What is Presbyopia?

Presbyopia is a condition of the eye where a progressive loss of magnification ability results in the inability to see near objects.

What causes it?

Presbyopia is caused by the hardening of the crystalline lens of your eye and occurs in a predictable fashion as a result of the natural process of aging.  The first symptoms of presbyopia normally occur between ages of 40-50 and the ability to focus on near objects continues to decrease.  In fact, if your eyes have a distance prescription of zero (“plano” in ophthalmology terms), you will first need reading glasses very predictably at 42 or 43 years old.

What happens if I have…

Myopia (nearsightedness) and Presbyopia?

If you’re myopic, as you age, you lose the magnification power of your lens just like any other person.

If you’re over 42 and wearing single vision distance contact lenses, you’ll notice that you have to hold things farther away when you’re wearing contact lenses for distance and trying to read, or that you need reading glasses on top of your contact lenses to see well up close.  You’ll also notice your presbyopia when you’re wearing glasses and have an irresistible urge to take them off to read.

Hyperopia (farsightedness) and Presbyopia?

If you’re a latent hyperope (person with farsightedness who doesn’t need glasses for distance until they get older), at a young age you probably had the best distance vision out of all of your friends.  However, as you get older, you need reading glasses far earlier than most people in your age group (even by your late 30s).

Here’s how it works:  hyperopes who don’t wear glasses in the distance are using their magnification power just to see far.  As you age, the lens in your eye becomes less flexible, decreasing its ability to magnify.   So, you’re a latent hyperope in your late 30′s  sitting in a chair, looking at the beautiful view, using most of your magnification power just to see far.  Now, you pick up something to read, and whammo!  It’s blurry.  This scenario happens earlier to untreated hyperopes than myopes (nearsighted people) or emmetropes (people who have no need for prescription in the distance) because their accomodation (ability to magnify) is already used up from looking far, and there’s not as much left to magnify to read.   Eventually, when the hyperopia is high enough or you get old enough, combining hyperopia and presbyopia blurs both your near vision and your distance vision.

What are the possible treatments for my eyes?

Bifocal spectacles – The most common type of bifocal spectacle is the Flat Top Bifocal and is comprised of two segments: one for far vision and one for near.  The segments are available in different sizes according to the field of vision you need to see.  The other bifocal “with line” spectacle style is the Executive Bifocal.  The lenses are also split into two segments, with a dividing line across the width of the lens.  They do not allow for a continuous range of vision and sometimes cause blurriness.  A third type of bifocal is the progressive or “no line” bifocal.  This is the type people are wearing when you see them bobbing their heads and looking for the sweet spot in their spectacles for focusing at that exact distance.

Monovision contact lenses – With monovision contact lenses for presbyopia, each eye is treated differently.  One eye (most commonly the dominant eye) is corrected for distance vision and the other eye is corrected for near vision.  Ideally, your brain will choose the magnified image and provide your eyes with what appears to be continuous, smooth vision.  However, Monovision contacts can sometimes cause a loss of depth perception which patients find difficult to adapt to.

Monovision LASIK or PRK – LASIK or PRK surgery is used to permanently correct one eye for near vision and the other eye for distance vision.  Monovision after LASIK or PRK tends to be better accepted by patients than contact lens monovision because the patient’s visual experience is the same all the time.  During LASIK surgery, a flap is created on the surface of the cornea (the front layer of the eye).  A laser is then used to re-shape the cornea back into a natural shape so that it focuses light more efficiently, and then the corneal flap is put back in place.

During PRK surgery, the surgeon removes the epithelium of the cornea altogether, and after the procedure, bandage contact lenses are worn to help in healing the epithelium.

About 10% of presbyopic patients prefer single vision distance correction over monovision.  I spend a great deal of time and care getting your prescription right (this includes whether to go with Monovision or not) and if so, the right amount.  I spend a significant amount of time learning about your daily activities and do my best to simulate your results so that you will be thrilled with the end product.

Most people find that they can adjust to Monovision LASIK or PRK far easier than contacts because the correction is 24/7, without the hassle of taking out and putting in contact lenses.  For the remaining 10%, single distance vision after LASIK or PRK with “drugstore readers” is an excellent choice.

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Sources:

http://www.seewithlasik.com/docs/presbyopia/presbyopia.html

http://www.pendletoneye.com/errors.htm

http://www.webmd.com/eye-health/tc/farsightedness-hyperopia-what-happens

http://www.docshop.com/education/vision/refractive/monovision/

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