Comparison of Arteritis and Nonarteritic Anterior Ischemic Optic Neuropathies with the Heidelberg Retina Tomograph
Received 4 November 2004; accepted 21 December 2004. published online 09 May 2005.
Objective
Quantitative data are not available regarding the morphological appearance of optic nerve morphology after arteritic anterior ischemic optic neuropathy (AAION) and nonarteritic anterior ischemic optic neuropathy (NAION). The purpose of this study is to evaluate the appearance of the optic nerve head in patients after AAION and NAION with the Heidelberg Retina Tomograph (HRT).
Design
Prospective comparative observational study.
Participants
Thirty-eight patients with either unilateral AAION (15) or NAION (23).
Methods
Heidelberg Retina Tomograph images were taken of both affected and unaffected eyes. The quantitative changes in the optic nerve head were morphologically evaluated and compared with those of the normal contralateral eyes.
Main outcome measures
Heidelberg Retina Tomograph parameters were analyzed using the uninvolved contralateral eye as a control.
Results
The ratio between cup area and disc area was 42% larger in the affected eyes in the NAION group than in the fellow eyes (P = 0.03, t test). In the AAION patients, the ratio between cup area and disc area was 116% larger in involved eyes than in their fellow eyes (P = 0.0003, t test). In addition, in the AAION group, relative to their fellow eyes, the rim area was 27% smaller (P = 0.0006), cup volume was 160% larger (P = 0.021, t test), mean cup depth was 29% larger, cup shape measure differed by 41% (suggesting more excavation), and mean retinal nerve fiber layer thickness was 30% less. Relative to the fellow eyes in the NAION group, the rim area was 6% smaller (P = 0.13, Student’s t test), and the cup shape measure was 13% different, although these were not statistically significant. When the uninvolved eyes of the NAION and AAION groups were compared directly, there was no statistical difference between any of the HRT parameters, except mean cup depth (0.09 vs. 0.14 mm, respectively; P = 0.02).
Conclusions
This study is the first to demonstrate quantitatively an enlargement and excavation of the optic cup after an event of AAION, but not NAION. The eyes affected with AAION showed significant excavation and enlargement of the optic cup when compared with contralateral uninvolved eyes. All HRT-generated parameters showed changes consistent with increased enlargement and excavation of AAION-involved eyes. These changes were not observed in eyes that experienced an event of NAION.
1Department of Ophthalmology, University of Auckland, Auckland, New Zealand.
2Neuro-ophthalmology Service, Wills Eye Hospital, Thomas Jefferson Medical School, Philadelphia, Pennsylvania.
3Glaucoma Service, Wills Eye Hospital, Thomas Jefferson Medical School, Philadelphia, Pennsylvania.
4Department of Medicine, University of Auckland, Auckland, New Zealand.
Reprint requests to Department of Ophthalmology, University of Auckland, Private Bag 92019, Auckland, New Zealand.
ABSTRACT