Silicone Oil Tamponade in Rhegmatogenous Retinal Detachment: Functional and Morphological Results

In vivo evaluation of a Nano-enabled therapeutic vitreous substitute for the precise delivery of triamcinolone to the posterior segment of the eye

This study focused on the design of a thermoresponsive, nano-enabled vitreous substitute for the treatment of retinal diseases. Synthesis of a hydrogel composed of hyaluronic acid and a poloxamer blend was undertaken. Poly(D,L-lactide-co-glycolide) acid nanoparticles encapsulating triamcinolone acetonide (TA) were synthesised with a spherical morphology and mean diameter of ~ 153 nm. Hydrogel fabrication and nanoparticle loading within the hydrogel was confirmed via physicochemical analysis. Gelation studies indicated that hydrogels formed in nine minutes and 10 min for the unloaded and nanoparticle-loaded hydrogels, respectively. The hydrogels displayed in situ gel formation properties, and rheometric viscoelastic studies indicated the unloaded and loaded hydrogels to have modulus values similar to those of the natural vitreous at 37 °C. Administration of the hydrogels was possible via 26G needles allowing for clinical application and drug release of triamcinolone acetonide from the nanoparticle-loaded hydrogel, which provided sustained in vitro drug release over nine weeks. The hydrogels displayed minimal swelling, reaching equilibrium swelling within 12 h for the unloaded hydrogel, and eight hours for the nanoparticle-loaded hydrogel. Biodegradation in simulated vitreous humour with lysozyme showed < 20% degradation within nine weeks. Biocompatibility of both unloaded and loaded hydrogels was shown with mouse fibroblast and human retinal pigment epithelium cell lines. Lastly, a pilot in vivo study in a New Zealand White rabbit model displayed minimal toxicity with precise, localised drug release behaviour, and ocular TA levels maintained within the therapeutic window for the 28-day investigation period, which supports the potential applicability of the unloaded and nanoparticle-loaded hydrogels as vitreous substitutes that function as drug delivery systems following vitrectomy surgery.

Single-dose Effect of Intravitreal Dexamethasone Implant for Post-vitrectomy Macular Edema under Silicone Oil

PURPOSE

To investigate the single-dose effect of intravitreal dexamethasone (DEX) implant for patients with post-vitrectomy macular edema (ME) under silicone oil (SO) tamponade.

METHODS

Twelve eyes diagnosed with ME after undergoing pars plana vitrectomy with SO injections were retrospectively reviewed. Each eye received a single intravitreal DEX implant (0.7-mg, Ozurdex; Allergan Inc) injection as treatment for recalcitrant ME. Best-corrected visual acuity (BCVA), central macular thickness (CMT), and intraocular pressure (IOP) were recorded.

RESULTS

Compared with baseline (1.24 ± 0.34), the mean LogMAR BCVA improved at 1 (1.14 ± 0.27), 3 (1.13 ± 0.22), and 6 (1.22 ± 0.30) months without statistical significance. Maximal CMT resolution was observed at 1 month after intravitreal injection. The CMT value improved significantly at 1 (P = .008), 3 (P = .006), and 6 (P = .009) months. IOP did not show significant elevation during follow-up. No serious adverse events were observed.

CONCLUSION

Single-dose treatment of DEX implant may have benefit for recalcitrant post-vitrectomy ME under SO tamponade.

Advances in Polysaccharide- and Synthetic Polymer-Based Vitreous Substitutes

The vitreous humour is a gel-like structure that composes the majority of each eye. It functions to provide passage of light, be a viscoelastic dampener, and hold the retina in place. Vitreous liquefaction causes retinal detachment and retinal tears requiring pars plana vitrectomy for vitreous substitution. An ideal vitreous substitute should display similar mechanical, chemical, and rheological properties to the natural vitreous. Currently used vitreous substitutes such as silicone oil, perfluorocarbon liquids, and gases cannot be used long-term due to adverse effects such as poor retention time, cytotoxicity, and cataract formation. Long-term, experimental vitreous substitutes composed of natural, modified and synthetic polymers are currently being studied. This review discusses current long- and short-term vitreous substitutes and the disadvantages of these that have highlighted the need for an ideal vitreous substitute. The review subsequently focuses specifically on currently used polysaccharide- and synthetic polymer-based vitreous substitutes, which may be modified or functionalised, or employed as the derivative, and discusses experimental vitreous substitutes in these classes. The advantages and challenges associated with the use of polymeric substitutes are discussed. Innovative approaches to vitreous substitution, namely a novel foldable capsular vitreous body, are presented, as well as future perspectives related to the advancement of this field.

Retinal and Corneal Changes Associated with Intraocular Silicone Oil Tamponade

Silicone oils (SO) are used as long-term intraocular tamponades and have an irreplaceable role in vitreoretinal surgery. They can, however, be associated with multiple and potentially severe complications, involving different ocular tissues, in particular retina and cornea. Recent advances in ophthalmic imaging have allowed the precise characterization of retinal and corneal microstructural changes, at a subclinical level. This detailed analysis of SO-related retinal and corneal changes has improved our understanding of their pathogenesis and offer the potential for optimized monitoring and management of patients with SO-filled eyes. This review aims to provide clinicians and ophthalmic scientists with an updated and comprehensive overview of the corneal and retinal changes associated with SO tamponade.

Longitudinal evaluation of retinal thickness and OCTA parameters before and following silicone oil removal in eyes with macula-on and macula-off retinal detachments

BACKGROUND

To investigate the longitudinal retinal vascular and structural alterations by using OCTA following successful repair of retinal detachment (RD) by using silicone oil (SO) endotamponade.

METHODS

A prospective cohort study was performed on 24 eyes of 24 subjects; 17 of them with macula-off and seven with macula-on RD. At least four OCTA scans were generated for each study eye; two before and two after SO removal (SOR). At each session, retinal thickness (RT), vascular density (VD) in the superficial (SCP) and deep capillary plexuses (DCP) and foveal avascular zone(FAZ) size were measured within the fovea, parafovea and whole macular image. The changes in repeated measures of the same parameters especially before and after SOR were performed and compared within macula-on and macula-off groups and between fellow eyes.

RESULTS

"In the macula-off eyes, RT measurements within the whole macula, fovea and parafovea reduced as compared with their fellow eyes(p < 0.0001, p = 0.001 and p < 0.0001, respectively) and did not improve after SOR. Additionally, all of the whole macular, foveal, and parafoveal VD measurements at SCP and foveal VD at DCP were less than their fellow eyes after SOR (p = 0.026, p = 0.023 p = 0.026, and p = 0.002, respectively). In macula-on eyes, RT measurements decreased within the parafovea and whole macular area before SOR (p = 0.018 and p = 0.011, respectively) but improved after SOR. Also, VD measurements did not change during follow-up and were not statistically different than their fellow eyes (p > 0.05). FAZ enlargement was found in eyes with macular-off RD after SOR, whereas it was not observed with macular-on RD (p = 0.038and p = 0.237, respectively).

CONCLUSIONS

Treatment of macula-off RD with SO tamponade has been associated with vascular retinal abnormalities which did not improve following SOR. On the contrary, successful treatment of RD with SO tamponade in macula-on eyes VD measurements of SCP and DCP were not statistically different than their fellow eyes.

Effect of Duration of Silicone Oil Tamponade on Retinal Structure after Rhegmatogenous Retinal Detachment Surgery

PURPOSE

The aim of the study was to investigate the effect of tamponade duration on retinal changes induced by silicone oil (SO) in patients who underwent successful rhegmatogenous retinal detachment (RRD) surgery.

METHODS

Retrospective comparative case series of 68 patients who underwent SO tamponade for RRD. Patients were divided into 2 groups based on timing of SO removal: <6 months (group 1, n = 34) versus ≥6 months (group 2, n = 34). The main outcome measure was the change in central macular, inner, and outer retinal layer thickness (CMT, IRLT, and ORLT) before and after SO removal (SOR).

RESULTS

The median tamponade duration was 4 [Clin Ophthalmol. 2016;10:471-6, Zhonghua Yan Ke Za Zhi. 1997 Jan;33(1):39-41] months in group 1 and 8 [Arch Ophthalmol. 1994 Jun;112(6):778-85, Retina. 2004 Dec;24(6):871-7] months in group 2 (p < 0.001). The mean CMT significantly increased from 245.3 ± 22.2 μm and 238.8 ± 41.6 μm under SO to 281.3 ± 60.2 μm and 259.0 ± 43.5 μm after SOR in group 1 (p = 0.009) and in group 2 (p = 0.007), respectively. Automated segmentation measurement revealed a significant increase in mean IRLT (p = 0.014 and p = 0.013) but no change in mean ORLT (p = 0.080 and p = 0.257) in both groups. After adjustment, there was no difference between the 2 groups in terms of mean final CMT, IRLT, and ORLT and mean retinal thickness changes after SOR. There was also no correlation between the tamponade duration and macular microstructural changes or visual recovery.

CONCLUSION

SO tamponade causes a thinning of all retinal layers, mainly affecting the inner retinal layer. However, these changes resolved following SO extraction and were not affected by longer tamponade duration.

Evaluation of the Effects of Silicone Oil on the Macula with Optical Coherence Tomography in Patients with Rhegmatogenous Retinal Detachment

Objectives:

The effects of silicone endotamponade duration on the macula were evaluated in patients with rhegmatogenous retinal detachment.

Materials and Methods:

Sixty-five eyes of 65 cases with rhegmatogenous retinal detachment that underwent pars plana vitrectomy and silicone endotamponade were included in the study. All cases were classified in three groups according to duration of silicone tamponade: ≤3 months, 3-6 months, and ≥6 months. All cases were evaluated at 1 week, 1 month, and 3 months after silicone injection, just before and at 1 month after silicone removal in terms of intraretinal pathologies in the macula by using spectral-domain optical coherence tomography (SD-OCT).

Results:

Sixteen (26.6%) of the patients were female and 49 (75.4%) were male. The mean age of the patients was 58.1±12.1 years (18-82); the mean follow-up time was 12.4±4 months (6-20). The mean duration of silicone tamponade was 6.7±2.3 months (2-12). In 26.6% of patients with ellipsoid zone/outer limiting membrane defect, a statistically significant improvement in reflectivity was detected after silicone oil removal (p=0.016). There was a significant increase in central foveal thickness after silicone removal in eyes with duration of silicone more than 3 months (p=0.003 for 3-6 months, p=0.006 for ≥6 months). The prevalence of cystoid macular edema before and after silicone removal was also significantly higher in the eyes with silicone duration of 6 months or longer (p<0.001).

Conclusion:

In eyes with silicone endotamponade, structural changes in the macula may differ according to the duration of silicone oil in the eye.

Peripapillary Vessel Density in Eyes with Rhegmatogenous Retinal Detachment after Pars Plana Vitrectomy

Purpose

To investigate the vascular density of the optic nerve head (ONH) and macula using optical coherence tomography angiography (OCTA) in patients undergoing vitrectomy for rhegmatogenous retinal detachment (RRD) and to evaluate associations with visual outcomes.

Methods

Patients with RRD, successfully treated with a pars plana vitrectomy (PPV) and a minimum three-month follow-up were included in this study. The vessel density (VD) of the ONH and peripapillary regions, foveal avascular zone (FAZ), foveal flow density (FFD), and parafoveal flow density (PFD) were evaluated using OCTA and compared to the fellow eye. Multivariate linear regression analysis was performed to determine correlations with visual outcomes.

Results

Thirty-one patients with macula-off RRD were included in the study. Compared with the fellow eyes, eyes after RRD surgery had a lower peripapillary VD (P < 0.01). No significant difference in superficial and deep FFD, PFD, and FAZ area was found compared to the fellow eyes. Postoperative peripapillary VD and baseline BCVA were significantly associated with BCVA three months after PPV (P < 0.05).

Conclusion

Rhegmatogenous retinal detachment eyes successfully treated with PPV had lower peripapillary vessel density than fellow healthy eyes. Postoperative BCVA was related to postoperative peripapillary VD.

Effect on rabbits' intraocular structure by cross-linked hyaluronic formations as vitreous substitute

AIM

To develop a new material for retina filling and to investigate its effect on intraocular structure and histocompatibility in rabbit eyes.

METHODS

The polymer-derived hyaluronic acid (HA) was formed by UV light cross-linked with N-vinyl-pyrrolidone. Vitrectomy was performed in the rabbits, and then cross-linked HA hydrogels at different concentrations were injected. Intraocular pressure measurements, cornea check-up, and B-ultrasound examination were performed during the follow-up period. After six weeks' follow-up, the rabbits were sacrificed, and both eyes were removed for hematoxylin-eosin (HE) staining, and the polymer materials were observed under electron microscopy.

RESULTS

The particle size of the cross-linked HA hydrogels was mainly around at 100 nm. After vitrectomy and injection into vitreous cavity optical coherence tomography showed that the polymeric material HA had no significant effect on the overall thickness of the retina. The intraocular pressure returned to the normal level gradually at week 4. B-ultrasound results revealed that there is no significant change in the eye tissue given to HA material. The pathological and transmission electron microscopy results showed no obvious pathological change in the primary cells and rod cells under the retina tissue.

CONCLUSION

HA-based cross-linked biopolymers has good biocompatibility in rabbit eyes, showing a promising potential as vitreous substitutes.