Eye Care Research and Patents
TANGENTIAL LASER PHOTOREFRACTIVE KERATECTOMY
BARRY MILES BELGOROD, M.D.
BMB PATENT HOLDING CORPORATION
200 EAST 72 STREET
NEW YORK, NY 10021
A. Specific Aims
The long-term objectives of the Tangential Laser Photorefractive Keratectomy (Tangential PRK) project are the development of ultra-precise instruments and procedures for the correction of the four types of refractive errors of the eye (myopia, hyperopia, astigmatism and presbyopia). Tangential PRK is defined as the kerato-refractive surgery procedure that utilizes the precisely contoured edge of the laser beam to remove microscopic quantities of corneal tissue tangentially. The objectives of the proposed research are to design, fabricate and test annular aspheric prisms of the delivery system for selected post-operative corneal curvatures. The commercialization of the instruments and procedures is intended to permit the ophthlamic community to achieve clear, prosthesis-free, visual acuity for Americans.
From the dawn of scientific method, mankind has attempted to overcome the imperfections in the optics of the eye known as refractive errors. The first documented use of a prosthesis to improve visual acuity may be attributable to Seneca in describing an ancient maginfying device for improving near acuity. Later attempts include spectacles and, more recently, contact lenses. In an attempt to free patients from the need for prosthetic visual correction, surgical procedures have been investigated, with varied results. Clear lens extraction was proposed in 1890 followed by unsuccessful scleral shortening procedures. It was not until Sato proposed radial endothelial incisions in the cornea for the treatment of keratoconus in the 1940’s, that the present goal of surgical modification of corneal curvature to eliminate refractive errors became a possibility. Due to endothelial loss and eventual corneal opacification, the Sato technique was abandoned.
Modern kerato-refractive surgery was initiated by Barraquer in the 1960’s with reshaping of resected anterior corneal lamellae. Keratophakia, keratomileusis and epikeratophakia are such procedures and are limited by scarring in the corneal stromal interfaces, inaccuracy, complicated procedures and expense. In the 1970’s keratotmy procedures were revived by Fyodorov, now making multiple incisions in the anterior corneal surface. Poor predictability, post-operative instability, significant decrease in impact resistance, scarring, glare, vision fluctuation and irregular induced astigmatism have limited the success of these procedures. Intracorneally implanted lenses and rings may be prone to extrusion. Thermokeratoplasty to shrink corneal collagen has repeatedly proven unstable.
In the 1980’s, laser procedures to reshape the cornea by tissue ablation were proposed. Among these, intrastromal ablation using infrared wavelengths to cause cavitation has not yet reportedly yielded the precision necessary to achieve predictable post-operative results. Surface ablation using the excimer laser in a non-tangential, en face approach, as currently under FDA investigation protocols, etches layers of varying diameters of corneal stroma with each pulse. Significant drawbacks to this approach are attributable to high degrees of variability of ablation depths per pulse (as seen in Fig 1 with ablation rates in microns/pulse).
Spectacle lens having continuously variable controlled density and fast response time
A spectacle lens comprises a liquid crystal layer and electrode assembly sandwiched between a pair of identically curved glass plates and layers of polarization material on the outer surfaces of the plates. The optical density of the lens is controlled by applying across the electrodes variable duty cycle voltage pulses having a magnitude greater than a threshold voltage of the liquid crystal layer and a frequency at least as great as the critical flicker fusion frequency of the eye. The duty cycle of the pulses is controlled in response to ambient light intensity measured by a photocell. In order to reduce response time and increase operating lifetime of the liquid crystal layer, tir-level (+V, 0, -V) rather than bilevel (+V, 0) pulses may be applied to the liquid crystal electrodes.
Method and apparatus for modification of corneal refractive properties
A method and apparatus for modifiying corneal refractive properties includes a laser source, computer control, and a plurality of deflectors including at least one rotating and translating deflector. A beam emitted from the laser source is deflected by the rotating and translating deflector in a controlled manner such that the beam strikes the cornea tangentially, ablating or lathing the contacted surface. The apparatus is computer controlled to intra-operatively determine the visual axis, monitor fixation, monitor changing refractive error, adjust the rotating and translating deflector and activate and deactivate the laser. The invention allows the radius of curvature of the cornea to be modified in vivo or in vitro. The cornea is lathed tangentially in either a natural or frozen state in an area centered about its optical axis, encompassing its optical zone. In one embodiment, a rotating arm, rotating in a plane perpendicular to the optical axis of the cornea, transmits the laser beam to the variable deflector.
Method and apparatus for modification of corneal refractive properties
A method and apparatus for modifying corneal refractive properties includes a laser source and an ring-like deflector positioned about the cornea. The ring-like deflector is contoured and positioned about the cornea. The contour of the deflector is selected to affect the desired post-operative corneal curvature. A beam emitted from the laser source is deflected in a (predictable) controlled manner by the ring-like deflector at any desired point such that the beam strikes the cornea tangentially, ablating or lathing the contacted corneal surface. A masking device or an axicon can be provided in cooperation with a wide-body laser beam to deliver a ring of laser light to the deflector causing the light to strike the cornea tangentially in a ring-like pattern substantially centered about the visual axis. Alternatively, in a narrow-beam embodiment, the beam may be translated in the radial direction and revolved about the visual axis or rotated off parallel to the visual axis causing the beam to be deflected off of the ring-like deflector for striking the cornea tangentially over 360.
Analgesic compositions from sweet peppers and methods of use thereof
This invention relates to analgesic compositions obtained from the fruit of the Capsicum genus, in particular Capsicum annuum and more particularly to purees or extracts of sweet peppers. This invention further relates to therapeutic uses of such analgesic compositions.
Analgesic compositions from sweet bell peppers and methods of use thereof
This invention relates to analgesic compositions obtained from extracts of sweet bell pepper purees or filtrates thereof and to therapeutic uses of such analgesic compositions.
Analgesic and anti-inflammatory compositions and methods with flavonoid glycoside-type compounds
The present invention relates to pharmaceutical compositions containing certain flavonoid glycoside-type compounds that have been shown in the present invention to be therapeutically useful, including useful as analgesics and anti-inflammatories for the treatment and management of pain and inflammatory conditions. Methods for the therapeutic uses of such compounds and pharmaceutical compositions is also provided.