Investigation in Corneal Sensation and Contact Lens Wear

Study Overview
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Brief Summary
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The aim is to find out more about how corneal sensory fibres react to different types of stimuli (liquid / tactile / nylon thread) and how this can be consciously perceived by the individual. Is it possible to generate a stimulus that delivers a repeatable and reliable response within a useful stimulus force range which allows an interpretation / evaluation of normal / expected activity of superficial nerve fibres in the cornea? The study group will be divided into three groups of individuals: two groups with different types of contact lenses (CL) and one without CL, as sensitivity changes are thought to occur with CL wear. A very interesting research question is to find out, if such sensitivity differences can be detected with the nature of the stimuli applied in this study.

Detailed Description
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The aim of this study is to gain more physiological knowledge about ocular surface sensation (corneal sensitivity), with application of three different concepts employing different types of stimuli for triggering a response from the pain sensitive nerve endings in the superficial cornea: 1) tactile method: a round plastic nozzle (2 mm diameter) is applied to the ocular surface with a defined, low force for a duration of 100ms. 2) liquid jet method: a liquid jet (isotonic saline) of a temperature to match ocular surface temperature is applied to the ocular surface with low pressure and low volume, from a distance of 15 mm.3) commercially available Cochet Bonnet esthesiometer (nylon thread). The study group will be divided into three groups of individuals: two groups with different types of contact lenses (CL) and one without CL, as sensitivity changes are thought to occur with CL wear. A very interesting research question is to find out, if such sensitivity differences can be detected with the nature of the stimuli applied in this study. Current knowledge about human corneal sensitivity is limited, as applied methods for ocular surface sensation measurement are limited with regards to reproducibility / accuracy. Corneal sensitivity represents a neurological response from the free nerve endings within the epithelium. They are sensitive to mechanical, electrical, chemical or thermal stimuli and hence have a protective function for the cornea. Corneal nerves play an important role in cell growth and proliferation of epithelial cells, wound healing and repair. In experimental studies, corneal denervation has been reported to result in epithelial changes: increased permeability, decreased proliferation, changed appearance and delayed wound healing. Therefore, intact corneal innervation is required to maintain the integrity of a normal corneal epithelium. Corneal sensory nerves are believed to play an important role in maintaining the resting tear flow, as their afferent impulses from the ocular surface lead to a reflex response, best described by the lacrimal functional unit: an integrated system comprising the ocular surface tissues (cornea, corneal limbus, conjunctiva, conjunctival blood vessels, and eyelids), the tear secreting components (main and accessory lacrimal glands, meibomian glands, conjunctival goblet, and epithelial cells), and the sensory and motor nerves that connect them. Current knowledge about ocular surface sensitivity is insufficient, as currently available measurement possibilities lack repeatability and accuracy. Before a new instrument can be developed, more research is required, in order to find a suitable concept for precise sensitivity measurement. For this purpose, two new different concepts with different / new stimulus types will be applied repeatably on healthy eyes in this study. The aim is to find out more about how corneal sensory fibres react to different types of stimuli (liquid / tactile / nylon thread) and how this can be consciously perceived by the individual. Is it possible to generate a stimulus that delivers a repeatable and reliable response within a useful stimulus force range which allows an interpretation / evaluation of normal / expected activity of superficial nerve fibres in the cornea? The study group will be divided into three groups of individuals: two groups with different types of contact lenses (CL) and one without CL, as sensitivity changes are thought to occur with CL wear.

Official Title
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Investigation in Variability and Repeatability of Corneal Sensation in a Normal Population and Contact Lens Wearers

Conditions
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Cornea, Sense Loss; Cornea

Intervention / Treatment
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* Device: Tactile Esthesiometer Prototype
* Device: Liquid Jet Esthesiometer Prototype
* Device: Cochet Bonnet esthesiometer


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Group A: Silicone hydrogel (SiHy) CL wear at least 3 days per week and at least 8 hours per day; 18 - 50 years of age; healthy eyes with OSDI </= 13 Group B: Rigid gas permeable (RGP) CL wear at least 3 days per week and at least 8 hours per day; 18 - 50 years of age; healthy eyes with OSDI </= 13 Group C: No current CL wear for at least 3 months; 18 - 50 years of age; healthy eyes with OSDI </= 13 Exclusion Criteria: Systemic disease that may affect ocular health, such as diabetes Injury and history of operations on the anterior segment of the eye regular application of systemic or ocular medication known to affect the tear film, specifically on the day of measurement

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Group A: SiHy CL<br>Silicone hydrogel (SiHy) CL wear at least 3 days per week and at least 8 hours per day; | Device: Tactile Esthesiometer Prototype<br>* A round plastic nozzle (1.8mm diameter) used as a stimulus for corneal sensation threshold measurement<br>Device: Liquid Jet Esthesiometer Prototype<br>* Balanced salt solution with a pH value similar to the tear film uesd as a liquid jet stimulus for corneal sensation threshold measurement<br>Device: Cochet Bonnet esthesiometer<br>* A nylon thread (0.12mm diameter) used as a stimulus for corneal sensation threshold measurement<br>|
| Experimental: Group B: RGP CL<br>Rigid gas permeable (RGP) CL wear at least 3 days per week and at least 8 hours per day; | Device: Tactile Esthesiometer Prototype<br>* A round plastic nozzle (1.8mm diameter) used as a stimulus for corneal sensation threshold measurement<br>Device: Liquid Jet Esthesiometer Prototype<br>* Balanced salt solution with a pH value similar to the tear film uesd as a liquid jet stimulus for corneal sensation threshold measurement<br>Device: Cochet Bonnet esthesiometer<br>* A nylon thread (0.12mm diameter) used as a stimulus for corneal sensation threshold measurement<br>|
| Experimental: Group C: no CL wear<br>No current CL wear for at least 3 months; | Device: Tactile Esthesiometer Prototype<br>* A round plastic nozzle (1.8mm diameter) used as a stimulus for corneal sensation threshold measurement<br>Device: Liquid Jet Esthesiometer Prototype<br>* Balanced salt solution with a pH value similar to the tear film uesd as a liquid jet stimulus for corneal sensation threshold measurement<br>Device: Cochet Bonnet esthesiometer<br>* A nylon thread (0.12mm diameter) used as a stimulus for corneal sensation threshold measurement<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Repeatability of mechanical corneal sensation thresholds with the liquid jet protoype esthesiometer | Evaluation of repeatability of mechanical corneal sensation thresholds for the measurement with the liquid jet esthesiometer prototype instrument (in mbar): the corneal sensation thresholds will be obtained with the double staircase method (with forced choice) and the stimulus represents a liquid jet (consisting of isotonic saline solution). | two weeks | 
| Repeatability of mechanical corneal sensation thresholds with the tactile prototype esthesiometer | Evaluation of variability / repeatability of mechanical corneal sensation thresholds for the measurement with the tactile esthesiometer prototype instrument (in mN): the corneal sensation thresholds will be obtained with the double staircase method (with forced choice) and the stimulus represents a small, round plastic ball. | two weeks | 
| Repeatability of mechanical corneal sensation thresholds with the Cochet Bonnet esthesiometer | Evaluation of repeatability of mechanical corneal sensation thresholds for the measurement with the Cochet Bonnet instrument (in mN): the corneal sensation thresholds will be obtained with the double staircase method (with forced choice) and the stimulus represents a nylon thread, whereby its force is proportional to the length of the nylon thread applied to the corneal surface. | two weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Correlation between corneal sensation thresholds with the Cochet Bonnet esthesiometer | Correlation between corneal sensitivity thresholds (in mN) obtained with the Cochet Bonnet esthesiometer | one day | 
| Correlation between corneal sensation thresholds with the liquid jet prototype esthesiometer | Correlation between corneal sensitivity thresholds (in mbar) obtained with the liquid jet prototype esthesiometer | one day | 
| Correlation between corneal sensation thresholds with the tactile prototype esthesiometer | Correlation between corneal sensitivity thresholds (in mN) obtained with the tactile prototype esthesiometer | one day | 
| Comparison of corneal sensation thresholds, obtained with the Cochet Bonnet esthesiometer, between the three groups in the study population | Comparison of corneal sensation thresholds obtained with the Cochet Bonnet esthesiometer between the three groups in the study population | two weeks | 
| Comparison of corneal sensation thresholds, obtained with the liquid jet prototype esthesiometer, between the three groups in the study population | Comparison of corneal sensation thresholds, obtained with the liquid jet prototype esthesiometer, between the three groups in the study population | two weeks | 
| Comparison of corneal sensation thresholds, obtained with the tactile prototype esthesiometer, between the three groups in the study population | Comparison of corneal sensation thresholds, obtained with the tactile prototype esthesiometer, between the three groups in the study population | two weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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cornea, ocular surface sensation, corneal sensitivity, contact lens wear