by Shane Scourfield | Dec 12, 2016 | Technical Information
* Denotes separate entry ABERRATION CONTROLLED LENS: Contact lens to improve visual performance by the control of spherical aberration, usually by means of an *aspheric front surface. Sometimes beneficial for early presbyopes. AESTHESIOMETER: Instrument for measuring...
by Shane Scourfield | Dec 6, 2016 | Technical Information
Presbyopia shows itself when reading and near vision become difficult and close objects need to be held further away. It is not a disease and typically occurs from about 45 years of age when the muscles within the eye are no longer able to change focus to see close...
by Shane Scourfield | Dec 6, 2016 | Technical Information
The normal cornea – the front surface of the eye – has approximately the same spherical curvature in all meridians. Astigmatism is usually the result of distortion of the cornea with steeper curvature in one meridian and flatter curvature in the opposite...
by Shane Scourfield | Dec 6, 2016 | Technical Information
In long sight the eye is relatively too short and rays of light are focused behind the retina. In younger people this can be corrected by adjusting the focus with the muscles within the eye. Depending on age, distance vision may therefore remain good but near vision...
by Shane Scourfield | Dec 6, 2016 | Technical Information
In short sight the eye has grown to be relatively too long so that rays of light are focused in front of the retina. Distance vision is therefore blurred while near vision remains good. The unit of measurement is the dioptre (D) and will appear as the sphere (sph) on...