Mesopic visual acuity is less crowded
| Autor: | John Siderov, František Pluháček |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Adult
Male Visual acuity Adolescent genetic structures Mesopic vision Mesopic Vision Visual Acuity Luminance Contrast Sensitivity Young Adult 03 medical and health sciences Cellular and Molecular Neuroscience 0302 clinical medicine LogMAR chart Reference Values medicine Humans Mathematics Monocular Color Vision Vision Tests Repeatability Crowding Sensory Systems eye diseases Ophthalmology 030221 ophthalmology & optometry Optometry Female medicine.symptom Photic Stimulation 030217 neurology & neurosurgery Photopic vision |
| ISSN: | 1435-702X |
| Popis: | Purpose: The decrease in visual acuity under low luminance conditions is well known. Recent laboratory evidence showed that crowding under low luminance (mesopic) light levels is less robust than under photopic conditions. The present study examines whether such differences in crowding influence clinical measurements of mesopic visual acuity, including test-retest repeatability. Methods: Twenty adult subjects with normal or corrected to normal visual acuity were recruited for the study. Monocular visual acuity was measured under photopic (228 cd/m2) and mesopic (0.164 cd/m2) luminance conditions using a letter chart, similar in principle to the ETDRS logMAR chart, presented on a computer monitor. Three rows of 5 letters, each row differing in size by 0.05 logMAR from largest to smallest were displayed at the center of the monitor. The level of crowding was varied by varying the separation between horizontally adjacent letters from 100% optotype size to 50%, 20% and 10% optotype size. Inter-row spacing was proportional to optotype size. Observers read the letters on the middle row only. Measurements continued by reducing the size of the letters, until 3 or more errors on the middle row were made. Each correctly identified letter contributed 0.01 to the recorded logMAR score. All measurements were repeated for each subject on two separate days. Results: Visual acuity (logMAR) was significantly better under photopic than mesopic luminance conditions with a mean difference of 0.48 logMAR. Visual acuity also decreased with decreasing letter separation (i.e. increase in crowding). However, the decrease in visual acuity for the smallest letter separation was less under the mesopic luminance condition, even after accounting for the increased size of threshold acuity letters. Test-retest repeatability for mesopic and photopic conditions was not significantly different. Conclusions: Crowding under mesopic luminance conditions has less impact on visual acuity than under photopic luminance. |
| Databáze: | OpenAIRE |
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