|Year : 2012 | Volume
| Issue : 3 | Page : 311-314
Visual outcome following optic neuritis: A 5-year review
CN Pedro-Egbe, B Fiebai, CS Ejimadu
Ophthalmology Unit, Department of Surgery, College of Health Sciences, University of Port Harcourt, Nigeria
|Date of Acceptance||10-Oct-2011|
|Date of Web Publication||6-Sep-2012|
C N Pedro-Egbe
Ophthalmology Unit, Department of Surgery, College of Health Sciences, University of Port Harcourt
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Optic neuritis is a demyelinating inflammatory disease of the optic nerve that typically affects young adults especially females, and is usually associated with multiple sclerosis especially in Caucasians. The prognosis for visual recovery is usually good but with poor quality.
Objective: The objective was to determine the level of improvement of vision after an attack of optic neuritis in Port Harcourt, Nigeria.
Design: A retrospective hospital-based study was performed.
Setting: Eye Clinic, University of Port Harcourt Teaching Hospital (UPTH), Port Harcourt, Nigeria.
Data Extraction: Medical records of all cases of optic neuritis seen at the Eye Clinic of UPTH over a 5-year period (January 2006-December 2010) were retrieved and relevant data including age, sex, presenting symptom, and visual acuity (VA) were extracted. The VA at discharge 12 weeks later was noted. Our diagnosis of optic neuritis was based on the presence of low vision, dyschromatopsia, and peri-ocular pain.
Results: Over 24,000 patients were seen during this period, and 27 cases were optic neuritis (0.1%). Of the 27 cases of optic neuritis, 20 cases were retro-bulbar neuritis (74.1%), while seven (25.9%) were papillitis. There were 16 females and 11 males giving a female to male ratio of 3:2. Most cases (75%) at presentation had VAs<6/24. By the 12 th week, most visual acuities (77.1%) had improved to 6/12 or better.
Conclusion: This study confirms widely documented evidence that there is improvement in visual acuity after an attack of optic neuritis. Even though the risk of developing multiple sclerosis following optic neuritis is said to be low in blacks, these patients should still be followed up for sometime especially as some may go on to develop other complications of demyelination.
Keywords: Optic neuritis, Port Harcourt, visual outcome
|How to cite this article:|
Pedro-Egbe C N, Fiebai B, Ejimadu C S. Visual outcome following optic neuritis: A 5-year review. Niger J Clin Pract 2012;15:311-4
| Introduction|| |
Optic neuritis (ON) is a demyelinating inflammatory disease of the optic nerve that typically affects young adults especially females.  Many cases of optic neuritis are associated with multiple sclerosis or neuromyelitis optica or can occur in isolation.  The association between optic neuritis and multiple sclerosis is well established.  Bilateral optic neuritis has been reported in a Nigerian patient with neuromyelitis optica (Devic's disease).  Occasionally, ON can result from infectious processes involving the paranasal sinuses  or occur in the course of a systemic viral infection. ,
A diagnosis of optic neuritis is most often based on accepted clinical criteria which include loss of vision, dyschromatopsia, and peri-ocular pain.  Other diagnostic criteria for optic neuritis may also include reduced perception of light intensity, Uhthoff's phenomenon (visual deficit induced by exercise or increased body temperature),  and Pulfrich phenomenon (visual stereo-illusion observed when a swinging pendulum bob is viewed through a neutral density filter in front of one eye). The initial attack of optic neuritis is unilateral in 70% of adult patients and bilateral in 30%; and mean age of onset is in the third decade of life  with an annual incidence that ranges from 1.6 to 5.0 new cases per 100,000 population. [8,9]
The cause and treatment of optic neuritis are unclear, but prognosis for visual recovery is generally good  even though return of visual function is almost never complete. , After resolution of optic neuritis, almost all patients show some signs of optic nerve damage and even when a patient's acuity recovers to 20/20, abnormalities frequently remain in other measures such as contrast sensitivity, color vision, and visual field. ,, Visual loss may be subtle or profound and may occur over hours (rarely) to days (most commonly). The nadir is usually about 1 week after the onset. 
The magnitude of the risk of multiple sclerosis after optic neuritis is uncertain. Previous studies have reported very disparate results, with the risk being reported to be as low as 19% 5 years after MS  and others up to 50% 15 years later. 
Optic neuritis can sometimes result from an infectious process involving the orbit, paranasal sinuses or systemic viral disease. ,,, It is second only to glaucoma as the most common acquired optic nerve disorder in persons younger than age 50.  Though the diagnosis of optic neuritis is usually made on clinical grounds, in atypical cases, magnetic resonance imaging (MRI) is used to further characterize and exclude other disease processes. Magnetic resonance imaging is well established as the single most important predictor of risk of developing optic neuritis (Optic Neuritis Treatment Trial).  The imaging of the brain in optic neuritis is said to be more important than that of the optic nerves as this is the most valuable predictor for the development of subsequent multiple sclerosis in the presence of white-matter abnormalities. 
In the Optic Neuritis Treatment Trial (ONTT), the 5-year risk of developing multiple sclerosis was 16% in patients with normal brain MRI findings, 37% with 1-2 lesions, and 51% with 3 or more lesions. At 10 years, the only statistically significant difference was between no lesions (22% risk) and one or more lesions (56% risk).  Prior to the Optic Neuritis Treatment Trial, there were no well-established guidelines for treating optic neuritis as some experts advocated treatment with oral prednisone while others recommended no treatment. Although corticosteroids had been used to treat this disease, various studies have not demonstrated their effectiveness. ,,,,
The objective of the study was to determine the level of improvement of vision after an attack of optic neuritis in Port Harcourt, Nigeria.
| Materials and Methods|| |
Medical records of all cases of optic neuritis seen at the Eye Clinic of the University of Port Harcourt Teaching Hospital over a 5-year period (January 2006 to December 2010) were retrieved and relevant data including age, sex, presenting symptom, presenting visual acuity (Snellen chart), and visual acuity at discharge 12 weeks later were extracted.
Our diagnosis of optic neuritis was based on accepted clinical criteria only and these included loss of vision, dyschromatopsia (Ishihara pseudoisochromatic plates), and peri-ocular pain in addition to a sluggish pupil or a relative afferent pupillary defect (RAPD). Contrast sensitivity was assessed with the Pelli-Robson chart. For retrobulbar neuritis a normal optic nerve head appearance was necessary for diagnosis while for papillits, the presence of disc swelling was needed for diagnosis. None of our patients had any systemic involvement suggestive of multiple sclerosis or neuromyelitis optica. All the patients received oral prednisolone (1 mg/kg body weight) for 2 weeks. Exclusion criteria included case files with incomplete records (two), those lost to follow-up (four) and other causes of optic neuropathy such as glaucoma or trauma. Diabetics were also excluded. Data were analyzed using Epi-info Version 6.02 and P values less than 0.05 were considered significant.
| Results|| |
A total of 27 cases of optic neuritis were seen over a 5-year period out of a total patient population of 24,363. (This gives the proportion of optic neuritis as 0.1%.) There were 11 males (40.7%) and 16 females (59.3%) giving a male to female ratio of 2:3. Over 60% of the subjects were aged between 20 and 49 years old [Table 1]. The mean age of those with optic neuritis was 26.7 ± 12.1. There were 20 cases of retro-bulbar neuritis (74.1%) and seven cases of papillitis (25.9%).
[Table 2] shows the age and gender distribution of those with retro-bulbar neuritis. A total of 20 cases of retro-bulbar neuritis were seen. There were 8 males (40%) and 12 (60%) females giving a male to female ratio of 2:3. The mean age of those with retro-bulbar neuritis was 25.8 ± 11.1.
|Table 2: Age and gender distribution of patients with retro-bulbar neuritis|
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[Table 3] shows the age and gender distribution of those with papillitis. A total of seven cases of papillitis were seen. There were three males (42.9%) and four females (57.1%) giving a male to female ratio of 3:4. The mean age of those with papillitis was 29.1 ± 15.3. There was a statistically significant difference between the mean age of those with retro-bulbar neuritis and papilltis (Chi square-12.52; P value - 0.00)
Nineteen patients had unilateral involvement (70.4%), while 8 (29.6%) subjects had bilateral involvement; making the total, 35 eyes of 27 patients [Table 4]. Over 75% of the cases at presentation had VAs<6/24; only 5 eyes (14.3%) had VAs better than 6/24 [Table 4]. Over 85% of those with bilateral disease were less than 25 years old and there was a slight female preponderance (M:F=1:1.3).
[Table 5] shows that by the 12 th week, most visual acuities (77.1%) had improved to 6/12 or better. In 18 eyes (52.4%) visual acuity was 6/6-6/9. There were no patients whose visual acuities remained at CF-NPL.
| Discussion|| |
In most parts of the world acute demyelinating optic neuritis (ON) is the most common cause of unilateral painful visual loss in young adults.  In this study, about 60% of those with optic neuritis were aged between 20 and 49 years, similar to other studies where young adults were found to be mainly affected by the disease.  Those with papillitis were however slightly older than those with retro-bulbar neuritis and this was statistically significant (Chi square 12.52; P value 0.00). Over 70% of our patients had unilateral ocular involvement similar to Shams et al.  In our study, even though females were found to be more affected than males by the disease, the figure is still slightly lower than reports by other researchers. ,,,, The reason for this may not be unconnected with the fact that, in our environment, females are less likely to present themselves for treatment than males because of cultural barriers and widespread illiteracy. This therefore gives a false impression that females are not that much affected compared to other studies. In our study, retro-bulbar neuritis was responsible for about 75% of all cases of optic neuritis similar to the result of the Optic Neuritis Treatment Trial Study.
In regions of the world where multiple sclerosis (MS) is common, most cases of ON are related to multiple sclerosis.  In our study, however, all the cases of optic neuritis occurred in isolation. This is not surprising as the incidence of multiple sclerosis associated optic neuritis (MSAON) is said to be very rare in blacks  and highest in Caucasians. 
At 12 weeks postpresentation, almost 80% of visual acuities had improved to 6/12 or better. This agrees with the widely documented evidence that visual acuity improves after an attack of optic neuritis. ,
About 50% of our patients however had some degree of reduction in quality of vision as assessed by color vision and contrast sensitivity. Since our patients were not followed up for a long time and none had magnetic resonance imaging (MRI), it is difficult to know if some were at risk of developing MS or if some could have gone on to develop multiple sclerosis. This relationship between optic neuritis and MS needs further elucidation in a homogenous black population such as ours.
| Conclusion|| |
This study has confirmed widely documented evidence that there is improvement in visual acuity after an attack of optic neuritis. It also lends credence to the known fact that optic neuritis is rare in blacks.  Even though the risk of developing MS following optic neuritis is said to be low in blacks, these patients should still be monitored for sometime especially as some may go on to develop other complications of demyelination. To fully substantiate some of these findings however, a prospective study on optic neuritis using the ONTT guideline and a larger sample size is proposed for future studies.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]
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