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Quantification of retinal nerve fiber layer thickness reduction associated with a relative afferent pupillary defect in asymmetric glaucoma
  1. Yasuko Tatsumi,
  2. Makoto Nakamura,
  3. Miyuki Fujioka,
  4. Yoriko Nakanishi,
  5. Azusa Kusuhara,
  6. Hidetaka Maeda,
  7. Akira Negi
  1. Department of Organs Therapeutics, Division of Ophthalmology, Kobe University Graduate School of Medicine, Kobe, Japan
  1. Correspondence to: Makoto Nakamura Department of Organs Therapeutics, Division of Ophthalmology, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan; manakamu{at}med.kobe-u.ac.jp

Abstract

Aim: The relative afferent pupillary defect (RAPD) is an important clinical sign of asymmetrical retinal ganglion cell and axonal damage. Although glaucoma essentially affects bilateral eyes, a subset of patients manifests asymmetrical glaucomatous optic neuropathy (GON), which exhibits an RPAD in the more advanced eyes. However, the degree to which axonal loss occurs before an RAPD is clinically detectable has not been substantiated. The purpose of this study is to assess the relationship between the depth of a clinically detectable RAPD and the reduction ratio of retinal nerve fiber layer (RNFL) thickness in the more advanced eyes relative to that in the contralateral less advanced eyes of patients with asymmetrical GON.

Methods: Enrolled were 29 consecutive glaucoma patients with the clinically detectable RAPD. An RAPD was quantified by placing log-scaled neutral density filters over the less advanced eyes while performing the swinging flashlight test. Average RNFL thickness was determined using the Fast RNFL thickness programme of optical coherence tomography 3000. Correlation coefficient and Linear regression analyses were used in assessing the relationship between the RAPD and the ratio of RNFL thickness in the more advanced eyes relative to that in the less advanced.

Results: RAPD ranged from 0.6 to 2.4 log units. The log-scaled RAPD had a statistically significantly inversed correlation with the average RNFL thickness ratio (rs = −0.729, p<0.0001). Linear regression analysis found an equation that the average RNFL thickness ratio in the more affected eyes relative to that in the less advanced (%)  = (0.827−0.169×RAPD (log units))×100 (R2 = 0.557, p<0.0001).

Conclusions: When an RAPD is clinically detected, the RNFL thickness in the more advanced eyes was in average reduced to about 73% of that in the less advanced.

  • GON, glaucomatous optic neuropathy
  • OCT, optical coherence tomography
  • RAPD, relative afferent pupillary defect
  • RNFL, retinal nerve fiber layer
  • relative afferent pupillary defect
  • retinal nerve fiber layer thickness
  • optical coherence tomography
  • asymmetric glaucoma
  • GON, glaucomatous optic neuropathy
  • OCT, optical coherence tomography
  • RAPD, relative afferent pupillary defect
  • RNFL, retinal nerve fiber layer
  • relative afferent pupillary defect
  • retinal nerve fiber layer thickness
  • optical coherence tomography
  • asymmetric glaucoma

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Footnotes

  • Published Online First 18 October 2006

  • Funding: This study was supported in part by Grant-in-Aid No. 16390499 (AN, MN) and No. 17591835 (MN) from the Ministry of Education, Culture, Sports, Science and Technology of the Japanese Government, and by Suda Memorial Foundation for Glaucoma Research (MN). MN is a recipient of the 12th ROHTO Award.

  • Competing interests: None.

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