Vision Science and Eye

Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment visual impairment may cause the individual difficulties with normal daily tasks including reading and walking. Low vision is a functional definition of visual impairment that is chronic, uncorrectable with treatment or correctable lenses, and impacts daily living. As such low vision can be used as a disability metric and varies based on an individual’s experience, environmental demands, accommodations, and access to services.

Neuro diagnostic imaging and other techniques, examination of the afferent visual sensory system is still the core of the neuro-ophthalmologic examination. A thorough refraction is an essential part of all clinical neuro ophthalmologic examinations. Confrontation visual fields should be part of every afferent system examination. The relationship between the physical properties of light and perceptual and behavioural responses is known as visual psychophysics, which serves as the foundation for the clinical assessment of visual function. The determination of whether a patient’s visual field improves worsens, or remains stable over time is the most difficult aspect of visual field interpretation. Many attempts have been made to investigate visual field function using evoked potentials to visual stimuli.

The hypothesis that there is a correlation between vision and cognition is based on the impact of vision on mentally stimulating activities. Loss of vision hinders the performance of these tasks (e.g., reading, socializing) and may result in behavioural changes and cognitive decline. Deterioration in vision reportedly reduces physical, mental, and psychosocial activities which can lead to a poor cognitive state.

Visual Neuroscience is a branch of neuroscience that focuses on the visual system of the human body, mainly located in the brain's visual cortex. The main goal of visual neuroscience is to understand how neural activity results in visual perception, as well as behaviours dependent on vision. In the past, visual neuroscience has focused primarily on how the brain (and in particular the Visual Cortex) responds to light rays projected from static images and onto the retina. While this provides a reasonable explanation for the visual perception of a static image, it does not provide an accurate explanation for how we perceive the world as it really is, an ever-changing, and ever-moving 3-D environment.

Keratoconus occurs when your cornea the clear, dome-shaped front surface of your eye thins and gradually bulges outward into a cone shape. A cone-shaped cornea causes blurred vision and may cause sensitivity to light and glare. Keratoconus usually affects both eyes, though it often affects one eye more than the other.

Dry eye is a condition in which a person doesn't have enough quality tears to lubricate and nourish the eye. Tears are necessary for maintaining the health of the front surface of the eye and for providing clear vision. Dry eye is a common and often chronic problem, particularly in older adults. With each blink of the eyelids, tears spread across the front surface of the eye, known as the cornea. Tears provide lubrication, reduce the risk of eye infection, wash away foreign matter in the eye and keep the surface of the eyes smooth and clear. Excess tears in the eyes flow into small drainage ducts in the inner corners of the eyelids, which drain into the back of the nose. Dry eyes can occur when tear production and drainage is not in balance.

Low vision is the loss of sight that is not correctible with prescription eyeglasses, contact lenses or surgery. This type of vision loss does not include complete blindness, because there is still some sight and it can sometimes be improved with the use of visual aids.

Binocular vision is defined and the motor system and sensory system underlying binocular vision are summarised. A simple model of binocular vision is presented and terminology defined. The prevalence of binocular vision anomalies is reviewed, noting that primary eye care practitioners can expect to find binocular vision anomalies in at least one in five patients. The classification of binocular vision anomalies is described, noting that heterophoria can be classified according to the direction of deviation, fixation distance, and compensation. Strabismus can be classified according to constancy, direction of deviation, eye preference, and accommodative state.

Glaucoma is a group of eye conditions that damage the optic nerve, the health of which is vital for good vision. This damage is often caused by an abnormally high pressure in your eye. Glaucoma is one of the leading causes of blindness for people over the age of 60. It can occur at any age but is more common in older adults.

Visual perception is the ability to perceive our surroundings through the light that enters our eyes. The visual perception of colors, patterns, and structures has been of particular interest in relation to graphical user interfaces (GUIs) because these are perceived exclusively through vision. An understanding of visual perception therefore enables designers to create more effective user interfaces.

Color vision deficiency is the inability to distinguish certain shades of color. The term "color blindness" is also used to describe this visual condition, but very few people are completely color blind. Color vision is possible due to photoreceptors in the retina of the eye known as cones. These cones have light-sensitive pigments that enable us to recognize color. Found in the macula (the central part of the retina), each cone is sensitive to either red, green or blue light (long, medium or short wavelengths). The cones recognize these lights based on their wavelengths.  Normally, the pigments inside the cones register different colors and send that information through the optic nerve to the brain. This enables us to distinguish countless shades of color. But if the cones don't have one or more light-sensitive pigments, they will be unable to see all colors.

Ocular oncology involves the study and treatment of tumors that occur in or around the eye. These tumors can range from harmless to potentially life-threatening, and may cause vision loss or loss of the eye itself. Due to the complex nature of ocular oncology, our faculty includes experts in cornea, ophthalmic plastic surgery, pathology, and retina. Mass. Eye and Ear researchers and clinician scientists have experience with a range of conditions, including ocular surface tumors, uveal melanoma, orbital tumors and inflammation, and retinoblastoma.

Vitreo-retinal diseases are conditions that affect structures in the eye called the retina and the vitreous. The retina is the light-sensitive layer in the back of the eye that focuses images and transmits that information to the brain via the optic nerve. The vitreous is a clear gel that fills the space between the lens (in the front of the eye) and the retina.

Oculoplastic and orbital surgery is plastic surgery focused on the structures surrounding the eye, including the eyelids, orbit (bones of the eye socket), lacrimal system (tear duct system), forehead, and mid face area. Because surgery in these areas can affect vision, ophthalmic plastic surgeons are best qualified to perform this delicate surgery.

Retinal detachment describes an emergency situation in which a thin layer of tissue (the retina) at the back of the eye pulls away from its normal position. Retinal detachment separates the retinal cells from the layer of blood vessels that provides oxygen and nourishment. The longer retinal detachment goes untreated, the greater your risk of permanent vision loss in the affected eye.

Blepharitis is inflammation of the eyelids. Blepharitis usually affects both eyes along the edges of the eyelids. Blepharitis commonly occurs when tiny oil glands near the base of the eyelashes become clogged, causing irritation and redness. Several diseases and conditions can cause blepharitis. Blepharitis is often a chronic condition that's difficult to treat. Blepharitis can be uncomfortable and unsightly. But it usually doesn't cause permanent damage to your eyesight, and it's not contagious.

Strabismus (crossed eyes) is a condition in which the eyes do not line up with one another. In other words, one eye is turned in a direction that is different from the other eye. Under normal conditions, the six muscles that control eye movement work together and point both eyes at the same direction. Patients with strabismus have problems with the control of eye movement and cannot keep normal ocular alignment (eye position).