Glossary

Haemorrhage - The loss of blood through a ruptured blood vessel either internally or externally.

Halos - A visual effect in the eye where coloured rings are seen around light sources. It is usually caused by imperfections in the visual system, such as cataracts or poor night vision from uncorrected refractive errors.

Haptics - The arms of the synthetic implantable lenses (IOLs) used in cataract and refractive surgery. The haptics hold the lens in place.

Haze - A visual effect in the eye that causes a reduction of contrast so that an object appears fainter or even disappears. It is caused by light scattering in the eye and is commonly reported with cataracts or following corneal surgery.

HFA - Humphreys Field Analyzer - An instrument used to test a persons visual fields to detect field losses due to damage to the visual pathways. It is helpful in monitoring glaucoma.

HRT - Heidelberg Retina Tomograph  A diagnostic instrument used in the early detection of glaucoma. It consists of a confocal scanning laser system that analyses 3-D images of the retina and optic nerve head and allows assessment of structural changes.

Hyperopia - Hypermetropia  Refractive eye condition where parallel light is focused behind the retina when the eye is relaxed causing near objects to be blurred. By the act of accommodation on the crystalline lens, the focus can be brought onto the retina for clear near vision. In the older eye, accommodation declines and spectacle lenses with a convex shape are needed to focus the light clearly onto the retina.

Hypoxia - A lack of oxygen in the tissues.