EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/78712
April 2012 Tools & techniques "Inside-out" approach to posterior polar cataracts by Abhay R. Vasavada, M.S., F.R.C.S., and Shetal M. Raj, M.S. A lthough most posterior polar cataracts tend to be on the softer side at the time of their removal, they can still be some of the more complex cataract extractions. The thinned and weakened posterior capsule has been reported to rupture in 26-36% of these cases. Certain precau- tions can be taken such as avoiding downward pressure on the capsule, avoiding hydrodissection, avoiding ex- cessive rotation of the endonucleus, and working within the safety of an epinu- clear shell. In this month's column, one of the world's most experienced sur- geons, Abhay Vasavada, M.S., F.R.C.S., gives tips and pearls for dealing with the posterior polar cataract. His inside- out hydrodelineation technique is a use- ful method for insuring safe creation of an epinuclear shell while placing mini- mal stress on the posterior capsule. His step-by-step instructions should help us all lower our rate of capsule rupture in these difficult cases. Richard Hoffman, M.D., Tools & techniques editor Watch this video on your smartphone or iPad using your QR code reader. (Scanner available for free at your app store.) Or view the video of Dr. Vasavada's procedure at www.eyeworld.org/replay.php. P osterior polar cataracts pose a unique challenge to the surgeon owing to the high risk of posterior cap- sule dehiscence during emulsification. It has been observed that the risk of posterior capsule rup- ture (PCR) increases with performing conventional cortical cleaving hy- drodissection. The speculation is that injecting balanced salt solution in the capsular bag with an intact nucleus rapidly builds up the hy- draulic pressure within the bag. This pressure is adequate to split the cap- sule at the site of the polar opacity as fluid passes through the area of least resistance. Other risk factors that could cause a PCR in eyes with posterior polar cataracts (PPC) are sudden and excessive forward move- ment of the iris-lens diaphragm, pre- mature cleavage of the opacity from the capsule, or attempts to polish the central plaque opacity on the posterior capsule. To circumvent this eventuality and to facilitate nucleus removal during phacoemulsification in eyes with posterior polar cataract, we devised the inside-out delin- eation approach. Pre-procedure evaluation PPC has to be distinguished from the posterior subcapsular cataract. PPC is characterized by a central, dense, disk-shaped opacity located on the posterior capsule with con- centric rings around the central plaque opacity that appear like a bull's eye. The opacity has a cone- shaped projection in the subcapsular region or central posterior cortex. The posterior subcapsular cataract is rather flat and does not have dis- tinctly demarcated central ring opac- ity. PPC could also have co-existing nuclear or cortical opacities. Noting the integrity of the posterior capsule could help explain the prognosis to the patient. Rationale It is widely accepted that cortical cleaving hydrodissection should be avoided during emulsification of posterior polar cataracts as it in- creases the risk of posterior capsule rupture. Conventional hydrodelin- eation is instead performed, wherein the cannula is penetrated within the lens substance in an attempt to cause the fluid to traverse between the nucleus and epinucleus. With this there remains a possibility of fluid being injected inadvertently between the opacity and the cap- sule, leading to unwarranted hy- drodissection. Also at times it may be difficult to introduce the cannula within a firm nucleus leading to rocking and stress to the capsular bag and zonules. With inside-out delineation fluid is injected at a desired depth, under direct vision. A precise demar- cation of the central core nucleus from the epinucleus provides a thick epinucleus bowl. This bowl acts as a mechanical cushion and a barrier that protects the posterior capsule during subsequent maneuvers. Instrumentation, anesthesia, and technique A. Instrumentation • Operating microscope with good coaxial illumination • Dispersive viscoelastic: I prefer chondroitin sulfate (Viscoat, Alcon, Fort Worth, Texas). • A specially designed 27-gauge right-angled cannula facing the right and the left side B. Anesthesia • Peribulbar anesthesia is advisable for novice surgeons; with experi- ence topical anesthesia could be administered. C. Technique • A moderate-sized continuous curvilinear capsulorhexis is cre- continued on page 18 EW NEWS & OPINION 17 Figure 1. A moderate-sized continuous curvilinear capsulorhexis is created Figure 2. A central trench is sculpted using the slow motion technique Figure 3. A dispersive viscoelastic is injected through the side port before retracting the probe to maintain a closed chamber Figure 4. A specially designed right- angled cannula is introduced through the main incision to reach the central trench Figure 5. The tip of the cannula is placed adjacent to the left wall of the trench at an appropriate depth Figure 6. Fluid is injected slowly with minimal force through the left wall of the trench Source (all): Abhay R. Vasavada, M.S., F.R.C.S., and Shetal M. Raj, M.S.