Femtosecond laser-assisted selective reduction of neovascularization in rat cornea

Abstract

Nonlinear multiphoton absorption induced by focusing near infrared (NIR) femtosecond (fs) laser pulses into a transparent cornea allows surgery on neovascular structures with minimal collateral damage. In this report, we introduce an fs laser-based microsurgery for selective treatment of rat corneal neovascularizations (in vivo). Contiguous tissue effects are achieved by scanning a focused laser pulse below the corneal surface with a fluence range of 2.2–8.6 J/cm2. The minimal visible laser lesion (MVL) threshold determined over the corneal neovascular structures was found to be 4.3 J/cm2. Histological and optical coherence tomography examinations of the anterior segment after laser irradiations show localized degeneration of neovascular structures without any unexpected change in adjacent tissues. Furthermore, an approximately 30 % reduction in corneal neovascularizations was observed after 5 days of fs laser exposure. The femtosecond laser is thus a promising tool for minimally invasive intrastromal surgery with the aid of a significantly smaller and more deterministic photodisruptive energy threshold for the interaction between the fs laser pulse and corneal neovascular structures.

Transient SHG Imaging on Ultrafast Carrier Dynamics of MoS2 Nanosheets

“…For the purposes of studying acoustic phonon generation and the associated heat diffusion induced by the weak van der Waals force in thin films, it is more useful to employ a pulse with an nJ‐level energy than one with a much higher fluence (>2 J cm −2 ) obtained with regenerative amplifiers. A high‐fluence pulse would likely create a “detachable” state of molecules or atoms (for laser‐induced deposition or laser‐based clinical surgery).…”

Ablation of Materials Using Femtosecond Lasers and Electron Beams

“…The numerical aperture (N.A) was 0.16. The laser spot was circular with a spot diameter of about 7.6 μm (measured at 1/e 2 in intensity) [50].…”

“…The minimal visible laser (MVL) lesion threshold was estimated for corneal neovascularizations (abnormal blood vessels grown under adverse conditions in the avascular cornea) by varying the laser fluence from 2.2 to 8.6 J/cm 2 . The area of a scan was 150 Â 150 μm, and the number of incident laser pulses (about 400) was kept constant [50].…”

Therapeutic approaches for corneal neovascularization

“…Kumar et al [ 55 ] reported a reduction of 7.01% and 44.08% in the area of corneal opacity and neovascularization, respectively, following frequency-doubled Nd:YAG (532 nm) laser photocoagulation at the end of 3 months follow up. An animal study showed that the femtosecond laser can be used for the management of corneal neovascularization with minimal collateral damage [ 59 ]. The cost of the equipment and lack of availability in most centres, however, limits the widespread use of this treatment.…”