October 2016

 

CATARACT

 

YES Connect
Considerations for cataract surgery in short eyes


by Liz Hillman EyeWorld Staff Writer

 
 

Bryan Lee, MD
S
hort eyes present multiple challenges for the cataract surgeon. There is less working space, potentially resulting in more endothelial damage, and the iris is more prone to prolapse. These eyes often have synechiae as well as convex anterior capsules that may make the capsulorhexis run out. When the axial length is very short, there is also greater concern for posterior pressure and suprachoroidal hemorrhage.

Even if the surgery goes perfectly, IOL selection formulas are less accurate, so patients should be counseled appropriately. One tip I learned from David Chang, MD, is to note the anterior chamber depth when I examine patients at the slit lamp. I have found that to be a useful observation to utilize as a fudge factor with third generation IOL formulas. This month, two experts, Leela Raju, MD, and Zachary Zavodni, MD, share valuable tips to tackle these difficult cases. Their pearls include preoperative considerations, counseling, patient positioning, and operative planning. Drs. Raju and Zavodni do a fantastic job walking us through the entire pre-, peri-, and intraoperative process.

One final note: Doing a dry vitreous tap can be very helpful for achieving a deeper anterior chamber if viscoelastics are unable to create sufficient working space. However, a small amount of vitreous removal is often plenty. In very short eyes, the pars plana may not be where you expect, so you do not want to do a tap in that situation.

Bryan Lee, MD, YES Connect co-editor

 
Cataract surgery

Preventing iris prolapse, increasing chamber depth, IOL calculations, and more

When faced with cataract surgery in a short eye, one interesting piece of advice doesn’t depend on surgical technique or skill: Just speak with your patient, recommended Leela Raju, MD, associate professor, Department of Ophthalmology, NYU Langone Medical Center, New York.

“Reassuring patients throughout the procedure, or ‘vocal local,’ can help keep patients from holding their breath due to anxiety that could also increase posterior pressure,” she said.

Of course, there are many clinical and surgical things you can do to help manage these cases and achieve safe and targeted outcomes.

Preoperative preparation

During the preop examination, Dr. Raju tells patients there may be a need for additional medications in the surgery as well as the possibility for more intraoperative procedures to make sure everything goes smoothly. “Prior discussion of possibilities can always help the patient feel more informed and comfortable. But we have to assure them we have a plan in place in case the surgery varies a little from the standard operation,” Dr. Raju said. Zachary Zavodni, MD, The Eye Institute, Salt Lake City, said that patients with extremely short axial lengths (less than 20 mm) and small white-to-white measurements (less than 11 mm) may be at higher risk for suprachoroidal hemorrhage, which should be discussed. In addition, even a maximum power IOL (i.e., 40 D) might not fully correct the refractive error. In these cases, Dr. Zavodni said he tells patients they may still need to wear glasses or perhaps consider a piggyback IOL in the future. During the exam, Dr. Zavodni said he looks closely at the extent of anterior segment crowding. “Short, hyperopic eyes tend to have narrow angles, which can be exacerbated by phacomorphic narrowing in eyes with more advanced cataracts,” he said. “In eyes with notably narrow angles, I will perform gonioscopy prior to dilation to assess if the angle is occludable. I look closely for both anterior and posterior synechiae, as these are more common in hyperopic eyes with previous angle closure episodes and they are more likely to result in poor intraoperative dilation.”

Intraoperative situations

Intraoperatively, there are many considerations for cataract surgery in short eyes. First, Dr. Raju said she makes sure that the speculum is not placed too wide as it could contribute to posterior pressure. Perhaps the most immediate consideration in these cases is the prevention of iris prolapse. “I try to make my incision longer than average in these cases,” Dr. Zavodni said. “I also have a very low threshold to place a Malyugin ring, as placement often helps to minimize iris prolapse. The rhexis can be more difficult to control because of ergonomic adjustments necessary to accommodate the crowded anterior chamber and because these lenses often have increased anterior capsule convexity, which will steer a rhexis tear peripherally.” To prevent iris prolapse, Dr. Raju said she might create a scleral tunnel versus a clear corneal incision. She also said she’d consider using iris hooks if the anterior chamber is shallow, although she noted that just because an eye is short does not mean it has a shallow chamber. She also uses a dispersive viscoelastic to maintain the space, refilling with it often, especially when she removes instruments from the anterior chamber. For the very crowded chamber, digital massage or a vitreous tap might be in order. To start though, Dr. Raju said she gives intravenous acetazolamide or mannitol in an eye with an axial length of less than 21 mm. She would avoid retrobulbar anesthesia in favor of peribulbar or topical anesthesia, both of which she said could avoid surgeon-created posterior pressure. “If I still have shallowing after the viscoelastic is placed, I will consider a vitreous tap or dry vitrectomy,” she said. Dr. Zavodni said a “soft shell” technique with a cohesive OVD injected within a shell of dispersive OVD could increase chamber depth, but he cautioned against overinflating, which could cause iris prolapse. Dr. Zavodni said he might also use preoperative IV mannitol to soften the globe and allow the anterior chamber to deepen. A pars plana vitreous tap is an option for extreme cases as well. “In performing a pars plana tap, I make my sclerotomy 3 mm posterior to the limbus and aim posteriorly to the optic nerve to avoid hitting the lens. I prefer the use of a vitrectomy cutter over a needle with syringe because, in my hands, direct visualization and control are better,” he said. He added that when performing a tap, it is “essential to immediately, if not simultaneously, inject an OVD through the paracentesis to deepen the anterior chamber and to lessen the potential for a suprachoroidal hemorrhage.” However, Dr. Raju said that if the need for a vitrectomy occurs in some of the earlier cases for young eye surgeons and they do not feel comfortable with this procedure, they should contact a glaucoma specialist or another senior colleague familiar with vitrectomy to step in. Dr. Zavodni said in eyes with cataract and narrow angles, he would go straight to cataract surgery, rather than a laser peripheral iridotomy, unless the patient was describing relative block symptoms and couldn’t have cataract surgery in the near future, or if he didn’t think they were safe to dilate for cataract surgery. In those cases, he would perform laser peripheral iridotomy first. This procedure is still his first choice for patients with narrow angles who do not have a cataract yet.

IOL calculations

IOL calculations in short eyes can be a challenge. Even a small error in predicted effective lens position could result in a large relative refractive error, Dr. Zavodni said, noting that he prefers to use the Holladay 2 and Barrett Universal 2 formulas in these cases. Dr. Raju also uses the Holladay 2 formula as well as the Hoffer Q. “I have also found intraoperative aberrometry helpful in confirming lens selection,” she said.

Additional advice

Dr. Raju said patients with short eyes should be positioned in a way that will not add to positive pressure. That might mean the head being a little higher, with the eye above the level of the chest. To avoid suprachoroidal hemorrhage, Dr. Zavodni cautioned surgeons to avoid large pressure fluctuation during surgery. If such a situation is suspected, the surgeon should stop the procedure, suture the incision, and assess the choroid using an intraoperative ophthalmoscope.

Editors’ note: Drs. Raju and Zavodni have no financial interests related to their comments.

Contact information

Raju
: rajulv25@gmail.com
Zavodni: zacharyzavodni@gmail.com

Cataract surgery in short eyes Cataract surgery in short eyes
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