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Subretinal membranes are associated with abnormal degrees of pupil “evasion”: an index of clinical macular dysfunction
  1. F H Zaidi1,2,
  2. F D Bremner3,
  3. K Gregory-Evans1,2,
  4. K D Cocker1,4,
  5. M J Moseley1,4
  1. 1Department of Ophthalmology and Visual Neuroscience, Imperial College London, UK
  2. 2The Western Eye Hospital, St Mary’s NHS Trust, London, UK
  3. 3The National Hospital for Neurology and Neurosurgery, London, and University College London Hospitals, London, UK
  4. 4Department of Optometry and Visual Science, City University, London, UK
  1. Correspondence to: Farhan H Zaidi Department of Ophthalmology, King’s College Hospital, London, UK; fhz12{at}hotmail.com

Abstract

Aim: To assess whether macular dysfunction caused by unilateral subretinal neovascular membranes (SRNs) is associated with pupil “evasion” (that is, increased initial rate of re-dilation following a brief light stimulus).

Methods: Comparative observational series. 20 eyes of 10 participants, all with unilateral SRNs and healthy fellow eyes. Dynamic infrared pupillography at seven stimulus intensities (duration 1100 ms, intensities over 2 log unit range). Pupil evasion ratio (PEVR; defined as the ratio of light response amplitude to amount of recovery at the mid-time point of re-dilation expressed as a percentage) was calculated for each stimulus intensity (mean of five recordings).

Results: Inter-eye PEVR is significantly reduced in eyes with SRN (that is, greater pupil evasion in SRN eyes: range p  =  0.002 to p  =  0.05 (paired t test)) and is most apparent at higher stimulus intensities.

Conclusions: PEVR is a novel parameter that is analogous to the pupil escape ratio, but measured following a short rather than a sustained light stimulus. PEVR is significantly altered by macular disease. Clinically PEVR may be used to detect occult unilateral or asymmetric maculopathy in situations such as ocular media opacities like cataract, when pupil reactions are unaffected or augmented, while other tests of retinal function are diminished. PEVR represents altered neuronal firing in cones and macular ganglion cells.

  • ARM, age related maculopathy
  • FFA, fundus fluorescein angiography
  • MDA, mid-dilation amplitude
  • PEVR, pupil evasion ratio
  • PDT, photodynamic therapy
  • RA, reflex amplitude
  • RAPD, relative afferent pupillary defect
  • SRNs, subretinal neovascular membranes
  • pupil evasion
  • pupil escape
  • pupil index
  • subretinal membrane
  • neovascular membrane
  • ARM, age related maculopathy
  • FFA, fundus fluorescein angiography
  • MDA, mid-dilation amplitude
  • PEVR, pupil evasion ratio
  • PDT, photodynamic therapy
  • RA, reflex amplitude
  • RAPD, relative afferent pupillary defect
  • SRNs, subretinal neovascular membranes
  • pupil evasion
  • pupil escape
  • pupil index
  • subretinal membrane
  • neovascular membrane

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Footnotes

  • Competing interests: none.

  • Local regional ethics committee approval was obtained for this study (St Mary’s NHS Trust, London).

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