Glaucomatous retinal nerve fiber layer loss is associated with slower reaction times under a divided attention task.

Abstract

 

Purpose

 

The ability to divide attention or “multi-task” is essential to everyday activities such as driving. This study evaluated the relationship between glaucomatous structural damage and ability to divide attention during simulated driving.

 

Methods

 

A cross-sectional study of 159 subjects from the Diagnostic Innovations in Glaucoma Study including 38 healthy subjects, 57 with suspect glaucoma and 64 with glaucoma. The ability to divide attention was investigated by measuring reaction times (RTs) to peripheral stimuli presented while subjects concomitantly performed a central driving task (car following or curve negotiation). Peripheral stimuli were presented at 3 contrasts (low, medium and high). Subjects also underwent standard automated perimetry and retinal nerve fiber layer (RNFL) assessment using optical coherence tomography. Self-reported 5-year history of motor vehicle crash (MVC) was recorded and cognitive ability assessed using the Montreal Cognitive Assessment (MOCA).

 

Results

 

The mean RTs to the low contrast stimulus were 1.06s and 0.56s in glaucomatous and healthy subjects respectively during the curve negotiation divided attention (CNDA) task (P <0.001), and 1.18s and 0.67s (P <0.001) during the car following divided attention (CFDA) task. RTs were positively skewed therefore base-10 logarithms were calculated. There was a significant, albeit nonlinear relationship between RTs and better eye RNFL thickness (ρ = -0.352; P <0.001 for CNDA and ρ = -0.313; P <0.001 for CFDA RTs). RNFL thickness was a significant predictor of RTs even after adjusting for age, better eye mean deviation, MOCA and central driving task performance (Figure 1). Longer RTs were associated with a history of recent MVC. A 1-unit increase in log10 RT was associated with a 9.0 to 12.4-fold increased odds of MVC for CNDA and CFDA tasks respectively after adjusting for potential confounding variables including average miles driven per week.

 

Conclusions

 

Glaucoma patients had longer RTs compared to healthy individuals. RNFL thickness was predictive of RTs independently of conventional perimetric measures and after adjustment for confounding variables. RNFL thickness may be a useful biomarker for predicting ability to perform activities of daily living.

 

 

Figure 1. Predicted log10 RTs for curve negotiation divided attention (DA) driving simulator task.

 

Keywords: 669 quality of life • 610 nerve fiber layer • 414 aging: visual performance