mood (p = 0.31), social contacts (p = 0.29), sleep (p = 0.5) and the joy of life (p = 0.39). Additionally, there was no statistically significant influence of age, sex, lateralization, co-existing ophthalmological diseases (p = 0.98) and post-operative complications (p = 0.4) on the experienced pain measured during the surgery and in the last 24 h. CONCLUSIONS: New commercially available intraocular anesthetic solution (Mydrane™) seems to be as effective as off-label traditional anesthetic formulation, in reducing the pain experienced during cataract surgery under topical anesthesia.

Comparative Safety of Bevacizumab, Ranibizumab, and Aflibercept for Treatment of Neovascular Age-Related Macular Degeneration (AMD): A Systematic Review and Network Meta-Analysis of Direct Comparative Studies.

BACKGROUND: Since the efficacy of ranibizumab (RBZ), bevacizumab (BVZ) and aflibercept (AFB) is comparable in neovascular age-related macular degeneration (AMD), we conducted a systematic review and meta-analysis to evaluate the long-term safety profiles of these agents, including ocular safety. METHODS: Systematic review identifying randomized controlled trials (RCTs) comparing RBZ, BVZ and AFB directly published before March 2019. Serious ocular adverse events (SOAE) of special interest were endophthalmitis, pseudo-endophthalmitis, retinal pigment epithelium tear and newly identified macular atrophy. RESULTS: Thirteen RCTs selected for meta-analysis (4952 patients, 8723 people-years follow-up): 10 compared RBZ vs. BVZ and three RBZ vs. AFB. There were no significant differences in almost all adverse events (systemic and ocular) between BVZ, RBZ and AFB in up to two years' follow-up. Macular atrophy was reported heterogeneously and not reported as SOAE in most trials. CONCLUSIONS: Direct comparison of RBZ, BVZ and AFB safety profiles in the RCT network meta-analytical setting have not revealed a consistent benefit of these three commonly used anti-vascular endothelial growth factor (anti-VEGF) agents in AMD. Network model ranking highlighted potential benefits of RBZ in terms of a systemic safety profile; however, this appears a hypothesis rather than a conclusion. Newly identified macular atrophy is underestimated in RCTs-future real-world data should be focused on SOAE.

Vascular changes after vitrectomy for rhegmatogenous retinal detachment: optical coherence tomography angiography study.

PURPOSE: To analyse the postoperative foveal avascular zone (FAZ) area, superficial vessel density (SVD) and deep vessel density (DVD) and their correlation with functional (best-corrected visual acuity, BCVA) and anatomical outcomes (foveal macular thickness, FMT) after surgery for rhegmatogenous retinal detachment (RRD) repair. METHOD: Patients with RRD eyes, successfully treated with a single pars plana vitrectomy (PPV) with gas tamponade and a minimum 12 months follow-up, were re-examined. Foveal avascular zone (FAZ) area, SVD, DVD and FMT were evaluated by using optical coherence tomography angiography (OCTA) and compared to fellow eye. RESULTS: Fifty-six patients with macula-on and 37 with macula-off RRD were included in the study. In both groups, no difference in FMT and FAZ area was found compared to fellow eyes. In macula-on RRD eyes, a lower parafoveal DVD (p = 0.001) was detected; FAZ area was related to FMT (p = 0.025), and the postoperative BCVA was correlated with parafoveal DVD (p = 0.010) and FAZ area (p = 0.003). In macula-off RRD eyes, lower parafoveal SDV (p = 0.012), and foveal and parafoveal DVD (p = 0.012 and p < 0.001, respectively) were observed. BCVA was related to FAZ area (p = 0.012), foveal SVD (p = 0.005) and parafoveal DVD (p = 0.010). CONCLUSION: Rhegmatogenous retinal detachment eyes successfully treated with PPV had lower vessel density in the superficial and deep retinal plexus compared to fellow healthy eyes; BCVA was related to FAZ area and vessel density.

Effect of Resveratrol on In Vitro and In Vivo Models of Diabetic Retinophathy: A Systematic Review.

A large number of preclinical studies suggest the involvement of resveratrol in the prevention and treatment of eye diseases induced by oxidative stress and inflammation. We tested the hypothesis that resveratrol influences many pathways of in vitro and in vivo models of diabetic retinopathy through a systematic literature review of original articles. The review was conducted in accordance with the PRISMA guidelines. A literature search of all original articles published until April 2019 was performed. The terms "resveratrol" in combination with "retina", "retinal pathology", "diabetic retinopathy" and "eye" were searched. Possible biases were identified with the adopted SYRCLE's tool. Eighteen articles met inclusion/exclusion criteria for full-text review. Eleven of them included in vitro experiments, 11 studies reported in vivo data and 3 studies described both in vitro and in vivo experiments. Most of the in vivo studies did not include data that would allow exclusion of bias risks, according to SYRCLE's risk of bias tool. Both in vitro and in vivo data suggest anti-apoptotic, anti-inflammatory and anti-oxidative actions of resveratrol in models of diabetic retinopathy. However, results on its anti-angiogenic effects are contradictory and need more rigorous studies.

Functional and morphological results of treatment of macula-on and macula-off rhegmatogenous retinal detachment with pars plana vitrectomy and sulfur hexafluoride gas tamponade.

BACKGROUND: To examine morphological and functional results after pars plana vitrectomy (PPV) with sulfur hexafluoride (SF6) gas tamponade due to macula-on and macula-off rhegmatogenous retinal detachment (RRD) during 6 months of the follow-up. METHODS: The study included 62 eyes that underwent successful PPV with SF6 tamponade with macula-on (34 eyes) and macula-off (28 eyes) RRD preoperatively. The best-corrected visual acuity (BCVA), Amsler test, M-charts, optical coherence tomography (OCT) and microperimetry were performed at 1, 3 and 6 months postoperatively. RESULTS: Results of the Amsler test were abnormal postoperatively in 54% of the patients in the group with macula-off and in 32% of the patients with macula-on RRD. Horizontal M-charts improved significantly from 0.33 to 0.2, vertical M-charts- from 0.29 to 0.17 during 6 months of the follow-up. There was a significant increase in the central retinal thickness (CRT) and average thickness (AT) between follow-up examinations only in the macula-off group. 29 of 62 eyes (47%) after surgery (equally with macula-on and macula-off RRD) showed morphological changes in OCT in the macular region, as epiretinal membrane, macular edema, subretinal fluid or alterations of the outer layers of the retina. The average threshold in microperimetry increased significantly within both groups during the follow-up. CONCLUSION: Both horizontal and vertical M-charts scores, as were as microperimetry sensitivity improved significantly during the 6 months of the follow-up both in macula-on and macula-off group. Although PPV with SF6 gas tamponade was successful, almost half of eyes revealed anatomical changes in the macular region in OCT both with macula-on and macula-off group. TRIAL REGISTRATION: Current Controlled Trials NCT03902795 registered on 03/04/2019. Retrospectively registered.

Changes in visual function and ocular morphology in women who have undergone ART treatment and children born as a result of ART treatment: a systematic review.

As all the structures of the human eye are characterized by sex hormone receptors, this study tested the hypothesis that assisted reproductive technology (ART) treatment influences visual function and ocular morphology in women who have undergone ART treatment and children born as a result of ART treatment. A systematic literature search of all original articles published up to August 2018 was performed using the PubMed database, including all original studies available in the literature. Review articles, studies in which participants underwent mixed interventions (i.e. other than ART treatment), studies reporting data on ocular malformations in ART offspring, and studies written in languages other than English were excluded. All selected articles were analysed to assess the level of evidence according to the Oxford Centre for Evidence-Based Medicine 2011 guidelines, and the quality of evidence according to the Grading of Recommendations Assessment, Development and Evaluation system. Although sparse data suggest that ART treatment can influence visual function and ocular morphology in women who have undergone ART treatment and children born as a result of ART treatment, the available evidence is inconclusive given its low level and quality. More high-quality research is needed to assess the potential interaction between ART treatment and the eye.

Modified Vitrectomy Technique for Phakic Rhegmatogenous Retinal Detachment with Intermediate Break.

PURPOSE: To evaluate the effects of a modification of the traditional 25-gauge pars plana vitrectomy technique in the treatment of uncomplicated macula-on rhegmatogenous retinal detachment (RRD) with intermediate retinal break(s) and marked vitreous traction in the phakic eye. METHODS: Prospective, noncomparative, and interventional case series. All consecutive phakic eyes with primary uncomplicated macula-on RRD with intermediate retinal break(s) and marked vitreous traction, with at least 1 year of postoperative follow-up, were enrolled. In all eyes, "localized 25-gauge vitrectomy" under air infusion with localized removal of the vitreous surrounding the retinal break(s), in association with laser photocoagulation and air tamponade, was performed. The primary end point was the rate of primary retinal attachment. Secondary end points were cataract progression and assessed by digital Scheimpflug lens photography (mean change of nuclear density units) and the rate of complications. RESULTS: Thirty-two phakic eyes were included in the final analysis. At 12 months, the primary outcome of anatomical success was achieved in 94% of eyes. The mean nuclear density units did not change significantly at any time point during the follow-up. After localized vitrectomy, one eye developed an epiretinal membrane, and one eye developed cystoid macular edema; no other significant complications were reported. CONCLUSIONS: "Localized vitrectomy" has a high anatomical success rate in phakic eyes with primary uncomplicated macula-on RRD with intermediate retinal break(s) and marked vitreous traction, without causing progression of cataract.

Morphology of the optic nerve head in glaucomatous eyes with visual field defects in superior or inferior hemifield.

PURPOSE: To evaluate the morphology of optic nerve head (ONH) and border tissue (BT) of Elschnig in glaucomatous eyes with visual field defects in superior or inferior hemifield. METHODS: In a case-control study, we included 25 patients with superior arcuate scotoma, 25 patients with inferior arcuate scotoma, and 25 healthy controls. They received visual field testing, measurement of peripapillary retinal nerve fiber layer (RNFL) thickness, and ONH examination in a radial pattern with spectral-domain optical coherence tomography. In each ONH scan, the length of Bruch membrane opening (BMO) and BT were measured. Pattern deviation of 6 areas of the visual field and RNFL thickness in corresponding sectors was calculated. RESULTS: Mean BMO length did not differ between groups. Compared with controls, glaucomatous eyes with superior scotoma had a greater BT length in inferior sectors (p<0.001), and eyes with inferior scotoma had a greater BT length in superotemporal sectors (p = 0.006). In both groups, a significant correlation was found between BT length and pattern deviation and RNFL thickness of corresponding sectors of superior and inferior hemifields. CONCLUSIONS: In patients with arcuate scotoma in one hemifield, the length of the BT correlates with glaucomatous anatomical and functional damage.

Correction: miRNAs in the vitreous humor of patients affected by idiopathic epiretinal membrane and macular hole.

[This corrects the article DOI: 10.1371/journal.pone.0174297.].

Optic nerve head in central retinal vein occlusion by spectral-domain OCT.

PURPOSE: To evaluate the morphology of optic nerve head by spectral-domain optical coherence tomography (SD-OCT) in patients with unilateral central retinal vein occlusion (CRVO). METHODS: In 39 consecutive patients with unilateral CRVO and 39 healthy controls, morphologic parameters of optic nerve head were assessed in both eyes by Spectralis SD-OCT using a custom radial B-scan pattern. The length of Bruch membrane opening (BMO) was measured in OCT scans, and optic disc diameters (DD) were assessed in infrared fundus photographs. Axial length was determined by IOLMaster. RESULTS: The BMO length was measured in all eyes with CRVO, while DD was not assessed in 9 eyes (27.3%) that had undefined disc margins. Compared to healthy controls (mean BMO length 1,511 ± 79 µm, mean disc diameter 1,521 ± 77 µm), in eyes with CRVO with defined disc margins (n = 28 [71.8%]), no significant difference was found in BMO length and DD (1,473 ± 118 µm and 1,516 ± 104 µm, respectively). Eyes with CRVO with undefined disc margins had lower BMO length (1,289 ± 61 µm [-14.7%], p = 0.001); also, in fellow eyes, these patients had lower BMO length and DD. In all groups, no significant difference was seen between BMO and DD. A correlation was found between axial length and BMO length and disc diameter (both p<0.001). CONCLUSIONS: Most of the eyes with CRVO had normal optic disc diameter, but about 25% of patients with CRVO have reduced optic disc dimensions.

miRNAs in the vitreous humor of patients affected by idiopathic epiretinal membrane and macular hole.

PURPOSE: The aim of the present study was to assess the expression of miRNAs in the Vitreous Humor (VH) of patients with Macular Hole (MH) and Epiretinal Membrane (ERM) compared to a control group. METHODS: In this prospective, comparative study, 2-ml of VH was extracted from the core of the vitreous chamber in consecutive patients who underwent standard vitrectomy for ERM and MH. RNA was extracted and TaqMan® Low Density Arrays (TLDAs) were used to profile the transcriptome of 754 miRNAs. Results were validated by single TaqMan® assays. Finally, we created a biological network of differentially expressed miRNA targets and their nearest neighbors. RESULTS: Overall 10 eyes with MH, 16 eyes with idiopathic ERM and 6 controls were enrolled in the study. Profiling data identified 5 miRNAs differentially expressed in patients affected by MH and ERM with respect to controls. Four were downregulated (miR-19b, miR-24, miR-155, miR-451) and 1 was downregulated (miR-29a); TaqMan® assays of the VH of patients affected by MH and ERM, with respect to controls, showed that the most differentially expressed were miR-19b (FC -9.13, p:<0.00004), mir-24 (FC -7.52, p:<0.004) and miR-142-3p (FC -5.32, p:<0.011). Our network data showed that deregulation of differentially expressed miRNAs induces an alteration of several pathways associated with genes involved in both MH and ERM. CONCLUSION: The present study suggests that disregulation of miR-19b, miR-24 and miR-142-3p, might be related to the alterations that characterize patients affected by MH and ERM.

Intravitreal Steroids for the Prevention of PVR After Surgery for Retinal Detachment.

Proliferative vitreoretinopathy (PVR) can occur in eyes with rhegmatogenous retinal detachment (RRD) or after RRD surgery, and it is the most common cause of failure of this surgery, accounting for about 75% of all primary failures. Complex biological pathways induce PVR development, with growth factors and cytokines from the vitreous and from the serum (as a result of the breakdown of the blood-retinal barrier) stimulating RPE and Muller cells transformation and proliferation, and membrane formation and contraction. Identification of pre-operative risk factors, recognition of the early signs of PVR, use of adequate surgical techniques and of pharmacological therapy can reduce the PRV incidence. Steroids can influence the inflammatory and proliferative components of PVR, by reducing the breakdown of the blood-retinal barrier, and the proliferation of Müller cell and of RPE cells. Some new formulation of intravitreal steroids are promising tool for the prevention of the PVR formation in eyes treated by vitreoretinal surgery.