Keratoconus
Keratoconus occurs when the central part of the cornea (the clear front surface of your eye) becomes thin. As the cornea thins, it becomes cone shaped or distorted and your vision gradually deteriorates.
The cause of keratoconus is not yet known, although excessive eye rubbing and genetics appear to be involved. It can be associated with conditions such as asthma, eczema, Down's syndrome, Marfan's syndrome and mitral valve prolapse.
Keratoconus occurs equally in men and women, in about 1 out of every 2000 people.
The initial symptoms include blurry or distorted vision that can often be corrected with spectacles. As the condition progresses rigid contact lenses are usually required to allow the person to see clearly.
Treatment: In the early stages of the condition, spectacles are adequate in correcting the vision. As the condition advances, the cornea becomes highly irregular and rigid contact lenses are then required to provide optimal visual acuity. In about a sixth of cases, the keratoconus progresses to the stage where corneal transplantation is required. New techniques such as collagen cross-linking are currently being trailed, providing exciting opportunities for the future treatment of keratoconus.
More information:
All about vision - Keratoconus
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Cataract
A cataract is a clouding of the eye’s natural lens. As light passes through the lens it becomes scattered thereby reducing vision.
Cataracts usually develop as part of the ageing process. However, they can occur earlier in cases of various medical conditions such as diabetes, injury to the eye, certain medications such as steroids, malnutrition, or prolonged, unprotected exposure to sunlight.
Over half of all people over the age of 65 have a cataract. Most common symptoms include blurry vision, colours appear faded, sensitivity to glare, and poor night vision. As the condition progresses many experience haloes around bright lights, double vision, or very poor vision in low lighting conditions.
Surgery is the only way to remove the cataract. The eye’s natural lens is removed and replaced with a new plastic version. With the advances in modern surgery the procedure usually takes about half an hour and many people only require reading glasses afterwards.
More information:
Optometrists Association Australia - eye diseases
University of Melbourne - Ophthalmology Dept
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Ultraviolet light and the eye
What is UV light?
Visible Light is electromagnetic radiation in the range of ~ 400-700 nm. A nanometer is a billionth of a meter. UV light is invisible and has a shorter wavelength of 10-400 nm. UV light is usually categorised as UVA (320-380 nm), UVB (290-320 nm) and UVC (180-290 nm).
Where is UV light found?
UV light is found in sunlight and is also emitted by specialised lights.
What are the benefits of UV light?
UV light helps us produce Vitamin D in the skin (required for normal functioning of the nervous system, for bone growth, insulin secretion, immunity and blood pressure), it increases melatonin production which gives us the skin tan in summer, and is used in the treatment of various skin conditions such as psoriasis and vitiligo.
What are the detriments of UV light?
UV light can damage the eyes in several ways, affecting the cornea, the lens and the retina. Well-known effects of excessive UV exposure to the eye include “welder’s flash” and “snow-blindness”. Long term effects include cataract, pterygium formation & eyelid cancers.
How to prevent UV damage?
Firstly, avoid excessive exposure. If you must be outside wear a hat, sunglasses and sunscreen protection. The colour of the sunglasses does not indicate the level of UV protection. Many clear lenses can offer almost 100% UV protection if they have special UV filters built into the lenses. (see our lens section on more information about lens coatings and their benefits)
More information:
Optometrists Association Australia - UV
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Colour Vision
Colour vision is the ability to distinguish objects based on their differing wavelengths of light that they reflect. Visible light occurs from around 400-700 nm. White light can be split into its component colours by passing through a prism or after a rainy day observing the rainbow. Each colour has a particular frequency that determines what we perceive or see. Red light has a frequency of about 650 nm, green light around 550 nm and blue light around 450 nm.
The human visual system has 2 types of photoreceptors to detect light, the cones (used to detect colour) and the rods (used to detect brightness). The cones are further subdivided into 3 types. These cells are part of a complex system, which includes many other cells, and the occipital lobe (or visual centre of the brain) to enable us to perceive colour. We are more sensitive to green-yellow light than blue or red light. Under low light levels, we are unable to detect colour effectively. The human eyes can distinguish millions of different colours. However, some people are “colour blind”. Most colour blindness has a genetic cause although damage to the retina, nerves or brain can also affect colour vision.
How common is colour blindness?
About 1 in 200 females and 1 in 12 males have a colour vision defect. There are several types of colour vision defects with the most common being deuteranopia (absence of green photoreceptors), which affects ones ability to discriminate red-green colours.
Most people find out they have a colour vision defect when they have their eyes examined using the Ishihara colour vision test. In some states and some professions (e.g. Defence forces) having a colour vision defect can limit the type of jobs one can do e.g. drive taxis or signalling. If you wish to apply for such positions and you are unsure please contact our offices for a consultation.
Most genetic types of colour blindness cannot be treated. Some forms that are due to nerve or retinal damage may be reversed if the condition causing the damage is removed and the tissue is repaired.
More information:
Health on the Net Foundation
Vischeck
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Behavioural Optometry
What is Behavioural Optometry?
Behavioural Optometry applies a holistic viewpoint to an eye examination and assesses clarity of vision, efficiency of vision, visual information processing and eye health taking into account the patient’s visual system as part of the whole body rather than one of the individual senses. It expands the role of optometry in areas such as binocular visual dysfunction, learning difficulties, brain injuries and sports vision.
Who needs a Behavioural Optometrist?
Virtually all of us can benefit from a behavioural optometric examination. However, for all children, as well as adults performing below their potential or having learning difficulties, for those who participate in sports and want improved performance, for anyone using a computer or has a visually demanding occupation, and for those who suffer from tired eyes or eye strain without any other apparent medical problem, it may be worthwhile having a behavioural optometric assessment.
How long does a behavioural assessment take?
This depends on the reason for your visit with the optometrist. A visual information processing assessment for example, takes approximately 1 hour. The optometrist will discuss the time needed for each assessment.
Are there additional costs associated with seeing a behavioural optometrist?
Given that behavioural optometrists do additional testing, some of which is not covered by Medicare, there may be additional costs involved. The optometrist will discuss these before any examinations or therapy is instigated.
If treatment is required, what is involved?
Treatment options are variable and depend on the finding of the examination. Some treatments include, various types of eye exercises, glasses with prism, coloured glasses, referral to a GP or other health professional or simply, advise on visual “hygiene” to improve posture, reading habits and reduce the possibility of eye problems developing.
Are special qualifications required to be a behavioural optometrist?
Behavioural optometrists are usually members of Fellows of ACBO (Australian College of Behavioural Optometry). To maintain membership the optometrist is required to maintain a certain level of continuing education in the area of behavioural optometry.
More information:
Australasian College of Behavioural Optometry
Children’s Vision
Optometric Extension Program
College of Optometrists in Vision Development
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Vision Therapy
What is vision therapy?
Vision therapy is a series of activities designed for each individual to assist their visual system in performing to its maximum potential.
What can it be used to treat?
Vision therapy can be used to treat conditions such as: Lazy eye (amblyopia), turned eyes (strabismus), poor eye movements, poor focussing skills, brain injury & stroke, improved visual hand-eye coordination and peripheral awareness required in sports, various developmental, perceptual and learning deficits such as spatial skills (reversals & poor body awareness), sequential memory difficulties, poor visual-auditory integration & visual-motor integration (seen with poor hand writing).
What are the costs involved?
The costs for vision therapy depend on the condition being treated, the length of time required for treatment and whether any equipment or software are required during training. At Kosmac & Clemens Optometrists we offer 3 levels of visual training to cover all budgets and time frames. Vision therapy is not covered by Medicare but you may be able to claim through your Private Health Fund. You can discuss this further with our optometrist or vision therapist.
How long does it take?
Vision therapy can take anywhere from a few weeks to many months. The length of time depends on the condition being treated, the severity of the condition and the level of vision training that the patient performs.
More information:
Optometrists Association Australia - vision training
Vision therapy
Australasian College of Behavioural Optometry - vision therapy
College of Optometrists in Vision Development - care
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Examinations
What does an optometrist check for during an examination?
An eye examination involves the use of several tests, usually performed by an optometrist or ophthalmologist, to assess vision. Comprehensive eyes tests usually involve the following: a thorough case history, an assessment of visual acuity, accommodation (focussing), vergence (eye teaming), stereopsis (depth perception), colour vision, pupil reactions, visual field screening (peripheral vision testing), ocular motility (eye muscle movement and control), eye health assessment (both front and inside your eye).
During the eye examination the health practitioner may use various pieces of equipment including a camera, a tonometer (used to measure eye pressure) and a slitlamp (a binocular microscope to look in detail at the front surface of the eye). These enable the monitoring of conditions such as diabetic retinopathy, glaucoma, cataracts and macular degeneration.
How often should I have an eye examination?
Everyone should have a regular eye examination regardless of whether they can see well or not since many diseases are asymptomatic and may be discovered during an eye examination. Most optometrists recommend eye examinations every 2-3 years or more frequently in cases of cardiovascular diseases such as diabetes, glaucoma or cataract.
How long does an eye examination take?
Most eye examinations take approximately 30 minutes.
What does it cost to have my eyes examined?
Examinations are usually bulk-billed to Medicare with little or no out of pocket expenses. For all new patients and patients with eye diseases there is usually a fee to cover the cost of any tests requiring the use of digital equipment such as a camera or corneal topographer. The optometrist will usually inform you if these are required prior to the examination.
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Dyslexia
What is dyslexia?
Dyslexia is often defined as a specific learning difficulty, irrespective of the level of intelligence. Most people with dyslexia are diagnosed in early primary school where they appear to have difficulty learning to read and spell.
What causes dyslexia?
The exact causes of dyslexia remain unknown, however it is believed to be a neurological mis-wiring with a hereditary component (tends to be in other members of the family), although no specific gene has yet been identified. Brain imaging techniques show that people with dyslexia process phonological information (i.e. sound-based information) in a different area of the brain than non-dyslexics. Other studies have suggested that people with dyslexia process visual information more slowly than those without. There are several theories that attempt to explain dyslexia including: deficits in the cerebellum, the magnocellular pathways, deficits in perceptual noise exclusion, deficits in phonological processing &/or rapid auditory processing and deficits in visual processing.
Dyslexia is not related to intelligence with many highly intelligent and creative people having this condition e.g. Leonardo da Vinci, Thomas Edison, Albert Einstein, Whoopi Goldberg, Tom Cruise, John Lennon etc.
How common is dyslexia?
It is estimated that dyslexia affects between 5% - 15% of the population.
What are the signs and symptoms of dyslexia?
Despite having average intelligence, people with dyslexia usually have difficulty when reading and spelling. Other symptoms include: difficulty associating sounds with the letters that represent them, difficulty segmenting words into individual sounds, or blending sounds to make words, confusion with left/right, reversals, difficulty distinguishing between similar sounds in words; mixing up sounds in multi-syllable words, difficulty with time keeping & organization skills, and difficulty comprehending rapid sequential instructions.
Can dyslexia be treated?
While there is no specific “cure” for dyslexia, successful management usually involves a multi-sensory and multi-disciplinary approach from specialists such as speech pathologists, occupational therapists and behavioural optometrists. Effective treatment can improve a person’s performance so that the symptoms are significantly reduced.
If you require further information please visit the websites listed below:
Children with special needs
Australasian College of Behavioural Optometry - vision & learning
College of Optometrists in Vision Development - care
Specific Learning Difficulties Association (SPELD)
Australian Resource Educator’s Association (AREA)
Parents Active for Vision Education (PAVE)
British Dyslexia Association (BDA)
Australian Council for Educational Research
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Computers and vision
Computer vision syndrome (CVS) affects many people who spend hours daily in front of a computer screen. It is often defined as a collection of symptoms which arise from prolonged computer use.
CVS arises because the visual demands of the task exceed the visual abilities of the individual to comfortably perform the task. Unlike printed characters on a page, computer text is less distinct and the eyes often focus on a location away from the screen thereby leading to even more defocused print. The act of regaining focus several times during the day is thought to lead to fatigue and eye strain.
There are several non-visual related symptoms such as Carpal Tunnel Syndrome, neck & back muscle strains and tendon disorders. These disorders are generally termed Repetitive Strain Injuries (RSI). Vision related symptoms include: headaches, loss of focus, burning, itchy, dry, tired eyes, double vision and glare sensitivity.
Various studies indicate that about 20% of video display terminal workers have musculo-skeletal disorders and up to 90% have visual symptoms.
Treatment: Many of the vision related problems related to computer screens can be reduced or eliminated by appropriate ergonomic designs incorporating posture adjustments, lighting control and preventative vision care. In cases where there is a pre-existing visual condition then artificial tear supplements and glasses designed for computer use made with various lens coatings and tints may reduce many of the symptoms.
More information:
All about vision - computers
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Contact Lenses
Contact lenses are a refreshing alternative to spectacles and are worn for a variety of reasons including sports, work requirements, social and cosmetic reasons, or when vision quality will exceed that of glasses. Most contact lenses are made of a soft, flexible material, and are extremely comfortable to wear. With new advances in technology, there is a contact lens type to suit almost every person and their individual needs, including high oxygen contact lenses that can be worn in the eyes for up to 30 continuous days.
More information:
Download our Contact Lense brochure (PDF 252kb)
Optometrists Association Australia - contact lenses
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Diabetes
Diabetes is a metabolic syndrome which results in an increase in blood sugar levels caused by an impairment of the body’s natural insulin production or action. Diabetes is becoming increasingly prevalent in Western society, particularly in the Type 2 form which affects people later in life, and is thought to be related to issues such as over consumption of food, hyper-refined foods, and a lack of regular exercise. One of the undesirable affects of diabetes is that it causes the body’s micro blood vessels to become leaky and can even reduce the supply of blood to important tissues. In the eye, there is a risk that bleeding can occur in the retina which can result in sudden and often permanent vision loss. A reduction in blood supply to parts of the eye can also result in secondary affects such as glaucoma. It is for these reasons that people with diabetes need to have their eyes examined on a yearly basis.
More information:
Optometrists Association Australia - diabetes
University of Melbourne - Ophthalmology Dept
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Hyperopia (Long-Sightedness)
Hyperopia is a refractive error of the eye caused by the eye’s lens and cornea (clear front surface of the eye) focusing light sharply behind the retina (image detector film at the back of the eye) rather than directly on to it. This causes the image at the retina to be blurry, however in individuals that have a good ability to accommodate (refocus light automatically using the natural lens) the image can be focused forward and in many cases focused sharply back on to the retina. In this way many people with hyperopia see well at most distances, however their ability to do so will decrease with age, closeness to the viewing target, and the magnitude of their hyperopia. Hyperopia can be corrected with either spectacles or contact lenses.
More information:
Optometrists Association Australia refractive error
University of Melbourne Ophthalmology Dept
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Itchy Eye
This is a term describing the irritation sensation being experienced by the individual. It often requires them to rub their eyes as a reaction to the irritation. It is most commonly caused by airborne or environmental irritants, and is a common symptom of allergic conjunctivitis. This condition can be relieved by using cold compresses over the eyes or anti-histamine medications.
More information:
All about vision - allergies
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Myopia (Short-Sightedness)
Myopia is a refractive error of the eye caused by the eye’s lens and cornea (clear front surface of the eye) focusing light sharply in front of the retina (image detector film at the back of the eye) rather than directly on to it. This causes the image at the retina to be blurry, and the individual will be unable to improve their vision by accommodating (refocusing light automatically using the natural lens) as this will only result in moving the sharp image even further forward of the retina. People with myopia experience blurry vision in their far distance view, however they are often able to see clearly at nearer distances. Myopia can be corrected with either spectacles or contact lenses.
More information:
Optometrists Association Australia refractive error
University of Melbourne Ophthalmology Dept
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Presbyopia
Presbyopia is a condition which makes it harder for the individual to accommodate (refocus light automatically using the natural lens). For most people this will make it more difficult for them to focus at nearer tasks such as reading books. It is a progressive condition with a common age of onset being in the early forties, progressing right through until about the early sixties. It is caused by the loss of flexibility in the eye’s natural lens which is brought about by a normal growth and hardening of the lens. Presbyopia is commonly corrected with reading glasses and multifocal spectacles, however it can also be corrected with contact lenses. It is important that people with presbyopia have their eyes examined every two years due to the progressive nature of the condition.
More information:
Optometrists Association Australia refractive error
University of Melbourne Ophthalmology Dept
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Pterygium
A pterygium is a skin-like triangular growth containing visible blood vessels, which begins growing from the conjunctiva (transparent membrane covering the white of the eye) across to and over the cornea (clear front surface of the eye). This growth is usually caused by excessive and prolonged exposure to the sun’s harmful UV rays and dusty environments. Whilst it is common for a pterygium to progress slowly, it should be monitored under magnification on a regular basis. A pterygium can be physically removed by an eye specialist if it becomes excessively large and threatens vision by growing towards the pupil (black hole/aperture in the centre of the eye) or if it becomes persistently inflamed or unsightly. Sun protection with a broad-brimmed hat and large coverage sunglasses is the best protection against developing this condition.
More information:
Optometrists Association Australia - eye diseases
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Spectacles (Glasses)
Spectacles are a form of visual aid worn on the face. They comprise of a frame of some description allowing for the successful mounting of optical lenses in front of the eyes so that the individual may view their visual task through them. The frames can be made from many materials, including high performance metals such as titanium, and more solid shell-like materials such as acetate. In general, spectacles have a nose bridge or pads worn over the nose, and temple pieces worn over the ears, however some more historical types of spectacles include monocles (held in place by the eye socket), lorgnettes (spectacles with a handle and then held over the eyes), and pince-nez (balanced and pressed upon the bridge of the nose). It is claimed that the first wearable spectacles were invented in Italy as far back as 1284, however the first pictorial evidence of the use of spectacles was not forthcoming until 1352.
More information:
Wikipedia
Optometrists Association Australia spectacles
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Amblyopia
A person with amblyopia (often referred to as “lazy eye”) has a condition in which the message or image received by the affected eye and sent to the visual cortex (part of the brain we see with) is of poor quality, making the sight of that eye poor. An adult or child with amblyopia will have poor vision that cannot be corrected simply with spectacles.
Common causes for amblyopia are a tropia (turned eye) or a large difference in the refractive error (shortsightedness, longsightedness or astigmatism) between the person’s eyes.
The visual cortex continues to develop from when we are born until we reach 7 or 8 years of age. In amblyopia, normal development does not occur in one eye. It is important to detect and commence treatment for the condition as early as possible in a child’s life. Children are often given a basic eye test in their first year of school to screen for amblyopia.
Amblyopia is often inherited. If a parent, grandparent, uncle or aunt has a “lazy eye” then a child has a much greater chance of developing this condition.
Treatment can involve a combination of spectacles, eye-patching and vision therapy (various eye exercises) to help train the amblyopic eye to function normally.
More information:
All about vision - amblyopia
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Astigmatism
Astigmatism is a focusing error which can cause blurred vision at both distance and near. Most astigmatism is caused by the cornea (clear front surface of the eye) not being spherical (like a bowling ball) but more oval or egg shaped (like an Australian Rules football).
Astigmatism causes distortion of the vision where some directions of the image are more out of focus than others. This can be contrasted with myopia (shortsightedness) where all directions are equally blurred.
Astigmatism is not an eye disease, but a focusing error of the eye. Correction of astigmatism is achieved with spectacles, hard or soft contact lenses or laser eye surgery.
More information:
Optometrists Association Australia - refractive error
University of Melbourne Ophthalmology Dept
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Conjunctivitis
The conjunctiva is the membrane that covers the inner surface of the eyelid and the white part of the eyeball (the sclera). By definition, conjunctivitis is an inflammation of this tissue. The condition is often characterized by the white of the eye appearing red and inflamed. There is often discharge from the eye that can be pus (sticky), clear fluid (watery) or fibrous (stringy) depending on what is causing the conjunctivitis. The degree of pain or discomfort varies considerably depending on the cause and severity of the condition.
Conjunctivitis can be caused by bacterial or viral infection, dry eyes, allergic reactions, eyelid disorders or it can be a sign of various systemic “whole of body” health issues.
Treatment is dependent on an accurate diagnosis. Bacterial conjunctivitis can require antibiotics, viral conjunctivitis is often self-limiting but very contagious and allergic conjunctivitis may require anti-inflammatory treatment with steroid drops or anti-histamines.
Red eyes are not always due to conjunctivitis. Some very serious eye conditions can cause your eye/eyes to become red. If you think you have conjunctivitis it is important to see an eye care professional to ensure an accurate diagnosis. This will allow the correct treatment to be commenced and the rapid resolution of the condition.
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Floaters & Spots
Floaters or spots are cloudy semi opaque particles within the eye that can be seen within the field of vision. When they first appear they can appear like an insect or a cobweb. When the patient tries to look at them they dart away because they move when the eye moves.
The causes of floaters are normally age related changes to the vitreous (jelly that fills the eyeball) or eye injuries. There are also some serious eye diseases (such as retinal tearing or retinal detachment) that can cause floaters to appear. The cause of floaters can be benign and harmless or severe and vision threatening. For this reason it is important to have you eyes examined immediately when floaters appear or increase in number.
More information:
All about vision - spots & floaters
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Laser Vision Correction
Laser surgery to correct focusing errors and allow a person to “throw away your glasses” involves the use of a special laser to re-shape the surface of the cornea (clear front surface of the eye).
Laser procedures have been performed in Australia since 1991 and are extremely safe. There are several different types of laser surgery available. A thorough eye examination at Kosmac & Clemens optometrists will determine your suitability for this treatment. Laser correction can be used to treat myopia (shortsightedness), hyperopia (longsightedness), astigmatism and can even offer a solution to presbyopia (poor near focus due to age).
One of our optometrists, Ian Clemens, had LASIK laser surgery in 2001. He has a special interest in this area of practice, but all of our optometrists can advise you of your options regarding this procedure.
More information:
All about vision - vision surgery
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Glaucoma
Glaucoma is a condition in which the nerves that allow us to see gradually become damaged and die. This prevents information from the retina (image detector film at the back of the eye) reaching the visual cortex (part of the brain that allows us to see).
It is often associated with a build-up of pressure involving the fluid inside the eye. There are many types of glaucoma and the symptoms are often mild or non-existent until the disease is quite advanced. For this reason, it is vital that people have regular eye examinations so that if glaucoma is present it can be treated in its early stages.
People with a family history of glaucoma are at much greater risk of developing the disease in their lifetime. Studies have shown that 10% of people over the age of 80 years of age have glaucoma but many are not aware that they have it and are untreated.
Most glaucoma cases can be treated easily in the early stages with eye drops or a simple non-invasive laser treatment. As glaucoma is more common as age increases it is recommended that people over the age of 40 should have an eye-test, including an eye pressure measurement, every two years.
More information:
Optometrists Association Australia - eye diseases
University of Melbourne - Ophthalmology Dept
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Macular Degeneration
The macula is the central part of the retina (image detector film at the back of the eye). It is the most sensitive part of the retina and is used to see the detail of things when you look directly at them. It is responsible for your ability to read, recognize faces and see colours clearly.
Macular Degeneration (MD) causes progressive macular damage resulting in loss of central vision but the peripheral (side) vision is not affected. This contrasts with glaucoma where peripheral (side) vision is usually lost.
For many years MD was untreatable, but over the past 10 years many new therapies have been developed to help slow the progression of MD. These include vitamin supplements, laser treatment and injections of special drugs directly into the eye.
MD occurs more frequently in older age groups. Our rapidly aging population has lead to MD being increasingly diagnosed and treated in recent years. The success of the treatment is often dependant on early detection and monitoring of the disease. People over 50 should have an eye examination at least every two years to ensure their macula is healthy.
More information:
Optometrists Association Australia - eye diseases
University of Melbourne - Ophthalmology Dept
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Retinal Detachment
The retina is the image detecting tissue that lines the inside of the eye ball. The retina works by taking images we see and passing that information via the optic nerve to our visual cortex (part of the brain we see with). This part of the brain interprets the information and allows us to see.
The retina can come away or detach from the inside of the eye due to various diseases or from trauma to the eye. If this happens, the retinal tissue that has detached will die if it is not reattached in a few days. This can result in visual loss. A retinal detachment is considered a medical emergency for this reason.
Symptoms of retinal detachment can include the appearance of floaters or spots in your vision, flashes of light that are seen when no light is present or a sudden decrease in the vision of one eye. If you develop any such symptoms it is important to have your eyes examined WITHIN 24 HOURS, especially if you have recently experienced any trauma to your head or eye.
More information:
All about vision - retinal detachment
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Visual Fields
Visual field testing is performed to assess how well your peripheral (off center or side) retina (image detecting film at the back of eye) is functioning. Reading letters on an eye chart only assesses your ability to see small details using the macula (most sensitive central part of the retina).
Visual field testing is used to detect and monitor a variety of conditions including glaucoma, multiple sclerosis, brain tumours, elevated intra-cranial (in the head) pressure, strokes and head injuries.
Your optometrist may suggest a visual field test if they suspect you may have some loss or reduction of your peripheral vision. The test involves looking at a central target while a machine shows different images or flashes of light in various locations around your field of vision. You need to provide a response as to whether you have or have not seen this image, usually by pushing a button.
The Visual Fields machine uses the results to create a map of your field of vision. Your optometrist will then interpret the results and discuss with you exactly what they mean.
More information:
Wills Eye Hospital
University of Ottawa Eye Institute
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