Abstract
Introduction: Globally, at least 30 million cataract surgeries are required annually to prevent cataract-related blindness. Corneal endothelial decompensation is one of the most common causes of poor visual outcome following cataract surgery, particularly in those with predisposing factors. The increasing ageing population and reduced visual impairment threshold for cataract surgery have resulted in rising cataract surgical rates and hence, an increase in corneal endothelial decompensation is expected. The role of phaco tip position on corneal endothelial damage is ambiguous. Previous studies have reported contradictory results and were also underpowered to detect a significant difference due to small sample sizes. With no consensus regarding the most cornea-friendly phaco tip position (bevel-up versus bevel-down) during phacoemulsification, we propose a randomised clinical trial with a robust design using direct chop phaco-technique. Objective: To compare the effect of phaco tip position (bevel-up vs. bevel-down) on corneal endothelial cell count during phacoemulsification. Methods: A randomised, multicentre, parallel-group, triple-masked (participant, outcome assessor, and statistician) trial with 1:1 allocation ratio is proposed. By adopting stratified randomisation (according to cataract grade), we will randomly allocate 480 patients aged >18 years with immature cataract into bevel-up and bevel-down groups at two centres. History of significant ocular trauma, previous intraocular surgery, shallow anterior chamber, low endothelial cell count, pseudoexfoliation syndrome, intraocular inflammation, and corneal endothelial dystrophy are the key exclusion criteria. The primary outcome is postoperative endothelial cell count at one month. Secondary outcomes are central corneal thickness on postoperative days 1, 15, and 30, and intraoperative complications. Trial registration: Clinical Trial Registry of India CTRI/2019/02/017464 (05/02/2019).
Highlights
At least 30 million cataract surgeries are required annually to prevent cataract-related blindness
It is speculated that the phaco tip, considered to be the source of heat, when kept away from the corneal endothelium with the bevel-up technique might result in minimal cell loss[22]
central corneal thickness (CCT) is known to display diurnal variation; being thickest in the morning and gradually thinning as the day progresses[30,31,32,33]. To answer this long-standing clinical question, we propose a randomised clinical trial with a robust study design using direct chop phacoemulsification technique and specular microscopy, which can non-invasively analyse the morphology of endothelial cells
Summary
Cataract causes blindness or moderate to severe visual impairment in about 62.5 million people globally[1]. It is speculated that the phaco tip, considered to be the source of heat, when kept away from the corneal endothelium with the bevel-up technique might result in minimal cell loss[22] In this position, the cavitational energy is directed towards the endothelium, which may have a negative impact. CCT is known to display diurnal variation; being thickest in the morning and gradually thinning as the day progresses[30,31,32,33] To answer this long-standing clinical question, we propose a randomised clinical trial with a robust study design using direct chop phacoemulsification technique and specular microscopy, which can non-invasively analyse the morphology of endothelial cells
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