Mesopic Functional Visual Acuity in Normal Subjects

Abstract

To evaluate mesopic functional visual acuity (FVA) with a newly developed system in normal subjects and to compare the results with photopic FVA, sixty-eight healthy volunteers (24.03 ± 4.42 [mean ± standard deviation] years) were enrolled in this study. A commercially available FVA measurement system (AS-28; Kowa, Aichi, Japan) was modified to measure FVA under mesopic conditions as well as photopic conditions. Measurements were performed monocularly in photopic conditions during 60 seconds. After dark adaptation for 15 minutes, the same measurements were repeated in mesopic conditions. Outcomes included starting visual acuity (VA), FVA (the average of VAs), visual maintenance ratio (VMR), maximum VA, minimum VA, and numbers of blinks during the 60-second measurement session, and were compared between mesopic and photopic conditions. Starting VA was –0.11 ± 0.08 and 0.39 ± 0.12 logarithm of the minimum angle of resolution (logMAR) in photopic and mesopic conditions, respectively. FVA was –0.06 ± 0.09 and 0.52 ± 0.14 logMAR, VMR was 0.98 ± 0.02 and 0.94 ± 0.04, maximum VA was –0.15 ± 0.06 and 0.33 ± 0.12 logMAR, the minimum VA was 0.05 ± 0.12 and 0.78 ± 0.20 logMAR, and the number of blinks was 8.23 ± 7.54 and 7.23 ± 6.20, respectively. All these parameters except the number of blinks were significantly different between the two conditions (P < 0.001). Besides, the difference between maximum and minimum VAs and standard deviation of VA were significantly larger in mesopic than in photopic conditions (P < 0.001). This study revealed that not only overall visual function decline but also instability of vision under mesopic conditions even in healthy subjects.

Effects of absolute luminance and luminance contrast on visual discrimination in low mesopic environments

“…While some researchers use a conservative adaptation period of 30 minutes (Yoshimoto, Okajima, & Takeuchi, 2016), others measuring mesopic sensitivity as a qualifying measure reveal that only 5 minutes are sufficient to allow dark adaptation (Perez, Puell, Sanchez, & Langa, 2003;Hertenstein, Bach, Gross, & Beisse, 2016). The participants in this study completed approximately 20 minutes of dark adaptation, which should be sufficient for our study parameters (Eloholma, Ketomäki, Orreveteläinen, & Halonen, 2006;Hiraoka, Hoshi, Okamoto, Okamoto, & Oshika, 2015;Koefoed, Baste, Roumes, & Hovding, 2015).…”

Nighttime Driving in Older Adults: Effects of Glare and Association With Mesopic Visual Function

“…42 Participants were given a 10-minute adaptation period to the mesopic light level based on previous study adaptation periods. 35,38,40,42,52 Visual Acuity and Contrast Sensitivity. Mesopic HCVA and Pelli-Robson CS were measured with the same method as the photopic assessments, using an alternative chart to avoid familiarity with the test letters.…”

“…31 A clinical examination of vision typically involves assessment of high contrast visual acuity (HCVA) under photopic light levels, which does not fully capture the visual capacity required for safe driving, 32,33 or for other lighting conditions such as the low luminance and glare conditions typically present when driving at night. [34][35][36][37] Numerous studies have demonstrated the advantages and advocated the use of Copyright 2017 The Authors iovs.arvojournals.org j ISSN: 1552-5783 nonstandard vision tests to represent visual function across a range of lighting conditions. 2,34,[38][39][40][41][42][43][44] While there is some evidence that driver safety and performance at night is associated with mesopic visual function and glare sensitivity, such as the Mesotest (mesopic CS in the presence and absence of glare) 45,46 and mesopic visual acuity (VA), 32 there has been very limited research into nighttime driving ability and the assessment of visual capacity to drive at night.…”

Older drivers' self‐reported vision‐related night‐driving difficulties and night‐driving performance

“…; Hiraoka et al. ). While measures of contrast sensitivity (Wood & Owens ), mesopic visual acuity (VA) (Kimlin et al.…”