Welcome to the Eye Movement and Vision Neuroscience Laboratory. We are located in Toronto, Ontario, Canada, at The Hospital for Sick Children and Toronto Western Hospital, and affiliated with the University of Toronto in Canada.
We conduct scientific investigations of visual disorders and their impact on brain function and behaviour with the aim of improving patient quality of life. We foster a multidisciplinary collaborative environment, and provide opportunities for educational advancement and personal growth. Our current goal is to understand the brain mechanisms that cause amblyopia (lazy eye), strabismus (crossed or walled eyes), and abnormal eye movements, as well as how to treat these diseases. We use sophisticated techniques to measure visual functions, eye movements, and brain activities to investigate how the normal brain functions, and how these brain functions change in the diseased states.
Amblyopia, also called lazy eye, is a decrease in vision in one or both eyes as a result of reduced visual input to the brain in early childhood. It is most commonly caused by a difference in glasses prescription between the eyes, or eye misalignment (turned or wandering eye), or from any eye diseases such as congenital cataract or ptosis. Children below 9 years of age have the highest risk of developing amblyopia. Vision screening by family doctors and pediatricians are very important. Depending on the causes, treatment for amblyopia may include glasses, patching, eye drops, and/or eye muscle surgery. Read more...
Strabismus, also called wandering eye or turned eye, is a condition when the eyes are not looking straight. The eye can be turned in, out, up or down. If one eye is constantly turned, children will be at increased risk of developing amblyopia (lazy eye), while adults will complain of double vision. Strabismus is most commonly caused by imbalance of eye muscles in children who are otherwise healthy. However, children with Down’s syndrome, cerebral palsy, and brain tumor are more likely to develop strabismus. In adults, common causes of strabismus include stroke, head trauma, brain tumor, and thyroid eye disease. Depending on the causes, treatment may include glasses, prism, and/or eye muscle surgery. Read more...
Glaucoma is a group of eye diseases which result in damage to the optic nerve resulting in vision loss. A major risk factor is increased pressure in the eye. Glaucoma can damage vision permanently in the affected eye, first by decreasing peripheral vision (reducing the visual field), and then potentially leading to blindness if not treated. Glaucoma is known as the "silent thief of vision" because the vision loss often occurs gradually, and symptoms only manifest when the disease is already advanced significantly. Worldwide, glaucoma is the second-leading cause of blindness after cataracts. Automated perimetry is the clinical standard for detecting and monitoring glaucoma progression, but it is subjective and difficult to perform in advanced disease.
In our lab we are developing chromatic pupillometry as a potential new non-invasive objective assessment technique for glaucoma. It is a promising new technique that uses light stimulation with specific frequencies and intensities to assess the integrity of the early visual pathways. We have several student projects employing chromatic pupillometry to detect and monitor disease progression in glaucoma in our lab at Toronto Western Hospital.
Mild Traumatic Brain Injury (mTBI)
Mild Traumatic Brain Injury is the most prevalent traumatic brain injury. MTBI is a head injury resulting in a temporary loss of brain function. It can cause a variety of physical, cognitive, and emotional symptoms, which may not be recognized if subtle. Symptoms usually resolve within three weeks, though they may persist or complications may occur, sometimes leading to Post-Concussion Syndrome. Individuals who have had one mTBI appear more susceptible to further mTBI, particularly if the new injury occurs before symptoms from the previous injury have resolved completely. There can also be a negative progressive process, in which subsequent lesser impacts cause similar symptom severity. Repeated concussions may increase the risk for dementia, Parkinson's disease, and/or depression in later life. The incidence of concussion is estimated to be approximately 6 per 1,000 people.
We have new student projects on mTBI, including 1) the potential role of the recently discovered melanopsin-driven intrinsically photosensitive retinal ganglion cell (ipRGC) light irradiance detection pathway in photophobia subsequent to mTBI using chromatic pupillometry; 2) the putative role of the melanopsin pathway in sleep disturbance after mTBI, which will also be investigated with chromatic pupillometry; 3) the role of vergence eye movement and vergence-saccade interaction dysfunction subsequent to mTBI, to be tested using objective non-invasive eye movement recordings; 4) the role of radial flow vergence dysfunction in spatial disorientation subsequent to mTBI, to be studied using stereoscopic stimulation and objective eye movement recordings; and 5) the impact of mTBI on sensorimotor adaptation, as evidenced by changes in the patient’s ability to adapt to visually-displacing prisms.
Myopia, which is also known as short-sightedness or near-sightedness, is an eye condition where light entering the eye does not focus on the retina, but in front of it instead. This causes the image formed on the retina when looking at a distant object to be out of focus. It does not affect focus when looking at a close object. High myopia is defined as a refractive error of -6 diopters or more. People with high myopia are more likely to experience retinal detachments and glaucoma. Eye growth is regulated by the retinal circadian rhythm, which in turn is mediated by the local release of dopamine in the retina. There is converging evidence that both retinal circadian rhythm and dopamine release are regulated to some extent by the recently discovered melanopsin-driven intrinsically photosensitive retinal ganglion cell (ipRGC) light irradiance detection pathway, suggesting that altered ipRGC output may contribute to the development of high myopia in genetically predisposed individuals.
We have available student projects using chromatic pupillometry to quantify the changes in ipRGC output in people with high myopia, which may be manifest as changes in the post-illumination pupil response (PIPR). These experiments will be run at our labs at Sickkids and Toronto Western Hospital.
Photophobia in Migraine
Migraine is a primary headache disorder characterized by recurrent headaches that are moderate to severe. Typically, the headaches affects one half of the head, are pulsating in nature, and last from two to 72 hours. The pain is generally made worse by physical activity. Associated symptoms may include nausea, vomiting, and hypersensitivity to sound, smell, or light (photophobia). Migraines are thought to be due to a mix of environmental and genetic factors. Globally, approximately 15% of people are affected by migraines.
We have new student projects examining the putative role of the recently discovered melanopsin-driven intrinsically photosensitive retinal ganglion cell (ipRGC) mediated light irradiance detection pathway in migraine photophobia. These projects will use chromatic pupillometry to quantify the differences in melanopsin pathway function in patients with persistent photophobia between their migraine episodes.
Infantile esotropia is an inward turning of one or both eyes that begins within the first 6 months of life. If one eye is constantly turned, children will be at increased risk of developing amblyopia (lazy eye). Most children with infantile esotropia are usually otherwise healthy. However, children who are born prematurely, those with hydrocephalus (a buildup of fluid inside the skull that leads to brain swelling), seizure disorders, development delay, and intraventricular hemorrhage (bleeding into the fluid-filled areas [ventricles] inside the brain) are more likely to develop infantile esotropia. While some children may respond to glasses, most will need eye muscle surgery before 2 years of age to improve long-term visual outcomes. Read more...
Fourth Nerve Palsy
Fourth nerve palsy, also known as trochlear nerve or superior oblique palsy, is caused by weakness of the fourth nerve that comes out of the brain. Double vision is a major symptom which may be vertical (one image on top of the other), diagonal (one image on top of the other as well as side-by-side) and less often rotated (or twisted). An abnormal head tilt is also common. Fourth nerve palsy is commonly congenital (although it may only cause symptoms later in life), but it can also be caused by head trauma, stroke, and brain tumor. Treatment may include patching, prism, and/or eye muscle surgery. Read more...
A vertical eye misalignment with one eye higher than the other. Patients typically complain of double vision and may also have an involuntary abnormal head tilt. It is usually caused by damages in the brain or inner ear, as a result of a stroke, tumor, trauma or multiple sclerosis. Treatment is directed at treating the underlying cause. Eye muscle surgery is sometimes required to correct for double vision.