Surgery – Miscellaneous – Methods
Reexamination Certificate
1999-10-26
2002-04-09
McDermott, Corrine (Department: 3738)
Surgery
Miscellaneous
Methods
Reexamination Certificate
active
06367480
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to therapeutic methods, compositions, and uses, more particularly to methods, compositions and uses associated with the eye, such as cataract treatment.
BACKGROUND OF THE INVENTION
Cataract is an exceptionally common condition affecting people of all racial groups. Cataract causes loss of visual capacity. Essentially, a cataract is an opacity of the crystalline lens, a key component of the eye's focusing system. The extent of opacity within the crysalline lens can vary, affecting the whole lens or only part thereof. The opaque region can prevent or retard the transmission of light through to the retina. Apart from affecting the capacity to visualize objects, cataracts may also scatter light, such that discomfort from sunlight and bright lights may result i.e. glare. Cataracts also affect animals, including animals such as dogs and cats.
Cataract most commonly occurs with increasing age but may occur as a congenital or genetic anomaly or in association with various diseases or certain medications. It is frequently the most common cause of decreased vision (not correctable with glasses) yet is one of the most successfully treated conditions by surgery.
The standard treatment for cataracts, is removal of the lens substance, and replacement of the cataractous human lens with an intraocular lens. Intraocular lenses are inserted into the eye in place of the removed cataractous lens, thereby improving and frequently retaining vision to normal levels.
Techniques for cataract treatment have been advanced by phacoemulsification surgery, this involving a very small corneo-limbal incision, to gain access to the lens capsule, creating an incision in the lens capsule to access the lens substance (cortex and nucleus) and removal of the lens by high frequency ultrasound and suction with irrigation. The capsule (the basement membrane which surrounds the crystalline lens) and its attachment, the zonular apparatus which suspends the lens from the ciliary body, are left largely intact, except for the anterior capsulotomy, that is the incision in the capsule through which the cataractous lens is removed and its replacement inserted. Preservation of this inert ocular structure (i.e. capsule and zonular apparatus) supplies a mechanism by which intraocular lenses can be implanted so that they do not impinge on vital structures (as occurs with angle or iris supported intraocular lenses) and thus avoids chronic complications such as uveitis, glaucoma and corneal decompensation.
During phacoemulsification surgery the anterior crystalline lens capsule is torn away to form a circular opening by which the lens material can be removed (continuous curvilinear capsulorhexis). This produces a strong capsular rim that resists tearing even when stretched—generally improving the safety margin during surgery. In extracapsular surgery, a so-called can-opener capsulotomy is performed, but the irregular edges of the capsule are prone to radial capsular extension tears which can result in loss of vitreous or the lens into the vitreous, both adverse events which frequently result in a suboptimal result and complications. Furthermore, following intraocular lens insertion, lens capsular fibrosis can cause decentration of the intraocular lens (with resultant astigmatism and lens-edge induced glare) but this occurs less frequently following capsulorhexis because the forces generated within the capsular bag are more symmetrical. Thus capsulorhexis is a critical step in achieving a good surgical result.
Visualization of the capsule, particularly the anterior lens capsule, is critical in capsulorhexis procedures. Capsulorhexis is generally performed in the presence of the red reflex, where light reflecting off the retina highlights the anterior capsule against a reddened background. Capsulorhexis is difficult in patients with dense cataracts (mature, usually white or very dense cataracts) where the red reflex is difficult to see, or simply not present. In these cases, elective extracapsular surgery is usually performed with its inherent inadequacies and difficulties. Capsulorhexis may also be difficult to perform in presence of corneal opacities (such as scars) or vitreous opacity, such as vitreous hemorrhage (for examples sometimes seen in patients with diabetes).
Various approaches have been tried to improve the success rate of performing capsulorhexis in patients with dense cataracts, or in conditions where the anterior lens capsule cannot be visualized for whatever reason. These include:
1. Using high magnification, dimming the operating theatre lights and using side illumination via a fibre-optic light source to enhance the view of the capsule. These procedures are clumsy, costly, and not particularly effective.
2. Using dyes, particularly fluorescein to stain the capsule and allow it to be highlighted against the unstrained underlying opaque lens fibres. Such dyes are difficult to use in the eye, they diffuse rapidly into the lens and cornea and require fitting of the operating microscope with appropriate filters to optimize visualization. Possible toxic effects of dyes also arise.
3. Haemocolouration of the capsule with the patients own blood.
4. Development of specialized cutting techniques, such as radiofrequency cutting devices, which require expensive additional instrumentation and have been shown to produce circular holes in the anterior lens capsule of inferior strength to the standard capsulorhexis.
None of these techniques have found widespread use.
There remains a distinct mean for methods, compositions and uses which enable ready visualization of the anterior lens capsule, so that capsulorhexis can be carried out so as to allow cataract removal and replacement with an intraocular lens in a safe, efficient, and cost-effective manner.
SUMMARY OF INVENTION
This invention is concerned with methods, compositions and uses for the visualization of the anterior lens capsule during cataract removal and lens replacement procedures. The invention is based on the surprising finding that the vital dye trypan blue can be readily used to stain the anterior lens capsule free of disadvantages associated with other dyes.
In accordance with a first aspect of this invention there is provided use of trypan blue in the manufacture of a compositions for the visualization of the anterior lens capsule of the eye during removal of cataractous lenses and lens replacement procedure.
In accordance with another aspect of the invention there is provided a method for visualising the anterior lens capsule of a human subject which comprises instilling into the anterior chamber of the eye a trypan blue solution of trypan blue dissolved in an ocularly compatible vehicle.
In accordance with a further aspect of this invention there is provided a method for the visualization of the anterior lens capsule which comprises introducing trypan blue into the anterior chamber of the eye following the addition of a viscoelastic substances into the anterior chamber of the eye to confine the trypan blue to the anterior capsular area.
In accordance with a further aspect of this invention there is provided a method for the visualization of the anterior lens capsule during the capsulorhexis procedure, which comprises filling the anterior chamber of the eye with viscoelastic substances of different viscosities, introducing a trypan blue solution comprising about 0.05% to 3% w/w trypan blue solution below the viscoelastic substances for a time sufficient to stain the anterior lens capsule, removing from the anterior chamber of the eye the excess trypan blue and viscoelastic substances, re-introducing fresh viscoelastic substances into the anterior chamber of the eye, and thereafter carrying out capsulorhexis, lens removal and replacement with an intraocular lens.
In a still further aspect this invention relates to a method for cataract treatment which comprises filling the anterior chamber of the eye with viscoelastic substances, introducing a trypan blue solution comprising about 0.05% to about 3% w/w tr
Barrett Thomas
Foley & Lardner
McDermott Corrine
LandOfFree
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