Our Optometry Definitions section defines and explains the optometry related terms used on our website. Browse through the various definitions and explanations to familiarize yourself with those terms and get a better understanding of what optometry is.
Optometry
Optometry is the health care profession concerned with examination, diagnosis, and treatment of the eyes and related structures, and with determination and correction of vision problems using lenses and other optical aids.
Sub-specialities include cornea and contact lenses, family practice optometry, geriatric optometry, low vision rehabilitation, ocular disease, pediatric optometry, primary care, refractive and ocular surgery, vision therapy and rehabilitation.
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Optometrist
An optometrist is an eye care professional who is a primary care practitioner for most vision and ocular health concerns. Optometrists are trained to diagnose, manage, and treat a multitude of visual and ocular health-related concerns, including, but not limited to, fitting and prescribing glasses and contact lenses, diagnosing and treating (excluding surgery) muscular abnormalities, treating minor ocular injuries, diagnosing and treating diseases such as glaucoma and diagnosing others such as diabetic retinopathy. In Oklahoma, optometrists perform certain laser procedures.
Optometrists are experts in determining one's refractive error and prescribing the appropriate correction. In the United States they perform comprehensive eye exams and diagnose and treat many of the most common eye disorders whether they be visual or physical. As with all medical practitioners, referrals are made when more specialized care is needed.
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Optician
An optician is an eye care professional who provides lenses for the correction of vision defects. The lenses may be contact lenses, or held in a frame in front of the eye, rarely as a monocle or most frequently as a pair of glasses, also known as spectacles or eyeglasses. The main optical properties of the lenses are specified from a refraction prescription supplied by a person qualified to measure visual defects and write an appropriate corrective prescription. The licensing and nomenclature of such persons varies from country to country.
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Lenses
A lens is a device that causes light to either converge and concentrate or to diverge, usually formed from a piece of shaped glass. One important use of lenses is as a prosthetic for the correction of visual impairments such as myopia, hyperopia, presbyopia, and astigmatism. Such prosthetics are in the form corrective lens, contact lens, eyeglasses.
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Vision Insurance
Vision insurance is a form of insurance that provides coverage for the services rendered by an eye care professional such as an optometrist. There a many forms of vision insurance with the most widely known method being Vision Service Plan (VSP). The typical vision insurance plan provides yearly coverage for eye exams and some compensation for eyeglasses, sunglasses and contact lenses.
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Vision Service Plan (VSP)
Vision Service Plan, commonly referred to as VSP, is the nation’s largest provider of eyecare and vision insurance coverage. One in seven Americans rely on VSP for eyecare wellness. For close to half a century, VSP has been a trusted advisor in eyecare wellness benefits.
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Eyeglasses
Glasses, spectacles, or eyeglasses are frames bearing lenses worn in front of the human eyes, sometimes for purely aesthetic reasons but normally for vision correction or eye protection. Special glasses are used for viewing three-dimensional images or experiencing virtual reality.
Modern glasses are typically supported by pads on the bridge of the nose and by temples placed over the ears. Historical types include the pince-nez, monocle, and lorgnette.
Glasses are occasionally called eyeglasses in North American English, occasionally spectacles in British English, and (rarely) frames or lenses. Spectacles is often shortened to specs.
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Sunglasses
Sunglasses are a visual aid, variously termed spectacles or glasses, which feature lenses that are coloured or darkened to screen out strong light from the eyes.
Many people find direct sunlight too bright to be comfortable, especially when reading from paper on which the sun directly shines. In outdoor activities like skiing and flying, the eye can receive more light than usual. It has been recommended to wear these kind of glasses on sunny days to protect the eyes from ultraviolet radiation, which can lead to the development of a cataract. Sunglasses have also been associated with celebrities and film actors primarily due to the desire to mask identity, but in part due to the lighting involved in production being typically stronger than natural light and uncomfortable to the naked eye.
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Glaucoma
Glaucoma is a group of diseases of the optic nerve involving loss of retinal ganglion cells in a characteristic pattern of optic neuropathy. Although raised intraocular pressure is a significant risk factor for developing glaucoma, there is no set threshold for intraocular pressure that causes glaucoma. One person may develop nerve damage at a relatively low pressure, while another person may have high eye pressures for years and yet never develop damage. Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness.
Also see: Glaucoma: Types, Symptoms and Treatment
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Glaucoma Valves
Glaucoma valves reduce the intraocular pressure (IOP) of the eye by directing the outflow of the aqueous humor through a shunt device. The IOP generally decreases from around 33 to 10 mmHg by removing on average 2.75 microliters/min. The shunt device channels the aqueous humor in an alternate pathway through a small tube into an outlet chamber. The aqueous forms a bleb and is removed through intercellular spaces and the lymphatic system. These devices create a pathway that completely bypasses the body’s natural drainage device, the trabecular meshwork, for the treatment of glaucoma.
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Ocular Hypertension
Ocular hypertension (OHT) is intraocular pressure higher than normal in the absence of optic nerve damage or visual field loss.
Current consensus in ophthalmology defines normal introcular pressure (IOP) as that between 10 mmHg and 21 mmHg. Elevated IOP is the most important risk factor for glaucoma, so those with ocular hypertension are frequently considered to have a greater chance of developing the condition.
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Depth Perception
Depth perception is the visual ability to perceive the world in three dimensions. It is a trait common to many higher animals. Depth perception allows the beholder to accurately gauge the distance to an object.
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Color Vision
Color vision is the capacity of an organism or machine to distinguish objects based on the wavelength (or frequency) of the light they reflect or emit, and arises through an appreciation of the distribution of light intensity over the visible spectrum (450-700 nm). A 'red' apple does not emit red light. Rather, it simply absorbs all the frequencies of light shining on it except the frequencies we call red, which are reflected. An apple is perceived to be red only because the human eye can distinguish between different wavelengths. Three things are needed to see color: a light source, a detector (e.g. the eye) and a sample to view.
The advantage of color, which is a quality constructed by the visual brain and not a property of objects as such, is the better discrimination of surfaces allowed by this aspect of visual processing.
In order for animals to respond accurately to their environments, their visual systems need to correctly interpret the form of objects around them. A major component of this is perception of colors.
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Diabetic Retinopathy
Diabetic retinopathy is retinopathy (damage to the retina) caused by complications of diabetes mellitus, which could eventually lead to blindness. It is an ocular manifestation of systemic disease which affects up to 80% of all diabetics who have had diabetes for 15 years or more [citation]. Despite these intimidating statistics, research indicates that at least 90% of these new cases could be reduced if there was proper and vigilant treatment and monitoring of the eyes [citation].
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Visual Perception
Visual perception is one of the senses, consisting of the ability to detect light and interpret (see) it. The resulting perception is known as eyesight, sight or naked eye vision. Vision has a specific sensory system, the visual system.
There is disagreement as to whether or not this constitutes one, two or even three distinct senses. Some people make a distinction between the "black and white" vision system and the color one, pointing out that they use completely different sets of photoreceptors (respectively rod cells and cone cells). Some argue that perception of depth also constitutes a distinct sense, but others persuasively argue that depth is just one of many pieces of information extracted from several visual cues (it is based on the stereoscopic effect of having two eyes, the relative size of objects, motion, etc). Many people are also able to perceive the polarization of light.
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Polarization
In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves such as light, which describes the direction of their transverse electric field. More generally, the polarization of a transverse wave describes the direction of oscillation in the plane perpendicular to the direction of travel. Longitudinal waves such as sound waves do not exhibit polarization, because for these waves the direction of oscillation is along the direction of travel.
Light reflected by shiny transparent materials is partly or fully polarized, except when the light is normal to the surface. A polarizing filter, such as a pair of polarizing sunglasses, can be used to observe this by rotating the filter while looking through. At certain angles, the reflected light will be reduced or eliminated. Polarizing filters remove light polarized at 90° to the filter's polarization axis. If two polarizers are placed atop one another at 90° angles to one another, no light passes through..
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