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Degree of glaucoma damage may influence choice of IOL
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 Richard L. Lindstrom |
Glaucoma is a common comorbidity in the patient who presents for cataract surgery. If we include glaucoma suspects and those with ocular hypertension, more than 15% of patients carry both diagnoses, according to surveys of Medicare data. The only comorbidity more frequently encountered by the cataract surgeon is age-related macular degeneration.
In the cataract patient with associated glaucoma, there are several important decisions to be made. First, the surgeon needs to decide if glaucoma surgery is needed prior to or in combination with the cataract surgery. I remain impressed that for most patients with mild to moderate glaucoma, cataract surgery alone is preferred to a combined approach with trabeculectomy or tube shunt. It is common for patients to experience a significant reduction in IOP and medication burden with a much lower complication rate after cataract surgery alone.
In addition, clear corneal surgery leaves us with an eye that is a near-perfect starting point for any of the more invasive glaucoma surgical interventions that might be needed to control IOP if the cataract surgery and topical medications are not adequate. The increasing availability of minimally invasive glaucoma surgery approaches such as the Trabectome (NeoMedix), endocyclophotocoagulation and the hopefully soon to be approved Glaukos iStent will likely tip me over to doing more combined procedures in the near future, especially in the patient who has demonstrated poor compliance with topical medications or who desires for lifestyle or quality-of-life issues a reduced dependence on topical medication. But for now, cataract surgery alone in the glaucoma patient is my most commonly selected approach.
Another important consideration is the selection of an appropriate IOL. While the majority of surgeons and patients will opt for an aspheric monofocal IOL in the glaucoma patient, there remains the option of a toric, accommodating or multifocal IOL. As more patients become aware of these advanced-technology IOL options, ophthalmologists are forced to decide how they are going to counsel their individual patients. There are many opinions and little data to support our decisions in this regard. Nonetheless, we see these patients every day, and a patient-centered decision must be made.
We do have some optical science to help us, and it is on this basis that I make my recommendations. The key known fact is that glaucoma damage is associated with a measurable and meaningful reduction in contrast sensitivity, and this contrast sensitivity progresses as the glaucoma damage progresses. For this reason, I favor an aspheric single-focus optic in any patient who presents with measurable glaucoma damage or, in my opinion, is likely to develop such damage. This limits my patients to an aspheric monofocal, toric or accommodating IOL.
My indications for these IOLs are more or less the same for the glaucoma patient as they are for the patient with no glaucoma. In patients with significant glaucoma damage, the expected potential lifestyle-enhancing benefits of a toric or accommodating IOL require additional thought, but for me they are an option for the patient who is motivated to reduce dependence on glasses for lifestyle or quality-of-life reasons.
Three diopters of astigmatism is potentially as much a handicap to the glaucoma patient as to any other, and while data is scant, I continue to be impressed as a refractive corneal surgeon and refractive cataract surgeon that, in many patients, quality of vision, even as measured on a Snellen visual acuity chart, is often improved over what can be achieved with spectacles when significant astigmatism is corrected surgically. I also remain comfortable offering the glaucoma patient mild monovision, with a target in the near eye of no more than –1.5 D, and am impressed that clinically they do well. The availability of accommodating IOLs with aspheric optics makes me comfortable offering these as an option as well.
The controversy, of course, revolves around the use of a multifocal IOL in the patient with significant glaucoma. While aspheric optics have improved multifocal IOL performance, there remains a real reduction in contrast sensitivity that is associated with the implantation of any multifocal IOL. For me, this excludes them as an option in the glaucoma patient who has or is likely to develop significant glaucoma damage.
It is easy to determine which patients have significant glaucoma damage, but how does one know which patient is likely to develop damage with associated compromise of contrast sensitivity? The best guide for me is to evaluate the risk factors as delineated in the Ocular Hypertension Treatment Study. It is possible to calculate a percent probability that glaucoma damage will develop in a given patient with ocular hypertension, and this information can be evaluated by the surgeon and shared with the patient, allowing a more informed decision to be made. I find myself on the conservative side in this area and rarely recommend a multifocal IOL in the patient with more than a very mild elevated IOP and no other associated risk factors. I do not, however, quarrel with those who are comfortable and report good outcomes and high patient satisfaction with multifocal IOLs in the patient with ocular hypertension and very early glaucoma damage.
It will take decades of follow-up to be certain in which ocular hypertensive and glaucoma patients the benefits outweigh the risks, and I suspect by then we will have accommodating IOLs with larger accommodative amplitudes and customized aspheric optics that will make the debate no longer relevant. In addition, I suspect that in a decade we will also have minimally invasive glaucoma procedures and enhanced medical therapies that reduce the chance of glaucoma damage progressing after cataract surgery to near zero. Still, I find myself forced to make this decision frequently today, and for my high-risk ocular hypertensive and glaucoma patients, aspheric monofocal, toric and accommodating IOLs remain a strong preference.