None listed
Conditions
Brief summary
Retinal ischemia plays a significant role in the pathogenesis of age-related macular degeneration (AMD) and diabetic retinopathy (DR)- two of the most common sight-threatening diseases in the developed world. Treatment options for these conditions are limited and there is a significant interest in developing methods for increasing ocular blood flow so as to reduced ischemia and inhibit disease progression. In healthy eyes, 70% of blood flow passes through the ocular choroid but in both AMD and DR the thickness of the choroid is significantly reduced. Interestingly, the choroid has a remarkable capacity to increase its thickness when exposed to short-term myopic defocus- a condition in which the image is formed in front of the retina. Because the choroid is largely a vascular tissue, this rapid and transient choroidal response to defocus is presumably driven by changes in blood flow. This project aims to translate this finding into a clinical application, and use contact lens-induced retinal defocus as a potential new treatment to increase choroidal thickness and blood flow in patients with AMD and DR so as to reduce ischemia and improve visual outcomes. The primary purpose of the study is to investigate whether the application of defocussing contact lens enhances blood flow in the posterior eye. We hypothesize that a short-term wear of defocussing contact lens, known to produce thickness changes in the posterior eye, results in an increase in blood flow.
Interventions
Name: Defocussing contact lens
Rationale: A defocussing contact lens (that would produce 2.00D myopic defocus) will be applied to the experimental eye for approximately 40 minutes prior to the MRI scan. Previous studies have shown that the application of contact lens inducing myopic defocus causes an increase in choroidal thickness, which is maximum at this time point.
Materials: CooperVision 54% 1-day Silicone Hydrogel; https://coopervision.com/)
Procedures: The trial will consist of two visits
Name: Defocussing contact lens Rationale: A defocussing contact lens (that would produce 2.00D myopic defocus) will be applied to the experimental eye for approximately 40 minutes prior to the MRI scan. Previous studies have shown that the application of contact lens inducing myopic defocus causes an increase in choroidal thickness, which is maximum at this time point. Materials: CooperVision 54% 1-day Silicone Hydrogel; https://coopervision.com/) Procedures: The trial will consist of two visits for each participant. In one of the visits, both eyes will be fully corrected with contact lenses of appropriate power, whereas, in the other, one randomly chosen eye (experimental eye) will be subjected to myopic defocus. The order of the experimental condition (i.e. defocus/no defocus) will be randomized between the two visits. Following the application of contact lens for 40 minutes, MRI will be performed in order to obtain measures of choroidal blood flow in both eyes. Personnel: A research optometrist with an optometry qualification (Doctor of Optometry degree) will be responsible for patient recruitment, eye examination, and providing intervention. MRI scans will be performed by MRI technologists experienced with perfusion MRI. Mode: Intervention (+2.00D defocussing contact lens) will be given individually to the research participants only once on the study visit Where: The trial will be conducted in School of Optometry and Vision Science and the Centre for Advanced MRI at the University of Auckland
Sponsors
The University of Auckland
Study design
Allocation
Non-randomised trial
Intervention model
Single group
Primary purpose
Treatment
Masking
Open (masking not used)
Eligibility
Sex/Gender
All
Age
18 Years to 35 Years
Healthy volunteers
Yes
Inclusion criteria
18-35 years old healthy subjects normal or corrected to normal vision with glasses/contact lenses
Exclusion criteria
Refractive error greater than -3.00DS or +3.00D spherical equivalent with the difference between eyes more than 1.00D; astigmatism greater than 1.00D; amblyopia, any underlying ocular pathology or previous history of ocular surgery; and previous history of myopia control treatment (such as Ortho-K and atropine).
Outcome results
None listed