Ophthalmic viscosurgical devices for intumescent cataracts: Pressure-equalized cataract surgery

I read with great interest the article by Hengerer et al.1 They presented a small study that shows the value of using trypan blue and increasing the anterior chamber pressure anterior to the anterior capsule using highly viscous ophthalmic viscosurgical devices (OVDs) for intumescent cataract cases. It is important for cataract surgeons to be aware of this principle, and I congratulate the authors on its demonstration. I do, however, have a few comments about the paper. First, the study did not show any value of the variant of the soft-shell technique used by the authors in Group 2; it simply stated the advantage of using a very highly viscous viscoadaptive OVD, which enabled the intraocular pressure to be increased in front of the anterior capsule. Ophthalmic viscosurgical devices with lower viscosity used in conjunction with viscoadaptives do not contribute to pressurization of the chamber but allow the pressure induced by the highly viscous and elastic viscoadaptives to be transmitted through the lower viscosity OVD, because the 2 OVDs are confined together in a single space, even if that lower viscosity OVD is a balanced salt solution, as in the ultimate soft-shell technique. Soft-shell techniques use dispersives, or water-based solutions of drugs, in conjunction with viscoadaptives, because they add additional benefits to the procedure, while the viscoadaptives contribute pressurization. The use of Healon, in addition to Healon5, really does not add an additional benefit in the situation presented here. Second, the authors did not refer to the OVDs with their accepted classification categories. The current classification of OVDs is shown in Figure 1, updated as indicated from Arshinoff and Jafari.2 Ophthalmic viscosurgical devices should be described indicating where they fit into this classification because of the numerous OVDs currently available and confusing conflicting claims about their properties. Ophthalmic viscosurgical devices in the same class share similar properties, making their behavior more understandable to the surgeon when choosing among them for a given task.Figure 1: The current classification of OVDs, updated and modified from Arshinoff and Jafari 20052 (CDI = cohesion-dispersion index [percentage aspirated/mm Hg]; HPMC = hydroxypropyl methylcellulose; mPA.s = millipascal-seconds; OVDs = ophthalmic viscosurgical devices) (*Manufactured by Abbott Medical Optics, Inc. **Sold by iMed Pharma. ***Manufactured by Bohus Biotech AB. #Sold by Bectin, Dickenson and Co. ##Manufactured by Carl Zeiss Meditec AG. ###Manufactured by Bausch & Lomb (Croma-Pharma GmbH). †Manufactured by Alcon Laboratories, Inc. +Manufactured by Bausch & Lomb. †††Manufactured by Bio-Technology General (Israel) Ltd. ???Manufactured by Rayner Intraocular Lenses Ltd.?Manufactured by Shisheido Co. Ltd. ††Manufactured by Seikagaku Corp. – Santen, Inc. *Available in the United States).Third, the authors failed to refer to preceding work discussing the principle they “discovered.” The principle that increasing pressure in front of the anterior capsule of an intumescent lens, using a viscoadaptive OVD to indent the capsule, making it change from convex anteriorly to slightly concave, and thereby directing erratic tears inward rather than equatorially, has been presented by me at numerous successive OVD courses at American Society of Cataract and Refractive Surgery, European Society of Cataract and Refractive Surgeons, American Academy of Ophthalmology, and Canadian Ophthalmological Society meetings and other meetings every year for more than a decade. Figure 2 is a copy of one of my lecture slides. It shows the principle of pressure-equalized cataract surgery, as I have termed it and taught it, illustrating the purpose of increasing pressure in front of the anterior capsule.Figure 2: If a high-viscosity cohesive OVD (the only ones that are really elastic) is used to pressurize the anterior chamber, so that the pressure in front of the anterior capsule exceeds the pressure behind it, the usually convex anterior capsule develops a central concavity. In this situation, a capsulorhexis will always tend to tear centrally rather than peripherally and the Argentinean flag sign will not occur (AC = anterior chamber; HMW NaHa = high-molecular-weight sodium hyaluronate; IOL = intraocular lens; OVD = ophthalmic viscosurgical device).This technique has also been mentioned in OVD articles published by me in the Journal of Cataract & Refractive Surgery and numerous trade journals. Many of my articles and videos have alluded to the technique, but the tri-soft shell article3 most succinctly amalgamates all soft-shell techniques into a single paradigm and on the final page, specifically discusses increasing the pressure of the area anterior to the anterior capsule of mature white cataracts using viscoadaptives. I thank the authors for confirming what I have been teaching ever since Healon5 became available in 1998 and respectfully request that they acknowledge previous publications in their paper, which elegantly confirms the value of pressure-equalized cataract surgery.

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