29 Premium Intraocular Lenses in Minimally Invasive Glaucoma Surgery Subspecialty ophthalmologists share a common focus on a small organ, but their goals of patient management can vary. For example, if a glaucoma specialist and a cataract refractive specialist are caring for the same patient, one might be aiming for an extra point of intraocular pressure (IOP) reduction while the other may favor an extra quarter diopter of cylinder reduction. Although it is natural for physicians to give greater emphasis to factors they encounter on a daily basis, it is becoming increasingly important to broaden the subspecialist’s scope of concern. As the population ages, so does its collective desire for improved outcomes. The physician has to adapt to meet these growing patient needs. Today’s ophthalmologist must incorporate a wider view of patients’ concerns and identify patients’ goals to confirm their alignment with the goals of the referring physician. Historically, glaucoma surgery has been highly invasive and frequently associated with postoperative complications.1 The notion of making a complex situation worse by introducing refractive goals was a step too far. Fortunately, the introduction of minimally invasive glaucoma surgery (MIGS) has allowed us to align pressure goals and physician expectations with the desired refractive goals of the patient. Minimally invasive glaucoma surgery, a term coined by Iqbal “Ike” Ahmed, is defined by the following principle features: ab interno procedure, biocompatibility with minimal disruption of normal anatomy/physiology, high safety profile, efficacy of IOP lowering, and quick recovery time. The iStent (Glaukos Corp., Laguna Hills, CA) is currently the only approved MIGS device for use in the United States, and it has a high safety profile when combined with cataract surgery.2 The iStent is refractively neutral and enables us to make a pressure intervention without introducing additional optical aberrations. This chapter illustrates our approach to patients undergoing phaco-MIGS. We shall discuss issues regarding ocular surface disease, excimer support, IOP spikes, and the monocular patient. The chapter ends with a patient case to illustrate some of these concepts. Paramount to establishing a surgical plan combining MIGS and refractive cataract surgery is determining the patient’s objectives. When identifying a patient with glaucoma and cataracts in need of surgical intervention, the next step is to determine if the patient wants to be less dependent on spectacles. Many patients state that they do not mind wearing glasses, whereas others have a strong desire to be more glasses independent. Patients having phaco-MIGS have three refractive options: remain in spectacles postoperatively, opt for distance spectacle independence, or aim for spectacle independence/reduction at distance and near. For patients who do not mind wearing glasses after surgery, the surgeon can offer a standard monofocal lens with a refractive error goal matching the patient’s desires. Typically the refractive error goal is a spherical equivalent of plano, but on occasion patients desire reading myopia; the choice is theirs, but the patient should be counseled to expect spectacle usage for most, if not all, tasks. The surgeon can allow any residual spherical or cylindrical error of their prescription to be addressed in the final spectacles. These patients will need biometry to help assess the needed intraocular lens (IOL) power to best meet their goals. Table 29.1 illustrates the supporting testing needed when addressing the cylinder at the time of surgery versus use of spectacles to correct any remaining postoperative astigmatism. For patients who desire greater independence from glasses, there are two options: glasses independence at distance or glasses independence at distance and near. Carefully addressing astigmatism can help these patients achieve their goals. Some patients do not mind wearing reading glasses or computer glasses and thus choose the option that is most likely to get them independent from glasses at distance. Other patients wish to be as independent as possible from glasses for both distance and near. For this latter group of patients, the surgeon can discuss their preference for monovision versus presbyopia-correcting IOLs including multifocal and accommodating lenses. The patient’s anatomy, physiology and particularly visual field findings can be used to guide options given to patients wishing presbyopia-correcting IOLs. The options for glasses independence at distance are no different for the glaucoma patient than they are for patients without glaucoma. When a patient desires glasses independence for distance vision, they can be offered a combination of tests to help them achieve their goals. Achieving emmetropia for spectacle free-distance vision requires accurate targeting of both spherical and cylindrical components of the refractive error. The ideal preoperative evaluation includes assessing the patient’s keratometry, topography, refraction, and biometry. These tests help to closely predict the postoperative residual cylinder. To better target the postoperative refractive error, intraoperative wavefront aberrometry can be used at the time of surgery for confirmation of IOL calculations and residual astigmatism. The ocular response analyzer (ORA) can be valuable when targeting the cylinder and can guide tools like on-axis surgery, astigmatic keratotomy (AK) with the femtosecond laser or manual AK, toric IOLs, or a combination of these depending on the amount of preoperative astigmatism (Table 29.1). In glaucoma patients, options for spectacle independence at both distance and near include multifocal IOLs, monovision, and accommodating IOLs. The patients’ visual field evaluation helps guide them in their choices. A visual field free from defects is needed prior to offering multifocal IOLs to glaucoma patients. Contrast sensitivity is reduced in both glaucoma and in multifocal IOLs,3,4 and the benefit of spectacle independence is unlikely to outweigh the reduced image quality seen when placing a multifocal IOL in a patient with glaucoma and visual field changes, especially considering that glaucoma can progress. For the group of patients exhibiting visual field defects, the physician can consider monovision and accommodating IOLs for improved spectacle independence. Monovision in glaucoma is similar to monovision in the unaffected population. Ideal monovision patients are those who have tried the method through contact lenses or happen to have natural monovision and enjoy the vision they experience. For patients who have not experienced monovision, but are interested in its possibility, the clinician should require a contact lens trial; however, this can be challenging in an older population and will not be perfect if there is a visually significant cataract. Typically the dominant eye is reserved for distance correction, and the nondominant eye for near. A thorough discussion with the patient regarding the risks of disease progression and subsequent difficulty with monovision is essential. With monovision it is important to understand the visual fields and ensure that defects are mild and not interfering with tracking. Alternatively, an accommodating IOL could be considered in glaucoma patients with visual field defects. The Crystalens accommodating IOL does not have the multifocality that causes a reduction in contrast sensitivity seen with multifocals. Thus, the Crystalens is a reasonable option for patients with glaucoma wishing to have some near vision with their distance correcting IOL. When considering a Crystalens, a thorough preoperative exam is important. Avoid using the Crystalens in patients with pseudoexfoliation due to the risk of an unstable zonulebag complex and to the risk of capsular contraction leading to a Z-syndrome. Finally, have a frank discussion with patients suffering from moderate to severe glaucoma who wish to use the Crystalens. When presented with all options, including each option’s limitations, it is not infrequent to hear a patient wanting anything that will give them some visual advantage over the standard monofocal lens. Therefore, great importance should be placed on presenting patients with all of their options while respecting their purchasing value. The decision ultimately belongs to the patient, not the doctor. Patients who are receiving treatment for glaucoma suffer from the same surface diseases that impede ideal visual outcomes in a refractive clinic. In fact, many of the IOP-lowering medication regimens can further worsen surface disease, making spectacle independence challenging. Glaucoma and cataract surgeons alike must do a thorough examination and treat the ocular surface to ensure the best refractive outcomes. A healthy surface is critical to realizing any potential gains that the surgeon has primed for reaching emmetropia. Specifically the surgeon should focus on dryness, meibomian gland dysfunction (MGD), and anterior basement membrane dystrophy (ABMD). Dryness and MGD should be treated preoperatively and the same holds true for ABMD when the surface is irregular and causing difficulty with biometry measurements. On occasion subtle ABMD is not treated preoperatively and may need to be addressed in the symptomatic postoperative refractive IOL patient with phototherapeutic keratectomy (PTK). Glaucoma specialists often do not have an excimer at their disposal, which makes offering options for spectacle independence difficult but not impossible. Just like a comprehensive ophthalmologist who offers premium IOL services might have a local refractive surgeon to team with, a glaucoma specialist should form a similar relationship. The cost of fully committing to performing refractive cataract surgery is significant, but for the financially restricted physician, the cost can be as minimal as acquiring a method of measuring keratometry and a marking pen for axis alignment. Premium lenses can be offered without excimer support, but many patients would benefit from an enhancement to enjoy their full visual potential. One such technology that currently exists in United States Food and Drug Administration (FDA) trials is the light-adjustable IOL,5 which enables post–phaco-IOL patients to have their postoperative refractive error adjusted in the immediate period following surgery. It is worth giving thought to the maximal rise in IOP that can be experienced with various surgical interventions (Table 29.2). With phacoemulsification alone, pressures of 60 mm Hg can be experienced during sculpting and irrigation/aspiration. The rise in pressures observed with femtosecond surgery depend on the type, due to differences in retention pressure from suction. With femtosecond cataract surgery, the IOP rise is lower than with femtosecond laser-assisted in-situ keratomileusis (LASIK) at 14 mm Hg and 130 mm Hg, respectively. To avoid the IOP rise to levels over 100 mm Hg observed with femtosecond LASIK, patients can be offered photorefractive keratectomy (PRK) as an alternative. In either case the surgeon should be mindful when thinning the cornea due to subsequent artificial effects on the measured IOP. Patients should be instructed on the relation between thin corneas and IOP so that they can inform their future eye care providers, and pressures can be appropriately adjusted. The monocular patient requires special consideration, and it is recommended that they wear a safety lens after cataract surgery. Options for spectacle independence should still be considered. Monocular patients who are a good steward of their health and who will wear the safety lens can be offered premium lenses. There are low-risk situations when these patients would benefit from having the best possible vision. One might argue that by targeting good uncorrected vision, surgeons are giving these patients a means of going without their safety lens. Nonetheless, aiming for the optimal visual potential remains in the patient’s best interest. A 59-year-old woman presents with complaints of difficulty with night driving because of glare. She had undergone myopic LASIK surgery 10 years ago. Her family history was significant for glaucoma, and she was using latanoprost nightly to both eyes. Table 29.2 Intraocular Pressure (IOP) Rise for Given Surgical Technique
Phaco-MIGS: Determining Expectations and Goals
Remain in Spectacles Postoperatively
Spectacle Independence
Distance Spectacle Independence
Spectacle Independence at Distance and Near
Special Considerations
Surface Disease
Excimer Support
Surgical Intraocular Pressure Spikes in the Glaucoma Patient
The Monocular Patient
Case Presentation
Surgical Technique | IOP Rise | Duration of IOP Rise |
Phacoemulsification | > 60 mm Hg | 5 to 30 minutes |
Femtosecond cataract | 14 mm Hg | 30 to 120 seconds |
Femtosecond LASIK | 130 mm Hg | 30 to 90 seconds |
Her best corrected visual acuities were 20/40 OU, but with brightness acuity testing dropped to 20/150 OD and 20/200 OS. Her IOP was 15 OU, with a previously established goal of upper teens OU (a goal established after LASIK surgery).
Pertinent exam findings included open angles with trace pigmentation OU, 1+ nuclear cataracts with 2+ posterior subcapsular cataracts on axis OU, and cup-to-disk ratios of 0.9 OU. Visual fields and topography are shown in Fig. 29.1 and Fig. 29.2. Optical coherence tomography (OCT) of the nerves and maculas was normal OU.
With her history of LASIK surgery, it was important to carefully review her visual objectives. Her hobbies included playing tennis and computer games. She reported enjoying books but did not describe herself as an avid reader. She reported that she highly desired to be less dependent on spectacles and wished to review options for spectacle independence.
Given this background we discussed the Crystalens. Although multifocal IOLs could be considered, there was concern about reducing her contrast sensitivity. Further, the Crystalens comes in a toric lens, which would allow treatment of her corneal cylinder at the time of her cataract and iStent surgery.
The ocular response analyzer was used intraoperatively to confirm and guide the choice of toric Crystalens and to direct the placement of its axis. Plano was targeted for her dominant right eye and –0.5D spherical power was targeted for her nondominant eye.
One month postoperatively, her visual acuity was 20/25 J5 OD and 20/60 J3 OS. Her refraction was plano –0.50 × 160 OD and –0.75 sphere OS. Her pressures were 16 OU despite self-discontinuation of latanoprost therapy. It was recommended that she remain off latanoprost given that she was at her predetermined IOP goal.
Three months postoperatively, the patient reported that her distance vision was not optimal. The right eye measured 20/30 but refracted to 20/20 with –0.25 –0.50 × 175.
Photorefractive keratectomy (PRK) to her right eye was discussed, and she elected to proceed with the treatment. Post-PRK she was 20/20 in the right eye uncorrected and quite happy with her vision.
Pressures have been at her IOP goal and she continues to be followed for her glaucoma. Her visual fields remain stable, and she is pleased with her vision.
