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Quantitative assessment of optic nerve head morphology and retinal nerve fibre layer in non-arteritic anterior ischaemic optic neuropathy with optical coherence tomography and confocal scanning laser ophthalmoloscopy
  1. C K M Chan1,2,
  2. A C O Cheng1,2,
  3. C K S Leung1,
  4. C Y L Cheung1,
  5. A Y Yung1,
  6. B Gong1,
  7. D S C Lam1,2
  1. 1
    Department of Ophthalmology & Visual Sciences, Chinese University of Hong Kong, Hong Kong
  2. 2
    Hong Kong Eye Hospital, Kowloon, Hong Kong
  1. Dr C K M Chan, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong; kmcc2001{at}hotmail.com

Abstract

Background/aims: To compare the optic disc parameters between patients with non-arteritic anterior ischaemic optic neuropathy (NAION) and normal controls, using optical coherence tomography (OCT) and Heidelberg Retinal Tomograph III (HRT), and to evaluate the structure–function relationship in NAION eyes.

Methods: Both eyes of 22 patients with typical unilateral NAION of ⩾6 months’ duration and 52 eyes from 52 randomly selected normal subjects underwent Humphrey visual field (HVF) examination and measurement of optic disc and retinal nerve fibre layer thickness (RNFLT).

Results: For the NAION-affected eyes, NAION fellow eyes and normal controls, the ocular magnification-corrected OCT disc areas were respectively 1.849 (SD 0.343) mm2, 1.809 (0.285) mm2 and 1.964 (0.386) mm2; the cup areas were 0.246 (0.187) mm2, 0.172 (0.180) mm2 and 0.469 (0.332) mm2. On HRT, the disc areas were 2.11 (0.38) mm2, 2.06 (0.40) mm2 and 2.16 (0.42) mm2; and the cup areas were 0.28 (0.34) mm2, 0.25 (0.18) mm2 and 0.48 (0.32) mm2. On both OCT and HRT, the cup areas and cup–disc area ratios (CDAR) of both eyes of NAION patients were significantly smaller than controls (p⩽0.01), but the disc areas were not (p⩾0.21). There was a significant correlation between HVF mean deviation and OCT RNFLT (r = 0.44, p = 0.04) but not with HRT RNFLT (p = 0.30) in NAION-affected eyes.

Conclusion: NAION patients have smaller optic cups and CDARs in both eyes compared with controls. A larger sample size is necessary to demonstrate if disc size affects the risk of developing NAION. The NAION-affected eyes’ OCT RNFLT correlated with HVF mean deviation but the HRT RNFLT did not.

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Footnotes

  • Competing interests: None.

  • Ethics approval: Ethics approval was provided by the Research Ethics Committee (Kowloon Central/Kowloon East) in Hong Kong.

  • Patient consent: Obtained.

  • See Editorial, p 703

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