A comparison between the visual field and color vision of normal eyes and eyes of MS patients with unilateral optic neuritis

Abstract

Introduction: Multiple Sclerosis (MS) is an inflammatory disease in which myelin sheaths of nerve cells in some parts of the brain and/or spinal cord are damaged. The damages cause some disorders in the ability of different parts of the nerve systems which are responsible for communication, and cause a lot of symptoms. The most common symptoms of the disease are autonomic nervous system, visual, motor and sensory problems. The most common damage to the optic nerve is optic neuritis, or inflammation of optic nerve which leads to disorders in color vision, visual field and a reduction in the thickness of the nerve axons, and it will be cured in 90% of patients after about 6 weeks, and it rarely becomes chronic. This study aimed to evaluate the residual impairment in the performance after the acute phase of disease. Methods and materials: In this study, 30 MS patients including 24 women and 6 men with an average age of 39 years old having a history of unilateral optic neuritis (at least one year before) were studied in ALZAHRA (PBUH) OPHTHALMOLOGY CENTER OF ZAHEDAN. Acuity, visual field and color vision in these patients were measured; OCT test was conducted for them. Finally, statistical analysis of data was conducted using SPSS software version 19 using the independent t test. Findings: a comparison between visual field of eyes showed that even after at least one year, the most prevalent disorder in visual field of both eyes was central scotoma which had prevalence equal to 46.7% in normal eyes and 43.3% in affected eyes. There was a significant difference between vision impairment of both eyes regarding the visual field (0.001) which was more prevalent in the upper half of the visual field (10%). In OCT test after at least one year from the attack of optic neuritis, although a decrease in thickness of visual axons in both eyes was observed with an average of 54 axons, there was no significant difference between the two eyes (0.758). In color vision test, the highest prevalence of color vision deficiency in normal eyes was Deuteranopia (the absence of green photoreceptors) which was 36.7%, while the prevalence for affected eyes with absence of red and green photoreceptors (Protanopia - Deuteranopia) was 33.3%. However, there were no significant differences between two eyes (0.635). In this study, a direct relationship was observed between the intensity of color vision deficiency and reduction of axons thickness. Conclusion: There is a permanent deficiency in visual field of MS patients, even after the acute phase of the disease, and it is statistically considerable. In the OCT test, a reduction in the thickness of nerve axons can be observed; although there is no statistically significant difference between the two eyes. Since there is a direct relationship between the reduction of axons thickness and color vision, one can observe that the patients will face some problems regarding the color vision as well as making decision for their future jobs or even in their daily activities.