EyeWorld Asia-Pacific December 2016 Issue

41 EWAP CATARACT/IOL December 2016 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. EWAP Editors’ note: Drs. Raju and Zavodni have no financial interests related to their comments. Contact information Raju : rajulv25@gmail.com Zavodni : zacharyzavodni@gmail.com Views from Asia-Pacific FAM Han Bor, MD Senior Consultant, NHG Eye Institute @ Tan Tock Seng Hospital 11 Jalan Tan Tock Seng, Singapore Tel. no. +65-6357-7726 Fax no. +65-6357-7735 han_bor_fam@ttsh.com.sg C ataract surgery in short eyes poses three major challenges: iris prolapse, lack of space from shallow anterior chamber, and IOL power calculation. Preoperatively, during clinical examination, I usually make a note if the anterior chamber is shallow. I will reaffirm this with biometry. For short eyes, I have three levels of alerts for the shallow anterior chamber depth (ACD). The first level of alert is when the anterior chamber depth is less than 2.5 mm. With anything less than 2.3 mm, I will emphasize the associated risks and delayed recovery to the patient. When the ACD is shallow, the cataract is usually thicker. The lack of space for buffering coupled with the thicker cataract that requires more ultrasonic energy; the cornea may be less clear the next day and hence the visual rehabilitation may be longer. When the ACD is 2.0 mm or less, I will make provision for initial vitreous tap to deepen the anterior chamber. Iris prolapse The narrow angle and the forward arching iris of the shallow ACD present a high risk of messy iris prolapse. I minimize this by preemptively making the incision slightly more anterior or the having incision tunnel longer such that the internal entry of the incision is further away from the iris root. This is best done temporally being further away from the central cornea. Care must be taken to avoid OVD from creeping underneath and thereby elevating the iris forward. Sometimes, these patients may have had acute angle closure glaucoma with poorly dilating and floppy iris. In such cases, I would use iris hooks to dilate the pupil. Shallow anterior chamber The lack of space is a challenging problem. The endothelial cells could easily be compromised and the soft tissue traumatized. Femtosecond laser-assisted cataract surgery is a less mechanical approach. I prefer to use femtosecond laser especially for those with less than 2.3 mm ACD. I use viscoadaptive OVD (Healon5) as it is an excellent space-maintainer and adapts to the need of the surgery. It is also a very effective viscodilator for the pupil, sometimes obviating the need for mechanical pupil dilator. IOL power calculation IOL power calculation is a challenge. Fortunately, there are some newer formulae that have proven to be good. I personally have good experience with Barrett’s and RBF. Both are quite comparable in outcomes. Haigis, especially when triple optimized, is also a good and convenient formula to use. Editors’ note: Dr. Fam is a consultant for AMO (Abbott Park, Illinois) and Zeiss (Jena, Germany) but has no financial interests related to his comments. Considerations - from page 39