The term “dysfunctional lens syndrome” can help physicians educate their patients about the best treatments for presbyopia, cataract, and related conditions, said Daniel S. Durrie, MD. Increasingly, more eye-care professionals are using the new term, he noted.
“This is a trend over the last five years, but it has intensified in the last two years,” said Dr. Durrie, Durrie Vision, Overland Park, KS, where, in his practice he does not use the terms “presbyopia” or “lack of accommodation.”
One reason for the terminology shift is the discovery that age-related stiffness, discoloration, and lens clouding is a result of increased disulphide bond formations between the crystalline proteins within lens fiber cells, he noted.
“People need to know it’s a natural process,” Dr. Durrie said. “It’s an aging change, but we don’t have to put up with it like our parents and grandparents did.”
In stage 1, the stiffening reduces the lens’ ability to focus, the condition commonly referred to as presbyopia. (The term is derived from the ancient Greek words presbus “old man” and ops “eye.”) In this stage, the lens remains clear and colorless, so patients are able to compensate with reading glasses, biofocals, or monovision. This occurs around 43 to 48 years of age.
In stage 2, which happens to people in their 50s and 60s, the continuing buildup of disulphide bonds scatters light. With their discolored lenses, people this age need more light to read and their night vision begins to deteriorate.
In stage 3, the disulphide bonds have accumulated to the point that significantly less light can pass through, the condition known as a cataract. (The term derives from the Latin cataracta “waterfall” or “portcullis,” and may originally have been used figuratively.) The average age for cataract surgery is 73 years, Dr. Durrie said.
A prodrug using lipoic acid to restore vision by breaking down the disulphide bonds (developed by Encore Vision) is now in clinical trials.
Perhaps a laser could be developed to do that job, Dr. Durrie said, but these treatments are “down the road.”
In the meantime, patients may choose to treat stage 1 dysfunctional lens syndrome with contact lenses, glasses, LASIK, PRK, corneal inlays, or IOLs. Though none of these approaches restores the eye’s ability to accommodate, they increase the patient’s depth-of-focus or create zones with different refractive powers.
Conventional LASIK and PRK require correcting one eye for distance and one eye for near vision, which can result in a lack of depth perception or imbalanced vision if the difference between corrections is too great.The sweet spot for most patients is a -1.25 D difference, he said. Multifocal LASIK creates different power zones for near and distant vision.