Vision A-Z

Amblyopia is a term used to describe an uncorrectable loss of vision in an eye that appears to be normal. It's commonly referred to as "lazy eye" and can occur for a variety of reasons.
Some causes of amblyopia include: strabismus (crossed or turned eye), congenital cataracts, cloudy cornea, droopy eyelid, unequal vision and uncorrected nearsightedness, farsightedness or astigmatism. Amblyopia may occur in various degrees depending on the severity of the underlying problem. Some patients just experience a partial loss; others are only able to recognise motion.

Astigmatism means that a corneal or lens surface is oval like a rugby ball instead of spherical like a basketball. Most astigmatic surfaces have two curves - a steeper curve and a flatter curve. This causes light to focus on more than one point in the eye, resulting in blurred vision at distance or near. Astigmatism often occurs along with nearsightedness or farsightedness.


(Granulated Eyelids)
Blepharitis is a common inflammatory condition that affects the eyelids. It usually causes burning, itching and irritation of the lids. In severe cases, it may also cause styes, irritation and inflammation of the cornea (keratitis) and conjunctiva (conjunctivitis). Some patients have no symptoms at all.

A cataract is a clouding of the natural lens, the part of the eye responsible for focusing light and producing clear, sharp images. The lens is contained in a sealed bag or capsule. As old cells die they become trapped within the capsule. Over time, the cells accumulate causing the lens to cloud, making images look blurred or fuzzy. For most people, cataracts are a natural result of ageing.

A chalazion (stye) is a small lump in the eyelid caused by obstruction of an oil producing or meibomian gland.

Colour Blindness

Colour blindness may be a hereditary condition or caused by disease of the optic nerve or retina. Acquired colour vision problems only affect the eye with the disease and may become progressively worse over time. Patients with a colour vision defect caused by disease usually have trouble discriminating blues and yellows.

Inherited colour blindness is most common, affects both eyes, and does not worsen over time. This type is found in about 8% of males and 0.4% of females. These colour problems are linked to the X chromosome and are almost always passed from a mother to her son.
Colour blindness may be partial (affecting only some colours), or complete (affecting all colours). Complete colour blindness is very rare. Those who are completely colour blind often have other serious eye problems as well.

Computer Vision Syndrome

Computer vision syndrome (CVS) is a term that describes eye-related problems and the other symptoms caused by prolonged computer use.

Signs and Symptoms
• Blurred near vision
• Difficulty focusing from close to far and back again
• Sore, irritated eyes
• Dry eyes
• Red eyes
• Eye fatigue
• Headaches that disappear after a period of rest
• Irritation and discomfort while wearing contact lenses
• Soreness and pain in the neck, shoulder, and back

(Pink Eye)
Conjunctivitis, commonly known as pink eye, is an infection of the conjunctiva (the outermost layer of the eye that covers the sclera). The three most common types of conjunctivitis are: viral, allergic, and bacterial.

Dry Eye Syndrome
Dry eye syndrome is one of the most common problems treated by eye care practitioners. Millions of people worldwide suffer from dry eyes. It is usually caused by a problem with the quality of the tear film that lubricates the eyes, the normal ageing process, hot, dry or windy climates, high altitudes, air-conditioning and cigarette smoke

Farsightedness or hyperopia, occurs when light entering the eye focuses behind the retina, instead of directly on it. This is caused by a cornea that is flatter, or an eye that is shorter, than a normal eye. Farsighted people usually have trouble seeing up close, but may also have difficulty seeing far away as well.

Flashes and Floaters
(Posterior Vitreous Detachment)
The space between the crystalline lens and the retina is filled with a clear, gel-like substance called vitreous. In a new-born, the vitreous has an egg-white consistency and is firmly attached to the retina. With age, the vitreous thins and may separate from the back of the eye. This is called posterior vitreous detachment (PVD), a very common, usually harmless condition.

As the vitreous pulls free from the retina, it is often accompanied by light flashes or floaters. Floaters are caused by tiny bits of vitreous gel or cells that cast shadows on the retina. Flashes occur when the vitreous tugs on the sensitive retinal tissue.

Foreign Body
Anyone who has felt as if there was a grain of sand in his or her eye has probably had a foreign body. Foreign bodies might be superficial, or in more serious injuries, they may penetrate the eye. Fortunately, the cornea has such an incredible reflex tearing system that most superficial foreign bodies are naturally flushed out with our natural tears. But if the object is more deeply embedded, medical attention is required.

Glaucoma is a disease caused by increased intraocular pressure (IOP) resulting either from a malformation or malfunction of the eye's drainage structures. Left untreated, an elevated IOP causes irreversible damage to the optic nerve and retinal fibres resulting in a progressive, permanent loss of vision. However, early detection and treatment can slow, or even halt the progression of the disease.

Headaches may occur for any number of reasons including: sinus conditions, hypertension, allergies, tumours, hormonal changes, and most frequently, stress. They are not usually associated with problems related to the eyes.
Eye-related headaches
Headaches related to eye fatigue:
• Headaches that begin after an extended period of reading, computer use, watching television, or close work
• Burning eyes
• Fatigue

• Throbbing pain
• Sensitivity to light and sound
• Nausea and vomiting
• Visual "aura" including: light flashes, jagged lights, missing areas of vision

Acute angle-closure glaucoma
• Intense headache that is usually centralised over brow area
• Nausea and vomiting
• Glare or haloes around lights

Infant's vision
Did you know that your baby has to learn to see? Proper prenatal care and nutrition can help your baby's eyes develop even before birth.
Age six months, take your baby to your optometrist for his or her first thorough eye examination. Vision development and eye health problems can be more easily corrected if treatment is begun early.

Keratoconus is a degenerative disease of the cornea that causes it to gradually thin and bulge into a cone-like shape. This shape prevents light from focusing precisely on the macula. As the disease progresses, the cone becomes more pronounced, causing vision to become blurred and distorted. Because of the cornea's irregular shape, patients with keratoconus are usually very nearsighted and have a high degree of astigmatism that is not correctable with glasses.

What is low vision?
Anyone with reduced vision is visually impaired, and can have problems functioning, ranging from minor to severe difficulty. There are two general classifications of low vision in use today:
• partially sighted
• legal blindness

What causes low vision?
Several eye diseases may be responsible for low vision, including:
• Macular Degeneration
• Diabetic Retinopathy
• Retinitis Pigmentosa
• Retrolental Fibroplasia
• Retinal Detachment
• Cataracts
• Glaucoma

Macular Degeneration
Age-related macular degeneration (ARMD) is a degenerative condition of the macula (the central retina). It is one of the most common causes of vision loss in the over 50's, and its prevalence increases with age. AMD is caused by hardening of the arteries that nourish the retina. This deprives the sensitive retinal tissue of oxygen and nutrients that it needs to function and thrive. As a result, the central vision deteriorates.


Nearsightedness or myopia, occurs when light entering the eye focuses in front of the retina instead of directly on it. This is caused by a cornea that is steeper, or an eye that is longer, than a normal eye. Nearsighted people typically see well up close, but have difficulty seeing far away.

This problem is often discovered in school-age children who report having trouble seeing the chalkboard. Nearsightedness usually becomes progressively worse through adolescence and stabilises in early adulthood.


A pinguecula is a benign, yellowish growth that forms on the conjunctiva caused by ultraviolet light


Presbyopia is a term used to describe an eye in which the natural lens can no longer accommodate. Accommodation is the eye's way of changing its focusing distance: the lens thickens, increasing its ability to focus close-up. At about the age of 40, the lens becomes less flexible and accommodation is gradually lost. It's a normal process that everyone eventually experiences.

Most people first notice difficulty reading very fine print.

Pterygium is a raised, wedge-shaped growth of the conjunctiva.

Refractive Surgery/Laser Surgery

Sight is our most precious sense. People who need a refractive correction know all too well the frustration of total dependency on glasses and contact lenses. Refractive Surgery is a family of surgical procedures designed to reduce or eliminate common vision abnormalities. These procedures help alter the way the light is focused on the retina by using precise surgical techniques to reshape the front surface of the eye or cornea.
LASIK (Laser Assisted in Situ Keratomilensis)
The procedure is nearly painless and is performed under topical anaesthesia. Microscopic amounts of cornea tissue are vaporised from the surface of the cornea by means of a computer-guided laser.


(Crossed or turned eye)
Strabismus is a problem caused by one or more improperly functioning eye muscles, resulting in a misalignment of the eyes.

Vision and Driving

Vision is the one human sense essential for safe driving. It is not easy to determine the minimum level of vision for safe driving. As visual standards have never internationally been agreed upon. Apart from suitable "normal" vision at distance, other visual functions such as the extent of visual fields, dark adaptation, stereopsis and glare recovery, are also important for "safe" vision when driving.

Visual Acuity

Is the capacity to discriminate the fine details of objects in the field of view. It is specified in terms of the minimum dimension of some critical aspects of a test object that a subject can correctly identify. The expression 20/20 or 6/6 or 1.0 vision denominates "normal vision" or 100% vision.

Vision and Sport
• Vision, just like speed and strength, is an important ingredient in how well you play your sport. Your vision is composed of many skills, and just as exercise and practice can increase your speed and strength, it can improve your vision skills.
• An evaluation by a sports vision optometrist can pinpoint your individual problems and needs as related to your sport. Remember, a thorough eye examination by your optometrist is a great place to begin "getting the winning edge."

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