  Purpose: To evaluate the efficacy of a recently proposed method for
characterizing tear film dynamics using non-invasive high speed
videokeratoscopy in assessing the loss of homeostasis of tear film. Methods:
Thirty subjects, from a retrospective study, of which 11 were classified as dry
eye and 19 as normal, were included. High speed videokeratoscopy measurements
were performed using E300 videokeratoscope (Medmont Pty., Ltd, Melbourne,
Australia). Raw data was analyzed using a recently proposed method to estimate
the dynamics of the tear film, based on a fractal dimension approach. This
method provides three time-varying indicators related to the regularity of the
reflected rings: Tear Film Surface Quality (TFSQ) indicator, Breaks Feature
Indicator (BFI) and Distortions Feature Indicator (DFI). From each indicator
five parameters were extracted and analyzed, including non-invasive break up
time, mean value of the indicator in the stability phase, mean value of the
indicator in the whole inter blink interval, mean value of the indicator in the
levelling phase and the general trend of the time series. Receiver Operating
Characteristic were used to determine the sensitivity and specificity of each
parameter in dry eye detection. Results: The best discrimination performance
between dry eye and normal subjects was achieved with the BFI non-invasive
break up time parameter, with an area under the curve of 0.85. For a cut off
value of 10 s the sensitivity was 100% and the specificity 84%. Conclusions:
The analyzed method improves the assessment of tear film homeostasis in
comparison to previous high speed videokeratoscopy methods showing higher
potential in assisting dry eye diagnosis.
