Electro-oculographic findings after 360 degrees retinotomy and macular translocation for subfoveal choroidal neovascularisation in age-related macular degeneration

Macular translocation for neovascular age-related macular degeneration

BACKGROUND

Macular translocation has been proposed by vitreoretinal surgeons to displace the neuroretinal tissue onto healthy retinal pigment epithelium and choroid when the macula has been invaded by subretinal neovascularisation.

OBJECTIVES

This review aims at assessing the effectiveness of macular translocation for preserving or improving vision in patients with neovascular age-related macular degeneration (AMD).

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE and Caribbean Literature on Health Sciences (LILACS). There were no language or date restrictions in the search for trials.The electronic databases were last searched on 21 July 2008.

SELECTION CRITERIA

We included randomised or quasi randomised controlled trials comparing macular translocation with any other treatment or observation.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data. The risk ratio (RR) of visual loss and visual gain was estimated at one year after treatment.

MAIN RESULTS

Only one small unblinded study on 50 people compared full macular translocation with photodynamic therapy (PDT) in AMD patients with predominantly classic subfoveal choroidal neovascularisation (CNV). At the last examination, performed in most of the cases after one year, there was no difference in the rate of visual loss of 3 or more lines (translocation versus PDT: RR 0.56, 95% confidence interval (CI) 0.22 to 1.43), as well as in the mean change of contrast sensitivity (1 letter favouring translocation; 95% CI -3.51 to 5.51) and the rate of recurrence of CNV (translocation versus PDT: RR 1.56, 95% CI 0.83 to 2.91). Other outcomes significantly favoured translocation, such as the gain of 3 or more ETDRS lines (RR 21, 95% CI 1.30 to 340.02), the mean change of visual acuity (mean difference (MD) 14.60, 95% CI 5.39 to 23.81) and the mean change of near visual acuity score (MD 17.80, 95% CI 3.98 to 31.62) which is obtained with an algorithm. Serious complications reported after macular translocation were retinal detachment in 6/25 patients and diplopia requiring prismatic correction in 5/25 patients.

AUTHORS' CONCLUSIONS

There is insufficient evidence from randomised controlled trials on the effectiveness of macular translocation, which is also not free of important risks. Furthermore, this technique is difficult to perform and a long surgical training is required. Future studies might include patients with small neovascular lesions that failed to respond to current pharmacological therapies and are willing to accept the risks associated with surgery to try to improve visual acuity.

A review of in vivo animal studies in retinal prosthesis research

BACKGROUND

The development of a functional retinal prosthesis for acquired blindness is a great challenge. Rapid progress in the field over the last 15 years would not have been possible without extensive animal experimentation pertaining to device design and fabrication, biocompatibility, stimulation parameters and functional responses. This paper presents an overview of in vivo animal research related to retinal prosthetics, and aims to summarize the relevant studies.

METHODS

A Pubmed search of the English language literature was performed. The key search terms were: retinal implant, retinal prosthesis, artificial vision, rat, rabbit, cat, dog, sheep, pig, minipig. In addition a manual search was performed based on references quoted in the articles retrieved through Pubmed.

RESULTS

We identified 50 articles relevant to in vivo animal experimentation directly related to the development of a retinal implant. The highest number of publications related to the cat (n = 18).

CONCLUSION

The contribution of animal models to the development of retinal prosthetic devices has been enormous, and has led to human feasibility studies. Grey areas remain regarding long-term tissue-implant interactions, biomaterials, prosthesis design and neural adaptation. Animals will continue to play a key role in this rapidly evolving field.

Polydimethylsiloxane as a substrate for retinal pigment epithelial cell growth

Retinal pigment epithelial (RPE) cell transplantation represents potential treatment for age-related macular degeneration (AMD). Because delivery of isolated cells can cause serious complications, it is necessary to develop a suitable transplant membrane that could support an intact functioning RPE monolayer. Polydimethylsiloxane (PDMS) possesses the physical properties required for a transplanting device and is widely used clinically. We have investigated the use of PDMS as a potential surface for the growth of healthy RPE monolayers. PDMS discs were surface modified by air and ammonia gas plasma treatments. Dynamic contact angles were measured to determine the changes in wettability. Human ARPE-19 cells were seeded onto untreated and treated samples. Cell number, morphology and monolayer formation, cytotoxicity, and phagocytosis of photoreceptor outer segments (POS) were assessed at set time-points. Air plasma treatment increased the wettability of PDMS. This significantly enhanced cell growth, reaching confluence by day 7. Immunofluorescence revealed well-defined actin staining, monolayer formation, and high cell viability on air plasma treated and untreated surfaces, and to a lesser extent, on ammonia plasma treated. Furthermore, RPE monolayers were able to demonstrate phagocytosis of POS in a time-dependent manner similar to control. PDMS can support an intact functional monolayer of healthy differentiated RPE cells.

The end of submacular surgery for age-related macular degeneration? A meta-analysis

BACKGROUND

The aim of this meta-analysis was to summarize and to discuss the results of the four main submacular surgical procedures for age-related macular degeneration (AMD) as reported in the literature through 2004 and to compare them to the Submacular Surgery Trials (SST) data.

METHODS

The existing data in the literature on submacular surgery for AMD from 1992 to 2004 were evaluated. The main outcomes were proportion of patients with two or more lines of improvement in visual acuity (VA) and proportion with two or more lines of deterioration in VA after surgery.

RESULTS

Eighty-eight studies including 1,915 cases met the inclusion criteria. Estimates for the treatment outcome within the four groups of treatment based on a logistic regression model gave comparable results for removal of choroidal neovascularization (CNV) (improvement of VA 28%, deterioration of VA 25%), macular translocation (improvement of VA 31%, deterioration of VA 27%), and for transplantation of pigment epithelium (improvement of VA 22%, deterioration of VA 21%). Estimates for removal of subretinal hemorrhage were significantly different (improvement of VA 62%, deterioration of VA 13%).

CONCLUSIONS

Selected case series showed superior results of VA compared to the SST. The question of whether this is due to selection bias that seems inevitable when dealing with medium-sized nonrandomized case series or due to better results in single centers cannot be answered. In our opinion there still seem to be indications for submacular surgery such as in patients with AMD with low preoperative VA due to large hemorrhagic or fibrotic membranes or nonresponders to photodynamic therapy (PDT).

The electro-oculogram

The retinal pigment epithelium (RPE) lying distal to the retina regulates the extracellular environment and provides metabolic support to the outer retina. RPE abnormalities are closely associated with retinal death and it has been claimed several of the most important diseases causing blindness are degenerations of the RPE. Therefore, the study of the RPE is important in Ophthalmology. Although visualisation of the RPE is part of clinical investigations, there are a limited number of methods which have been used to investigate RPE function. One of the most important is a study of the current generated by the RPE. In this it is similar to other secretory epithelia. The RPE current is large and varies as retinal activity alters. It is also affected by drugs and disease. The RPE currents can be studied in cell culture, in animal experimentation but also in clinical situations. The object of this review is to summarise this work, to relate it to the molecular membrane mechanisms of the RPE and to possible mechanisms of disease states.