Terminology explained

If, at any time during your visit to our practice, we use terminology that you don't fully understand, then please feel free to ask us for an explanation. Meantime, here is a list of common ocular abnormalities and conditions that we come across.

Important: This glossary lists a few of the better known ocular conditions and abnormalities (in alphabetical order) and is intended as a guide only. Patients experiencing loss or blurred vision or any pain in the eye, howsoever caused, should seek urgent medical advice immediately.


The ability for the eye to increase its positive power thereby facilitating the normal eye to focus on objects nearer the viewer. This is necessary when reading, for example. As we get older the amount of accommodation possible reduces due to a loss of elasticity within the eye and reading may become more difficult, necessitating extra help for reading, generally in the form of spectacles.


A condition in which both eyes have a notable difference in their degrees of Hypermetropia or Myopia. In the particular case where one eye is Myopic and the other Hypermetropic, the condition is known as Antimetropia.


A condition where the image falling on the retina is not equal in all meridians, causing blurring. It is caused by either the front or back of the eye being non-spherical (i.e. instead of being round, the surfaces may be shaped more like a rugby ball). This prevents the rays from forming a sharp focus. Generally the condition is simply corrected by the use of astigmatic or toric lenses which themselves have different powers over their surface correcting the fault within the eye. Astigmatism can equally affect both Myopic or Hyperopic patients.

Detached Retina

A condition in which part of the Retina (the layer within the eye which receives the image) becomes separated or detached from the inside of the eye. Symptoms include a sudden loss of vision over the area of vision affected. The condition is more common in myopic patients and the elderly. Prompt treatment involving laser surgery can often correct the condition, although patients generally suffer some permanent reduction in their visual field.


This can often be detected in an eye examination and the patient referred to their GP for treatment. Apart from the general effects of the condition, Diabetes if left untreated can cause major complications in the eye, particularly in later life and for this reason diagnosed patients are entitled to free NHS eye examinations.


An eye disease displaying an increase in the pressure within the eye (intraocular pressure) which, if untreated, can cause loss of vision and potentially blindness in the affected eye. During an eye examination, patients may be tested for signs of this condition. Patients who have direct family members suffering from this condition should have routine examinations on a regular basis (at least every 12 months). Patients over the age of 40 and with a mother, father, brother or sister, who have been diagnosed as suffering from glaucoma, are entitled to a free NHS eye examination.

Hordeolum (stye)

This acute and painful condition manifests itself as a red swelling on the eyelid which may eventually rupture and discharge a yellowish pus. It is generally caused by a localised infection of an eyelash follicle and treatment by antibiotics is sometimes necessary

Hypermetropia (Long Sighted)

A condition of the eye in which distant objects are focused behind the retina when the eye is in a relaxed state (see Accommodation) causing vision to be blurred. People with this condition are also known as, Hyperopic, Long sighted or Far sighted. The condition is corrected by the use of positive powered lenses.


A painful condition typified by swelling of the Iris (the circular coloured section of the eye surrounding the pupil). Symptoms include blurring and loss of vision. The condition is treatable with medication.


Patients suffering from Keratoconus have a thinning of the central portion of the cornea causing the cornea to adopt a slight cone shape. This prevents the formation of a sharp retinal image, causing blurring of vision. This condition is generally corrected with the use of contact lenses.

Long Sighted (see Hypermetropia)


Macular Degeneration

A condition affecting mainly the elderly in which the vision becomes progressively impaired, generally in both eyes. It is caused by a degeneration of the the receptors of the eye and affects mainly the central areas of vision. Treatment is normally restricted to the use of Low Visual Aids (powerful forms of magnifying lenses) but in some forms of disease, treatment by laser can arrest the condition.

Myopia (short sighted)

The condition of the eye in which distant objects are focused in front of the retina when the eye is in a relaxed state (see Accommodation), causing the image to be blurred. People with this condition are also known as, Short sighted or Near sighted. The condition is corrected by the use of negative powered lenses.


With increasing age the eye becomes less flexible and is unable to deliver the amount of extra positive power to view close objects (see Accommodation). This extra power is generally delivered by supplying the patient with reading glasses or alternatively a bifocal or varifocal lens, which will ensure sharp vision for both distance and reading.

Retinitis Pigmentosa

An inherited disease in which the patient's visual field becomes reduced (tunnel vision) and night time vision is severely impaired.

Short sighted (see Myopia)


Strabismus (squint)

Patients suffering from this condition have difficulty in fusing the images within each eye to produce a single image. This can cause double vision and in certain cases the two eyes will not appear to be looking in the same position. The condition can often be corrected by the use of spectacles, particularly in young children, together with ocular exercises. However, in some cases a simple surgical procedure is necessary.



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