ON USING SMOKED GLASSES FOR THE EYES.

Feilding Star, Issue 758, 19 December 1908, Page 2

ON USING SMOKED GLASSES FOR THE EYES.

TO THE KDITOB OP THE STAB. H Sir, —As it is commonly supposed by those having no knowledge of optics that the wearing of "smoked glasses" during the heat ofj summer is beneficial to the eyes, " would" you kindly allow me to sound a note nt~ warning through the medium of columns. It is quite true that "smoked or tinted" glasses having no refractive power are useful to person's having an extra sensitive retina (inside back of the eye). This usefulness' ie due to the fact that rays of light known as •'irritant rays" are prohibited by the smoked glass from entering the eyes, but the same glass should not possess any refractive or light-ray bending power. During the past few weeks quite a few persons nave mentioned to me that the "smoked glasses" they*" were wearing seemed to be "drawing" or otherwise injuring their eyes. On examination of the glasses I found that they possessed, refractive power, which accounted for the annoyance. This refractive power ex^tends the focussing point, and. sets up a need for an extra amount of accommodation, or ciliary muscle powder within the eye, and actually produces more trouble than the one intended to be avoided, and may, if persistently worn, do considerable damage. If any persons wearing such glasses care to bring them to me I should be pleased to examine arid say whether they are safe to wear or not, —Yours truly, G. W. Hean, Chemist and Optician. *- P.S.—-Perhaps it is only fair to state that "smoked" or other tinted glasses sold by me do not possess refractive power, unless actually intended to neutralise some defect in addition to the stopping of irritant light rays.—G.W.H.