Gilbert, Clare Elizabeth; (1994) Retinal patching: A new approach to the management of selected retinal breaks. Doctoral thesis (M.D), UCL (University College London).

Text Retinal_patching_A_new_approa.pdf Download (26MB)

Abstract

This thesis examines a new approach to the management of retinal breaks, a retinal patching technique, which could be used to repair retinal breaks by restoring retinal continuity. It is envisaged that this technique could be used as a novel treatment for selected cases where retinal reattachment is currently difficult to achieve, and also to avoid some of the complications of established procedures. Potential patching materials (17 adhesives and 26 "substrates", both biological and synthetic materials) were evaluated in vitro, in order to select the most suitable for evaluation in an animal model. Bovine eye cup experiments, tissue culture studies and limited organ culture were undertaken to evaluate the physical properties, toxicity and biocompatibility of the materials. Following these experiments two adhesives (octylcyanoacrylate and Tisseel, a fibrin preparation) and two substrates (PVdF and propylene) were evaluated in vivo. In the animal studies there were three Control Groups (43 rabbits) and two Experimental Groups (37 rabbits). The animal work showed that retinal patching is possible, but difficult. The procedure had to be abandoned in 6 Experimental animals (6/37) compared to 1 Control animal (1/43) because of major operative complications, e.g. dense vitreous haemorrhage (Chi sq test, p=0.028, exact p=0.013). Minor posterior segment operative complications, e.g. inadvertent retinal tears, occurred significantly more often in experimental animals (12/31) compared to controls (4/42)(Chi sq, p=0.003). When octylcyanoacrylate was used to secure the substrate (Experimental Group A) 5/16 (31.3%) eyes developed new tears at the edge of the patch after air/fluid exchange. All developed localised retinal necrosis in the vicinity of the adhesive in the immediate postoperative period. Atrophic retinal holes formed in necrotic retina in 4/10 (40%) animals followed for one week. All eyes with iatrogenic or atrophic retinal breaks subsequently developed retinal detachment. At the end of the period of study (4 weeks) only 2/7 eyes had adherent patches and flat retinas. Generalised epiretinal membranes (ERMs) had developed in 3 of the animals with detached retinas. When the substrate was applied with Tisseel (Experimental Group B, 15 animals) air/fluid exchange caused fewer problems. However, the fibrin adhesive lysed in all eyes within 14 days, and the patch separated in several animals. Epiretinal membrane formation was a notable feature of patching with Tisseel. At two weeks 3/8 eyes had developed focal ERMs and a further 3 had generalised ERMs. At the end of the study period all eyes had extensive, generalised ERMs (8/8) often causing marked vitreoretinal traction. Retinal detachment was present in 5/10 eyes examined at 1 week and developed in 3 more eyes during follow up. Using stratified analysis retinal detachment of any extent and generalised epiretinal membrane formation occurred significantly more often in Experimental Groups animals compared to Controls. Retinal detachment of any extent and generalised epiretinal membrane formation occurred more frequently in Experiment Group B eyes compared to Group A, but this did not reach significance. Histological examination confirmed the presence of early coagulative necrosis and late retinal atrophy in retina beneath and adjacent to patches made with octyl-cyanoacrylate. The underlying retinal pigment epithelium was also abnormal, with vacuolation and separation of cells from Bruch's membrane. Intense inflammatory infiltration of the choroid and ciliary body characterised eyes where Tisseel was used as the adhesive. This study has shown that retinal patching is technically possible, but is associated with operative and postoperative complications. Difficulties in delivering, manipulating and applying the patching materials were responsible for some of the complications. Others occurred as a result of toxic and biological effects of the adhesives selected for study. The rabbit was not an ideal model, as the ocular tissues are thin and the eye responds vigorously to insult. Some of the complications may have been less pronounced if another species had been used. Retinal patching remains a compelling attractive means of managing selected retinal breaks, at least in theory, but involves many practical difficulties which could not be overcome within the constraints of this study.

Download activity - last month

Export as XMLCSVJSON

Download activity - last 12 months

Export as XMLCSVJSON

Downloads by country - last 12 months

Export as CSVXMLJSON

Archive Staff Only

View Item