Objective: To evaluate the peripapillary RNFL thickness and optic nerve functions in fellow eye of NMO with unilateral optic neuritis.

Materials and Methods: A comparative cross-sectional study was conducted in 2 tertiary hospitals from August 2017 to May 2019. RNFL thickness and optic nerve functions were evaluated. Statistical analysis was performed using Statistical Package for Social Science version 24.

Results: A total of 26 NMO patients and 26 controls were involved in this study. The median age (IQR) of NMO patients was 32.5 (12) years old. The RNFL thickness was significantly reduced in NMO patients with non-ON eyes as compared to control group. Best corrected visual acuity between the 2 groups were comparable (0.20 vs 0.00, p=0.071). Contrast sensitivity was also reduced in NMO patients (non-ON eyes) at all 5 spatial frequencies. In NMO group, 34.6% have normal colour vision. The mean deviation (MD) of Humphrey visual field (HVF) was higher in NMO group (p<0.001). There was a moderate correlation between RNFL thickness and contrast sensitivity. Weak correlation was found between the RNFL thickness with visual acuity and mean deviation of visual field test.

CLINICAL CASE: A 56-year-old Chinese woman, an active smoker, presented with a hearing deficit, persistent tinnitus and nasal congestion. Examination and investigations revealed the presence of a mass in the nasopharynx. Tissue biopsy revealed nasopharyngeal carcinoma. However, the Epstein-Barr virus was not tested. She was counseled for chemotherapy, but refused and was subsequently lost to follow up. She presented one year later with right eye ptosis associated with progressive worsening of diplopia and blurring of vision. Examination revealed multiple (second, third, fourth and sixth) cranial nerve involvement. Systemic examination and investigations revealed cervical lymphadenopathy and liver metastasis. Repeated imaging showed that the mass had invaded the base of the skull, cavernous sinus and orbital apices. Pulse dosing of corticosteroid therapy was commenced, resulting in dramatic improvement of vision.

METHODS: The present study is a comparative cross-sectional, hospital-based study. A total number of 64 PD patients and 64 controls were recruited. Candidates that fulfilled the criteria with normal ocular examinations were undergone optical coherent tomography (OCT) examinations of the right eye. RNFL and macular thickness were evaluated.

RESULTS: There was a statistically significant reduction in RNFL thickness in average (adjusted mean 84.32 vs 95.93, p ≤ 0.001), superior (adjusted mean 105.15 vs 118.13, p ≤ 0.010), and inferior (adjusted mean 104.95 vs 126.55, p ≤ 0.001) PD group compared to the control group. The macula thickness also was significantly reduced in average (adjusted mean 266.51 vs 281.34, p = 0.015), central (adjusted mean 236.37 vs 255.55, p = 0.001), outer superior (adjusted mean 269.16 vs 278.19, p = 0.014), outer inferior (adjusted mean 256.34 vs 272.24, p ≤ 0.001), and outer nasal (adjusted mean 287.64 vs 302.84, p = 0.001) PD group compared to the control group. There was a significant positive correlation between RNFL thickness and visual acuity among PD patients in the inferior segment with p = 0.020 and nasal segment with p ≤ 0.001. There was also a significant positive correlation between macular thickness and visual acuity among PD patients in the inner temporal segment with p = 0.006, outer superior segment with p = 0.003, and outer temporal segment with p ≤ 0.001.

FINDINGS: In Case 1, a 36-year-old Malay lady presented to our clinic with acute onset of blurring of vision in her left eye that she experienced since past 1 month. She was diagnosed with syringomyelia 12 years ago and was on conservative management. Her visual acuity was 6/6 in the right eye and counting fingers at 1 m in the left. There was a positive relative afferent pupillary defect in her left eye. Optic nerve functions of her left eye were reduced. Visual field showed a left inferior field defect. Her extraocular muscle movements were full. Magnetic resonance imaging of the brain and spine showed syringomyelia at the level of C2-C6 and T2-T9. Both of her optic nerves were normal. Her condition improved with intravenous and oral corticosteroids. In Case 2, a 44-year-old Malay lady presented to our clinic with a progressive central scotoma in her right eye that she experienced since past 1 month. She had previous history of recurrent episodes of weakness in both of her lower limbs from past 8 months. Visual acuity in her right and left eye was 6/9 and 6/6, respectively. The relative afferent pupillary defect in her right eye was positive. Optic nerve functions of her right eye were affected. Visual field showed a central scotoma in her right eye. Her extraocular muscle movements were full. Fundoscopy of her right eye showed a pale optic disc. Her left eye fundus was normal. Magnetic resonance imaging of the brain and spine showed syringomyelia at T3-T6. Both of her optic nerves were normal. A diagnosis of syringomyelia with right optic atrophy was performed. Her condition improved with intravenous and oral corticosteroids.