Contrast Sensitivity Is Impaired in Suspected Primary Open-Angle Glaucoma Patients

Abstract

Purpose: To assess spatial contrast sensitivity (CS) in suspected primary open-angle glaucoma (POAG) patients.

Methods: CS was measured using sinusoidal gratings of 4 cycles/degree. First, foveal and peripheral CS were assessed in 34 suspected POAG patients and compared with 71 and 28 age-matched healthy individuals for foveal and peripheral conditions, respectively. Second, foveal CS was assessed in 34 early POAG patients age-matched with suspected POAG patients. Analyses were performed considering two age ranges: Under and Over 50 y.o. Correlations were evaluated between CS and clinical parameters. Diagnostic accuracy was also analyzed.

Results: Peripheral CS was lower in older suspected POAG patients (23.4 ± 16.1) than the control group (39.1 ± 28.2) (p = 0.040). Foveal CS was reduced in suspected POAG participants (Under 50: 146.8 ± 63.3; p = 0.004. Over 50: 110.5 ± 65.0; p = 0.044) and in early POAG patients (Under 50: 141.2 ± 72.6; p = 0.002. Over 50: 80.2 ± 54.5 p < 0.001), both compared to the control group (Under 50: 213.5 ± 66.2. Over 50: 138.6 ± 71.7). CS was lower in early POAG than in POAG suspected in older patients (p = 0.042). Foveal CS was correlated with age (Early: p = 0.001. Suspect: p = 0.002) and with the cup-disc ratio only in early POAG patients (p < 0.001). Foveal CS had fair (AUC = 0.74) diagnostic accuracy for early POAG patients.

Conclusions: CS in suspected POAG patients is lower than in healthy individuals. Our findings evidence the spatial vision loss before the onset of POAG.

Keywords: age; contrast sensitivity; early detection; functional assessment; glaucoma.

Figure 1

Box plot of peripheral contrast sensitivity in suspected primary open-angle glaucoma (POAG) patients and control participants for those under 50 years old (left panel) and over 50 years old (right panel). Blue dots are the individual’s values and red marks are the mean values of each group. Differences between groups are indicated as (*) for p < 0.05.

Figure 2

Box plot of foveal contrast sensitivity in suspected primary open-angle glaucoma (POAG) patients and control participants for those under 50 years old (left panel) and over 50 years old (right panel). Blue dots are the individual’s values and red marks are the mean values of each group. Differences between groups are indicated as (*) for p < 0.05, (**) for p < 0.01.

Figure 3

Box plot of foveal contrast sensitivity in early primary open-angle glaucoma (POAG) and suspected POAG patients under 50 years old (left panel) and over 50 years old (right panel). Blue dots are the individual’s values and red marks are the mean values of each group. The mean foveal control group value is shown by the dashed line. Differences between groups are indicated as (*) for p < 0.05.

Figure 4

Foveal contrast sensitivity versus age of the participants. Circular dots represent the individual’s values. Solid lines represent the linear model for each group. POAG: primary open-angle glaucoma. The blue color represents the early POAG group (slope = −2.21, intercept = 213.45; r = −0.45; p = 0.001). The red color represents the suspected POAG group (slope = −1.9, intercept = 220.17; r = −0.37; p = 0.002). The black color represents the control group (slope = −2.91, intercept = 314; r = −0.53; p < 0.001). Control data was obtained from the study of Santillán and colleagues [30].

Figure 5

Foveal contrast sensitivity versus cup-to-disc ratio (CDR) in early primary open-angle glaucoma (POAG) (left panel) and suspected POAG patients (right panel). Circular blue dots represent the individual’s values. Solid black lines represent the linear model for each group (Early POAG group: p-value < 0.001. Suspected POAG group: p-value = 0.766).

Figure 6

Receiver characteristic operating (ROC) curves for foveal contrast sensitivity. POAG: primary open-angle glaucoma; AUC: area under the curve; Upper panel: suspected POAG patients; Lower panel: early POAG patients; (Left panel): Under 50 years old groups; (Right panel): Over 50 years old groups. The dotted black lines represent the diagonals with AUC = 0.5 (no discrimination). The red dots represent the pair sensitivity and 100-specificity for the cut-off values. p: significance level.