Measuring visual and quality of life outcomes in nystagmus: a scoping review.

INTRODUCTION

Pathological nystagmus of all aetiologies can cause visual disability and reduced quality of life. Recent research has characterised the dynamic nature of the condition and questioned the validity of widely used outcome measures, such as visual acuity (VA), as an accurate measure of visual function in nystagmus. VA only describes the spatial resolving capacity of the visual system for high contrast stimuli, whereas good visual function requires numerous components including contrast sensitivity, colour vision, depth perception and oculomotor functions. For these reasons, the literature on nystagmus, particularly interventional studies, has been inconsistent with regard to the outcome measures used.

METHODS

We performed a scoping literature review to characterise all published measures and instruments for determining functional vision and quality of life in patients with nystagmus.

RESULTS

A total of 235 articles were included in the study, accounting for 5880 patients with nystagmus. Articles spanned six continents and eight decades of research. We identified 10 grouped outcome measures including VA (27 outcomes, 84 instruments), nystagmus features (33 outcomes, 4 instruments), visual function (11 outcomes, 30 instruments), ocular morphology (3 outcomes, 5 instruments), orthoptic and ocular alignment features (20 outcomes, 63 instruments), reading assessment (8 outcomes, 6 instruments), visual search assessment (4 outcomes, 4 instruments), foveation/function models (8 outcomes), patient-reported outcomes (30 outcomes) and non-ocular features (6 outcomes).

CONCLUSION

We have confirmed that there is significant heterogeneity in visual function and quality of life outcome measures in the nystagmus literature. It is evident that one or few measures are insufficient to measure all the relevant outcomes from interventional nystagmus studies. Therefore, we propose a Delphi project using our data to determine a standardised core outcome set for interventional nystagmus studies.