Glossary

DCR - Dacryocystorhinostomy  A surgical procedure to relieve the blockage of the nasolacrimal duct, which drains the tears from the eyes into the nose. This is done by making a small incision into the side of the nose, and then some bone is removed to make a connection between the lacrimal sac and the nose so that tears can freely flow.

Diabetes Mellitus - Diabetes is a disorder of the metabolism where sugars (glucose) are not oxidised to produce enough energy; this is due to a lack of insulin. Symptoms include: loss of weight, excessive thirst and urine production. There are two types of diabetes: Type 1 and Type 2. Type 1; insulin-dependent diabetes; usually occurs in childhood or adolescence; the individual has little or no ability to produce insulin and must rely on injections for survival. Type 2; noninsulin-dependent diabetes; usually occurs after the age of 40, but can be seen in younger individuals. The pancreas can still produce a small amount of insulin, but this is not adequate for the bodys needs; sometimes the body may become resistant to the effects of insulin. This can be treated with either oral hypoglycaemic drugs or insulin. Long term complications include damage to blood vessels; this can affect the nerves, kidneys and eyes; diabetic retinopathy.

Diabetic Retinopathy - Damage caused to the retina from complications with diabetes, often resulting in loss of vision; it affects 80% of the diabetic population. The disease has many stages; an individual with diabetic retinopathy may notice they have floaters; debris in the eye, affecting vision; double vision, macula oedema; fluid collecting and causing swelling on the macula at the back of the eye, haemorrhaging or retinal detachment.

Diagnosis - The identification of a disease by way of a patient's symptoms.

Diagnostic - The process of identifying or determining the nature and circumstances of an existing condition.

Dilated Pupil - Mydriasis - Enlargement of the pupil that does not contract, even in bright lighting, usually resulting from trauma or drugs. If there is direct trauma to the skull of an individual it can cause damage to nerves which control the muscles that are responsible for closing the pupil. Drugs can also control pupil size of an individual; Atropines and Mydriatics (such as Tropicamide, Phenylephrine and Cyclopentolate) are used in the Ophthalmic industry to temporarily paralyse muscles in the eye, which control pupil movement and to get a better view of the retina; back of the eye.

Dioptre - The unit of measure used to determine the refractive power of a lens. A negative dioptre value (eg -2.25) indicates an individual with myopia (short-sighted) and a positive dioptre value (eg +4.00) indicates an individual with hyperopia (long-sighted).

Diplopia - Double vision  The simultaneous perception of two images from one object; usually occurs from the lack of movement from one eye compared to the other. This can be caused by strabismus, squint, which often occurs in childhood, where one of the eyes moves horizontally or vertically away from the other. The brain can sometimes suppress one of the images; this is more common in children than adults. An individual can get temporary diplopia from intoxication from alcohol and drugs, or through concussion.

Drusen - The tiny white or yellow deposits on the Bruchs membrane (part of the retinal pigment epithelium) at the back of the eye, before the retina. Drusen are common after the age of 60 and they often signify the beginning of AMD (age-related macular degeneration).

Dry Eye Syndrome - Deficiency or abnormality in aqueous production or increased tear film evaporation. This results in uncomfortable, burning, gritty, and sometimes watery eyes, and in extreme cases erosion of the conjunctival and corneal epithelium. This condition is predominantly found in menopausal and post-menopausal women; there are no long term effects although severe untreated cases may result in impaired vision but rarely loss of sight.