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Anne-Marie Jablonka, Niklas Alexander Maierhofer, Hessam Roodaki, Abouzar Eslami, Daniel Zapp, Ali Nasseri, Chris Patrick Lohmann; The effect of needle entry angle on bubble formation in DALK using the big-bubble technique. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1862.
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© ARVO (1962-2015); The Authors (2016-present)
Successful big-bubble formation in Deep Anterior Lamellar Keratoplasty (DALK) using the big-bubble technique is crucial to the outcome of the procedure. Parameters including but not limited to the needle size, the length of the induced tunnel and most notably the achieved depth of injection play a role in success of pneumodissection. Continuous monitoring and adjusting of these parameters have become feasible with the advent of intraoperative Optical Coherence Tomography (OCT). In this study, the role of the needle angle on entry is investigated with regards to the success in bubble formation.
OCT guided cannulation and air injection was performed on 23 ex-vivo porcine eyes using a custom-made robot and 30G needles. Upon inspection of volumetric OCT acquisitions, the mean angle of entry relative to the corneal central surface was observed to be 23.3° in 19 cases with successful deep air deposits compared to 29.6° for 3 cases with superficial air deposits. However, the mean length of the induced tunnel was similar in both cases (1.72mm and 1.71mm for successful and superficial cases respectively). To test the hypothesis that steeper entry angles are a factor in pneumodissection failure, a second set of robotic DALK simulations using the big-bubble technique were performed on ex-vivo porcine eyes. The angle of entry in each case was deliberately targeted to be either 23° or 30° using OCT. The outcome of the task and volumetric OCT acquisitions were captured.
A total of 11 eyes were cannulated. Out of 6 cases with angle of entry set to 23°, 5 were successful with deep air deposits manifesting indications as similar as possible to pneumodissection that is observable in porcine models. However, all 5 trials with angle of entry set to 30° led to superficial air deposits and failure.
A strong correlation between the needle entry angle and successful deep air deposits is observed in porcine models. Shallower entry angles (~23°) increase and steeper angles (~30°) decrease the chance of successful deep air deposit.
This is a 2020 ARVO Annual Meeting abstract.
Cross-sectional OCT views of simulated DALK on ex-vivo porcine eyes. Steep entry angles (A) typically result in superficial bubble formations whereas shallow entry angles (B) usually result in deep bubble formations.
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