Anthony Kwan

Subretinal transplantation of genetically modified human cell lines attenuates loss of visual function in dystrophic rats

Royal College of Surgeons rats are genetically predisposed to undergo significant visual loss caused by a primary dysfunction of retinal pigment epithelial (RPE) cells. By using this model, we have examined the efficacy of subretinal transplantation of two independent human RPE cell lines each exhibiting genetic modifications that confer long-term stability in vitro. The two cell lines, a spontaneously derived cell line (ARPE19) and an extensively characterized genetically engineered human RPE cell line (h1RPE7), which expresses SV40 large T (tumor) antigen, were evaluated separately. Both lines result in a significant preservation of visual function as assessed by either behavioral or physiological techniques. This attenuation of visual loss correlates with photoreceptor survival and the presence of donor cells in the areas of rescued photoreceptors at 5 months postgrafting (6 months of age). These results demonstrate the potential of genetically modified human RPE cells for ultimate application in therapeutic transplantation strategies for retinal degenerative diseases caused by RPE dysfunction.

Cell transplantation as a treatment for retinal disease.

It has been shown that photoreceptor degeneration can be limited in experimental animals by transplantation of fresh RPE to the subretinal space. There is also evidence that retinal cell transplants can be used to reconstruct retinal circuitry in dystrophic animals. Here we describe and review recent developments that highlight the necessary steps that should be taken prior to embarking on clinical trials in humans.

Photoreceptor layer reconstruction in a rodent model of retinal degeneration

We have examined the potential of retinal cell transplantation to dystrophic retinal degeneration mice as a way of replacing photoreceptors lost because of an intrinsic genetic defect. Early postnatal retinae which had been gently dissociated survived for at least 6 weeks after transplantation to the subretinal space. Over a significant area of distribution, transplanted cells formed outer segments which lay in close apposition to the host retinal pigment epithelial cell layer. The grafts integrated with the remaining host retina, sufficient at least to mediate a simple light-dark preference. A new synaptic layer was seen at the graft-host interface, which contained substantial numbers of photoreceptor synapses. This and the fact that the behavior could be elicited at low luminance levels argue for functional circuit reconstruction between grafted cells and host retina.

Fluorescein angiography and adverse drug reactions revisited: the Lions Eye experience

Background:  The last major survey of adverse reactions to intravenous fluorescein angiography was performed more than 20 years ago. There have been two recent fatalities involving intravenous fluorescein in Australia. It is important to review the current incidence of adverse reactions and latest literature on the pathogenesis, prophylaxis and alternatives to intravenous fluorescein angiography.

Chondroitin Sulfate Proteoglycans and Microglia Prevent Migration and Integration of Grafted Müller Stem Cells into Degenerating Retina

At present, there are severe limitations to the successful migration and integration of stem cells transplanted into the degenerated retina to restore visual function. This study investigated the potential role of chondroitin sulfate proteoglycans (CSPGs) and microglia in the migration of human Müller glia with neural stem cell characteristics following subretinal injection into the Lister hooded (LH) and Royal College of Surgeons (RCS) rat retinae. Neonate LH rat retina showed minimal baseline microglial accumulation (CD68‐positive cells) that increased significantly 2 weeks after transplantation (p < .001), particularly in the ganglion cell layer (GCL) and inner plexiform layer. In contrast, nontransplanted 5‐week‐old RCS rat retina showed considerable baseline microglial accumulation in the outer nuclear layer (ONL) and photoreceptor outer segment debris zone (DZ) that further increased (p < .05) throughout the retina 2 weeks after transplantation. Marked deposition of the N‐terminal fragment of CSPGs, as well as neurocan and versican, was observed in the DZ of 5‐week‐old RCS rat retinae, which contrasted with the limited expression of these proteins in the GCL of the adult and neonate LH rat retinae. Staining for CSPGs and CD68 revealed colocalization of these two molecules in cells infiltrating the ONL and DZ of the degenerating RCS rat retina. Enhanced immune suppression with oral prednisolone and intraperitoneal injections of indomethacin caused a reduction in the number of microglia but did not facilitate Müller stem cell migration. However, injection of cells with chondroitinase ABC combined with enhanced immune suppression caused a dramatic increase in the migration of Müller stem cells into all the retinal cell layers. These observations suggest that both microglia and CSPGs constitute a barrier for stem cell migration following transplantation into experimental models of retinal degeneration and that control of matrix deposition and the innate microglial response to neural retina degeneration may need to be addressed when translating cell‐based therapies to treat human retinal disease.

Predicting visual outcome following retinectomy for retinal detachment

Aim: To evaluate outcome following retinectomy surgery and to identify factors that predict visual outcome. Methods: This was a retrospective uncontrolled interventional case-series of patients who underwent retinectomy surgery at Moorfields Eye Hospital (London, UK) during a 2-year period. We recorded peri-operative factors with the potential to influence functional outcome including aetiology of retinal detachment; type of ocular trauma; preoperative visual acuity and intraocular pressure; grade of PVR; extent and position of retinectomy; peri-operative complications; tamponade agent and prophylactic 360° laser retinopexy. Results: The authors identified 145 patients who underwent retinectomy surgery. After a mean follow-up period of 23.2 months (6–58 months) 16% of eyes had visual acuity of 20/60 or better, 33% had visual acuity of between 20/60 and 20/400, and 51% had visual acuity less than 20/400. Visual acuity was improved or stable in 76% of eyes and the rate of complete retinal reattachment was 68%. For each stepwise increase in the grade of PVR there was an approximately 15% increased risk of final visual acuity of less than 20/40. The use of additional 360 degree prophylactic laser retinopexy prior to removal of silicone oil was associated with a higher rate of final retinal reattachment. Conclusions: This study provides important information to help surgeons inform and counsel their patients about visual prognosis following retinectomy surgery. Furthermore, the study demonstrates that the aetiology of retinal detachment, the stage of PVR and the use of 360° laser retinopexy have significant predictive value for visual outcome. Summary: Retinectomy is a valuable technique in the management of complex retinal detachment but is associated with a significant risk of retinal redetachment and poor visual outcome. In this large study, we identified that the aetiology of retinal detachment, the stage of proliferative vitreoretinopathy and the use of 360° prophylactic laser retinopexy are predictive of functional outcome.

Lacrimal drainage surgery in Wegener's granulomatosis

AIM To examine the results of open lacrimal surgery in patients with Wegeners granulomatosis. METHODS A retrospective review of patients with Wegeners granulomatosis who underwent lacrimal surgery over a 17 year period. RESULTS 11 patients were identified and a total of 14 primary dacryocystorhinostomies (DCR) and one revisional DCR were performed; symptomatic relief was achieved in 13/14 operations and one patient required revisional surgery for persistent symptoms. There were no intraoperative and few postoperative complications. CONCLUSIONS In contrast with some previous reports, open DCR appears to be a safe procedure and it is recommended as a treatment for lacrimal obstruction in patients with Wegeners granulomatosis, but an increase of perioperative immunosuppression is recommended in certain cases.

Ocular motility disturbances after surgery for retinal detachment

PURPOSE Relatively little has been published on the management of motility problems after surgery for retinal detachment. We report a large series with the aim of describing clinical features, management, and outcome. METHODS The charts of 68 of 86 consecutive patients referred to one of us between 1989 and 1995 were retrieved and analyzed. Sixty-two had unilateral and 6 bilateral surgery for retinal detachment. In 45 cases the macula was detached at surgery. The visual acuity of the affected eyes ranged from hand motions to 6/6. Sensory testing suggested potential binocular function in 39.7%. Fifty-nine patients had combined vertical and horizontal strabismus, 8 horizontal alone, and 1 vertical only. The average vertical deviation measured 10.2 PD and the average horizontal 19 PD. RESULTS Twelve patients underwent strabismus surgery, 26 were treated with botulinum toxin, 21 were managed conservatively with prisms or occlusion, and 8 refused or did not require treatment. Forty-seven percent of the group regained binocularity (20.5% cured with surgery or botulinum toxin, 26.5% controlled with prisms or intermittent injection with botulinum toxin). A total of 20.7% gained improvement in appearance, 19.1% were managed with permanent occlusion, and 13.2% either refused or did not require treatment. CONCLUSION Macula off retinal detachment, poor visual acuity plus or minus distortion, and multiple procedures for retinal reattachment are associated with a poor prognosis for restoration of binocular vision and a good outcome. In our hands, botulinum toxin treatment is the method of choice, with surgery used in selected cases.

A pilot randomised controlled trial comparing the post-operative pain experience following vitrectomy with a 20-gauge system and the 25-gauge transconjunctival system.

Aims: To compare post-operative pain following 25-gauge (25G) and 20-gauge (20G) vitrectomy in the first week following surgery. Methods: The study was a pilot randomised controlled trial with patients masked to the treatment allocation. Post-operative pain was assessed using both a visual scale and verbal pain scores for 1 week following surgery. Additional data collected included intraocular pressure (IOP), time taken to perform the surgical procedure, per-operative and post-operative complications, and dropout rates. Results: Forty patients were recruited for the study: 21 randomised to 20G vitrectomy and 19 to 25G. In the first 12 h following surgery, presence of significant post-operative pain (defined as >1 cm on a visual analogue scale) was similar in both 20G (50%) and 25G (53%) patients. In the first week following surgery, 38 of the 527 scores (7.2%) were >1 (median 2.1, IQR 1.3–3) cm; however, there was evidence that “significant pain” was experienced more commonly in the 20G group. There was no statistical difference in the time taken to complete the surgical procedure, although in the 25G group the time from first incision to the start of vitrectomy was significantly shorter (p = 0.043) and in the 20G group the time taken to complete the vitrectomy was less (p = 0.047). Post-operative hypotony (IOP <6 mmHg) was observed in 25% of patients in the 25G group. No patients required additional surgery for hypotony. Conclusion: There was evidence that 25G resulted in less patient discomfort. However, pain was not a prominent feature in either group. We failed to find a significant advantage in 25G for patients or surgeons.

A new technique of combined retinal and choroidal biopsy

Aims: To evaluate a new technique in large retinal and choroidal biopsies in patients with uveitis of unknown aetiology and chorioretinal lesions or infiltrate. Methods: Retrospective, non-comparative, consecutive interventional case series. Patients were identified from the computerised patient database and from histopathology records. Results: A total of nine patients were included in the study. The commonest indication of biopsy was panuveitis of unknown aetiology. Positive histological diagnoses from the chorioretinal biopsies were made in five cases (55.6%). Complications included vitreous haemorrhages and one case of retinal detachment. Conclusion: The technique of large chorioretinal biopsy described appears to be safe. It produced good amounts of chorioretinal tissue for histopathological analysis. Positive histology results were seen in the majority of the sample and especially in those where vitreous biopsy alone proved to be inadequate.