Replacement of dysfunctional lens may pose multiple benefits

Take-home

Dysfunctional lens replacement may be a better option in certain cases for patients with dysfunctional lens syndrome who initially seek LASIK correction. With the availability of advanced diagnostic equipment, surgeons can now identify candidates and recommend this solution.

By George O. Waring IV, MD, FACS, Special to Ophthalmology Times

Charleston, SC-With the increasing baby-boomer population and greater awareness of surgical options for the treatment of presbyopia, more patients in their mid-50s to mid-60s are requesting LASIK to reduce their dependence on reading glasses and bifocals.

Advances in diagnostic technologies have given clinicians the objective ability to evaluate metrics-such as light scatter, lens density, tear film quality over time, and depth-of-focus.

Recently, the term dysfunctional lens syndrome (DLS) has been proposed to describe the aspects of the senile crystalline lens, including lens opacities, loss of accommodation, and increase of higher-order aberrations (HOAs). Clinicians educate patients on the natural history of DLS, available treatment options, and associated risks and benefits.

Although these patients are seeking LASIK, the recommended procedure of choice is often replacement of their dysfunctional lens. It is discussed with patients how a laser lens procedure-instead of a laser corneal procedure-may spare them multiple surgeries (LASIK now, and lens surgery in the forthcoming years) and how it may be the most appropriate surgical solution to optimize quality of vision.

Surgical option with multiple benefits

Dysfunctional lens replacement (DLR) can be considered an “all-in-one” surgical option with multiple benefits. First, it addresses the source of the problem-the senile crystalline lens and resultant dysfunctionalities. As a result, it optimizes visual quality by improving forward light scatter and HOAs.

Second, it can be a definitive surgical correction for the loss of accommodation that is often bringing the patients to the practice in the first place with advanced technology multifocal diffractive IOLs.

Lastly, DLR is a permanent solution that prevents cataract formation (Stage III dysfunctional lens). This all-in-one procedure addresses congenital and age-related ametropia, as well as age-related opacities. With diagnostic and surgical equipment technology available today-such as femtosecond lasers for lens surgery-LASIK-like outcomes can be delivered with quick visual recovery.

Who can benefit from DLR?

Ideal candidates for DLR are patients in their mid-50s to 60s who present for surgical options to reduce dependence on glasses or contact lenses and who have dysfunctional lens diagnoses. Often, these patients had corneal refractive surgery many years prior and present with the complaint that their LASIK has “worn off” and they are seeking an enhancement. DLR may be cases the most appropriate enhancement procedure for these individuals.

DLR has become my procedure of choice in patients with hyperopia with narrow angle, and ocular hypertension, even if they have had peripheral iridotomy in the past. In select cases, the procedure can significantly reduce IOP and may eliminate patients’ use of IOP-lowering eye medications. Due to lens softening with light and significant or total reduction of ultrasound use, the procedure can be highly effective for patients with Fuchs’ dystrophy as well, often sparing the need for a combined endothelial keratoplasty.

Diagnosing the syndrome

A diagnosis of DLS begins with a comprehensive ophthalmic examination and advanced digital ocular analysis. A careful slit lamp examination is conducted to determine if lens opacities exist, and if so, to what degree. An advanced eye analysis includes use of advanced diagnostics for objective lens density and light scatter evaluation. These findings are quantitatively correlated with the densitometer on the Scheimpflug camera.

A double-pass wavefront diagnostic device (AcuTarget HD, Visiometrics/AcuFocus) is used to measure light scatter; the device generates an ocular scatter index (OSI) score. Generally, an OSI score of greater than 2 and a densitometry reading of greater than 20 generally correlates with clinically relevant light scatter, where DLR may be indicated.

The device generates a point spread function (PSF), and this can be evaluated in three dimensions, which is an actual display of the pattern of light scatter falling on the patient’s retina. This measurement and display gives important qualitative information, and PSF pattern recognition is useful much like topography evaluation. The result of this advanced digital eye examination is a much more meaningful analysis than Snellen acuity, a metric described close to 150 years ago.

Based on the patients’ optical profile-including topographic, tomographic, wavefront analysis, light scatter, ocular health (including the ocular surface and macular health), and prior surgical status-clinicians can make a determination and recommendation to patients. Since most patients have come to the practice to receive LASIK, they are often surprised to hear that they have DLS-particularly because it is a little-known syndrome. Patient education is then required.

Educating patients

Patient education-which begins the moment patients step through the practice door-builds their confidence and empowers them in the decision-making process. Throughout the examination, technicians explain the goal of each diagnostic device. While patients wait during dilation, they view an informative video about femtosecond laser and IOL technologies on a tablet device.

During the examination patients are given a digital tour of their eyes, where they are shown their dysfunctional lens and the resultant light scatter, including both their densitometry scores, OSI and PSF. The analogy of two dirty windshields is used to illustrate how each laser option will affect their vision. It is explained how the secondary lens will continue to age, causing further decline in vision quality despite LASIK correction or enhancement.

The relative risks and benefits for both surgical and non-surgical options are thoroughly discussed. Finally, patients proceed to the counselor.

How the technique is done

Once a patient has made a decision to pursue DLR, the optical profile is matched to the best IOL to suit his or her needs (this includes HOA profiles). Typically, I implant a multifocal lens (Tecnis, Abbott Medical Optics) in patients who are candidates for this technology. I have found the full diffractive optics, large central optic, and spherical and chromatic aberration profiles of this lens to lead to the most consistent results.

The multifocal patient must have a perfectly healthy eye and less than 1.5 D of preoperative relatively regular astigmatism that I feel comfortable correcting with femtosecond-assisted LRI. Patients with more than 1.5 D of astigmatism are offered other strategies, such as toric IOLs and possible use of blended vision or bioptics. In selected cases with ocular pathology, such as epiretinal membranes or significant irregular astigmatism, use of accommodative IOLs is considered.

The surgery is performed by making limbal-relaxing incisions (LRIs) with a femtosecond laser (Catalys, Abbott Medical Optics), which we have found to be accurate and reproducible. We use intraoperative aberrometry, which is of particular benefit for post-refractive cases.

For patients aged 50 years and younger, we routinely do laser vision correction on the cornea. Patients aged 60 or more years typically receive laser correction on the lens. For patients aged 50 to 60 years, the determination is based on the optics and their individual needs.

I am proposing that DLR, by definition, requires use of a femtosecond laser, much like Daniel Durrie, MD, and Steven Slade, MD, proposed with sub-Bowman’s keratomileusis to differentiate femtosecond-assisted LASIK from mechanical keratomes.

Summation

DLR is often a better option for many patients with DLS who initially seek LASIK correction. With the availability of advanced diagnostic equipment, surgeons can now identify candidates and recommend this permanent solution, thus avoiding a continued decline in vision quality or a return trip for cataract removal and lens replacement. Patients can expect excellent outcomes and long-term satisfaction.

George O. Waring IV, MD, FACS, is director of refractive surgery and assistant professor of ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston. He is also medical director of the Magill Vision Center, Mount Pleasant, SC. Dr. Waring may be reached at waringg@musc.edu.