Abstract
Purpose :
The Pediatric Eye Disease Investigator Group (PEDIG) has developed and used the Electronic Visual Acuity Tester (EVA) HOTV protocols for assessing visual acuity in verbal children. Stimuli are generated on a lap-top as single, flanked, H, O, T or V optotypes, controlled by a staircase. The current research assesses potential improvements in EVA HOTV using: 1. additional smaller optotypes; 2. new ways to calculate acuity from the data.
Methods :
Right eyes of 20 young adults (7M&13F;19 to 29 years) were tested under 3 blur conditions: Plano, +0.50DS and +1.00DS. Three different testing protocols were used: 1. HOTV Short, the current standard EVA HOTV protocol which does not test optotype sizes lower than -0.1 logMAR (6/4.8, 20/16); 2. HOTV Long, a modified EVA HOTV protocol which could test as low as -0.4 logMAR (6/2.4, 20/8); and 3. Sloan, a logMAR chart using the same laptop, with Sloan letter optotypes sized from 0.4 to -0.4 logMAR. For each testing protocol, acuity was calculated (Scoring methods) in 3 ways: 1. Line-by-line scoring (the current EVA HOTV method); 2. Letter-by-letter scoring; and 3. Probit Analysis, fitting a fixed shape probit function the frequency of seeing data.
Results :
If acuity (Figure 1) was calculated using Line-by-line, or Letter-by letter scoring, HOTV Short, HOTV Long and Sloan protocols gave different acuity thresholds and different shaped Acuity v Blur functions (significant Blur X Test Protocol interaction, p<=0.046; Blur effects, p<0.001; Test Protocol,p<=0.005). In particular HOTV Short protocol does not present below logMAR -0.1. These Test Protocol differences were not apparent if acuity was scored by probit analysis, which resulted in almost identical thresholds for HOTV Short, HOTV Long and Sloan (Blur X Test Protocol interaction, p=0.61; Test Protocol p=0.62; Blur effect, p<0.001).
Conclusions :
Because it does not present sufficiently small optotypes, the current EVA HOTV testing protocol will not be able to measure acuity to threshold in most adults who have their best spectacle correction, and, based on a review of previous studies, this is also likely to be the case in older pre-school children. This can be overcome by adding smaller sized optotypes. Estimating HOTV EVA acuity thresholds by probit analysis is easy, because the protocol is run by computer, and gives a good match with Sloan logMAR acuities.
This is a 2020 ARVO Annual Meeting abstract.