| Show spectacles A NECESSITY I 1 IT is a general idea among the people that the human eye is a perfect optical organ while in point of fact an absolutely normal eye is 18 a rare exception this very beef explanation may be helpful to some whose sight is not all that is desired there are two distinct and diametrically opposite conditions of the eye due to its ito anatomical construction or far sight eight and myopia or near sight or old sight la in caused by a hardening of the lens which commences at the tenth year and gradually increases as the individual grows older it is incident in certain degrees to both refractive conditions dit ions an eye may have different degrees of far sight in different meridians of the same eye A nearsighted eye may be affected similarly an eye may be farsighted far sighted in one meridian and nearsighted near sighted in another of the same eye these conditions are called astigmatism and considerable patience and skill are required infesting in testing the eye to find the proper glasses to correct the error spectacles can correct optical errors only no glass can benefit the vision if the loss is due to disease of any part of the eye distinct vision depends upon the exact adjustment of the local point of the refractive media upon the retina which to is the perceptive layer this result to Is the whole object in fitting and wearing refractive glasses A or farsighted far sighted eye is so called because the nearest point of distinct vision is farther from the eye than is normal its antero pos perlor diameter is shorter than the local distance ot of its refracting med media and the retina lies within the focus A double convex or condensing de nging lens of greater or less power is required to assist the natural ural lens to shorten its focus and bring it on to the retina this kind of refractive defect requires the wearing of presby ople or old sight glasses earlier than either the normal or nearsighted near sighted eye it is often a very hurtful mistake to delay the wearing of glasses as long as possible properly fitted glasses are beneficial just as early aa 00 rafOrt and ease ease in the use of the ea yea and distinct vision require the them high degrees of trop dropla require ulm glasses to be worn all the me time anae even by very young children it Is Ini mistaken staken sometimes for near nearsightedness sightedness because 64 acts are held roseto close to the eyes before vision is distinct A myopic or nearsighted near sighted eye is erroneously thought by many to be a very strong eye it is essentially a weak eye and generally grows worse myopia may be acquired by long log continued use of the eye on close objects statistics show its increase berease Oe rease to hold a close relation to the higher intellectual attain attainments ants of a people or nation the axis of the eye is too long the retinal is behind the focal point of the refracting fr acting media hence a concave or persing glass is required to throw the th focal point further back low degrees of myopia need glasses only tw for distance but high degrees require them for reading also if the patient is a musician or artist a glass must be adjusted for the deed adred distance of low de creft may in old age need a convex glass but in certain degrees never r need old sight glasses eduse because they make use use of their far point pint in ila all near work mo more re complicated and difficult cases both for testing bating the eye and in grinding tai the ga glasses are those described above as ism here two glasses will have to be combined each correcting ing a 4 meridian of the eye separate lav V one of these glasses is called cylindrical because it is a section of a c cylinder and corrects only in one raer in idian spherical glasses correct au aal meridians af afan eye ye is more myopic in one than another a concave bunder Is ig combined with a con cave spherical in some cases two cylinders at right angles answer best astle astigmatism e is corrected in the same way u using ng convex glasses when the same eye is both nearsighted near sighted and farsighted far sigh sighted at the same time concave and convex n glasses must be combined one i or both being cylinders when n the natural lens has become opaque it is called a cataract it lies immediately behind the pupil causes it to look white and as completely obstructs the ingress of the rays of light into the eye as a curtain drawn down over a window no glass can help the sight in this condition after the cataract is re moved wong strong convex glasses a pair for distance and a pair for near frequently restore the blind once more to see the faces of his friends and his books colored glasses blue or london smoke the latter being preferable are non refractive and are used only as protectors to weak or sore eyes ROMANIA B M D deseret hospital |
