As a layman, it is not easy to evaluate the quality of your lens at home without consulting professionals. However, you might as well try an evaluation at home by following a careful step by step process.
– Hold the glass lens a minimum one foot away from the eye and then look at some distant and stationery object like lamppost or something else.
– Try and move the glasses from one side to another.
– If the view of the distant object in the lens is unclear and interrupted by breaks and irregular waves, then you know that your lens is of a poor quality.
– Also note if there are scratches or pits on the surface of the lens. This might be caused either by poor polishing methods or small accidents. Though apparently insignificant these might lead to problems with vision if not corrected.
– The junction of the bifocal section of your spectacles is a part you ought to carefully observe. Not only should the lines here be clear and sharp but also there should be equality between the size and shape of the segment from left to right. In case there seems to be a visual coloring it is a sign of poorly fused bifocal blank.
– The fitting of the lens into the frame is done by what is known as technical glazing. The edge of the lens hence should be at its thinnest and should fit perfectly into the frame without any gap.To check if your lens has poor glazing you can slide a piece of paper at the edges and see if it passes.
The various kinds of lenses are:-
– In the special asferic kind of design the lenses correction is in the center. Since the distance correction is in the central zone, therefore if you are uncomfortable with the design you can always get a reversed one through a consultation with your doctor.
– The concentric design lenses are the most common types. In this type the inner lenses are responsible for distant vision or the other way round. Other kinds like the translating design have the distance correction above the nearness correction center. Distinguished by a fine line, the lenses don’t shift even when you blink because their bottom is totally flat.
– If the lenses are of the monovision kind then while one lens has nearness correction, another one has the distance correction lens. In this case, you need to know which is your dominant eye. A consultation with the doctor can tell you that and accordingly you should be wearing the distance correction in that eye.
– Another kind of lenses is the simultaneous ones through which you can focus on both near and far objects simultaneously. The lenses for nearness and distance corrections are placed in concentric circles. The reflections of light from near and distant objects reach your eyes and help you to focus at both at the same time.
Today thanks to advancement in technology, researchers are trying to use bifocals to replace all the cumbersome methods of limited vision. Innovative designs are shaping the new materials available and thus this way each and every lens can be specifically designed to cater to everyone’s requirements. One of the latest products from the optic stable is a liquid crystal layer fitted between two glass substrates. The varying power of the lens can be changed by changing the refractive index with the help of electricity.