Highlights
- •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.
Abstract
Purpose
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).
Methods
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).
Results
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.
Conclusions
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.
Graphical abstract

Graphical Abstract
Keywords
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Article info
Publication history
Published online: March 05, 2020
Accepted:
February 18,
2020
Received in revised form:
February 10,
2020
Received:
June 24,
2019
Identification
Copyright
© 2020 Published by Elsevier Ltd on behalf of British Contact Lens Association.