Spectacles for Presbyopia

Starting around the age of 40, we loose the ability to see objects at very close distances. We might first notice this when we have difficulty in reading the small print  on our medicine bottles or legal documents. As we grow older near vision will slowly become progressively more blurry, but distance vision will not be affected. This inability to see near objects is called presbyopia.

We have two types of spectacles to help people with presbyopia see near objects. These are Bifocal and Progressive lens. The major physical difference between the bifocal lens and the progressives lens is the demarcation line between the area used to see far and area used to see near objects. The main functional difference is that bifocal has only two focal points, while progressive has many.



Bifocal as the name implies have two areas of focus- the top portion for distance and the bottom circle for near. The reading power can be titrated to the distance that the person requires. For a person who read books in his hand would need the focus to be at 20-30 cm, while if he reads with the paper on a desk while he leans back the focal distance would be 3-40cm. If he requires to see both near and intermediate objects/ print then he has to opt for a progressive lens.

The reading segment can be round, D shaped or a flat line as in executive bifocals. Round shape is most comfortable while D shape gives more area for distance. Executive bifocals have large area for near for people who read a lot.

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Progressive glasses are also known as varifocal, graduated glasses and no-lines bifocals.  These lenses have more than one focal point or lens power with different powers at different levels of the lens. At the top of the lens, the power is minimum, which gradually increases in the middle level and finally, the bottom part of the lens has the maximum power. 

Commercially, progressive glasses are quite popular because of the absence of any line on the lens. The greatest advantage of progressive glasses is the ability to look at objects at varying distances with just a slight tilt of head. As the different levels have different powers, the top part can be used to view objects at a distance, the middle one at the objects at an intermediate distance and the bottom part while working on the nearby objects, like reading a book. They also avoid the discontinuities like image-jumps which occur in the visual fields created by bifocal and trifocal glasses. 

Links 

How to choose a spectacle frame

Computers and the Eye.
Getting used to progressive lens.

Choosing a Spectacle frame

The most important factor to consider when choosing a new frame is the fit of the frame. It doesn't matter how good a frame looks if you always have to push it back up your nose. Make sure that the frame fits the bridge of your nose without slipping down, remembering that the finished spectacles will be heavier than the frame when you try it on.

The frame should not rest on your cheeks. Try smiling while you are trying on the frame - if it rides up, then it is sitting on your cheeks, not your nose.

A frame should also suit your lifestyle. If you are very active, or wear your spectacles while exercising, then a smaller frame may be better, since your spectacles will be less likely to fog up than if they have a large, close-fitting frame.

Re-Using Your Frames

Re-Using your own frame can be a good alternative to searching for another frame that suits you, or spending a lot of money on a new frame when your budget is a little low. 

But before considering this there are a few things you should bare in mind. Plastic frames must be heated and stretched to insert new lenses. Because the resins used in plastic frames tend to become hard and brittle with age, there is a high risk of breakage when you re-use an old plastic frame, regardless of how much the frame cost when you bought it, or which manufacturer made it.

A progressive lens requires perfect centration for an ideal fit. An old frame might have slight distortions and a perfect fit might not be possible. It is best not to reuse a frame to fit a progressive lens. 

Contact Lens: Use and Care

The contact lens is a plastic film which floats in front of the cornea on a thin film of tear. It corrects refractive errors of the eye. It is applied onto the eyes in the morning and removed at night.

It has several advantages over spectacles: The patient will have a wider field of view with contact lens. There will not be any steaming. There is no restriction of activity while using contact lens. Patients with high power glasses will have better and sharper vision with contact lens.
Disadvantages of contact lens

Once the Contact Lens are placed over the eyes, there will be increased tearing, lid irritation, excessive blinking. It is a matter of getting used to an unaccustomed set of sensations. By the end of one week the contact lens wearer is usually no longer aware of the lenses on his eye except when he thinks about it.

About the only real disadvantage in wearing contact lenses is the process of getting used to them. Once the wearer has become accustomed to all day use of contact lenses, he will find it difficult to name any disadvantage of importance.

Care of your Contact Lens

* Cleanliness cannot be over emphasized. Always wash your hands before putting on or taking off the Contact Lens.
* Do not rub your eyes when Contact Lens is in your eyes.
* When in doubt about anything contact us immediately.
* Insert the Contact Lens before shaving or applying facial creams or make-up.
* Remove contact lens before removing make-up.
* You can use a pencil eye liner. Apply it just above the upper lashes and just below the lower lashes. Never apply eyeliner to the inside rim of the eye.