Almost everyone has to use optical aids like bifocals for reading by the age of 50. Presbyopia is the gradual loss of the eye's ability to adjust and focus when trying to read or see up close, according to the National Eye Institute. Luckily, there are alternatives to traditional bifocal eyeglasses.
Corneal Surgery
Laser-Assisted in Situ Keratomileusis, LASIK, Photorefractive Keratectomy,PRK, and Conductive Keratoplasty, CK, eye surgery offer options for bifocal patients. The U.S. Food and Drug Administration notes that PRK and LASIK use lasers to reshape the front of the cornea, while CK uses radio frequency. Both kinds of surgery are done while a person is awake and only take a few moments.
The most common treatment with this type of surgery is called monovision and involves reshaping or altering the cornea of one eye to achieve enhanced vision up close. This is usually done on the non-dominant eye. Ocular dominance is the preference of visual input of one eye over the other. The dominant eye is not surgically corrected unless there is a need to fix distance vision.
Eye doctors often recommend using a temporary contact lens to test monovision before having the surgery to ensure a patient is comfortable with this type of vision correction, according to a 2006 article in "Transactions of the American Ophthalmological Society."
Reading Glasses
Reading glasses are used as an alternative to bifocals. The lenses of some reading glasses, called "half eyes" are smaller and are worn lower on the bridge of the nose, allowing a person to look over the top of the frames if they need to see in the distance.
A reading prescription can also be put into a larger frame. The whole lens of the eyeglass contains the correction for reading. This provides good vision for close objects but makes distant objects look blurred. Full lens reading glasses have to be taken off to see in the distance. The Department of Ophthalmology and Vision Services at the University of Illinois notes that these lenses are best for people who do not mind switching between distance and reading glasses or who wear contact lenses for seeing in the distance.
Reading glasses work well for people who have trouble adjusting to regular bifocals or who require a large viewing area for detail work.
Contact Lenses
Contacts as an alternative to bifocals are available in several styles. Lenses come in soft and rigid, or gas-permeable, material and have a bifocal lens, similar to glasses. Contact lenses are also prescribed as monovision, with one lens used for distance vision and the other for near vision.
Bifocal contacts are also available as extended-wear lenses, contacts that can be worn overnight.
Artificial Intraocular Lens
Cataract surgery is done to remove a cloudy or discolored crystalline lens, the part of the eye that flexes and changes shape to help with focus. After cataract surgery, an artificial intraocular lens, or IOL, is an option for implantation to replace the eye's natural lens. IOLs can be made as bifocal IOLs and function much like a person's normal lens for seeing up close and far away. Bifocal IOLs are more expensive than regular, single-vision IOLs.
Progressive Bifocals
Progressive lenses are bifocals that are not visible in the lens. This type of bifocal is also commonly referred to as a no-line or invisible bifocal. The top of the lens is used to see in the distance and the middle and lower portion of the lens gets gradually stronger, progressing the strength of the reading portion near the bottom of the lens.
Progressive bifocals are a popular choice for bifocals because they are cosmetically attractive. According to the All About Vision website, progressive lenses also provide natural and comfortable vision as opposed to traditional lined bifocals, which have an image jump as a person looks through the line.
References
- National Eye Institute: Presbyopia
- National Library of Medicine: LASIK Eye Surgery
- All About Vision: Progressive Lenses
- University of Illinois at Chicago: Presbyopia
- National Center for Biotechnology Information: The Effect of Different Contact Lens Powers on the Visual Function of Presbyopic Emmetropic Patient
