Wide-field angiography in retinal vein occlusions.

BACKGROUND: Retinal vein occlusion (RVO) is the second most common retinal vascular disease after diabetic retinopathy. It can result in significant visual loss from complications like macula edema, retinal and iris neovascularization, and vitreous hemorrhage. Recently, ultra-widefield imaging (UWF) has been developed for posterior pole visualization and has shown to be useful in the evaluation and treatment of RVO. MAIN TEXT: Ultra-widefield imaging (UWF) imaging allows for visualization of the retina up to an angle of 200°. This is especially important in detecting peripheral retinal pathologies, especially in retinal conditions such as RVO, where the disease process affects the peripheral as well as central retina. In particular, retinal non-perfusion in RVO is a risk factor for neovascularization. Various techniques, such as ischemic index and stereographic projection, have been described to assess areas of ischemia on UWF images. Retinal non-perfusion has an impact on disease complications, such as macular edema, and retinal and iris neovascularization. Retinal non-perfusion also has implications on disease response, including visual acuity, reduction in retinal edema and treatment burden. CONCLUSION: Ultra-widefield imaging (UWF) imaging plays an important role in the assessment and management of RVO, especially in measuring retinal non-perfusion in the peripheries.

Relationship between Myopia Severity and Macular Retinal Thickness on Visual Performance under Different Lighting Conditions.

OBJECTIVE: To evaluate the relationship between both spherical equivalent (SE) and retinal thickness (RT) on best-corrected visual acuity (BCVA) among young Asian adult men under photopic, mesopic, and simulated night-vision goggle (NVG) lighting conditions. DESIGN: Community-based cross-sectional study. PARTICIPANTS: Total of 698 myopic and 148 emmetropic subjects. METHODS: All participants underwent a complete ophthalmic examination and color fundus photography. BCVA and subjective refraction were assessed under standardized photopic, mesopic, and simulated NVG lighting conditions. Retinal thickness in various Early Treatment Diabetic Retinopathy Study (ETDRS) subfields was measured using spectral-domain OCT using a standardized protocol. Univariate and multiple linear regression analyses were performed to assess the relationship between BCVA and both SE and RT. MAIN OUTCOME MEASURES: Relationship between BCVA and both SE and RT. RESULTS: The mean age of all subjects was 21.1 years, with mean SE of -8.44 diopter (D) among the myopic subjects (range, -3.75 D to -23.0 D) and +0.10 among the emmetropic subjects (range, -0.49 D to +1.00 D). BCVA worsened progressively with increasing myopia under all lighting conditions (standardized coefficient -0.581 under photopic conditions, P < 0.001). RT was thickest among participants with LogMAR VA ≤0.00, and became thinner in the groups including those with VA >0.00 to ≤0.10 and >0.10 (mean inner subfield RT: 342.7 µm vs. 338.1 µm vs. 331.0 µm, respectively, P < 0.001) under all lighting conditions. When multiple linear regression was performed, higher degrees of myopia and decreasing RT were associated with reduced BCVA (all P < 0.05). For each diopter increase in myopia, mean BCVA decreased by 0.01 LogMAR in photopic conditions and 0.02 LogMAR in mesopic conditions (both P < 0.001). The mean BCVA reduced by 0.05 LogMAR (P = 0.003) and 0.04 LogMAR (P = 0.037), under photopic and scotopic lighting conditions respectively, for each 100-µm decrease in RT. CONCLUSIONS: Both the severity of myopia and macular RT independently affect visual performance under photopic, mesopic, and simulated NVG conditions.

Calculating the predicted retinal thickness from spectral domain and time domain optical coherence tomography - comparison of different methods.

PURPOSE: To compare the accuracy of different methods of calculating predicted central retinal thickness values in order to allow comparison between results of spectral-domain optical coherence tomography (SD-OCT) and time-domain OCT (TD-OCT) devices. METHODS: In a prospective cohort study, 100 consecutive healthy individuals without ocular disease underwent sequential scanning with SD-OCT (Spectralis OCT) and TD-OCT (Stratus OCT). A group of 60 eyes was used to generate the conversion equations, which were tested on the remaining 140 eyes. Four equations were used: 1. Mean difference between SD-OCT and TD-OCT; 2. Multiplying a ratio by the original retinal thickness; 3. Linear regression analysis using retinal thickness; and 4. Regression analysis using retinal thickness and spherical equivalent. All four methods were used to calculate predicted SD-OCT values from TD-OCT measurements, and vice versa. RESULTS: For all four equations, the predicted SD-OCT central retinal thickness values were similar to the actual SD-OCT, with mean difference ranging from 0.78 to 1.01 µm, and intraclass correlation coefficients >0.88. Both regression equations and mean difference showed greater accuracy, with variation between calculated and actual retinal thickness values ≤5 µm in 60% of eyes. In contrast, the ratio method was less accurate, with 15.8 % of eyes showing differences >15 µm. Similar results were found for predicted TD-OCT values. CONCLUSIONS: Several methods can be used to convert central retinal thickness values from SD-OCT to the predicted TD-OCT value, or vice versa, with high degrees of accuracy and reliability. These methods may allow comparison of OCT values from SD-OCT and TD-OCT devices in clinical trials and standard patient care.

Topographic variation of choroidal and retinal thicknesses at the macula in healthy adults.

BACKGROUND/AIMS: To determine the topographic variation of macular choroidal and retinal thicknesses (RTs) in normal eyes and their relationship with refractive error. METHODS: Spectral domain optical coherence tomography with enhanced depth imaging was performed on 124 healthy participants using a standardised imaging protocol. Manual segmentation of choroidal boundaries was performed by trained graders, and mean choroidal thickness (CT) was compared with mean RT in corresponding sectors of the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. RESULTS: Mean central subfield CT was 322.2 µm. The choroid was thickest at the temporal and superior sectors (323.1-338.1 µm), followed by inferior sectors (314.0-321.8 µm), and thinnest at the nasal sectors (232.8-287.8 µm). In contrast, the retina was thicker nasally (343.4 µm) and thinner temporally (287.1 µm). CT was thickest among emmetropes in all ETDRS subfields and became thinner progressively among low, moderate and high myopes (p<0.001). The variation of both choroidal and RTs among refractive error groups resulted in different topographic patterns at the macula. CONCLUSION: There is significant topographic variation of choroidal and RTs at different regions of the macula, with progressive change of choroidal thickness in all sectors based on the refractive status of the eye.

A novel technique of adjusting segmentation boundary layers to achieve comparability of retinal thickness and volumes between spectral domain and time domain optical coherence tomography.

PURPOSE: The quantitative assessment of retinal thickness and volume varies according to the optical coherence tomography (OCT) machine used due to differences in segmentation lines. We describe a novel method of adjusting the segmentation lines of spectral-domain OCT (SD-OCT) to enable comparison with time-domain OCT (TD-OCT), and assess factors affecting its accuracy. METHODS: In a prospective study, SD-OCT (Spectralis OCT) and TD-OCT (Stratus OCT) were sequentially performed on 200 eyes of 100 healthy individuals. Central retinal thickness (CRT), central point thickness (CPT), and 1-mm volume of the Early Treatment Diabetic Retinopathy Study grid were compared between the two machines. The segmentation lines on SD-OCT were manually adjusted by a trained operator and the parameters compared again with TD-OCT. RESULTS: The mean CRTs of Spectralis and Stratus were significantly different (268.2 µm vs. 193.9 µm, P < 0.001). After adjustment of segmentation lines, the mean adjusted Spectralis CRT was 197.3 µm, with the difference between SD-OCT and TD-OCT measurements decreasing from 74.3 µm to 3.4 µm (P < 0.001). The difference between the adjusted Spectralis and Stratus CRTs was smallest for high myopes (≤ -6.0 diopters [D]) compared with those with moderate and low myopia (1.5 µm vs. 3.5 µm and 4.6 µm, respectively; P < 0.001). Similar trends were obtained for central 1-mm volumes and CPT. Interoperator and intraoperator repeatability for adjustment of the segmentation lines were good, with an intraclass correlation of 0.99 for both. CONCLUSIONS: Manual adjustment of SD-OCT segmentation lines reliably achieves retinal thickness and volume measurements that are comparable to that of TD-OCT. This is valuable to allow comparisons in multicenter clinical trials where different OCT machines may be used.