The Novel Methods For Tear Clearance Test And Pachymetry Mapping Of Tear Film Using Pentacam

The Novel Methods for Tear Clearance Test and Pachymetry Mapping of Tear Film Using PentacamEnglish AbstractPart I A Novel Method for Tear Fluorescein Clearance Test Using PentacamObjective To report a novel method for quantitative evaluation of tear fluorescein clearance rate (TFCR) using Pentacam Scheimpflug imaging system.Methods Thirty patients with dry eye symptoms and thirty age-matched asymptomatic control subjects were enrolled in this prospective study. Slit-lamp microscopy, tear fluorescein clearance test and Schirmer I test were performed in each participant. The TFCR was evaluated with Pentacam by measuring reflective light intensity (RLI) of fluorescent tear film after instillation of 2μl 1% sodium fluorescein into inferior cul-de-sac (3 min and 5 min later, respectively).Results The Schirmer Score of symptomatic dry eye patients (7.0±6.4 mm/5min, z=-4.266, P<0.0001) was significantly shorter than that of normal controls (18.4±9.6 mm/5min). Meanwhile, significantly decreased TFCR (indicated by a higher tear film RLI) was observed in symptomatic patients. Tear film RLI of symptomatic patients (3 min later,41.1±14.5, z=5.271, P<0.0001; 5 min later, 28.7±10.9, z=4.894, P<0.0001) were significantly higher than those of normal controls (3 min later,17.9±13.5; 5min later,11.0±10.7). An inverse correlation was found between tear film RLI and Schirmer Score (3 min later, tear film RLI, Spearman's rho=-0.45, P= 0.0003; 5 min later, tear film RLI, Spearman's rho=-0.47, P= 0.0002). In this study, the ability of a test to identify dry eye symptoms was analysed by ROC curve:AUC of (3 min later) tear film RLIwas 0.8961; AUC of (5 min later) tear film RLI was 0.8678; AUC of Schirmer I test was 0.8194. The cutoff value of (3 min later) tear film RLI 31.6, had 80% sensitivity and 93% specificity.Conclusions This novel method is convenient and practical for tear fluorescein clearance test in clinic, and it will further the investigation of tear clearance under physiological and pathological conditions. Part II A Novel Method for Pachymetry Mapping of Precorneal Tear Film Using PentacamObjective To report a novel method for pachymetry mapping of human precorneal tear film using Pentacam Scheimpflug imaging system.Methods Precorneal tear film is undetected by Pentacam routinely but that could be well visualized with aid of microdose fluorescein. Twenty dry eye patients and twenty age-matched normal subjects were enrolled in this prospective study. Right eye of each subject was scanned once with Pentacam and rescanned after instillation of 1μl 0.1% fluorescein into inferior cul-de-sac, and the differential map of corneal thickness between the two measurements was identified as the pachymetry map of tear film. Then the central tear film thickness was evaluated and the pattern of each pachymetry map was determined.Results Mean central tear film thickness in dry eyes (22.2±4.5μm) was less than in normal eyes (24.7±3.9μm, t=-1.9280, P= 0.0614). Additionally, In light of spatial distribution of overall precorneal tear film, pachymetry maps of tear film could be generally classified into three patterns:Pattern 1 "thickening upwards", Pattern 2 "uniform distribution", and Pattern 3 "thickening downwards". Tear film pachymetry maps of normal eyes consist of Pattern 1 (8 maps,40%), Pattern 2 (8 maps,40%) and Pattern 3 (4 maps,20%), while those of dry eyes consist of Pattern 1 (14 maps,70%), Pattern 2 (4 maps,20%) and Pattern 3 (2 maps,10%). Dry eyes tended to have a higher proportion of Pattern 1 pachymetry maps than normal eyes, although still no significant difference was found between two groups (CMH x2-2.9630, P=0.0852).Conclusions The novel method feasibly could be used to map the tear film thicknss which provides a valuable means to investigate the spatial distribution of tear film under physiological and pathological conditions.