Zainab Faisal², Edrich Silva², Angelina Joseph², Nancy O. Mahfouz², Sophia Castro¹, Ayesha Mulla², Simrat Renu², Robert G. Alexander²; ¹CUNY School of Medicine, ²Department of Psychology & Counseling, New York Institute of Technology, USA

Fixational eye movements (microsaccades, drifts, and tremors) are essential for everyday visual function. Clinical disorders result in detectable abnormalities in eye movement patterns, though these impairments are often not consciously perceived by the patient. This review examines the research on disease-related fixational instability across ophthalmological and neurological conditions. Methods: We conducted a literature review of peer-reviewed articles examining fixational eye movements in both neurologic and ophthalmological diseases. Articles were selected through extensive keyword searches and searches of references cited in retrieved publications. Studies reporting quantitative measures of microsaccades, drift, tremor, or fixation stability were included. Results: Findings across the literature review indicate that ophthalmic and neurological diseases produce measurable disruptions in fixational control. Ophthalmic conditions such as Behçet uveitis, cataracts, amblyopia, macular disease, and glaucoma each show specific changes in fixational behavior, including increased drift, altered microsaccade timing, or wider fixation areas. Some conditions also differ based on disease progression, such as the reduced stability seen in Stargardt disease compared with Best vitelliform macular dystrophy. Neurological disorders show similar disruptions. For example, increased square-wave jerks have been observed in Amyotrophic Lateral Sclerosis, and difficulties maintaining stable fixation have been reported after mild Traumatic Brain Injury. Conclusion: Fixational instability is a useful way to understand how ophthalmic and neurological diseases affect visual function. Measuring changes in microsaccades, drift, and fixation stability can help identify functional problems that are not always visible through standard tests. Continued research may support the use of these measures in clinical settings to better track disease and evaluate treatment.

Acknowledgements: This work was supported by the National Institute of Health (Award R16GM159810 to RGA), which provided support for student training that contributed to this project. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.