Objective Scatter Index May Explain Visual Acuity Decline in Dry Eye Disease

Objective scatter index metrics may be used to assess and diagnose dry eye disease (DED), as they correlate with subjective visual performance and patient-reported symptoms, according to a study published in Eye and Vision. Functional visual acuity-related metrics, which include mean functional visual acuity, visual maintenance ratio, and visual acuity break-up time, may quantify visual acuity decline in these patients, the report shows. 

Researchers enrolled 57 participants in the prospective, case-controlled study, including individuals with DED (n=37; 86.5% women; mean age, 24.6 years) and age-matched control group participants (n=20; 65% women; mean age 24.6 years), to determine the effect of tear film instability in DED. Participants underwent visual performance and tear film optical quality assessment in real-time and reported DED symptoms using the Ocular Surface Disease Index (OSDI) questionnaire. 

The team developed a real-time analysis system to simultaneously and repeatedly measure functional visual acuity and objective scatter index while under blink suppression conditions for 20 seconds and assessed changes between dynamic and baseline objective scatter index.  

Correlation coefficients revealed moderate correlations between mean objective scatter index and mean functional visual acuity (0.53), visual maintenance ratio (−0.56), and visual acuity breakup time (−0.53; P <.01 for all). Objective scatter index demonstrated a moderate-to-high correlation with the same functional visual acuity-related parameters (correlation coefficients: −0.62, 0.71, and 0.64, respectively, P <.01 for all). 

The simultaneous, real-time analysis system metrics moderately correlated with patient-reported symptoms and visual acuity break-up time and had the highest correlation coefficients with OSDI total, ocular symptoms, and vision-related function (−0.64, −0.63, −0.62, respectively, P <.01 for all). Objective scatter index maintenance ratio showed the best performance for detecting DED, with a sensitivity of 95.0% and specificity of 83.8%. 

“Simultaneous real-time measurement of the subjective visual acuity decline and objective optical quality deterioration can facilitate and deepen the understanding of the interrelationship between tear film instability and visual performance as well as the underlying mechanism of visual fluctuation in DED,” according to the researchers. 

Study limitations include convenience sampling and failure to assess the intra- and inter-observer variability of the simultaneous measurement with the simultaneous real-time analysis system prototype.