The term ‘reading glasses’ is used for glasses which are used for near work including reading. The power of the lenses in the reading glasses may exclusively be only for near work or the glasses may have lenses for both distance and near work (bifocal or progressive reading glasses).
Why do we need reading glasses?
In children and young adults, the natural lens in the eye is more elastic and has the ability to change its shape – less curved and more curved. A less curved (flatter) lens has less light bending power (less refractive power). A more curved lens can bend the light rays more and therefore has more refractive power. This ability of the natural lens of the eye to change its shape to focus the incoming light rays on the retina is called as ‘accommodation’ and is explained in the animation below.
As we age, the lens in the eye becomes harder and the elasticity of the lens decreases gradually. This condition is called as presbyopia. Around the age of 40 years, it reaches a critical level when an adult starts feeling difficulty in seeing objects at close distance clearly. This is when the person needs corrective glasses which are plus (convex) lenses.
With further aging, the power of the lenses gradually increases generally and may go up to +3.0 diopters till the age of 60 years.
Click here to read more about presbyopia.
How reading glasses work
As mentioned above, presbyopia is corrected with plus/convex lenses in the reading glasses. These lenses do what the natural lens of the eye cannot do – they focus the light rays on the retina for the near objects to be seen clearly. In the absence of reading glasses, the light rays focus behind the retina and the image of near objects is blurred.
Types of reading glasses
Single vision glasses
A single vision lens has the same corrective power in the entire lens. It does not have any additional power for distance or intermediate vision. The area of the lens through which the eye looks at the near object is large and therefore the comfort level with single vision reading glasses is higher.
Bifocal reading glasses
Bifocal glasses have a lower segment for near vision and an upper segment for distance vision. The demarcation line between them is usually visible. The segments for near and distance vision are smaller as compared to single vision glasses. The user as a result has to align the glasses along the visual axis and adjust the head position to look through the desired segment.
Progressive reading glasses
Progressive lenses have power for near vision in the lower part and the power progressively changes to the one meant for distance vision in the upper segment of the lens. This implies that there is no demarcation line and that there is a transition zone which helps correct intermediate vision.
Computer glasses are an example of intermediate vision – the distance which is neither near nor far. People who work on computers for long durations consistently may need such glasses to see clearly and avoid eye strain.
Do you need reading glasses after LASIK eye surgery?
The answer is yes and no! In a standard LASIK laser procedure, the eyes are corrected for distance vision especially in young adults who do not have presbyopia. Individuals 40 years and above who are corrected for distance with LASIK do need reading glasses.
In selected patients however, one eye can be corrected for distance and the other eye can be corrected for near. This approach is called as monovision. Usually the dominant eye is corrected for distance and the non-dominant eye is corrected for near.
Some individuals are not comfortable with this solution as they complain of blurry vision in one eye. On the other hand, some people quickly adapt to monovision. The big advantage for them is that they don’t need any reading glasses.
Do you need reading glasses after cataract surgery?
Again, it depends. In a standard cataract surgery with standard intraocular lens (IOL) implantation, you will most probably need reading glasses.
But there are some options available such as accommodating IOLs and multifocal IOLs which if implanted will provide excellent distance as well as near vision. Apart from this, cataract surgery can also be combined with other refractive surgery or laser surgery to produce monovision and minimize or avoid the use of reading glasses.
Where to get reading glasses?
It is important to know that the power of your reading glasses is usually the combination of distance correction plus near correction. Your reading glasses are not simply ‘near vision glasses’. That is the reason you should avoid buying your glasses without a proper eye examination by an optometrist or ophthalmologist. A ‘test’ with borrowed glasses from someone will probably not help you in the long run.
Once you know your prescription (reading glasses strength), you can then decide whether you need single vision, bifocals or progressive glasses. A lot depends on your visual needs and the nature of your work. Some individuals have to try many types of reading glasses before they know what suits them best.