The Dry Eye Zone

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Abstract: Measuring pachymetry of tear film

A Novel Method for Pachymetry Mapping of Human Precorneal Tear Film Using Pentacam with Fluorescein.
Invest Ophthalmol Vis Sci. 2009 Aug 26. [Epub ahead of print]
Zhuang H, Zhou XT, Xu J.
Department of Ophthalmology, Eye and ENT Hospital of Fudan University, Shanghai, China.

Purpose. To report a novel method for pachymetry mapping of human precorneal tear film using Pentacam.

Methods. Precorneal tear film is undetected by Pentacam routinely but that could be well visualized with aid of 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 1 microl 0.1% fluorescein. And the differential map of corneal thickness between two measurements is identified as the pachymetry map of tear film. Then central tear film thickness was evaluated and pattern of each pachymetry map was determined.

Results. The 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, tear film pachymetry map could be 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 (40%), Pattern 2 (40%) and Pattern 3 (20%), while those of dry eyes consist 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, although still no significant difference was found between two groups (CMH chi2 test, 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.