Phoria Tests and Calibration

The word "Phoria" is an abbreviation of "hetero-Phoria" which means "latent squint". A person suffering from this condition has a tendency for the eyes either to turn inwards (eso-phoria) or outward (exo-phoria) or for one eye to tend to move upward relative to the other eye (right or left hyper-Phoria). Such persons frequently suffer from excessive fatigue or so called "eye strain" particularly when performing concentrated eye tasks such as driving, close work, use of VDU equipment etc. the condition can often be corrected with prismatic lenses.

In relation to the NRK Medical record form, people should be referred for a full eye examination if their 'Phoria' results are scored in the lighter grey shaded area of the record form, which would indicate that their defect is greater than what one normally would expect to be on-goingly tolerable without causing some form of symptoms.

An inherited condition most commonly seen in men. It is caused by a deficiency of certain "cones", or colour detectors, in the eye.

Approximately 8% of male & less than 1% of female population are born with an inherited type of colour blindness known as "red-green" colour blindness, called "Colour Severe" as more colours are made of Red/Green mixtures.

Also 1% of the population, nearly all males, suffer from "blue-violet" colour blindness. Also called "Colour Mild".

There is NO treatment at present for colour blindness nor is it usually the cause of any significant disability.

The accuracy of test results inter-alia is dependent upon:

• The optical power and position in the instrument of the viewing lenses.
• The design of test target slides.
• The position of the eight-sided drum inside the instrument on which the target slides are mounted.

All these components are "fixed and non-variable" both in construction and operation.

The correct position of the viewing lenses and the target drum are pre-set at manufacture and securely fixed.

Therefore NO routine re-calibration of these instruments is required, unless the unit has been tempered with or mishandled.