Glossary

Capsular Haze - Posterior capsular opacity  Can occur after cataract surgery and is often referred to as a secondary cataract. This is when the cataract has been removed; the capsule in the eye is left intact and the epithelial cells grow over the back of the capsule, which rarely results in worse, blurred vision than before.

Capsulotomy - YAG Laser Capsulotomy  Is a procedure often done after cataract surgery to remove capsular haze, which blurs the vision. The laser is applied which creates an opening in the hazy capsule, giving an instant improvement in vision.

Cataract - A clouding of the crystalline, natural lens in the eye resulting in blurred vision. This occurs mainly in old age, when the protein in the lens starts to clump together forming a cloudy part to the lens. Cataracts can also occur from trauma to the eye or from long periods of UV light exposure. There are three main types of cataract: nuclear cataract, resulting in increased density and yellowing of the centre of the lens; cortical cataract, where the clouding occurs in the outer part of the lens moving towards the centre; subcapsular cataract, develops on the back of the lens. Cataracts can be surgically removed.

Cataract Extraction - The surgical removal of a cataract, cloudy lens, from the eye. In extracapsular cataract extraction the clouded lens is removed, leaving behind the capsule to support the intra-ocular lens implant. In intracapsular cataract extraction both the clouded lens and the capsule are removed; this procedure is rarely done today.

Central Vision - Straight ahead vision  Used for driving and reading; identifying fine detail and colour. Central vision results from the stimulation of the fovea and macular area of the retina. The retina is made up of two types of cells; cones and rods, the cones are nerve cells which are sensitive to light, fine detail, and colour.

Ciliary Body - The part of the eye that connects the iris to the choroid membrane; layer of nourishment for the retina. It produces aqueous humour, watery fluid in the anterior segment of the eye, and helps to maintain eye pressure. It also contains the ciliary muscle.

Ciliary Muscle - Is the muscle involved in accommodation and is attached to the crystalline lens via the Zonules; suspensory ligaments of the lens. Contraction of the muscle alters the curvature of the lens and allows a change in focus.

CLE - Clear Lens Extraction (also called RLE - Refractive Lens Exchange)  Is a procedure used for some refractive patients when laser may not be suitable. It is similar to cataract surgery, except that the removed lens is clear and not cloudy. Then an intra-ocular lens is implanted into the eye, enabling the individual to have a good level of vision. This treatment can be used for hyperopia (long-sighted -) and mild myopia (short-sighted +), but not for extreme myopia or astigmatism.

Closed Angle Glaucoma - Acute narrow angle glaucoma  This occurs when there is a sudden closure of the angle between the iris and the cornea, stopping the aqueous fluid, watery fluid in the front of the eye, to drain away properly. This increases the intra-ocular pressure (IOP) of the eye very quickly. This can cause headaches, pain, halos and vision loss. This form of glaucoma is a medical emergency, if the pressure in the eye is not released within a few hours there can be permanent peripheral, side, vision lost. Treatment includes eye drops or surgery to reduce the intra-ocular pressure.

Colour Blindness - The inability to perceive the difference between certain colours. There are retinal photoreceptors for blue, green and red-yellow, which all overlap slightly. These cells are responsible for absorbing different pigments of light and making up our colour vision. The most common types of colour blindness are Protanopia and Deuteranopia; the inability to distinguish between reds and greens. In Protanopia there is an absence of red retinal photoreceptors, which causes red to appear dark. In Deuteranopia there is an absence of green retinal photoreceptors, which causes difficulty in distinguishing between red and green. A rare type of colour blindness is Tritanopia; the inability to distinguish between blue and yellow; where there is a total absence of blue retinal photoreceptors. Rarer still is Monochromacy; where an individual possesses only one channel for the intake of colour information. They have the inability to distinguish any colours; the individual perceives all images in variations of brightness. Colour blindness is hereditary and affects predominantly Caucasian males (8%).

CONCERTO Laser - WaveLight CONCERTO Excimer Laser  A state-of-the-art laser system used in refractive surgery. An excimer laser is a form of ultraviolet chemical laser and it typically uses a combination of an inert gas (argon, krypton or xenon) and a reactive gas (fluorine or chlorine). Rather than cutting the eye, the excimer laser adds enough energy to disrupt the molecular bonds of the surface tissue, which effectively disintegrates into the air in a tightly controlled manner through ablation.

Conjunctiva - The delicate mucous membrane that covers the front part of the sclera; white part of the eye and inside the eyelids. It contains blood vessels and helps keep the eye moist.

Conjunctivitis - Pink eye  Irritation and/or inflammation of the conjunctiva; causing redness in the eye and edge of the eyelid. Usually from a bacterial infection, this may produce a pus-containing discharge. Can also be from a viral infection or allergy based, which may produce a watery discharge. Can affect one or both eyes at once and it can be treated with antibiotic eye drops.

Contact Lens - A tiny, thin, removable plastic lens worn directly against the front of the eye; they are used for corrective or cosmetic purposes. They are usually used for corrective purposes instead of individuals wearing spectacles and correct long and short-sightedness as well as astigmatism. Also a 'bandage lens' can sometimes be used to protect the eye. For cosmetic purposes a contact lens is usually coloured to change the appearance of an individuals iris. Contact lenses may be made from soft or hard materials and are suitable for different conditions and lifestyles. This includes polymers; plastic for RGP (Rigid Gas Permeable) and silicone hydrogel for soft lenses. RGP (Rigid Gas Permeable) lenses are hard lenses which let in oxygen into the eye. They are used for individuals who have a high level of astigmatism or Keratoconus as they have the ability to reshape the cornea and improve vision further than is sometimes possible with spectacles. Soft lenses are for use by all individuals; they give freedom from spectacles.

Cyclopentolate - A Mydriatic and Cycloplegic agent, similar to Atropine is used to temporarily paralyse the muscles in the eye which make the pupil contract and relax. This is often used by Ophthalmologists to get a better look at the retina; back of the eye. It can also be used to gain a persons refractive correction.

Cycloplegic Refraction - Cycloplegia is a temporary paralysis of the ciliary muscle, which is responsible for the contracting and dilating of the pupil to let in a certain amount of light into the eye. A cycloplegic refraction is when an Ophthalmologist or Optometrist obtains an individuals prescription after administering muscle paralysing eye drops. Cyclopentolate is one of the most commonly used muscle paralysing eye drops, its aim is to stop the eye accommodating, changing focus from distance to close up, therefore achieving an accurate prescription. The effect of the eye drops is a dilated pupil, which lasts for at least a few hours; this gives an excellent opportunity for a close look at the retina; back of the eye. Some individuals can experience dilated pupils for a few days; this is completely normal; it just depends on how quickly your body absorbs the drug. After a cycloplegic refraction it is recommended for an individual to have a pair of sunglasses; this is to aid their vision outside, where it may be bright.

Cylinder - The component in an individuals prescription that denotes astigmatism. If an individual has astigmatism they need two different correction powers in two different meridians, the first is the sphere power, and the second is the cylinder power.