Comparison of effective phacoemulsification time and corneal endothelial cell loss using three different ultrasound frequencies in phacoemulsification

Phacoemulsification is today the most popular surgery for cataract worldwide. The nucleus is emulsified using a machine which provides energy for emulsifying the nucleus and generates a vacuum for aspirating the cortex. The method is constantly being improved to minimize the risk of complications, particularly tearing of the capsule and dropping of the nucleus into the vitreous ,and corneal endothelial damage.1 Effective phaco time is time taken to remove cataract if continuous 100% phaco power is used. Lower the effective phaco time, lower the energy delivered in the eye and thus clearer the cornea with better visual rehabilitation.2

 Phacoemulsification is ultrasound based dissolution of lens matter. The piezoelectric crystal imparts a specific frequency vibratory motion to the phaco tip which when interacts with the lens matter in a fluid based environment leads to disintegration and dissolution of the cataractous lens. It is in accordance with the principles of physics that subjecting a solid to a frequency matching its internal resonant frequency would lead to disintegration of intermolecular bonds and make it easily aspirable. Biological experiments have shown supporting evidence in other human tissue.3

 Increasing hardness of cataract is associated with change in chemical and physical properties in the crystalline lens and should logically require a change in frequency of ultrasound. However different machines, though within the range of 22-60 kHz, use the same frequency ultrasound (inherent to the machine) for all grades of cataract and hence end up with higher effective phaco time in hard cataract.4

 Higher effective phaco time is associated with increase in endothelial damage5and using optimal frequency should reduce effective phaco time and hence corneal endothelial loss during phaco. So far the studies have compared machines with different frequencies in cataract but unique phacodynamics of each machine brings in other confounding variables making the results questionable. In a pilot study we found lower effective phaco time with use of higher frequency ultrasound6. Based on these results an RCT was conducted after ethical approval comparing 28 and 42 kHz frequencies in the same machine Megatron S4. The result showed decrease in effective phaco time and endothelial cell loss with use of higher frequency. The present Geuder

 Megatron S4 HPS phaco machine delivers ultrasound frequency range from 27-55 kHz. We wish to conduct a randomized controlled trial comparing three frequencies 28kHz, 42kHz, and 55kHz in the same machine in patients with identical parameters and see if we arrive at statistically significant results through the comparison.

 RESEARCH QUESTION

 Is there any difference in effective phaco time and endothelial cell loss between three different ultrasound frequencies in phacoemulsification?

HYPOTHESIS

There is difference in effective phaco time and endothelial cell loss between three different ultrasound frequencies in patients of cataract undergoing phacoemulsification