Surgery – Means for introducing or removing material from body for... – Material introduced into and removed from body through...
Reexamination Certificate
1999-07-15
2001-04-03
Kennedy, Sharon (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Material introduced into and removed from body through...
C604S521000, C604S294000
Reexamination Certificate
active
06210357
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed generally to medical procedures and, more particularly to a medical procedure for removal of the innermost layer of the human retina (internal limiting membrane) from the underlying neural retina at the center of vision (macula).
2. Background Art
The rays of light entering the eye (
FIG. 1
) and bearing the pattern of the object being looked upon pass through the cornea
32
, the aqueous humor, the pupil, the lens
34
, and the vitreous humor, then fall upon the retina
26
. The retina is the light sensitive film lining the back two-thirds of the eye. Its appearance is similar to that of wet tissue paper. Its layers consist of the internal limiting membrane (ILM), the neurosensory retina, and the retinal pigment epithelium; the ILM, being innermost, is the retinal border with the vitreous gel cavity
42
. If the parts of the eye are normal and the lens is properly adjusted, the image will be focused upon the retina. This condition results in clear vision. At the back of the eye or, more specifically, the back part of the retina is the macula lutea
36
having at its center the fovea centralis. The macula is a small orange-yellow, oval area (about 3 mm by 5 mm) of the retina adjacent to the optic nerve
38
. Vision in which the image of the object looked upon falls upon the macula is the sharpest vision and is called macular vision or central vision, as opposed to gross, peripheral vision.
A wrinkling of the internal limiting membrane and the neural retina is called macular pucker. This can cause loss of fine vision to the level of legal blindness. The wrinkling is caused by contractile cells or fibrocellular membranes (epimacular proliferation or EMP) and is usually a process associated with aging.
Macular distortion and macular edema, with resultant macular dysfunction, are recognized sequelae of EMP. Often, the macula will have a “wrinkled cellophane” appearance. According to one theory, this appearance represents internal limiting membrane (ILM) distortion by surface proliferative cells without a distinct epimacular proliferative membrane overlying the ILM, which might be surgically removed. This ILM cellophaning may persist or occur months after seemingly successful removal of EMP, limiting visual recovery.
Specimens analyzed after vitrectomy (the surgical removal of a portion of the vitreous body and/or associated epiretinal or fibrous membranes) using a microscope for epimacular membrane removal often contain retinal ILM fragments that have been intentionally or unintentionally removed to treat “traction maculopathy,” a term introduced by Morris, R., Kuhn, F., Witherspoon, C. D., (“Retinal folds and hemorrhagic macular cysts in Terson's syndrome,”
Ophthalmology
(1994) 101:1). Written reports differ on whether the presence of ILM fragments correlate with the visual outcome. (Trese, M. et al., “Macular pucker Ultrastructure,”
Graefe's Arch Clin Exp Ophihamol.
(1983) 221:16-26; De Bustros, S. et al., “Vitrectomy for Macular Pucker: Use after treatment of retinal tears or retinal detachment,”
Arch Ophthalmol.
(1988) 106:758-760; Sivalingam, A. et al., “Visual prognosis correlated with the presence of internal limiting membrane in histophathologic specimens obtained from epiretinal membrane surgery,”
Ophthalmology.
(1990) 97:1549-1552). More recently, William Hutton and others have implicated even relatively small amounts of traction as exacerbating diabetic macular edema.
Additionally, Logan Brooks and Tom Rice have advocated the intentional removal of the macular ILM in macular hole surgery. (Brooks, L., “ILM peeling in full thickness macular hole surgery,”
Vitreoretinal Surgery and Technology.
(1995) 7:2; Rice, T. A., “Technique of removal of the inner retinal surface in macular hole surgery,”
Retina Society
28
th
Annual Meeting. Santa Fe, N. Mex.,
1995). A macular hole is thought to occur as a result of tangential traction on the retina at the macula, usually leading to legal blindness
Thus, there are many advocates of the importance of ILM removal in macular hole surgery. Previous methods as shown in
FIG.2
, developed over a period of about twenty years, have removed the macular ILM
54
and EMP
50
utilizing the manual, mechanical method with grasping forceps
52
. This forceps procedure is the most delicate surgical maneuver performed on the human body. The procedure requires ideal surgical conditions and expert skill. Ideally, cataracts and any other opacity obscuring surgical view will have been eliminated for safe and predictable EMP/ILM removal. Electron microscopy of surgical specimens frequently demonstrates cellular proliferation contracting the ILM. It is believed that the increased mobility of an ILM denuded macula contributes to successful hole closure.
Furthermore, the results with ILM maculorhexis in macular hole surgery were encouraging. In a consecutive series of 32 idiopathic holes with less than two years duration, a 97% closure was achieved. Previous macular hole edges were rarely discernible. Visual acuity improved at least two Snellen lines in 91% of eyes, and 41% of eyes achieved 20/40 or better visual acuity at the last follow-up (Morris, R., Witherspoon, C. D., “Internal Limiting Membrane Maculorhexis for Traction Maculopathy,”
Vitreorelinal Surgery and Technology
(1997) 8(4):1).
All of the above-described conditions may be considered forms of traction maculopathy as first described by Morris et al. The ultimate goal of all surgery to cure traction maculopathy is to return the neural retina to its normally smooth contour, allowing resumption of fine vision and relief from distorted vision.
In a very rare disease called Terson's syndrome, blood under pressure from a ruptured vein or capillary spontaneously lifts the ILM, resulting in what is called a hemorrhagic macular cyst (HMC) (Morris, R., Kuhn, F., Witherspoon, C. D., American Academy of Opthalmology, 1990). The hemorrhage usually then breaks through the ILM into the vitreous. Vitreous and subinternal limiting membrane hemorrhage occurs as a result of abrupt intracranial hemorrhage from an aneurysm or closed head trauma. Although the exact mechanism for these hemorrhages is unknown, it is thought that the sudden increased intracranial pressure is transmitted via the optic nerve to retinal venules and capillaries, rupturing them. If bleeding has occurred at the macula, it will appear as a circular or boat shaped cyst (HMC) on the surface of the retina. The HMC is usually encircling the macula. Its diameter and height vary, as does its color, depending on the longevity of the hemorrhage. Early intervention (i.e., for amblyopia prevention in infants) finds a reddish cyst. A few months after the incident, the surgeon encounters a yellow lesion (degenerated blood products), a clear membrane spanning an optically empty cavity, or a collapsed membrane. A perimacular fold may form along the edge of the separation of the ILM from the neurosensory retina at the cyst margin.
Sub ILM hemorrhagic macular cysts are almost pathognomic to Terson's syndrome. Fourteen cases of retinal folds from shaken baby syndrome or consequent to direct head trauma were analyzed from various literature reports, each had intracranial hemorrhage and various forms of intraocular hemorrhage, including HMC. The HMC's occur not only in traumatically induced cases of Terson's syndrome but also in patients with spontaneous subarachnoid hemorrhage. Accordingly, it has been proposed that intracranial hemorrhage, from whatever source, is the common denominator in the formation of both HMC's and their accompanying perimacular folds.
In the series originally presented at the Annual Meeting of the American Academy of Ophthalmology in 1990, it was found that of 25 eyes undergoing vitrectomy for Terson's syndrome, 8 (32%) demonstrated HMC's (Morris, R., Kuhn, F., Witherspoon, C. D., “Hemorrhagic Macular Cysts in Terson's Syndrome and its Implications for Macular Surgery,”
Developments
Kennedy Sharon
Lyon & Lyon LLP
Thompson Michael M
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