Vision ∙ Vue ∙ Vista ∙ Syn ∙ зрение ∙ 视力
Jens G. Hetland, Professor, MD, Ph.D, Oslo, Norway
Sponsored by Arthur and Odd Clausons Legacy for vision and eye care
for people who want to study visual acuity and visual fields interactively

Syn for alle - On Tonometry - Experimental Tonography

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When the muscles, responsible for changes in the thickness and power of the lens, are in the relaxed mode, the hyperopic person cannot see clearly, neither at distance nor close-up, because the eye is too short, (other factors might also have an effect upon the refraction). When looking at distance, the incoming rays are parallell; when reading, the incoming rays are divergent. In hyperopia both parallell and divergent rays are carried to focus behind the eye, that is behind the macula! Therefore the images are blurred.

In order to see clearly, the thickness and power of the lens has to be increased by means of the process of accommodation, and bring the focus forward to the macula. Thus, the accommodation muscles will always be in an activated state, and some of the accommodative power continuously in use! That is the negative side of hyperopia.

The tests are for educational purposes only to illustrate hypothetical cases
This site was last updated 15 March 2010