Glossary of Terms

The following explanations are intended as a general description of terms you may encounter from a visit to your Optometrist. If you are in any way concerned with the condition of your eyes, you should seek out medical assessment.

  1. Anti-Reflection coatings
    A coating on the lens surface to enhance the visual performance and cosmetic appearance of your spectacles.
  2. Astigmatism
    A refractive error in your prescription, caused by an ovalisation of the cornea or crystalline lens, that results in a ‘ghosting’ of your vision.
  3. Bifocal Lenses
    Provide clear vision at two ranges, generally far and near, with a visible dividing line between them.
  4. Cataract
    Opacity of the crystalline lens inside your eye.
  5. Cornea
    The clear front surface of the eye.
  6. Conjunctiva
    The tissue surrounding the cornea, extending over the ‘white’ of your eyes to line the inner surface of your eyelids.
  7. Conjunctivitis
    Inflammation of the above tissue.
  8. Diplopia
    A condition where objects are actually seen double – not to be confused with the ‘ghosting’ effects that can be seen with astigmatism.
  9. Glaucoma
    Damage to the optic nerve caused by multiple factors, including changes in intra-ocular pressure. Increasingly common in the over 40 age group and often symptom free in the early stages. Symptoms include peripheral field loss, tunnel vision and (if not treated early), blindness. Regular eye examinations are recommended when you exceed 40, as advancing age and family history increase the risk of developing this condition.
  10. High Index Lenses
    Spectacle lenses made from denser glass or plastic materials, resulting in thinner designs – generally used for high prescriptions only.
  11. Interview Lenses
    Specialised spectacle lenses for close work that have an extended design to incorporate reading and VDU distances.
  12. Iris
    The coloured part of your eye, which changes the size of your pupil to regulate the amount of light entering your eye.
  13. Laser refractive surgery
    The permanent re-shaping of the cornea to eliminate myopia (short sightedness), and to a lesser extent astigmatism and hyperopia (long sightedness), by the use of a laser.
  14. Macular Degeneration
    A common degenerative condition that affects the central, macular area of the retina in the over 60 age group. Divided into 2 common types: dry macular degeneration (slow to develop and not currently treatable) and wet macular degeneration (rapid onset and treatable if diagnosed early).
  15. Myopia
    Near-sightedness causing distant images to be out of focus.
  16. Multi-focal lenses
    Spectacle or contact lenses with more than one refractive correction allowing a clear focus at all distances.
  17. Optic Nerve
    Made up from the nerve fibres of the rods and cones of the retina, the Optic Nerve conveys visual information from the eye to the brain.
  18. Orthokeratology
    The process of re-moulding a cornea to eliminate myopia (short sightedness), by the wearing of a specially designed contact lens overnight. Completely reversible on cessation of lens wear – unlike laser surgery where the effects are permanent.
  19. Polarised Lens
    A spectacle lens designed to cut out annoying reflections from surfaces.
  20. Polarised Light
    Light that is reflected off a flat surface.
  21. Presbyopia
    A gradual loss of lens flexibility with age, making it increasingly difficult to focus on close-up tasks. Correctable by spectacle or contact lenses.
  22. Pupil
    The aperture in the centre of the iris that allows light through to the retina.
  23. Retina
    The layer of light receptors at the back of the eye.
  24. Single Vision Lenses
    Spectacle or contact lenses that allow viewing at only one distance eg. Distance glasses or reading glasses.
  25. Sports Vision Eyewear
    Corrective eyewear used for sports.
  26. Trifocal Lenses
    A multi-focal lens divided into distance and near sections, but also incorporating a mid distance section for viewing objects at arms length. A visible dividing line separates each section of the lens.
  27. Varifocal Lenses
    A specialised type of multi-focal lens that shows a smooth, invisible transition between the various sections allowing a clear focus at all distances.
  28. Occupational Lenses
    A specialised blended lens similar to varifocals. Usually used for computer and reading but can have various uses in and out of the office.
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