Longitudinal evaluation of the distribution of intraretinal hyper-reflective foci in eyes with intermediate age-related macular degeneration

Purpose

Intraretinal hyper-reflective foci (IHRF) are optical coherence tomography (OCT) risk factors for progression of age-related macular degeneration (AMD). In this study we assess the change in the number and distribution of IHRF over two years.

Methods

The axial distribution of IHRF were quantified in eyes with intermediate AMD (iAMD) at baseline and 24 months, using a series of 5 sequential equidistant en face OCT retinal slabs generated between the outer border of the internal limiting membrane (ILM) and the inner border of the retinal pigment epithelium (RPE). Following thresholding and binarization, IHRF were quantified in each retinal slab using ImageJ. The change in IHRF number in each slab between baseline and month 24 was calculated.

Results

Fifty-two eyes showed evidence of IHRF at baseline, and all continued to show evidence of IHRF at 24 months (M24). The total average IHRF count/eye increased significantly from 4.67 ± 0.63 at baseline to 11.62 ± 13.86 at M24 (p<0.001) with a mean increase of 6.94 ± 11.12 (range: - 9 to + 60). Overall, at M24, 76.9% eyes showed an increase in IHRF whereas 15.4% of eyes showed a decrease (4 eyes [7.6%] showed no change). There was a greater number of IHRF and a greater increase in IHRF over M24 in the outer slabs.

Conclusions

IHRF are most common in the outer retinal layers and tend to increase in number over time. The impact of the distribution and frequency of these IHRF on the overall progression of AMD requires further study.

NOVEL RETINAL IMAGING ABNORMALITIES IN ALPORT SYNDROME

PURPOSE

The purpose of this study was to report a novel observation during retinal screening of a child with Alport syndrome.

METHODS

This was a review of case record and imaging files.

RESULTS

Clinical examination of the retina and standard color fundus photography revealed no abnormality. However, distinct and identical wrinkling of the temporal macula (fingerprint sign) in both eyes was noted on Optos pseudocolor images of the retina. On optical coherence tomography, there were corresponding "saw-tooth" corrugations in the middle layers of the retina. En face images further highlighted the characteristic nature of this unusual observation.

CONCLUSION

Fingerprint sign in the retina, a heretofore undescribed feature, is reported in a child with biopsy confirmed Alport syndrome.

Polypoidal Choroidal Vasculopathy: Updates on Risk Factors, Diagnosis, and Treatments

There have been recent advances in basic research and clinical studies in polypoidal choroidal vasculopathy (PCV). A recent, large-scale, population-based study found systemic factors, such as male gender and smoking, were associated with PCV, and a recent systematic review reported plasma C-reactive protein, a systemic biomarker, was associated with PCV. Growing evidence points to an association between pachydrusen, recently proposed extracellular deposits associated with the thick choroid, and the risk of development of PCV. Many recent studies on diagnosis of PCV have focused on applying criteria from noninvasive multimodal retinal imaging without requirement of indocyanine green angiography. There have been attempts to develop deep learning models, a recent subset of artificial intelligence, for detecting PCV from different types of retinal imaging modality. Some of these deep learning models were found to have high performance when they were trained and tested on color retinal images with corresponding images from optical coherence tomography. The treatment of PCV is either a combination therapy using verteporfin photodynamic therapy and anti-vascular endothelial growth factor (VEGF), or anti-VEGF monotherapy, often used with a treat-and-extend regimen. New anti-VEGF agents may provide more durable treatment with similar efficacy, compared with existing anti-VEGF agents. It is not known if they can induce greater closure of polypoidal lesions, in which case, combination therapy may still be a mainstay. Recent evidence supports long-term follow-up of patients with PCV after treatment for early detection of recurrence, particularly in patients with incomplete closure of polypoidal lesions.

Progression of Stargardt Disease as Determined by Fundus Autofluorescence Over a 24-Month Period (ProgStar Report No. 17)

PURPOSE

To estimate the progression rate of atrophic lesions in Stargardt disease derived from fundus autofluorescence (FAF).

DESIGN

International, multicenter, prospective cohort study.

METHODS

A total of 259 participants aged ≥6 years with disease-causing variants in the ABCA4 gene were enrolled from 9 centers and followed over a 24-month period. FAF images were obtained every 6 months, and areas of definitely decreased autofluorescence (DDAF) and decreased autofluorescence (DAF) were quantified. Progression rates were estimated from linear mixed models with time as the independent variable.

RESULTS

A total of 488 study eyes of 259 participants (88.8% with both eyes) were enrolled and images from 432 eyes were followed for 24 months. The overall estimated progression of DDAF was 0.74 mm²/y (95% CI 0.64-0.85, P < .0001) and that of DAF was 0.64 mm²/y (95% CI 0.57-0.71) over a 24-month period in univariate analysis. Growth rates were strongly dependent on baseline lesion area. After square root transformation, the DDAF growth rate was not dependent on baseline lesion radius (P = .11), whereas the DAF growth rate was dependent (P < .0001). Genotype was not found to significantly impact the growth rate of DDAF or DAF lesions.

CONCLUSIONS

FAF may serve as a convenient monitoring tool and suitable end point for interventional clinical trials that aim to slow disease progression. DDAF and DAF lesion sizes at baseline are strong predicting factors for lesion area growth and can be partially accounted for by square root transformation.

Effect of Residual Retinal Fluid on Visual Function in Ranibizumab-Treated Neovascular Age-Related Macular Degeneration

PURPOSE

To investigate the relationship between retinal fluid and vision in ranibizumab-treated patients with neovascular age-related macular degeneration (nAMD).

DESIGN

Clinical cohort study using post hoc analysis of clinical trial data.

METHODS

We assessed data from HARBOR (NCT00891735), a phase III, randomized, controlled trial. We reviewed 917 patients ≥50 years of age with subfoveal nAMD associated with subretinal (SRF) and/or intraretinal fluid (IRF) at baseline, screening, or week 1. The intervention was intravitreal ranibizumab 0.5 or 2.0 mg (all treatment arms pooled). Outcomes included mean best-corrected visual acuity (BCVA) and BCVA change from baseline at months (M) 12 and 24 evaluated by the presence/absence of SRF and/or IRF.

RESULTS

Baseline BCVA was higher with residual vs resolved SRF at M12 (mean [95% confidence interval {CI}] 58.8 letters [57.2-60.4] vs 53.5 [52.4-54.5]) and M24 (59.3 letters [57.8-60.8] vs 53.5 [52.5-54.5]). Mean BCVA change (adjusted for baseline) to M12 was greater with residual vs resolved SRF (mean difference [95% CI], +2.4 letters [+0.1 to +4.7]), but lower with residual vs resolved IRF (-3.5 letters [-5.8 to -1.2]). Eyes with residual SRF (no IRF) exhibited the largest mean BCVA gains (M12, +14.1 letters; M24, +13.2 letters), followed by resolved SRF/IRF (M12, +10.6 letters; M24, +10.0 letters), residual SRF/IRF (M12, +7.2 letters; M24, +8.5 letters), and residual IRF only (M12, +5.5 letters; M24, +3.6 letters).

CONCLUSIONS

Vision outcomes (adjusted for baseline BCVA) through M24 were better in ranibizumab-treated eyes with residual vs resolved SRF, and worse with residual vs resolved IRF. Presence of residual retinal fluid requires a more complex and nuanced assessment and interpretation in the context of nAMD management.

Outer Retinal Folds Following Pars Plana Vitrectomy vs Pneumatic Retinopexy for Retinal Detachment Repair: Post Hoc Analysis from PIVOT

PURPOSE

To assess the incidence of post-operative outer retinal folds (ORFs) in pars plana vitrectomy (PPV) vs pneumatic retinopexy (PnR) following rhegmatogenous retinal detachment (RRD) repair and to determine the association of ORFs with functional outcomes at 1 year.

DESIGN

Randomized controlled trial PARTICIPANTS: Patients with primary macula-off RRD meeting PIVOT trial criteria randomly assigned to PPV vs PnR.

METHODS

Post-hoc analysis of the PIVOT trial. Incidence and quantitative morphological features of ORFs were assessed with en face and cross-sectional OCT at 1 month post-operatively by two masked graders. ETDRS letter score and quantitative metamorphopsia were measured at 1 year.

MAIN OUTCOME MEASURES

Proportion of patients with ORFs following PPV vs PnR at 1 month post-operatively. Secondary outcomes include the association of ORFs with visual acuity (ETDRS letter score) and metamorphopsia (M-CHARTS) at 12 months post-operatively.

RESULTS

Eighty-eight of the 176 participants enrolled in PIVOT were macula-off RRD. 94.3% (83/88) of these macula-off eyes had month 1 post-operative OCT scans that were gradable, 93.2% (41/44) in the PPV group and 95.5% (42/44) in the PnR group. The incidence of ORFs formation was 34.1% (14/41) in the PPV group and 14.3% (6/42) in the PnR group (p=0.034). ETDRS letter score at 1 year was 65.7±6.6 letters in patients with ORFs versus 75.1±1.4 letters in those without ORFs (difference=9.4 letters, 95% CI=7.5-11.3, p=0.047). Among patients in the PPV group only, mean ETDRS letter score at 1 year in patients with ORFs was 62.8 ± 24.7 letters compared to 75.4 ± 9.2 letters in patients without ORF formation (difference=12.6 letters, 95% CI=0.05-24.59, p=0.04). Horizontal and vertical metamorphopsia scores were similar in patients with vs without ORFs: horizontal: 0.35 ± 0.12 versus 0.29 ± 0.07 (difference=0.06, 95% CI=0.01-0.11, p=0.69) and vertical: 0.25±0.07 versus 0.29±0.07 (difference=0.04, 95%CI=0-0.08, p=0.60) respectively. There was a negative correlation between the closest distance of the ORFs from the fovea and the vertical metamorphopsia score (r=-0.507, p=0.045).

CONCLUSIONS

There is a greater risk of developing ORFs following PPV compared to PnR for RRD. ORFs at 1 month are associated with significantly worse ETDRS visual acuity letter score at 1 year.

En Face Optical Coherence Tomography Imaging of Foveal Dots in Eyes With Posterior Vitreous Detachment or Internal Limiting Membrane Peeling

Purpose

To analyze the morphology of foveal hyperreflective dots (HRD) identified with en face optical coherence tomography (OCT) and evaluate the effects of internal limiting membrane (ILM) peeling and posterior vitreous detachment (PVD) on the number of these lesions.

Methods

Retrospective cross-sectional study of patients with OCT angiography and en face OCT. Using en face OCT, superficial HRD lying on the foveal floor were measured and quantitated in eyes with ILM peel and in the fellow nonsurgical eyes. Eyes with foveal PVD were also compared to fellow eyes without foveal PVD. High-magnification en face OCT was also performed to better understand the morphology of HRD in the fovea.

Results

Eyes that underwent ILM peel (n = 10) displayed fewer HRD (P = 0.012) compared to control fellow nonoperated eyes. In eyes with foveal PVD, the mean number of HRD was numerically greater, but without statistical significance, compared to the contralateral eye without foveal PVD. High-magnification en face OCT illustrated HRD with irregular shapes and fine cilia-like or dendriform extensions. Average length of HRD was between 15 to 21 µm in all four groups.

Conclusions

HRD decreased in eyes with ILM peeling by en face OCT compared with fellow nonoperated eyes and exhibited a glial cell-like morphology and size closely resembling the white dot fovea described previously using scanning electron microscopy. HRD may represent processes of activated retinal glia, possibly Muller cells, that traverse defects in the ILM.

Clinical Update on Metamorphopsia: Epidemiology, Diagnosis and Imaging

Purpose: To discuss the pathophysiology of metamorphopsia, its characterisation using retinal imaging and methods of assessment of patient symptoms and visual function.Methods: A literature search of electronic databases was performedResults: Metamorphopsia has commonly been associated with vitreomacular interface disorders (such as epiretinal membrane) and has also regularly been noted in diseases of the retina and choroid, particularly age-related macular degeneration and central serous chorioretinopathy. Developments in optical coherence tomography retinal imaging have enabled improved imaging of the foveal microstructure and have led to the localisation of the pathophysiology of metamorphopsia within the retinal layers of the macula. Alteration of alignment of inner and outer retinal layers at various retinal loci has been identified using multimodal imaging in patients with metamorphopsia in a range of conditions. Although the Amsler Grid assessment of metamorphopsia is a useful clinical indicator, new emerging methods of metamorphopsia assessment with psychophysical tests such as M-CHARTS and preferential hyperacuity perimetry, have been developed.Conclusions: It appears that there is a complex relationship between visual acuity and metamorphopsia symptoms that vary between retinal conditions. Although metamorphopsia has traditionally been challenging to measure in the clinic, advances in technology promise more robust, easy-to-use tests. It is possible that home assessment of metamorphopsia, particularly in conditions such as age-related macular degeneration, may help to guide the need for further clinic evaluation and consideration of treatment.

Visualizing and understanding inherent features in SD-OCT for the progression of age-related macular degeneration using deconvolutional neural networks

To develop a convolutional neural network visualization strategy so that optical coherence tomography (OCT) features contributing to the evolution of age-related macular degeneration (AMD) can be better determined. We have trained a U-Net model to utilize baseline OCT to predict the progression of geographic atrophy (GA), a late stage manifestation of AMD. We have augmented the U-Net architecture by attaching deconvolutional neural networks (deconvnets). Deconvnets produce the reconstructed feature maps and provide an indication regarding the inherent baseline OCT features contributing to GA progression. Experiments were conducted on longitudinal spectral domain (SD)-OCT and fundus autofluorescence images collected from 70 eyes with GA. The intensity of Bruch's membrane-outer choroid (BMChoroid) retinal junction exhibited a relative importance of 24%, in the GA progression. The intensity of the inner retinal pigment epithelium (RPE) and BM junction (InRPEBM) showed a relative importance of 22%. BMChoroid (where the AMD feature/damage of choriocapillaris was included) followed by InRPEBM (where the AMD feature/damage of RPE was included) are the layers which appear to be most relevant in predicting the progression of AMD.

Evaluation of retinal vessel quantity within individual retinal structural layers using optical coherence tomography angiography

PURPOSE

To evaluate retinal vessel quantity within various retinal structural layers using optical coherence tomography angiography (OCTA).

METHODS

In this IRB-approved study, 22 normal eyes (from 22 subjects) were imaged using the Spectralis OCT2, with a 15 × 15 degree OCTA scan centered on fovea and two additional 15 × 5 degree OCTA scans, displaced temporally and nasally by 15 degrees along the fovea-Bruch's membrane opening (BMO) axis. Following projection artifact removal (PAR), vessel quantity (i.e., amount of flow signal) within each retinal nuclear and plexiform layer was assessed across the scan and was plotted as a vessel quantity profile over this fovea-BMO axis. Vessel quantity was correlated against the retinal layer thickness at the corresponding locations using the Spearman correlation.

RESULTS

For the nerve fiber layer (NFL), the vessel quantity was highest nasally and declined towards the fovea and was near zero temporal to the fovea with or without PAR. For all other retinal layers, the retinal vessel quantities were greatest in the parafoveal retina, peaking approximately 5 degrees from the foveal center. Before PAR, the parafoveal vessel quantity was highest in the inner plexiform layer (IPL). Following PAR, the vessel quantity in the IPL decreased but was relatively unchanged in the other layers. The vessel quantity correlated moderately well with retinal layer thickness (r = 0.432 to 0.511; P < 0.05 among the various layers).

CONCLUSIONS

Retinal vessel quantity varies significantly among the various structural layers, with significant regional variability. Projection artifact can significantly impact retinal vessel quantity in the deeper layers, but the effect appears to be most pronounced in the IPL.

Near-Infrared Reflectance Imaging for Quantification of Atrophy Associated with Age-Related Macular Degeneration

PURPOSE

To compare measurements of area of geographic atrophy (GA) in dry age-related macular degeneration (AMD) obtained by fundus autofluorescence (FAF) to those obtained by near-infrared reflectance (NIR).

DESIGN

Interrater reliability analysis.

METHODS

Ninety-seven confocal NIR images (Heidelberg HRA + Spectralis) and FAF images from 97 patients/eyes with GA with dry AMD were collected retrospectively from existing anonymized Doheny Image Reading Center datasets. Two masked reading center graders (N.S., J.S.) independently and blindly performed manual segmentation of the GA lesions on each NIR and FAF image using GNU Image Manipulation Program software (version 2.8.22). GA on NIR/FAF images was defined in accordance to recently published Classification of Atrophy Meeting criteria as sharply demarcated hyperreflective regions ≥250 μm in diameter. The difference and point-to-point correspondence between gradings in GA area measurements between NIR and FAF were assessed by mean difference, overlap ratio, and Dice similarity coefficient.

RESULTS

Among the 97 eyes with dry AMD, the mean GA area was 7.62 ± 7.77 mm² from FAF images and 7.65 ± 7.83 mm² from NIR, with a mean nonsignificant difference of 0.31 ± 0.55 mm² (2-tailed t test, P = .65). The overlap ratio in the segmented GA lesion between modalities was 0.84 ± 0.28 with a Dice similarity coefficient of 0.87 ± 0.27. Intermodal reliability was high (intraclass correlation coefficient = 0.998, P < .01). Of note, in 5 cases (5.2%), the GA lesion could be identified on the FAF image but not on the NIR image, translating into a sensitivity of 94.8%.

CONCLUSIONS

GA lesions in dry AMD can be identified and quantified reliably using NIR images in many cases, though eyes with a thin choroid resulting in isoreflective GA lesions may be challenging. NIR imaging is comfortable for patients and is commonly obtained along with OCT, and therefore NIR-based GA assessment may be a useful surrogate in clinical settings.

En Face OCT of Type 2 Neovascularization:A Reappraisal of the Pitchfork Sign

BACKGROUND AND OBJECTIVES

To describe a new en face optical coherence tomography (OCT) imaging feature of type 2 choroidal neovascularization (CNV) and illustrate the OCT angiographic (OCTA) findings in these eyes.

PATIENTS AND METHODS

Multimodal images of patients with type 2 CNV who displayed the typical "pitchfork" sign with cross-sectional OCT were reviewed. Corresponding en face structural OCT and OCTA images were analyzed to correlate the finding before and after anti-vascular endothelial growth factor (VEGF) therapy.

RESULTS

Five eyes of five patients, including two females and three males with a median age of 13 years (range: 8 years to 84 years), were studied. The etiology for type 2 CNV was laser-induced maculopathy in two eyes, idiopathic in two eyes, and age-related macular degeneration in one eye. None of the eyes had evidence of inflammatory ocular disease. En face OCT displayed a characteristic wreath-like pattern of hyperreflective spikes surrounding the type 2 neovascular membrane that originated from the ellipsoid zone and extended into the outer nuclear layer. Wreath-like spikes resolved with intravitreal anti-VEGF injection with good visual outcomes and transformation of the neovascular lesion from a type 2 to type 1 morphology.

CONCLUSIONS

Type 2 CNV associated with the pitchfork sign with cross-sectional OCT displayed a characteristic wreath-like pattern of hyperreflective spikes with en face OCT that resolved with anti-VEGF therapy. This form of type 2 neovascularization may occur in eyes with different underlying etiologies and without signs of intraocular inflammation and is not limited to pediatric patients. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:719-725.].

Pharmacotherapeutic management of macular edema in diabetic subjects undergoing cataract surgery

INTRODUCTION

Cataracts and diabetes are widespread pathologies that are of growing concern to the global population. In diabetic patients who have had cataract surgery, the worsening of preexisting diabetic macular edema or occurrence of pseudophakic cystoid macular edema are common causes of visual impairment even with the most advanced surgical techniques available today for phacoemulsification.

AREAS COVERED

In this review, the authors assess the available literature to evaluate and compare different drugs, with the aim of establishing the best pharmacological strategies for the prevention and treatment of macular edema in diabetic patients undergoing cataract surgery.

EXPERT OPINION

Guidelines for the optimal management of diabetic macular edema in conjunction with cataract surgery or treatment of pseudophakic cystoid macular edema in diabetic patients are still lacking. To treat these conditions, clinicians need to understand the pharmacokinetics, posology, and efficacy of available drugs: topical non-steroidal anti-inflammatory drugs (NSAIDs), intravitreal anti-vascular endothelial growth factors (VEGFs), and both topical and intravitreal steroids. Diabetic patients undergoing cataract surgery should receive topical NSAIDs to prevent pseudophakic cystoid macular edema. Intravitreal anti-VEGFs and steroids, in association with cataract surgery, are indicated for patients with preexisting diabetic macular edema or those at high risk of macular edema after surgery.

Distinct Retinal Capillary Plexuses in Normal Eyes as Observed in Optical Coherence Tomography Angiography Axial Profile Analysis

Optical coherence tomography angiography (OCTA) allows the retinal microvasculature to be visualized at various retinal depths. Previous studies introduced OCTA axial profile analysis and showed regional variations in the number and location of axially distinct vascular retinal plexuses. OCTA acquisition and processing approaches, however, vary in terms of their resulting transverse and axial resolutions, and especially the latter could potentially influence the profile analysis results. Our study imaged normal eyes using the Spectralis OCT2 with a full-spectrum, probabilistic OCTA algorithm, that, in marked contrast to split-spectrum approaches, preserves the original high OCT axial resolution also within the resulting OCTA signal. En face OCTA images are generally created by averaging flow signals over a finite axial depth window. However, we assessed regional OCTA signal profiles at each depth position at full axial resolution. All regions had two sharp vessel density peaks near the inner and outer boundaries of the inner nuclear layer, indicating separate intermediate and deep capillary plexuses. The superficial vascular plexus (SVP) separated into two distinct peaks within the ganglion cell layer in the parafoveal zone. The nasal, superior, and inferior perifovea had a deeper SVP peak that was shifted anteriorly compared to the parafoveal zone. Axial vascular density analysis with high-resolution, full spectrum OCTA thus allows healthy retinal vasculature to be precisely reconstructed and may be useful for clinically assessing retinal pathology.

Quantifying vascular density and morphology using different swept-source optical coherence tomography angiographic scan patterns in diabetic retinopathy

AIMS

To evaluate quantitative metrics of the retinal microvasculature in eyes with diabetic retinopathy (DR) using various en face swept-source optical coherence tomography angiography (SS-OCTA) image sizes.

METHODS

Non-segmented and segmented images were acquired using an SS-OCTA device (PLEX Elite 9000; Carl Zeiss Meditec, Dublin, California, USA). The scanning protocols included the 3×3 mm, 6×6 mm and 12×12 mm fields of view. Quantitative analysis of the perfusion density (PD), vessel length density (VLD) and fractal dimension (FD) was performed. The area under the receiver operating characteristic curve was estimated to assess the ability of each image size to predict DR.

RESULTS

This prospective, cross-sectional study included 60 eyes, (non-DR, 13 eyes; non-proliferative DR (NPDR), 24 eyes; proliferative DR (PDR), 23 eyes) of 46 patients with diabetes and 21 eyes of 16 healthy individuals. In the 12×12 mm images, the PD of healthy individuals was significantly greater than that of patients with NPDR or PDR for all layers (NPDR, p<0.05; PDR, p<0.001 0.001; FD, p<0.001) or PDR (VLD, p<0.001; FD, p<0.001 for all layers). The results were similar for the 3×3 mm and 6×6 mm images. Overall, PD, VLD and FD progressively decreased with worsening DR severity in segmented and non-segmented layers for all SS-OCTA scan sizes. For detecting DR, 3×3 mm images best predicted DR for all evaluated quantitative parameters.

CONCLUSIONS

Vascular changes in DR can be monitored in detail through quantitative evaluations that combine different SS-OCTA scan sizes and parameters.

Pilot Study of the Effects of Ambient Light Level Variation on Spectral Domain Anterior Segment OCT-Derived Angle Metrics in Caucasians versus Asians

PURPOSE

To investigate the effects of ambient light level variation on spectral domain anterior segment optical coherence tomography (SD-ΟCT)-derived anterior chamber angle metrics in Caucasians versus Asians.

MATERIALS AND METHODS

Caucasian (n = 24) and Asian participants of Chinese ancestry (n = 24) with open angles on gonioscopy had one eye imaged twice at five strictly controlled, ambient light levels. Ethnicity was self-reported. Light levels were strictly controlled using a light meter at 1.0, 0.75, 0.5, 0.25, and 0 foot candle illumination levels. SD-OCT 5-line raster scans at the inferior 270° irido-corneal angle were measured by two trained, masked graders from the Doheny Image Reading Center using customized Image-J software. Schwalbe's line-angle opening distance (SL-AOD) and SL-trabecular iris space area (SL-TISA) in different light meter readings (LMRs) between the two groups were compared.

RESULTS

Baseline light SL-AOD and SL-TISA measured 0.464 ± 0.115mm/0.351 ± 0.110mm² and 0.344 ± 0.118mm/0.257 ± 0.092mm², respectively, in the Caucasian and the Asian group. SL-AOD and SL-TISA in each LMR were significantly larger in the Caucasian group compared to the Asian group (p < 0.05). Despite this difference in angle size between the groups, there were no statistically significant differences in the degree of change in angle parameters from light to dark (% changes in SL-AOD or SL-TISA between the two groups were statistically similar with all p-values >0.3).

CONCLUSION

SL-based angle dimensions using SD-OCT are sensitive to changes in ambient illumination in participants with Caucasian and Asian ancestry. Although Caucasian eyes had larger baseline angle opening under bright light conditions, the light-to-dark change in angle dimensions was similar in the two groups.

Wide-field en face swept-source optical coherence tomography angiography using extended field imaging in diabetic retinopathy

Aims

To examine the feasibility of wide-field en face swept-source optical coherence tomography angiography (SS-OCTA) with extended field imaging (EFI) for evaluation of the retinal vasculature in diabetic retinopathy (DR).

Methods

This study included 37 eyes of 27 patients (age, 65±10 years; male patients, 18; female patients, 9) with DR. All patients underwent comprehensive ophthalmological examination, including OCTA and fluorescein angiography (FA). The imaging methods were compared for visible field of view, presence and extent of non-perfused areas (NPAs), presence and number of new blood vessels (NVs), vessel density (VD) and patient comfort level measured by Visual Analogue Scale.

Results

SS-OCTA with EFI allowed capture of larger areas (by 1.80±0.18 times on average) of the fundus than SS-OCTA without EFI. Compared with FA, the sensitivities of SS-OCTA with EFI for detection of NPAs and NVs were 96% and 79%, respectively, with specificities of 100% and 96%, respectively. There was no significant difference in extent of NPAs (61.2±45.8 vs 61.5±55.0 disc areas, P=0.99) or number of NVs (1.5±3.3 vs 0.9±1.8, P=0.68) between FA and SS-OCTA with EFI. VD showed significantly lower values in EFI SS-OCTA than in those acquired without EFI (31.6%±4.3%  vs 34.2%±4.3%, P<0.001). Wide-field OCTA with EFI was significantly more comfortable for patients than FA (P<0.001).

Conclusions

SS-OCTA with EFI allows acquisition of wide-field en face images of the retinal vasculature in patients with DR, with greater patient comfort than FA.

Anatomical effects of dexamethasone intravitreal implant in diabetic macular oedema: a pooled analysis of 3-year phase III trials

BACKGROUND/AIM

To assess long-term effects of dexamethasone intravitreal implant (DEX implant) monotherapy on retinal morphology in diabetic macular oedema (DME).

METHODS

Two multicentre, masked, phase III studies with identical protocols randomised patients with DME, best-corrected visual acuity of 34-68 Early Treatment Diabetic Retinopathy Study letters and central subfield retinal thickness (CSRT) ≥300 µm to DEX implant 0.7, 0.35 mg or sham procedure. Patients were followed up for 3 years (39 months if treated at month 36), with retreatment allowed at ≥6-month intervals. Patients needing other macular oedema (ME) therapy exited the study. Changes from baseline in CSRT, macular volume and ME grade, area of retinal thickening, macular leakage, macular capillary loss and diabetic retinopathy severity were assessed.

RESULTS

After 3 years, more eyes treated with DEX implant 0.7 and 0.35 mg than sham showed improvement (although small) in ME grade (p<0.05 vs sham). DEX implant 0.7 mg delayed time to onset of two-step progression in diabetic retinopathy severity by ∼12 months. DEX implant 0.7 and 0.35 mg produced small, non-sustained reductions in macular leakage but had no significant effect on macular capillary loss.

CONCLUSIONS

DEX implant 0.7 or 0.35 mg, administered at ≥6-month intervals over 3 years, produced sustained retinal structural improvement in DME.

TRIAL REGISTRATION NUMBER

NCT00168337 and NCT00168389.

Proposed lexicon for anatomic landmarks in normal posterior segment spectral-domain optical coherence tomography: the IN•OCT consensus

PURPOSE

To develop a consensus nomenclature for the classification of retinal and choroidal layers and bands visible on spectral-domain optical coherence tomography (SD-OCT) images of a normal eye.

DESIGN

An international panel with expertise in retinal imaging (International Nomenclature for Optical Coherence Tomography [IN • OCT] Panel) was assembled to define a consensus for OCT imaging terminology.

PARTICIPANTS

A panel of retina specialists.

METHODS

A set of 3 B-scan images from a normal eye was circulated to the panel before the meeting for independent assignment of nomenclature to anatomic landmarks in the vitreous, retina, and choroid. The outputs were scrutinized, tabulated, and used as the starting point for discussions at a roundtable panel meeting. The history of anatomic landmark designations over time was reviewed for the various cellular layers of the ocular structures that are visible by SD-OCT. A process of open discussion and negotiation was undertaken until a unanimous consensus name was adopted for each feature.

MAIN OUTCOME MEASURES

Definitions of normal eye features showed by SD-OCT.

RESULTS

Definitions for various layers changed frequently in the literature and were often inconsistent with retinal anatomy and histology. The panel introduced the term "zone" for OCT features that seem to localize to a particular anatomic region that lacks definitely proven evidence for a specific reflective structure. Such zones include the myoid, ellipsoid, and the interdigitation zones.

CONCLUSIONS

A nomenclature system for normal anatomic landmarks seen on SD-OCT outputs has been proposed and adopted by the IN • OCT Panel. The panel recommends this standardized nomenclature for use in future publications. The proposed harmonizing of terminology serves as a basis for future OCT research studies.

Optical coherence tomographic and visual results at six months after transitioning to aflibercept for patients on prior ranibizumab or bevacizumab treatment for exudative age-related macular degeneration (an American Ophthalmological Society thesis)

PURPOSE

To study optical coherence tomographic (OCT) results and vision at 6 months after transition (post-Tx) from intravitreal bevacizumab and/or ranibizumab to aflibercept for treatment of neovascular age-related macular degeneration (nAMD). The null hypothesis was the lack of improvements in OCT metrics and vision outcome in study eyes at 6 months after transitioning from bevacizumab or ranibizumab to aflibercept.

METHODS

This retrospective study assessed 6 monthly OCT (Cirrus) data after transitioning to aflibercept for eyes on prior Legacy-ranibizumab, Legacy-bevacizumab, or mixed treatment for nAMD. Outcome measures were subretinal fluid (SRF), cystoid macular edema (CME), pigment epithelial detachment (PED) heights and volumes, central 1- and 3-mm subfield, Macular Volume, and best spectacle and pinhole visual acuity (VA). A single masked investigator performed all OCT measurements.

RESULTS

One hundred eighty-nine eyes in 172 patients in Legacy-bevacizumab (95 eyes), Legacy-ranibizumab (84 eyes), or Mixed Group(10 eyes) were switched to aflibercept and followed for 6 months. Significant post-Tx reductions were noted in SRF/CME heights and volumes (all P<.001). Similar findings were noted for PED heights (122.8 μm vs 79.4 μm) and PED volumes (all P<.001). Post-Tx VA was better (20/43 vs 20/51, P<.001). There were no differences between Legacy-bevacizumab and Legacy-ranibizumab groups in OCT and VA changes. Post-Tx VA, SRF/CME, and PED heights and volumes were improved for Nonresponders (suboptimal response to bevacizumab/ranibizumab) (P=.001 to <.001), but not Responders (good responses to same). The only adverse event was a retinal pigment epithelial tear in one eye.

CONCLUSIONS

Significant improvements in vision and OCT metrics developed in Nonresponders but not in Responders. Post-Tx VA and OCT measures were similar for eyes on prior bevacizumab or ranibizumab. Post-Tx adverse events were uncommon.

TCF7L2 variation and proliferative diabetic retinopathy

Proliferative diabetic retinopathy (PDR) is the most severe vision-threatening complication of diabetes. For investigation of genetic association between TCF7L2 and PDR in Caucasian type 2 diabetes mellitus (T2DM) and its functional consequences, 383 T2DM patients with PDR (T2DM-PDR) and 756 T2DM patients without diabetic retinopathy (T2DM-no DR) were genotyped with rs7903146 in TCF7L2. We found that risk allele (T) frequency of rs7903146 was significantly higher in T2DM-PDR patients (allelic P = 2.52E-04). In lymphoblastoid cells induced to undergo endoplasmic reticulum (ER) stress by treatment of tunicamycin, higher fold change of TCF7L2 and VEGFA mRNA levels were observed in rs7903146-TT cells than in rs7903146-CC cells (P = 0.02 for TCF7L2; P = 0.004 for VEGFA), suggesting that ER stress plays a role in PDR pathogenesis. Silencing TCF7L2 resulted in decreased mRNA levels of both TCF7L2 and VEGFA (P < 0.001). Retinas of oxygen-induced retinopathy mice (a model for PDR) had higher TCF7L2 and VEGFA mRNA levels than those of controls (P = 2.9E-04 for TCF7L2; P = 1.9E-07 for VEGFA). Together, data from our study show that TCF7L2-rs7903146 is associated with PDR in Caucasian T2DM and suggest that TCF7L2 promotes pathological retinal neovascularization via ER stress-dependent upregulation of VEGFA.

Drusen detection by confocal aperture-modulated infrared scanning laser ophthalmoscopy

AIM

To evaluate the efficiency of drusen detection by scanning laser ophthalmoscopy (SLO) using various infrared confocal apertures and differential contrast (DC) strategies.

METHODS

11 eyes with non-neovascular age-related macular degeneration (AMD) underwent infrared imaging with a Nidek F-10 confocal SLO using multiple confocal apertures: central, ring, aperture on the right side (AR) and left side (AL), with and without use of the DC. A conventional colour fundus photograph was also obtained. Images were exported into a certified grading tool and all visible drusen were manually outlined by two graders. For each image type, the number of drusen and total drusen area were calculated, and the measurements obtained by the two graders were averaged. Intergrader reliability was evaluated, and paired t tests compared measurements between the various aperture/DC modes and the colour image.

RESULTS

Agreement between graders was high (r=0.93-0.98). Drusen number values obtained with the AR (121.0, p=0.01) mode were higher than for the colour photographs (69.1). Area measurements were also significantly higher in the AR (1.93 mm(2); p=0.04) and AL modes (1.41 mm(2); p=0.03) when compared with the colour photographs (1.24 mm(2)). The addition of the DC did not seem to improve drusen detection compared with the unmodified infrared images.

CONCLUSIONS

In this pilot study, drusen number and area grades were significantly higher using the AR and AL in which the laterally scattered light is captured (retromode). Use of the lateral confocal aperture may highlight subclinical drusen and aid in monitoring disease progression and response to emerging non-neovascular AMD therapies.

Selective laser trabeculoplasty complicated by cystoid macular edema: report of two cases

PURPOSE

Selective laser trabeculoplasty, a relatively novel treatment for open angle glaucoma, is frequently associated with mild post-operative intraocular inflammation.

METHODS

We report two uncommon cases of cystoid macular edema within a few weeks of routine selective laser trabeculoplasty.

RESULTS

Visual acuities and macular thicknesses of the two cases returned to baseline after medical treatment, but in one case, the cystoid macular edema persisted for months.

CONCLUSION

Cystoid macular edema after selective laser trabeculoplasty is fortunately a rare complication, but it might be more common in patients with predisposing factors, and it can be resistant to treatment.

Morphometric spectral-domain optical coherence tomography features of epiretinal membrane correlate with visual acuity in patients with uveitis

PURPOSE

To identify visually significant spectral-domain optical coherence tomography (SD-OCT) features of epiretinal membranes (ERM) in patients with uveitis.

DESIGN

Retrospective cohort and cross-sectional study.

METHODS

Eighty consecutive eyes with uveitis and SD-OCT-documented ERM were included. Clinical data were collected at the time of diagnosis of ERM and at the final visit. SD-OCT images at the last visit were evaluated to identify fovea and ERM configuration and structural changes. Changes of 10% and 20% in central subfield thickness between initial and last SD-OCT were calculated and correlated with visual acuity (VA). An ERM thickness map was created using validated SD-OCT grading software.

RESULTS

VA improved significantly in eyes with more than 12 months of follow-up (P = .03). Although inflammation activity and medical treatment methods were no different in eyes with more or less than 12 months of follow-up, 16 eyes in the subset with longer follow-up underwent cataract extraction and intraocular lens implantation. Kaplan-Meier analysis demonstrated few vision losses during the follow-up period. Change in central subfield thickness did not correlate with VA. Foveal center involvement (P < .001), focal attachment of the ERM (P = .003), and foveal inner segment and outer segment junction disruption (P = .006) were associated independently with lower VA. ERM was thinner in eyes with 20/40 or better VA (4.6 ± 0.6 μm) compared with eyes with VA of less than 20/200 (P = .02). Longer duration of ERM was associated with thicker ERM (P < .05).

CONCLUSIONS

In most eyes with uveitis and ERM, VA remains stable if ocular inflammation and comorbidities are addressed appropriately.

Image quality affects macular and retinal nerve fiber layer thickness measurements on fourier-domain optical coherence tomography

BACKGROUND AND OBJECTIVE

To investigate whether image quality is an important determinant of retinal nerve fiber layer (RNFL) and macular thickness measurements on Fourier-domain optical coherence tomography (OCT).

PATIENTS AND METHODS

Seventy-five and 56 normal subjects were recruited in RNFL and macular thickness arms of the study, respectively. Each participant was scanned three times using both the 3D OCT-1000 (version 3.01, Mark II; Topcon Corporation, Tokyo, Japan) and the Cirrus OCT (version 3.0, Model 4000; Carl Zeiss Meditec, Inc., Dublin, CA). The scans for each participant were arranged in order of increasing image qualities, which were correlated with RNFL and macular thicknesses. Subgroup analyses were performed with identical versus different and high versus low image quality metrics.

RESULTS

Higher image quality was significantly correlated with greater RNFL thickness measurements on the 3D OCT-1000, and when the signal strength was less than 7 on the Cirrus device. Image quality metrics were negatively correlated with measured macular thicknesses on Cirrus OCT but not on 3D OCT-1000.

CONCLUSION

Image quality metrics should be considered when evaluating thickness measurements derived from Fourier-domain OCT devices.

Intraretinal Segmentation on Fourier Domain Optical Coherence Tomography

Introduction: We studied the automated intraretinal segmentation on Fourier domain optical coherence tomography (OCT). Materials and Methods: Thirty eyes from 30 normal subjects were studied using the RTVue-100. Both radial and raster scan protocol were performed 3 times on each subject. The OCT software performs automated intraretinal segmentation and provides macular thickness measurements. Results: Both scanning protocols provide reproducible inner, outer and full retinal thickness measurements. The inner, outer and full retinal thicknesses at the foveal central subfield were 67.31 ± 12.27 μm, 151.67 ± 12.96 μm, 219.33 ± 23.19 μm, respectively by the raster scan, and 63.27 ± 10.37 μm, 147.07 ± 14.54 μm, 209.89 ± 21.80 μm, respectively by the radial scan. Macular regional variations were consistently observed. The raster scan protocol gives greater retinal thickness measurements than the radial scan protocol (P <0.05), but the latter yields slightly more reproducible results. Conclusions: Fourier domain OCT equipped with the ability to perform automatic intraretinal segmentation is a convenient tool in studying diseases that may differentially affect various parts of the retina. However, the establishment of normative values can be complicated by different scanning protocols, devices used, methods of data presentation and definition of intraretinal boundaries. Key words: Histology, Image processing, Retina/anatomy

Intraretinal segmentation on fourier domain optical coherence tomography

INTRODUCTION

We studied the automated intraretinal segmentation on Fourier domain optical coherence tomography (OCT).

MATERIALS AND METHODS

Thirty eyes from 30 normal subjects were studied using the RTVue-100. Both radial and raster scan protocol were performed 3 times on each subject. The OCT software performs automated intraretinal segmentation and provides macular thickness measurements.

RESULTS

Both scanning protocols provide reproducible inner, outer and full retinal thickness measurements. The inner, outer and full retinal thicknesses at the foveal central subfield were 67.31 +/- 12.27 microm, 151.67 +/- 12.96 microm, 219.33 +/- 23.19 microm, respectively by the raster scan, and 63.27 +/- 10.37 microm, 147.07 +/- 14.54 microm, 209.89 +/- 21.80 microm, respectively by the radial scan. Macular regional variations were consistently observed. The raster scan protocol gives greater retinal thickness measurements than the radial scan protocol (P <0.05), but the latter yields slightly more reproducible results.

CONCLUSIONS

Fourier domain OCT equipped with the ability to perform automatic intraretinal segmentation is a convenient tool in studying diseases that may differentially affect various parts of the retina. However, the establishment of normative values can be complicated by different scanning protocols, devices used, methods of data presentation and definition of intraretinal boundaries.

Inadvertent Use of Bevacizumab to Treat Choroidal Neovascularisation During Pregnancy: A Case Report

Introduction: This study reports a case of bevacizumab administered to treat choroidal neovascularisation in a woman later discovered to be pregnant. Clinical Picture: A 25-year-old pregnant woman developed myopic choroidal neovascularisation in both eyes. Treatment: Both eyes were treated with a total of 3 intravitreal injections of bevacizumab sequentially. Outcome: Vision improved significantly in both eyes. There were no evident pregnancy-related complications at 1 year postpartum. Conclusion: Although anti-vascular endothelial growth factor (VEGF) therapy did not result in any detectable short-term adverse event in this mother and baby, the potential toxicity of these agents must be carefully considered in pregnant patients. Key words: Anti-VEGF therapy, Pre-eclampsia, Vasculogenesis

Inadvertent use of bevacizumab to treat choroidal neovascularisation during pregnancy: a case report

INTRODUCTION

This study reports a case of bevacizumab administered to treat choroidal neovascularisation in a woman later discovered to be pregnant.

CLINICAL PICTURE

A 25-year-old pregnant woman developed myopic choroidal neovascularisation in both eyes.

TREATMENT

Both eyes were treated with a total of 3 intravitreal injections of bevacizumab sequentially.

OUTCOME

Vision improved significantly in both eyes. There were no evident pregnancy-related complications at 1 year postpartum.

CONCLUSION

Although anti-vascular endothelial growth factor (VEGF) therapy did not result in any detectable short-term adverse event in this mother and baby, the potential toxicity of these agents must be carefully considered in pregnant patients.

Central retinal vein occlusion: a case report and review of the literature

Introduction

Central retinal vein occlusion is one of the major causes of severe vision impairment and blindness in adults.

Case presentation

We present a case of unilateral ischemic central retinal vein occlusion in a 54-year-old woman with history of uncontrolled hypertension and open angle glaucoma. Laboratory tests including complete hypercoagulability and thrombotic workup were completed.

Conclusion

Our case illustrates an interesting presentation of unilateral ischemic central retinal vein occlusion, where hypertension and glaucoma were thought to be the main risk factors. Close follow up, tight blood pressure and glaucoma control are crucial to prevent similar scenario in the fellow eye.

A new model of experimental subretinal neovascularization in the rabbit

Existing animal models of choroidal neovascularization (CNV) present several problems: they are hard to reproduce, they are inefficient, and the CNV created is not sustainable. The purpose of this study is to develop a highly efficient, reliable, sustainable rabbit model of CNV to facilitate the study of anti-angiogenic and anti-proliferative therapies for ocular diseases. Twenty-two pigmented rabbits were used in this study. Eleven rabbits received subretinal injections of either 10 microl of Matrigel with 500 ng of vascular endothelial growth factor (VEGF) or 20 microl of Matrigel with 750 ng of VEGF; eight rabbits received subretinal injections of either 10 or 20 microl of Matrigel only; three rabbits used as controls received subretinal injections of 20 microl phosphate-buffered saline (PBS) alone. Fundus photography, fluorescein angiography, optical coherence tomography, and histologic examinations were performed 1, 2, 4, and 9 weeks after injection. All experimental eyes showed angiographic leakage within this localized area 1 week after injection. The amount of leakage usually increased at weeks 2 and 4 and, in most cases, persisted at week 9. Control eyes demonstrated no leakage at any time point. Optical coherence tomography of treated eyes showed subretinal fluid and the presence of a lesion, possibly vascular or fibrotic, at the site of the leakage. Histologic analysis confirmed the presence of new subretinal blood vessels in the areas of Matrigel deposit. In conclusion, this novel method provides a highly reproducible, reliable, and sustainable rabbit model of experimental choroidal neovascularization. Such a model may prove useful for screening new anti-angiogenic therapies in a larger animal eye.

ONE-YEAR RESULTS OF A PILOT STUDY USING ORAL 13-CIS RETINOIC ACID AS A TREATMENT FOR SUBFOVEAL PREDOMINANTLY OCCULT CHOROIDAL NEOVASCULARIZATION IN PATIENTS WITH AGE-RELATED MACULAR DEGENERATION

PURPOSE

To evaluate the safety and evidence of efficacy for oral 13-cis retinoic acid as a treatment for patients with subfoveal occult choroidal neovascularization (CNV) due to age-related macular degeneration (ARMD).

METHODS

Patients with active, subfoveal occult CNV with no prior treatment of the subfoveal component were eligible for inclusion. Patients received 40 mg of 13-cis retinoic acid twice daily for 5 months, stopped treatment for 2 months, and then resumed treatment for 5 months. Patients were observed monthly with Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity (VA), clinical examination, fluorescein angiography, and laboratory testing.

RESULTS

Eleven patients, aged 64 to 88 years, were enrolled and followed for 1 year. Initial VA ranged from 55 (20/40) to 5 (20/400) ETDRS letters (median 48 letters). Mild drug-related side effects (dry skin, chapped lips) occurred in all 11 patients. Three patients experienced more severe side effects (muscle aches, mood swings) and did not resume treatment after the drug holiday. Moderate VA loss occurred in 36% at both 6 and 12 months.

CONCLUSIONS

Oral 13-cis retinoic acid is too toxic to be useful in patients with ARMD. Oral 13-cis retinoic acid did not improve vision although it may have slowed visual acuity loss in patients with ARMD with occult subfoveal CNV.

Electrical stimulation of isolated retina with microwire glass electrodes

The development of high-resolution retinal prostheses fabricated from silicon wafers presents an interesting problem: how to electrically bridge the space between the flat silicon wafer and the curved retinal surface. One potential "bridge" is a microwire glass electrode. In this paper we present our results in evaluating microwire glass electrodes. We stimulated isolated rabbit retina (n = 5) with a 0.0256 cm(2) microwire electrode. The current and pulse duration were varied from 498 to 1660 microA and 0.1 to 3 ms, respectively. We found that short pulses produced more spikes per coulomb and longer pulses produced more spikes per milliamp. The optimal pulse duration range of 0.7-1 ms was identified as a compromise between the advantages of short and long pulses. Stimulation of isolated rabbit retina with microwire glass results in consistent neuronal spike formation at safe charge density, 20.7 +/- 4.3 microC/cm(2). We also examined the response of retinas (n = 6) to stimulation with a smaller microwire electrode, 0.0002 cm(2). We found that less current was required (15 microA versus 756 microA) for a 1 ms pulse, but at the expense of greater charge density (75 microC/cm(2) versus 29.5 microC/cm(2)). Nonetheless, a 128-fold reduction in area resulted in only a 2.7-fold increase in charge density required for a 1 ms pulse duration. The results presented here indicate that microwire glass can be used as a neural stimulating electrode to bridge the gap between flat microelectronic stimulator chips and curved neuronal tissue.

Morphometric analysis of the macula in eyes with geographic atrophy due to age-related macular degeneration

PURPOSE

To evaluate the extent of neural cell death in eyes with geographic atrophy (GA).

METHODS

Ten eyes with GA and five age-matched control eyes were selected for morphometric analysis. The nuclei of the ganglion cell, inner nuclear, and outer nuclear layers were counted in contiguous 100-microm segments from 1,500 microm nasal to 1,500 microm temporal to the fovea.

RESULTS

The outer nuclear layer was most severely attenuated in eyes with GA, demonstrating a 76.9% reduction relative to control eyes (P < 0.0001). A significant loss of ganglion cells (by 30.7%) was also observed (P = 0.0008). There was no significant difference in the inner nuclear layer cells (P = 0.30). Among the GA eyes, the nuclei in all three layers were significantly reduced in segments in which the retinal pigment epithelium was completely absent (P </= 0.0003).

CONCLUSION

Although the nuclei of the outer nuclear layer in eyes with GA were markedly attenuated, the nuclei of the inner nuclear layer were relatively preserved. There was also a significant reduction in ganglion cells in GA eyes, but considerable numbers remained even in the areas of complete retinal pigment epithelium atrophy. This finding suggests that therapies aimed at replacing outer nuclear function (such as neural retinal and retinal pigment epithelium transplantation or implantation of the intraocular retinal prosthesis) may be feasible for restoring vision in these patients.

Morphometric analysis of the macula in eyes with disciform age-related macular degeneration

PURPOSE

To evaluate the extent of neural cell death in eyes with disciform age-related macular degeneration.

METHODS

Six eyes with disciform degeneration at various stages and five age-matched control eyes were selected for morphometric analysis using digitized light microscopic images. Disciform scars were classified as subneurosensory retinal, subretinal pigment epithelial, or combined lesions. The nuclei of the ganglion cell, inner nuclear, and outer nuclear layers were counted in contiguous 100 microm segments spanning a distance from 1,500 microm nasal to 1,500 microm temporal to the fovea.

RESULTS

The outer nuclear layer was most severely attenuated in eyes with disciform scars, demonstrating a 69.4% reduction in cell number relative to control eyes. A loss in retinal ganglion cells (by 7.3%) and an increase in inner nuclear layer cells (by 10%) were observed, but these changes were not significant. Photoreceptor loss was most pronounced when the disciform scar was not covered by the retinal pigment epithelium.

CONCLUSION

The nuclei of the outer nuclear layer are significantly attenuated in eyes with disciform age-related macular degeneration, while the ganglion cell and inner nuclear layers are relatively preserved. These findings suggest that replacement of outer nuclear function, by either retinal transplantation or implantation of the intraocular retinal prosthesis, might be a feasible therapeutic option for patients with this condition.

Ganglion cell responses to retinal light stimulation in the absence of photoreceptor outer segments from retinal degenerate rodents

PURPOSE

To determine whether a severely degenerated retina without photoreceptor outer segments and a non-recordable electroretinogram (ERG) can still show retinal ganglion cell (RGC) responses to retinal light stimulation.

METHODS

The authors measured ERGs and retinal surface RGC responses from six week old rd mice and three month old homozygous S334ter line3 rats. Animal eyes were also studied by light microscopy, transmission electron microscopy, and immunohistochemistry (rats).

RESULTS

The corneal ERGs were non-recordable and no photoreceptor outer segments were found in either retinal degeneration model. A few cell bodies (without outer segments) that were immunoreactive for cone opsin and rhodopsin were found in the outer nuclear layer of the rats. Light-driven ON-RGC responses, however, were recordable from six week old rd mice. In addition, light-driven ON and OFF-RGC responses were recordable from three month old homozygous S334ter line 3 rats.

CONCLUSIONS

This study suggests that despite the apparent absence of photoreceptor outer segments and a non-recordable ERG, ganglion cell responses to retinal light stimulation may remain preserved in some severe retinal degenerate transgenic rodents.