Evaluation of the Capacity of a Camera to Identify Signs of Arteriosclerosis in Retinal Arterioles

Preliminary Evaluation of the Capacity of a Metabolic Hyperspectral Retinal Camera (MHRC) to Identify an Arteriosclerosis Spectral Signature in Retinal Arterioles

Arteriosclerosis is a degenerative and dysmetabolic disease of the arterial walls. It is known to be the principal cause of coronary artery disease (CAD). Arteriosclerosis has an impact on the entire vascularization including the microvascularization. The retina is a nervous tissue that is supported by microvascularization. Therefore, systemic diseases that affect the nervous or the cardiovascular system are susceptible to have manifestations in the retina. Retinal signs associated to the risks to develop CAD (qualitative appreciation; diameter and appearance of arterioles) have been suggested. A quantitative approach would strengthen the interpretation of these evaluations.

The Metabolic Hyperspectral Retinal Camera (MHRC) - the experimental instrument - has the capacity to identify and quantify a variety of biomolecules specific to the retina and the optic nerve.

The purpose of this pilot study is to determine if the MHRC has the capacity to detect a specific hyperspectral signature in the retinal arterioles of subjects suffering from arteriosclerosis.

In this pilot study, the main goal is to evaluate the capacity of the Metabolic Hyperspectral Retinal Camera (MHRC) - the experimental instrument - to identify the presence of a specific hyperspectral signature in the retinal arterioles of subjects suffering from arteriosclerosis while this signature should not be present in the retinal arterioles of control subjects considered healthy and without arteriosclerosis risk factors. The study is open, non-controlled and without randomization or placebo.

30 subjects of each group will be enrolled in the study for a total of 60 subjects. Recruitment will take place at the Montreal Heart Institute (Montreal, Quebec, Canada) and will be led by the research team of the Principal Investigator. Specific inclusion/exclusion criteria will differentiate subjects in each group. Once subjects fitting the inclusion/exclusion criteria will be identified, they will be enrolled and asked to sign the informed consent form approved by the Research Ethics and New Technology Development Committee (Montreal Heart Institute).

Following this step, an ophthalmic examination will be performed. During this examination, both eyes will be evaluated in order to detect the presence of eye pathologies (advanced cataracts, venous occlusion, age-related macular degeneration or glaucoma) that could interfere with the analysis of the MHRC optical imaging results. The ophthalmic examination consists first of a slit-lamp evaluation and secondly of an optic coherence tomography (OCT) plus a color image of the fundus (standard instruments commonly used in ophthalmology clinics) following the instillation of eye drops to dilate the pupils. The whole examination should last 45 minutes (it takes 15 to 20 minutes for the pupil to be sufficiently dilated to carry out the examinations). If the ophthalmic examination does not reveal any of the exclusion criteria, in the next minutes, the subject will be asked to undergo the baseline MHRC examination. This baseline imaging session will last a maximum of 15 minutes.

All data according to the light signal spectrum will be analyzed subsequently. Only depersonalized data, identified solely by the subject number, will be used by the investigators.

Risks associated to the subject's participation in this research project have been evaluated. Pupil dilation will be necessary to obtain quality images of the retina using conventional imaging techniques (OCT and fundus) and with the MHRC. The subject's pupils will remain dilated for 4 to 6 hours afterward, which may cause significant glare in areas where light is strong.. The MHRC is a research instrument which images the retina non-invasively and Health Canada authorization has been obtained for its use in the context of this study. The only foreseeable harm connected to its use is discomfort connected to the injection of light into the eye. The power of the monochromatic light source has been calculated to be well below the recommended exposure limits.. Very rigorous verifications were made according to the parameters fixed by the "American National Standard for safe use of laser" (ANSI 136.1) for laser radiation exposure.

Finally, all conflicts of interested are declared in the protocol and the informed consent form. Measures are in place to mitigate them in order to maintain research and data analysis integrity.

Inclusion Criteria:

Subjects suffering from arteriosclerosis:

1. myocardial infarction
2. coronary angiography showing at least one coronary stenosis (more than 50%)
3. and/or coronary angioplasty
4. and/or coronary bypass.

Healthy control subjects:

1. absence of a medical history of cardiovascular disease
2. absence of medical history of cerebrovascular disease
3. absence of a medical history of peripheral arterial disease

Exclusion Criteria:

Healthy control subjects:

1. myocardial infarction or angina
2. known coronary stenosis
3. coronary angioplasty history or coronary bypass surgery
4. stroke or transient ischemic attack history
5. peripheral arterial disease history
6. active smoking or history smoking in the past 5 years
7. diabetes mellitus
8. familial hypercholesterolemia
9. poorly controlled hypertension (systolic blood pressure ≥150 mm Hg)

All subjects:

1. medium or high opacity of the lens (which interferes with the MHRC imaging)
2. bleeding in the vitreous (which interfere with MHRC imaging)
3. presence of venous occlusion, age-related macular degeneration or glaucoma
4. pupillary dilation inadequate or contra-indicated
5. deficient visual fixation
6. refractive error outside of the range -9 to +9
7. inability to obtain satisfactory images with the MHRC