Novel Ultrafast Visual Field Testing with The Toronto Portable Perimeter (TPP)

Authors: Runjie B. Shi¹, Moshe Eizenman², Michael Balas³, Gareth Leung⁴, Yan Li⁵, Myrna Lichter², Steve Arshinoff², Willy Wong⁵. ¹Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada, ²Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada, ³Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada, ⁴Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada, ⁵Edward S. Rogers Sr. Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, Canada.

Author Disclosures: R.B. Shi: None. M. Eizenman: None. M. Balas: None. G. Leung: None. Y. Li: None. M. Lichter: None. S. Arshinoff: Membership on advisory boards or speakers’ bureaus; Name of for-profit or not-for-profit organization(s); Alcon Laboratories Inc., Cima Life Science, Zeiss, Rayner, Arctic Dx.. Membership on advisory boards or speakers’ bureaus; Description of relationship(s); C. W. Wong: None.


Abstract Body: 

Purpose: Approximately half of all Canadian glaucoma patients already have moderate-to-severe visual field defects at initial diagnosis. A more accessible visual field test that enables earlier detection of visual field loss could be useful to intervene vision loss in these patients earlier. Current standard automated perimeters are difficult to use in community screening programs as they are non-portable, expensive, require technical support and the tests are relatively long. In this study we evaluate a new TPP-Ultrafast test that was integrated into the Toronto Portable Perimeter (TPP), a head-mounted virtual-reality perimeter. 

Study Design: Prospective study. 

Methods: Algorithms based on the Sequentially Optimized Reconstruction Strategy (SORS) to estimate contrast sensitivity thresholds were trained to match the expected characteristics of visual fields in the general population. SORS is a data-driven algorithm that continuously predicts visual field thresholds during the test to achieve significant speed-up over traditional approaches. Unlike supra-threshold tests, the TPP-Ultrafast test estimates "true" thresholds (in dB) and outputs all standard field indices. Glaucoma patients with stable visual fields were recruited from the York Finch Eye Institute in Toronto. Each patient performed an HFA SITA-Fast and a TPP-Ultrafast 24-2 test. Fields with at least one cluster of three neighboring locations with pattern deviation p<5%, were considered a "detection." Each eye’s last two SITA-Fast tests were analyzed and compared against the TPP-Ultrafast results. The more reliable of the two SITA-Fast tests was used as "reference" to establish the status of the visual field ("detection" or "no detection") while the other SITA-Fast test was used as "retest" to establish test-retest diagnostic performance of the HFA. 

Results: N=33 eyes from 18 patients (age: 72±8 years (mean±sd), Mean Deviation (MD): -4.4±6.9 dB) were tested. In 11 "no detection" eyes on the SITA-Fast reference field, the TPP-Ultrafast test achieved specificity of 91% (10/11) versus 64% (7/11) for the SITA-Fast retest. In eight eyes with moderate-to-severe field defect (MD worse than -6 dB), TPP-Ultrafast and SITA-Fast both achieved 100% sensitivity. In 14 eyes with mild field defect (MD better than -6 dB), TPP-Ultrafast achieved 50% (7/14) sensitivity versus 86% (12/14) on the HFA. TPP-Ultrafast tests were on average 55% shorter in moderate-to-severe fields (mean: 131 vs 292 seconds, Wilcoxon p=0.008) and 57% shorter in mild and healthy fields (mean: 95 vs 196 seconds, Wilcoxon p<0.001). 

Conclusions: The TPP-Ultrafast test has very good specificity and can reliably detect moderate-to-severe visual field loss in half the time of a SITA-Fast test. However, its sensitivity to detect mild defects could be improved by adding more examples of mild defects to the training dataset. The portability and ease of use of the TPP system makes the TPP-Ultrafast test a promising tool for visual field testing in the community.

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