Contrast Discrimination and Global Form Perception in Primary Open-Angle Glaucoma and Primary Angle-Closure Glaucoma.

Purpose: This study explored early (contrast discrimination) and intermediate (global form perception) visual processing in primary subtypes of glaucoma: primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG). We aimed to understand early and intermediate visual processing in POAG and PACG, matched for similar visual field defect severity. Methods: Early visual processing was measured using a contrast discrimination task described by Porkorny and Smith (1997), and intermediate processing using a global form perception task using glass pattern coherence thresholds. Thresholds were determined centrally and at a single midperipheral location (12.5°) in a quadrant without visual field defects. Controls were tested in corresponding quadrants to individuals with glaucoma. Results: Sixty participants (20 POAG, 20 PACG, and 20 age-matched controls), aged 50 to 77 years, were included. Visual field defects were matched between POAG and PACG, with mean deviation values of -6.53 ± 4.46 (range: -1.5 to -16.85) dB and -6.2 ± 4.24 (range: -1.37 to -16.42) dB, respectively. Two-Way ANOVA revealed significant differences in thresholds between the glaucoma groups and the control group for both contrast discrimination and global form perception tasks, with higher thresholds in the glaucoma groups. Post hoc analyses showed no significant contrast discrimination difference between POAG and PACG, but POAG had significantly higher thresholds than PACG for form perception. Conclusions: In form perception, POAG showed slightly worse performance than PACG, suggesting that individuals with POAG may experience more severe functional damage than PACG of similar visual field severity.

Determination of Refractive Error Using Direct Ophthalmoscopy in Children.

Purpose: Refractive error is a major cause of visual impairment in children and its early detection can prevent ocular morbidity such as amblyopia and strabismus. Brückner test is a comprehensive test which can be easily administered in children using a direct ophthalmoscope. We aimed to determine refractive error in children by analysis of the red reflex using modified Brückner test. Patients and Methods: This prospective observational study was conducted on 683 undilated eyes of 683 children aged four to 10 years. They were evaluated with a direct ophthalmoscope from one meter in a dimly lit room. The characteristics of the red reflex and crescent obtained were compared with photoscreener refraction value and analyzed. Results: The presence of superior crescent was associated with hypermetropia (Chi square 37.11, p < 0.001, kappa = 0.15) and inferior crescent with myopia (Chi square 157.29, p < 0.001, kappa = 0.477). Superior crescent was 98.4% sensitive in detecting hypermetropia. Hypermetropia greater than +1.5D, was associated with larger superior crescent crossing horizontal midline of pupil (Chi square = 5.29, p = 0.021). Conclusion: The modified Brückner test is useful in detection and quantification of refractive error in children. It is easy, simple, quick and can be employed in the community as a screening test to detect potentially amblyogenic refractive errors.

Visual Field Evaluation Using Zippy Adaptive Threshold Algorithm (ZATA) Standard and ZATA Fast in Patients With Glaucoma and Healthy Individuals.

Purpose: To evaluate visual fields obtained with Zippy Adaptive Threshold Algorithm (ZATA) Standard and ZATA Fast from patients with glaucoma and healthy individuals. Methods: Fifty-five patients with glaucoma (median mean deviation [MD], -7.6 dB; interquartile range [IQR], -15.3 to -2.6 dB) and 22 healthy participants (median MD, -0.6 dB; IQR, -1.7 to 0.2 dB) performed ZATA Standard and ZATA Fast tests on a Henson 9000 perimeter and Swedish Interactive Thresholding Algorithm (SITA) Standard and SITA Fast tests on a Humphrey Field Analyzer. Tests were repeated within 90 days (median, 14 days; range, 7-26 days) to evaluate the test-retest variability. Results: The mean difference between the MD of the ZATA Standard and SITA Standard tests was 1.7 dB (95% confidence interval [CI], 0.9-2.4). Between ZATA Fast and SITA Fast, it was 0.9 dB (95% CI, 0.2-1.5 dB). Although there were systematic differences between the distributions of sensitivity estimates with ZATA and SITA, they did not affect the overall representation of damage by these tests. ZATA Standard and ZATA Fast were approximately 30% and 6% faster, respectively, than the corresponding SITA tests. Conclusions: ZATA Standard and ZATA Fast are suitable for clinical practice. However, differences between ZATA and SITA tests suggest that they should not be used interchangeably when patients with glaucoma are followed over time. Translational Relevance: This study examined the characteristics of ZATA visual field tests in a clinical population, and it supports the adoption of these tests for assessing patients with glaucoma.

HPLC-LED-Induced Fluorescence Analysis of Tear Fluids: An Objective Method for Primary Open Angle Glaucoma Diagnosis.

PURPOSE: The study showcased the application of the lab-assembled HPLC-LED-IF system to analyze proteins in tear fluid samples collected from individuals diagnosed with primary open-angle glaucoma (POAG). METHODS: Clinical application of the said technique was evaluated by recording chromatograms of tear fluid samples from control and POAG subjects and by analyzing the protein profile using multivariate analysis. The data analysis methods involved are principal component analysis (PCA), Match/No-Match, and artificial neural network (ANN) based binary classification for disease diagnosis. RESULTS: Mahalanobis distance and spectral residual values calculated using a standard calibration set of clinically confirmed POAG samples for the Match/No-Match test gave 86.9% sensitivity and 81.8% specificity. ANN with leaving one out procedure has given 87.1% sensitivity and 81.8% specificity. CONCLUSION: The results of the study revealed that the utilization of a 278 nm LED excitation in the HPLC system offers good sensitivity for detecting proteins at low concentrations allowing to obtain reliable protein profiles for the diagnosis of POAG.

Does the sampling frequency of an eye tracker affect the detection of glaucomatous visual field loss?

PURPOSE: Evidence suggests that eye movements have potential as a tool for detecting glaucomatous visual field defects. This study evaluated the influence of sampling frequency on eye movement parameters in detecting glaucomatous visual field defects during a free-viewing task. METHODS: We investigated eye movements in two sets of experiments: (a) young adults with and without simulated visual field defects and (b) glaucoma patients and age-matched controls. In Experiment 1, we recruited 30 healthy volunteers. Among these, 10 performed the task with a gaze-contingent superior arcuate (SARC) scotoma, 10 performed the task with a gaze-contingent biarcuate (BARC) scotoma and 10 performed the task without a simulated scotoma (NoSim). The experimental task involved participants freely exploring 100 images, each for 4 s. Eye movements were recorded using the LiveTrack Lightning eye-tracker (500 Hz). In Experiment 2, we recruited 20 glaucoma patients and 16 age-matched controls. All participants underwent similar experimental tasks as in Experiment 1, except only 37 images were shown for exploration. To analyse the effect of sampling frequency, data were downsampled to 250, 120 and 60 Hz. Eye movement parameters, such as the number of fixations, fixation duration, saccadic amplitude and bivariate contour ellipse area (BCEA), were computed across various sampling frequencies. RESULTS: Two-way ANOVA revealed no significant effects of sampling frequency on fixation duration (simulation, p = 0.37; glaucoma patients, p = 0.95) and BCEA (simulation, p = 0.84; glaucoma patients: p = 0.91). BCEA showed good distinguishability in differentiating groups across different sampling frequencies, whereas fixation duration failed to distinguish between glaucoma patients and controls. Number of fixations and saccade amplitude showed variations with sampling frequency in both simulations and glaucoma patients. CONCLUSION: In both simulations and glaucoma patients, BCEA consistently differentiated them from controls across various sampling frequencies.

Comparison of clinical outcomes of Eyecryl toric and Alcon toric intra-ocular lenses - A real world study.

Purpose: To compare the visual outcomes and residual astigmatism following implantation of Eyecryl toric versus Alcon AcrySof IQ toric intra-ocular lenses (IOLs). Methods: This retrospective, observational study included 143 eyes of 141 patients who underwent phaco-emulsification, followed by implantation of Eyecryl toric IOL (n = 83 eyes) or Alcon toric IOL (n = 60 eyes) in an eye hospital in South India from 2018 to 2021. At 1 month post-op, the uncorrected distance visual acuity (UCVA), best corrected distance visual acuity (BCVA), and residual astigmatism of the toric IOL were compared and analyzed. Results: The mean pre-op corneal astigmatism was 2.02 ± 0.81 D and 1.70 ± 0.68 D in the Alcon and Eyecryl groups, respectively (P = 0.005). The mean post-op corneal astigmatism at 1 month was 0.50 ± 0.51 D and 0.36 ± 0.42 D in the Alcon and Eyecryl groups, respectively, with no statistically significant difference between them (P = 0.87). The mean post-op UCVA in logarithm of minimum angle of resolution (logMAR) at 1 month was similar between the groups at 0.17 ± 0.18 and 0.17 ± 0.16 in the Alcon and Eyecryl groups, respectively (P = 0.98). The mean post-op BCVA in logMAR at 1 month was 0.06 ± 0.09 and 0.03 ± 0.10 in the Alcon and Eyecryl groups, respectively (P = 0.02). Conclusion: Both Eyecryl toric and Alcon AcrySof IQ toric IOLs showed comparable post-operative outcomes in terms of UCVA and residual astigmatism. The post-op BCVA was clinically similar between groups but statistically better in the Eyecryl toric group.

Cháksu: A glaucoma specific fundus image database.

We introduce Cháksu-a retinal fundus image database for the evaluation of computer-assisted glaucoma prescreening techniques. The database contains 1345 color fundus images acquired using three brands of commercially available fundus cameras. Each image is provided with the outlines for the optic disc (OD) and optic cup (OC) using smooth closed contours and a decision of normal versus glaucomatous by five expert ophthalmologists. In addition, segmentation ground-truths of the OD and OC are provided by fusing the expert annotations using the mean, median, majority, and Simultaneous Truth and Performance Level Estimation (STAPLE) algorithm. The performance indices show that the ground-truth agreement with the experts is the best with STAPLE algorithm, followed by majority, median, and mean. The vertical, horizontal, and area cup-to-disc ratios are provided based on the expert annotations. Image-wise glaucoma decisions are also provided based on majority voting among the experts. Cháksu is the largest Indian-ethnicity-specific fundus image database with expert annotations and would aid in the development of artificial intelligence based glaucoma diagnostics.

The Effect of Specific Techniques of Nasal Breathing [Pranayama] on Intra-Ocular Pressure in Normal Individuals, a Randomized Trial.

Purpose: Glaucoma is an optic neuropathy where intraocular pressure is the only modifiable risk factor. Yoga is thought to adversely affect intra-ocular pressure (IOP) but we do not know if yogic breathing exercises can influence IOP. With this study, we aimed to determine the effect of specific nasal breathing techniques on intra-ocular pressure in normal individuals. Patients and Methods: One hundred and sixty-four normal subjects were randomly assigned to one of four specific breathing groups - right nostril breathing (RNB), left nostril breathing (LNB), alternate nostril breathing (ANB), normal breathing (NB). The IOP was measured in both eyes at baseline and following the breathing exercise; and the change was analyzed. Results: Eighty-five women and 79 men participated and there was no significant difference in baseline age or IOP between the groups. In RNB, IOP reduced significantly in both right and left eyes, from 14.3 ± 3.0mmHg to 13.9 ± 2.6mmHg, (p=0.022) and from 14.7 ± 3.2mmHg to 14.2 ± 3mmHg (p=0.016) respectively. In LNB, there was no significant IOP change in the right eye, whereas in the left eye, there was a significant reduction from 14.2 ± 2.7mmHg to 13.3 ± 2.5mmHg (p< 0.0001). There was no significant IOP change in ANB and NB. Conclusion: Specific breathing techniques like right and left nostril breathing, alternate nostril breathing are safe and do not raise IOP in normal subjects. Additionally, right and left nostril breathing techniques have a beneficial effect of lowering IOP.

Smartphone-Acquired Image Photogrammetry for Detection of Shallow Anterior Chamber.

PURPOSE: This study aimed to explore the role of smartphone imaging of the eye using two perspectives - anterior and temporal - in the detection of a shallow anterior chamber (AC). The AC depth (ACD) of an eye can be used as a surrogate marker for identification of eyes at risk of developing angle-closure disease. METHODS: A prospective observational study was conducted at a university teaching hospital in South India. Each eye was photographed with a smartphone using the two perspectives, followed by quantitative measurement of ACD using optical biometry. The percentage of nasal iris illuminated was measured from the image acquired using the flashlight method (anterior perspective), whereas pupil position relative to the cornea was measured from the image acquired using the temporal perpendicular method (temporal perspective). The receiver-operating characteristic curve and area under the curve (AUC) were studied for both perspectives independently for overall predictive accuracy in detection of shallow AC (ACD <2.7 mm, obtained by IOL Master). RESULTS: A total of 275 eyes were examined, of which 77 (28%) had an ACD <2.7 mm. The accuracy of detection of shallow AC was found to be 95.2% for both perspectives when used alone or in combination. AUC of the anterior perspective was 0.99 (95% CI 0.982-0.997). The AUC for the temporal perspective was 0.993 (95% CI 0.988-0.999). CONCLUSION: Smartphone-acquired image photogrammetry of an eye with anterior and temporal perspectives independently and in combination provided accuracy nearing 95% in the detection of shallow AC (ACD <2.7 mm). REGISTRATION: This trial was registered with the Clinical Trial Registry of India (CTRI/2018/09/015867, September 28, 2018).

A Novel Approach to Measuring Binocular Visual Fields in Glaucoma.

PRECIS: Combined average visual field index (VFI) is a simple, novel tool for binocular visual field which agrees with the existing binocular integrated visual field (IVF) model, as well as patient reported activity limitation in glaucoma. PURPOSE: The aim was to determine the correlation between novel models of binocular visual field with the existing IVF and glaucoma activity limitation (GAL-9). MATERIALS AND METHODS: IVFs were calculated from the monocular visual fields of 58 patients with primary glaucoma and the novel binocular visual field models termed binocular summation visual field index (BiSumVFI) and combined average visual field index (CaVFI) were derived from the VFIs of both fields. GAL-9 questionnaire was administered to the patients. The relationship between IVF and the 2 newer models of binocular fields were determined and the correlation of IVF, BiSumVFI, and CaVFI with GAL-9 was estimated. RESULTS: A very strong correlation was seen between IVF and BiSumVFI (r=-0.913, P<0.001, confidence interval: -0.958 to -0.821) and also between IVF and CaVFI (r=-0.896, P<0.001, confidence interval: -0.947 to -0.802). Linear regression analysis showed a significant R2 of 0.902 (P<0.001) to predict IVF from BiSumVFI and R2 of 0.847 (P<0.001) to predict IVF from CaVFI. IVF, BiSumVFI, and CaVFI correlated moderately and significantly with GAL-9 with correlation coefficients of 0.481, -0.499, and -0.505, respectively. CONCLUSION: The binocular summation VFI and combined average VFI models of binocular visual field are good predictors of IVF in glaucoma. They correlate well with the existing IVF model in estimating patients' perception of activity limitation in glaucoma.

Correlation of central field index (10-2 visual field analysis) and activity limitation with increasing severity of glaucoma using glaucoma activity limitation-9 questionnaire.

Purpose: The purpose of the study was to analyze the correlation between central field index (CFI) and activity limitation in glaucoma using glaucoma activity limitation-9 (GAL-9) questionnaire. Methods: This hospital-based, cross-sectional, noninterventional study, included 50 patients diagnosed with glaucoma, with field defect encroaching onto central 10° in Humphrey field analysis 30-2 program, in at least one eye. These patients underwent central 10-2 field analysis and CFI was calculated with the help of a calculator created by us. Patients with severe cognitive impairment were excluded and the rest completed the GAL-9 questionnaire. The data was analyzed to determine the correlation between the CFI and the GAL-9 scores. Results: There was a moderate correlation between CFI of better eye (r = -0.431, confidence interval "CI" -0.619 to -0.173, P < 0.002) and worse eye (r = -0.342, CI: -0.575 to - 0.058, P < 0.015) with GAL-9, the better eye showing a stronger correlation. Mean deviations (MD) of both better (r = -0.345, CI: -0.556 to -0.069, P < 0.014) and worse eye (r = -0.346, CI: -0.578 to -0.063 P < 0.014) showed similar moderate correlation. Vision of better eye (r = -0.398, CI: -0.577 to -0.210, P < 0.004) showed a stronger correlation with GAL-9 score than worse eye (r = -0.188, CI: -0.475 to 0.100, P < 0.192). Subscales of GAL-9 questionnaire also correlated with better eye status. "Finding dropped objects" had the strongest correlation to CFI of better eye (r = -0.676) and "adjusting to dim lights" had the weakest correlation (r = -0.052). Conclusion: The better eye status in glaucoma patients correlated better than worse eye with regard to activity limitation, signifying that the better eye has a greater influence on the quality of life and how patients perceive their disability. Furthermore, CFI showed a better correlation with GAL-9 score than MD.