Abhilash Goud

Neurodegeneration in Type 2 Diabetes: Evidence From Spectral-Domain Optical Coherence Tomography

PURPOSE The purpose of this study was to assess changes in the neural retina in eyes with different stages of diabetic retinopathy (DR) in comparison to age-matched healthy subjects. METHODS Retrospective analysis of spectral-domain optical coherence tomography (SD-OCT) scans of 76 naïve eyes of 62 subjects with diabetes was performed. Key exclusion criteria included presence of diabetic macular edema, any other retinal disease, history of any treatment for DR, or incorrect segmentation of the retinal layers on SD-OCT scans. Eyes from diabetic patients were divided into three groups, including no DR, nonproliferative DR (NPDR), and proliferative DR (PDR). A control group of 67 eyes of 66 age-matched healthy volunteers was included for comparison. Average, minimum, and sectoral thicknesses for the ganglion cell-inner plexiform layer (GCIPL) and retinal nerve fiber layer (RNFL) were collected from both groups and compared using an ANOVA test. RESULTS Among the 76 included eyes, 43 had NPDR, 13 had PDR, and 20 had no signs of DR. Average and minimum GCIPL showed significant thinning in diabetic subjects compared with controls in all stages of DR (P < 0.05), especially involving the papillo-macula bundle. However, GCIPL thickness was similar between diabetic groups. There was no significant difference in average or sectoral RNFL thicknesses among groups; however, the minimum RNFL thickness was lower in diabetics compared with controls (P < 0.05). No relationship between GCIPL and RNFL thicknesses and duration of diabetes was present. CONCLUSIONS Early thinning on the inner retina happens in type 2 diabetes, even before visible vascular signs of DR. This supports the presence of a neurodegenerative process in eyes of patients with diabetes and warrants neuroprotective intervention to prevent chronic neurodegeneration. The SD-OCT may represent an indispensable tool for identifying early signs of neurodegeneration in diabetic patients.

In vivo evaluation of retinal ganglion cells degeneration in eyes with branch retinal vein occlusion

Purpose To analyse the topographic changes in retinal ganglion cells (RGCs) in eyes with unilateral naive branch retinal vein occlusion (BRVO) in comparison to normal fellow eyes and to healthy control eyes. Methods We performed a retrospective analysis of 66 eyes (33 subjects) with naive unilateral BRVO who underwent spectral-domain optical coherence tomography using Cirrus HD-OCT. We also included 67 eyes of 48 age-matched healthy volunteers as control group. Average, minimum and sectoral macular ganglion cell-inner plexiform layer (GCIPL) thickness, macular retinal nerve fibre layer (RNFL) thickness and outer retinal thickness were collected. Comparison of the GCIPL, RNFL and outer retinal thicknesses among study eyes, normal fellow eyes and control groups was performed. Results The average and minimum macular GCIPL thicknesses were constantly and diffusely reduced in BRVO compared with normal fellow eyes and healthy controls (p<0.001 for each GCIPL sector). The average macular RNFL thickness was reduced in BRVO eyes compared with normal fellow eyes (p=0.01) and tended to be lower than controls (p=0.07). The minimum RNFL thickness in eyes with BRVO was significantly reduced when compared with fellow eyes (p<0.001) and control eyes (p<0.001). The average outer retina thickness was thicker in BRVO eyes compared with both fellow eyes (p<0.001) and controls (p<0.001). Conclusions A significant reduction of the macular GCIPL and RNFL thicknesses was observed in eyes with BRVO. This finding is suggestive of RGCs degeneration; the neuroprotective effect of current therapeutic options might be an important consideration when evaluating treatment strategies and prognosticating visual outcome in BRVO eyes.

Influence of scanning area on choroidal vascularity index measurement using optical coherence tomography

Recently, choroidal vascularity index (CVI) is proposed as a novel tool to evaluate the choroidal vasculature. In this study, we investigate the impact of scanning area on CVI measurement using spectral‐domain optical coherence tomography (SD‐OCT).

Prevalence and Distribution of Segmentation Errors in Macular Ganglion Cell Analysis of Healthy Eyes Using Cirrus HD-OCT.

Purpose To determine the frequency of different types of spectral domain optical coherence tomography (SD-OCT) scan artifacts and errors in ganglion cell algorithm (GCA) in healthy eyes. Methods Infrared image, color-coded map and each of the 128 horizontal b-scans acquired in the macular ganglion cell-inner plexiform layer scans using the Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA) macular cube 512 × 128 protocol in 30 healthy normal eyes were evaluated. The frequency and pattern of each artifact was determined. Deviation of the segmentation line was classified into mild (less than 10 microns), moderate (10–50 microns) and severe (more than 50 microns). Each deviation, if present, was noted as upward or downward deviation. Each artifact was further described as per location on the scan and zones in the total scan area. Results A total of 1029 (26.8%) out of total 3840 scans had scan errors. The most common scan error was segmentation error (100%), followed by degraded images (6.70%), blink artifacts (0.09%) and out of register artifacts (3.3%). Misidentification of the inner retinal layers was most frequent (62%). Upward Deviation of the segmentation line (47.91%) and severe deviation (40.3%) were more often noted. Artifacts were mostly located in the central scan area (16.8%). The average number of scans with artifacts per eye was 34.3% and was not related to signal strength on Spearman correlation (p = 0.36). Conclusions This study reveals that image artifacts and scan errors in SD-OCT GCA analysis are common and frequently involve segmentation errors. These errors may affect inner retinal thickness measurements in a clinically significant manner. Careful review of scans for artifacts is important when using this feature of SD-OCT device.

Microsecond yellow laser for subfoveal leaks in central serous chorioretinopathy

Purpose To evaluate the role of navigated yellow microsecond laser in treating subfoveal leaks in nonresolving central serous chorioretinopathy (CSC). Methods This prospective study included ten eyes of ten consecutive patients with nonresolving CSC with subfoveal leaks. All eyes were treated with 577 nm navigated yellow microsecond laser (5% duty cycle). Key inclusion criteria include a vision loss for a duration of minimum 3 months duration due to focal subfoveal leak on fluorescein angiography. Key exclusion criteria include prior treatment for CSC and any signs of chronic CSC. Comprehensive examination, in addition to low-contrast visual acuity assessment, microperimetry, autofluorescence, spectral domain optical coherence tomography, and fundus fluorescein angiography, was done at baseline, 1, 3, and 6 months after treatment. Rescue laser was performed as per predefined criteria at 3 months. Results The average best-corrected visual acuity improved from 73.3±16.1 letters to 75.8±14.0 (P=0.69) at 3 months and 76.9±13.0 (P=0.59) at 6 months, but was not statistically significant. Low-contrast visual acuity assessment (logMAR) improved from 0.41±0.32 to 0.35±0.42 (P=0.50) at 3 months and 0.28±0.33 (P=0.18) at 6 months. Average retinal sensitivity significantly improved from baseline 18.93±7.19 dB to 22.49±6.67 dB (P=0.01) at 3 months and 21.46±8.47 dB (P=0.04) at 6 months. Rescue laser was required only in one eye at 3 months; however, laser was required in three eyes at 6 months. Conclusion Microsecond laser is a safe and effective modality for treating cases of nonresolving CSC with subfoveal leaks.

Subfoveal Choroidal Vascularity in Myopia: Evidence From Spectral-Domain Optical Coherence Tomography

BACKGROUND AND OBJECTIVE To evaluate subfoveal choroidal vascularity in eyes with myopia in comparison to age-matched healthy subjects. PATIENTS AND METHODS Retrospective analysis of single foveal enhanced depth imaging optical coherence tomography (EDI-OCT) scans of 30 eyes with myopia (axial length greater than 25 mm). Subfoveal choroidal vascularity was evaluated by calculating vessel-area-to-stromal-area ratio using a previously validated automated algorithm. RESULTS The subfoveal stromal area was significantly smaller in myopes (0.95 mm3 ± 0.22 mm3) compared to controls (1.33 mm3 ± 0.23 mm3; P < .0001). However, there was no significant difference in vascular area or in vessel-area-to-stroma-area ratio between the groups (P = .15 and P = .16, respectively). Subfoveal choroidal vascularity percentage was also not significantly different between the two groups (P = .07). CONCLUSION Subfoveal choroidal thinning in myopia is primarily associated with a reduction in choroidal stroma, not vascular components. This needs further exploration and has potential clinical applications. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:202-207.].

Segmentation errors in macular ganglion cell analysis as determined by optical coherence tomography in eyes with macular pathology

BackgroundTo evaluate artifacts in macular ganglion cell inner plexiform layer (GCIPL) thickness measurement in eyes with retinal pathology using spectral-domain optical coherence tomography (SD OCT).MethodsRetrospective analysis of color-coded maps, infrared images and 128 horizontal B-scans (acquired in the macular ganglion cell inner plexiform layer scans), using the Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA). The study population included 105 eyes with various macular conditions compared to 30 eyes of 30 age-matched healthy volunteers. The overall frequency of image artifacts and the relative frequency of artifacts were stratified by macular disease.ResultsScan errors and artifacts were found in 55.1% of the 13,440 B-scans in eyes with macular pathology and 26.8% of the 3840 scans in normal eyes. Segmentation errors were the most common scan error in both groups, with more common involvement of both segmentation borders in diseased eyes and anterior segmentation border in normal eyes.ConclusionSegmentation errors and artifacts in SD OCT GCA are common in conditions involving the macula. These findings should be considered when assessing macular GCIPL thickness and careful assessment of scans is suggested.

Patterns of posterior ocular complications in myopic eyes of Indian population

This is a retrospective study aimed to investigate the patterns of myopic fundus complications in Indian children and young adults. Electronic medical records of 29,592 patients, aged 10–40 years, who visited L V Prasad Eye Institute between 1st January to 31st December 2016 were analysed in the study. Data such as age, gender, refractive error and various pathologic lesions of posterior globe were considered for analysis. Among all the patients with different types of refractive errors, myopia was found in 47.4%, high myopia in 6.8% and pathologic myopia in 2.2%. There was no trend of the increased prevalence of pathologic myopia with increasing age, except for a significant difference between the children aged 10–15 years (2.7%) and those aged more than 15 years (>4%). . Although, the overall pattern of pathologic lesions was similar across different grades of myopia (2.5% in low myopes vs. 2.2% in severe myopes), lesions like staphyloma and retinal detachment increased with increasing degree of myopia. The proportion of pathologic lesions across different grades of myopia suggests the necessity for careful peripheral fundus examinations irrespective of the degree of myopia for better management and prognostic purposes.

Quantitative shadow compensated optical coherence tomography of choroidal vasculature

Conventionally rendered optical coherence tomography (OCT) images of the posterior segment contain shadows which influence the visualization of deep structures such as the choroid. The purpose of this study was to determine whether OCT shadow compensation (SC) alters the appearance of the choroid and the apparent choroidal vascularity index (CVI), an OCT-derived estimated ratio of luminal to total choroidal volume. All scans were shadow compensated using a previously published algorithm, binarized using a novel validated algorithm and extracted binarized choroid to estimate CVI. On 27 raw swept-source OCT volume-scans of healthy subjects, the effect of SC on CVI was established both qualitatively and quantitatively. In shadow compensated scans, the choroid was visualized with greater brightness than the neurosensory retina and the masking of deep tissues by retinal blood vessels was greatly reduced. Among study subjects, significant mean difference in CVI of −0.13 was observed between raw and shadow compensated scans. Conventionally acquired OCT underestimates both choroidal reflectivity and calculated CVI. Quantitative analysis based on subjective grading demonstrated that SC increased the contrast between stromal and luminal regions and are in agreement with true tissue regions. This study is warranted to determine the effects of SC on CVI in diseased eyes.

Author Correction: Quantitative shadow compensated optical coherence tomography of choroidal vasculature

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