Vision Disorders and Eye Conditions

The following is a list of the most frequently occurring eye disorders. Most people will suffer from one or perhaps several of these conditions during their lives. However if treated correctly, with appropriate vision correction where necessary, they should not lead on to more serious problems.

Myopia

Myopia is more commonly known as “short-sightedness”. It is a condition caused by the eyeball itself being either too long, or by the cornea (the front of the eye) being too curved, or a combination of both. The result is that light from distant objects is focuses in front of the retina instead of directly on it. This makes far away objects appear out of focus, resulting in myopia sufferers having difficulty for example in reading road signs when driving or in watching sports. Myopia can be corrected with either soft (disposable) contact lenses or gas permeable contact lenses.

Hyperopia

Hyperopia is better known as “long-sightedness”. It is also known by the term hypermetropia. This is a condition in which either the eyeball is too short, or the cornea is too curved, or a combination of both. It is the opposite of myopia. The result is that light from objects focuses behind the retina, resulting in blurred vision when viewing objects at close quarters such as when reading a book. The focussing ability of the eyes also diminishes as we get older (see presbyopia, below), resulting in even greater difficulty in focusing on close-by objects. Hyperopia can be corrected with either soft (disposable) contact lenses or gas permeable contact lenses.

Presbyopia

Presbyopia refers to the loss of the eyes’ ability to focus. With advancing years, the focussing lens inside the eye begins to harden, with the result that the closest point that we can focus on moves further and further away until reading small print becomes ever more difficult. Presbyopia is the reason why many people who have never previously worn spectacles find that they need a pair of reading glasses when they reach their mid-forties. However, there are a number of contact lens designs now available which offer an alternative to spectacles for myopia sufferers.

Astigmatism

Astigmatism is a condition in which the front of the cornea (the front of the eye) is oval-shaped instead of round. There are two types of astigmatism, regular astigmatism and irregular astigmatism. The former type can be corrected either with glasses, soft contact lenses (toric lenses) and gas permeable contact lenses. Indeed the range of contact lenses available to correct regular astigmatism is constantly increasing.

Irregular astigmatism, unless quite mild, is much more difficult to correct with spectacles or soft contact lenses. Irregular astigmatism can be caused by conditions such as keratoconus and corneal scarring.

Gas permeable contact lenses correct astigmatic vision by maintaining their shape on the cornea, with any corneal irregularity being filled by the tears behind the lens. Soft toric contact lenses function in a different way when used with irregular astigmatism. Toric lenses possess two different focussing powers, created with curvatures at different angles (one for the astigmatism, the other for either myopia or hyperopia as necessary). A toric lens also possesses a feature to keep the contact lens stable on the eye when you blink or look around. To maintain sharp vision, toric contact lenses cannot rotate on the eye.

Keratoconus

Keratoconus is a medical condition where the cornea thins and then slowly pushes forward in the shape of a cone. In the early stages of the condition, sufferers will regularly still see well with spectacles or soft contact lenses, but as the condition progresses gas permeable contact lenses are needed to improve distortion in vision.

Many new designs of gas permeable lenses now exist to correct keratoconus, including large diameter contact lenses which can be center better on the eye and provide a greater degree of comfort than traditional lenses.

Blepharitis

Blepharitis is an inflammation of the eyelids. It usually affects the edges of the eyelids. Although not usually serious, Blepharitis may cause discomfort and irritation. Blepharitis is typically chronic (persistent) and usually affects both eyes.

The exact cause of blepharitis is unknown. It tends to flare-up and then reduce in severity. If you do suffer from blepharitis, it is possible you will always have it from time to time since it does tend to recur. Unfortunately there is no one-off simple cure for blepharitis. However, symptoms can usually be eased with regular treatment.

Meibomitis

The meibomian glands are the oil-producing glands located in both the upper and lower eyelids. These glands secrete the lipid (oily) layer of the tear film which is essential in preventing rapid evaporation of tears. Thus any dysfunction of these glands (such as by clogging) can have an immediately noticeable impact on the quality and stability of the tear film. This condition is known as meibomian gland dysfunction or simply meibomitis.

Sometimes the oil can become thicker than normal which can lead to blockage of the narrow duct which takes the oil from the gland to the tear film. This can lead to overfilling and swelling of the glands, along with causing a dry eye, since the oil cannot reach the tear film. Severe blockage can lead to a cyst and possibly infection.

Depending on the cause, meibomian gland dysfunction is often treated with oral antibiotics such as doxycycline, and/or topical antibiotics, as well as hot compresses which liquefy any secretions that have solidified and are clogging the glands.

Dry Eyes

Today many newer contact lens materials are available providing improved comfort to people suffering from dry eyes than was previously possible with older lens materials. Specially designed polymers have been developed which dry out less on the eye, resulting in less awareness of the lens, better clarity of vision and less reliance on wetting drops.

Computer Vision Syndrome

When we perform tasks requiring concentrated vision - such as reading, driving, reading and working at the computer - we tend to blink less often than normal. This can result in contact lens drying, which will make the lenses less comfortable, as well causing blurred vision. This can be managed by applying rewetting eye drops to rehydrate the lenses as often as needed. Indeed simply blinking more frequently can be a great help. There are also new lens materials available which dry out less, especially in air-conditioned environments.