Outer retinal transduction by AAV2-7m8 following intravitreal injection in a sheep model of CNGA3 achromatopsia.

Sheep carrying a mutated CNGA3 gene exhibit diminished cone function and provide a naturally occurring large animal model of achromatopsia. Subretinal injection of a vector carrying the CNGA3 transgene resulted in long-term recovery of cone function and photopic vision in these sheep. Research is underway to develop efficacious vectors that would enable safer transgene delivery, while avoiding potential drawbacks of subretinal injections. The current study evaluated two modified vectors, adeno-associated virus 2-7m8 (AAV2-7m8) and AAV9-7m8. Intravitreal injection of AAV2-7m8 carrying enhanced green fluorescent protein under a cone-specific promoter resulted in moderate photoreceptor transduction in wild-type sheep, whereas peripheral subretinal delivery of AAV9-7m8 resulted in the radial spread of the vector beyond the point of deposition. Intravitreal injection of AAV2-7m8 carrying human CNGA3 in mutant sheep resulted in mild photoreceptor transduction, but did not lead to the clinical rescue of photopic vision, while day-blind sheep treated with a subretinal injection exhibited functional recovery of photopic vision. Transgene messenger RNA levels in retinas of intravitreally treated eyes amounted to 4-23% of the endogenous CNGA3 levels, indicating that expression levels >23% are needed to achieve clinical rescue. Overall, our results indicate intravitreal injections of AAV2.7m8 transduce ovine photoreceptors, but not with sufficient efficacy to achieve clinical rescue in CNGA3 mutant sheep.

Fellow eye effect of unilateral intravitreal bevacizumab injection in eyes with diabetic macular edema.

AIMS: Anti-vascular endothelial growth factor compounds are routinely used for the treatment of diabetic macular edema (DME). We aim to evaluate for the existence and magnitude of treatment effect on fellow un-injected eyes. METHODS: A consecutive group of patients with bilateral DME who received unilateral bevacizumab injections was retrospectively evaluated. Data collected included demographics, ophthalmic and systemic findings, and optical coherence tomography (OCT) measurements of macular thickness. RESULTS: Thirty-five patients were evaluated. Mean follow-up was 245 days (range: 30-800), and the mean number of bevacizumab injections was 3.6 (range: 1-11). At end of follow-up, the mean (SD) OCT central subfield thickness reduced by 72 ± 112 micron in the injected eye (from 469 ± 139 to 397 ± 120 micron; P=0.001), while in the non-injected eye it reduced by 49 ± 75 micron (from 380 ± 130 to 331 ± 106 micron; P<0.001). Sixteen injected eyes (45.7%) showed central subfield thickness reduction of ≥50 micron while 10 (28.6%) non-injected eyes showed such thickness reduction. Improved VA following treatment was detected in 14 (40%) injected eyes and in 15 (43%) non-injected eyes. CONCLUSIONS: Unilateral bevacizumab injections in patients with bilateral DME are often associated with bilateral response. SUMMARY STATEMENT: Anti-vascular endothelial growth factor compounds are routinely used for the treatment of diabetic macular edema (DME). In this retrospective study, we show that unilateral bevacizumab injections often result in reduction of the macular thickness in the fellow un-injected eye.

Intravitreal bevacizumab therapy for neovascular age-related macular degeneration associated with poor initial visual acuity.

AIM: The aim of the study was to assess the efficacy of intravitreal bevacizumab injections for eyes with neovascular age-related macular degeneration (NVAMD) and poor initial visual acuity (VA). METHODS: A retrospective study of 44 consecutive treatment-naïve eyes with NVAMD who had initial VA of 0.1 decimal or worse, and that were treated with intravitreal bevacizumab injections, was undertaken. Charts, optical coherence tomography (OCT) and fluorescein angiograms (FAs) were reviewed for the purpose of the study. RESULTS: Mean lesion size was 3375 (SD 2116) microm, all lesions showed sub- or intra-retinal fluid in OCT, and active neovascularisation comprised 41.6 (SD 17.7)% (range 10-90%) of the lesion area according to FA. The mean follow-up time was 3.9 (SD 5.8) (range 1-21) months. Patients received a mean of 2.6 (SD 2.4) bevacizumab injections (range 1-14), and mean VA improved from 1.85 (SD 0.64) to 1.52 (SD 0.77) LogMAR (p = 0.002). At final examination, nine eyes (20%) had reduced VA, ten eyes (23%) had stable VA and 25 eyes (57%) had improved VA compared with baseline. Following treatment, mean macular thickness was reduced from 332 (SD 98) to 248 (SD 79) microm (p<0.0001). CONCLUSIONS: Poor initial VA should not prevent use of bevacizumab in eyes with NVAMD. Selection of patients with signs of active neovascularisation based on ophthalmoscopy, OCT and FA may increase the likelihood of a favourable response to treatment.

Lack of benefit of early awareness to age-related macular degeneration.

AIMS: To assess the rate of early awareness to the presence of age-related macular degeneration (AMD) and whether it enables early detection of transition to neovascular AMD (NVAMD) as compared with patients whose first presentation to an ophthalmologist is already at the neovascular stage of disease. METHODS: A retrospective analysis of 268 eyes of 268 consecutive patients with newly diagnosed NVAMD that were treated in a tertiary referral centre was performed. Patients were classified into those who were unaware (Group 1), or aware (Group 2), of the fact that they had AMD before diagnosis of NVAMD. Visual acuity, lesion size and composition, and demographics were compared between both groups. RESULTS: In all, 185 patients (69%) and 83 patients (31%) were classified to Groups 1 and 2, respectively. Patients in Groups 1 and 2 had similar demographic characteristics, presenting visual acuity and lesion size, and lesion compositions. Group 1 patients were more likely to have a positive history for smoking (41 vs26% in Group 2, P=0.03), whereas Group 2 patients were more likely to have positive family history for AMD (20 vs10%, P=0.02). CONCLUSIONS: These data suggest that current screening methods fail to identify the majority of patients with AMD before the development of NVAMD. The findings also demonstrate that in the routine clinical setting, prior awareness of AMD may not facilitate early detection of treatable choroidal neovascularization lesions.

Paediatric vs adult retinal detachment.

OBJECTIVE: To evaluate the causes, incidences, characteristics, and treatment outcomes of paediatric vs adult retinal detachment. PATIENTS AND METHODS: One hundred and sixty (136 patients) out of 2408 consecutive retinal detachments (6.6%) at our facility occurred in children under the age of 18 years. Of them, 144 eyes (90%) of 127 (93%) children were treated and compared with a sample of 56 consecutive retinal detachments in 50 adults (over the age of 18 years). The parameters for comparison included cause, type of retinal detachment, its extent, macular involvement, number of tears, number and types of surgery, and the anatomic and functional surgical outcome. RESULTS: Statistically significant differences were found in the type of retinal detachment. Rhegmatogenous RD was less common (P=0.004), and exudative RD was more common (P=0.021) in the paediatric group. Ocular trauma and ocular syndromes were more common in the paediatric group (P<0.001), while myopia, posterior vitreous detachment, and retinal detachment following cataract surgery were less common in this group compared with adults (P<0.001, <0.001, and 0.001, respectively). Ocular pathologies associated with retinal detachment were more common in the paediatric group (P<0.001). Initial and last visual acuity of >20/400, last visual acuity of >20/40, and retinal complete reattachment were higher in adults (P<0.001). CONCLUSIONS: The type of retinal detachment, causes and outcomes were statistically different between paediatric and adult cases. The less successful functional and anatomical outcomes of retinal detachment surgery in children may reflect the different aetiologies and indicate the need for aetiology-specific treatment strategies according to each aetiology.

Octreotide, a somatostatin analogue, fails to inhibit hypoxia-induced retinal neovascularization in the neonatal rat.

OBJECTIVE: Octreotide, a somatostatin analogue, has been shown to prevent angiogenesis in diverse in vitro models. We evaluated its effect on retinal neovascularization in vivo, using a neonatal rat retinopathy model. METHODS: We used, on alternating days, hypoxia (10% O2) and hyperoxia (50% O2) during the first 14 days of neonatal rats, to induce retinal neovascularization. Half of the rats were injected subcutaneously with octreotide 0.7 microg/g BW twice daily. At day 18 the eyes were evaluated for the presence of epiretinal and vitreal hemorrhage, neovascularization and epiretinal proliferation. Octreotide pharmacokinetics and its effect on serum growth hormone (GH) and insulin-like growth factor I (IGF-I) were examined in 28 rats. RESULTS: Serum octreotide levels were 667 microg/l two hours after injection, 26.4 microg/l after nine hours and 3.2 microg/l after 14 hours. GH levels were decreased by 40% (p = 0.002) two hours after injection but thereafter returned to baseline. IGF-I levels were unchanged two hours after injection and were elevated by 26% 14 hours after injection (p = 0.02). Epiretinal membranes were highly associated with epiretinal hemorrhages (p < 0.001), while retinal neovascularization was notably associated with vitreal hemorrhages (p < 0.001). CONCLUSIONS: Twice-daily injections of octreotide failed to produce sustained decrease in serum GH, but produced rebound elevation of serum IGF-I. Accordingly, no statistically significant effect of injections on retinal pathology was noted. This finding, however, does not contradict our assumption that GH suppression may decrease the severity of retinopathy.

Gene expression of insulin-like growth factor-I, its receptor and binding proteins in retina under hypoxic conditions.

Hypoxia is the main stimulus for neovascularization in the retina. Insulin-like growth factor-I (IGF-I) is thought to be one of the mediators of this process. Severe persistent hypoxia, as occurs in central retinal artery occlusion, is associated with less retinal neovascularization than relative hypoxia. To study the influence of different types of hypoxia on the IGF system, we used a model of neonatal rat retina that responds with neovascularization to a relative hypoxic stimulus produced by alternating oxygen concentrations in the respired air. We studied the influence of 24-hour hypoxia (10% oxygen), 48-hour hyperoxia (75% oxygen), and relative hypoxia (shifting from 48 hours in 75% oxygen to 24 hours in room air) on the gene expression of IGF-I, IGF-I receptor (IGF-IR), and IGF binding protein-1 (IGFBP-1), IGFBP-2, and IGFBP-3 in retina using a solution hybridization RNase protection assay. Hypoxia induced a significant increase in retinal IGF-IR (178%), IGFBP-2 (227%), and IGFBP-3 (317%) mRNA; however, retinal IGF-I mRNA was reduced, as well as serum growth hormone (GH). Relative hypoxia caused a similar but less pronounced trend in the gene expression of IGF-IR and the binding proteins, whereas retinal IGF-I mRNA was unchanged and serum GH was elevated. Both hypoxia and relative hypoxia may cause IGF system stimulation in the retina through upregulation of IGF-IR and IGFBPs. This stimulation may result in neovascularization. However, during hypoxia, low levels of tissue oxygenation and reduced local production of IGF-I may impede the neovascularization process.

Conjunctival oculosporidiosis in east Africa caused by Rhinosporidium seeberi.

BACKGROUND AND OBJECTIVE: Conjunctival rhinosporidiosis is an infectious disease rarely recorded outside the Indian subcontinent. The disease is caused by Rhinosporidium seeberi, an endosporulating microorganism of uncertain taxonomic classification. We report a series of cases manifesting this infection. MATERIAL AND METHODS: The demographic, clinical, and histopathologic data of 14 cases of conjunctival rhinosporidiosis on record at our Ophthalmic Pathology Laboratory were reviewed. RESULTS: All cases were from East Africa; 10 were from Malawi and 4 from Kenya. Ten specimens were from males and three from females. Their age ranged from 7 to 20 years. All patients were treated by surgical excision, and no recurrence was recorded. None of the cases was diagnosed clinically as rhinosporidiosis. Histologically, all stages of the organism's life cycle could be found in the excised tissue, from small trophocytes to large sporangia-containing sporoblasts. There were changes in histochemical stainings with growth and maturation. In general, the inflammation was of chronic nongranulomatous type. CONCLUSIONS: Conjunctival rhinosporidiosis is a rare infectious disease that typically appears in young males in rural regions, and that can be treated by surgical excision. It typically causes chronic nongranulomatous inflammation. Various stages of the R seeberi life cycle can be seen in the affected tissue.

Protection of the transiently ischemic cat retina by zinc-desferrioxamine.

PURPOSE: A previous study indicated that hydroxyl radicals are generated in the cat retina during the early reperfusion phase after 90 minutes of ischemia. Salicylate was injected intravenously, and its conversion to 2,3-dihydroxybenzoic acid (2,3-DHBA) served as a marker of hydroxyl radicals. The authors attempted to prevent this free radical generation during reperfusion. METHODS: After salicylate administration, both eyes (15 minutes apart) of 15 cats were subjected to 90 minutes retinal ischemia. Following 5 minutes of reperfusion in the control eye, it was enucleated and processed for DHBA quantitation. Then, 7.5 mg of Zn-desferrioxamine (Zn-DFO) was injected intravenously into nine cats and saline into six cats. Five minutes later, reperfusion was induced in the experimental eye for 5 minutes, followed by enucleation. In one eye each of 12 other cats, scotopic electroretinographic (ERG) studies were carried out during 90 minutes of ischemia and 16 to 18 hours of reperfusion. Five minutes before termination of the ischemia, six animals were injected with 7.5 mg Zn-DFO and six with saline. RESULTS: The normalized levels of 2,3-DHBA were lower in the experimental eyes than in their fellow controls only after Zn-DFO treatment (P = 0.01). In the ERG studies, after 16 to 18 hours of reperfusion, the mean b-wave-ERG amplitudes in the eyes of the saline-treated cats (n = 6) were 8.4% +/- 4.0% of the preischemic stage, and 70.5% +/- 6.7% of the Zn-DFO-treated cats (n = 6, P = 0.004). CONCLUSIONS: Protection of the cat retina against ischemia and reperfusion injury by Zn-DFO was evident, most probably through its inhibitory effect on the generation of hydroxyl radicals during reperfusion.