Pearls for the young cataract surgeon: Creating space in the shallow or crowded anterior chamber by intermittent globe compression

This column is one of an invited series by Dr. Osher. The series highlights techniques that may be helpful in particular to young practitioners. Every surgeon encounters a crowded or shallow anterior chamber, making the procedure more difficult and increasing the risk of complications. This column describes a noninvasive technique that deepens the anterior chamber and creates more room for the surgeon to perform an easier and safer cataract procedure. Several situations require the cataract surgeon to work in a shallow or "crowded" anterior segment.1 An anatomically narrow angle is not uncommon, while relative anterior microphthalmos or nanophthalmos are less often encountered.2,3 Nevertheless, the perils of operating in a shallow chamber are well-recognized and can result in iridial, capsular, or corneal endothelial damage and a higher risk of other intraoperative and postoperative complications.1–4 Previous reports have described an invasive technique for entering the pars plana and removing vitreous.1 Although effective in creating more space, there is a risk of damaging the lens, the zonular fibers, or the retina. The latter is especially true in nanophthalmos because it is difficult to know where the pars plana ends and the retina begins. For more than 3 decades, one of us (Osher) has been using a noninvasive 3-step approach for creating space in any narrow chamber. Surgical Technique Step 1. Approximately 20 minutes before the initial incision, the anesthesia team gives 50 mL of 20% mannitol intravenously. This hyperosmotic agent has a known hypotonic effect by dehydrating the vitreous. Step 2. A muscle hook or an Osher Sweep is inserted into the inferior conjunctival fornix (Figure 1). Intermittent upward compression of the globe against the superior orbital rim, analogous to scleral depression, is performed intermittently for about 1 or 2 minutes, relieving the pressure every few seconds to allow arteriole perfusion to the globe (Video 1, https://links.lww.com/JRS/A619).Figure 1.: The Osher Sweep design is compared with a standard muscle hook. The sweep is placed into the inferior fornix to intermittently compress the globe upward against the superior roof of the orbit. Every few seconds, the pressure is released to restore blood flow to the eye.Step 3. After an incision is carefully constructed with an anterior entry to avoid the greater tendency to traumatize the peripheral iris or induce iris prolapse, a retentive ophthalmic viscosurgical device (OVD), such as Healon 5 (Johnson & Johnson Vision), is injected. The surgeon must exercise caution to avoid injuring Descemet membrane by depressing the floor of the incision as the cannula enters the anterior chamber. Injection of the OVD should be performed when the cannula has reached the mid-pupil to prevent an inadvertent Descemet detachment. The anterior chamber deepens, and the surgeon may continue the procedure in a safer environment. Discussion This technique has been very effective in safely creating space in eyes with a cramped anterior segment. Regardless of the etiology of the shallow anterior chamber, the surgery is more complex with a higher risk of complications. Although a closed-system approach such as phacoemulsification has reduced the frequency of iris prolapse, choroidal effusion, and choroidal hemorrhage, the ultrasound energy or the ultrasound tip itself is capable of causing iris or corneal damage. Deepening the chamber increases the safety of the phacoemulsification while making nucleus disassembly and cortical removal more straightforward for the surgeon. Retaining the OVD throughout the emulsification can be achieved by lowering the parameters, which adds safety by creating a physical barrier between the ultrasound tip and the corneal endothelium.5 When the OVD fails to deepen the shallow chamber sufficiently, an automated pars plan vitreous tap has been reported to facilitate small-incision cataract surgery.1 However, pars plana vitrectomy is more aggressive and risks unintentional damage to the lens, zonular fibers, vitreous hemorrhage, or retinal trauma.6 This is especially true in nanophthalmic eyes because of the variability of the retinal anatomy. Our technique is less invasive, simple to perform, safe, and very effective in creating space. Every first-year resident who has performed scleral depression has noticed that the eye becomes soft by dehydrating the vitreous. When combined with intravenous mannitol and a retentive OVD, intermittent globe compression results in an easier surgical procedure with less risk for intraoperative complications.