Interocular symmetry of optical coherence tomography parameters in healthy children and adolescents

Evaluation of interocular asymmetry of optical coherence tomography (OCT) parameters is important for the glaucoma and optic neuropathies. This study was performed to evaluate the interocular asymmetry of OCT parameters in healthy children and adolescents. The circumpapillary retinal nerve fiber layer (RNFL) thickness, optic nerve head (ONH) parameters, and macular ganglion cell-inner plexiform layer (GCIPL) thickness were measured in 620 eyes of 310 healthy children and adolescents using Cirrus HD-OCT. The interocular asymmetry (right eye–left eye) in the OCT parameters was analyzed. The mean ± standard deviation age was 10.3 ± 3.7 years (range 5–17). The right eyes showed thinner superior quadrant RNFL, thicker nasal and temporal quadrant RNFL, lesser rim and disc areas, and thinner average, superior, and superonasal GCIPL than the left eyes (P < 0.05). The 2.5th and 97.5th percentile interocular difference tolerance limits were − 9.0 μm and 11.0 μm for average RNFL thickness, − 0.21 and 0.18 for average cup-to-disc ratio, and − 4.0 μm and 4.0 μm for average GCIPL thickness, respectively. Interocular differences were found in RNFL thickness, ONH parameters, and GCIPL thickness in healthy children and adolescents. These findings should be considered when comparing OCT parameters between the right and left eyes.

Patients with unilateral retinal vein occlusion show reduced radial peripapillary capillary density in their fellow eyes

Background To evaluate the radial peripapillary capillary (RPC) density in the fellow eyes of unilateral retinal vein occlusion (RVO) patients using optical coherence tomography angiography (OCTA), and further analyze the correlation between RPC density and peripapillary retinal nerve fiber layer (RNFL) thickness. Methods Seventy-eight unilateral RVO patients and 70 normal controls were included in the study. OCTA was conducted with the 4.5 × 4.5-mm scan pattern centered on the optic nerve head, and the RPC density and peripapillary RNFL thickness were quantified. Results The peripapillary RNFL in the RVO fellow eyes was significantly thinner than in normal controls in the average, inferior-hemisphere, inferior quadrant, and temporal quadrant (P < 0.05, respectively). The RPC density in the fellow eyes was also significantly lower in the average, inferior-hemisphere, nasal quadrant, and temporal quadrant ((P < 0.05, respectively). There were no significant differences in RNFL thickness and RPC density between branch RVO fellow eyes and central RVO fellow eyes. Pearson’s correlation analysis showed significant positive correlations between the RPC density and RNFL thickness in all measurements (P < 0.001, respectively). Conclusions The regional RPC density was reduced in the RVO fellow eyes, which might contribute to peripapillary RNFL thinning in the corresponding region, suggesting the influence of systemic risk factors on RVO. OCTA may offer new insights into the pathophysiology of RVO.

Frosted Branch Angiitis (FBA): A case report

The purpose of the study is to describe a rare case report for raising the awareness of existence of this rare ocular disease and also review the characteristics of this disease. A 35-year-old man presented with acute vision loss in both eye after high grade fever. On fundoscopic examination flower petal pattern blood vessel sheathing in temporal quadrant of both eyes was seen. A provisional diagnosis of frosted branch angiitis was considered. The patient responds promptly with Intravenous and oral corticosteroid. A total of 58 cases have been reported in worldwide literature. The disease is likely to represent a common immune pathway in response to multiple infective agents. CBMJ 2020 July: Vol. 09 No. 02 P: 42-44

To measure angle of anterior chamber using Topcon SD-OCT: A new technique

The proposed new method of measuring angle of anterior chamber is an effective method of measuring the angles. Identification of narrow anterior chamber angle is important for glaucoma screening and prophylactic treatment prevents acute angle closure glaucoma event.Aim of this study wasto measure the angle of anterior chamber using Topcon spectral domain optical coherence tomography (SD OCT).In this cross-sectional study 120 normal subjects above the age of 40 years were enrolled. The study was done at the tertiary health care center of central Indian. All volunteers had visual acuity of at least 6/9 with no ocular diseases. Using OCT the angle opening distance (AOD-500), trabecular–iris angle (TIA) and trabecular-iris space area (TISA-500) were measured. In this study the mean AOD was 0.430 µm in nasal and 0.433 µm in temporal quadrant. The mean TISA in nasal was 0.405 µm and temporal quadrant was 0.408 µm. While the mean trabecular iris angle (TIA) was 26.9° in nasal and 26.01° in temporal quadrant. The study proved that the proposed method of measuring AOD, TISA, TIA is the effective method as the Topcon-2000 OCT does not have any inbuilt software like that of other ASOCT machines.

Study of retinal nerve fiber layer thickness in chronic kidney disease patients

To compare the RNFL thickness between CKD patients and age matched healthy controls and to correlate RNFL thickness with duration of CKD. RNFL thickness was also assessed in CKD patients with and without haemodialysis.: One hundred and fifty eyes were included in the study and were labeled as group A. Equal number of age matched controls were included in group B. RNFL thickness was measured using optical coherence tomography for optic nerve head (ONH) scan.Mean of average RNFL thickness was studied to be thinner in group A in comparison to group B. Statistically significant thinning was also noted in superior and inferior quadrant of group A. Increase in average RNFL thickness and increase in superior and temporal quadrant RNFL thickness was noted in HD group as compared to non- HD group. A negative correlation was noted between RNFL thickness and duration of CKD. : This study concluded that RNFL thickness was found to be thinner in CKD patients as compared to healthy individuals. However RNFL thickness was found to be thicker in HD group as compared to non- HD group.

Impacts of Mild and Moderate Acute Hypoxia on Visual Contrast Sensitivity

Introduction: Acute hypoxia could hamper the visual performance during the aviation. In the study, we aimed to investigate the effects of acute hypoxia on the contrast sensitivity (CS) and the color contrast sensitivity (CCS).Methos: 12 healthy volunteers (aged 20-22 years old) were selected for CS and CCS examination at altitude of 300m, 3000m and 4500m by applying the hypobaric cabin to simulate acute hypoxia (3000m in height = mild hypoxia; 4500m = moderate hypoxia). All data were collected after the heart rate and the blood oxygen saturation became stable, and were analyzed by the paired student’s t-test. Results: The CS at the spatial frequency of 1.5 Cpd was significantly increased at the altitude of 3000m (P<0.05), while CS at the higher spatial frequencies was not significantly affected. The CS of 1.5 and 3.0 Cpd was increased at the altitude of 4500m (P<0.05), while the CS of higher spatial frequency did not change significantly. With the increased degree of hypoxia, the overall CCS was increased with a statistical difference at 4500m (P<0.05). The CCS of the temporal superior and inferior quadrants were significantly affected (P<0.05), while those in other quadrants were significantly changed. Conclusions: Mild and moderate acute hypoxia could affect the CS in the low spatial frequency. With the increased degree of acute hypoxia, CCS deteriorates with the temporal quadrant more vulnerable to be affected.

Effects of Venoconstrictive Thigh Cuffs on Dry Immersion-Induced Ophthalmological Changes

Neuro-ophthalmological changes named spaceflight associated neuro-ocular syndrome (SANS) reported after spaceflights are important medical issues. Dry immersion (DI), an analog to microgravity, rapidly induces a centralization of body fluids, immobilization, and hypokinesia similar to that observed during spaceflight. The main objectives of the present study were 2-fold: (1) to assess the neuro-ophthalmological impact during 5 days of DI and (2) to determine the effects of venoconstrictive thigh cuffs (VTC), used as a countermeasure to limit headward fluid shift, on DI-induced ophthalmological adaptations. Eighteen healthy male subjects underwent 5 days of DI with or without VTC countermeasures. The subjects were randomly assigned into two groups of 9: a control and cuffs group. Retinal and optic nerve thickness were assessed with spectral-domain optical coherence tomography (OCT). Optic nerve sheath diameter (ONSD) was measured by ocular ultrasonography and used to assess indirect changes in intracranial pressure (ICP). Intraocular pressure (IOP) was assessed by applanation tonometry. A higher thickness of the retinal nerve fiber layer (RNFL) in the temporal quadrant was observed after DI. ONSD increased significantly during DI and remained higher during the recovery phase. IOP did not significantly change during and after DI. VTC tended to limit the ONSD enlargement but not the higher thickness of an RNFL induced by DI. These findings suggest that 5 days of DI induced significant ophthalmological changes. VTC were found to dampen the ONSD enlargement induced by DI.

Automated Sectoral Quantitative Analysis of Parafoveal Microvascular Status and Association with Structure in Diabetic Macular Edema

Purpose: To evaluate the integrity of the capillary plexuses, their relationship with each other, and their association with structural changes in a sectoral manner in diabetic macular edema (DME).Methods: The vessel density (VD) was measured in inferior, superior, nasal and temporal (İ, S, N, T) parafovea in the superficial capillary plexus (SCP) and deep capillary plexus (DCP). The integrity of the external limiting membrane (ELM) and ellipsoid zone (EZ) were evaluated in B-scan images.Results: In the SCP, only superior and nasal VD was significantly lower (P: 0.0001 and P: 0.020, respectively) while in the DCP, only temporal VD was significantly lower in the DME eyes (P: 0.034). There was no correlation between the VD of SCP and DCP in the corresponding quadrants (all P > 0.05). The FAZ area was significantly greater (both superficial and deep) in DME eyes than in control eyes (P > 0.05). ELM disruptions were not affected by the corresponding VDs in the SCP (all P> 0.05), but nasal and temporal quadrant ELM disruptions were affected by VDs in the DCP in the corresponding quadrants (P: 0.005 nasal, P: 0.001 temporal). EZ disruptions were not affected by the corresponding VDs in the SCP and DCP (all P> 0.05).Conclusions: The SCP was affected in more quadrants than the DCP and probably independently from each other. There was an association with the ELM and the DCP, especially in nasal and temporal quadrants, but there was not an association between the EZ and SCP or DCP.

Topographic Quadrant Analysis of Peripapillary Superficial Microvasculature in Optic Disc Drusen

Background: Limited information is known about the topographic effect of optic disc drusen (ODD) on peripapillary retinal nerve fibers and microvasculature.Objective: This study aims to understand the structural and functional impact of ODD in different quadrants of the optic disc.Methods: We performed a retrospective case-control study of 22 ODD patients (34 eyes) and 26 controls (33 eyes) to compare optical coherence tomography (OCT) retinal nerve fiber layer (RNFL), OCT angiography (OCTA), and corresponding static perimetry mean deviation (MD) calculated using the modified Garway-Heath map in different quadrants of the optic disc. OCTA was analyzed using custom MATLAB script to measure six parameters in a peripapillary annulus with large vessel removal: vessel area density (VAD), vessel skeleton density (VSD), vessel perimeter index (VPI), vessel complexity index (VCI), flux, and vessel diameter index (VDI).Results: Quadrant analysis revealed that OCTA VAD and VCI were significantly decreased in superior, nasal, and inferior but not temporal quadrant. RNFL, VSD, and VPI were significantly impacted only in the superior and nasal quadrants. Corresponding visual field MDs in all ODD eyes were not different in the four quadrants, although eyes with MD equal or worse than −5 dB (32%) had worst visual field corresponding to the superior quadrant of the optic disc (inferior arcuate visual field). Structure-structure comparison of OCT and OCTA showed high correlation of RNFL with multiple OCTA measurements in the superior, nasal, and inferior quadrants but not temporal quadrant. Structure-function analysis revealed significant correlation of VAD and VCI and visual field MD in every quadrant, but RNFL was only significantly correlated in the superior and inferior quadrants.Conclusions: Peripapillary VAD and VCI are decreased in more quadrants than RNFL, supporting the clinical utility of performing OCTA in addition to OCT. Consistent with the most common locations of ODD, five OCT/OCTA measurements (VAD, VCI, RNFL, VSD, VPI) are decreased in the superior and nasal quadrants. OCT/OCTA measurements were significantly impacted in contrast to the relatively mild effect on corresponding visual field MD, consistent with the idea that a decrease in objective structural and vascular measurements occurs without parallel change in subjective visual function in ODD.

Correlation between the Nonperfusion Area on Ultra-Widefield Fluorescein Angiography and Nonflow Area on Optical Coherence Tomographic Angiography in Retinal Vein Occlusion

Aims. To compare the relationship between the nonperfusion area (NPA) on ultra-widefield fluorescein angiography (UWFFA) and the nonflow area (NFA) on optical coherence tomographic angiography (OCTA) in retinal vein occlusion (RVO). Methods. Cross-sectional study. 46 eyes of 46 RVO patients who underwent UWFFA and OCTA. NPA and ischemic index (ISI) were quantified on UWWFA. NFA, vessel density (VD) of the superficial capillary plexus (SCP), the deep capillary plexus (DCP), and the size foveal avascular zone (FAZ) on 3 ∗ 3 mm OCTA were measured. The association of the NPA and ISI on UWWFA and the parameters on OCTA were analyzed. Spearman correlation was used for statistical testing. Results. The NPA and ISI on UWFFA were significantly correlated with the NFA on OCTA in RVO, and r values were 0.688 ( p < 0.01 ) and 0.680 ( p < 0.01 ), respectively. VD in the SCP of the temporal quadrant was negatively correlated with NPA and ISI, and r values were −0.346 ( p < 0.05 ) and −0.337 ( p < 0.05 ), respectively. VD in the DCP of the temporal quadrant was negatively correlated with the NPA, and the r value was −0.246 ( p < 0.05 ). No significant correlation was found between the NPA and ISI on UWFFA and VD of other quadrants in the SCP or DCP and the FAZ area on OCTA. Conclusion. NPA in the peripheral retina was correlated with NFA in macula. NFA detected by OCTA could be an indicator of the ischemic status in RVO.