Glossary: Terms & Definitions

Amblyopia: a condition that occurs when there is a reduction of vision in one eye. Amblyopia, which is often called “lazy eye,” is most common in infants and children, but it can also occur in adults. Amblyopia is not contagious.

Antioxidant: natural or synthetic substance which prevent and delay deterioration by oxygen. In the body, antioxidants are molecules that prevent the damaging effects of oxidation on animal tissue.

Arcus senilis: a cloudy opaque arc or circle around the edge of the eye, often seen in the eye of the elderly.

Astigmatism: visual disturbance caused by an error in the refraction of light within the eye.

Ataxia-telangiectasia: (AT) a genetic disease with a wobbly gait and "red eye" due to widening of small blood vessels in the conjunctiva of the eye. AT carries with it an increased risk of leukemia and lymphoma.

Black eye: also known as an eye contusion or a bruise around the eye. It may occur when a blow is sustained in or near the eye socket. If a bruise appears, it will usually do so within 24 hours of the injury.

Blepharitis: an inflammation of the outer edges of the eyelids, resulting in redness, itching, burning, scaly areas of skin around the eye and the feeling of something in the eye.

Cataracts: opaque colourisation of the lens, which is usually transparent, causing partial or complete blindness usually occurring in one or both of the eyes.

Computer vision syndrome (CVS): temporary condition resulting from focusing the eyes on a computer display for long, uninterrupted periods of time. Symptoms include headaches, blurred vision, neck pain, fatigue, eye strain, dry, irritated eyes, and difficulty refocusing the eyes.

Corneal abrasion: a scratch on the cornea. The cornea is the clear, outer surface that covers the front, or colored part, of the eye. The cornea has several layers that protect the eye. Deep corneal abrasions may scar and permanently impair vision.

Crossed eyes: also known as strabismus, where one or both of the eyes turn in, out, up, or down. It usually occurs in children but may also occur in adults. Permanent vision loss may result if strabismus is not detected and treated in a timely manner.

Diabetes: an increasingly common metabolic disorder involving the loss of proper glucose energy regulation, affecting all areas of the body.

Dry eye syndrome: also known as keratoconjunctivitis, a condition in which the conjunctiva (the membranes on the surface of the eye) become red and inflamed. The most common form of this condition is keratoconjunctivitis sicca. This occurs when the surface of the eye becomes dry due to a lack of tears. This dryness in the eye generally causes mild irritation, however in some individuals this condition may cause severe discomfort and visual problems.

Eye contusion: a bruise around the eye, commonly called a black eye (see above). It may occur when a blow is sustained in or near the eye socket. If a bruise appears, it will usually do so within 24 hours of the injury.

Far point: the point farthest from the eye at which an object is accurately focused on the retina when the accommodation is completely relaxed, being theoretically equivalent to infinity or, for practical purposes with respect to the normal eye, equivalent to any distance greater than 20 feet.

Far point of the eye: for the normal eye, the far point is at infinity. The rays of light from an infinitely distant point source are parallel and can be focused with the accommodation muscles of the eye when entirely relaxed.

Forced duction: a maneuver to determine whether a mechanical obstruction is present in the eye; with forceps grasping an eye muscle, an attempt is made to passively move the eyeball in the direction of restricted rotation.

Glaucoma: eye condition that arises when the fluids within the eye increase in pressure causing damage to internal eye structures.

High blood pressure: also called hypertension, one must have persistent high blood pressure across multiple readings for diagnosis.

Hyperopia (far sightedness): eye condition involving an error in focussing whereby near objects appear blurry, requiring corrective eyewear.

Inflammation: localised response from the body’s immune system mostly accompanied by pain, heat, sensitivity, redness and swelling.

Iris: the round, colored part of the eye that adjusts according to pupil size. The iris regulates the amount of light reaching the retina in the back of the eye.

Kleig eyes: a condition marked by conjunctivitis and watering of the eyes resulting from excessive exposure to intense light.

Lazy eye: dimness of vision, especially when occurring in one eye without apparent physical defect or disease.

Left-eyed: using the left eye in preference (as in using a monocular microscope)

Lens: the transparent structure inside the eye that focuses light rays onto the retina (the nerve cells at the back of the eye).

Macular degeneration: deterioration of the macular area of the retina causing visual disturbances, unclear vision, and a distorted central field of vision.

Migraine: a condition where periodic headache attacks cause considerable discomfort including nausea and vomiting.

Mucin: a component of mucus, used for many reasons in the body formed in glands. Mucin acts as a protective layer over the eye preventing dry eyes.

Myopia (near sightedness): eye condition involving an error in focusing whereby far objects appear blurry, requiring corrective eyewear.

Obesity: a situation where an increase in body weight to an unhealthy level associated with increased morbidity and mortality.

Odd eyed: having different colored eyes, usually one eye is blue, the other is copper or orange.

Omega-3 fatty acids: family of polyunsaturated fatty acids important in the diet and for maintaining health. Found naturally in flaxseeds, soybeans and walnuts, it is highly concentrated in fish oils. DHA and EPA are found in higher concentrations in fish oils, in particular, tuna oil. Tuna oil is purposely included in PM Eye Tonic as tuna oil has the highest level of DHA when compared with other fish oils. Being comparatively rich in DHA, tuna oil has a 5:1 ratio of DHA to EPA, similar to that present in nutrient-rich human breast milk.

Oxidative stress: situation where there is an abundance of oxygen free-radicals which can cause damage to cells.

Oxygen free-radicals: an oxygen atom or group of atoms, that are highly reactive with the potential to cause damage to cell structures.

Photoreceptors: Cells present in the eye specialised to capture and convey light and darkness, which is ultimately transmitted to, and processed by, the brain. There are two kinds, called rods and cones due to their shape. Predominantly, cone receptors allow us to see during the day and rods at night.

Presbyopia: common defect of refraction causing far-sightedness arising in middle aged people, requiring the need for corrective glasses. Distinguished from hyperopia that involves the cornea, presbyopia occurs after the progressive loss of function of the muscles that control the lens.

Refraction (vision): bending of light rays by the lens to focus on the retina for accurate visual processing.

Retina: 1. The delicate, 10-layered, nervous tissue membrane of the eye that receives images and sends them for processing through the optic nerve to the brain. 2. The sensory membrane that lines most of the back of the eye. The retina is composed of several layers including one containing the rods and cones. It receives the image formed by the lens and converts it into chemical and nervous signals which reach the brain by way of the optic nerve.

Retinitis pigmentosa: genetic disorder involving damage to the macula area of the eye causing progressive loss of vision.

Retinopathy: group of eye conditions causing non-inflammatory damage to the retina (eg. retinal detachment, diabetic retinopathy, hypertensive retinopathy). This usually occurs due to co-occurring cardiovascular condition such as diabetes or high blood pressure.

Rhodopsin: light sensitive pigment found in photoreceptors allowing for the perception of night vision. After exposure to white light, it usually takes 30mins to fully recover.

Sebum: thick substance consistent of fat which coats the eye for lubrication and protection.

Steroids: group of substances that share similar chemical make-up, most of which have significant biological activity. Eg. Progesterone, oestrogen, testosterone.

Strabismus: (Squint) a disorder of vision in which one eye cannot focus with the other on an object due to a lack of muscular coordination. Strabismus involves deviation of the alignment of one eye in relation to the other.

Tuna fish (oil): highest quality fish oil comparatively rich in DHA, essential for eye and brain development and maintenance.

Uniocular: 1. Relating to one eye only. 2. Having vision in only one eye.

Visual field: the image of the world in front of the eyes that can be perceived by the brain.