Abstract: TearLab variability

Clinical Utility of Objective Tests for Dry Eye Disease: Variability Over Time and Implications for Clinical Trials and Disease Management.

PURPOSE:
To evaluate the efficacy of commonly used biomarkers in dry eye disease management in a longitudinal observational case series study followed by an interventional study in a subset of subjects treated with cyclosporine A (0.05%).

METHODS:
Bilateral tear osmolarity, Schirmer, tear film breakup time (TBUT), staining, meibomian grading, and Ocular Surface Disease Index were measured for a period of 3 consecutive months in participants recruited from a clinic-based population at 2 study sites. Fifty-two subjects completed the study (n = 16 mild/moderate, n = 36 severe; age, 47.1 ± 16.1 years). After the 3-month observation period, severe dry eye patients were prescribed topical cyclosporine A and evaluated for an additional 3 months.

RESULTS:
Tear osmolarity (8.7 ± 6.3%) exhibited significantly less variability over a 3-month period than corneal staining (12.2 ± 8.8%, P = 0.040), conjunctival staining (14.8 ± 8.9%, P = 0.002), and meibomian grading (14.3 ± 8.8%, P < 0.0001) across the entire patient population. Osmolarity also demonstrated less variation than TBUT (11.7 ± 9.0%, P = 0.059), Schirmer tests (10.7 ± 9.2%, P = 0.67), and Ocular Surface Disease Index (9.3 ± 7.8%, P = 0.94), although the differences were not significant. Variation in osmolarity was less for mild dry eye patients (5.9 ± 3.1%) than severe dry eye patients (10.0 ± 6.9%, P = 0.038). After treatment, average osmolarity and variability were lowered from 341 ± 18 mOsm/L to 307 ± 8 mOsm/L (P < 0.0001, n = 10). A downward trend in symptoms followed changes in osmolarity, declining from 44 ± 17 mOsm/L to 38 ± 18 mOsm/L (P = 0.35). None of the other signs demonstrated a change after treatment.

CONCLUSIONS:
Over a 3-month period, tear film osmolarity was found to have the lowest variability among commonly used signs of dry eye disease. Reductions in osmolarity preceded changes in symptoms during therapy.

Cornea. 2012 Apr 3. [Epub ahead of print]
Sullivan BD, Crews LA, Sönmez B, de la Paz MF, Comert E, Charoenrook V, de Araujo AL, Pepose JS, Berg MS, Kosheleff VP, Lemp MA.
Source
*TearLab Corporation, San Diego CA †Department of Ophthalmology, School of Medicine, Ondokuz Mayis University, Samsun, Turkey ‡Centro de Oftalmologia Barraquer, Barcelona, Spain §Pepose Vision Institute, St Louis, MO ¶Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St Louis, MO ‖Department of Ophthalmology, Georgetown University, Washington, DC **Department of Ophthalmology, George Washington University, Washington, DC.

Abstract: TearLab

This is the sort of thing that makes me wish I'd ever learned something about statistics. I don't know how to translate this. To someone as ignorant as me it could be anything from validating the usefulness of the tool to politely saying it's just a marketing gimmick stupid. Somebody with a mathematical bone in their body care to comment on what 33 means here?

Reproducibility and repeatability of the OcuSense TearLab™ osmometer.

BACKGROUND:
Some studies report that increased tear osmolarity is a reliable indicator of dry eye syndrome (DES). The OcuSense TearLab™ osmometer requires less than a 100-nl sample of tears and provides an instant quantitative result. Our aim was to clinically evaluate this instrument in terms of its reproducibility and repeatability.
METHODS:
Twenty-nine participants who ranged in age from 19 to 49 years (mean ± SD: 23.3 ± 5.5 years) were recruited. Osmolarity readings were collected by two operators, in two sessions separated by 1 or 2 weeks in order to assess test reproducibility and repeatability.
RESULTS:
The coefficient of reproducibility was 39 mOsms/l; the coefficient of repeatability was 33 mOsms/l.
CONCLUSIONS:
Our mean coefficient of variation over four readings for 29 subjects is 2.9%, which compares well with that reported by the manufacturer. Our results inform practitioners about the level of change over time that can be considered clinically relevant for healthy subjects. This value is 33mOsms/l; any change smaller than this could be attributed to measurement noise.

Graefes Arch Clin Exp Ophthalmol. 2012 Feb 21. [Epub ahead of print]
Eperjesi F, Aujla M, Bartlett H.
Source
Ophthalmic Research Group, School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK, f.eperjesi@aston.ac.uk.