Presbyopia

Presbyopia (prez-bee-OH-pee-ah) refers to an eye condition that makes it difficult to see close objects. The word presbyopia comes from Greek words meaning "to see like an old person." It is a progressive condition that usually begins to become noticeable between the ages of forty and fifty. The condition is normal, common, and unpreventable.

Presbyopia results from age-related changes to the lens of the eye that make it difficult for the eye to focus on objects that are held close; people with this condition often hold books at arm’s length to read them and find it challenging to read fine print or in dim lighting. Glasses, contacts, and surgery can compensate for and correct presbyopia, but there is no known way to avoid it.

Description

Vision results from light rays entering the eye through the clear outer layer called the cornea. Light rays travel into the pupil, or the black area at the center of the eye, and through the lens behind it. The lens changes shape to help bend or refract light rays so they can be focused on the retina, which contains light-sensing nerve cells that transform light rays into electrical impulses that the brain interprets as images.

As part of the normal aging process, the lens hardens and becomes less flexible. Muscles that control the eye become less effective at focusing the light rays as they travel through the lens. As a result, the lens focuses the rays behind the retina instead of on it, and the image is not clear and easy to see.

The changes that cause presbyopia develop gradually over time. People as young as thirty-five may find it harder to read fine print on labels or a menu in a darkened restaurant, but it is more commonly noticed in the mid-forties. Because the condition is so common and unpreventable, it is not considered a disease.

Symptoms and Risk Factors

In addition to the challenges of reading small print and reading in dim light, people with presbyopia sometimes experience eyestrain and headaches. Normal-sized print may appear blurry. These problems can worsen when the person is tired or has been drinking alcohol.

The most common risk factor for presbyopia is age; nearly everyone over the age of forty will develop the condition on some level. Some diseases can increase the risk of developing presbyopia before the age of forty—known as premature presbyopia—including diabetes, cardiovascular disease, and multiple sclerosis. Drugs such as antihistamines, diuretics, and antidepressants also can cause premature presbyopia.

Diagnosis

Presbyopia is normal and does not require treatment. However, people generally seek help when vision impairment affects their ability to work or enjoy everyday activities. An eye doctor will diagnose the condition during a regular eye exam. During the exam, the physician will determine whether the symptoms are caused by presbyopia or another refractive eye condition such as hyperopia, myopia, or astigmatism.

For example, hyperopia, the condition commonly referred to as farsightedness, affects the ability to see close objects but not objects that are far away. However, it is caused by a shorter eyeball or flattened cornea that affects the way the light rays focus on the retina. Unlike presbyopia, which develops with age, hyperopia can affect people of any age, including newborns. Myopia—nearsightedness—is another refractive error like hyperopia and presbyopia, but it affects the ability to see far. Astigmatism is a minor imperfection in how the eye focuses that causes objects to appear blurry. Presbyopia can happen in conjunction with any of these conditions.

Treatment

Many people who experience presbyopia correct it simply and easily with reading glasses. These "readers" help the eye to focus during close work such as reading or sewing. Readers are readily available at many retail stores in a variety of price ranges and strengths. When selecting readers, people should choose the weakest strength that allows them to read newspaper print without strain. Charts often are on display near readers to assist with this choice. Reading glasses also may be purchased from an eye doctor, who will ensure that they are the correct strength.

Whether purchased by prescription or over the counter, reading glasses may be worn over prescription contact lenses to correct presbyopia and any other refractive error. In addition, bifocal and trifocal glasses are available to correct two or more problems with one pair of glasses. These types of lenses have one part prepared to permit distance vision and another part to correct close vision.

Contact lenses also can be prepared to allow multifocal vision. These lenses are weighted so that they rest on the eye in such a way that the prescription for distance viewing is in place when gazing out and the prescription for close vision is in place when the person looks down.

Another option for contact lens wearers is to wear one contact with a prescription that corrects for distance vision while the other corrects for close work. In time, the brain adapts to choose the correct eye for the task at hand. This correction technique is known as monovision. Regardless of the method of correction chosen, corrective lenses need to be adjusted over time to compensate for additional changes to the eye from the aging process.

Presbyopia may be corrected by surgery as well. LASIK surgery—a laser cut to the eye surface—can be used to induce monovision, with one eye correcting for distance and the other correcting for close work. Future enhancements to the procedure may result in laser surgery that will create multifocal corrections, much like built-in bifocals. Conductive keratoplasty (CK) uses radio waves to adjust the curve of the cornea and can improve close vision, but its effects are temporary. It also is possible to surgically replace the natural lens with an artificial one that eliminates the focusing error caused by presbyopia. This is called refractive eye exchange.

Bibliography

Boyd, Kierstan. "What Is Presbyopia?" American Academy of Ophthalmology. American Academy of Ophthalmology, 1 Sep. 2013. Web. 26 Jan. 2016. http://www.aao.org/eye-health/tips-prevention/what-is-presbyopia

"Facts about Presbyopia." National Eye Institute. National Institutes of Health. Web. 26 Jan. 2016. https://nei.nih.gov/health/errors/presbyopia

"How Your Eyes Work." American Optometric Association. American Optometric Association. Web. 26 Jan. 2016. http://www.aoa.org/patients-and-public/resources-for-teachers/how-your-eyes-work?sso=y

Pepose, Jay S. "Presbyopia Therapy: Comparison of Corneal Versus Lens-Based Options." Ophthalmology Times—Europe. UBM Medica, LLC, 1 Dec. 2015. Web. 26 Jan. 2016. http://ophthalmologytimes.modernmedicine.com/ophthalmologytimes/news/presbyopia-therapy-comparison-corneal-versus-lens-based-options

"Presbyopia." American Optometric Association. American Optometric Association. Web. 26 Jan. 2016. http://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/presbyopia?sso=y

"Presbyopia." Mayo Clinic. Mayo Foundation for Medical Education and Research. Web. 26 Jan. 2016. http://www.mayoclinic.org/diseases-conditions/presbyopia/basics/definition/con-20032261