Selective Shock Wave Therapy Of The Lens And Sclera For Accommodation Restoration And More

The concept of accommodation restoration (AR) with intra-lenticular femtosecond lasers has previously demonstrated safety, but unpredictable efficacy in primates and human subjects. Snipping of the posterior vitreous zonule (PVZ) has previously shown experimental AR in primate eyes. In this study, we are proposing a new non-invasive, non-thermal, non-ionizing shock wave energy source for enhancing the compliance of both the aging lens and the sclera overlying the PVZ for AR in presbyopic eyes. Additional ophthalmic applications are proposed.

Laboratory Setting

Electro-hydraulic shock wave generation is achieved through an ocular prototype device coupled to the eye. Electrical energies of 2-4 kV, 200-8,000 Hz frequency and 20-120 sec duration are applied in a sealed water bath to 100 porcine eyes and lenses using various exposure nomograms. The evaluation of outcomes included crystalline lens image quality in USAF targets, pars plana scleral and lens elastic softening with OCE (elastography), the detection of scleral vacuoles and supra ciliary spaces using OCT imaging and histology, and IOP reduction efficiency from 40 to 15 mm Hg using online intraocular pressure sensors. 

Using energy parameters of 2 kV, 2 kHz and 2 min duration, disaggregation, microporation and tissue softening was achieved in the porcine lens and sclera. The acoustic intensity, temperature and cavitation testing validated safety of the nomogram with no change in lens clarity. OCE demonstrated the ability to reduce lens and scleral elasticity by ~30-60%. Frequency-dependent microporation (vacuoles) were noted in the sclera with an increase in supraciliary spacing. Histology revealed no tissue destruction or coagulative effects. Furthermore, a 40% IOP reduction efficiency revealed enhanced outflow.

While the classic medical use of shock waves has been in lithotripsy (stone crushing), varying the energy, frequency, duration and geometry of delivery can achieve a host of microsurgical effects. In the quest for AR, this study reveals that microporation and modification of lens and scleral elasticity can be safely achieved, and also contribute to IOP lowering effects. Additionally, disaggregation of inspissated meibomian glands in Dry Eye/MGD, as well as enhancement of ocular permeability in drug delivery would also be feasible with selective shock wave therapy.