Objective assessment of optical quality in dry eye disease using a double-pass imaging system

To assess optical quality dynamics using a double-pass (DP) system in patients with dry eye disease (DED).

Seventy-six eyes with DED and 44 control subjects were enrolled in this study. Each patient underwent ocular surface evaluation including fluorescein corneal staining and Schirmer's II test. Ocular Surface Disease Index (OSDI) questionnaire was used to assess subjective symptoms. Optical quality dynamics and tear film instability was analyzed using a DP system (HD Analyzer^TM, Visiometrics, Spain). Mean objective scatter index (OSI), maximum and minimum OSI, difference between maximum and minimum OSI (ΔOSI) were recorded with 40 consecutive scans over 20 s.

The DED group had pronounced impairment of optical quality compared to the control group. Mean OSI (4.29±4.07), minimum (3.22±3.51) and maximum (5.72±4.52) OSI, ΔOSI (2.50±1.96), OSDI score (36.94±16.55), and fluorescein corneal staining (0.79±0.96) were statistically significantly higher than controls (p<0.05). Schirmer's II test was statistically significantly lower in the DED group compared to controls (10.08±7.85, 26.41±6.75, respectively; p<0.001). Three patterns of dynamic changes of OSI were proposed: ladder (continuous increase of OSI), seesaw (instability of OSI without improvement after blinking), and plateau (steady-high OSI). The ladder group showed the highest value of maximum OSI (6.93±4.13; p=0.03) and ΔOSI (3.76±2.08; p<0.001).

DP imaging system provides an objective measurement of the visual quality in DED. Tear film instability may be assessed by dynamic changes of OSI over 20 s. In particular, the highest OSI values were observed in the ladder pattern group.