Plain English Summary
Background and study aims
This is a research project that has two studies.
Study A
A Goldmann tonometer (GAT) is the standard method used to measure the internal pressure (intraocular pressure) of the eye by pressing the cornea (the transparent dome-shaped window covering the front of the eye) with a small flat piece. The aim of Study A is to develop a new technology to measure the biomechanical (structural and functional) properties of the cornea. Characterising these properties are vital for treating conditions (e.g. diseases or injury) that effect the corneas ability to maintain its shape and its ability to focus light, and therefore effect an persons ability to see. Corneal biomedical properties also affect how some diseases (for example keratoconus, where the shape of the cornea alters to resemble a cone) are treated, the accuracy of intraocular pressure (IOP) measurements, outcome of eye surgery procedures and the design of contact lenses. Since the new device will come into contact with the eye, anaesthetic must be used before measurements are taken. Here, we want to find out how reliable the new device is and how comfortable it is to use. It is similar to a GAT tonometer, but is operated by a computer and uses a curved contact tip. The device will press against the cornea and move it inward and backward by about half of a millimetre. This will be done 3 times using different loading rates.
Study B
The aim of this study is to compare corneal stiffness and hysteresis (elastic and viscoelastic) measurements of the new device compare to those taken by another device called the Ocular Response Analyzer (ORA). The stiffness measurements will also be compared to that taken by a new non-contact device called the Corvis ST. The study will also consider the stability of the measurements when the device and the eye are not accurately aligned.
Who can participate?
The study population will be healthy volunteers and participants with raised intraocular pressure, with or without ocular hypotensive therapy. Patients will be screened against the inclusion and exclusion criteria for the study.
What does the study involve?
Participants recruited to study A will undertake the following assessments:
1. General Medical and Ophthalmic History
2. Visual Acuity Check (standard check of your vision on a letter chart)
3. Biomicroscopy, Ophthalmoscopy, Gonioscopy (standard check of the health of the eye)
4. Corneal stiffness measurements with the device under study using three different loading rates.
5. Biomicroscopy
6. A short questionnaire about comfort during the measurements
Participants recruited to study B will undertake the following assessments:
1. General Medical and Ophthalmic History
2. Visual Acuity Check (standard check of your vision on a letter chart)
3. Biomicroscopy, Ophthalmoscopy, Gonioscopy (standard check of the health of the eye)
4. Eye Pressure measurements with Goldmann applanation tonometer and dynamic contour tonometer.(These are the standard clinical methods of checking the eye pressure during a routine visit to the optometrist or eye doctor. We will need to instil one drop of a mild topical anaesthetic, which will wear off after approximately 20 minutes. You are advised to refrain from rubbing your eye until this time.).
5. Corneal Hysteresis (CH) and Corneal Resistance Factor (CRF) will be measured by the Ocular Response Analyzer (ORA).
6. Corneal force-deformation response measurements using the device.
7. The ophthalmic examination is repeated to search for any adverse effects caused by using the prototype.
What are the possible benefits and risks of participating?
Participants will volunteer to participate in this study which aims to derive the stress-strain behaviour of corneal tissue from the in-vivo stiffness measurements. Quantifying corneal mechanical properties is also important when these properties impact on the treatment of diseases such as keratoconus, accuracy of IOP measurements, improving the outcome of refractive surgery procedures and design of contact lenses.
Where is the study run from?
1. Ninewells Hospital (UK)
2. Moorfields Hospital (UK)
3. Aberdeen Royal Infirmary (UK)
The study is managed by the Liverpool Clinical Trials Unit (UK)
When is the study starting and how long is it expected to run for?
July 2014 to February 2015
Who is funding the study?
Engineering and Physical Sciences Research Council (UK)
Who is the main contact?
Mr M Bickerstaff
oasis@liv.ac.uk
Trial website
Additional identifiers
EudraCT number
2014-002712-16
ClinicalTrials.gov number
Protocol/serial number
UoL000983
Study information
Scientific title
Determination of corneal biomechanical properties in-vivo using a contact device: a single-arm, observational study
Acronym
DetCorBio
Study hypothesis
This is an observational study to determine the corneal biomedical properities of patients with high IOP using a novel contact device. The device applies indentation to the participants cornea and monitors the corneal deformation and load to measure the overall stiffness of the cornea. A computer is used to control the device and to store the measurements.
The cornea is a load-bearing tissue whose primary function is to focus light on the retina. The mechanical properties of the cornea are important in maintaining this function under the effect of actions such as intraocular pressure (IOP), eyelid movement and external impacts. Characterising the mechanical properties of the cornea is of critical clinical importance when action is to be taken to remedy deterioration in mechanical performance, caused for instance by disease or injury, and leading to corneal failure to maintain its shape and focus light. Quantifying corneal mechanical properties is also important when these properties impact on the treatment of diseases such as keratoconus, accuracy of IOP measurements, outcome of refractive surgery procedures and design of contact lenses
Ethics approval
Not provided at registration
Study design
Single-arm study of a non-CE-marked medical device
Primary study design
Observational
Secondary study design
Other
Trial setting
Other
Trial type
Diagnostic
Patient information sheet
Not available in web format, please use the contact details below to request a patient information sheet
Condition
Increased intraocular pressure of eye
Intervention
The device applies indentation to the participants cornea and monitor the corneal deformation and load to measure the overall stiffness of the cornea. A computer is used to control the device and to store the measurements.
Intervention type
Device
Phase
Not Applicable
Drug names
Primary outcome measure
Study B
1. The correlation between the force-displacement measurements made by the device and:
1.1. The overall stiffness as estimated mathematically based on the corneas thickness, topography and age
1.2.The differences in IOP readings made by two devices; namely the Goldmann Applanation Tonometer or GAT (which is known to be affected by corneal stiffness), and the Dynamic Contour Tonometer or DCT (which is known to be much less affected by corneal stiffness than GAT),
1.3. Corneal Resistance Factor, CRF (a stiffness-related parameter) as provided by the Ocular Response Analyzer (ORA).
1.4. The stiffness estimate provided by Corvis ST; a recently-released and not yet fully validated, non-contact device.
2. The correlation between the tissue hysteresis (difference in stress-strain behaviour under loading and unloading conditions) measured by the new device and the Corneal Hysteresis (CH) parameter provided by the Ocular Response Analyzer (ORA)
3. Estimation of tissue viscoelasticity
Secondary outcome measures
Study A
1. The reliability and repeatability of the device output
2. Comfort of use and tolerance of the new device
3. Assessment of general operation of device
Overall trial start date
01/07/2014
Overall trial end date
01/02/2015
Reason abandoned (if study stopped)
Lack of funding/sponsorship
Eligibility
Participant inclusion criteria
1. At least 18 years of age
2. Normal findings in the medical history unless the investigator considers an abnormality to be clinically irrelevant
3. Normal ophthalmic findings, other than high IOP
4. Astigmatism <2D
5. Potential to complete the study and comply with appropriate instructions
6. Signature on the informed consent form
Participant type
Patient
Age group
Adult
Gender
Both
Target number of participants
70
Participant exclusion criteria
1. Corneal pathology or previous intra- or extra-ocular surgery, including refractive surgery (e.g., radial keratotomy, photorefractive keratotomy, LASIK, intracorneal ring), retinal surgery (e.g., buckle, photocoagulation), or implantation of a primary or secondary intraocular lens
2. Contact lens wearing within 3 days (rigid contact lenses) or 1 day (soft contact lenses) prior to study day
3. Inability to fully understand the informed consent
4. Participants who are diabetic
Recruitment start date
01/07/2014
Recruitment end date
01/02/2015
Locations
Countries of recruitment
United Kingdom
Trial participating centre
University of Liverpool
Liverpool
L69 3GH
United Kingdom
Funders
Funder type
Research organisation
Funder name
Engineering and Physical Sciences Research Council
Alternative name(s)
EPSRC
Funding Body Type
government organisation
Funding Body Subtype
National government
Location
United Kingdom
Results and Publications
Publication and dissemination plan
Not provided at time of registration
Intention to publish date
Participant level data
Not provided at time of registration
Basic results (scientific)
Publication list