Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Reexamination Certificate
1999-10-18
2001-01-30
Manuel, George (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
Reexamination Certificate
active
06179421
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to method and apparatus for examination of ocular microcirculation and subsequent treatment to prevent, ameliorate or inhibit worsening of disease associated with abnormalities of choroidal and/or subretinal microcirculation. In particular, the invention relates to method and apparatus for diagnosis and treatment of ocular neovascularization.
2. Related Art
A pathology of current interest is age-related macular degeneration, symptoms of which include the growth of fibrovascular membranes and new blood vessels around, and from the choroid below, the macula. The prognosis is progression to eventual blindness in the aged population with this illness. The choroid is the layer below the Bruch's membrane and the retinal pigment epithelium. The neovascularization typical of this disease arises from the capillary network (called the choriocapillaris) which, for our intents and purposes, may be considered as flat in the microscopic field of view or region of interest. Diabetic retinopathy is another disease associated with neovascularization in the retina.
The progression of these diseases includes the growth of new blood vessels in the choroid and the retina. This neovascularization can occur in different layers in the fundus and may lead to blindness. These new, microscopic vessels are fragile. They may push upwards, off the plane of the normally flat choroidal capillary networks, into or against the retina (in which the light-sensing ganglion cells reside) or the Bruch's membrane or the retinal pigment epithelium, resulting in bleeding, and/or retinal detachment which may lead to blindness.
Current techniques for examining such diseases include fluorescein angiography (SF) and indocyanine green angiography (ICG). These techniques do not resolve the microscopic details which permit the earliest possible detection of the existence and the exact locations of these new vessels. The ophthalmologist requires angiographs, then time to study them, deciding on suspect areas, whether to recall the patient for confirmatory angiographs or for treatment. Also, even if visible damage is noted, separate techniques (eg laser photocoagulation) using different instruments, must then be employed for later treatment. There is therefore a delay from examination to treatment, causing inconvenience to the patient in the multiple visits required. The additional costs in the different instruments and the manpower for handling these different instruments as well as the multiple visits are disadvantages.
There are several different techniques for locating neovascularization. Some of them are still experimental or undergoing clinical trials, (eg Optical Coherence Tomography—OCT). The existing commercial devices do not provide high-resolution and/or high-magnification images. Some simply take electronic pictures of the entire fundus (at low magnification), using false colour and other image-processing means to enhance the low resolution images.
The current treatment techniques for the removal of neovascularization employ imprecise local areal destruction (usually using a laser beam) after damage becomes visible; damage is significant if it is visible even in low-magnification, low-resolution angiographs. The laser destroys the suspect neovascularization by destroying and coagulating the area surrounding the suspect neovascularization location. Other means, some still experimental, of terminating neovascularization involve invasive methods like optic fibre insertion into the vitreous chamber.
U.S. Pat. No. 4,838,679 describes an apparatus for and a method of examining the front parts of human eyes. The apparatus is specifically designed for corneal examination using light reflected from a raster-scanning laser source. The apparatus is not suitable for fundus examination and does not describe treatment of neovascularization.
U.S. Pat. No. 4,213,678 describes an apparatus for examining the fundus. Again, this is achieved using reflected light and via scanning with a laser source of light. Resolution achieved with this apparatus is not sufficient for early diagnosis of neovascularization. There is reference to treatment of the fundus using a laser but no details are provided.
Currently, no known apparatus enables examination of those parts of the eye at the macula or in the layers below it with sufficient image quality for neovascularization to be detected before visible macula damage occurs, or enables examination of those parts of the eye at or around the fovea with sufficient data for detection of feeder vessels of a neovascular net.
Further, no apparatus is known that enables early diagnosis of macular degeneration and its treatment prior to significant loss of vision.
SUMMARY OF THE INVENTION
It is an object of this invention to provide method and apparatus to view, analyze, and treat certain diseases of the fundus of the eye. More specifically, an object of at least the preferred embodiments of the invention is to view, analyze and treat choroidal/subretinal and/or retinal neovascularization, especially as seen in age-related macular degeneration and diabetic retinopathy. An associated object is to provide method and apparatus for detailed observation of the microcirculation in the fundus of the eye. A further object is to provide method and apparatus for tracking the movement of individual blood cells and plasma in the retinal and optic disc microcirculation. A yet further object includes the provision of method and apparatus for examination of the microcirculation of the eye using two or more dyes.
Accordingly, a first aspect of the invention provides ophthalmologic examination apparatus comprising:
a light source;
illumination means for directing light from the source along an illumination path and into the fundus of an eye of a patient;
imaging means for directing fluorescence from the fundus of the patient along an imaging path to enable an image of the eye to be viewed;
wherein the illumination and imaging paths are arranged as a confocal microscope adapted to focus on the fundus of the eye.
In the present invention, the term “confocal” in relation to microscopy is used to indicate a confocal arrangement of illumination and imaging paths resulting in a shallower depth of focus and an enhanced contrast than are otherwise achievable using non-confocal arrangements. While from some technical points of view the illumination and imaging arrangements of some embodiments of the invention may properly be regarded as “partially confocal” or “of the confocal type”, the essential feature of the invention is that a shallow depth of field and an enhanced contrast are achieved based on the principles of one type of confocal microscope. Nipkow discs, if used in apparatus or method of the invention are used effectively as neutral-density filters.
The apparatus thus enables the fundus, the retina and the choroid, to be examined using a shallow depth of focus. This is an advantage as an operator can see an image of blood vessels within a relatively narrow layer of the fundus, typically within a depth of focus of about 50 &mgr;m and preferably 30 &mgr;m. As the total thickness of the fundus is several hundred microns, the apparatus enables fundal examination layer by layer. Disease associated with neovascularization that disrupts the layered structure of the fundus is more easily observed at an early stage—for example, bulges in the retinal pigment epithelium due to growth of a few new blood vessels below are more easily detectable than hitherto.
Nipkow discs comprising a plurality of apertures are used to achieve confocal arrangement of the illumination and imaging means, and are preferably mounted in operative combination with optics of the apparatus so that the planes of the respective apertures are coincidentally focused on the same layer in the fundus.
In an embodiment of the invention described below, the illumination and imaging paths each passes through a Nipkow disc adapted in use to rotate at high speeds. Preferably, the Nipk
Avimo Group Limited
Manuel George
Sterne Kessler Goldstein & Fox P.L.L.C.
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