Dynamic changes in the air-tear film interface modulation transfer function.
OBJECTIVE
To determine objectively the changes in the optical quality of the air-tear film interface by measuring the modulation transfer function (MTF) of the anterior surface of the film.


METHODS
Air-tear film interface MTF was determined from the wavefront aberration obtained from corneal elevation maps and custom software. MTF and Strehl ratio were derived for 3 (photopic) and 7 (mesopic) mm pupils, in 14 healthy young subjects at various intervals after a blink (1 second up to 15 seconds). Fluorescein tear break-up times (TBUT) measured by a standard method were determined for clinical correlation purposes


RESULTS
The MTF profile varies as a function of the time post-blink, showing the highest values at 6-7 seconds. Strehl ratio showed a similar dynamic pattern reaching its maximum level, on average, at 6.2 +/- 0.4 seconds after a blink. Minimum levels occur from 10 seconds after a blink, worsening with larger times. Strehl ratio values were correlated with clinical TBUT: minimum values were found to occur earlier for those subjects with shorter TBUT and vice versa.


CONCLUSIONS
Air-tear film interface MTF and Strehl ratio estimation are useful metrics for optical quality analysis of tear film changes.
Optometry Research Group, Optics Department, Faculty of Physics, University of Valencia, C/ Dr. Moliner 50, 46100 Burjassot, Valencia, Spain.
Teresa
T
Ferrer-Blasco
Santiago
S
García-Lázaro
Robert
R
Montés-Micó
Alejandro
A
Cerviño
Jose M
JM
González-Méijome
D000328:Adult; D000388:Air; D001767:Blinking / Q000502:physiology*; D003315:Cornea / Q000502:physiology*; D019781:Corneal Topography; D057108:Corneal Wavefront Aberration / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D013666:Tears / Q000502:physiology*