Abstract
Purpose :
This study aims to compare contrast discrimination, global motion and global form perception between primary open-angle glaucoma (POAG) and primary angle closure glaucoma (PACG)
Methods :
Contrast discrimination thresholds were assessed using a task described by Porkorny & Smith (1997). The steady pedestal task measures contrast discrimination of the magnocellular pathway whereas the pulsed pedestal task measures the parvocellular pathway (Pokorny & Smith, 1997). Global motion perception was assessed using random dot kinematograms (motion coherence thresholds) and global form perception using glass pattern coherence thresholds. A total of 45 people aged 50 to 77 years (15 POAG: 51-77 years, mean=63.73±6.96; 15 PACG: 58-75 years, mean=66.66±4.7; 15 controls: 51-77 years, mean=59.8±8.1) participated. The severity between the POAG and PACG groups was approximately matched. People were selected with similar spatial patterns of visual field defects and one quadrant free from damage. HFA mean deviation was: POAG -2.34 to -16.85dB, mean=-6.88±4.87; PACG -1.37 to -16.42dB, mean=-6.3±4.22). Threshold estimates were determined centrally and at a single mid-peripheral location (12.5o) in a quadrant free from visual field defects. Control participants were tested in matching quadrants to those of the people with glaucoma.
Results :
Two-Way ANOVA revealed significant differences in thresholds between the groups for all tasks with glaucoma groups having higher thresholds than controls (Figure: 1, main effect of group p<0.01). Post hoc testing showed no significant difference between PACG and controls for global motion perception. There was no significant (p>0.05) difference in thresholds between POAG and PACG for either of the contrast discrimination task. However, the POAG group had higher thresholds (p<0.05) than PACG for both global motion and form perception tasks.
Conclusions :
The POAG group performed worse than the PACG group for tasks requiring higher cortical processing, compared to tasks processed earlier in the visual pathways. Our findings suggest that POAG has more generalised neurodegeneration beyond the eye, whereas PACG may have more localised effects on the eye.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.