Biological Characteristics of Subsilicone Oil Fluid and Differences With Other Ocular Humors

Vision loss associated with silicone oil endotamponade in vitreoretinal surgery - a review

PURPOSE

To clarify the definition, prevalence and classification of different types of unexplained vision loss associated with silicone oil (SO) endotamponades (SO in situ (SOIS) or after removal of SO (ROSO)) in vitreoretinal surgery and identifying the most specific clinical findings and suggesting possible causes.

METHODS

Review of the literature regarding randomized clinical trials (RCTs), retrospective case-control, cohort studies and case series evaluating the risk of using SO, published in English between 1994 and 2023, conducting a computer-based search of the following databases: PubMed, Web of Science, Scopus and Embase. The search was supplemented using the Medline option 'Related Articles' and consulting review articles on the topic.

RESULTS

Findings from reported clinical examinations in SOIS and ROSO are analyzed and finally different theories regarding the underlying pathophysiology are described. From the clinical point of view, findings have been found in OCT, OCTA, microperimetry and electrophysiological studies. Other clearly identifiable causes of vision loss related to the use of SO are listed and commented as differential diagnosis. Finally, the different physiopathological theories of the two types of causes of unexplained vision have been analyzed.

CONCLUSION

Unexpected vision loss under or after SO tamponade (SOIS and ROSO) is a significant concern which is probably underestimated because it is not a clearly defined and known entity. The most frequently described changes were in the ganglion cell complex but this unexpected vision loss remains a serious and unexplained concern for vitreoretinal surgeons and should be identified by clinicians, addressed by manufacturers and reported to Health Authorities as a serious incident according to the new regulation.

Retinal ferroptosis as a critical mechanism for the induction of retinochoroiditis during ocular toxoplasmosis

Toxoplasmosis is a major infectious disease, affecting approximately one-third of the world's population; its main clinical manifestation, ocular toxoplasmosis (OT), is a severe sight-threatening disease. Nevertheless, the diagnosis of OT is based on clinical findings, which needs improvement, even with biochemical tests, such as polymerase chain reaction and antibody detections. Furthermore, the efficacy of OT-targeted treatment is limited; thus, additional measures for diagnosis and treatments are needed. Here, we for the first time report a significantly reduced iron concentration in the vitreous humor (VH) of human patients infected with OT. To obtain further insights into molecular mechanisms, we established a mouse model of T. gondii infection, in which intravitreally injected tracer 57Fe, was accumulated in the neurosensory retina. T. gondii-infected eyes showed increased lipid peroxidation, reduction of glutathione peroxidase-4 expression and mitochondrial deformity in the photoreceptor as cristae loss. These findings strongly suggest the involvement of ferroptotic process in the photoreceptor of OT. In addition, deferiprone, an FDA-approved iron chelator, reduced the iron uptake but also ameliorated toxoplasma-induced retinochoroiditis by reducing retinal inflammation. In conclusion, the iron levels in the VH could serve as diagnostic markers and iron chelators as potential treatments for OT.

Interferon Alpha-2a for the Treatment of Cystoid Macular Edema Secondary to Acute Retinal Necrosis

PURPOSE

To report the results of interferon (IFN) α-2a treatment in patients with cystoid macular edema (CME) secondary to acute retinal necrosis (ARN).

METHODS

We reviewed the records of seven patients (eight eyes) who received IFNα-2a for post-ARN CME. The initial dose of IFNα-2a was 3 MIU/day and it could be tapered down to 3 MIU twice a week. Efficacy was assessed by central macular thickness (CMT) on spectral-domain optical coherence tomography and visual acuity.

RESULTS

Age range of seven patients (four men, three women) was 36-74 years. Mean CMT decreased from 477.9 ± 167.5 μm to 367.3 ± 120.5 μm at first week, and vision improved up to five lines in five eyes. CME relapsed after cessation of IFNα-2a in all and improved following reinstitution of treatment. Treatment was discontinued in one patient because of depression. Three patients electively discontinued treatment due to poor tolerability or lack of functional improvement.

CONCLUSION

IFNα-2a is an effective therapeutic option for post-ARN CME, though side effects such as fatigue, elevated liver enzymes, neutropenia, and depression may limit tolerability. Lower initial doses may be a better tolerated.

Changes in aqueous and vitreous inflammatory cytokine levels in proliferative diabetic retinopathy: a systematic review and meta-analysis

BACKGROUND

Diabetic retinopathy is a major complication of diabetes mellitus, where in its most advanced form ischemic changes lead to the development of retinal neovascularization, termed proliferative diabetic retinopathy (PDR). While the development of PDR is often associated with angiogenic and inflammatory cytokines, studies differ on which cytokines are implicated in disease pathogenesis and on the strength of these associations. We therefore conducted a systematic review and meta-analysis to quantitatively assess the existing body of data on intraocular cytokines as biomarkers in PDR.

METHODS

A comprehensive search of the literature without year limitation was conducted to January 18, 2021, which identified 341 studies assessing vitreous or aqueous cytokine levels in PDR, accounting for 10379 eyes with PDR and 6269 eyes from healthy controls. Effect sizes were calculated as standardized mean differences (SMD) of cytokine concentrations between PDR and control patients.

RESULTS

Concentrations (SMD, 95% confidence interval, and p-value) of aqueous IL-1β, IL-6, IL-8, MCP-1, TNF-α, and VEGF, and vitreous IL-2, IL-4, IL-6, IL-8, angiopoietin-2, eotaxin, erythropoietin, GM-CSF, GRO, HMGB-1, IFN-γ, IGF, IP-10, MCP-1, MIP-1, MMP-9, PDGF-AA, PlGF, sCD40L, SDF-1, sICAM-1, sVEGFR, TIMP, TNF-α, and VEGF were significantly higher in patients with PDR when compared to healthy nondiabetic controls. For all other cytokines no differences, failed sensitivity analyses or insufficient data were found.

CONCLUSIONS

This extensive list of cytokines speaks to the complexity of PDR pathogenesis, and informs future investigations into disease pathogenesis, prognosis, and management.

Status of corneal endothelial cells in the presence of silicone oil in the anterior chamber

To evaluate corneal endothelium damage with silicone oil (SO) presence in the anterior chamber after pars plana vitrectomy. We investigated the medical records of consecutive 54 eyes of 53 patients undergoing SO removal after pars plana vitrectomy with SO tamponade at Saitama Medical Center, Jichi Medical University, Japan. We recorded SO tamponade retention period, anterior chamber SO with gonioscope, area of SO attachment to the corneal endothelium before SO removal surgery, and the lens status. We then retrospectively investigated the correlation between SO presence in the anterior chamber and the decrease rate of corneal endothelial cell (CEC) density during SO tamponade. The average decrease rate of CEC density was 7.6 (0–38.1) %. The correlation between SO tamponade retention period and decrease rate of CEC density was high (p = 0.0001). However, there was no correlation between anterior chamber SO under gonioscope, SO attaching area, and lens status with the decrease rate of CEC density (p = 0.11, p = 0.93, p = 0.16). No correlation was observed between CEC loss and the existence of anterior chamber SO, although CEC decrease rate was relatively high after a long SO tamponade period. These findings suggest that SO presence in the anterior chamber may not directly injure CEC.

Effects of different tamponade materials on macular segmentation after retinal detachment repair

PURPOSE

This study used spectral domain-optical coherence tomography (SD-OCT) to evaluate individual retinal layer thickness in eyes with macula-off rhegmatogenous retinal detachment (RRD) treated with silicone oil (SiO) or gas endotamponades.

STUDY DESIGN

This was a retrospective, interventional, comparative study.

METHODS

The study included 86 eyes of 43 patients who were divided into 3 groups according to endotamponades: SiO, perfluoropropane (C3F8), and sulfur hexafluoride (SF6). The affected eyes were compared with the fellow eyes of the same patient via SD-OCT automated segmentation analysis. Patients with a follow-up of at least 6 months were included in the final analysis. Macular segmentation including the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), retinal pigment epithelium (RPE), inner retinal layers (IRLs), and outer retinal layers (ORLs) was analyzed.

RESULTS

In the SiO group, the mean thickness of each retinal layer including the RNFL, GCL, IPL, ONL, and IRLs within a 1-mm ETDRS subfield of the affected eyes was significantly lower than that of the fellow eyes (P = 0.036, P = 0.028, P = 0.003, P < 0.001, P = 0.013, respectively). There was no significant difference in the C3F8 and SF6 groups (all P > 0.05). The difference between the ONL and IRLs in the SiO-treated eyes differed significantly from that of the gas groups (P = 0.001 and P = 0.045, respectively) The difference in the GCL thickness of the affected eyes and healthy eyes showed a significant correlation with postoperative BCVA changes in the SiO, C3F8, and SF6 groups (P = 0.041, P = 0.048, and P = 0.045, respectively).

CONCLUSION

The findings of our study show that endotamponades used in RRD surgery may have different effects on retinal layers. In addition, SiO may cause undesirable effects on the retinal layers.