Careful patient selection and education is always important when deciding to implant a premium intraocular lens (IOL) after cataract removal, but there may be additional structural and functional considerations for patients with comorbid glaucoma.
Speaking at the 23rd Annual Glaucoma 360 Symposium, held during the 2019 Glaucoma 360 meeting, Shan C. Lin, MD, outlined issues he considers when patients with glaucoma are interested in reducing spectacle dependence after cataract surgery.
“Patients getting a premium IOL are paying out of pocket and have high expectations for their outcomes,” said Dr. Lin, Glaucoma Center of San Francisco. “It is important to carefully assess if their glaucoma or any other ocular comorbidity that could affect the quantity and quality of their vision.”
Dr. Lin suggested that toric IOLs and multifocal IOLs can be an option for patients with glaucoma who do not have visual field loss, assuming the absence of other ocular conditions that would exclude them as candidates for those lenses.
For patients with peripheral visual field loss whose glaucoma is stable, a toric IOL may be appropriate, but he would tend towards not implanting a multifocal IOL in that situation.
Dr. Lin said pseudoexfoliation and traumatic glaucoma are not absolute contraindications for using premium IOLs, but he would consider the decision carefully before proceeding. He was firm in his recommendation against implanting a premium IOL in patients with central visual field loss.
Rationale for recommendations
The severity of glaucoma is an important issue in deciding on the use of premium IOLs, Dr. Lin said.
“Foveal sensitivity is a critical issue for determining whether a patient will experience benefit from a premium IOL,” Dr. Lin explained. “If central acuity is affected or at significant risk for being impacted in the near future, these lenses should be avoided.”
In addition, contrast sensitivity is reduced in eyes with glaucoma and are further reduced by multifocal IOLs.
“The extended depth of focus IOL (TECNIS Symfony, Johnson & Johnson Vision) does not reduce contrast sensitivity compared with a monofocal IOL,” Dr. Lin said. “Therefore, it is a potential consideration for glaucoma patients interested in a presbyopia-correcting lens.”
Positional stability of the IOL is a concern in patients who have pseudoexfoliation or who have a history of ocular trauma because they may have existing or future zonular instability.
“Patient education and expectations are crucial as with any of our patients,” Dr. Lin said. “But in these situations patients should be apprised that they may be taking a chance with a toric or multifocal IOL due to possible shift or dislocation.”
He noted that zonular laxity can often be detected prior to surgery with some simple maneuvers.
“To observe for obvious laxity, I will jostle the slit lamp table and tell patients to look in one direction, and then the opposite direction, to see if there is lens movement.” Dr. Lin said. “Surgeons may also consider putting in a capsular tension ring to maintain IOL stability in these patients.”
If the decision is made to proceed with implantation of a premium IOL in patients with pseudoexfoliation, Dr. Lin suggested making a generous capsulorhexis, about 5.5 mm in diameter, and even creating some radial incisions in the anterior capsule using an Nd:YAG laser in the postoperative period to account for potential capsular phimosis.
General considerations Dr. Lin said it is important in all patients to consider glaucoma stability.
“The best candidates for a premium IOL have controlled intraocular pressure without evidence of disease progression for at least six months,” he added.
Ocular comorbidities that limit visual potential, including age-related macular degeneration or an epiretinal membrane, can exclude any patient from implantation of a multifocal IOL.
“Macular optical coherence tomography may be helpful in terms of determining whether or not to put in the premium IOL,” Dr Lin said.
Ocular surface regularity is also an issue and may be a particular concern in glaucoma patients who may have dry eye disease secondary to use of ocular hypotensive medications.
For patients who are possible candidates for a toric IOL, surgeons should also take into consideration the possible effect of glaucoma surgery on astigmatism. Currently available minimally invasive glaucoma surgical procedures have minimal effect on refraction, but both trabeculectomy and tube implant surgery can induce astigmatism in an unpredictable manner.
Dr. Lin said that ideally, patients will have undergone glaucoma surgery at least six months prior to cataract surgery and exhibit stability of astigmatism. In cases of combined surgery, however, he said he almost never will implant a toric IOL. In toric IOL implantation cases, surgeons can check the power and alignment through intraoperative aberrometry because there is evidence that its use can improve the re-fractive outcome.
“I have found intraoperative aberrometry helpful with toric IOL implantation,” Dr. Lin said. “It may improve the refractive predictability in eyes with a history of corneal refractive surgery. However, it is inconclusive if it is better than preoperative measures in routine cataract surgery.”