Low Vision
Conditions
Keywords
visual acuity, contrast sensitivity, scleral contact lens, artificial iris
Brief summary
Data from 15 healthy subjects will be recorded in two testing sessions spread on two days, using three lens designs (A, B and C). Before the measuring days, each subject will undergo an extra fitting session of a large-diameter scleral contact lens on the dominant eye, assessed by an experienced practitioner. The fitting data will be used to custom-make the three lens designs for each subject, thus ensuring their comfort and safety during the days of the experiments. During the experiment days baseline measurements will be obtained before and after pupil dilation and contact lens wear. During the first testing session data from the lens design A (reference lens without artificial iris) will be recorded. During the second testing session data from the lens designs B and C (lenses with artificial iris with different transmittances) will be recorded. In each testing session, contrast sensitivity and visual acuity will be evaluated and non-invasive imaging measurements will be undertaken (optical coherence tomography and slit lamp). A specific questionnaire will be given to the subject to assess comfort, light sensitivity, the horizontal visual angle and overall experience of the scleral lens and in combination with a pair of sunglasses category 3-4.
Detailed description
First, the participant will be subjected to an RGP scleral contact lens fitting session, then during the second and third visits the participant will be subjected to several non-invasive procedures specific to the study in order to assess contrast sensitivity and visual acuity using the fitted and uniquely fabricated investigational medical devices. The tests will be performed after eye drops are supplied to dilate the pupil of the subjects (eye drops: tropicamide and phenylephrine). Besides the clinical experiments, the participant will be given a specific questionnaire in order to assess comfort, light sensitivity, horizontal visual angle and overall experience of the investigational medical device and in combination with a pair of sunglasses category 3-4. The investigators will document the occurrence of any adverse events and specific side effects during Day 2 and 3 (testing sessions with the investigational devices) in order to effectively assess their safety.
Interventions
DEVICEScleral contact lens without a passive artificial iris
Participants wear a scleral contact lens without a passive artificial iris (Design A) on the dominant eye to perform the baseline visual performance assessment
DEVICEScleral contact lens with a passive artificial iris with low contrast (<1:5)
Participants wear a scleral contact lens with a low contrast (\<1:5) passive artificial iris (Design B) on the dominant eye to perform the baseline visual performance assessment
DEVICEScleral contact lens with a passive artificial iris with high contrast (>1:5)
Participants wear a scleral contact lens with a low contrast (\<1:5) passive artificial iris (Design B) on the dominant eye to perform the baseline visual performance assessment
DRUGTropicamide and phenylephrine
Participants receive pupil dilation eye drops on the dominant eye, after baseline measurement and before wearing the scleral contact lenses (Designs A, B and C)
Sponsors
University Ghent
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 45 Years
Healthy volunteers
Yes
Inclusion criteria
\- Age between 18 and 45 years old
Exclusion criteria
* Iris disorders (i.e. ocular albinism, coloboma, aniridia). * Known disease-related ocular surface problem (i.e. microbial keratitis). * Known ocular pathologies (except refractive disorders). * Coexistent ocular diseases impeding contact lens correction (i.e. glaucoma, previous ocular surgery). * Corneal scarring. * Low corneal endothelial cell count (\< 1500 cells per mm2), with potential of corneal hypoxia-induced corneal edema induced by contact lens wear. * Wearing of contact lenses in the last 24 hours (prior to the interventions).
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Visual acuity assessment and comparison between Designs A, B and C by means of logMAR or equivalent value | 5 months from fitting session | Compare visual acuity values obtained with different designs |
| Contrast sensitivity assessment and comparison between Designs A, B and C by means of threshold percentage or equivalent value | 5 months from fitting session | Compare contrast sensitivity values obtained with different designs |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Contact lens wear comfort, as assessed by subject data from questionnaires Rasch analyzed using a 4-Andrich ration scale model | 5 months from fitting session | The subjective assessment will be carried out by means of questions on 3 content areas: lens comfort (3 questions), visual quality (4 questions) and general satisfaction with the lenses (3 questions). |
| Visual acuity assessment and comparison between Designs B (low contrast) and C (high contrast) by means of logMAR or equivalent value | 5 months from fitting session | Comparing visual acuity between Designs B and C |
| Device safety by comparing eventual adverse events with those found in scleral contact lenses | 5 months from fitting session | Comparing adverse event of similar devices |
| Horizontal visual angle | 5 months from fitting session | Angle at which the volunteer can see his fingers move when extending the arm (same side as dominant eye), 0°=arm extended to the side; 90°=arm straight ahead |
| Contrast sensitivity assessment and comparison between Designs B (low contrast) and C (high contrast) by means of threshold percentage or equivalent value | 5 months from fitting session | Comparing contrast sensitivity between Designs B and C |
| Correct fitting | 5 months from fitting session | Taking and analyzing ocular coherence tomography (OCT) images and slit lamp observations to estimate the clearance |
Countries
Belgium
Outcome results
None listed