Evaluation of Visual Cortex Activity using Functional Near-Infrared Spectroscopy (fNIRS) in Primary Open Angle and Primary Angle Closure Glaucoma: A pilot study

Hage Angku; Rohit Verma; Karthikeyan Mahalingam; Anand Naik; Dewang Angmo; Shikha Gupta; Ramanjit Sihota; Tanuj Dada

doi:10.1097/IJG.0000000000002427

Evaluation of Visual Cortex Activity using Functional Near-Infrared Spectroscopy (fNIRS) in Primary Open Angle and Primary Angle Closure Glaucoma: A pilot study

J Glaucoma. 2024 May 16. doi: 10.1097/IJG.0000000000002427. Online ahead of print.

Authors

Hage Angku¹, Rohit Verma², Karthikeyan Mahalingam¹, Anand Naik¹, Dewang Angmo¹, Shikha Gupta¹, Ramanjit Sihota¹, Tanuj Dada¹

Affiliations

¹ Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
² Department of Psychiatry, All India Institute of Medical Sciences, New Delhi, India.

PMID: 38747728
DOI: 10.1097/IJG.0000000000002427

Abstract

Precis: Functional Near Infrared Spectroscopy was used to assess visual cortical activity in patients with primary open angle and primary angle closure glaucoma. There was decreased activity in the visual cortex of glaucoma patients correlating with the severity of glaucoma.

Purpose: To evaluate visual cortex activity using fNIRS (Functional Near Infrared Spectroscopy) in primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG) compared to healthy controls.

Methods: A total of 30 POAG, 31 PACG, and 30 healthy aged-matched controls from a single centre were recruited in this cross-sectional observational pilot study with purposive sampling. The POAG and PACG groups were age-matched but were not matched for disease severity at recruitment. All participants underwent fNIRS testing using a multi-channel continuous-wave near infra-red system NIRSport 8×7 device (NIRx Medizintechnik GmbH, Berlin, Germany). The visual cortex activity was evaluated in terms of maximum amplitude of change in oxyhemoglobin (OxyHb) concentration over 10 seconds and a comparison was done between three groups. Both POAG and PACG groups were combined (termed as glaucoma group) to assess relationship of visual cortical activity with disease severity {by visual field defect (mean deviation) and retinal nerve fiber layer (RNFL) thickness}.

Results: All participants showed the characteristic response of increased OxyHb and decreased DeoxyHb during stimulus presentation. The maximum amplitude of change in OxyHb concentration over 10 seconds was significantly lower in both POAG and PACG groups compared to control in the right and left middle occipital gyri (P<0.05). There was no significant difference between PACG and POAG. Importantly, there was a negative correlation of the visual cortex activity with the visual field defects (mean deviation) (P<0.05) and a positive correlation with RNFL thickness in the glaucoma group (P<0.05).

Conclusion: In glaucoma patients, reduction in visual cortical activity was observed which may be indicative of neuronal degeneration occurring in the occipital cortex. Disease severity in glaucoma appears to be closely correlated with visual cortex activity. fNIRS can serve as a useful neuroimaging modality for assessing the hemodynamic and neurodegenerative changes in glaucoma.