Intraocular Pressure and Big Bubble Diameter in Deep Anterior Lamellar Keratoplasty: An Ex-Vivo Microscope-Integrated OCT With Heads-Up Display Study

Abstract

Purpose To investigate the relationship between intraocular pressure (IOP) and big bubble (BB) formation in an ex-vivo model of deep anterior lamellar keratoplasty (DALK). Design Ex-vivo Methods Corneo-scleral buttons from human donors were loaded onto an artificial anterior chamber connected to a column of balanced salt solution. A surgeon-in-training learned to perform DALK via the BB technique using swept-source microscope-integrated optical coherence tomography (SS-MIOCT) with heads-up-display (HUD). DALK procedures were performed at six different IOPs (5, 10, 15, 20, 30, or 40mmHg; n=6 per group) in a randomized fashion, with the surgeon-in-training masked to the pressure and guided by SS-MIOCT with HUD. For a subset of corneas within each pressure group, DALK was performed on matching donor tissue at a control IOP. BB diameter was recorded, and a diameter exceeding the trephine diameter was considered optimal. Results Wilcoxon rank sum test showed a difference in BB diameter amongst the different pressure groups (mean±standard deviation of 7.75±1.60mm, 8.33±1.99mm, 10.9±0.92mm, 9.08±1.07mm, 6.67±3.33mm, and 3.42±3.77mm in the 5, 10, 15, 20, 30, and 40mmHg groups, respectively; p=0.0014). Per Tukey test, this difference was attributable to comparisons between the 40mmHg group and the 5, 10, 15, or 20mmHg groups (p=0.04, 0.02, 0.0001, 0.004, respectively). Conclusion In this ex-vivo model of DALK, the BB technique guided by SS-MIOCT with HUD, yielded bubbles of optimal diameters only at physiologic pressures (10–20mmHg). Extremely high IOP (40mmHg) resulted in BBs of significantly smaller diameter than BBs obtained at physiologic and low (5mmHg) IOPs.

<p>Intraoperative Optical Coherence Tomography Guided Ocular Surgeries: Critical Analysis of Clinical Role and Future Perspectives</p>

“…13 Several observations were of the opinion that, with iOCT in DALK, the plane of canula introduction, its effect on big bubble morphology and subsequent manual dissection, and suture depth sagacity are all well executed. 14 In addition, the effect of intraocular pressures on the success of big bubble technique, 15 interface events during surgery, 16,17 and the added advantage of femtosecond laser in the customization of intraoperative parameters have all provided the inclusive notions for using iOCT. 18 Under complex clinical scenarios, such as the identification of superficial fibrovascular tissue in severe limbal stem cell deficiency, iOCT helps in the discretion of abnormal tissue from normal, thus preventing excessive resection of healthy tissue.…”

Deep anterior lamellar keratoplasty: A surgeon's guide

“…Extremely high IOPs (40 mmHg) resulted in big bubbles of significantly smaller diameter than those obtained at physiologic and low (5 mmHg) IOPs. 56 …”