XIAP Protects Retinal Ganglion Cells in the Mutant ND4 Mouse Model of Leber Hereditary Optic Neuropathy.

Purpose: Leber hereditary optic neuropathy (LHON) is a genetic form of vision loss that occurs primarily owing to mutations in the nicotinamide adenine dinucleotide dehydrogenase (ND) subunits that make up complex I of the electron transport chain. LHON mutations result in the apoptotic death of retinal ganglion cells. We tested the hypothesis that gene therapy with the X-linked inhibitor of apoptosis (XIAP) would prevent retinal ganglion cell apoptosis and reduce disease progression in a vector-induced mouse model of LHON that carries the ND4 mutation. Methods: Adeno-associated virus (AAV) encoding full length hemagglutinin-tagged XIAP (AAV2.HA-XIAP) or green fluorescent protein (AAV2.GFP) was injected into the vitreous of DBA/1J mice. Two weeks later, the LHON phenotype was induced by AAV delivery of mutant ND4 (AAV2.mND4FLAG) to the vitreous. Retinal function was assessed by pattern electroretinography. Optic nerves were harvested at 4 months, and the effects of XIAP therapy on nerve fiber layer and optic nerve integrity were evaluated using immunohistochemistry, transmission electron microscopy and magnetic resonance imaging. Results: During LHON disease progression, retinal ganglion cell axons are lost. Apoptotic cell bodies are seen in the nuclei of astrocytes or oligodendrocytes in the optic nerve, and there is thinning of the optic nerve and the nerve fiber layer of the retina. At 4 months after disease onset, XIAP gene therapy protects the nerve fiber layer and optic nerve architecture by preserving axon health. XIAP also decreases nuclear fragmentation in resident astrocytes or oligodendrocytes and decreases glial cell infiltration. Conclusions: XIAP therapy improves optic nerve health and delays disease progression in LHON.

The Diagnostic Utility of Multifocal Electroretinography in Detecting Chloroquine and Hydroxychloroquine Retinal Toxicity.

PURPOSE: To evaluate multifocal electroretinography (mfERG) as a screening test for detecting hydroxychloroquine and chloroquine toxicity. DESIGN: Diagnostic accuracy study. METHODS: Patients referred to the University of Ottawa for hydroxychloroquine or chloroquine retinopathy screening during 2011-2014 underwent 10-2 automated visual field, spectral domain optical coherence tomography, and mfERG testing. Patients with amblyopia, high myopia or hyperopia, coexisting retinal disease, or prior surgery were excluded. Abnormalities in parafoveal ring amplitudes or ring ratios were considered a positive mfERG result. We used the definition for hydroxychloroquine and chloroquine toxicity provided by the 2016 American Academy of Ophthalmology recommendations. Area under the curve (AUC) for each mfERG parameter and the sensitivity and specificity of mfERG were calculated. Logistic regression was used to model the effect of covariates in receiver operating characteristic (ROC) analyses. RESULTS: In total, 63 patients (47 female, 16 male) were included. Of 120 eyes, 16 (13.3%) had toxicity according to the American Academy of Ophthalmology guidelines, and 39 (32.5%) had positive mfERG findings. mfERG was found to have a sensitivity of 1.00 (95% CI 0.79-1.00) and a specificity of 0.78 (95% CI 0.69-0.85). Ring 2 amplitude had the best performance among all parameters (AUC 0.97, 95% CI 0.94-1.00). Ring 2 amplitude decreased linearly with increasing cumulative dose and daily dose. CONCLUSIONS: The high sensitivity of parafoveal depression on mfERG and its relationship to cumulative and daily dose illustrates an important role for objective functional testing. The high false-positive rate suggests a potential period where physiologic dysfunction is detected objectively on mfERG before structural change on spectral domain optical coherence tomography.

Overexpression of the X-Linked Inhibitor of Apoptosis Protects Against Retinal Degeneration in a Feline Model of Retinal Detachment.

Retinal detachment is an acute disorder in humans that is caused by trauma or disease, and it can often lead to permanent visual deficits that result from the death of photoreceptors in the retina. The final pathway for photoreceptor cell death is apoptosis and necroptosis. The X-linked inhibitor of apoptosis (XIAP) has been shown to block both of these cell death pathways. This study tested the effects of XIAP on photoreceptor survival in a feline model of retinal detachment. The study was performed in 12 cats, divided into two experimental groups. Six animals received a subretinal injection of adeno-associated virus (AAV) carrying XIAP, and six animals received AAV carrying green fluorescent protein (GFP) as a control. Three weeks after viral delivery, retinas were detached by injecting C3F8 gas into the subretinal space. Optical coherence tomography revealed that the retinal detachments resolved within 3-6 weeks as the gas was slowly resorbed. Analysis of histological sections through the plane of the detachment showed significant preservation of the photoreceptor layer in AAV-XIAP-treated animals compared to AAV-GFP-treated animals at 9 weeks after the detachment. XIAP-treated detached retinas were similar to intact controls. These studies support the potential for XIAP therapy in the treatment of human retinal detachment.

The Development of a Cat Model of Retinal Detachment and Re-attachment.

We present an optimized surgical technique for feline retinal detachment which allows for natural re-attachment, reduces retinal scarring and vitreal bands, and allows central placement of the detachment in close proximity to the optic nerve. This enables imaging via Optical Coherence Tomography (OCT) and multifocal electroretinography (mfERG) analysis. Ideal detachment conditions involve a lensectomy followed by a three-port pars plana vitrectomy. A 16-20 % retinal detachment is induced by injecting 8 % C3F8 gas into the subretinal space in the central retina with a 42G cannula. The retinal detachment resolves approximately 6 weeks post-surgery. Imaging is enhanced by using a 7.5 and 20 diopter lens for OCT and mfERG fundus imaging, respectively, to compensate for the removed lens.

Is Acute Zonal Occult Outer Retinopathy an Autoimmune Condition? A Case Report and Literature Review.

A 42-year-old woman with multiple sclerosis presented with focal decreased vision and photopsia in the left eye. Funduscopy and fluorescein angiography revealed focal chorioretinal atrophy, vascular attenuation, and bone spicules. Electroretinography revealed interocular reduction in b-wave amplitude, and Goldmann visual field perimetry studies revealed an inferior scotoma. The authors performed a literature review and conclude that the prevalence of acute zonal occult outer retinopathy in patients with autoimmune conditions may suggest that the condition is autoimmune in nature. Clinical history as well as funduscopic and retinal investigations are important in diagnosing acute zonal occult outer retinopathy.

Remission of nonparaneoplastic autoimmune retinopathy after minimal steroid treatment.

PURPOSE: To describe the clinical findings in a patient demonstrating recovery from nonparaneoplastic autoimmune retinopathy after a minimal course of steroid treatment. METHODS: Clinical presentation was documented, and paraclinical tests were obtained using Humphrey automated perimetry for visual fields, Western blotting for antiretinal antibodies, and electroretinography for evaluation of rod and cone function. RESULTS: Initial presentation revealed marked visual field deficits, electroretinographic dysfunction, and the presence of α-enolase autoantibodies. After a brief course of oral corticosteroids, the patient demonstrated improvement in visual fields, disappearance of α-enolase autoantibodies, partial recovery of the cone on-response, and complete recovery of the rod response. CONCLUSION: This case is distinguished from previous reports by the rapidity and degree of recovery, the brevity of treatment required, and the unique electroretinographic recovery pattern with concomitant disappearance of α-enolase autoantibodies. These findings suggest a pathologic role for α-enolase autoantibodies in autoimmune rod bipolar cell dysfunction. Identification of other cases exhibiting such improvements and associated autoantibody activity may expand our understanding of nonparaneoplastic autoimmune retinopathy disease pathogenesis.

Optimal optical coherence tomography-based measures in the diagnosis of clinically significant macular edema: retinal volume vs foveal thickness.

OBJECTIVE: To compare optical coherence tomography-based measures of retinal thickness and volume as quantitative tests for clinically significant macular edema (CSME). DESIGN: Diagnostic validation study. METHODS: Sixty-five eyes with diabetic retinopathy underwent stereo photographic and optical coherence tomographic examination. Stereo photographs were examined in a masked fashion to determine the presence or absence of CSME according to criteria from the Early Treatment Diabetic Retinopathy Study. Optical coherence tomography-based measurements of central foveal thickness as well as retinal volumes within a series of radii of fixation were generated. The main outcome measures were areas under receiver operating characteristic curves. Likelihood ratios, sensitivities, and specificities for the diagnosis of CSME were also evaluated. RESULTS: Retinal volumes within radii of 0.50 mm and 1.11 mm of fixation and central foveal thickness were the best variables for discriminating between those with and without CSME as evidenced by analysis of receiver operating characteristic curves. There were no significant differences among these 3 variables in their performance as diagnostic tests for CSME. CONCLUSIONS: Optical coherence tomography-based retinal volume and central foveal thickness variables display comparable abilities to discriminate between those with and without CSME. Both measures may have clinical applications as quantitative diagnostic tests for CSME.

Effect of eccentric and inconsistent fixation on retinal optical coherence tomography measures.

OBJECTIVE: To assess the relative stabilities of optical coherence tomography (OCT)-based retinal volume and central foveal thickness measurements in the setting of eccentric or inconsistent fixation. METHODS: Ten healthy right eyes underwent multiple macular OCT centered at fixation. To model the effect of eccentric or inconsistent fixation, OCT was repeated with scan centers precisely shifted by 0.50, 1.00, and 1.50 mm in each of 4 directions. At each scan location, retinal volumes within a series of radii of the scan center, as well as central foveal thickness, were calculated. The main outcome measure was the percentage effect of decentered scanning on each OCT-based variable. RESULTS: Central foveal thickness was the variable most affected in this model of eccentric and inconsistent fixation. This variable demonstrated changes from baseline-centered scans of up to 69.4%. Retinal volumes within a radii of the scan center measuring 1.11 mm or greater were least affected by decentered scanning, demonstrating maximum changes from baseline-centered scans of only 15.7% (P<.001 vs foveal thickness). CONCLUSION: Optical coherence tomography-based retinal volume quantification provides a more stable measure than foveal thickness in the setting of eccentric or inconsistent fixation as may occur in the setting of macular pathologic conditions.

XIAP protection of photoreceptors in animal models of retinitis pigmentosa.

BACKGROUND: Retinitis pigmentosa (RP) is a blinding genetic disorder that is caused by the death of photoreceptors in the outer nuclear layer of the retina. To date, 39 different genetic loci have been associated with the disease, and 28 mutated genes have been identified. Despite the complexity of the underlying genetic basis for RP, the final common pathway is photoreceptor cell death via apoptosis. METHODOLOGY/PRINCIPAL FINDINGS: In this study, P23H and S334ter rhodopsin transgenic rat models of RP were used to test the neuroprotective effects of anti-apoptotic gene therapy. Adeno-associated viruses (AAV) carrying the X-linked inhibitor of apoptosis (XIAP) or green fluorescent protein (GFP) were delivered subretinally into the eye of transgenic rat pups. Histological and functional measures were used to assess neuroprotection. XIAP is known to block apoptosis by inhibiting the action of caspases-3, -7 and -9. The results show that XIAP gene therapy provides long-term neuroprotection of photoreceptors at both structural and functional levels. CONCLUSIONS/SIGNIFICANCE: Our gene therapy strategy targets the apoptotic cascade, which is the final common pathway in all forms of retinitis pigmentosa. This strategy holds great promise for the treatment of RP, as it allows for the broad protection of photoreceptors, regardless of the initial disease causing mutation.

The use of subretinal triamcinolone acetonide in the management of neovascular age-related macular degeneration: a pilot study.

BACKGROUND: We conducted this study to investigate the toxicity and efficacy of pars plana vitrectomy combined with a single dose of sub-retinally administered triamcinolone acetonide (4 mg) in patients with subfoveal choroidal neovascular membranes secondary to age-related macular degeneration (AMD). METHODS: The important eligibility criteria included eyes with recent and progressive onset of decreased vision (

Structural and functional protection of photoreceptors from MNU-induced retinal degeneration by the X-linked inhibitor of apoptosis.

PURPOSE: To evaluate the neuroprotective effects of adenoassociated virus delivery of XIAP in N-methyl-N-nitrosourea (MNU)-induced retinal degeneration in Sprague-Dawley rats. METHODS: Sprague-Dawley rats were injected subretinally with recombinant adenoassociated virus (rAAV) encoding either XIAP or green fluorescent protein (GFP; injection control). Six weeks after injection, the animals received an intraperitoneal injection of MNU, a DNA methylating agent, at a dose of 60 mg/kg. Electroretinograms (ERGs) were recorded at 0, 24, 48 and 72 hours and 1 week after MNU. The rats were killed after the ERG was performed and were perfused with 4% paraformaldehyde. Eyes were then enucleated and embedded for cryosectioning. Eye sections were analyzed by TUNEL and histologic techniques. Real-time PCR and Western analysis were performed to confirm the overexpression of XIAP in injected eyes. RESULTS: Real-time PCR and Western analysis confirmed the overexpression of XIAP in virus-injected eyes in comparison to uninjected control eyes. At 24 hours after MNU injection, fewer cells had undergone apoptosis in the XIAP-treated eyes in comparison with GFP-injected or uninjected eyes. Hematoxylin and eosin staining revealed that the uninjected and GFP-injected photoreceptors were destroyed by 72 hours after injection of MNU, whereas the AAV-XIAP-injected eyes showed structural protection of the photoreceptors at all time points throughout the 1-week sampling period. ERGs showed functional protection up to 1 week after MNU injection in the AAV-XIAP-injected eye, whereas no response was observed in the control eye. CONCLUSIONS: The results suggest that XIAP is protective against this potent chemotoxic agent and holds promise as a therapeutic agent in gene therapy approaches to treating retinitis pigmentosa.