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A-Z Eye Health Glossary

Let's learn about the different terms used frequently
about your eyes and what they mean! 

A-Z Eye Health Glossary

When discussing some terms and definitions with your eye care practitioner, these terms can be commonly used when discussing the conditions and treatments available. 

A - D

Astigmatism :

Due to the curvature of the eyes when it is not completely round, causing blurry, distorted vision at all distances.

Amblyopia (Lazy Eyes) :

Can be caused by strabismus, anisometropia (imbalance of eye prescription) leading to undeveloped central vision on one eye and reliance on the other eye.

Age Related Macular Degeneration  :

Gradual loss of the central vision due to ageing and damaged macula.


Clouding/yellowing of the natural lens in the eye. Commonly due to ageing along with other factors such as UV exposure, certain medication, smoking and diabetes. 


Bump on the eyelids that is usually not painful due to obstructed oil glands along the eyelid. 

Colour Deficiency:

Inability to distinguish certain colours, this can be due to deficiencies of some types of cones or absence of these cones (colour receptors).


Pink eye, Inflammation of the conjunctiva, can be infectious or allergic causes. Symptoms can include, tearing, discharge, burning sensation, pain, discomfort and others. 

Diabetic Retinopathy:

Leakage of blood into the retina due to long-term or uncontrolled diabetes. 

Double Vision / Diplopia:

When two images of the same object is seen by one or both eyes 

Dry Eyes:

Lack of lubrication or moisture in the eyes, can be temporary or chronic caused by ageing, certain medications, contact lens wear. Symptoms include eye pain, discomfort, gritty feeling, itchiness, light sensitivity, pink/red eye, tearing.

E - L

Eye twitching:

Spasm of a small muscle in the eyebrow involuntarily, can be caused by stress, not enough sleep, caffeine, alcohol usage or eye strain. 

Epi-Retinal Membrane:

Thin layer of scar tissue that can tug on various areas of the retina. 


Orange dye solution that become yellow-green when exposed to blue light and helps any corneal lesion or dryness to be examined. 


Optic nerve damage and peripheral loss of vision due to the elevated eye pressure. It can be acute (angle closure) or chronic (Open angle). 

Hyperopia (Far-sightedness):

A type of refractive error that results in the person requiring greater effort when focusing to see distant and near objects clearly. Glasses may not may not be required to see clearly depending on the age and degree of prescription. 

Intraocular Pressure (IOP): 

Eye pressure, determined by the amount of aqueous humour generated and drained out. High eye pressure can be a sign of glaucoma. 


Degenerative condition of the cornea that can cause the cornea to become cone shaped. Vision can be distorted or become double. 


Laser Assisted In Situ Keratomileusis, surgical process of creating a flap on the cornea and removing the tissue below with an excimer laser and putting the flap back.

Low Vision:

Vision cannot be corrected to a satisfactory level with glasses, contact lens and surgery. It usually is a result of eye diseases such as glaucoma or macular degeneration.

M - Z

Myopia (Short-sightedness): 

A type of refractive error where a person is able to see near objects clearly but vision in the distance is blurry. 

Orthokeratology (Ortho-K):

Speciality Gas Permeable hard contact lenses that are fitted by an optometrist to reshape the cornea to correct refractive errors. Usually worn at night. 


Yellowish lesion on the conjunctiva near the cornea, degenerative changes that are due to the leakages of protein near the limbus. 


An elevated bump that starts from the white part of the eye (sclera) into the cornea. 


Droopy eyelids


Condition that is related to ageing that begins after 40 years old where the vision at near becomes hard to focus. 

Retina Detachment:

When the retina is separated from the choroid layer of the eye. Symptoms can include flashes, floaters, curtain-like shadow over your vision, blurry vision and vision loss. 


Red bump near the eyelid due to infected glands. Symptoms includes, redness, pain, swelling, tearing


Misalignment of the eyes. 


Depth-perception/3D vision 

Subconjunctival Haemorrhage:

Benign bleeding of the surface blood vessels on the eyes that can leave a red patch. Commonly caused by sneezing, coughing, high blood pressure, trauma and others. 

Visual Acuity:

Vision quality and sharpness. 20/20 or 6/6 is considered normal acuity. 

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