Influence of ophthalmic lenses in the illuminance originated at a peripheral glare source and reaching the eye

SILVIANA COMASTRI; JULIANA MATRANGA; KARINA BASTIDA; LUIS ISSOLIO; ELISA COLOMBO

Optics

Elsevier Gmbh, Urban & Fischer Verlag

Lugar: Alemania; Año: 2009 vol. 120 p. 860 - 872

0030-4026

To study the influence of glare on the visual performance of a subject wearing an ophthalmic lens, it is useful to know how the lens affects the illuminance reaching the eye. In this paper, considering spherical standard ophthalmic lenses and defining the relative illuminance, Er, as the quotient between the illuminance at the cornea with and without lens, a methodology to evaluate Er in terms of easily determined parameters is developed. Three effects are considered, pupil size variation of the system with and without lens; lateral shifts of rays transmitted through the lens and reflections at the lens. Calculations are experimentally verified employing 5 organic ophthalmic lenses of ±6; ±4 and 0.12Dioptres and 2 glass plane parallel plates 1.95mm and 6.6mm thick. Using a photometer whose sensor is 12mm apart from the lens and 740mm apart from a glare source subtending an eccentricity angle of 9.6o, it results Er=1.204 for the 6Dioptres lens and Er=0.803 for the -6Dioptres one if sensor diameter is 10mm while, for a 719mm distance and a 10o angle, Er=0.922 for the thin plate and a 30mm sensor and Er=1.006 for the thick plate and a 10mm sensor. Experimental and theoretical results differ in less than 3%.