Following your advanced or comprehensive examination, there may be some of these further tests listed on your eye examination report. We do not perform every test on every person, instead your optician will decide which tests are necessary based on your symptoms and history.
Visual Field Testing
Your visual field is the area that is covered by your peripheral vision. In testing this, the sensitivity of your eyes is compared, at a range of points, to that of an average person your age. Reduced peripheral sensitivity can occur for a number of reasons which will generally result in referral for specialist investigation.
FDT Field Testing
Frequency-doubling tests of the peripheral vision utilise oscillating targets, which test the function of a different receptor in the retina compared to static targets. These receptors are thought to be affected earliest in Glaucoma, so FDT tests are more sensitive then traditional methods in detecting early cases.
Tonometry
The fluid pressure within the eyes can be measured with a variety of instruments, either contact-tonometers which, after the instillation of a local anaesthetic drop, rest gently on the front surface of the eye, or non-contact-tonometers, which measure the resistance of each eye to a puff of air. High pressure in the eyes is a risk factor for developing Glaucoma.
Amsler Charts
These charts, which are similar in appearance to squared paper, are used to assess the function of the macula region of the retina. Certain eye conditions, such as macula degeneration and diabetes can cause distortion to the tissues in this region, which lead to a reduction in vision.
Slit-lamp Microscopy
This microscope, mounted horizontally, allows a magnified view of the eyelids and front section of the eye. It is especially useful in the fitting of contact lenses, suspected foreign bodies in the eye and evaluation of the causes of dry eyes. It can also be used in combination with a tonometer or an additional lens to enable viewing of the retina (see : indirect ophthalmoscopy).
Fundus Photography
Advancements in camera technology now allow digital photographs to be taken of the retina, the membrane at the back of the eye with which we detect light. These photographs give a far superior view of the retina, and can be compared to previous years' for accurate monitoring of the progression of eye conditions such as diabetes, glaucoma and macula degeneration.
Indirect Opthalmoscopy
An ophthalmoscope is a device for examining the inside of the eyes to check for defects. Indirect ophthalmoscopy, either with or without the instillation of drops to make the pupils larger, allows for a larger area of the retina to be viewed at one time and also permits a binocular view of the retina so that structures can be observed in 3D.
Keratometry
The cornea, which is the clear tissue covering the front of the eye, can vary in shape from person to person. Measurement of the shape of the cornea is performed using a keratometer, and is often done as a first step in the fitting of contact lenses, or to monitor the progression of diseases such as keratocconus.
Orthoptics
An orthoptic assessment consists of various tests to measure how well the eyes work as a pair to provide clear and comfortable binocular vision. Should any problems be found, these may be alleviated using either eye exercises, the addition of prisms to a spectacle prescription, or referral to a specialist where necessary.
Colour Vision Testing
Colour vision deficiencies (sometimes incorrectly called “Colour Blindness”) affect approximately 1 in every 8 males, and a much smaller proportion of females. This can cause difficulties with recognising certain colours, essential for working in certain occupations, for example the navy and fire service and also lead to confusion of similar colours, which may lead to educational difficulties.
Intuitive Overlays
In patients with dyslexia, it has been found that certain coloured tints cause the print on a page to be more stable, and therefore easier to read. Using a selection of coloured overlays, we can assess the colour that is likely to have the greatest effect, then prescribe reading lenses with a tint to match.