Friday, 30 May 2014

Recovering from Optic Neuritis

Malik MT, Healy BC, Benson LA, Kivisakk P, Musallam A, Weiner HL, Chitnis T. Factors associated with recovery from acute optic neuritis in patients with multiple sclerosis.Neurology. 2014 May. pii: 10.1212/WNL.0000000000000524. [Epub ahead of print]

OBJECTIVE: To identify clinical and demographic features associated with the severity and recovery from acute optic neuritis (AON) episodes in patients with multiple sclerosis (MS).
METHODS: Adult (n = 253) and paediatric (n = 38) patients whose first symptom was AON were identified from our MS database. Severity measured by loss of visual acuity (mild attack ≤20/40, moderate attack 20/50-20/190, and severe attack ≥20/200) and recovery in visual acuity at 1 year after the attack (complete recovery ≤20/20, fair recovery 20/40, and poor recovery ≥20/50) were recorded. Demographic and clinical features associated with attack severity and recovery were identified using proportional odds logistic regression. For another group of patients, blood samples were available within 6 months of an AON attack. In this group, the impact of vitamin D level on the severity/recovery was also assessed.
RESULTS: Men (adjusted odds ratio [OR] = 2.28, p = 0.03) and subjects with severe attacks (adjusted OR = 5.24, p < 0.001) had worse recovery. AON severity was similar between the pediatric and adult subjects, but recovery was significantly better in pediatric subjects in the unadjusted analysis (p = 0.041) and the analysis adjusted for sex (p = 0.029). Season-adjusted vitamin D level was significantly associated with attack severity (OR for 10-U increase in vitamin D level = 0.47; 95% confidence interval: 0.32, 0.68; p < 0.001). Vitamin D level was not associated with recovery from the attack (p = 0.98) in univariate analysis or after accounting for attack severity (p = 0.10).
CONCLUSION: Vitamin D levels affect AON severity, whereas younger age, attack severity, and male sex affect AON recovery. Underlying mechanisms and potential therapeutic targets may identify new measures to mitigate disability accrual in MS.
Normal visual acuity is commonly referred to as 20/20 vision, the metric equivalent of which is 6/6 vision. At 20 feet or 6 meters, a human eye with nominal performance is able to separate contours that are approximately 1.75mm apart. A vision of 20/40 corresponds to lower than nominal performance, a vision of 20/10 to better performance.

In the expression 20/x vision, the numerator (20) is the distance in feet between the subject and the chart, and the denominator (x) is the distance at which a person with 20/20 acuity would just discern the same optotype. Thus, 20/20 means "normal" vision and 20/40 means that a person with 20/20 vision would discern the same optotype from 40 feet away. This is equivalent to saying that with 20/40 vision, the person possesses half the resolution and needs twice the size to discern the optotype.
Acuity is a measure of visual performance and is unrelated to the eyeglass prescription required to correct vision. Instead, an eye exam seeks to find the prescription that will provide the best corrected visual performance achievable. The resulting acuity may be greater or less than 20/20 = 1.0. Indeed, a subject diagnosed as having 20/20 vision will often actually have higher visual acuity because, once this standard is attained, the subject is considered to have normal (in the sense of undisturbed) vision and smaller optotypes are not tested.

This study looks at factors which may predict better outcomes after optic neuritis and is a guide only, but having your vitamin D levels up may protected you before not after the event, so remeber to keep them topped up.

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