A standardized visual scale for evaluation of tear fluorescein clearance

To evaluate the correlation and the agreement between a validated fluorometric technique (fluorescein clearance test) and a newly developed, clinically practical standardized visual scale to evaluate tear fluorescein clearance. Also, the ability of this new method to distinguish healthy persons from patients reporting ocular irritation associated with meibomian gland disease (MGD), aqueous tear deficiency (ATD), or both was tested.

Case-controlled study.

Healthy persons (n = 32), patients with MGD associated with rosacea (n = 30), patients with noninflammatory atrophic MGD (n = 24), and patients with ATD (n = 39) were evaluated. There was a similar age and gender distribution in each group.

Each subject completed a symptom questionnaire and had the following tests performed: fluorescein clearance test (FCT), standardized visual scale test (SVST), corneal fluorescein staining, Schirmer 1 test, corneal and conjunctiva sensitivity, and eyelid margin and meibomian gland examination.

The FCT was performed with a CytoFluor II fluorophotometer by measuring the fluorescein concentration in minimally stimulated tear samples collected from the inferior tear meniscus 15 minutes after instillation of 5 microl of 2% sodium fluorescein. The SVST score, ranging from 0 to 6, was obtained by comparing the colors of the standardized visual scale with the color of the lateral inferior tear meniscus immediately before tear collection for the FCT. Severity of ocular irritation was assessed with a symptom questionnaire. Schirmer 1 test (without anesthesia), biomicroscopic meibomian gland evaluation, and corneal fluorescein staining were performed. Corneal and conjunctival sensitivity scores were assessed with the Cochet-Bonnet aesthesiometer. The correlation and the agreement between FCT, FCT corrected for Schirmer test (corrected FCT), SVST, and SVST corrected for Schirmer test (corrected SVST) in separating healthy persons from patients with ATD, MGD, or both were studied. Furthermore, the correlations of FCT, corrected FCT, SVST and corrected SVST, corneal fluorescein staining score, corneal and conjunctiva sensitivity, meibomian gland and eyelid evaluation, and questionnaire score were studied.

The FCT, the corrected FCT, the SVST, and the corrected SVST all showed strong correlation with irritation symptoms, corneal fluorescein staining, Schirmer 1 test score, cornea and conjunctiva sensitivity, and meibomian gland and eyelid pathologic characteristics. The FCT, the corrected FCT, the SVST, and the corrected SVST had a sensitivity in diagnosing MGD, respectively, of 67%, 72%, 69%, and 76%, and of 95%, 97%, 97%, and 97% in diagnosing ATD. The specificity was, respectively, 97%, 96%, 97%, and 94%.

The new standardized visual scale test was equivalent to fluorometric assessment of tear clearance in its correlation with irritation symptoms, ocular surface and eyelid disease, and ocular surface sensitivity. Its ability to separate healthy persons from patients with MGD and ATD was improved by applying a correction factor based on Schirmer test score. The new standardized visual scale test is an accurate and practical method for clinical assessment of fluorescein tear clearance.