Discovering irregular pupil light responses to chromatic stimuli using waveform shapes of pupillograms

Abstract

BackgroundThe waveforms of the pupillary light reflex (PLR) can be analyzed in a diagnostic test that allows for differentiation between disorders affecting photoreceptors and disorders affecting retinal ganglion cells, using various signal processing techniques. This procedure has been used on both healthy subjects and patients with age-related macular degeneration (AMD), as a simple diagnostic procedure is required for diagnosis.ResultsThe Fourier descriptor technique is used to extract the features of PLR waveform shapes of pupillograms and their amplitudes. To detect those patients affected by AMD using the extracted features, multidimensional scaling (MDS) and clustering techniques were used to emphasize stimuli and subject differences. The detection performance of AMD using the features and the MDS technique shows only a qualitative tendency, however. To evaluate the detection performance quantitatively, a set of combined features was created to evaluate characteristics of the PLR waveform shapes in detail. Classification performance was compared across three categories (AMD patients, aged, and healthy subjects) using the Random Forest method, and weighted values were optimized using variations of the classification error rates. The results show that the error rates for healthy pupils and AMD-affected pupils were low when the value of the coefficient for a combination of PLR amplitudes and features of waveforms was optimized as 1.5. However, the error rates for patients with age-affected eyes was not low.ConclusionsA classification procedure for AMD patients has been developed using the features of PLR waveform shapes and their amplitudes. The results show that the error rates for healthy PLRs and AMD PLRs were low when the Random Forest method was used to produce the classification. The classification of pupils of patients with age-affected eyes should be carefully considered in order to produce optimum results.Electronic supplementary materialThe online version of this article (doi:10.1186/s13637-014-0018-x) contains supplementary material, which is available to authorized users.

Analysis for Extracted Features of Pupil Light Reflex to Chromatic Stimuli in Alzheimer’s Patients

“…By using these differences in PLR behaviour, PLRs in response to chromatic stimuli have been observed in patients with retinal diseases such as Pigmentosa or Glaucoma [7,10,11]. Also, this phenomenon was used with AMD patients, and a diagnostic procedure has also been discussed [8]. The patients do not recognise the influence of AMD when the diseased area appears at the periphery of the retina.…”

“…Therefore, the differences in the two types of PLRs may suggest a retinal condition as the possible reason for the size of the damaged area caused by AMD. To examined the differences, several features of waveform shapes of PLRs in response to red and blue light stimuli were compared using discrimination analysis [8].…”

“…Some of the magnitudes of the coefficients in the early orders of the series, a(k) and b(k), and the DC component (a 0 ) were employed to form feature vectors of the waveform shapes [8]. The magnitudes of the coefficients, including a 0 , FD i (i = 0, .…”

“…In addition to this, the recent discovery of intrinsically photosensitive retinal ganglion cells (ipRGCs) [3,4] reveals the possibility of using various new procedures to diagnose diseases related to retinal conditions by using a shorter light wavelength, such as blue light [5][6][7]. For example, PLRs related to ipRGCs can be used to detect symptoms of Age-Related Macular Degeneration (AMD) [8]. Also, the phenomenon has been used to diagnostic procedures for diseases [9][10][11].…”

Image and Non-Image Forming Melanopsin Function in Age-Related Macular Degeneration

“…In AMD, the PLR has been used as a measure of outer retinal function (Asakawa, Ishikawa, Ichibe & Shimizu 2014;Brozou et al 2009;Nakayama, Nowak, Ishikawa, Asakawa & Ichibe 2014;Rosli et al 2012;Sabeti et al 2013;Sabeti et al 2011) and demonstrates a longer latency to constriction and reduction in maximum pupil constriction amplitude. However, these studies were not designed to measure ipRGC function in AMD.…”