Glossary

Ultra violet (UV) light
 Ultra violet light (UV) is a type of sunlight which is invisible and has a damaging effect on the eyes. UV radiation is particularly dangerous as it does not directly stimulate the sensory nerves and symptoms are delayed for between six and twelve hours. UV is measured in nanometres (nm) and is divided into three categories:

  • UVA (315-380nm) dangerous - causes ageing of the eye
  • UVB (280-315nm) dangerous - causes sunstroke
  • UVC (~100-280nm) very dangerous to the eye - but filtered by the ozone layer

Glare
Glare is light which is reflected from a surface. This reflected light is partially polarised and at certain angles becomes completely polarised. Glare causes eyestrain and discomfort. It increases brightness and reduces colour saturation making objects appear washed-out. Glare is a particular problem around water, snow and wet road surfaces. In these situations reflected light can be very hazardous as it multiplies the amount of UV light striking the eyes, with sand reflecting 17% of incident light, water 60% and snow 85%.

Polarised
In direct light the waves of light circulate in all directions – this is termed ‘diffused light’. Reflected light is ordered in parallel lines – this is termed ‘polarised light’. Polarised lenses effectively block reflected glare. This means that lighter tints can be used to achieve the same degree of glare reduction compared to non-polarised lenses.

Photochromic
Photochromic lenses darken in bright sunlight and become paler in less intense light conditions. These lenses are ideal in variable light conditions or when moving from areas of shade into sunlight.

Mirrored
Mirrored lenses have a reflective metal oxide mirror coating on the front or on both the front and back of the lens. This further reduces the amount of light transmitted through the lens to the eye and mirrored lenses are ideal for very sunny days with strong reflected light.

Rx-able
This is the term used by Optometrists to indicate that the eyewear can support prescription lenses. In Sport sunglasses this is either by having a prescription insert clipped behind the sunglass lenses or some frames can support prescription lenses directly into the frames of the sunglasses. At the moment, Sport Spex does not offer an Rx-ing service. We do, however, supply the optical inserts and Rx-able sunglasses which you can simply take along to your optician to have your prescription added. For single vision lenses this usually costs around £50-60

Sport Optometrist
An Optometrist examines your eyes and related structures for health and vision disorders and treats vision problems with spectacles and contact lenses. A Sport Optometrist has an additional qualification in Sport related eye care. This means not only dealing with eye problems encountered by Sport people but also advising on eye injury prevention and optimal eyewear for Sport participation.

Image distortion
Image distortion can occur with some Sport eyewear due to the increased curve of the lens in the wrap around styles that are popular with Sport people today. The increase curve means that the lenses are no longer parallel to the ‘axis of vision’ which is the imaginary centre of the lens zone in which vision undergoes no distortion. This means that the image appears distorted and causes headaches, eye fatigue and even eye damage. All Rudy Project sunglasses supplied by Sport Spex have lenses which are technically designed to eliminate image distortion guaranteeing a wider ‘viewing’ area.

Visual acuity
Visual acuity represents the quality of the perception of human vision. It is often termed 20/20 (or 6/6) vision. It assumes the ability to read a standard sized letter at a standard testing distance of 20 feet or 6 metres.