Cataract Symptoms & Types
A cataract is a clouding or opacification of the crystalline lens inside the eye. As the opacification progresses, light rays cannot properly pass through the cloudy lens to the retina and the vision becomes progressively blurred.
The clouding of the lens can occur at different locations within the lens. Cataracts are named according to the location of the opacification and there are many types. To name a few – a nuclear sclerotic cataract (the most common type and the type associated with normal aging) is a yellowing in the center of the lens and most commonly causes loss of low light distance vision, i.e., difficulty driving at dusk or night. A cortical cataract sometimes associated with UV light exposure is located in the outer layer of the lens and causes increased glare (at night and in bright sunlight) as it progresses.
Diabetes or steroid use increases the risk of formation of a posterior subcapsular cataract (located at the very back of the lens, just in front of the capsule that holds the lens). A posterior subcapsular cataract that progresses will cause nighttime glare and, eventually, a decrease in reading vision. In many cases, the first sign of a cataract for individuals over 30 is a significant change in the glasses prescription.
New eyeglasses, better lighting, or anti-glare sunglasses may improve the symptoms of early cataracts, but if these measures do not help, the only effective treatment is surgery. Cataract surgery involves the removal of the cloudy lens and replacement of the natural lens with an artificial lens that is called an intraocular lens (IOL).
Cataract surgery is performed as an outpatient procedure under local anesthesia. After the administration of eyedrops to dilate the pupil, you will be given a sedative to help you relax during the surgery and anesthetics to numb the eye. Typically, you are awake, but in the twilight zone, during the surgery.
A small incision is made in the numb cornea (the front part of your eye) and a tiny instrument using high-frequency ultrasound (phacoemulsification)is used to break up the center of the cloudy lens and carefully suction it out. The very back of the natural lens called the capsular bag is left in place to serve as a place for the artificial lens or IOL to rest.
The IOL is placed in the capsular bag using an injector delivery system, thus allowing a very small corneal incision– about 2 mm. Typically, when Dr. Parker performs cataract surgery, there is no need for sutures, because the incision is so small and self-sealing. Cataract surgery complication rates in this country are typically cited as 2-3% nationally, but Dr. Parker’s complication rate is less than 1%.
After your cataract surgery, expect your vision to improve within a few days. It is normal to feel itching and very mild discomfort and you will be using eyedrops to prevent infection and reduce inflammation. As your eye heals, you will enjoy improved clarity and color.
Cataract Surgery Implants & Intraocular Lenses
An intraocular lens (IOL) is placed in the eye at the time of cataract surgery after the cloudy cataractous lens is removed. The IOL allows light passing through it to be focused on the retina similar to the way the natural lens performed this function prior to becoming a cataract. Most IOL’s are acrylic and consist of a central optic (the focusing part of the IOL) with side struts called haptics that allow the IOL to be placed within the capsular bag that originally held the natural lens. Measurement of the corneal curvature and length of the eye taken prior to surgery are used to determine the specific power of the optic necessary for each individual. Typically, prior to placement within the eye, the IOL is folded or rolled up in an injector. Use of the injector allows easy placement of the IOL within the capsular bag through a very small corneal incision.
There are two basic IOL designs: monofocal or presbyopia correcting.
“Mono” means “one”, and this IOL design has one focus. Monofocal IOLs placed during cataract surgery have been used routinely since the 1970’s and the power is usually selected to provide best corrected vision at distance with the use of reading glasses for near activities. On the other hand, a person whose IOLs were set to correct near vision would need glasses to see distant objects more clearly.
Some patients who have worn monovision contact lens prescriptions prior to cataract surgery wish to have this situation after their cataract surgery. In this case, one eye’s IOL power is chosen for distance and the other for near. This reduces the need for reading glasses, but when the focus is widely separated for a full monovision correction depth perception is compromised.
Presbyopia Correcting IOL
Presbyopia refers to the loss of near vision that occurs with age and is a result of loss of flexibility in the natural lens. Patients who receive a monofocal IOL at the time of cataract surgery and have good uncorrected distance vision in that eye will have the near vision of a 65-year-old individual with that same uncorrected distance vision. They will need reading glasses or bifocals for near activities.
Thus, individuals who do not wish to wear any glasses after cataract surgery can choose a presbyopia correcting IOL. There are currently four IOL designs available for this purpose – Crystalens, ReZoom, ReSTOR, and Tecnis Multifocal. The Tecnis Multifocal is the latest addition to this group with FDA approval obtained in 2009 and is Dr. Parker’s first choice for cataract surgery patients who do not want to wear glasses after surgery. The Tecnis Multifocal IOL has an aspheric full diffractive optic (a series of rings on the back surface of the IOL) that allows high quality near and distance vision in low light conditions.
Visit www.tecnismultifocal.com for more information.
In the FDA approval for the IOL, 94% of patients receiving the Tecnis Multifocal would choose this IOL again. For more in depth information about your cataracts, make an appointment for a comprehensive examination of your visual system. Dr. Parker will thoroughly examine your visual system and quantitate the degree of cataract as well as define any other contributing factors affecting your vision.