Pattern Recognition Analysis Reveals Unique Contrast Sensitivity Isocontours Using Static Perimetry Thresholds Across the Visual Field

Abstract

PurposeTo determine the locus of test locations that exhibit statistically similar age-related decline in sensitivity to light increments and age-corrected contrast sensitivity isocontours (CSIs) across the central visual field (VF). We compared these CSIs with test point clusters used by the Glaucoma Hemifield Test (GHT).MethodsSixty healthy observers underwent testing on the Humphrey Field Analyzer 30-2 test grid using Goldmann (G) stimulus sizes I-V. Age-correction factors for GI-V were determined using linear regression analysis. Pattern recognition analysis was used to cluster test locations across the VF exhibiting equal age-related sensitivity decline (age-related CSIs), and points of equal age-corrected sensitivity (age-corrected CSIs) for GI-V.ResultsThere was a small but significant test size–dependent sensitivity decline with age, with smaller stimuli declining more rapidly. Age-related decline in sensitivity was more rapid in the periphery. A greater number of unique age-related CSIs was revealed when using smaller stimuli, particularly in the mid-periphery. Cluster analysis of age-corrected sensitivity thresholds revealed unique CSIs for GI-V, with smaller stimuli having a greater number of unique clusters. Zones examined by the GHT consisted of test locations that did not necessarily belong to the same CSI, particularly in the periphery.ConclusionsCluster analysis reveals statistically significant groups of test locations within the 30-2 test grid exhibiting the same age-related decline. CSIs facilitate pooling of sensitivities to reduce the variability of individual test locations. These CSIs could guide future structure-function and alternate hemifield asymmetry analyses by comparing matched areas of similar sensitivity signatures.

Consistency of Structure-Function Correlation Between Spatially Scaled Visual Field Stimuli and In Vivo OCT Ganglion Cell Counts

“…5B, GI, green interval), but one must be judicious with the application of a stimulus that is too small, as these are associated with increased variability. 49 The predicted GCc loss associated with a statistically significant (2 SD below normative data mean from Phu et al 45 ) visual sensitivity loss is less with GII (Fig. 5C, blue interval) compared to GIII and GV (Fig.…”

“…5B, GIII, orange interval). 45 While larger stimuli are associated with lower variability and were suggested to retain their ability to detect early visual sensitivity loss, 47 loss of sensitivity (Fig. 5B, GV, red interval) falls within the measurement variability and cannot be reliably detected.…”

“…5B, GV, red interval) falls within the measurement variability and cannot be reliably detected. 45 Conversely, GI is predicted to show greater sensitivity loss (Fig. 5B, GI, green interval), but one must be judicious with the application of a stimulus that is too small, as these are associated with increased variability.…”

“…21,[44][45][46] The age difference between individual subjects and the cohorts may therefore increase the variability within the dataset and confound the comparison of structure-function relationship between the normal and glaucomatous cohort. Hence, to minimize the variability imposed by intra-and intercohort age differences, the GCL thickness and DLS of all normal and glaucomatous subjects were age-corrected to the average age of the glaucomatous cohort using previously established regression analysis models as conducted in previous studies, 11,21,[24][25][26]31,32,45,47 including the commonly used SITAstandard algorithm of the HFA. 48 Specifically, for the GCL thickness, measurements from each normal and glaucomatous subjects were clustered into eight statistically separable classes and adjusted to match the average age of the glaucomatous cohort using a previously published conversion for all but the foveal area.…”

“…S2D). The age correction for visual field data was established for 30-2 test pattern 45 ; therefore, correction factors were calculated for the 10-2 test locations using a distance-wise weighted averaging method from the three or four closest 30-2 stimulus locations as described elsewhere. 25 Further, subanalysis of the normal cohort was conducted to determine the efficacy of the age correction as detailed in the supplementary material.…”