Investigation in Corneal Sensation and Contact Lens Wear

Not Applicable

Completed

Conditions: Sense Loss; Cornea
Cornea

Interventions: Device: Tactile Esthesiometer Prototype
Device: Liquid Jet Esthesiometer Prototype
Device: Cochet Bonnet esthesiometer

Registration Number: NCT04804592

Lead Sponsor: Daniela Nosch

Brief Summary: 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: 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.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 111

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

Study & Design

Study Type: INTERVENTIONAL

Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Group B: RGP CL	Tactile Esthesiometer Prototype	Rigid gas permeable (RGP) CL wear at least 3 days per week and at least 8 hours per day;
Group A: SiHy CL	Cochet Bonnet esthesiometer	Silicone hydrogel (SiHy) CL wear at least 3 days per week and at least 8 hours per day;
Group B: RGP CL	Cochet Bonnet esthesiometer	Rigid gas permeable (RGP) CL wear at least 3 days per week and at least 8 hours per day;
Group A: SiHy CL	Tactile Esthesiometer Prototype	Silicone hydrogel (SiHy) CL wear at least 3 days per week and at least 8 hours per day;
Group A: SiHy CL	Liquid Jet Esthesiometer Prototype	Silicone hydrogel (SiHy) CL wear at least 3 days per week and at least 8 hours per day;
Group B: RGP CL	Liquid Jet Esthesiometer Prototype	Rigid gas permeable (RGP) CL wear at least 3 days per week and at least 8 hours per day;
Group C: no CL wear	Tactile Esthesiometer Prototype	No current CL wear for at least 3 months;
Group C: no CL wear	Cochet Bonnet esthesiometer	No current CL wear for at least 3 months;
Group C: no CL wear	Liquid Jet Esthesiometer Prototype	No current CL wear for at least 3 months;

Primary Outcome Measures

Name	Time	Method
Repeatability of mechanical corneal sensation thresholds with the liquid jet protoype esthesiometer	two weeks	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).
Repeatability of mechanical corneal sensation thresholds with the tactile prototype esthesiometer	two weeks	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.
Repeatability of mechanical corneal sensation thresholds with the Cochet Bonnet esthesiometer	two weeks	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.

Secondary Outcome Measures

Name	Time	Method
Correlation between corneal sensation thresholds with the tactile prototype esthesiometer	one day	Correlation between corneal sensitivity thresholds (in mN) obtained with the tactile prototype esthesiometer
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 Cochet Bonnet 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 liquid jet 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	Comparison of corneal sensation thresholds, obtained with the tactile prototype esthesiometer, between the three groups in the study population
Correlation between corneal sensation thresholds with the Cochet Bonnet esthesiometer	one day	Correlation between corneal sensitivity thresholds (in mN) obtained with the Cochet Bonnet esthesiometer
Correlation between corneal sensation thresholds with the liquid jet prototype esthesiometer	one day	Correlation between corneal sensitivity thresholds (in mbar) obtained with the liquid jet prototype esthesiometer

Trial Locations

Locations (1): Institute of Optometry, FHNW
🇨🇭
Olten, Solothurn, Switzerland

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