A novel method for pachymetry mapping of human precorneal tear film using Pentacam with fluorescein.

PURPOSE To report a novel method for pachymetry mapping of human precorneal tear film using Pentacam. METHODS Precorneal tear film is routinely undetected by Pentacam but could be well visualized with the aid of fluorescein. Twenty patients with dry eye and 20 age-matched control subjects with normal eyes were enrolled in this prospective study. The right eye of each subject was scanned once with Pentacam and rescanned after instillation of 1 microL 0.1% fluorescein, 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 +/- 4.5 microm) was less than in normal eyes (24.7 +/- 3.9 microm) (Student's t-test, P = 0.0614). Additionally, the tear film pachymetry map could be classified into three patterns: pattern 1, thickening upward; pattern 2, uniform distribution; pattern 3, thickening downward. Tear film pachymetry maps of normal eyes consisted of pattern 1 (40%), pattern 2 (40%), and pattern 3 (20%), whereas those of dry eyes consisted of pattern 1 (70%), pattern 2 (20%), and pattern 3 (10%). Dry eyes tended to have a higher proportion of pattern 1 pachymetry maps than normal eyes, though still no significant difference was found between two groups (Cochran-Mantel-Haenszel chi(2) test, P = 0.0852). CONCLUSIONS This novel method feasibly could be used to map tear film thickness, and it provides a valuable means to investigate the spatial distribution of tear film.