City Research Online

Abstract

Objective: The visual field (VF) may be predicted from retinal nerve fibre layer thickness (RNFLT) using a Bayesian Radial Basis Function (BRBF). This study aimed to evaluate a new methodology to quantify and visualise discordance between structural and functional measurements in glaucomatous eyes.

Methods: Five GDxVCC RNFLT scans and 5 Humphrey SITA VF tests were obtained from 50 glaucomatous eyes from 50 patients. A best available estimate of the ‘true’ VF was calculated as the point-wise median of these 5 replications. This ‘true’ VF was compared with every single RNFLT-predicted VF from BRBF and every single measured VF. Predictability of VFs from RNFLT was established from previous data. A structure-function pattern discordance map (PDM) and structure-function discordance index (SFDI; values 0 to 1) were established from the predictability limits for each structure-function measurement pair to quantify and visualise the discordance between the structure-predicted and measured VFs.

Results: Mean absolute difference (MAD) between the structure-predicted and ‘true’ VFs was 3.9dB. MAD between single and ‘true’ VFs was 2.6dB. Mean of SFDI was 0.34 (SD 0.11). 39% of the structure-predicted VFs showed significant discordance (SFDI>0.3) from measured VFs.

Conclusions: BRBF, on average, predicts the ‘true’ VF from RNFLT slightly less well than a measured VF from the 5 VFs compromising the ‘true’ VF. The PDM highlights locations with structure-function discordance, with the SFDI providing a summary index. These tools may help clinicians trust the mutually confirmatory structure-function measurements with good concordance, or identify unreliable ones with poor concordance.

Publication Type:	Article
Subjects:	R Medicine > RE Ophthalmology
Departments:	School of Health & Psychological Sciences > Optometry & Visual Sciences
SWORD Depositor:	Symplectic Administrator

Export

Downloads