Photoreceptor Sensitivity Thresholds
Conditions
Brief summary
Conventional dark-adaptometers are unsuitable as a mass screening tool due to their high cost, lack of easy portability, need of trained staff and a totally dark room to be operated, arbitrary testing procedures, associated time waste in clinic and patient burden to mention a few. Consequently, dark adaptometers are not routinely used as clinical tools for retinal diagnosis and monitoring despite the inherent benefits over other visual electrophysiology equipment such as the ERG system, whose cost and features may often be surplus to optometrists' requirements. This trial will assess the dark-adaptometry testing performance of a novel light-emitting system by generating full dark-adaptation threshold functions in normal adult healthy volunteers. The novel system has been proposed to overcome the issues associated with current instrumentation; it is semi-automatic and easy to use without the need of any skilled operator. It is envisaged that this system could spread the practice of dark-adaptometry testing and its adoption by high-street optometrists. This will allow diagnosing a number of retinal pathologies more quickly and more reliably that, faced with an ageing population, represents a major asset to the Health Community and the NHS. This trial will involve 20 healthy volunteers, distributed in equal number in 2 groups of 18-40 and 50-70 years old, respectively. Proven the good health and eye condition of the participants, one of their eyes will be randomly-allocated and undergo dark-adaptometry testing 3 times on separate days within 3 weeks. Testing will clarify whether by using the novel system it is possible to reproduce state-of-the-art threshold measurements as good or better than those produced by commercially-available dark-adaptometers. Threshold measurements in the elderly will be compared with literature data adjusted to exclude aged crystalline lens and pupillary miosis contributions. Data variability and system usability will be also assessed.
Detailed description
All details elsewhere in the documentation
Interventions
DEVICEDark Adaptometer
Sponsors
University of Liverpool
Study design
Observational model
CASE_ONLY
Time perspective
OTHER
Eligibility
Sex/Gender
ALL
Age
18 Years to 70 Years
Healthy volunteers
Yes
Inclusion criteria
* Refractive error: ≤ ±5 dioptres spherical (myopia/hyperopia) equivalent; ≤ 3 dioptres cylinder (astigmatism) equivalent.
Exclusion criteria
* Subjects not in age range and/or unable to fully understand the informed consent and/or unable to comply with study procedures. * Self-reported history of depression, lack of sleep, psychiatric disorders, or neurological diseases such as Alzheimer's and Parkinson's disease. * Self-reported history of diabetes, stroke, or multiple sclerosis. * Self-reported hypovitaminosis A, alcoholism, liver or intestinal disease, malabsorption, protein calorie malnutrition, or sickle cell anaemia. * Use of psychoactive drugs (including lithium salts for mood stabilisation). * Use of dietary intake of ascorbic acid, vitamin A, B, E or other antioxidant supplements in the last two weeks. * Recurrent practice of activities that expose the retina to ultra-violet radiation such as sailing, fishing, sunbathing or tanning saloons.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Time to Rod-cone Break (RCB) | 40 minutes | RCB (time) values were determined by recording the time required for the participant to observe a light stimulus of a particular luminosity. Participants viewed the light stimuli without their optical correction. These consisted of a white (λpeak = 464 nm; chromaticity coordinates - 2° observer: x = 0.269, y = 0.324) circular test target of 0.255 mm radius, forming a visual angle of around 33°. Participants were asked to press a response button on the handheld joystick when the test target was visible and had 750 ms to make a response after target onset. Target intensity started at approximately 4.865 cd\*m-2. Light stimuli were presented approximately every 2.6 s for a duration of 150 ms each. If the subject under test did not respond to the stimuli, the target intensity remained at the same initial level of approximately 4.865 cd\*m-2 until the subject responded. If the subject reported perception of the light stimulus within the response window, the luminance was reduced by 0 |
| Absolute Threshold | 40 minutes | Rod sensitivity (absolute threshold luminance) values measured in cd\*m-2 |
| Absolute Threshold Time | 40 minutes | Time taken to reach absolution threshold measured in minutes |
Countries
United Kingdom
Participant flow
Pre-assignment details
Use of dietary intake of ascorbic acid, vitamin A, B, E or other antioxidant supplements in the last two weeks prior dark adaptometry was cause of exclusion from the study.
Participants by arm
| Arm | Count |
|---|---|
| Young Adults (18-40) Healthy adult volunteers, aged between 18 and 40, with no prior/current eye problems or family history of genetic eye diseases and good general health. | 10 |
| Older Adults (50-70) Healthy adult volunteers, aged between 50 and 70, with no prior/current eye problems or family history of genetic eye diseases and good general health. | 10 |
| Total | 20 |
Baseline characteristics
| Characteristic | Young Adults (18-40) | Older Adults (50-70) | Total |
|---|---|---|---|
| Age, Categorical <=18 years | 0 Participants | 0 Participants | 0 Participants |
| Age, Categorical >=65 years | 0 Participants | 3 Participants | 3 Participants |
| Age, Categorical Between 18 and 65 years | 10 Participants | 7 Participants | 17 Participants |
| Age, Continuous | 29 years | 58 years | 45 years |
| Ethnicity (NIH/OMB) Hispanic or Latino | 0 Participants | 0 Participants | 0 Participants |
| Ethnicity (NIH/OMB) Not Hispanic or Latino | 10 Participants | 10 Participants | 20 Participants |
| Ethnicity (NIH/OMB) Unknown or Not Reported | 0 Participants | 0 Participants | 0 Participants |
| Sex: Female, Male Female | 7 Participants | 5 Participants | 12 Participants |
| Sex: Female, Male Male | 3 Participants | 5 Participants | 8 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | 0 / 10 | 0 / 10 |
| other Total, other adverse events | 0 / 10 | 0 / 10 |
| serious Total, serious adverse events | 0 / 10 | 0 / 10 |
Outcome results
Primary
Absolute Threshold
Rod sensitivity (absolute threshold luminance) values measured in cd\*m-2
Time frame: 40 minutes
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Young Adults (18-40) | Absolute Threshold | 4.56 cd/m^2 | Standard Deviation 0.23 |
| Older Adults (50-70) | Absolute Threshold | 4.04 cd/m^2 | Standard Deviation 0.65 |
Primary
Absolute Threshold Time
Time taken to reach absolution threshold measured in minutes
Time frame: 40 minutes
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Young Adults (18-40) | Absolute Threshold Time | 28.99 Minutes | Standard Deviation 5.62 |
| Older Adults (50-70) | Absolute Threshold Time | 29.99 Minutes | Standard Deviation 7.01 |
Primary
Time to Rod-cone Break (RCB)
RCB (time) values were determined by recording the time required for the participant to observe a light stimulus of a particular luminosity. Participants viewed the light stimuli without their optical correction. These consisted of a white (λpeak = 464 nm; chromaticity coordinates - 2° observer: x = 0.269, y = 0.324) circular test target of 0.255 mm radius, forming a visual angle of around 33°. Participants were asked to press a response button on the handheld joystick when the test target was visible and had 750 ms to make a response after target onset. Target intensity started at approximately 4.865 cd\*m-2. Light stimuli were presented approximately every 2.6 s for a duration of 150 ms each. If the subject under test did not respond to the stimuli, the target intensity remained at the same initial level of approximately 4.865 cd\*m-2 until the subject responded. If the subject reported perception of the light stimulus within the response window, the luminance was reduced by 0
Time frame: 40 minutes
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Young Adults (18-40) | Time to Rod-cone Break (RCB) | 11.34 Minutes | Standard Deviation 1.37 |
| Older Adults (50-70) | Time to Rod-cone Break (RCB) | 9.98 Minutes | Standard Deviation 3.01 |