Surgery – Instruments – Light application
Reexamination Certificate
2002-03-12
2004-06-01
Peffley, Michael (Department: 3739)
Surgery
Instruments
Light application
C128S898000, C606S010000
Reexamination Certificate
active
06743221
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to systems for and methods of treating biological tissue and vascular biological tissue. More specifically, this invention relates to systems for and methods of treating biological tissues and vascular tissues with laser radiation that are within an enclosed space or within a cavity of the body, such as vascular ophthalmic tissues.
BACKGROUND OF THE INVENTION
Proliferative diabetic retinopathy (PDR) and proliferative vitreoretinopathy (PVR) are the most common causes of permanent or severe visual loss associated with retinal detachment. At the core of visual loss in both of these diseases is the growth of fibrous and/or fibro-vascular membranes, referred to generally herein as FVMs. The FVMs grow or develop on or near the surface of the retina. The growth of FVMs causes tractional retinal detachments, combined tractional-rhegmatogenous retinal detachments, and vitreous hemorrhages. Prior to the development of vitrectomy, severe cases of proliferative vitreoretinopathy that underwent conventional scleral buckle failed to reattach the retina in up to 70% of cases (Yoshida et al., 1984; Grizzard and Hilton, 1982). With the advent of photocoagulation and vitrectomy, great progress has been made over the past 30 years in treatment and management of proliferative diabetic and vitreoretinopathy. Success of reattaching retinal tissue with patients having severe PVR has been reported between 36 and 80% overall (Machemer and Lagua, 1978; Aaberg 1988; Hanneken and Michels, 1988; Fishe et al., 1988; The Silicon Oil Study Group, 1992). Success rates were decreased when eyes had already failed vitrectomy or when anterior membranes were present (Lewis and Aaberg, 1991). In diabetics the prognosis is even worse. When eyes with vitreous hemorrhage and preoperatively attached maculas undergo vitrectomy to remove blood 5 to 17% of eyes are reported to lose light perception and only 40-62% regained visual acuity of 20/200 or better (DRVS 1985 and 1990; Machemer and Blankenship, 1981; Michels et al., 1983; Thompson et al., 1987; Rice et al., 1983). In eyes with traction retinal detachment of the macula 20/200 vision was regained in 21 to 58% and loss of light perception occurred in 11 to 19% (Aaberg 1978; Aaberg and Van Horn, 1978; Hutton et al., 1980; Rice et al., 1983). When retinal detachment was both rhegmatogenous and tractional only 25 to 36% regained 20/200 or better vision and loss of light perception ranged from 9 to 23%.
In order to repair retinal detachments caused by PDR and PVR the surgeon must relieve traction and close all breaks. Some residual traction outside the macula is acceptable provided that it does not prevent the surgeon from closing a break. During vitreoretinal surgery, FVMs are removed from the surface of the retina by careful mechanical dissection. The surgeon has several tools at his or her disposal to aid in the removal of fibrovascular tissue from the retina. These tools include various scissors, knives, picks, forceps and other cutting devices (e.g. vitrector). This process is tedious, time consuming and very labor-intensive. Further, mechanical dissection exerts traction on the retina and can lead to complications like hemorrhage, resulting in the formation of a retinal hole, failure to remove enough of the FVM tissue or failure to close a retinal break.
Many of these complications are a direct result of the mechanical nature of the dissection of FVMs. For example cutting FVMs with scissors often results in bleeding which reduces visibility and results in clot formation. The clots can adhere to the surface of the retina and FVMs and cause traction or reduce visibility. To control bleeding requires that the surgeon elevate the intraocular pressure and slowly lower it back to normal while waiting for the bleeding to stop. The surgeon must usually change instruments to clear the hemorrhage before resuming the operation. Also, a retinal break sometimes forms when adherent FVMs are removed from the delicate retinal surface. When this happens all traction near the break must be relieved, the break must be marked and treated with a laser once the retina is reattached. These complications can occur numerous times during the course of a single surgery adding to the time required to complete the procedure. Increased surgical time results in increased fatigue, increased risk of surgical error, increased risk of surgical failure, increased need for re-operation, increased likelihood of severe vision loss, and increased cost to the healthcare system and society. Further, there is an increased risk to the patient from the prolonged exposures to general anesthesia.
Many types of lasers have been tried in the search for more effective means of removing membranes from the surface of the retina including Excimer (ArF), Carbon Dioxide CO
2
, Holmium:YAG, Erbium:YAG, and other infrared lasers (Hemo et al., 1997; Lewis et al., 1992; Palanker et al., 1994; Tsubota 1990; Peyman and Katoh, 1987; D'Amico et al., 1994; Bende et al., 1989; Walsh et al., 1989; Cummings and Walsh 1993 Karlin et al., 1986; Bridges et al., 1983; Meyers et al., 1983; Miller et al., 1980; Borirakchanyavat et al., 1991;). However, to date laser systems and methods have not been discovered which are suitable for routine laser assisted vitreoretinal surgery.
The Excimer laser, or argon fluoride laser, with a wavelength of 193 nm has been evaluated for vitreoretinal surgery in both air and fluid filled eyes (Hemo et al., 1997; Lewis et al., 1992; Palanker et al., 1994). The Excimer laser is capable of extremely precise ablation of retinal tissue with apparently few complications. However, difficulties with size, cost, maintenance, delivery systems and possible mutagenicity of ultra violet wavelengths have hampered development of Excimer and other similar lasers for vitreoretinal surgery (Pellin et al., 1985; Marshall and Sliney, 1986).
Because of the numerous shortcomings of the currently available laser systems and methods, what is needed is a laser system and method which allows vitreoretinal surgeons to cut and cauterize FVMs while reducing traction on the retina and also removing adherent FVMs by ablation.
SUMMARY
The instant invention is directed to a system for and method of treating a target area of biological tissue with laser radiation. Preferably, the biological tissue is ophthalmic tissue having one or more FVMs on or under the retinal surface of a human eye. Preferably, the FVM is categorized prior to treating the ophthalmic tissue with the laser radiation, wherein separations between underlying retinal tissue and the FVMs, the thickness of FVMs, and the nature of the attachments of FVMs, are determined or characterized prior to laser treatment. The laser assisted vitreoretinal surgery is then tailored to minimize the potential for damage to healthy ocular tissue surrounding the membranes. Variables that can be adjusted in order to tailor the laser assisted vitreoretinal surgery, include but are not limited to the laser sequence (burst and/or pulse sequence), the laser power, the endo-probe configuration(s) used and/or the presentation angles selected to treat and/or dissect the membranes.
In a preferred method of the instant invention, the separations of the FVM(s) from the underlying retinal tissue can be optically measured using a microscope and the laser power can be adjusted to have an effective penetration depth that is less than or equal to the separation of the FVM(s) from the underlying retinal tissue. The effective penetration depth of a laser pulse sequence and optical configuration used can be estimated by measuring the penetration depth of the laser radiation in saline solution or other material having similar absorption properties to the ophthalmic tissue to be treated. During the laser treatment of the ophthalmic tissue, the laser penetration depth can be controlled by adjusting the approach angle, the distance between emitted laser light, the laser pulse sequence and/or power. Further, the endo-probes used to deliver the laser radi
Allen Peter Nigel
Hobart James L.
Joseph Daniel Paul
Negus Daniel K.
Haverstock & Owens LLP
Peffley Michael
LandOfFree
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