Effect of Air Injection Depth on Big-bubble Formation in Lamellar Keratoplasty: an Ex Vivo Study

Abstract

This study evaluated the effect of air injection depth in the big-bubble (BB) technique, which is used for corneal tissue preparation in lamellar keratoplasty. The BB technique was performed on ex vivo human corneoscleral buttons using a depth-sensing needle, based on optical coherence tomography (OCT) imaging technology. The needle tip, equipped with a miniaturized OCT depth-sensing probe, was inserted for air injection at a specified depth. Inside the corneal tissue, our needle obtained OCT line profiles, from which residual thickness below the needle tip was measured. Subjects were classified into Groups I, II, III, and IV based on injection depths of 75–80%, 80–85%, 85–90%, and >90% of the full corneal thickness, respectively. Both Type I and II BBs were produced when the mean residual thicknesses of air injection were 109.7 ± 38.0 µm and 52.4 ± 19.2 µm, respectively. Type II BB (4/5) was dominant in group IV. Bubble burst occurred in 1/16 cases of type I BB and 3/16 cases of type II BB, respectively. Injection depth was an important factor in determining the types of BBs produced. Deeper air injection could facilitate formation of Type II BBs, with an increased risk of bubble bursts.

Modified big bubble technique for deep anterior lamellar keratoplasty in keratoconus

“…Different techniques are introduced by applying air, fluid or viscoelastic injection to facilitate deep lamellar dissection. [13][14][15][16][17][18][19][20][21][22][23][24] In the Anwar's big bubble technique, 23 after trephination up to 80% of the stroma, the air is injected into the deep stroma. When the "Big Bubble" is formed the superficial layers of the stroma is resected to reach the bubble outer wall.…”

Data-Driven Modelling and Control for Robot Needle Insertion in Deep Anterior Lamellar Keratoplasty

“…We evaluate the method on ex vivo corneas and find that it outperforms the state-of-the-art [ 13 ] in terms of both final error in cornea depth achieved by the needle (3.96 ± 1.48% vs 7.80 ± 3.37% for a target depth of 90%) and in terms of vertical error (43.29 ± 15.78 μ m vs 75.71 ± 33.90 μ m). Furthermore, the method achieves less than 5% error in relative depth (the threshold found by Yoo et al [ 6 ] to be associated with reliable control of bubble type) in 61% of trials, as opposed to 42% for the baseline.…”

“…Type I bubbles form within the stroma, while type II bubbles form deeper, between the stroma and the Descemet’s Membrane. Depending on the type of bubble formed, the surgeon will have to modify the graft preparation [ 6 ]. Moreover, the type of bubble impacts the perforation rate and the histological properties of the graft [ 6 ], [ 7 ].…”

“…Depending on the type of bubble formed, the surgeon will have to modify the graft preparation [ 6 ]. Moreover, the type of bubble impacts the perforation rate and the histological properties of the graft [ 6 ], [ 7 ]. Thus, it is highly desirable to control the type of bubble formation.…”

“…Thus, it is highly desirable to control the type of bubble formation. Yoo et al [ 6 ] found that the relative depth of the needle within the cornea is an important factor for both the success rate and type of bubble formation. They found that type I bubbles were consistently formed when the relative depth of the needle was between 75% and 85%, while type II bubbles dominantly formed for depths greater than 90%.…”