Assessment Of Retinal Function Research Articles

Gene augmentation therapy attenuates retinal degeneration in a knockout mouse model of Fam161a retinitis pigmentosa

Photoreceptor cell degeneration and death is the major hallmark of a wide group of human blinding diseases including age-related macular degeneration and inherited retinal diseases such as retinitis pigmentosa. In recent years, inherited retinal diseases have become the "testing ground" for novel therapeutic modalities, including gene and cell-based therapies. Currently there is no available treatment for retinitis pigmentosa caused by FAM161A biallelic pathogenic variants. In this study, we injected an adeno-associated virus encoding for the longer transcript of mFam161a into the subretinal space of P24-P29 Fam161a knockout mice to characterize the safety and efficacy of gene augmentation therapy. Serial in vivo assessment of retinal function and structure at 3, 6, and 8months of age using the optomotor response test, full-field electroretinography, fundus autofluorescence, and optical coherence tomography imaging as well as ex vivo quantitative histology and immunohistochemical studies revealed a significant structural and functional rescue effect in treated eyes accompanied by expression of the FAM161A protein in photoreceptors. The results of this study may serve as an important step toward future application of gene augmentation therapy in FAM161A-deficient patients by identifying a promising isoform to rescue photoreceptors and their function.

Retinitis Pigmentosa Associated with EYS Gene Mutations: Disease Severity Staging and Central Retina Atrophy

Eyes shut homolog (EYS) gene mutations are estimated to affect at least 5% of patients with autosomal recessive retinitis pigmentosa. Since there is no mammalian model of human EYS disease, it is important to investigate its age-related changes and the degree of central retinal impairment. A cohort of EYS patients was studied. They underwent full ophthalmic examination as well as assessment of retinal function and structure, by full-field and focal electroretinograms (ERGs) and spectral domain optical coherence tomography (OCT), respectively. The disease severity stage was determined by the RP stage scoring system (RP-SSS). Central retina atrophy (CRA) was estimated from the automatically calculated area of the sub-retinal pigment epithelium (RPE) illumination (SRI). The RP-SSS was positively correlated with age, showing an advanced severity score (≥8) at an age of 45 and a disease duration of 15 years. The RP-SSS was positively correlated with the CRA area. LogMAR visual acuity and ellipsoid zone width, but not ERG, were correlated with CRA. In EYS-related disease, the RP-SSS showed advanced severity at a relative early age and was correlated with the central area of the RPE/photoreceptor atrophy. These correlations may be relevant in view of therapeutic interventions aimed at rescuing rods and cones in EYS-retinopathy.

New model of complete retinal degeneration: A good tool for therapeutic essays?

AbstractPurpose: To characterize a mouse model of complete blindness after induction of retinal degeneration based on the degenerative capacity of NaIO3 on cell photoreceptors, rods and cones, and to test the effect of new pharmacological tools.Methods: Two doses of NaIO3 (40 mg/kg and 60 mg/kg) were intraperitoneally injected into a series of C57BL/6J mice with a mutation in the Opn4−/− gene. The effect of NaIO3 on the retina was assessed at 7, 14, 21 and 28 days after the injection by means of visual behavioural test, electroretinogram (ERG) recordings and immunohistochemical staining. To further assert the model's effectiveness, new optopharmacological agents were tested on the developed model, followed by visual testing.Results: Both doses of the degenerative agent induced a gradual reduction of the visual capacities of the animals. The different components of the ERG waves showed a marked decrease in their amplitude throughout the 28 days of the experiment, with the 60 mg/kg dose provoking a more pronounced functional loss. Similar results were observed in the behavioural tests, in which the animals' visual sensitivity, visual acuity, photomotor capacity were highly decreased. Same tests were performed under the effect of new optopharmacological therapies. Our results demonstrate not only the model's effectiveness, but also the usefulness of the new therapy for vision recover.Conclusions: NaIO3 induced murine model of retinal degeneration seems to be a good model for testing new pharmacological approaches to retinal diseases. Assessment of retinal function by electrophysiological tests, visual animal behaviour and retinal histology seem to be basic and reliable techniques for the evaluation of drug effect on this new animal model.

Resting state electroretinography: An innovative approach to intrinsic retinal function monitoring.

The electroretinogram (ERG) represents the biopotential evoked by the retina in response to a light stimulus. The flash evoked ERG (fERG) is the ERG modality most frequently used clinically to diagnose and monitor retinal disorders. We hereby present a new method to record spontaneous retinal activity, without the use of a flash stimulus, that we named the resting-state ERG (rsERG). The recordings were done in normal subjects under light- and dark-adaptation and with different background light conditions (i.e., variations of wavelength and intensity). Additionally, rsERG recordings were obtained in five patients with retinopathies. The signals were subsequently analyzed in the frequency domain, extracting both periodic (i.e., frequency peaks) and aperiodic (i.e., background trend) components of the signal. The later was further assessed through a multifractal analysis using Wavelet Leaders. Results show that, irrespective of the recording conditions used, the rsERG always includes the same 90 Hz component; a frequency component also present in the fERG response, suggesting a retinally-intrinsic origin. However, in addition, the fERGs also includes a low-frequency component which is absent in the rsERGs, a finding supporting a retinally-induced origin. Comparing rsERGs with fERGs in selected patients with various retinal disorders indicates that the two retinal signals are not always similarly affected (either as a result of underlying retinal pathology or otherwise), suggesting an added value in the assessment of retinal function. Thus, the rsERG could have a similar role in clinical visual electrophysiology as that of the resting-state EEG in neurology namely, to quantify changes in spontaneous activity that result from a given disease processes.

Functional Optical Coherence Tomography for Intrinsic Signal Optoretinography: Recent Developments and Deployment Challenges.

Intrinsic optical signal (IOS) imaging of the retina, also termed as optoretinogram or optoretinography (ORG), promises a non-invasive method for the objective assessment of retinal function. By providing the unparalleled capability to differentiate individual retinal layers, functional optical coherence tomography (OCT) has been actively investigated for intrinsic signal ORG measurements. However, clinical deployment of functional OCT for quantitative ORG is still challenging due to the lack of a standardized imaging protocol and the complication of IOS sources and mechanisms. This article aims to summarize recent developments of functional OCT for ORG measurement, OCT intensity- and phase-based IOS processing. Technical challenges and perspectives of quantitative IOS analysis and ORG interpretations are discussed.

Chromatic Full-Field Stimulus Thresholds in Patients with Treatment-Naive Age-Related Macular Degeneration.

PurposeTo evaluate retinal sensitivity using chromatic full-field stimulus thresholds (FST) in patients with treatment naive exudative age-related macular degeneration (e-ARMD) before and during the first intravitreal anti-vascular endothelial growth factor (anti-VEGF) treatment.Patients and MethodsAfter general ophthalmological examinations to diagnose patients with e-ARMD the FST, the central foveal thickness (FCt) and the visual acuity were assessed in 20 eyes of 20 patients during this prospective study. Examinations were performed before and during the first treatment series with three intravitreal anti-VEGF injections. Normal values for FST were assessed in 19 eyes of 19 healthy subjects. Results were analyzed using Student’s two-tailed t-test and Pearson’s correlation coefficients between all functional parameters.ResultsAt baseline and before the 1st intravitreal anti-VEGF treatment, a moderately significant negative correlation between VA and FCt was found in the e-ARMD group (p = 0.02, r = −0.45 and p = 0.03, r = −0.45), respectively. After the 2nd intravitreal anti-VEGF injection, no significant correlation between VA and FCt was found (p = 0.12). However, a significant correlation between FCt and blue FST was evident (p = 0.04, r = 0.4). After the 3rd intravitreal anti-VEGF treatment, there was no correlation evident between VA and FCt (p = 0.31) but a high significant correlation between FCt and FST using red (p = 0.01, r = 0.53), green (p = 0.002, r = 0.6) and blue light (p = 0.007, r = 0.66).ConclusionDuring anti-VEGF treatment in patients with e-ARMD, the FST test showed higher significant correlations with the morphology measured by FCt, as it is the case for VA. These findings support that the FST test might serve as a valuable diagnostic tool for monitoring patients with e-ARMD and enhance functional assessment of retinal function under treatment with anti-VEGF.

Prediction of glaucoma severity using parameters from the electroretinogram

Glaucoma is an optic neuropathy that results in the progressive loss of retinal ganglion cells (RGCs), which are known to exhibit functional changes prior to cell loss. The electroretinogram (ERG) is a method that enables an objective assessment of retinal function, and the photopic negative response (PhNR) has conventionally been used to provide a measure of RGC function. This study sought to examine if additional parameters from the ERG (amplitudes of the a-, b-, i-wave, as well the trough between the b- and i-wave), a multivariate adaptive regression splines (MARS; a non-linear) model and achromatic stimuli could better predict glaucoma severity in 103 eyes of 55 individuals with glaucoma. Glaucoma severity was determined using standard automated perimetry and optical coherence tomography imaging. ERGs targeting the PhNR were recorded with a chromatic (red-on-blue) and achromatic (white-on-white) stimulus with the same luminance. Linear and MARS models were fitted to predict glaucoma severity using the PhNR only or all ERG markers, derived from chromatic and achromatic stimuli. Use of all ERG markers predicted glaucoma severity significantly better than the PhNR alone (P ≤ 0.02), and the MARS performed better than linear models when using all markers (P = 0.01), but there was no significant difference between the achromatic and chromatic stimulus models. This study shows that there is more information present in the photopic ERG beyond the conventional PhNR measure in characterizing RGC function.

Macular Telangiectasia type 2: multimodal assessment of retinal function and microstructure.

To assess the impact of neurodegenerative morphologic alterations due to macular telangiectasia type 2 (MacTel) on microperimetry (MP) and multifocal electroretinography (mfERG). Thirty-five eyes of 18 patients with MacTel were examined using spectral domain optical coherence tomography (SD-OCT), fundus autofluorescence (FAF), mfERG and MP. Software was used to match SD-OCT B-scans with the corresponding retinal sensitivity map and multifocal electroretinograms (mfERGs), thus enabling direct structure/function correlation. Loss of the ellipsoid zone (EZ) had the strongest negative association with retinal sensitivity (16.77 dB versus 4.58 dB, adj. p < 0.001) of all parameters examined, and a limited negative effect on mfERGs (0.32 SD versus -1.97 SD adj. p = 0.121). Ellipsoid zone (EZ) irregularity was associated with reduced MP values but preserved mfERGs. There was a significant association between areas of inner retinal hyporeflectivity and loss of MP sensitivity (adj. p < 0.001) but the reduction in sensitivity was less than in locations with EZ loss. Areas of mfERG abnormality showed similar sensitivity loss with either inner retinal hyporeflectivity or EZ loss (adj. p = 0.063). In areas with EZ loss alone, preservation of the external limiting membrane (ELM) was associated with higher MP values than in areas with additional ELM loss; the integrity of the ELM alone was not associated with changes either in MP or mfERG. Increased FAF was observed in 51% of eyes, mixed/reduced FAF in 40%, and no abnormality was detected in 9% of eyes. The data suggest both MP and mfERG to be useful non-invasive modalities for detecting localised macular dysfunction in MacTel. The findings suggest a different sensitivity of the two modalities to inner and outer retinal changes in macular function and are therefore complementary.

Predictive value of retinal function by the Purkinje test in patients scheduled for cataract surgery in Kinshasa, DR Congo.

To assess the retinal function in patients with dense cataracts in resource poor settings in Kinshasa, DR Congo. In a tertiary eye care center, the Purkinje entoptic test was performed as part of the ophthalmological examination in 98 eyes in patients with cataract, using a penlight. Totally 92 cataract patients including 86 patients suffered from unilateral and 6 from bilateral cataracts were included in the study. The investigator asked the patients about their perception of the vascular pattern most commonly described as a leafless or dead tree. Visual acuity≥6/60 was considered an indication of good visual function and visual acuity<6/60 of poor function. Following small incision cataract surgery, best corrected visual acuity (BCVA) was determined and compared with the preoperative findings. Out of 98 eyes, there were 80 (81.6%) where the Purkinje entoptic phenomenon was reported by the patients. After cataract surgery, out of the 80 eyes, there were 75 (93.8%) with a BCVA of better than 6/60, whereas in 5 eyes (6.2%), BCVA was 6/60 or less. Out of the 18 eyes (18.4%) where no Purkinje tree was recognized, there were 14 (77.8%) with BCVA of better than 6/60, whereas in 4 (22.2%) BCVA was 6/60 or less. The Purkinje entoptic test is successfully used for preoperative assessment of retinal function in patients with dense cataract. However, further investigation and refinement of the test is necessary to validate the method for use in sub-Saharan conditions.

Functional optoretinography: concurrent OCT monitoring of intrinsic signal amplitude and phase dynamics in human photoreceptors.

Intrinsic optical signal (IOS) imaging promises a noninvasive method for objective assessment of retinal function. This study demonstrates concurrent optical coherence tomography (OCT) of amplitude-IOS and phase-IOS changes in human photoreceptors. A new procedure for differential-phase-mapping (DPM) is validated to enable depth-resolved phase-IOS imaging. Dynamic OCT revealed rapid amplitude-IOS and phase-IOS changes, which occur almost right away after the stimulus onset. These IOS changes were predominantly observed within the photoreceptor outer segment (OS), particularly two boundaries connecting to the inner segment and retinal pigment epithelium. The comparative analysis supports that both amplitude-IOS and phase-IOS attribute to transient OS morphological change associated with phototransduction activation in retinal photoreceptors. A simulation modeling is proposed to discuss the relationship between the photoreceptor OS length and phase-IOS changes.

Multifocal electroretinogram changes in patients with retinal vein occlusion

Background Retinal vein occlusion (RVO) is one of the most common vascular retinal disorders that lead to macular edema. There is often discrepancy between visual prognosis and optical coherence tomography (OCT) changes. Multifocal electroretinogram (mfERG) provides useful information about retinal function in affected parts of the retina in patients with RVO.Purpose The aim of this study was to assess the functional changes in patients with RVO by mfERG and to correlate these changes with OCT findings in those patients.Patients and methods This is a prospective study of 30 eyes of patients with RVO, with their fellow eyes being taken as control. Thirteen eyes with central RVO, 12 eyes with branch RVO, and five eyes with hemi-RVO were included in the study. OCT to measure the central macular thickness was done in all patients. mfERG was also done in all patients. P wave amplitude and p wave implicit times were measured in the central area and all quadrants.Results mfERG responses were markedly affected in all quadrants in central RVO, in the affected quadrants in branch RVO, and in the affected hemiretina in hemi-RVO. The differences between the p amplitude and p implicit time between the affected eyes and the fellow eyes were statistically significant in all patients. There was a significant correlation between the central macular thickness and p amplitude in the affected half of the retina in hemi-RVO.Conclusion mfERG is a sensitive tool for assessment of retinal function in patients with RVO. mfERG can assess local retinal dysfunction in patients with RVO, which is sensitive to morphological changes detected by OCT.

A longitudinal assessment of retinal function and structure in the APP/PS1 transgenic mouse model of Alzheimer\u2019s disease

BackgroundA great body of evidence suggests that there are retinal functional and structural changes that occur in Alzheimer’s disease (AD). However, whether such changes are primary or secondary remains to be elucidated. We studied a range of retinal functional and structural parameters in association with AD- specific pathophysiological markers in the double transgenic APP/PS1 and control mice across age.MethodsElectroretinogram (ERG) and optical coherence tomography (OCT) was performed in APP/PS1 and wild type (WT) control mice every 3 months from 3 to 12 months of age. For functional assessment, the a- and b-wave of the ERG, amplitude of oscillatory potentials (OP) and the positive scotopic threshold response (pSTR) were quantified at each time point. For structural assessment, the inner and outer retinal thickness was segmented and measured from OCT scans. Episodic memory was evaluated at 6, 9 and 12 months of age using the novel object recognition test. Amyloid beta (Aβ) distribution in the hippocampus and the retina were visualised at 3, 6 and 12 months of age. Inter- and intra- group analysis was performed to study rate of change for each parameter between the two groups.ResultsInter-group analysis revealed a significant difference in b-wave and OPs of APP/PS1 compared to WT controls starting from 3 months (p < 0.001). There was also a significant difference in the amplitude of pSTR between the two groups starting from 6 months (p < 0.001). Furthermore, a significant difference in the inner retinal thickness, between the two groups, was observed starting from 9 months (p < 0.001).ConclusionsWe observed an age-related decline in retinal functional and structural parameters in both APP/PS1 and WT controls, however, inter-group analysis revealed that inner retinal functional and structural decline is exacerbated in APP/PS1 mice, and that retinal functional changes precede structural changes in this strain. Further studies are required to confirm whether such phenomenon occurs in humans and if studying retinal functional changes can aid-in early assessment of AD.

Electroretinography in small animal practice

During the last years, clinical electrophysiology has considerably improved, allowing the evaluation of the retina and visual pathways. In small animal practice, electroretinography is more useful than other diagnostic techniques for the assessment of retinal function, because of the fact that this method doesn't require patient's cooperation. Electroretinography (ERG) is an electrophysiological technique, which measures the retinal action potentials in response to light stimulation. Flash ERG evaluates the function of outer retina and is performed by the using of flashlight units that uniformly stimulate the retina. The evaluation of ERG requires the well understanding of the morphology as well as the physiologic function of the retina. Furthermore, a number of factors, which can influence the quality of the ERG, are totally controlled during the procedure. Because of the fact that electroretinographic values vary, according to many factors and different diagnostic protocols, comparison of results, obtained from different laboratories, would be difficult. Therefore, each veterinary ERG laboratory obtains its own normal values. ERG is indicated, when retinal disease is suspected. ERG can also help to identify the cause of blindness. In small animal practice, the majority of ERGs are performed on candidates for cataract surgery. Other ERG indications include the early diagnosis of central or generalized progressive retinal atrophy (PRA), the differential diagnosis between the sudden acquired retinal degeneration (SARD) and optic neuritis, the glaucoma and many cases of retinal detachments. Furthermore, ERG is used to evaluate the progression of many retinal disorders.

Macular Sensitivity Measured With Microperimetry in Stargardt Disease in the Progression of Atrophy Secondary to Stargardt Disease (ProgStar) Study

New outcome measures for treatment trials for Stargardt disease type 1 (STGD1) and other macular diseases are needed. Microperimetry allows mapping of light sensitivity of the macula and provides topographic information on visual function beyond visual acuity. To measure and analyze retinal light sensitivity of the macula in STGD1 using fundus-controlled perimetry (microperimetry). This was a multicenter prospective cohort study. A total of 199 patients and 326 eyes with molecularly confirmed (ABCA4) STGD1 underwent testing with the Nidek MP-1 microperimeter as part of the multicenter, prospective Natural History of the Progression of Atrophy Secondary to Stargardt Disease (ProgStar) study. Sensitivity of 68 retinal loci was tested, and the mean sensitivity (MS) was determined; each point was categorized as "normal," "relative," or "deep" scotoma. Mean sensitivity and the number of points with normal sensitivity, relative, or deep scotomas. Mean (SD) patient age was 34.2 (14.7) years, mean (SD) best-corrected visual acuity of all eyes was 47.8 (16.9) Early Treatment Diabetic Retinopathy Study letter score (approximately 20/100 Snellen equivalent), and mean MS of all eyes of all 68 points was 11.0 (5.0) dB. The median number of normal points per eye was 49 (mean [SD], 41.3 [20.8]; range, 0-68); abnormal sensitivity and deep scotomas were more prevalent in the central macula. Mean sensitivity was lower in the fovea (mean [SD], 2.7 [4.4] dB) than in the inner (mean [SD], 6.8 [5.8] dB) and outer ring (mean [SD], 12.7 [5.3] dB). Overall MS per eye was 0.086 dB lower per year of additional age (95% CI, -0.13 to -0.041; P < .001) and 0.21 dB lower per additional year of duration of STGD1 (95% CI, -0.28 to -0.14; P < .001). Longer duration of STGD1 was associated with worse MS (β = -0.18; P < .001), with a lower number of normal test points (β = -0.71; P < .001), and with a higher number of deep scotoma points (β = -0.70; P < .001). We found 11 eyes with low MS (<6 dB) but very good best-corrected visual acuity of at least 72 Early Treatment Diabetic Retinopathy Study letter score (20/40 Snellen equivalent). We provide an extensive analysis of macular sensitivity parameters in STGD1 and demonstrate their association with demographic characteristics and vision. These data suggest microperimetry testing provides a more comprehensive assessment of retinal function and will be an important outcome measure in future clinical trials.

Therapeutic efficacy of isavuconazole in experimental Aspergillus fumigatus endophthalmitis

BackgroundFungal endophthalmitis remains a significant cause of vision impairment and blindness with poor prognosis, in part, due to delay in diagnosis and limited availability of antifungal agents without ocular toxicity. Thus, it is imperative to evaluate the therapeutic efficacy of newer antifungal agents such as Isavuconazole in fungal endophthalmitis.Methods Aspergillus fumigatus (AF) endophthalmitis was induced by intravitreal (IVT) injection of AF spores in C57BL/6 mice eyes. Therapeutic efficacy of isavuconazole was evaluated by administering the drug in five treatment groups (1) oral gavage, (2) IVT injections, (3) intravenous, (4) IVT injection followed by oral gavage, and (5) IVT injection followed by intravenous. In all treatment groups, isavuconazole therapy was starting at 6 h post AFinfection and continued daily for a maximum of three-day post infection (dpi). Disease progression was monitored by daily eye exam and the assessment of retinal function using the electroretinogram (ERG) diagnostic test. Enucleated eyes were used for histology and the determination of fungal burden and inflammatory cytokines.ResultsIn comparison to placebo, isavuconazole treatment significantly (P < 0.001) retained retinal function in all treatment groups. This coincided with preservation of retinal architecture (histology analysis) and reduction in fungal burden and intraocular inflammation. Among various treatment groups, daily oral administration of isavuconazole alone was as effective as IVT alone, as evidenced by significant (P < 0.0001) inhibition of inflammatory cytokine levels (TNF-α, IL-1β, IL-6), drastic (P < 0.0001) reduction in fungal burden and retinal tissue damage, culminating in significant (P < 0.001) retention of retinal function (ERG response). Moreover, oral isavuconazole combined with single IVT injection also seems to be highly effective in comparison with IVT+ intravenous delivery of the drug.ConclusionIn this first proof-of-principle study, we show that isavuconazole can be potentially used for the treatment of fungal (Aspergillus) endophthalmitis. Moreover, the better efficacy of oral administration alone may avoid the need for an invasive procedure (IVT injection) to deliver antifungal agents into the eye.Disclosures A. Kumar, Astellas Pharma Global Development, Inc.: Grant Investigator, Research grant

Fixation Location and Stability Using the MP-1 Microperimeter in Stargardt Disease: ProgStar Report No. 3

To determine fixation location and fixation stability in Stargardt disease (STGD1) and their association with best-corrected visual acuity (BCVA). Cross-sectional analysis within the multicenter, prospective ProgStar study. A total of 238 patients and 440 eyes with ABCA4-related STGD1. Patients underwent testing with the Nidek MP-1 microperimeter (Nidek Technologies Inc., Gamagōri, Japan). Fixation location was expressed as the eccentricity of the preferred retinal locus (PRL) from the anatomic fovea, fixation stability was expressed as the bivariate contour ellipse area (BCEA), and BCVA was expressed as Early Treatment Diabetic Retinopathy Study (ETDRS) letters. Linear models with generalized estimating equations were used for statistical analysis while accounting for between-eye correlations. Fixation location and fixation stability. Median PRL eccentricity from the fovea was 6° (mean, 6.3°; range, 0°-25°) and median BCEA was 6.31°2 (mean, 12.31°2; range, 0.03°2-365.63°2). Each year of later onset of symptoms of STGD1 was associated with 0.14° more central fixation location (P < 0.0001), but not with fixation stability (P= 0.53). A single linear model best described the relationship between fixation location and BCVA: 1° farther PRL eccentricity was associated with a 2.3-letter loss of BCVA (P < 0.0001). A piecewise linear model best described the relationship between fixation stability and BCVA: for a BCEA less than 2.8°2, an increase in BCEA by 1°2 was associated with a 10.5-letter (ETDRS) lower BCVA (P < 0.0001). For a BCEA 2.8°2 or more, an increase in BCEA by 1°2 was associated with a 0.036-letter (ETDRS) lower BCVA (P= 0.0234). Pearson correlation coefficients between patients' right and left eyes were 0.89 (P < 0.0001) for fixation location and 0.25 (P= 0.0006) for fixation stability. After 10 years of disease duration, 82% of patients had eccentric PRLs in both eyes. We provide the first extensive database of continuous fixation parameters in STGD1 and demonstrate their association with vision. These measures allow for a more comprehensive assessment of retinal function and may serve as potential secondary outcome measures for future treatment trials for STGD1 and other macular diseases.

Photoreceptor Integrity Predicts Response to Anti-VEGF Treatment

Purpose: Assessing changes in foveal photoreceptor microstructure (FPM) following intravitreal anti-VEGF treatment may serve as a prognostic marker in patients with macular edema (ME). Methods: Sixteen eyes belonging to newly diagnosed patients with ME were included in this prospective longitudinal study. FPM integrity was evaluated at baseline and at the end of a series of anti-VEGF injections. Results: Treatment led to a significant improvement in mean visual acuity (VA) and central macular thickness. A larger FPM defect was associated with lower VA, both before and after treatment. Patients with larger FPM defects at baseline had smaller VA improvements, and the improvement in FPM integrity was associated with VA improvement (every 100-µm FPM recovery contributed to a gain of 0.04 logMAR). Conclusions: Recovery of FPM after anti-VEGF treatment was significantly associated with a VA improvement. Direct measurement of photoreceptor integrity might provide an additional tool for the assessment of retinal function and treatment response in patients newly diagnosed with ME.

Glucose variability and inner retinal sensory neuropathy in persons with type 1 diabetes mellitus.

PurposeTo quantify early neuroretinal alterations in patients with type 1 diabetes mellitus (T1DM) and to assess whether glycemic variability contributes to alterations in neuroretinal structure or function.MethodsThirty patients with T1DM and 51 controls underwent comprehensive ophthalmic examination and assessment of retinal function or structure with frequency doubling perimetry (FDP), contrast sensitivity, dark adaptation, fundus photography, and optical coherence tomography (OCT). Diabetic participants wore a subcutaneous continuous glucose monitor for 5 days, from which makers of glycemic variability including the low blood glucose index (LGBI) and area under the curve (AUC) for hypoglycemia were derived.ResultsSixteen patients had no diabetic retinopathy (DR), and 14 had mild or moderate DR. Log contrast sensitivity for the DM group was significantly reduced (mean±SD=1.63±0.06) compared with controls (1.77±0.13, P<0.001). OCT analysis revealed that the inner temporal inner nuclear layer (INL) was thinner in patients with T1DM (34.9±2.8 μm) compared with controls (36.5±2.9 μm) (P=0.023), although this effect lost statistical significance after application of the Bonferroni correction for multiple comparisons. Both markers of glycemic variability, the AUC for hypoglycemia (R=-0.458, P=0.006) and LGBI (R=-0.473, P=0.004), were negatively correlated with inner temporal INL thickness.ConclusionsPatients with T1DM and no to moderate DR exhibit alterations in inner retinal structure and function. Increased glycemic variability correlates with retinal thinning on OCT imaging, suggesting that fluctuations in blood glucose may contribute to neurodegeneration.

Mthfr as a modifier of the retinal phenotype of Crb1rd8/rd8 mice

Mutations in crumb homologue 1 (CRB1) in humans are associated with Leber's congenital amaurosis (LCA) and retinitis pigmentosa (RP). There is no clear genotype–phenotype correlation for human CRB1 mutations in RP and LCA. The high variability in clinical features observed in CRB1 mutations suggests that environmental factors or genetic modifiers influence severity of CRB1 related retinopathies. Retinal degeneration 8 (rd8) is a spontaneous mutation in the Crb1 gene (Crb1rdr/rd8). Crb1rdr/rd8 mice present with focal disruption in the outer retina manifesting as white spots on fundus examination. Mild retinal dysfunction with decreased b-wave amplitude has been reported in Crb1rdr/rd8 mice at 18 months. Methylene tetrahydrofolate reductase (MTHFR) is a crucial enzyme of homocysteine metabolism. MTHFR mutations are prevalent in humans and are linked to a broad spectrum of disorders including cardiovascular and neurodegenerative diseases. We recently reported the retinal phenotype in Mthfr-deficient (Mthfr+/−) heterozygous mice. At 24 weeks the mice showed decreased RGC function, thinner nerve fiber layer, focal areas of vascular leakage and 20% fewer cells in the ganglion cell layer (GCL). Considering the variability in CRB1-related retinopathies and the high occurrence of human MTHFR mutations we evaluated whether Mthfr deficiency influences rd8 retinal phenotype. Mthfr heterozygous mice with rd8 mutations (Mthfr+/−rd8/rd8) and Crbrd8/rd8 mice (Mthfr+/+rd8/rd8) mice were subjected to comprehensive retinal evaluation using ERG, fundoscopy, fluorescein angiography (FA), morphometric and retinal flat mount immunostaining analyses of isolectin-B4 at 8–54 wks. Assessment of retinal function revealed a significant decrease in the a-, b- and c-wave amplitudes in Mthfr+/−rd8/rd8 mice at 52 wks. Fundoscopic evaluation demonstrated the presence of signature rd8 spots in Mthfr+/+rd8/rd8 mice and an increase in the extent of these rd8 spots in Mthfr+/−rd8/rd8 mice at 24 weeks and beyond. FA revealed marked vascular leakage, ischemia and vascular tortuosity in Mthfr+/−rd8/rd8 mice at 24 and 52 weeks. Retinal dysplasia was observed in ∼14–33% Mthfr+/−rd8/rd8 mice by morphometric analysis. This was accompanied by a ∼20% reduction in cells of the GCL of Mthfr+/−rd8/rd8 mice at 24 and 52 weeks. Retinal flat mount immunostaining with isolectin-B4 showed neovascularization and loss of blood vessel integrity in Mthfr+/−rd8/rd8 mice in contrast to mild vasculopathy in Mthfr+/+rd8/rd8 mice. Taken together, our data support an earlier onset and worsened retinal phenotype when Mthfr and rd8 mutations coexist. Our study sets the stage for future studies to investigate the role of MTHFR deficiency in human CRB1 retinopathies.

Exercise and Cyclic Light Preconditioning Protect Against Light-Induced Retinal Degeneration and Evoke Similar Gene Expression Patterns.

To compare patterns of gene expression following preconditioning cyclic light rearing versus preconditioning aerobic exercise. BALB/C mice were preconditioned either by rearing in 800lx 12:12h cyclic light for 8 days or by running on treadmills for 9 days, exposed to toxic levels of light to cause light-induced retinal degeneration (LIRD), then sacrificed and retinal tissue harvested. Subsets of mice were maintained for an additional 2 weeks and for assessment of retinal function by electroretinogram (ERG). Both preconditioning protocols partially but significantly preserved retinal function and morphology and induced similar leukemia inhibitory factor (LIF) gene expression pattern. The data demonstrate that exercise preconditioning and cyclic light preconditioning protect photoreceptors against LIRD and evoke a similar pattern of retinal LIF gene expression. It may be that similar stress response pathways mediate the protection provided by the two preconditioning modalities.