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Extensive planning necessary for complex cataract surgery
A patient presented with a host of ocular issues that had the potential to affect the course and outcome of cataract surgery.
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As surgeons progress in their careers and perform thousands of cataract surgeries, there is a pleasure that comes with doing a routine cataract surgery. The ophthalmologist can work to elevate every stage of surgery in order to produce the safest, most predictable visual results while simplifying the steps into their most elegant and minimally invasive elements.
But quite often patients present to our clinics with multiple concurrent ocular issues that make the cataract surgery more complex. By performing a thorough preoperative exam and carefully planning the surgical procedure, we can solve these complex cases and provide a successful outcome for our patients.
Preoperative examination
In the case presented here, an 80-year-old woman notes poor vision in her right eye for about 1 year. She has a history of pseudoexfoliation glaucoma with a prior trabeculectomy performed in the right eye. Her vision is only hand motions in the right eye and 20/50 in the left eye. There is no afferent pupillary defect noted, although a right sensory exotropia is present. IOP is 12 mm Hg in the right eye and 13 mm Hg in the left eye.
Slit lamp examination shows a poor tear film, a dry ocular surface, blepharitis and corneal guttae. She had a prior superior trabeculectomy with a large iridotomy for control of her pseudoexfoliation glaucoma. Her posterior synechiae is limiting the pupillary dilation to 3 mm. The right cataract is dense, mature and white, and the anterior chamber is somewhat shallow at 2 mm, while the left eye has a 2+ nuclear cataract and a more normal 3 mm anterior chamber depth. There is no view of the posterior segment of the right eye, although B-scan ultrasound shows an attached retina. The left eye has a normal posterior segment other than a cup-to-disc ratio of 0.8 for the optic nerve, indicative of the glaucoma. The axial lengths, measured with A-scan ultrasound due to the density of the cataract, are about 24 mm in each eye with keratometry values in the 43 D to 44 D range with a mild degree of against-the-rule astigmatism.
Anticipated surgical challenges
The small pupil precludes adequate access to the cataract during surgery. Viscoelastic can be used to break the posterior synechiae and free the iris adhesions, although it may be wise to dye the anterior lens capsule with trypan blue before to ensure optimal staining. Iris hooks or retractors will likely prove beneficial in expanding the pupil and maintaining exposure during the case. Using the Oetting technique, the iris hooks can be placed in a diamond shape, with the lead hook under the main phaco incision.
The presence of a shallow anterior chamber means that we will need to be careful to work away from the corneal endothelium. The relatively weak corneal endothelium also has to be protected with a good dispersive viscoelastic, and it may need to be recoated during the procedure to ensure optimal protection. The patient has a normal axial length, so we would normally expect a deeper anterior chamber, more than the 2 mm noted. This shallow anterior chamber likely indicates that the entire lens-zonule-iris complex has shifted anteriorly. In fact, when the patient is reclined into the supine position, the anterior chamber is noted to deepen. This confirms the zonular laxity and the need for intraoperative capsular tension rings, segments or even suture fixation for the IOL.
The prior trabeculectomy surgery provides an extra outflow channel for the balanced salt solution during phaco, which can lead to fluidic instability and increase the risk of posterior capsule rupture and vitreous loss. This can be mitigated by injecting viscoelastic near the trabeculectomy site, but this must be removed at the end of the surgery to ensure continued functioning of the trabeculectomy to control glaucoma. Even then, the cataract surgery itself is a risk factor for future failure of the trabeculectomy to adequately control the patient’s IOP and glaucoma. A lower flow setting with an increased bottle height can help to rebalance the fluidics.
The patient presented with a host of ocular issues that can affect the course and outcome of cataract surgery. The pre-existing trabeculectomy will influence the fluidic balance during phacoemulsification, the pseudoexfoliation syndrome means that the zonular support can be lax, the posterior synechiae and small pupil may necessitate the use of iris hooks, the dense white cataract will require more ultrasonic energy to remove, and the corneal issues include a relatively low endothelial cell count and a compromised ocular surface. Finally, because this unilateral cataract has been present for about 1 year, the patient has developed a sensory exotropia that may cause postoperative diplopia.
Image: Devgan U
The dense white cataract will need to be mechanically disassembled within the capsular bag, likely with a chop technique. Phaco power modulations can help to limit the amount of ultrasound energy delivered into the eye. My choice for the IOL is a three-piece monofocal design because this design will be amenable to a variety of placement and fixation choices such as sulcus placed or sutured to the iris or sclera if need be. A postoperative refractive goal of slight myopia is recommended in case the patient experiences corneal failure and requires an endothelial transplant, which would result in a hyperopic shift. The mild amount of corneal astigmatism will be helped with our planned temporal phaco incision, but due to the complexity of her case, the refractive results are less important than the anatomic results of the cataract surgery.
The blepharitis and ocular surface disease need to be cleaned up prior to cataract surgery. This can be accomplished with lid hygiene, artificial tears and sometimes topical steroids. Because the tear film is the first refracting surface of the eye, optimizing it can improve the postoperative visual results for our patient.
The sensory exotropia indicates that the patient has had poor vision in this eye for at least a year, and it may indicate that the visual potential of the eye is limited. While we did not detect an afferent pupillary defect, this eye may have vision that is limited by the glaucomatous damage to the optic nerve, which cannot be visualized in this eye. If the patient recovers a reasonable central visual acuity in this eye after surgery, she may have intractable diplopia.
Finally, understanding that the patient will have additional challenges during surgery, we must plan for a longer procedure with more prolonged local anesthesia. The patient will also need more time for postop recovery and may not recover the full visual potential as compared with a patient with a more routine clinical situation. Due to the higher risks of surgery, the patient may need additional future procedures such as a corneal endothelial transplant, a vitrectomy, a repeat glaucoma surgery or even IOL suture fixation. But with the current profound visual impairment that the patient currently has, the potential benefits outweigh the risks, and performing this complex cataract surgery is a reasonable choice.
By carefully evaluating the patient and making a surgical plan, we can likely deliver better vision for the patient while enjoying the satisfaction of a challenging surgery.