13-cis-retinoic acid in silicone-fluorosilicone copolymer oil in a rabbit model of proliferative vitreoretinopathy

Vitreous Substitutes as Drug Release Systems

Vitreous substitutes are traditionally used to stabilize the retina after vitrectomy. In recent years, various approaches have been developed for using the vitreous substitute not only as a tamponade but also as a drug release system to tackle ocular diseases. This review provides an overview of the requirements for vitreous substitutes and discusses the current clinically applied as well as novel polymer-based vitreous substitutes as drug delivery systems, including their release mechanisms, efficiencies, challenges, and future perspectives.

Silicone oil in vitreoretinal surgery: indications, complications, new developments and alternative long-term tamponade agents

Silicone oil (SO) has been used as a long-term tamponade agent in the treatment of complicated vitreoretinal diseases for about half a century, during which time many advances in surgical techniques and technologies have been made. This review summarizes the chemical and physical properties of SO, its indications and complications, including particularly emulsification. The mechanisms and risk factors for emulsification are discussed, as well as novel strategies for its effective removal. Finally, the review focuses on new improved formulations of SO, including research into slow-release pharmacological agents within SO and provides an overview of alternatives to SO for the purpose of long-term tamponade that are being developed.

Determining the effect of low-dose isotretinoin on proliferative vitreoretinopathy: the DELIVER trial

PURPOSE

To examine the effect of low-dose, oral isotretinoin in lowering the risk of proliferative vitreoretinopathy (PVR) following rhegmatogenous retinal detachment (RRD) repair.

METHODS

Prospective, open label, dual-cohort study with pathology-matched historical controls. The prospective experimental arms included two cohorts, composed of 51 eyes with recurrent PVR-related RRD and 58 eyes with primary RRD associated with high-risk features for developing PVR. Eyes in the experimental arms received 20 mg of isotretinoin by mouth once daily for 12 weeks starting the day after surgical repair. The primary outcome measure was single surgery anatomical success rate at 3 months following the study surgery.

RESULTS

The single surgery anatomic success rate was 78.4% versus 70.0% (p=0.358) in eyes with recurrent PVR-related retinal detachment exposed to isotretinoin versus historical controls, respectively. In eyes with RRD at high risk for developing PVR, the single surgery success rate was 84.5% versus 61.1% (p=0.005) for eyes exposed to isotretinoin versus historical controls, respectively. For eyes enrolled in the experimental arms, the most common isotretinoin-related side effects were dry skin/mucus membranes in 106 patients (97.2%), abnormal sleep/dreams in 4 patients (3.7%) and fatigue in 3 patients (2.8%).

CONCLUSION

The management and prevention of PVR is challenging and complex. At the dose and duration given in this study, oral istotretinoin may reduce the risk of PVR-associated recurrent retinal detachment in eyes with primary RRD at high risk of developing PVR.

Clinical management of proliferative vitreoretinopathy: an update

BACKGROUND

Proliferative vitreoretinopathy (PVR) remains the most significant obstacle to successful retinal reattachment surgery. Preclinical studies continue to add insights into the complex molecular events leading to PVR development, helping to identify new targets for potential prophylactic or therapeutic agents. This article reviews the recent evidence supporting surgical and medical treatments for PVR.

METHODS

PUBMED was used for literature search. Clinical studies regarding surgical management of PVR from January 1, 2000 to August 1, 2014 were included. Clinical studies regarding medical management of PVR from January 1, 2000 to August 1, 2014 were included if the design of study was a randomized controlled trial.

RESULTS

Many recent studies have evaluated surgical and medical strategies for the treatment and prevention of PVR. Newer vitreoretinal surgery technology (23- and 25-gauge vitrectomy) and tamponade agents (heavy silicone oils) have been studied. Medical therapies evaluated include antiinflammatory agents, low molecular weight heparin, 5-fluorouracil, 13-cis-retinoic acid, and daunorubicin, amongst others.

CONCLUSION

Surgical management with pars plana vitrectomy, with or without scleral buckle or inferior retinectomy, remains an effective treatment for PVR-related detachments. Consensus regarding a preferred surgical strategy remains controversial. Many medical therapies have been studied but fail to demonstrate a statistically significant benefit in clinical trials. Further studies to clarify the efficacy of available and novel treatment options are warranted.

Effect of oral 13-cis-retinoic acid treatment on postoperative clinical outcome of eyes with proliferative vitreoretinopathy

PURPOSE

To determine whether postoperative oral 13-cis-retinoic acid (RA) treatment could improve the outcome of vitreoretinal surgery with silicone oil for the management of proliferative vitreoretinopathy (PVR).

DESIGN

Prospective controlled randomized interventional case series.

METHODS

This study included 35 eyes of 35 patients with primary rhegmatogenous retinal detachment and PVR. All patients underwent surgical repair by similar procedures. The RA group consisted of 16 patients who received 10 mg oral RA twice daily for eight weeks postoperatively. The control group included 19 patients without taking RA. The outcome measure included the rate of retinal attachment, macular pucker formation, ambulatory vision, and RA-related side effects.

RESULTS

At last follow-up (at least one year postoperatively), 15 of 16 eyes (93.8%) in the RA group and 12 of 19 eyes (63.2%) in the control group maintained retinal attachment (P = .047). The rate of macular pucker formation was significantly lower in the RA group (18.8% vs 78.9% in the control group; P = .001). A higher rate of ambulatory vision was achieved in the RA group as compared to the control group (56.3% vs 10.5%; P = .009).

CONCLUSIONS

Postoperative administration with oral moderate dosage of RA for eight weeks appears to maintain retinal attachment, decrease the macular pucker, and improve vision after surgical repair for eyes with PVR.

Efficient approach to acyloxymethyl esters of nalidixic acid and in vitro evaluation as intra-ocular prodrugs

Various alkylcarbonyloxymethyl esters of nalidixic acid ranging from 3 to 15 carbon units in the pro-moiety have been prepared and assessed as potential prodrugs. Their chromatographic retention factors k', silicone oil solubilities and in vitro conversion to nalidixic acid by a commercial esterase were determined together with their in vitro antimicrobial activity and cytotoxicity. The preliminary results suggest that silicone oil may have potential for the intra-ocular delivery of antibacterial compounds. Moreover, the in vitro release rate can be controlled by the lipophilicity of the prodrug.

Effects of Retinoic Acid on Retinal Pigment Epithelium from Excised Membranes from Proliferative Vitreoretinopathy

It has been reported that retinoic acid (RA) may inhibit the growth of RPE and be used in the treatment of proliferative vitreoretinopathy (PVR). However, previous reports in this field have been conflicting. The main reason for these contradictory findings is that different methods for evaluating the effects of RA on RPE from different species have been used. In human specimens, only RPE from the donor eye (stationary) but not RPE from the PVR membrane (already at active proliferation status) have been tested. This study tested the effects of RA on the growth of RPE using a novel in vitro model: RPE from the PVR membranes, which simulates the in vivo situation of PVR patients better than RPE from the donor eyes. This study also used various methods to solve the conflicting results reported previously. We found that both all transretinoic acid (all-RA) and 13-cis-retinoic acid (cis-RA) can promptly (though not completely) inhibit proliferation of RPE (inhibition rate of 89%-90%) over a very wide range of concentrations (10(-9)-10(-5) M) and various lengths of periods (2-12 days) in a dose-dependent and time-dependent manner and without evident cytotoxic effects. Previously reported disadvantages discovered from the study of RPE from donor eyes, e.g., the absence of inhibitory effects on the early passages of cultured cells and inhibition occurring only after long-term treatment, do not present in RPE cells from the PVR membrane. The proliferation of RPE recovered from the inhibition by RA rapidly after the discontinuation of treatment, indicating that a continuous supply of the drug over a long period, i.e., until the breakdown of the blood-retinal barrier has been repaired, is essential for the success of drug treatment of PVR.

Biomaterials used in the posterior segment of the eye

The treatment of posterior segment eye disease and related conditions has improved greatly in recent years with the advent of new therapies, materials and devices. Vitreoretinal conditions, however, remain significant causes of blindness in the developed world. Biomaterials play a major role in the treatment of many of these disorders and the success rate of vitreoretinal surgery, especially in the repair of retinal detachment and related conditions, would increase with the introduction of new and improved materials. This review, which focuses on disorders that feature retinal detachment, briefly describes the anatomy of the eye and the nature and treatment of posterior segment eye disorders. The roles, required properties and suitability of the materials used in vitreoretinal surgery as scleral buckles, tamponade agents or drug delivery devices, are reviewed. Experimental approaches are discussed, along with the methods used for their evaluation, and future directions for biomaterial research in the posterior segment of the eye are considered.