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Background: Ophthalmoscopy is a valuable tool in clinical practice. We report the use of a novel smartphone-based handheld device for visualisation and photo-documentation of the ocular fundus in veterinary medicine., Methods: Selected veterinary patients of a referral ophthalmology service were included if one or both eyes had clear ocular media, allowing for examination of the fundus. Following pharmacological mydriasis, fundic images were obtained with a handheld fundus camera (Volk VistaView). For comparison, the fundus of a subset of animals was also imaged with a veterinary-specific fundus camera (Optomed Smartscope VET2)., Results: The large field of view achieved by the Volk VistaView allowed for rapid and thorough observation of the ocular fundus in animals, providing a tool to visualise and record common pathologies of the posterior segment. Captured fundic images were sometimes overexposed, with the tapetal fundus artificially appearing hyperreflective when using the Volk VistaView camera, a finding that was less frequent when activating a 'veterinary mode' that reduced the sensitivity of the camera's sensor. The Volk VistaView compared well with the Optomed Smartscope VET2., Limitation: The main study limitation was the small sample size., Conclusions: The Volk VistaView camera was easy to use and provided good-quality fundic images in veterinary patients with healthy or diseased eyes, offering a wide field of view that was ideal for screening purposes., (© 2024 The Authors. Veterinary Record published by John Wiley & Sons Ltd on behalf of British Veterinary Association.)

The aim of this study was to better understand the role of apoptosis in a retinal ischaemia-reperfusion injury model and to determine whether sildenafil citrate treatment can prevent retinal cell apoptosis. Thirty-six rats were divided into a control group (n = 6) and two experimentally induced ischaemia-reperfusion groups (7 and 21 days; n = 15 per group). The induced ischaemia-reperfusion groups were treated with sildenafil for 7 and 21 days (n = 10 per group), and 10 animals were treated with a placebo for the same period (n = 5 per group). Paracentesis of the anterior chamber was performed with a 30-G needle attached to a saline solution (0.9%) bag positioned at a height of 150 cm above the eye for 60 min. Intraocular pressure was measured by rebound tonometer (TonoVet ® ). The eyes were analysed by histology and morphometry, and by immunohistochemistry and qRT-PCR for expression of Caspase-7, Caspase-6, Caspase-9, Tnf-r2, Fas-l, Bcl-2 and Bax. Sildenafil-treated animals showed lower levels of histopathological changes (inflammatory, cellular and tissue) than their placebo-treated counterparts at both 7 and 21 days. The retinal ganglion cell layer (RGC) was preserved in the sildenafil groups (SG), with a cell count closer to control than in the placebo groups (PG). Caspase-7 expression was significantly higher in both treated groups at 7 days compared to controls. Gene expression levels in both treatment groups differed from the controls, but in SG Bax and Caspase-6 expression levels were similar to control animals. These results suggest that the main mechanism of retinal cell death in this model is apoptosis, as there is an increase in pro-apoptotic factors and decrease in the anti-apoptotic ones. Also, sildenafil seems to protect the retinal ganglion cell layer from apoptosis. Cell survival was evident in the histological and morphometric analyses, and sildenafil treatment had a protective effect in the apoptosis pathways, with gene expression levels in SG similar to the controls., (© 2017 The Authors. International Journal of Experimental Pathology © 2017 International Journal of Experimental Pathology.)

Purpose: Retinal ischemia is a common cause of visual impairment and blindness. Sildenafil, a PDE5 inhibitor which inhibits cGMP degradation and in turn prolongs the effect of nitric oxide, has been shown to be protective in a number of ischemia/reperfusion (I/R) injuries, as well as in neuronal damage. We hypothesized that treatment with sildenafil might be neuroprotective in a model of acute retinal I/R injury., Methods: Anterior chamber cannulation was performed to induce unilateral I/R injury in 38 Lewis rats. Animals received intraperitoneal injections of sildenafil (0.5 and 1 mg/kg once a day, for a period of 7 and 18 days, respectively), or saline. Electroretinography recordings, retinal ganglion cell (RGC) counts following retrograde labeling with fluorogold, histopathology, and immunohistochemistry (IHC) using antibodies against PDE5, NOS2, caspase-3, caspase-9, and Bcl-2 were conducted., Results: No significant differences in electroretinography, RGC counts, or retinal morphometry were observed between experimental eyes of sildenafil- and saline-treated animals. A tendency toward less necrosis in histopathology, and a slight trend toward lower PDE5, NOS2, and caspase-9 and higher Bcl-2 IHC scores were evident in experimental retinas of sildenafil-treated animals., Conclusions: Electroretinography, RGC counts, and retinal morphometry failed to show any neuroprotective effect of sildenafil in acute retinal I/R injury in rats. A slight positive effect of sildenafil was qualitatively indicated by histopathology and IHC.

Purpose: To conduct ophthalmic, behavioral, electrophysiological, and genetic testing on two related Gordon setters presented for day blindness and compare findings with those of nine related and unrelated Gordon setters., Methods: All dogs underwent comprehensive ophthalmic examination. Maze testing was conducted under different light intensities. Rod and cone function was assessed electroretinographically. DNA samples were screened for five canine retinal disease gene mutations., Results: Ophthalmic examination was unremarkable in all dogs. There was no notable difference between day blind dogs and the reference population in scotopic and mesopic maze tests. Day blind dogs performed worse in the photopic maze with slower course completion time and more obstacle collisions. Electroretinography revealed extinguished cone function in day blind dogs and depressed rod responses in all but two reference dogs. One reference population dog presented with day blindness 1 year after initial examination. Mutations that cause achromatopsia (in CNGB3) and cone-rod dystrophies (in ADAM9 and IQCB1) were not detected in any dog tested, although five reference dogs were carriers of the mutation in C2orf71 that causes rod-cone degeneration 4 (rcd4) in Gordon setters and in polski owczarek nizinny dogs., Conclusions: This report describes a novel retinopathy in related Gordon setters that has clinical signs and vision testing results consistent with achromatopsia but electroretinographic results suggestive of cone-rod dystrophy. The majority of Gordon setters in this study had low rod responses on electroretinography but it is unclear whether this was indicative of rod dysfunction or normal for the breed. Longer-term observation of affected individuals is warranted., (© 2015 American College of Veterinary Ophthalmologists.)

Objective: To perform a clinical, ophthalmological, and electroretinographic assessment of retinopathic lesions in German Shepherd dogs., Animals: The study was conducted on 14 German Shepherds diagnosed with retinopathy during the course of an ophthalmological checkup. The animals were systemically healthy police dogs used for patrolling and tracking duties and which were, at times, exposed to considerable physical strain and stress., Procedure: Periodic ophthalmological examinations using slit-lamp biomicroscopy, direct and indirect ophthalmoscopy, and photography, as well as maze testing, were performed on all dogs. Electroretinography (ERG) was performed on 10 affected German Shepherds and eight control dogs., Results: Ophthalmological examination revealed areas of tapetal hyper-reflectivity with pigmented centers, which were characteristic of inactive chorioretinitis. Most of the lesions were in proximity to blood vessels, and in a number of eyes, progression was observed during repeated examinations. Transition from active to inactive lesions, as well as onset in previously unaffected eyes, was also recorded. The ERG recordings showed impaired cone function, with significantly lower b-wave amplitudes and prolonged implicit times, in the mixed rod-cone, photopic, and flicker tests of affected dogs (P < 0.05)., Conclusions: Retinopathy observed in German Shepherd dogs is characterized by areas of tapetal hyper-reflectivity with pigmented centers. The underlying causes of retinopathy in German Shepherd dogs remain unknown, although husbandry conditions and proximity of the lesions to blood vessels may suggest an association with physical exertion or circulatory disorders, respectively., (© 2012 American College of Veterinary Ophthalmologists.)

Purpose: Age-related changes in retinal ganglion cell (RGC) activity may impact results of long-term functional studies of disease progression and drug efficacy in humans and animal models. Though these changes can be evaluated using the pattern electroretinogram (PERG), longitudinal studies suffer from failure of follow-up from birth to senescence. Our aim was to perform a long-term, longitudinal study evaluating age-related changes in the rat PERG, by conducting repeated, serial recordings in the same animals. Additionally, we tested the hypothesis that neuroprotective treatment using glatiramer acetate (COP-1) immunization may delay age-related decline in function., Methods: PERG was recorded from six untreated and seven Cop-1-immunized Lewis rats. Recordings were conducted at 2- to 4-week intervals from age 5 to 59 weeks., Results: PERG amplitudes significantly increased between 5 to 7 weeks of age, and decreased from age 30 weeks onward (P = 0.016 and 0.0002, respectively). Amplitudes fluctuated insignificantly in weeks 7 to 30, with peak amplitudes reached at age 18 weeks in most spatial frequencies tested. N2 implicit times were shortened, mainly during weeks 5 to 18 and 40 to 59 (P < 0.001). PERG amplitudes of Cop-1-treated rats were similar to controls (P = 0.137) but peaked later (22-26 weeks)., Conclusions: This 14-month-long study provided accurate measurement of developmental and aging changes of rat RGC function using repeated testing of individual animals. We found functional development to extend beyond the reported period of structural changes. Cop-1-immunized rats were not protected against age-related decline in inner retinal function, although their PERG maturation dynamics were altered.

With the increasing use of the rat as an animal model for glaucoma and for the evaluation of neuroprotective treatments, there is a need for a sensitive test of retinal ganglion cell (RGC) function in this species. The aims of this study were to detect functional abnormalities of the inner retina in a rat model of high intraocular pressure (IOP) using the pattern electroretinogram (PERG), and to correlate them with morphometric analysis of RGC survival and the functional integrity of the inner retina. Unilateral ocular hypertension was induced in 17 Lewis rats through laser photocoagulation. Pattern ERGs were recorded prior to lasering and 3 weeks later, using a series of shifting patterns of decreasing spatial frequency projected directly onto the animals' fundus. IOP was measured at the same intervals, and the number of surviving RGCs estimated. Low amplitude PERG signals could be recorded in response to a narrow grating of 0.368 cycles per degree (cpd), and increased with stimulus size. Lasering caused mean (+/-s.d.) IOP to increase significantly from 18.3+/-4.5 (baseline) to 29.8+/-8.8 mmHg within 3 weeks (p<0.0001). At this time, PERG amplitudes were significantly reduced (p<0.05), declining an average of 45% compared to the normotensive, control eyes. No outer retinal damage was observed, but the mean number of RGCs decreased significantly (p<0.001), from 2 525.0+/-372.4 to 1 542.8+/-333.8 cells per mm2. This decrease in RGC number was significantly (p=0.03) correlated the decrease in PERG amplitude. The correlation between functional integrity of the inner retina and the rat PERG was further demonstrated by intravitreal tetrodotoxin injections, which temporarily abolished the PERG but did not affect outer retinal activity, reflected in the flash ERG. The evidence for early functional deficits, combined with tonometry and documentation of correlated ganglion cells loss, confirms the sensitivity of this diagnostic tool and the validity and importance of this animal model in glaucoma research.

Retinitis pigmentosa (RP) is a heterogeneous inherited retinal disorder. Mutations in KIZ cause autosomal recessive (AR) RP. We aimed to characterize the genotype, expression pattern, and phenotype in a large cohort of KIZ cases. Sanger and whole exome sequencing were used to identify the KIZ variants. Medical records were reviewed and analyzed. Thirty-one patients with biallelic KIZ mutations were identified: 28 homozygous for c.226C>T (p.R76*), 2 compound heterozygous for p.R76* and c.3G>A (p.M1?), and one homozygous for c.247C>T (p.R83*). c.226C>T is a founder mutation among patients of Jewish descent. The clinical parameters were less severe in KIZ compared to DHDDS and FAM161A cases. RT-PCR analysis in fibroblast cells revealed the presence of four different transcripts in both WT and mutant samples with a lower percentage of the WT transcript in patients. Sequence analysis identified an exonic sequence enhancer (ESE) that includes the c.226 position which is affected by the mutation. KIZ mutations are an uncommon cause of IRD worldwide but are not rare among Ashkenazi Jews. Our data indicate that p.R76* affect an ESE which in turn results in the pronounced skipping of exon 3. Therefore, RNA-based therapies might show low efficacy since the mutant transcripts are spliced. [ABSTRACT FROM AUTHOR]

Objective: Electroretinography (ERG) is used prior to cataract removal surgery to assess retinal function. We aimed to replicate and improve upon previous studies by performing a full ECVO protocol and by examining the retina post‐surgery in all patients. Animals studied: One hundred twenty‐seven eyes from 67 dogs were included in the study. Procedures: A full ECVO protocol electroretinography, which includes extensive rod and cone analysis, was performed on all dogs presenting for cataract surgery. Results: Our main findings were that amplitudes, but not implicit times of rod responses decreased with advanced cataracts. Amplitudes of the single flash rod and rod flicker responses were significantly lower in eyes with mature cataracts, and the former also decreased in hypermature cataracts. Cone flicker amplitude responses were also significantly lower in eyes with mature and hypermature cataracts. However, mixed single flash rod‐cone and cone responses, with the exception of the mixed rod‐cone a‐wave amplitude in eyes with hypermature cataracts, were unaffected by cataract stage. The b‐wave amplitude of the scotopic, mixed rod‐cone, and photopic cone responses were affected by age and decreased by an average of 2.9, 7.5, and 1.5 μV/year, retrospectively (p < 0.01). Conclusions: Lower ERG amplitudes in canine cataract patients may result from aging or the presence of advanced cataracts and may not indicate the presence of retinal disease. [ABSTRACT FROM AUTHOR]

Achromatopsia causes severely reduced visual acuity, photoaversion, and inability to discern colors due to cone photoreceptor dysfunction. In 2010, we reported on day-blindness in sheep caused by a stop-codon mutation of the ovine CNGA3 gene and began gene augmentation therapy trials in this naturally occurring large animal model of CNGA3 achromatopsia. The purpose of this study was to evaluate long-term efficacy and safety results of treatment, findings that hold great relevance for clinical trials that started recently in CNGA3 achromatopsia patients. Nine day-blind sheep were available for long-term follow up. The right eye of each sheep was treated with a single subretinal injection of an Adeno-Associated Virus Type 5 (AAV5) vector carrying either a mouse (n = 4) or a human (n = 5) CNGA3 transgene under control of the 2.1-Kb red/green opsin promoter. The efficacy of treatment was assessed periodically with photopic maze tests and electroretinographic (ERG) recordings for as long as 74 months postoperatively. Safety was assessed by repeated ophthalmic examinations and scotopic ERG recordings. The retinas of three animals that died of unrelated causes >5 years post-treatment were studied histologically and immunohistochemically using anti-hCNGA3 and anti-red/green cone opsin antibodies. Passage time and number of collisions of treated sheep in the photopic maze test were significantly lower at all follow-up examinations as compared with pretreatment values (p = 0.0025 and p < 0.001, respectively). ERG Critical Flicker Fusion Frequency and flicker amplitudes at 30 and 40 Hz showed significant improvement following treatment (p < 0.0001) throughout the study. Ophthalmic examinations and rod ERG recordings showed no abnormalities in the treated eyes. Immunohistochemistry revealed the presence of CNGA3 protein in red/green opsin-positive cells (cones) of the treated eyes. Our results show significant, long-term improvement in cone function, demonstrating a robust rescue effect up to six years following a single treatment with a viral vector that provides episomal delivery of the transgene. This unique follow-up duration confirms the safe and stable nature of AAV5 gene therapy in the ovine achromatopsia model. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate an innovative approach for closing retinal tears using DuraSeal™ (DS) hydrogel sealant in a rabbit model.Methods: Retinal detachment with a small tear was performed on 20 New Zealand rabbits. Thereafter, rabbits were divided into two groups; the experimental group received a transscleral injection of 0.1 ml DS into the subretinal space whereas the control group received sham injection of saline. Eyes were clinically evaluated using indirect ophthalmoscopy, retinal function was recorded in ten rabbits by electroretinography and the sealant's toxicity was evaluated histopathologically.Results: We found that the DS hydrogel was easily injected transsclerally into the subretinal space of the detached retinas with no major complications. Retinal reattachment was seen in both groups within 2 weeks with no toxicity to the sensory retina. There were no significant differences in retinal function between groups.Conclusion: Subretinal injection of hydrogel through a transscleral route is easy to perform and may open a new avenue in the treatment of retinal detachment. However, the efficacy of the DS as a tamponade for sealing retinal tear is yet to be definite. Long-term clinical, functional, and toxicological studies are needed to evaluate its full potential for clinical applications. [ABSTRACT FROM AUTHOR]

Achromatopsia is an inherited retinal disease characterized by loss of cone photoreceptor function. Day blind CNGA3 mutant Improved Awassi sheep provide a large animal model for achromatopsia. This study measured refractive error and axial length parameters of the eye in this model and evaluated chromatic pupillary light reflex (cPLR) testing as a potential screening test for loss of cone function. Twenty-one CNGA3 mutant, Improved Awassi, 12 control Afec-Assaf and 12 control breed-matched wild-type (WT) Awassi sheep were examined using streak retinoscopy and B-mode ocular ultrasonography. Four CNGA3 mutant and four Afec-Assaf control sheep underwent cPLR testing. Statistical tests showed that day-blind sheep are significantly more myopic than both Afec-Assaf and WT Awassi controls. Day-blind sheep had significantly longer vitreous axial length compared to WT Awassi (1.43 ± 0.13 and 1.23 ± 0.06 cm, respectively, p < 0.0002) and no response to bright red light compared to both controls. Lack of response to bright red light is consistent with cone dysfunction, demonstrating that cPLR can be used to diagnose day blindness in sheep. Day-blind sheep were found to exhibit myopia and increased vitreous chamber depth, providing a naturally occurring large animal model of myopia. [ABSTRACT FROM AUTHOR]

Abtract Recombinant adeno associated viruses (AAV) are the most commonly used vectors in animal model studies of gene therapy for retinal diseases. The ability of a vector to localize and remain in the target tissue, and in this manner to avoid off-target effects beyond the site of delivery, is critical to the efficacy and safety of the treatment. The in vivo imaging system (IVIS) is a non-invasive imaging tool used for detection and quantification of bioluminescence activity in rodents. Our aim was to investigate whether IVIS can detect localization and biodistribution of AAV5 vector in mice following subretinal (SR) and intravitreal (IVT) injections. AAV5 carrying firefly luciferase DNA under control of the ubiquitous cytomegalovirus (CMV) promoter was injected unilaterally IVT or SR (in the central or peripheral retina) of forty-one mice. Luciferase activity was tracked for up to 60 weeks in the longest surviving animals, using repeated (up to 12 times) IVIS bioluminescence imaging. Luciferase presence was also confirmed immunohistochemically (IHC) and by PCR in representative animals. In the SR group, IVIS readings demonstrated luciferase activity in all (32/32) eyes, and luciferase presence was confirmed by IHC (4/4 eyes) and PCR (12/12 eyes). In the IVT group, IVIS readings demonstrated luciferase activity in 7/9 eyes, and luciferase presence was confirmed by PCR in 5/5 eyes and by IHC (2/2 eyes). In two SR-injected animals (one each from the central and peripheral injection sites), PCR detected luciferase presence in the ipsilateral optic nerves, a finding that was not detected by IVIS or IHC. Our results show that when evaluating SR delivery, IVIS has a sensitivity and specificity of 100% compared with the gold standard PCR. When evaluating IVT delivery, IVIS has a sensitivity of 78% and specificity of 100%. These finding confirm the ability of IVIS to detect in-vivo localized expression of AAV following SR delivery in the retina up to 60 weeks post-treatment, using repeated imaging for longitudinal evaluation, without fading of the biological signal, thereby replacing the need for post mortem processing in order to confirm vector expression. However, IVIS is probably not sensitive enough, compared with genome detection, to demonstrate biodistribution to the optic nerve, as it could not detect luciferase activity in ipsilateral optic nerves following SR delivery in mice. Highlights • AAV expression was imaged in-vivo after subretinal/intravitreal injections in mice. • Imaging was non-invasive, with repeated imaging sessions conducted up to 60 weeks. • Compared to PCR, this detection method was highly sensitive and specific. • Method allows sequential, long-term monitoring of biodistribution in same animal. • Method can replace terminal PCR and IHC studies of vector biodistribution. [ABSTRACT FROM AUTHOR]