Understanding cataracts and intraocular lenses.
Inside your eye, your natural lens functions like a camera lens, allowing you to focus on objects. “When your natural lens turns dense and cloudy with age, it becomes a cataract. It’s a normal part of life,” says Dr. Kendall Donaldson, a cataract surgeon at the Bascom Palmer Eye Institute, part of the University of Miami Health System.
The progression from clear lens to cataract is so gradual, we adapt by using stronger eyeglass prescriptions, increasing our light for daily activities, and slowly limiting our activities (such as night driving). “My patients tend to think every age-related vision issue is correctable with glasses, but cataracts eventually require surgery,” Dr. Donaldson says.
During cataract surgery, she breaks up the old, clouded lens using ultrasound or with a laser, then removes it with a tiny instrument. She replaces the old lens with a clear synthetic lens. “The new lens is so soft and flexible, it folds up like a burrito which can be injected through a special instrument. When placed in the eye, it opens and settles into place within a natural structure of the eye called the capsular bag.” Like a contact lens, the intraocular lens implant (IOL) contains a prescription customized to the patient’s visual needs.
Cataract surgery is an outpatient procedure performed under local anesthesia, allowing patients to return to their routine within days. With a high success rate and the promise of better vision, the decision to have surgery is not difficult. “Deciding when to have surgery and what type of lens implant best suits a patient’s needs can be a more difficult decision,” says Dr. Donaldson. For Cataract Awareness Month in June, she shares information on cataract surgery and lens implants.
Deciding on surgery
As cataracts progress, people make lifestyle adjustments like those mentioned earlier. “As an ophthalmologist, if I can’t get the patient to see 20/20, I’m looking for a reason why. I know the right questions to ask to see how cataracts affect the patient’s lifestyle.” Unlike some surgeries, Dr. Donaldson believes patients should view cataract surgery as a welcome opportunity to improve their vision and possibly free themselves from glasses or contact lenses.
Selecting a lens
“Patients have varying degrees of knowledge about intraocular lenses. Educating patients is key, because choosing the right lens is a lifelong investment. We ask about their lifestyle, profession, hobbies, and goals for surgery. We then evaluate those considerations, along with their visual needs.”
A comprehensive eye exam and precise, computer-generated measurements of each eye factor into the decision. “Cataract surgery is becoming more customized. We can correct astigmatism and presbyopia in some patients so that they don’t have to wear reading glasses.”
There are two main types of lenses with several subtypes of each:
Standard monofocal lenses have one prescription throughout the lens. These lenses allow you to see well at one distance (either distance or near, but not both). Most patients choose a distance monofocal lens and wear glasses for reading. This type of lens is covered by insurance.
These lenses do not correct astigmatism – any remaining astigmatism could cause blurriness at all distances if you’re not wearing glasses. Most patients have some degree of astigmatism; however, if the astigmatism component of their prescription is small, they can achieve excellent vision at distance and simply wear over-the-counter reading glasses.
Toric monofocal lenses are custom lenses that have either distance or near correction and are also customized with the patient’s astigmatism correction. For patients with astigmatism, this provides clearer vision without glasses for distance. They can then wear simple over-the-counter readers following surgery. In some patients, astigmatism is corrected with a laser enhancement surgery after the original cataract surgery.
Presbyopic lenses a more recent innovation, allow patients to focus both near and far while minimizing the need for glasses. These lenses are not covered by insurance. There are two types of presbyopia correcting lenses: accommodating lenses and multifocal lenses. These lenses come in toric varieties (for patients with astigmatism) and non-toric varieties for patients with spherical eyes (minimal astigmatism). The Crystalens, for example, is an accommodating lens that moves forward inside your eye to change focus from distance to near. It provides good distance vision and functional intermediate distance vision for a computer screen. Most people with this lens can read large type without glasses but may need readers for small print. After surgery, patients gradually adapt to a presbyopic lens by learning to hold items at a certain distance.
Multifocal lenses offer good near, far, and intermediate vision in each eye. Some patients, however, do experience a slight decrease in quality of distance and/or reading vision. They may also have reduced vision in dim light and may see halos around lights at nighttime. In patients that experience some of these potential side effects, the symptoms improve with time. Multifocal lenses are designed to reduce dependency on glasses. Most patients are extremely happy with multifocal lenses and experience a dramatic decrease in the use of glasses. There may be an adjustment period as they learn to use their new lenses.
It’s important to consider your expected outcome when contemplating cataract surgery. “No surgery makes us 20 years old again where we can focus at every point. Therefore, your expectations need to be reasonable and consistent with the technology of 2018,” Dr. Donaldson says.
Between the ages of 50 and 70, other visual changes may occur, from macular degeneration to glaucoma. “Routine eye exams play a vital role in catching age-related conditions early, when treatment is more effective. We’re lucky that technology is always evolving so that patients have many more options as they consider cataract surgery. Cataract surgery was once simply removal of the cloudy lens and replacement with thick glasses. In 2018, we are fortunate that it is also an opportunity to correct vision and reduce dependency on glasses.”
To schedule an eye exam at Bascom Palmer, call 305-243-2020 or click here.
Nancy Moreland is a contributing writer for the UMiami Health News Blog. She has written for several major health care systems and the Centers for Disease Control and Prevention. Her writing also appears in the Chicago Tribune.