Localized RPE Removal with a Novel Instrument Aided by Viscoelastics in Rabbits.

PURPOSE: We developed a surgical method for localized and atraumatic removal of the retinal pigment epithelium (RPE) with a novel instrument. METHODS: Bleb retinal detachments (bRD) were raised with balanced salt solution (BSS) following vitrectomy in 27 rabbits. The RPE was scraped with 3 loop variants (polypropylene [PP], 0.1 mm; PP, 0.06 mm; metal, 0.1 mm) of a custom-made instrument. Stabilization of bRDs with BSS or various concentrations (0.1%-0.5%) of hyaluronic acid (HA) was video analyzed. Perfusion-fixed samples of scraped areas and controls were studied by light and transmission electron microscopy. RESULTS: The bRDs were sufficiently stabilized by ≥0.25% HA. Using the PP 0.1 mm loop with a single forward/backward stroke, an area of ca. 2.5 × 1.5 mm was nearly devoid of RPE, yet did show occasional Bruch's membrane (BM) defects combined with choriocapillaris hemorrhages in 13% of the bRDs. A single scrape with PP 0.06 mm resulted in unsatisfactory RPE denudement, while repeated scraping maneuvers caused more BM defects and hemorrhages. The metal loop resulted in incomplete RPE removal and massive intraoperative subretinal hemorrhages. Histologically, intact photoreceptor outer segments (POS) were observed above the RPE wounds in bRDs. Controls with bRDs alone showed an intact RPE monolayer with microvilli, with few engulfed remains of POS. CONCLUSIONS: Localized removal of RPE in HA stabilized bRD can be achieved by a PP 0.1 mm loop instrument. TRANSLATIONAL RELEVANCE: Removal of degenerated RPE may aid RPE cell replacement strategies.

The first rapid assessment of avoidable blindness (RAAB) in Thailand.

BACKGROUND: The majority of vision loss is preventable or treatable. Population surveys are crucial for planning, implementation, and monitoring policies and interventions to eliminate avoidable blindness and visual impairments. This is the first rapid assessment of avoidable blindness (RAAB) study in Thailand. METHODS: A cross-sectional study of a population in Thailand age 50 years old or over aimed to assess the prevalence and causes of blindness and visual impairments. Using the Thailand National Census 2010 as the sampling frame, a stratified four-stage cluster sampling based on a probability proportional to size was conducted in 176 enumeration areas from 11 provinces. Participants received comprehensive eye examination by ophthalmologists. RESULTS: The age and sex adjusted prevalence of blindness (presenting visual acuity (VA) <20/400), severe visual impairment (VA <20/200 but ≥20/400), and moderate visual impairment (VA <20/70 but ≥20/200) were 0.6% (95% CI: 0.5-0.8), 1.3% (95% CI: 1.0-1.6), 12.6% (95% CI: 10.8-14.5). There was no significant difference among the four regions of Thailand. Cataract was the main cause of vision loss accounted for 69.7% of blindness. Cataract surgical coverage in persons was 95.1% for cut off VA of 20/400. Refractive errors, diabetic retinopathy, glaucoma, and corneal opacities were responsible for 6.0%, 5.1%, 4.0%, and 2.0% of blindness respectively. CONCLUSION: Thailand is on track to achieve the goal of VISION 2020. However, there is still much room for improvement. Policy refinements and innovative interventions are recommended to alleviate blindness and visual impairments especially regarding the backlog of blinding cataract, management of non-communicative, chronic, age-related eye diseases such as glaucoma, age-related macular degeneration, and diabetic retinopathy, prevention of childhood blindness, and establishment of a robust eye health information system.

Human RPE stem cells grown into polarized RPE monolayers on a polyester matrix are maintained after grafting into rabbit subretinal space.

Transplantation of the retinal pigment epithelium (RPE) is being developed as a cell-replacement therapy for age-related macular degeneration. Human embryonic stem cell (hESC) and induced pluripotent stem cell (iPSC)-derived RPE are currently translating toward clinic. We introduce the adult human RPE stem cell (hRPESC) as an alternative RPE source. Polarized monolayers of adult hRPESC-derived RPE grown on polyester (PET) membranes had near-native characteristics. Trephined pieces of RPE monolayers on PET were transplanted subretinally in the rabbit, a large-eyed animal model. After 4 days, retinal edema was observed above the implant, detected by spectral domain optical coherence tomography (SD-OCT) and fundoscopy. At 1 week, retinal atrophy overlying the fetal or adult transplant was observed, remaining stable thereafter. Histology obtained 4 weeks after implantation confirmed a continuous polarized human RPE monolayer on PET. Taken together, the xeno-RPE survived with retained characteristics in the subretinal space. These experiments support that adult hRPESC-derived RPE are a potential source for transplantation therapies.

Pars plana vitrectomy with silicone oil or gas endotamponade in HIV-related rhegmatogenous retinal detachments in Thai patients.

OBJECTIVE: To evaluate the efficacy and results of pars plana vitrectomy with endotamponade for retinal detachments caused by necrotizing retinitis in HIV patients. MATERIAL AND METHOD: The data of patients with HIV-related retinal detachment who underwent pars plana vitrectomy with silicone oil or gas endotamponade between January 2003 and June 2005 were retrospectively reviewed The outcome measures were demographic data, anatomical, and visual results. RESULTS: Of all 24 eyes from 20 patients, 19 eyes underwent pars plana vitrectomy with silicone oil tamponade and 5 eyes with long-acting gas tamponade. Mean follow up time was 13 months (range 2-33 months). The overall anatomical success was 83% (84% and 80% with silicone oil and gas tamponade, respectively). Final best corrected visual acuity was equal or better than 5/200 in 12 eyes (50%). Forty-six percent had stabled or improved vision at the end of follow-up. CONCLUSION: Pars plana vitrectomy with silicone oil or gas tamponade gives the high anatomical success rate in the repair of retinal detachments caused by necrotizing retinitis in HIV patients. There were the same reattachment rate and visual results between the two tamponade groups. However, the use of gas tamponade may be effective in patients with highly active antiretroviral therapy (HAART).