Cortical Cleaving Hydrodissection

Field: Medicine (Health Sciences)

Reply: We thank Dr. Fine for his thoughtful letter regarding what we believe is a very important and often underrated surgical technique. As we noted in our article, intraoperative subcapsular injection of fluid (in particular, cortical cleaving hydrodissection in which the anterior capsular flap is tented up by the injection cannula),1 is an essential maneuver in enhancing cortical and cellular removal and cleanup. Our studies reveal that its increased use is an important reason that the incidence of posterior capsule opacification (PCO, secondary cataract, after cataract), one of the last nagging (and expensive) complications of modern cataract surgery, is now beginning to decrease toward single digits (D.J. Apple, MD, Q. Peng, MD, “Histopathological Study of Posterior Capsule Opacification with Different IOLs,” presented at the annual meeting of the American Academy of Ophthalmology, Orlando, Florida, USA, October 1999). Based on our laboratory research, we have recently identified 6 important factors in reducing PCO. Hydrodissection, specifically subcapsular or cortical cleaving hydrodissection, is the first of these factors. Until recently, the hydrodissection component of the cataract procedure has too often been used primarily to enhance the surgical ease of lens substance removal and the general safety of the operation. For example, most surgeons focus on facilitation of nucleus removal from the capsular bag without excessive zonular stress. Hydrodissection is rarely seen as a procedure that is highly efficacious in removing cortex and cells to combat PCO. For example, in Gimbel's review of hydrodissection and hydrodelineation in 1994, PCO was scarcely mentioned.2 It is often forgotten that retained cortex, the material within the postoperative peripheral Soemmering's ring, is composed of not only acellular, amorphous, proteinaceous lens fibers and strands but also clusters of residual equatorial lens epithelial cells. The latter are the actual precursors of clinical PCO. Thorough removal of these is critical in controlling PCO, and the hydrodissection maneuver is the most useful tool for this. The method described as cortical cleaving hydrodissection by Fine in 1992 as well as in his letter is precisely what is needed to achieve this long-term goal. Realizing now that this component of the cataract operation has quietly emerged as one of the numerous stellar achievements and improvements in cataract surgery provided by many surgeons over the years, a brief look back at its evolution is fitting. Gimbel has done this, providing an excellent clinical review.2 He outlines how various agents such as viscoelastic agents, Ringer's solution, and balanced salt solution have been tried throughout the years. The article by Faust that we cited3 includes the first use of the term hydrodissection in the refereed literature. Faust's sketches of the procedure were among the first to illustrate the general principles of this technique. We conducted the first systematic laboratory studies on the various hydrodissection/delineation techniques in 1989 (D.J. Apple, MD, R. Casanova, MD, J. Davison, MD, “Technique of PC IOL Implantation Using a Small Smooth Circular Continuous Tear Capsulotomy (Capsulorhexis); a Demonstration Using the Posterior Video Technique on Human Cadaver Eyes,” video presented at the annual meeting of the American Academy of Ophthalmology, New Orleans, Louisiana, USA, October 1989). Assia and coauthors4 continued this research into the pathophysiology of the various types of intralenticular injection. Fine's procedure, which is highlighted by the fact that he tents up the anterior capsule during injection, reduces or eliminates the need for cortical aspiration in many cases. It represents the culmination and near perfection of this technique, which now serves us so well. The significance of our recent article is that it has, for the first time, called attention to the direct relationship between hydrodissection and PCO. The hydrodissection procedure itself, although never an attention getter in comparison to, for example, intraocular lenses and other biodevices and instruments, has been a close partner on our road to success with the cataract operation. David J. Apple MD Qun Peng MD