Early impairment of magnocellular visual pathways mediated by isolated-check visual evoked potentials in primary open-angle glaucoma: a cross-sectional study.

OBJECTIVE: To explore different performances in the magnocellular (MC) and parvocellular (PC) visual pathways in patients with primary open-angle glaucoma (POAG) and to objectively assess impairment in early stage of POAG. METHODS AND ANALYSIS: This is a cross-sectional study. MC and PC visual pathways were assessed using isolated-check visual evoked potential (ic-VEP). Visual acuity, intraocular pressure, fundus examination, optical coherence tomography and visual field were measured. Signal-to-noise ratios (SNRs), mediated by ic-VEP were recorded. The Spearman's correlation analysis was used to estimate the relationships between visual functions and structures. Receiver-operating-characteristic (ROC) curves were used to estimate the accuracy in detection of early POAG. RESULTS: 60 participants (30 early POAG eyes and 30 age-matched control subjects) were recruited. MC visual pathway showed a non-linear response function, while PC visual pathway was a linear response function as contrast increased. Early POAG eyes exhibited significantly weaker initial contrast gains and lower maximum responses in the MC visual pathway (p=0.001, p=0.004, respectively). The SNRs at 8% and 32% depths of modulation (DOM) were significantly correlated with temporal-side retinal nerve fibre layer (RNFL) thickness in early POAG in MC-biased stimulation (p=0.017, p=0.020, respectively). The areas under ROC of 16% DOM were 0.780 (sensitivity 80.0%, specificity 63.3%) with the cut-off SNR of 2.07. CONCLUSIONS: The MC visual pathway was damaged in the early stage of POAG. The SNRs at 8% and 32% DOM of MC-biased stimulation were significantly correlated with temporal-side RNFL thickness in early POAG, which helped in understanding the mechanisms of visual impairment in the early stage of POAG.

Intraocular pressure and diurnal fluctuation of open-angle glaucoma and ocular hypertension: a baseline report from the LiGHT China trial cohort.

AIMS: To report the baseline intraocular pressure (IOP) characteristics and its diurnal fluctuation in the Laser in Glaucoma and Ocular Hypertension China cohort. METHODS: 622 primary open-angle glaucoma (POAG) patients and 149 ocular hypertension (OHT) patients were recruited at Zhongshan Ophthalmic Center from 2015 to 2019. Standardised ocular examinations were performed including IOP measurement using the Goldmann applanation tonometer. Daytime phasing IOP was recorded at 8:00, 10:00, 11:30, 14:30, 17:00 hour. RESULTS: The mean baseline IOP was 20.2 mm Hg for POAG patients and 24.4 mm Hg for OHT. Multiple regression analysis revealed that thicker central corneal thickness (CCT) was correlated with higher IOP in both POAG and OHT. Male gender and younger age were correlated with higher IOP only for POAG. As for diurnal IOP fluctuation, mean IOP fluctuation was 3.4 mm Hg in POAG eyes and 4.4 mm Hg in OHT. The peak and trough IOP occurred at 8:00 and 14:30 hour in both POAG and OHT eyes. CONCLUSIONS: Younger age, male gender and thicker CCT are correlated to higher IOP in POAG patients while only thicker CCT is related to higher IOP in OHT patients. Peak IOP appears mostly at early morning or late afternoon and trough value occurs mostly at early afternoon.