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Abstract
Primary open-angle glaucoma (POAG) firstly mainly affects peripheral vision. Current behavioral studies support the idea that visual defects of patients with POAG extend into parts of the central visual field classified as normal by static automated perimetry analysis. This is particularly true for visual tasks involving processes of a higher level than mere detection. The purpose of this study was to assess visual abilities of POAG patients in central vision. Patients were assigned to two groups following a visual field examination (Humphrey 24–2 SITA-Standard test). Patients with both peripheral and central defects and patients with peripheral but no central defect, as well as age-matched controls, participated in the experiment. All participants had to perform two visual tasks where low-contrast stimuli were presented in the central 6° of the visual field. A categorization task of scene images and human face images assessed high-level visual recognition abilities. In contrast, a detection task using the same stimuli assessed low-level visual function. The difference in performance between detection and categorization revealed the cost of high-level visual processing. Compared to controls, patients with a central visual defect showed a deficit in both detection and categorization of all low-contrast images. This is consistent with the abnormal retinal sensitivity as assessed by perimetry. However, the deficit was greater for categorization than detection. Patients without a central defect showed similar performances to the controls concerning the detection and categorization of faces. However, while the detection of scene images was well-maintained, these patients showed a deficit in their categorization. This suggests that the simple loss of peripheral vision could be detrimental to scene recognition, even when the information is displayed in central vision. This study revealed subtle defects in the central visual field of POAG patients that cannot be predicted by static automated perimetry assessment using Humphrey 24–2 SITA-Standard test.
Highlights
Primary open-angle glaucoma (POAG) is an ocular disease characterized by a progressive destruction of retinal ganglion cells and the optic nerve
Considering only controls and central defect (CD) patients as groups, the Task interacted with the Group suggesting that the difference between sensitivity for the Categorization task and for the Detection task was larger for CD patients than for controls (CD patients: 1.44 ± 0.73; controls: 0.93 ± 0.60; F(1,44) = 15.73, p < 0.001)
For the Categorization task, mean comparisons showed that CD patients as well as no central defect (NoCD) patients had a lower sensitivity than controls (CD: 1.70 ± 0.82; NoCD: 2.71 ± 0.93; controls: 3.35 ± 0.69; CD vs. controls: F(1,44) = 33.94, p < 0.001; NoCD vs. controls: F(1,44) = 5.00, p < 0.05)
Summary
Primary open-angle glaucoma (POAG) is an ocular disease characterized by a progressive destruction of retinal ganglion cells and the optic nerve. This results in progressive vision loss affecting mainly peripheral vision [1]. The visual field defect is mostly assessed by static automated perimetry This is based on luminance increment detection of small dots and allows evaluation of retinal sensitivity. POAG patients often report discomfort in their daily life, even at stages when static automated perimetry only indicates a slight peripheral vision loss [4]. Retinal sensitivity loss may impact more complex aspects of visual processing in POAG patients, even early in the disease. Specific eye movement patterns have been observed during reading [10], face recognition [11], exploration of scenes [12,13,14], visual search of objects [15]
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