# US 5,352,445 A · Lavaux tear test lacrimal equilibration time (LET)

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- Number: US 5,352,445 A
- Document ID: US5352445A
- Status: Granted
- Kind: A
- Application number: 07/879,330
- Filed: 1992-05-07
- Granted: 1994-10-04
- Earliest claimed: 1992-05-07
- Inventors: Joseph E. Lavaux
- Web page: https://patentgrep.com/patent/US5352445A

## CPC

- A61B 3/101: {for examining the tear film}
- A61K 33/14: Alkali metal chlorides; Alkaline earth metal chlorides
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- A61K: PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES (devices or methods specially adapted for bringing pharmaceutical products into particular physical or administering forms A61J3/00; chemical aspects of, or use of materials for deodorisation of air, for disinfection or sterilisation, or for bandages, dressings, absorbent pads or surgical articles A61L; soap compositions C11D)

## Abstract

A method for measuring precorneal tear film stability and diagnosing dry and wet eye conditions. The method comprises stressing baseline visual acuity with the installation of a predetermined ophthalmic preparation and measuring the time to recover normal visual acuity. Once baseline visual acuity is regained and sustained, the Lacrimal Equilibration Time (LET) is recorded. LET measures the quality of precorneal tear film stability and is related to the degree of dry and wet eye condition.

## Claims

### Claim 1

A method of accessing precorneal tear film stability, including symptomatic dry and wet eye conditions, comprising topically applying into the eye a predetermined topical ophthalmic preparation that is visually blurring comprising carboxymethylcellulose sodium 1%, calcium chloride, potassium chloride, purified water, sodium chloride and sodium lactate said eye so treated visually clearing over a period of time by tear film production, tear mixing by the blink force and tear elimination by evaporation and drainage, wherein said period of time measures a precorneal tear film stability and said period of time for visual clearing is substantially longer when dry and wet eye symptoms occur.

### Claim 2 (depends on 1)

The method of claim 1 wherein said visual blurring and clearing is measured by Snellen visual acuity charts or other visual acuity tests used by eyecare professionals.

### Claim 3 (depends on 1)

The method of claim 1 comprising use for determining eye surface health, comfort and lubrication, lowered visual acuity or eye surface disorders.