Eye glasses : Eye vision correction
Eye glasses:-
Eye glasses are the artificial optic materials used to improve eye sight, to correct defective vision, and to add capacity to weak eye sight.
Eye glasses also provides protection from dust particles, sunlight, ultraviolet rays, flying objects, and prevents damage to eye.
As we have two eyes, eye glasses are two and which are made up of glasses or fibre material, which are attached to frame.
The frame with two eye glasses is placed on the ridge of nose and two arms of frame are fixed to narrow region between ears and head.
Materials used in eye glasses:-
Eye glasses are made from high tech materials. The standard material used is glass, but now a days polymer materials are emerged such as CR39, polycarbonate and high index plastic.
Multi focal lenses are the lens contains two are more vision correcting prescriptions in a single lens.
Bifocal lens contains split lens, the upper part is used for distant vision and lower part is used for for short vision.
Different eye glasses are different for different for different individuals according to vision disturbances.
There is option of eye glasses for individual needs as per one’s convenient.
Full spectrum of eye glass lens tints are also available. ranging from lighter tints to darker tints.
Working of Eye glasses:-
Eye glasses correct mainly four vision disturbances.
Myopia or shortsightedness :- this causes far objects to appear blurred and nearer objects can be seen clearly. Concave lenses or concave eye glasses are the corrective eye glasses used to correct short sightedness or refractive errors. These concave corrective lenses makes the image of far objects to fall behind the retina and helps in clear visualisation of far objects and corrects short sightedness.
Hyperopia or long sightedness : is a vision disorder characterized by far objects are seen clearly but near objects seeing is difficult. Convex lenses or concave eyeglasses are the corrective eye glasses used to correct farsightedness by making an image of far objects to fall in front of the retina. Hence These eyeglasses corrects refractive error of farsightedness.
Astigmatism:- is a vision disturbance caused by non uniform curvature in the refractive surfaces of the eye. The external light rays do not fall on one focal point on retina, instead fells behind or in front of the retina. The person may experience both short and long sightedness.
Specially made eye glass , cylindrical glass is placed in lens to correct this vision disturbances.
Presbyopia :- is a disorder occurs when natural crystalline lens fails to change it’s shape to accommodate vision. Is corrected by using bifocal eye glasses.
