Presbyopia

Presbyopia is an eye condition in which your eye slowly loses the ability to quickly focus on objects that are close. It is a disorder that affects everyone people during the natural aging process of their eyes.

When light enters the eye, it passes through the cornea and then through the pupil. The iris, the colored ring in your eye, opens and closes the pupil to adjust the amount of light passing through it. It then passes through the lens. In its healthiest state, the lens changes shape so it can bend the rays further and focus them on the retina at the back of the eye. However, with age, the lenses of your eyes become less flexible and can’t change shape as easily. As a result, the lens is unable to bend the light properly to focus it on the retina.

When you’re young, the lens in your eye is flexible and relatively elastic. It can change its length or shape with the help of a ring of tiny muscles that surround it. The muscles that surround your eye can easily reshape and adjust the lens to accommodate both close and distant images.

With age, your lenses and the muscle fibers surrounding the lenses slowly lose flexibility and stiffen. As a result, your lenses become unable to change shape and constrict to focus on close images. With this hardening of your lenses, your eye gradually loses its ability to focus light directly on to the retina.

The most significant risk factor for presbyopia is age. Most people lose some ability to focus on close objects by age 40. It affects everyone, but some people notice it more than others.

Certain diseases or drugs can cause presbyopia in people younger than age 40. When the symptoms of presbyopia occur earlier than usual, it is called premature presbyopia. If you notice the symptoms of presbyopia at an age earlier than the normal onset, it may be a warning of an underlying medical condition.

You are at a higher risk for premature presbyopia if you have:

• anemia (lack of enough or normal blood cells)
• cardiovascular disease
• diabetes (difficulties metabolizing blood sugar)
• hyperopia (farsightedness, or greater difficulty seeing near objects)
• multiple sclerosis (an autoimmune disease that affects the spine and brain)
• myasthenia gravis (a neuromuscular disorder that affects the nerves and muscles)
• eye trauma or disease
• vascular insufficiency (poor blood flow)

Some prescription and over-the-counter drugs can reduce your eye’s ability to focus on close images. Taking the following drugs can put you at a higher risk for presbyopia:

• alcohol
• antianxiety drugs
• antidepressants
• antihistamines
• antipsychotics
• antispasmodics
• diuretics

Other considerations that may put you at a higher risk for the earlier onset of presbyopia are:

• being female
• having had intraocular (eye) surgery
• eating an unhealthy diet
• having decompression sickness, also called “the bends,” which results from rapid decompression; it typically occurs in scuba divers that surface too quickly
• living closer to the equator (giving you more exposure to ultraviolet radiation and higher temperatures)

The most common symptoms of presbyopia occur at around age 40 for most people. Signs of presbyopia typically involve a gradual deterioration of your ability to read or do work up close.

Common symptoms related to presbyopia are:

• eyestrain or headaches after reading or doing close work
• difficulty reading small print
• fatigue from doing close work
• need for brighter lighting when reading or doing close work
• need to hold reading material at an arm’s distance to properly focus on it
• overall problems seeing and focusing on objects that are close to you
• squinting

Hyperopia is a condition that has symptoms similar to presbyopia. However, they are two different disorders. In hyperopia, as in presbyopia, distant objects are clear, but closer objects appear blurred.

Hyperopia occurs when the eye is shorter than normal or the cornea is too flat. With these malformations, the light rays focus behind the retina, as in presbyopia. However, hyperopia is a refractive error that is present at birth, while presbyopia occurs with age. It is possible to have hyperopia and then develop presbyopia.

If presbyopia is undiagnosed or uncorrected, your vision will likely deteriorate gradually and become increasingly intrusive to your lifestyle over time. If a correction is not made, you may experience a significant visual disability. You will develop problems maintaining your usual levels of activity and productivity at work and in everyday activities. When tasks such as reading small print become difficult and remain untreated, you are at risk for headaches and eyestrain.

Since everyone develops presbyopia as they age, it is possible to have presbyopia in addition to another type of refractive error. Presbyopia can combine with:

• astigmatism (an imperfection in the curvature of the cornea that causes blurred vision)
• hyperopia
• myopia (nearsightedness)

It also is possible to have a different type of refractive error in each eye.

Contact your physician or eye specialist if you have any of the symptoms associated with presbyopia. Even if you are not experiencing symptoms, you should have an eye examination by age 40.

According to the American Academy of Ophthalmology, adults who do not have any symptoms or risk factors associated with eye disease should have a baseline examination at age 40. An eye screening can identify early signs of disease and vision changes that can begin, sometimes without any symptoms, at this age. (FAAO, 2007)

Presbyopia can be diagnosed as part of a comprehensive eye examination. A typical exam will include tests to evaluate your eyes for the presence of diseases and vision disorders. It is likely that your pupils will be dilated with special eye drops to allow your physician to examine inside your eye.

No cure exists for presbyopia, but there are several alternatives available to correct your vision. Depending on your condition and lifestyle, you may be able to choose from corrective lenses, contact lenses, or surgery to correct your vision.

Non-prescription reading glasses may be sufficient if you did not need eyeglasses before the onset of presbyopia. These “readers” typically are available at retail stores such as drug stores. They typically work best when reserved for use during reading or close work.

When selecting a pair of over-the-counter reading glasses, try different degrees of magnification. Select the lowest magnification that allows you to read a newspaper comfortably.

You will need prescription lenses for presbyopia if you can’t find an appropriate magnification from the non-prescription offerings. You also will need a prescription if you already have lenses to correct another refractive error. There are several variations of prescription lenses, many of which are described below.

• Prescription reading glasses can be prescribed if you have no other problems other than presbyopia and prefer not to purchase your glasses off the shelf.
• Bifocals have two different types of focus with a noticeable line between them. The upper portion is set for distance while the lower portion is set for reading or close work.
• Progressive lenses are similar to bifocal lenses. However, they do not have a visible line. They offer a more gradual transition between the distant and close portions of the prescription.
• Trifocals have three different points of focus. The portions are set for close work, mid-range, and distance vision. They can be made with or without visible lines.
• Bifocal contact lenses provide the same option as bifocal glasses.
• Monovision contact lenses require that you wear a contact lens set for distance vision in one eye and a different contact lens set for close work in your other eye.
• Modified monovision contact lenses require that you wear a bifocal contact lens in one eye and a contact lens for distance in your other eye. Both eyes are used for distance. Only one eye is used for reading. Your brain adjusts to use the right lens for the distance of the image being processed.

Because your eyes will continue to gradually lose more of their ability to focus on close objects, your prescription will have to be reviewed and changed according to the advice of your eye specialist.

There are several surgical options to treat presbyopia, such as:

• Conductive keroplasty (CK) uses radiofrequency energy to change the curvature of the cornea. While effective, the correction may diminish over time for some people
• Laser-assisted in-situ keratomileusis (LASIK) can be used to create monovision. This adjustment corrects one eye for near vision and the other eye for distance.
• Refractive lens exchange involves the removal of your natural lens. It is replaced with a synthetic lens, called an intraocular lens implant, inside your eye.

In most cases, the vision you’ve lost to presbyopia can be corrected with eyeglasses, contact lenses, or surgery. The gradual decline of the elasticity required to focus your lens on near objects continues until about age 65, when most of the elasticity is gone. However, even at that point, correction to see close objects is possible.

There is no proven technique for the prevention of presbyopia. The gradual decline of the ability to focus on near objects affects everyone. However, you can help protect your vision with these precautions:

• Have regular eye examinations.
• Control chronic health conditions that could contribute toward vision loss, such as diabetes or high blood pressure.
• Wear sunglasses.
• Wear protective eyeglasses when participating in activities that could result in eye injury.
• Eat a healthy diet with foods containing antioxidants, vitamin A, and beta carotene.
• Make sure you are using the right strength of eyeglasses.
• Use good lighting when reading.

Consult with your physician or eye specialist regarding any changes in vision or eye health. Many eye diseases and conditions can benefit from early intervention and treatment.