Mohammed Riyazuddin

A comparison of the diagnostic ability of vessel density and structural measurements of optical coherence tomography in primary open angle glaucoma

Purpose To compare the diagnostic abilities of vessel density measurements of the optic nerve head (ONH), peripapillary and macular regions on optical coherence tomography (OCT) angiography in eyes with primary open angle glaucoma (POAG) with that of the ONH rim area, peripapillary retinal nerve fiber layer (RNFL) thickness and the macular ganglion cell complex (GCC) thickness measurements. Methods In a cross sectional study, 78 eyes of 50 control subjects and 117 eyes of 67 POAG patients underwent vessel density and structural measurements with spectral domain OCT. POAG was diagnosed based on the masked evaluation of optic disc stereo photographs. Area under receiver operating characteristic curves (AUC) and sensitivities at fixed specificities of vessel densities in ONH, peripapillary and macular regions were compared with rim area, RNFL and GCC thickness. Results The AUC (sensitivity at 95% specificity) of average vessel densities within the ONH, peripapillary and macular region were 0.77 (31%), 0.85 (56%) and 0.70 (18%) respectively. The same of ONH rim area, average RNFL and GCC thickness were 0.94 (83%), 0.95 (72%) and 0.93 (62%) respectively. AUCs of vessel densities were significantly lower (p<0.05) than that of the corresponding structural measurements. Pre-treatment IOP (coefficient: 0.08) affected (p<0.05) the AUC of ONH vessel density but not of any other vessel density or structural measurements. Conclusions Diagnostic abilities of ONH, peripapillary and the macular vessel densities in POAG were significantly lower than ONH rim area, peripapillary RNFL and macular GCC measurements respectively. At fixed levels of glaucoma severity, the diagnostic ability of the ONH vessel density was significantly greater in eyes with higher pre-treatment IOP.

Repeatability of vessel density measurements of optical coherence tomography angiography in normal and glaucoma eyes

Aims To compare the intrasession repeatability of peripapillary and macular vessel density measurements of optical coherence tomography angiography (OCTA) in normal and glaucoma eyes, and to evaluate the effect of signal strength of OCTA scans on the repeatability. Methods In a cross-sectional study, three optic nerve head scans each of 65 eyes (30 normal, 35 glaucoma eyes) and three macular scans each of 69 eyes (35 normal, 34 glaucoma eyes) acquired in the same session with OCTA were analysed. Repeatability was assessed using within-subject coefficient of repeatability (CRw) and variation (CVw). Effect of signal strength index (SSI) on repeatability was evaluated with repeated-measures mixed-effects models. Results CRw (%) and CVw (%) of peripapillary measurements in normal eyes ranged between 3.3 and 7.0, and 2.5 and 4.4 respectively, and that in glaucoma eyes between 3.5 and 7.1, and 2.6 and 6.6. For the macular, these measurements ranged between 4.1 and 6.0, and 3.3 and 4.7 in normal eyes and 4.3 and 6.9, and 3.7 and 5.6 in glaucoma eyes. Repeatability estimates of most measurements were similar in normal and glaucoma eyes. Vessel densities of both peripapillary and macular regions significantly increased with increase in SSI of repeat scans (coefficients ranging from 0.15 to 0.38, p<0.01 for all associations). Conclusions Repeatability estimates of OCTA measured peripapillary and macular vessel densities were similar in normal eyes and eyes with glaucoma. SSI values of the scans had a significant effect on the repeatability of OCTA with the vessel density values increasing in scans with higher SSI values.

Determinants of Peripapillary and Macular Vessel Densities Measured by Optical Coherence Tomography Angiography in Normal Eyes.

Purpose: The aim of this study was to evaluate the effect of subject-related (age, sex, and systemic hypertension and diabetes), eye-related (refractive error, optic disc size), and technology-related (signal strength index, SSI of the scans) determinants on the peripapillary and macular vessel densities measured with optical coherence tomography angiography (OCTA) in normal eyes. Methods: In a cross-sectional study, 181 normal eyes of 107 subjects (45 men, 62 women, median age: 50 y, range: 18 to 77 y) underwent OCTA imaging. Linear mixed models were used to analyze the effect of the determinants on the peripapillary and macular vessel densities measured with OCTA. Results: It was found that age and optic disc size did not affect the vessel densities of any of the regions (P>0.05 for all associations). En face optic disc (coefficient: 1.67, P<0.001) and most of the peripapillary vessel densities were higher in female individuals. En face disc (coefficient=−1.88, P=0.02) and most of the peripapillary vessel densities were lower, whereas the parafoveal vessel density was higher (coefficient=2.32, P=0.01), in subjects with hypertension. Most of the vessel densities were lower in subjects with diabetes. SSI showed a statistically significant association with the vessel densities of all regions (coefficients: 0.14 to 0.27 for peripapillary and 0.20 to 0.27 for macular sectors). Conclusions: Most of the peripapillary vessel densities were higher in female subjects. Hypertension and diabetes also affected the vessel densities. Vessel densities in all the regions were significantly higher in scans with higher SSI. These results should be considered when interpreting the vessel densities in retinal diseases and glaucoma.

Relationship of Optic Nerve Structure and Function to Peripapillary Vessel Density Measurements of Optical Coherence Tomography Angiography in Glaucoma

Purpose: To evaluate the sectoral and global structure-structure (vessel density-retinal nerve fiber layer thickness) and structure-function (vessel density-visual sensitivity loss) relationships of peripapillary vessel density measurements on optical coherence tomography angiography in primary open-angle glaucoma and to determine if fractional polynomial (FP) models characterize the relationships better than linear models. Materials and Methods: In a cross-sectional study, structure-structure and structure-function relationships of peripapillary vessel densities were determined in 227 eyes of 143 subjects (63 control and 164 primary open-angle glaucoma eyes) who had undergone standard automated perimetry and optical coherence tomography testing within 6 months of each other, using linear and FP models. FP model evaluates the relationship between the dependent and the best-fitting fractional powers of the independent variable. Strength of relationship was reported as coefficient of determination (R2). Results: R2 values for structure-structure associations using linear models (0.53 for superotemporal sector, 0.61 for inferotemporal, and 0.53 for average measurements) were significantly less (P<0.05) than that determined using FP models (0.57, 0.65, and 0.55, respectively). R2 values for structure-function associations using linear models (0.35 for superotemporal vessel density-inferotemporal visual sensitivity loss, 0.49 for inferotemporal vessel density-superotemporal visual sensitivity loss, and 0.39 for average vessel density-average visual sensitivity loss) were significantly less than that determined using FP models (0.43, 0.58, and 0.47, respectively). Conclusions: The inferotemporal peripapillary vessel density showed the strongest association with the corresponding retinal nerve fiber layer thickness and visual sensitivity loss in the global and sectoral regions studied. The FP models were significantly better than linear models in describing these relationships.

Predicting the Magnitude of Functional and Structural Damage in Glaucoma From Monocular Pupillary Light Responses Using Automated Pupillography

Purpose: To predict the magnitude of functional damage [mean deviation (MD) on visual field examination] and structural damage [retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) thickness on spectral domain optical coherence tomography] in glaucoma from monocular pupillary light response measurements using automated pupillography. Methods: In total, 59 subjects (118 eyes) with either a confirmed or suspected diagnosis of glaucoma underwent automated pupillography, along with visual fields and spectral domain optical coherence tomography examinations. Association between pupillary light response measurements of each eye [amplitude of constriction, latency of onset of constriction (Loc), latency of maximal constriction (Lmaxc), velocity of constriction and velocity of redilation] and corresponding MD, average RNFL, and average GCC measurements were evaluated using univariate and multivariate regression analysis after accounting for the multicollinearity. Goodness of fit of the multivariate models was evaluated using coefficient of determination (R2). Results: Multivariate regression models that contained Loc and Lmaxc showed the best association with MD (R2 of 0.30), average RNFL thickness (R2=0.18) and average GCC thickness (R2=0.26). The formula that best predicts the MD could be described as: MD=−14.06−0.15×Loc+0.06×Lmaxc. The formula that best predicts the average RNFL thickness could be described as: Average RNFL thickness=67.18−0.22×Loc+0.09×Lmaxc. Conclusions: Glaucomatous damage as estimated by MD, RNFL, and GCC thickness measurements were best predicted by the latency parameters (Loc and Lmaxc) of pupillography. Worsening of glaucomatous damage resulted in a delayed onset of pupillary constriction and a decreased Lmaxc.

Optical Coherence Tomography Angiography Vessel Density Measurements in Eyes With Primary Open-Angle Glaucoma and Disc Hemorrhage

Purpose: To compare the vessel density measurements of optic nerve head, peripapillary and macular regions in severity-matched primary open-angle glaucoma (POAG) eyes with and without disc hemorrhage (DH) using optical coherence tomography (OCT) angiography, and to compare their diagnostic abilities with that of the rim area, retinal nerve fiber layer and the ganglion cell complex thickness measurements on OCT. Methods: In a cross-sectional study, 66 eyes of 46 control subjects, 34 eyes of 33 POAG patients with DH (median mean deviation=−3.7 dB) and 63 eyes of 43 POAG patients without DH (median mean deviation=−3.8 dB) underwent imaging with spectral domain OCT. Area under receiver operating characteristic curves (AUC) and 5sensitivities at 90% specificity of vessel density and structural measurements in POAG eyes with DH were compared with those in POAG eyes without DH. Results: Most of the vessel density and structural measurements were similar (P>0.05) in POAG eyes with and without DH. Whole enface vessel density of the disc scan and inferotemporal peripapillary vessel density showed the best AUC and sensitivity at 90% specificity both in POAG eyes with DH (0.82, 56% and 0.75, 59%) and without DH (0.91, 73% and 0.83, 67%). AUCs and sensitivities of vessel density and structural measurements of POAG eyes with and without DH were statistically similar (P>0.05). Conclusions: OCT angiography measured vessel densities and their diagnostic abilities in POAG eyes with and without DH were similar. This suggests that the cause of DH in POAG is unlikely to be vascular abnormality.

Repeatability and comparability of peripapillary vessel density measurements of high-density and non-high-density optical coherence tomography angiography scans in normal and glaucoma eyes

Aims To compare the peripapillary vessel density (VD) measurements of high-density (HD) and non-HD optical coherence tomography angiography (OCTA) scans in normal and glaucoma eyes, and to evaluate the intrasession repeatability of VD measurements of HD scans. Methods In a cross-sectional study, 46 normal (33 subjects) and 89 glaucoma (64 patients) eyes underwent 3 HD and 1 non-HD optic nerve head OCTA scans in the same session. Agreement in VD measurements between HD and non-HD scans was assessed using Bland and Altman analysis. Repeatability of the VD measurements of HD scans was assessed using within-subject coefficient of repeatability (CRw) and variation (CVw). Results The mean difference in the VDs ranged between 0.7% (temporal sector VD) and 2.0% (inferonasal sector VD), with HD scans showing significantly greater VD values than non-HD scans. The 95% limits of agreement (LoA) in glaucoma eyes ranged between −2.0% and 5.0% for whole enface VD and between −4.8% and 9.6% for superotemporal VD. CRw (%) and CVw (%) of VD measurements of HD scans ranged from 3.0 to 4.9 and from 2.0 to 3.1 in normal eyes. The same ranged from 3.2 to 6.7 and from 2.6 to 4.8, respectively, in glaucoma eyes. Conclusions VD of HD scans was higher than that of non-HD scans. The wide 95% LoA indicates that the VD measurements of HD and non-HD scans cannot be used interchangeably. Test–retest repeatability of VDs on HD scans was as high as 6%. These results should be considered while using OCTA for longitudinal evaluation of glaucoma.

Predicting the intereye asymmetry in functional and structural damage in glaucoma using automated pupillography.

To predict the intereye asymmetry in functional (mean deviation, MD on visual field, VF) and structural (retinal nerve fibre layer, RNFL and ganglion cell complex, GCC thickness on spectral domain optical coherence tomography, SDOCT) measurements in glaucoma using the automated pupillography parameters.