When preparing to perform cataract surgery on patients with glaucoma, surgeons must consider how the operation may affect subsequent or prior trabeculectomies and other glaucoma procedures. On the positive side, optimal cataract surgery can improve a given patient's IOP control and the success of continuing medical therapy. Furthermore, cataract removal can enhance the patient's ability to perform visual field testing, as well as increase the accuracy of optic nerve and nerve fiber layer assessment.THE PROCEDURE OF CHOICE
A topical, clear corneal technique allows the ophthalmologist freedom in timing glaucoma procedures and may be used regardless of whether or not the patient has a pre-existing, filtering bleb (Figure 1). Topical anesthesia is safer for the patient and the glaucomatous eye, with a minimal risk of snuffing out a remaining central island of vision (a phenomenon of uncertain etiology that sometimes occurs after surgery in patients with advanced glaucoma). Most importantly, the temporal clear corneal technique does not cause conjunctival scarring, so cataract surgery may be performed before or after filtering surgery. Although my outcomes are best if I separate the cataract surgery from the filtering procedure, I use the same technique whether the procedures are combined or not.
I apply 2% lidocaine gel combined with 1% cyclopentolate, 2.5% phenylephrine, and Acular (Allergan, Inc., Irvine, CA) to the ocular surface one half-hour before the patient enters the OR. If the pupil requires stretching or synechiae need to be broken, I perform an intracameral injection of nonpreserved lidocaine 1%.
I create the paracentesis with a 1-mm diamond knife. If there is a pre-existing bleb or I plan to perform a combined case on a right eye, I make sure the incision is sufficiently anterior to the bleb. Fixating the eye with a cotton-tipped swab minimizes conjunctival trauma, which can adversely affect future glaucoma surgery or compromise an existing bleb.
After injecting a cohesive viscoelastic such as Co-Ease (Advanced Medical Optics, Inc., Santa Ana, CA) or Healon (Pfizer Inc., New York, NY) into the anterior chamber, I use a diamond keratome to create a 2.8-mm temporal clear corneal incision. I prefer to keep the incision size as small as possible so that the patient may perform digital massage, if necessary, as early as possible after the surgery. Massage can help push aqueous through the surgical sclerostomy to keep it open and to lower the IOP.
Generally, I believe it is best to perform the cataract and glaucoma procedures separately, if possible. Doing so helps to minimize inflammation and results in a less variable outcome in terms of postoperative refractive error, astigmatism, and IOP control. For eyes in which the cataract is worse than the glaucoma, I first perform the cataract surgery, which frequently reduces the patient's IOP and thereby allows some individuals to defer or avoid glaucoma surgery. The outcome of a trabeculectomy in those who still require the procedure is often improved by the reduction in medication use frequently made possible by cataract removal. Nevertheless, IOP may rise slightly after cataract surgery in the presence of a pre-existing bleb.
DEALING WITH SMALL PUPILS
To simplify the creation of the capsulorhexis and minimize the risk of complications, I typically stretch any pupil smaller than 4 to 5 mm. Injecting a dispersive viscoelastic such as Vitrax (Advanced Medical Optics, Inc.) or Viscoat (Alcon Laboratories, Inc., Fort Worth, TX) will enlarge pupils sized 5 to 7 mm, but the use of this sort of viscoelastic device increases the patient's risk of iris prolapse. For this reason, I attempt to place a shell of Co-Ease or Healon beneath the dispersive viscoelastic before creating the capsulorhexis. I am also careful to allow as much viscoelastic as possible to prolapse from the anterior chamber before and during hydrodissection.
I stretch a small pupil with two Kuglen hooks simultaneously, and, after reassessing the size of the pupil with the placement of viscoelastic, I repeat the stretching as necessary. I perform aggressive stretching, angle-to-angle, and avoid stretching the pupil toward the temporal incision, because this movement increases the likelihood of iris prolapse. If this complication does occur, then I decompress the anterior chamber and replace the iris with a cyclodialysis spatula or the end of the Co-Ease or Healon cannula. Before inserting the phaco tip into the patient's eye, I place a small amount of Co-Ease just inside the temporal incision in order to push the iris posteriorly. When iris prolapse has persisted, I have often found it helpful to inject Miochol-E (CIBA Vision, Duluth, GA) into the anterior chamber, immediately inside the temporal incision, at the end of the case as a means of repositioning the iris or keeping it in the eye.
I use the Sovereign System with WhiteStar Technology (Advanced Medical Optics, Inc.) and a 0º phaco tip. I find that the amount of energy needed to remove the nucleus is remarkably low with this equipment, and lesser ultrasonic energy is especially important in the eyes of patients with pseudoexfoliation or a narrow- or closed-angle component to their glaucoma. No matter the phaco technique used, the fluidics of the Sovereign make even these complicated glaucoma cases safe and fast.
I prefer to implant three-piece IOLs because they are easy to position and manipulate within the eye and they provide refractive stability. I personally favor the Clariflex lens (Advanced Medical Optics, Inc.). When teaching residents how to perform cataract surgery, I prefer to use IOLs that behave predictably during placement into the eye, and I have found that this lens enters the eye in an easy, quick, controlled fashion (Figure 2).
Another advantage of three-piece IOLs is that they give the surgeon some control if he encounters a problem with lens placement, the IOL itself, or excessive patient movement. In the case of ophthalmology residents, whose capsulorhexes may be bigger or less regularly shaped than expected, I do not worry that a three-piece IOL will not remain in position within the bag after the procedure. Lastly, in the setting of a combined cataract and glaucoma procedure, during which unexpected hypotony may occur, I find the Clariflex lens is stable and decreases the chance of iris capture compared with other IOLs.
Patients with glaucoma have decreased contrast sensitivity and tend to be more disabled by glare than patients not suffering from the disease.1 Glare is of particular concern to me because I practice in southern Arizona. I have found that my patients who receive a Clariflex lens with the OptiEdge design experience less glare and better vision than those who receive IOLs with both anterior and posterior squared edges, as well as greater visual ability in demanding settings. After cataract surgery and implantation of this IOL, their performance on visual field testing also improves.
Additionally, an IOL with a squared posterior edge helps minimize posterior capsular opacification. This preventive measure is particularly important in glaucoma patients, many of whom may take a prostaglandin analog to control their glaucoma. Prostaglandins have been associated with increased or prolonged inflammation in the surgical setting.2 By avoiding a YAG capsulotomy, the possibility of inflammation or trabeculitis is minimized.
Lens material is no longer as important a factor in the choice of an IOL now that we have third-generation silicone and second-generation hydrophobic acrylic lenses. In patients who will likely need a vitrectomy in the future, however, I tend to use an acrylic IOL (Sensar; Advanced Medical Optics, Inc.) in order to enhance the retinal surgeon's intraoperative visualization.
I favor the Unfolder Silver series (Advanced Medical Optics, Inc.) of injectors. My residents load IOLs themselves and learn to do so quickly with this delivery system, which also makes it easy to place the trailing haptic inside the eye without the use of an additional instrument.
Cataract surgery in patients with glaucoma can be more complicated than in routine cataract patients. It is important to recognize that patients' vision may already be compromised by their glaucoma and to take into account their particular needs when choosing the equipment and materials used in cataract surgery. Doing so optimizes surgical outcomes and improves their vision for the long term.
Robert J. Noecker, MD, is Associate Professor of Ophthalmology and Director of the Glaucoma Service, Residency Program, and Clinical Studies Program at the University of Arizona in Tucson. Dr. Noecker is a consultant for Allergan, Inc., and receives research funding from Allergan, Inc., Akorn, Inc., Pfizer Inc., Merck & Co., Inc., Genentech, Inc., and Lumenis Inc. Dr. Noecker is a speaker for Allergan, Inc., Alcon Laboratories, Inc., Lumenis Inc., Merck & Co., Inc., and Novartis Ophthalmics, Inc. He holds no financial interest in any products mentioned herein. Dr. Noecker may be reached at (520) 321-3677; firstname.lastname@example.org. Nelson P, Aspinall P, Papasouliotis O, et al. Quality of life in glaucoma and its relationship with visual function. J Glaucoma. 2003;12:139-150.
2. Yeh PC, Ramanathan S. Latanoprost and clinically significant cystoid macular edema after uneventful phacoemulsification with intraocular lens implantation. J Cataract Refract Surg. 2002;28:1814-1818.