Patent Application
20080027519
The present invention makes use of laser photoablation, photodisruption, photocoagulation, or a combination thereof, in order to decompress an ocular compartment syndrome. In the case of a central retinal vein occlusion, laser energy is directed at the site of vascular compression, usually at the level of the lamina cribrosa. In the case of branch retinal vein occlusions, laser energy is delivered to the fascial sheath which binds the retinal vein to its companion artery so as to decompress the site of venous compression. In the case of non-arteritic anterior ischemic optic neuropathy (NAAION) or papilledema, the laser energy is directed at the optic nerve and/or nerve sheath in much the same way a surgical blade would be directed at the nerve in order to perform a traditional surgical radial neurotomy.
The advantageous qualities of photoablation make the process desirable for the controlled decompression of the lamina cribrosa in the area of an occluded central retinal vein. Likewise, for branch retinal vein occlusions in which a retinal vein is compressed by an adjoining artery as they pass through their common fascial sheath, laser photoablation can be used to ablate the fascial layer thereby releasing the compressive forces on the involved retinal vein.
Published research has suggested that surgical delamination of the internal limiting membrane (ILM) in the area of a BRVO at the same time as decompression of the fascial sheath may improve final visual outcome. To this end, laser photoablation could also be used to locally ablate the ILM in the area of a BRVO without the need for intraocular surgery. For the treatment of NAAION or papilledema, photoablation can be used to create a precise incision in the optic nerve with far greater control and far less risk to adjacent structures than a radial neurotomy performed with a hand-held surgical knife blade. By creating the smallest possible incision required to produce a therapeutic effect, radial neurotomy performed with a laser will cause less loss of nerve fibers than radial neurotomy performed with a blade.
Tissue ablation with a photodisruptive laser such as a femtosecond infrared device is well suited for the controlled decompression of the lamina cribrosa in the area of an occluded central retinal vein. Likewise, for branch retinal vein occlusions, laser photodisruption can be used to ablate the fascial sheath and/or Internal Limiting Membrane that is compressing a retinal vein. Published research has suggested that surgical delamination of the internal limiting membrane (ILM) in the area of a BRVO at the same time as decompression of the fascial sheath may improve final visual outcome. To this end, laser photodisruption could be used to locally ablate the ILM in the area of a BRVO without the need for intraocular surgery.
For the treatment of NAAION or papilledema, photodisruption can be used to create a precise incision in the optic nerve (neurotomy) with far greater control and far less risk to adjacent structures than a radial neurotomy performed with a handheld surgical knife blade. By creating the smallest possible incision required to produce a therapeutic effect, a neurotomy performed with a laser results in less loss of nerve fibers than radial neurotomy performed with a blade.
Although laser photocoagulation offers far less control over tissue removal than laser photoablation or photodisruption, it can be used to decompress a central or branch retinal venous occlusion either alone or in conjunction with a photoablative and/or photodisruptive laser. In this regard, laser photocoagulation would be most useful in arresting any bleeding caused by the use of a photoablative or photodisruptive laser in the treatment of ocular compartment syndromes. Since laser photocoagulation generally causes tissue shrinkage, a photocoagulative laser can also be used to place a tissue under tension prior to treatment with a photodisruptive and/or photoablative laser.
Referring now to
The laser 108 can be selected to include any suitable laser for causing a photoablative and/or a photodisruptive effect. In the preferred embodiment of the invention, laser 108 can be selected to be a photoablative laser including a Nd:YAG laser radiating in the infrared range (1064 nm) with a pulse duration measured in nanoseconds to tens of nanoseconds. In an alternate embodiment of the invention, the laser 108 can be selected to be a photoablative laser including a Nd:YAG laser radiating in the infrared range (1064 nm) with a pulse duration measured in femtoseconds to hundreds of femtoseconds. Those skilled in the art will appreciate that the Nd:YAG laser can be photodisruptive when used at a nanosecond durations with a wavelength of 1064 nm. When the same 1064 nm Nd:YAG laser is used at femtosecond durations, it can produce effects which are on the border between the effects produced by the photodisruptive and photoablative lasers. Still, it should be understood that the method disclosed herein is not limited to the particular types of lasers and/or pulse durations described herein. Instead, any type of laser can be used that is capable of causing a desired photoablative, photodisruptive and/or photocoagulative effect.
The energy level selected for use with the laser 108 used with the present invention will vary greatly based on the type of laser used and the tissue being targeted. Incising the optic nerve head, for example, would be expected to require laser energy on an order of magnitude higher than the laser energy required for incising the ILM (internal limiting membrane). The clarity of the patient's ocular media will also affect the laser energy needed to complete a procedure. For example, incising the optic nerve head in a patient with a dense cataract will take far more laser energy than incising the optic nerve head in a patient with a clear/non-cataractous lens. In general, a photocoagulative laser such as a green diode laser would be expected to utilize spot sizes between 25 and 500 microns. The duration of the laser treatments selected would vary between milliseconds bursts and a continuous wave. The power level selected for the laser treatments would be in the 50 milliwatt to 1 watt range. For a traditional nanosecond(s) duration photodisruptive Nd:YAG laser, energy delivery would vary between millijoules and hundreds of millijoules per pulse. For a photodisruptive femtosecond(s) duration Nd:YAG laser, energy fluence would vary between tens of joules per square centimeter and thousands of joules per square centimeter.
The operative site, including the patient's operative eye 102, can be visualized by the surgeon by selecting a safety-shielded optical or videographic electronic display 112. Still, the selection of the display for viewing the operative site is not limited in this regard. The control of the microscope (zoom, focus, X-Y, tilt, brightness, etc.) and laser (focal point, power, spot size, spot shape, spot pattern, etc.) are performed from microscope and laser controls 114 using established control techniques.
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The method of treatment 400 begins with step 402 and continues with step 404. In step 404, the patient is positioned beneath an operative microscope 110 and one or more of lasers 108, 109, and 111. In step 406, the operative eye 102 is stabilized by selecting and positioning a fixation ring 104 or other fixation device on the operative eye 102. In step 408, microscopic visualization is used to identify the patient's central retinal vein as it passes through the optic nerve. In step 410, laser energy is directed at the tissues which are compressing the central retinal vein. This step involves selecting one or more of lasers 108, 109, and 111 depending upon the effect desired. A single photocoagulative, photodisruptive, or photoablative laser may be selected. However, in the preferred embodiment of the invention, a combination of one or more laser types is selected in order to achieve the desired effect. For example, a photocoagulative laser such as a diode laser (400-800 nanometer range) may be selected to cause contraction of the lamina cribrosa thereby thinning it and putting it under tension. This tension facilitates incision of the lamina cribrosa by selecting and utilizing a photodisruptive laser (such as a nanosecond, 1064 nm Nd:YAG laser) or by selecting and using a photoablative laser (such as a femtosecond Nd:YAG). A photocoagulative laser may also be selected and used following decompression of the CRVO to stop any bleeding caused by the treatment.
If the patient has a large optic cup, incision of the lamina cribrosa may be all that is necessary to decompress the compartment compressing the central retinal vein. If the patient has a small optic cup, incision of a portion of the substance of the patient's optic nerve may be necessary in addition to incision of the lamina cribrosa. Although it may be possible to incise said tissues with a single high-power application of laser energy, multiple passes using lower energies are preferred. By selecting the least possible amount of laser energy to accomplish decompression, collateral damage to surrounding structures such as the central retinal artery and vein are minimized. When incision of the optic nerve head is necessary, multiple low-energy laser application will help minimize visual field loss from optic nerve damage. When practical, the nerve head is incised at the nasal midline in order to minimize visual field loss and avoid damage to macular nerve fibers.
The method ends with step 412.
Referring now to
In step 504, the patient is positioned beneath an operative microscope 110 and one or more of lasers 108, 109, and 111. In step 506, the operative eye 102 is stabilized by selecting and positioning a fixation ring 104 or other fixation device on the operative eye 102. In step 508, the site of the branch retinal vein occlusion (generally an arteriovenous crossing) is identified using microscopic visualization. In step 510, laser energy is used to open the fascial sheath which binds the artery to the vein at the site of the branch retinal vein occlusion identified in step 508. In this step, a single photocoagulative, photodisruptive, or photoablative laser may be selected and used for this purpose. However, in the preferred embodiment of the invention, a combination of one or more laser types is selected in order to achieve the desired effect.
For example, a photocoagulative laser such as a diode laser (400-800 nanometer range) may be selected and used to cause contraction of the internal limiting membrane (ILM) that makes up the arterio-venous fascial sheath, thereby thinning it and placing it under tension. This tension facilitates incision of the sheath with a photodisruptive laser. A photodisruptive laser that can be selected includes a nanosecond, 1064 nm Nd:YAG laser. In other embodiments of the invention, a photoablative laser could be selected such as a femtosecond, 1064 nm Nd:YAG laser. This type of Nd:YAG laser ablates the fascial sheath and/or Internal Limiting Membrane (ILM) surrounding the area of retinal venous constriction, thus, restoring venous blood flow without disrupting the full thickness of the underlying retinal vessels and surrounding structures. A photocoagulative laser can also be selected and used following decompression of the BRVO to stop any bleeding caused by the treatment. Although it may be possible to decompress the branch retinal vein with a single high-power application of laser energy, multiple passes using lower energies are preferred. By selecting and using the least possible amount of laser energy to accomplish decompression, collateral damage to the affected vein, the adjacent artery, and the surrounding artery are minimized.
The method ends with step 512.
Referring now to
In step 610, laser energy is directed at a thin radial strip of the substance of the optic nerve in order to incise the nerve in much the same way a steel blade is used to perform a traditional radial optic neurotomy. Whenever practical, the nerve head is incised at the nasal midline in order to minimize visual field loss and avoid damage to macular nerve fibers. Alternatively, the neurotomy can be performed in an area that already shows evidence of ischemia, so as to minimize visual field loss. A single photocoagulative, photodisruptive, or photoablative laser may be used for this purpose. In the preferred embodiment of the invention, a combination of one or more laser types is selected in order to achieve the desired effect.
For example, a photocoagulative laser such as a diode laser (400-800 nanometer range) may be selected and used to cause contraction of the target tissue thereby thinning it and putting it under tension. This tension facilitates incision of the tissue with a photodisruptive laser (such as a nanosecond, 1064 nanometer Nd:YAG laser) that can be selected and/or a photoablative laser (such as a femtosecond, 1064 nm Nd:YAG) that can also be selected. A photocoagulative laser may also be selected and used following decompression of the NAAION to stop any bleeding caused by the treatment. Although it may be possible to incise said tissues with a single high-power application of laser energy, multiple passes using lower energies are preferred. By selecting the least possible amount of laser energy to accomplish decompression, visual field loss due to optic nerve damage is minimized.
The method ends with step 612.
Papilledema is another ocular compartment syndrome which is amenable to treatment with the proposed method and apparatus. Unlike the previously described ocular compartment syndromes, in papilledema, the source of compressive force comes from elevated cerebrospinal fluid (CSF) pressure. This force compresses the optic nerve and results in impaired blood flow to the nerve as well as axoplasmic stasis. Lowering of intracranial pressure can be achieved through traditional means such as a ventriculoperitoneal shunt. Because ventricular shunting requires brain surgery, however, a less invasive treatment would be desirable and highly preferable. Incision of the optic nerve sheath through a medial or lateral orbitotomy can also be used to decompress this compartment syndrome although this also requires significant surgical trauma.
Referring now to
For example, a photocoagulative laser such as a diode laser (400-800 nanometer range) may be selected and used to cause contraction of the optic nerve rim thereby thinning it and putting it under tension. This tension facilitates incision of the nerve rim with a photodisruptive laser such as a nanosecond, 1064 nm Nd:YAG laser. In other embodiments of the invention, a photoablative laser may be selected, such as a femtosecond 1064 nm Nd:YAG laser to create photoablative effects. The photocoagulative laser may also be used to control any bleeding caused by the treatment. Although it may be possible to incise said tissue with a single high-power application of laser energy, multiple passes using lower energies are preferred. By using the least possible amount of laser energy to accomplish decompression, damage to the optic nerve is minimized. When practical, the nerve head is incised at the nasal midline in order to minimize visual field loss and avoid damage to macular nerve fibers.
The method ends with step 712.
All of the apparatus, methods and compositions disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the invention has been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the apparatus, methods and sequence of steps of the method without departing from the concept, spirit and scope of the invention. More specifically, it will be apparent that certain components may be added to, combined with, or substituted for the components described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims. Accordingly, the exclusive rights sought to be patented are as described in the claims below.
