Clinicians coming to terms with dysfunctional lens syndrome

Reviewed by Daniel S. Durrie, MD

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.”

Various stages

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.

Corneal inlays

Two corneal inlays are currently available in the United States (Kamra, AcuFocus; Raindrop, ReVision Optics). The former is polyvinylidene fluoride ring placed intrasomally in the cornea of the nondominant eye, with its small aperture expanding depth of focus. In contrast to conventional LASIK and PRK, the inlay does not diminish distance vision, which remains binocular.

“The [inlay] has been very popular,” said Dr. Durrie, who was a clinical investigator for the device and has been implanting it for 10 years. “I select patients that have good distance vision, no astigmatism, and healthy eyes. It works very well.”

The other inlay, an hydrogel implant, provides multifocal refraction. The strongest curvature is in the central region, providing near vision. The curvature gradually decreases toward the periphery, creating regions that provide intermediate and distance vision.

More corneal inlays are under development, and “if they get approval, we will be able to pick different ones for different patients,” he said, adding that no head-to-head trials have yet compared these inlays or either one to any of those still in the pipeline.

“Over the next 5 years, we’ll find out which patients are best for which procedures,” he said.

The inlays offer one significant advantage over IOL implants: they can be removed, making the procedure reversible.

Patients who are more than 3 D hyperopic may benefit from lens replacement even if they are in stage 1, he said.

“That’s the best procedure for these patients because it stops progression to stage 2 and stage 3,” he said. “A lot of people are going for that option because they can.”

Lens replacement is also the best option for someone who has progressed to stage 2 or 3, Dr. Durrie said. To educate patients about these options, Dr. Durrie often uses material from companies that provide inlays and laser surgery.

“With this new way to talk to patients, the industry is now responding with brochures and videos for dysfunctional lens syndrome education,” he said.

New diagnostic equipment helps, he says, especially the HD analyzer.

“It measures ocular scatter so it shows that if there is loss of quality,” he said. “It’s very easy to do. We use it on every patient in every exam.”

Dr. Durrie uses the results to show patients how light is being scattered from their lenses. He also listed the Pentacam (Oculus), Galilei (Ziemer Ophthalmic Systems) and the iTrace (Tracey Technologies) as useful devices.

“We do photos of lens to help educate patients,” Dr. Durrie said. “Lots of doctors are modifying the way they do exams so they can better educate patients.”

Optometrists are also finding it helpful to talk about dysfunctional lens syndrome, he said.

“Optometric groups are very enthusiastic about this,” he added, “because they can do a better job educating their patients and making sure they understand why a new pair of glasses isn’t going to help.”

Daniel S. Durrie, MD

E: DDurrie@DurrieVision.com

This article was adapted from Dr. Durrie’s presentation at the 2016 meeting of the American Society of Cataract and Refractive Surgery. He did not indicate any proprietary interest in the subject matter.