The Effect of Cataract on Early Stage Glaucoma Detection Using Spatial and Temporal Contrast Sensitivity Tests

RESEARCH ARTICLE The Effect of Cataract on Early Stage Glaucoma Detection Using Spatial and Temporal Contrast Sensitivity Tests Johann Klein1, Barbara K. Pierscionek2*, Jan Lauritzen2, Karin Derntl3, Andrzej Grzybowski4,5, Margarita B. Zlatkova1 1 School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, BT521SA, United Kingdom, 2 Faculty of Science, Engineering and Computing, Kingston University, Penrhyn Road,Kingstonupon-Thames, KT1 2EE, United Kingdom, 3 Ordination Dr. Karin Derntl, Ophthalmologist, Wartenburgerstr. 1b, 4840 Vöcklabruck, Austria, 4 Department of Ophthalmology, Poznań City Hospital, Poznań, Poland, 5 Department of Ophthalmology, University of Warmia and Mazury, Olsztyn, Poland * Abstract Background OPEN ACCESS Citation: Klein J, Pierscionek BK, Lauritzen J, Derntl K, Grzybowski A, Zlatkova MB (2015) The Effect of Cataract on Early Stage Glaucoma Detection Using Spatial and Temporal Contrast Sensitivity Tests. PLoS ONE 10(6): e0128681. doi:10.1371/journal. pone.0128681 Academic Editor: Maurice Ptito, University of Montreal, CANADA To investigate the effect of cataract on the ability of spatial and temporal contrast sensitivity tests used to detect early glaucoma. Methods Twenty-seven glaucoma subjects with early cataract (mean age 60 ±10.2 years) which constituted the test group were recruited together with twenty-seven controls (cataract only) matched for age and cataract type from a primary eye care setting. Contrast sensitivity to flickering gratings at 20 Hz and stationary gratings with and without glare, were measured for 0.5, 1.5 and 3 cycles per degree (cpd) in central vision. Perimetry and structural measurements with the Heidelberg Retinal Tomograph (HRT) were also performed. Received: January 16, 2015 Accepted: April 29, 2015 Results Published: June 8, 2015 Data Availability Statement: All relevant data are within the paper and its Supporting Information files. After considering the effect of cataract, contrast sensitivity to stationary gratings was reduced in the test group compared with controls with a statistically significant mean difference of 0.2 log units independent of spatial frequency. The flicker test showed a significant difference between test and control group at 1.5 and 3 cpd (p = 0.019 and p = 0.011 respectively). The percentage of glaucoma patients who could not see the temporal modulation was much higher compared with their cataract only counterparts. A significant correlation was found between the reduction of contrast sensitivity caused by glare and the Glaucoma Probability Score (GPS) as measured with the HRT (p<0.005). Funding: The authors have no support or funding to report. Conclusions Competing Interests: The authors have declared that no competing interests exist. These findings indicate that both spatial and temporal contrast sensitivity tests are suitable for distinguishing between vision loss as a consequence of glaucoma and vision loss Copyright: © 2015 Klein et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. PLOS ONE | DOI:10.1371/journal.pone.0128681 June 8, 2015 1 / 17 Contrast Sensitivity Tests for Glaucoma Diagnosis caused by cataract only. The correlation between glare factor and GPS suggests that there may be an increase in intraocular stray light in glaucoma. Introduction The pernicious nature of glaucoma and sight loss that this disease can cause renders early diagnosis vital. Visual field losses caused by glaucoma can occur with no signs or symptoms. Yet pathogenesis of the disease is not fully understood [1]. The ability to detect contrast has relevance to the progression of glaucoma and is measured using contrast sensitivity tests that assess the extent to which this ability has been lost. Since contrast sensitivity testing for sinusoidal grating patterns was introduced as a research tool [2,3], studies have shown that grating contrast sensitivity has the potential to detect early glaucoma [4–8], is a better predictor of visual function than visual acuity [9,10], discriminates between glaucoma and/or other ocular disease and normal subjects [11–13] and thus has the potential to be an efficient screening tool for detecting glaucoma at its early stages [12,14,15]. There is also substantial evidence to indicate that ability to detect flickering targets which measures temporal contrast sensitivity may be significantly reduced before visual field defects can be detected or before changes in the optic nerve become apparent [7, 16–19]. Although standard automatic perimetry (SAP) which is used to assess visual fields remains the main psychophysical test used for measuring visual field loss in glaucoma, it does not consider the anatomical arrangement of nerve fibres [20,21,22] and has a high degree of non-stationary test-retest variability which is dependent on the sensitivity and on the type of analysis used (ie a Full Threshold strategy or the Swedish Interactive Threshold Algorithm (SITA)) [22]. Tests of temporal contrast sensitivity i.e. flicker perimetry have been used in a battery of tests for glaucoma [6,19,23–24] and inspired the development of the frequency doubling technology (FDT) perimeter [25]. Temporal contrast sensitivity is considered more resistant to the effects of lens opacities [26–28]. Yet, it has been suggested recently that the high temporal frequency stimuli in FDT render this more susceptible to reduced retinal illumination when light is attenuated in opacified or older lenses [29]. In this study the ability of spatial and temporal contrast sensitivity tests to detect early glaucoma in the presence of cataract was investigated using a control group matched for cataract type and severity. Contrast sensitivity for spatiotemporal stimuli, were investigated to find what combination of parameters may allow detection of glaucoma in the presence of cataract. Methods Subjects Subjects were recruited from a clinical practice in Upper Austria. Twenty-seven subjects with early glaucoma who presented with low grade or no glaucomatous field losses with simultaneous early cataractous signs were selected together with twenty-seven control subjects matched for age and cataract type and severity (S1 and S2 Tables). The mean ages of the test and control groups were 60 ± 10.2 (SD) years (ranging from 37 to 74 years, 17 females, 10 males) and 59.03 ± 9.0 years (ranging from 38 to 73 years, 14 females, 13 males) respectively. The age distribution of the test and control cohorts is shown in Fig 1. PLOS ONE | DOI:10.1371/journal.pone.0128681 June 8, 2015 2 / 17 Contrast Sensitivity Tests for Glaucoma Diagnosis PLOS ONE | DOI:10.1371/journal.pone.0128681 June 8, 2015 3 / 17 Contrast Sensitivity Tests for Glaucoma Diagnosis Fig 1. Frequency histogram of age distributio (...truncated)