Tears are the natural way to keep eyes moist, and tears are important for good vision and healthy eyes. Eyes without enought tears get dry and sore. The natural and normal way to stimulate secretion of tears is by turning on cold sensors that are located on the cornea of the eye. Tear are normally released across the eyeball in a finely balanced system that balances out that natural evaporation. But sometimes there is not enough tear secretion to balance out the evaporation of tears and eyes can get sore. The aim here is to test whether menthol in its vapor form may possibly turn on those cold sensors and thus cause secretion of tears. Use of menthol vapors may be like having a switch to release more tears. The aim of this clinical trial is to test the hypothesis that a menthol solution applied onto a cheek will release enough menthol vapor into the air flowing up over the eye's cornea to stimulate cold sensors enough to make a tear flow from the eye. If the hypothesis that menthol safely stimulates tear secretion in healthy people proves to be correct, then this clinical trial may inspire more new research into the use of menthol as an alternative to the use of eye drops for some people.
This is a proof-of-principle clinical trial. It is a double-blind, placebo-controlled, randomized clinical trial. Participants are not being seen by a physician for eye disease, and there is a 50% probability that a participant will receive active treatment, or 50% probability that they will just receive the carrier oil with nothing in it (placebo).
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
QUADRUPLE
Enrollment
30
To facilitate reproducible and correct application of the solution, the subject wears glasses while the product is applied. The solution is rolled onto one cheek by rolling it to an area of about 2cm X 2cm at the cheekbone, underneath the bottom rim of the glasses worn. This method delivers about 12 mg solution, i.e. 2.4 mg menthol to one cheek. Or this method delviers 12 mg of placebo oil. The subject then sits in still air for 5 minutes, at which point tissue is wiped across the skin below the bottom eyelashes to permit the weighing of secreted tear.
To facilitate reproducible and correct application of the Placebo oil, the subject wears glasses while the product is applied. The Placebo oil is rolled onto one cheek by rolling it to an area of about 2cm X 2cm at the cheekbone, underneath the bottom rim of the glasses worn. This method delivers zero active agent. The subject then sits in still air for 5 minutes, at which point tissue is wiped across the skin below the bottom eyelashes to permit the weighing of secreted tear.
Stearacl Incorporated.
Toronto, Ontario, Canada
Objective measure of tear stimulation Yes or No
The outcome is the binary yes/no observation of active tear secretion that overflows to the skin below the bottom eyelashes. Subject sits in still air while wearing glasses to ensure correct positioning of the topical application. The solution of menthol or placebo is dispensed from a roller-ball bottle to the right eye only, onto an area about 2cm x 2 cm just below the bottom rim of the glasses; that is, inferior to the pupil, and in line with the bottom of the nose. Within 5 minutes of sitting in still air, If moisture is evident below the bottom eyelashes, glasses are removed and tissue is dabbed, or wiped under bottom eyelash to take up the tear. If that wipe increases the weight of the tissue by at least 6 milligrams, then a "Yes" response is recorded. If after 5 minutes a wipe of tissue across the bottom eyelashes of the right eye does not increase the weight of tissue by at least 6 milligrams, a "No" is recorded to indicate that there was no increase in tear secretion.
Time frame: Participant is observed for 5 minutes after application, to record tear-weight data, and the related questions that are asked are completed within 10 minutes after applicaiton.
Weight of tear
The actual measured weight of the tear(s) collected onto the tissue, from below the right eye.
Time frame: Measured at 5 minutes after dose application.
Was there a subjective difference between left and right eyes in terms of sense if moisture
Response to the question: " Which eye feels more moist? Left eye more moist or No difference (both same) or ….Right eye more moist"
Time frame: 5 to 10 minutes after application
Weight of nasal secretion blown into tissue.
The purpose is to test whether there is evidence of shared innervation of TRPM8 receptors (the menthol-responsive sensors for cold) in cornea and nasal subepithelium. The particpant holds closed the left nostril, while blowing into a tissue from the right nostril. The increase in weight of tissue is measured.
Time frame: Within 10 minutes of applying the dose.
Weight of nasal secretion
Subject blows their nose into a tissue, and the increase in tissue weight is recorded.
Time frame: 5 to 10 minutes after application
Discomfortable feeling at the treated eye.
At your right eye, was there anything uncomfortable feeling? Nothing mild moderate severe (choose one)
Time frame: 10 minutes
Degree of cooling or pain at the skin where the dose was applied.
At the skin of the cheek, where it was rolled on, did you feel (choose one) COOLING OR NOTHING OR PAIN If cooling or pain, how strong was the feeling? (choose one) Nothing mild moderate severe
Time frame: 10 minutes
Did the procedure increase sense of runny nose?
Did you feel a runny nose, or nasal secretion during the 5 minutes of waiting? No or Yes And if Yes, at which nostril? Left or Right or Both nostrils
Time frame: 10 minutes
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