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Meet, exceed patient expectations with proper IOL selection

Those with glaucoma who seek vision correction with cataract surgery require special considerations.

by Richard B. Mangan, OD, FAAO

This course is jointly sponsored by PCON, The State University of New York State College of Optometry and Vindico Medical Education. It is COPE-approved for 2 continuing education credits.

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Recent decades have seen a rapid evolution of designs, materials and implantation techniques for IOLs, making them a safe and practical way to improve, if not restore, visual functioning through surgery. With this ever-increasing menu of lens options comes a greater responsibility to discern which lens design and material is best suited for a particular patient. The “one-size-fits-all” approach to IOL selection for cataract surgery will soon become a practice of the past.

As our general population continues to age, more and more patients with disposable income will be looking to enhance their visual functionality and overall quality of life through premium lens technology. This is evident based on a survey conducted by the International Society of Refractive Surgeons/American Academy of Ophthalmology, which approximated a 10% increase in refractive lens exchanges performed in 2007 (U.S. Trends in Refractive Surgery)

Proper IOL selection is only part of the battle in meeting or exceeding patient expectations. As the average age of our patient population continues to rise, so does systemic and ocular comorbidity. Friedman and colleagues (The Eye Diseases Prevalence Research Group) estimate that 20.5 million Americans currently have cataracts. Most will have their cataracts surgically addressed in their early to mid 70s.

The research group also estimates that 1 out of every 10 patients undergoing cataract surgery has been previously diagnosed with glaucoma. Additionally, according to the largest prevalence study conducted to date on ocular surface disease, approximately 1 in 10 women in their mid 70s suffers from chronic dry eye (Schaumberg and colleagues).

More and more patients with glaucoma, diabetes and ocular surface disease will be anticipating an improved quality of life through premium lens technology when their cataracts become clinically significant. I will review pearls and pitfalls in managing the visual expectations of the glaucoma patient who is considering cataract surgery or a refractive lens exchange.

Treat the ocular surface preoperatively

A healthy ocular surface is critical when trying to meet a patient’s visual expectations after cataract surgery or refractive lens exchange. Too often, this component of visual functioning is either overlooked preoperatively or simply taken for granted.

Managing clinically significant dry eye disease can often be challenging. However, in the glaucoma patient, this can be especially difficult.

Noecker reports that benzalkonium chloride (BAK) is the most commonly used ophthalmic preservative. While BAK is an effective preservative and may play a complementary role by enhancing drug penetration for topical agents, chronic use may exacerbate ocular surface disease. A number of studies have shown that the chronic use of eye drops preserved with BAK can weaken cellular junctions, decrease goblet cell density and increase inflammatory mediators on the ocular surface, all of which contribute to symptomatic dry eye disease, according to Noecker.

Coincidentally, one study by Broadway in 1996 showed a significant decrease in fibroblasts and inflammatory cells in the conjunctiva within 1 month after discontinuing BAK. Studies by Ichijima and colleagues indicate that concentrations of BAK as low as 0.005% can induce pathological changes in living corneal tissue.

It is important to emphasize that the effects of BAK are not only dose dependent, but cumulative, according to Cha and colleagues. Most importantly, Broadway and colleagues reported in 1994 that continued exposure to BAK over time increases the risk of poor corneal and conjunctival wound healing. Therefore, it is important for today’s clinician to be aware of the effects of BAK on the ocular surface and use strategies to limit this exposure.

Manage preexisting lid disease

When confronted with a glaucoma patient, it is easy to blame a poor ocular surface entirely on age-related aqueous deficiency or toxicity related to the glaucoma drops (BAK, pH or the active ingredient). It is, therefore, easy to overlook posterior blepharitis or mixed inflammatory lid disease as a contributing factor. The clinician that recognizes this condition early will greatly enhance the chances of a good refractive outcome by appropriately treating the lid disease preoperatively.

Warm compresses, the treatment of choice for inspissated meibomian glands (meibomianitis), 2 to 4 weeks prior to surgery can be helpful in improving tear quality in these patients. Warm compresses induce the “melting” of the gland secretions, which relieves the blockage of the glands.

For patients with significant inflammatory lid disease, low-dose doxycycline and oral omega-3 fatty acids can also be effective. Unfortunately, it takes time to see results with these treatments, and proper adherence is usually poor, especially in the asymptomatic patient seeking refractive lens exchange.

Azasite (azithromycin, Inspire) used with lid massage therapy is a good option for resolving meibomian gland disease in this patient population. Azasite, a mixture of azithromycin (a macrolide antibiotic with anti-inflammatory properties and a high affinity for ocular tissue) and DuraSite, a matrix forming polycarbophil vehicle (InSite Vision, Alameda, Calif.), offers significant tissue penetration resulting in an impressive therapeutic index as an anti-infective and anti-inflammatory agent. It is this staying power that allows for its more convenient once daily dosing schedule, which makes patient compliance around ocular surgery promising.

Restasis effective perioperatively

It has been well documented that Restasis (0.05% cyclosporine A, Allergan) can decrease symptoms and improve the quality of vision in dry eye patients. Studies by Roberts and Elie also suggest that the perioperative use of cyclosporine emulsion 0.05% can decrease dry eye symptoms and improve visual recovery after laser vision correction as well as cataract surgery. For the patient diagnosed with glaucoma who is considering lenticular surgery, the use of Restasis may be a valuable adjunctive therapy.

Strategies to limit BAK exposure

Lotemax (loteprednol etabonate 0.5%, Bausch & Lomb), a site-specific “soft” topical ester-steroid, is an excellent drug for the short-term or intermittent management of inflammatory dry eye in the glaucoma patient. However, as most forms of glaucoma and ocular surface disease are chronic in nature, Restasis should be the drug of choice for managing recalcitrant ocular surface disease. Restasis has a superb safety profile, including no deleterious effect on IOP.

Factors to consider in IOL selection

Your recommendation on IOL design for the glaucoma patient will largely depend on four factors:

For the 65-year-old or older patient with minimal nerve damage, well controlled IOPs and strong motivation for spectacle independence, a multifocal IOL, such as ReZoom (Abbott Medical Optics, Santa Ana, Calif.), AcrySof ReStor (Alcon, Fort Worth, Texas) or Tecnis (AMO), may be an acceptable option. However, for younger glaucoma suspects or patients with glaucomatous nerve damage and corresponding reductions in central threshold contrast sensitivity, multifocal IOLs may not be the best choice. While there has been little research to date on multifocal IOLs and the glaucoma patient, it is fairly well established that these lenses reduce contrast sensitivity to some degree when compared to monofocal IOLs, according to Kowamorita and Uozato.

Additional concern with multifocal implants revolves around our limited understanding of the effect these lenses have on diagnostic testing, including – but not limited to – automated perimetry and nerve fiber layer analysis.

One lens option to consider that addresses these concerns and yet provides some degree of presbyopia correction for the highly motivated patient is the Crystalens HD (Bausch & Lomb, Aliso Viejo, Calif.). The Crystalens, an accommodating IOL with a 5-mm enhanced monofocal optic, offers some degree of pseudoaccommodation and improved depth of focus, allowing 80% of subjects in the U.S. Food and Drug Administration trials to become J2 or better at 4 months. The HD lens provides this improved near vision without increasing undesirable dysphotopsia or night vision symptoms.

Considering an aspheric design

For moderate to severe glaucoma patients with measurable threshold sensitivity loss, an aspheric design should be considered.

Three aspheric lens designs have “new technology” (NTIOL) status and are currently available in the United States:

The Centers for Medicare and Medicaid Services (CMS) define an NTIOL as: “An IOL that CMS determines has been approved by the FDA for use in labeling and advertising the IOL’s claims of specific clinical advantages and superiority over existing IOLs with regard to reduced risk of intraoperative or postoperative

complications or trauma, accelerated postoperative recovery, reduced induced astigmatism, improved postoperative visual acuity, more stable postoperative vision or other comparable clinical advantages.”

The NTIOL designation allows for additional reimbursement for these lenses implanted in an ambulatory surgery center.

In patients where there is no concern over lens decentration (i.e., history of trauma, pseudoexfoliation, etc.), the Tecnis is an excellent choice. Of the three lens options, the Tecnis, which is a three-piece, foldable lens available in either acrylic or silicone, is the only aspheric IOL developed based on wavefront-aberration analysis of human corneas, according to Wang and colleagues. By matching the positive asphericity of the cornea (+0.27 microns) with the negatively aspheric Tecnis CL (-0.27 microns), we would expect to see an improvement in functional vision under mesopic and photopic conditions, according to Mester and colleagues and Bellucci and colleagues.

It should be pointed out, however, that negatively aspheric IOLs such as the Tecnis CL should be used with caution in patients with negative corneal asphericity, estimated by Holladay and colleagues to approximate 10% of the general population. Such patients with highly prolate corneas, including those who have undergone hyperopic laser refractive surgery, would be at risk for increased negative spherical aberration if paired with the Tecnis or the AcrySof IQ.

While the AcrySof IQ, a single-piece hydrophobic acrylic lens, also adds significant negative spherical aberration to the eye, Werner has documented concern regarding the decrease in visible light entering the eye due to its blue wavelength blocking material. In an eye with preexisting nerve damage, this may be a concern.

For patients with small pupils or where zonular compromise is expected, two precautions should be considered. For those surgeons accustomed to working with Malyugin and capsular tension rings, moving forward with the Tecnis aspheric may still be acceptable. If not, or when significant zonular compromise is suspected, a neutral aspheric design, such as the Sofport AO, is more forgiving when lens decentration or tilt does occur, Hayashi reported. The decentration of an IOL with negative or positive spherical aberration may induce defocus, astigmatism and coma, which would degrade the optical transfer function and, hence, image quality, according to Altmann and colleagues.

Each of the aspheric lenses offer advanced edge designs that decrease capsular opacification postoperatively. The sloping OptiEdge design by AMO has also been proven to significantly reduce internal reflection, thereby reducing glare. Therefore, aspherically designed monofocal IOLs should be strongly considered in patients with contrast sensitivity deficits related to glaucomatous nerve damage. Monovision is still an acceptable option in this subset of patients seeking less dependency on eye wear for near or intermediate tasks.

Reducing astigmatism

Hoffer estimated that between 15% and 20% of cataract patients have more than 1.5 D of corneal or refractive astigmatism. For patients desiring reduced dependency on glasses following surgery, the goal should be to reduce the amount of astigmatism to 0.50 D or less while maintaining the preexisting axis. There are a number of ways to accomplish this goal:

While all of the above techniques are routinely used to treat astigmatism in routine cataract surgery, not all are ideal when dealing with glaucomatous nerve damage. Subjecting the optic nerve to pressures in excess of 60 mm Hg, albeit for a short period of time as when creating the corneal flap with mechanical microkeratomes, may not be a good idea for patients with preexisting disease, according to Cameron and colleagues. Bushley and colleagues have suggested that acute spikes in IOP associated with microkeratome technology can, in fact, create or worsen visual field loss.

The use of femtosecond technology in “all-laser” or “bladeless” LASIK may prove to be an acceptable option considering that the rise in IOP imposed during flap development is approximately half that of mechanical microkeratomes. The Intralase FS, AMO’s fourth-generation femtosecond laser, now comes with a 60-kHz engine, allowing flaps to be created in a more timely fashion (about 20 seconds) as compared to the earlier models. Further study in this area is certainly warranted.

A conservative approach would be a standard or wavefront-guided excimer laser surface ablation. In fact, in the presence of ocular surface disease, a surface ablation is preferred, as goblet cell loss is minimal in comparison.

While a non-wavefront-guided surface ablation should be considered a sufficient option for residual astigmatism after implant surgery, Knorz has anecdotally reported successful wavefront or customized enhancements in the pseudophakic patient. When dealing with higher-order aberrations such as coma, the ability to perform reliable customized enhancements would be welcome.

Toric IOLs, in most cases, offer the advantage of correcting astigmatism without concomitant or subsequent corneal surgery. While there still may be some debate over the blue wavelength-blocking effects associated with Alcon’s AcrySof Toric IOL, the benefits, in my opinion, outweigh this concern. The AcrySof Toric has proven to be a predictable and precise implant with minimal lens rotation.

Alcon’s recently approved aspheric toric design (SN6ATT) offers negative asphericity equal to that of the aspheric IQ lens (SN60AT), yielding an improved modulation transfer function and hence improved image quality. When you consider the effect multiple surgeries can have on the eye with respect to inflammatory and neurogenic side effects, exacerbated by postoperative drops containing preservatives, the impact of a reliable toric lens cannot be overstated.

Establish realistic expectations

Without question, the most important aspect of the preoperative consultation in the glaucoma patient seeking a refractive lens exchange is establishing realistic expectations. Premium IOL technology comes with a premium price tag and often premium expectations. It is important for this subset of patients to understand that some or most of their vision loss may not be related to their cataract, but rather to nerve damage from their glaucoma. In essence: “Under promise and over deliver.”

For patients with adequate nerve function contemplating a multifocal or accommodating IOL, consider trial framing their distance refractive error followed by near vision assessment with a pre-printed near vision acuity chart. Monocularly, have him or her initial and date the smallest font paragraph they can read. Despite your best efforts at educating patients preoperatively about the delayed “wow” factor associated with the multifocal IOLs (the 3 to 6 months it takes for cortical adaptation to occur), even the most motivated of patients may get discouraged early on into the postoperative period.

By showing the patients the near vision chart again postoperatively, they will recognize that they are already reading significantly better when compared to the smallest paragraph they could read before surgery. This will ease their concerns and allow for greater patience as you both wait for adaptation to occur.

CME precautions postoperatively

Glaucoma patients are generally at no greater risk for developing postoperative cystoid macular edema (CME) in uneventful cataract surgery as compared to nonglaucomatous cataract patients. However, there has been some concern regarding multiple case reports noting postsurgical CME in patients who were concomitantly being treated with prostaglandin analogs for glaucoma.

To date, little evidence has been offered in the literature for a cause-and-effect relationship between the two, according to Arcieri. While CME can be especially bothersome to a patient who has received a multifocal IOL, every precaution should be exercised when managing IOP in a patient with pre-existing glaucomatous nerve damage. Therefore, the clinician must weigh the potential risks and benefits from temporarily stopping prostaglandin analogs in the glaucoma patient who has had cataract surgery or a refractive lens exchange.

Additional protection against CME is generally offered in the form of a topical nonsteroidal anti-inflammatory drug (NSAID). Each of the FDA-approved topical NSAIDs have shown effectiveness in preventing and reducing angiographic CME after surgery. However, if a patient has a history of poor drop compliance, especially with the mid-day application, Xibrom (bromfenac ophthalmic solution 0.09%, Ista) is often recommended due to its convenient FDA-approved twice-daily dosing schedule.

Managing IOP spikes

Postoperative pressure spikes are certainly more of a concern in the glaucoma patient, especially in the presence of moderate to advanced cupping. Thankfully, with clear-cornea cataract surgery, acute pressure spikes are, in most cases, easily managed. A paracentesis, at a previously established corneal side-port incision, will release fluid (most likely a combination of aqueous and viscoelastic) from the anterior chamber and pressure should normalize quickly. However, IOPs can still rebound to higher-than-expected levels in a short period of time for varying reasons. Therefore, it is important to monitor these patients more closely, especially in the presence of advanced cupping.

Comanagement tips

The resumption of glaucoma medications postoperatively will largely depend on the level of nerve damage. For ocular hypertension patients, you may not feel compelled to resume any medications until they are further out postoperatively. Baseline pressures can then be re-established at 4 to 6 weeks postoperatively.

For more advanced cases, adding drops back on day 1 is certainly understandable. However, as mentioned earlier, in those patients at greater risk of developing CME (i.e., diabetes, broken capsule, etc.) we carefully weigh the advantages and disadvantages of resuming the use of the prostaglandin analog, as Avakian and colleagues have suggested this class of drug can worsen macular edema.

Postoperative laser procedures

While the latest IOL edge designs are greatly reducing the development of posterior capsular opacification (PCO), you will see it. Should you see PCO within the first 6 months after surgery, you will need to be aware of a few points. Once a capsule has been opened with the YAG laser, it is much more difficult to perform a lens exchange. Therefore, if the patient’s refraction is not on target postoperatively, and a lens exchange is the preferred answer to correct the visual problem, this should be addressed first. However, if the residual refractive error would be better managed with a surface ablation (i.e., residual astigmatism), the YAG capsulotomy should be done first. This will allow you to get a more accurate refraction and a better result.

For the glaucoma patient who elected to have a multifocal IOL, proper lens centration is critical. Should you discover that a slight decentration has occurred, this can sometimes be overcome by an argon laser iridoplasty. When the rings of a multifocal are not properly aligned with the patient’s pupil, the refractive or diffractive pattern becomes asymmetrical and may reduce quality of vision, according to Donnenfeld.

Microsurgical Technology
For those surgeons accustomed to working with a Malyugin Ring (Microsurgical Technology) and capsular tension rings, moving forward with the Tecnis aspheric may be acceptable.
Image: Scripture K

With argon iridoplasty, the surgeon places the 500 micron spots in the midperipheral iris, in the quadrant the IOL has decentered toward. According to one study presented by Eric Donnenfeld, MD, at the 2007 AAO Annual Meeting in New Orleans, digital photography showed a mean pupillary shift of 0.55 mm, and both uncorrected and best corrected visual acuity improved by one line. This one line of visual acuity improvement can sometimes mean the difference between a satisfied and unsatisfied patient.

Glaucoma patients desiring an improved quality of life via cataract or refractive lens exchange surgery may still be eligible for presbyopia-correcting IOL designs. However, for those patients with moderate nerve damage from this often chronic disease, an aspheric lens may preserve or even improve contrast sensitivity and overall visual functioning in both normal and dim illumination. With careful preoperative planning and counseling, these patients can achieve excellent outcomes and you will continue to be successful.

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