Cataract measurement by estimating the ultrasonic statistical parameter using an ultrasound needle transducer: an in vitro study.

A cataract is a clouding of the crystalline lens that reduces the amount of incoming light and impairs visual perception. Phacoemulsification is the most common surgical method for treating advanced cataracts, and the optimal phacoemulsification energy is determined by the lens hardness. A previous study proposed using the ultrasonic Nakagami image to complement the B-scan for distinguishing different degrees of lens hardening. However, it is difficult to implement the use of an imaging probe to detect the lens during phacoemulsification surgery in a clinical situation. To resolve this problem, this study applied an ultrasonic needle transducer to estimate the Nakagami parameter as an alternative for characterizing the cataract lens. Cataracts of porcine lenses were artificially induced in vitro, and the Young's modulus, backscattering intensities, and the Nakagami parameters were measured. The results showed that the backscattering intensity was not correlated with Young's modulus. In contrast, the average Nakagami parameter increased from 0.34 to 0.95 with increasing Young's modulus of the lens from 1.71 to 101 kPa. The above findings showed that the Nakagami parameter estimated with a needle transducer may be useful in differentiating different degrees of lens hardening, and implied that determining the optimal ultrasonic energy during clinical cataract surgery is possible if the needle transducer can be combined with the phacoemulsification probe to estimate the Nakagami parameter.