Mid-Infrared Diode Laser Scleral Therapy (L S T) For Accommodation Restoration And Aqueous Outflow: Preclinical & Initial Pilot Study

Laser induced heating of collagen tissues can induce both collagen shrinkage and softening (enhanced tissue compliance) when targeted at temperatures of 55-70 deg C.  Scleral collagen becomes more rigid with age, and contributes to the loss of accommodation and reduction of aqueous outflow in aging eyes.  Our purpose is to explore the use of a portable, infrared diode laser in treating the anterior sclera to modify its anatomical structure and collagen tissue properties in pursuit of a potential therapy for presbyopia and glaucoma.

Laboratory Studies in Germany and Czech Republic and pilot human studies in Slovakia

Porcine eyes were studied using 3 laser sources to identify the ideal wavelength and penetration depth.  After identifying the 1.55 um pulsed fiber laser, as the ideal source, pulsed treatments with an energy of ~1 Joule/sec, 1 MHz, 2 nsec for 30-90 sec were made through a diffractive optical element, projecting a 12-18 mm diameter annulus onto the sclera.  Ocular coherence tomography (OCT), ocular coherence elastography (OCE), tissue histology and aqueous outflow studies were used to characterize the anatomical and biomechanical effects.  After signing an informed consent, 6 presbyopic volunteers (ages 45-70 yrs) were treated with the above parameters as a pilot trial, and were asked to report their subjective experience.

Infrared lasers of 2.1 um, 1.45 and 1.55 um were studied for their depth and uniformity of penetration with the latter being optimal for deeper scleral treatment without denaturation.  At 1.55 um, OCT shows uniform specular reflection and a mean greater AC angle opening of 4 degrees.  Histological sections of treated vs. untreated sclera depict iris and ciliary body (CB) translocation outward and backward.   OCE reveals a 2/3rd reduction of elastic rigidity in treated sclera.  Aqueous outflow showed >30% IOP decline and increase in aqueous outflow.  All 6 subjects maintained good centration with minimal conjunctival hyperemia and discomfort. All reported improvement in unaided reading vision with no perceived change in distance correction.

Pulsed, mid-infrared laser treatment of the perilimbal sclera overlying the ciliary body and posterior vitreous zonule insertion can both translocate the iris/ CB complex and increase the scleral compliance, showing promise as a low cost, portable method for restoring accommodation and improving aqueous outflow.  Early clinical safety and subjective visual improvement warrants further studies in aged human cadaver eyes to confirm preclinical findings prior to pursuing formalized clinical trials.