High Intensity Focus Ultrasound (HIFU) to Breakdown Lens for Cataract Surgery

Abstract

 

Purpose:

 

To study the effects of non-invasive HIFU on porcine lenses

 

Methods:

 

Porcine lenses were hardened by soaked in 10% formalin (for 1,2,3,5 minutes) then were treated with HIFU (4 MHz transducer focused at 40 +/- 1.64mm for 1,2, 3 minutes) and compared to untreated porcine lenses (no HIFU). Temperature was kept constant at 36º, 40º or 46ºC. The following measurements were then performed: 1) lens hardness using the Bose System (Bose Corporation USA, MN); 2) Sound velocity through the lens (Panametrics USA, MA); 3) Phacoemulsification energy (power X time of ultrasound - Millennium, Bausch & Lomb USA, NY); 4) Transmission electron microscopy (TEM, JEOL USA, MA) to analyze HIFU-induced anatomical changes.

 

Results:

 

Force (Bose measurements) was decreased in lens soaked for 2,3 minutes in formalin treated with 1,2,3 minutes of HIFU at 36 º, 40º and 46ºC. (Table 1). Sound Velocity was significantly decreased for lenses treated with HIFU for 2 minutes and 36ºC (p=0.02, p=0.03 respectively). Phaco energy was significantly reduced for lenses measured in formalin 1,2,3,5 minutes with HIFU for 2,3 minutes at 36ºC. All others values were not statistically significant. Post-HIFU TEM revealed changes in the center of the lens: spreading of membrane spaces and vacuole formation. There was no damage in the lens capsule.

 

Conclusions:

 

HIFU affects lens integrity primarily through mechanical sheering; temperature changes are secondary since the best results were at 36ºC.  

 

Keywords: cataract • intraocular lens • cell adhesions/cell junctions