- •Simultaneous measurement of contact lens dewetting behavior and visual performance is possible.
- •After 13.1 s ± 17,4 s, 20.83 s ± 21,81 s, 34.67 s ± 29,11 s participants lost one, two or three log units of visual acuity.
- •Visual loss of one log unit occurred 5 s after first dewetting.
- •Visual loss due to dewetting of pre lens tear film was unaffected by amount of daily wearing time (5 min vs 8 h).
- •Visual performance was reduced without any dewetted are within the pupil zone in more than 50 % of all cases.
To introduce a novel in vivo method (Visual Acuity Dry Up; VADU) for testing the visual performance during the dewetting of the pre-lens tear film on a contact lens (CL).
Thirty-nine subjects were fitted with daily disposable CL (Nelfilcon A). Visual performance and dewetting characteristics of the pre-lens tear film were simultaneously assessed using a modified multifunctional topographer (Keratograph 5 M, OCULUS Optikgeräte GmbH, Wetzlar, GERMANY) and the Non-Invasive Keratograph Dry-Up Time (NIKDUT) method. Measures were taken after five minutes and eight hours of CL wear and included the Visual Acuity Dry-Up Time (VADUT; time between last blink and visual breakdown) and the Visual Acuity Dry-Up Area (VADUA; dewetted CL area at visual breakdown) at one (VA+0.1logMAR), two (VA+0.2logMAR) and three (VA+0.3logMAR) log units below maximal visual acuity (VA).
Participants lost one, two or three log units of VA after 13.1 ± 17.4 s, 20.83 ± 21.81, 34.67 ± 29.11 (VADUT), corresponding to a dewetted CL area of 4.82 ± 6.64 mm², 9.5 ± 8.26 and 13.0 ± 8.68 (VADUA), respectively. Differences in VADUT und VADUA for all visual requirements were significant (all p < 0.05). VADUT and VADUA did not vary with CL wear duration (all p > 0.05). A median VA loss of one log unit occurred five seconds after the first dewetting.
The novel VADU method can be used to analyze the role of the tear film stability on the visual performance during CL wear. Hereby, visual loss is quantified based on the threshold definition of the psychometric function.
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Published online: March 05, 2020
Accepted: February 18, 2020
Received in revised form: February 10, 2020
Received: June 24, 2019
© 2020 Published by Elsevier Ltd on behalf of British Contact Lens Association.