Department of Ophthalmology and Visual Sciences Publications
12-1-1994
Overview and new technology in cyclodestructive procedures Jill Fishbaugh University of Iowa
Copyright © 1994 American Society of Ophthalmic Registered Nurses. Posted by permission. Fishbaugh J. Overview and new technology in cyclodestructive procedures. Insight: The Journal of the American Society of Ophthalmic Registered Nurses. December 1994;19(4):26-29 4p. Hosted by Iowa Research Online. For more information please contact:
[email protected].
Observations on Subspecialties Jill Fishbaugh, R.N., B.S.N., CRNO
Overview and new technology in cyclodestructive procedures When all medical and surgical measures have failed to lower intraocular pressure (IOP) in patients with severe and uncontrolled glaucoma, ophthalmologists must turn to cyclodestructive procedures to decrease aqueous production. Several months ago, the FDA (Food and Drug Administration) came through with an approval for a new technology in cyclophotocoagulation therapy. The IRIS Medical G-Probe™ used in conjunction with a semiconduc tor diode laser may be the superior alternative to previously available cyclodestructive techniques for which ophthalmol ogists have been searching. must go before cyclodestmctive procedures are iode laser technology has progressed I at a rapid pace since their first appear recommended, first it is interesting to investigate the definition, incidence, and treatment of glau ance about 10 years ago. Due to coma. Glaucoma is present when IOP is at a advancements in the telecommuni level that is intolerable for the normal function cations industry, companies like MCI® and ing of the optic nerve (Schuman & Puliafito, Sprint® have developed durable and reliable 1990). In the United States, glaucoma is one of lasers for their fiberoptic telephone lines which the leading causes of blindness for the adult in turn have led to cost effective and dependable population, age 40 and older. African-Americans diode lasers for other purposes. Medical applica are 4 to 5 times more likely to acquire glaucoma tions require a much higher power setting and than Caucasians. Prevent Blindness America cur in the last 5 years, diode lasers have become rently estimates there are between 2 to 3 million powerful enough for clinical functioning in the Americans with glaucoma. Half of those with ophthalmic setting. the disease are unaware they are afflicted. There Diode lasers are compact and portable, about are a staggering 89,000 to 120,000 Americans the size of a standard briefcase (Figure 1). They blind from glaucoma. are powered by ordinary electrical wall current. Medical and surgical treatments for glaucoma In the future, batteries may even power upcom simply aim at affecting the balance between ing models (Balles & Puliafito, 1990). They are aqueous production and aqueous outflow to highly efficient at converting electric energy to control IOP. Medical therapy used to lower IOP laser energy so little heat is produced. Therefore, by increasing aqueous outflow are cholinergics no special plumbing or water cooling system is (e.g. Pilocarpine, Carbachol, Phospholine necessary. In addition, to being highly reliable Iodide). Beta blockers (e.g. Timoptic, Betoptic, and relatively inexpensive, they are easy to oper Betagan) and carbonic anhydrase inhibitors (e.g. ate. From a nursing standpoint, diode lasers are Diamox, Neptazane) are used to decrease aque an easy maintenance item. There are no gas ous production. pressures to regulate, water cooling systems to Some surgical procedures that lower IOP by monitor, filters to change, or mirrors to go out increasing aqueous outflow include trabeculo of alignment. plasty, filtration, goniotomy, trabeculotomy, and iridotomy (Schuman & Puliafito, 1990). Glaucoma Cyclodestructive procedures such as To describe how far patients and physicians
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cyclocryotherapy and cyclophotocoagulation decrease aqueous production by partially elimi nating the function of the ciliary processes (Shields, 1985). Cyclodestructive procedures
80° C for at least 60 seconds was considered to be generally more predictable and less destruc tive than cylcodiathermy (Shields, 1992). Even though cyclocryotherapy is currently the most commonly performed cyclodestructive proce dure, IOP control and visual acuity results remain unpredictable. There are many other reported problems associated with cyclocryotherapy, such as intense postoperative pain, IOP rise, inflammation, hypotony (Alward, 1992), and uveitis. Therefore, ophthalmol ogists have continued to search for a better method of cyclode struction and cyclophoto coagulation is quickly becoming the cyclode stmctive treatment of Figure 1. Semiconductor diode laser with choice.
Cyclodestmctive therapy or ciliary ablation is usually reserved as treatment for those patients with uncontrolled glaucoma despite maximum medical and previous surgical interventions. For more than fifty years, ophthalmologists have been using ciliary ablation to slow the forma tion of aqueous production thereby reducing IOP in eyes with severe glaucoma. Methods to deliver this ablation energy to the eye have included coagulation with diathermy, beta-irra diation, chemicals, ultrasound, freezing, xenon light, and laser light (Gaasterland & Pollack, 1992). The evolutionary path of cyclodestructive technology that led to the development of the G-Probe™ has had its ups and downs. Most of the early cyclodestructive methods proved dis advantageous. Cyclodiathermy, first introduced in 1933 had associated phthisis bulbi, uveitis, hemorrhage, and scleral necrosis (Alward, 1992). Beta-irradiation, used on rabbits in 1948, was damaging to the lens and therefore never adopted for clinical use (Shields, 1985). In 1949, a cycloelectrolysis method using a low frequen cy galvanic current that created a chemical reac Cydophotocoagulation tion of sodium hydroxide which was caustic to Cyclophotocoagulation uses laser energy to the tissues within the ciliary body was attempt oblate the ciliary processes. Lasers emit light ed. It provided no advantage over cyclo with photons in phase with each other in time diathermy and therefore was never clinically and space which is referred to as coherent. popular (Shields, 1985). These photons are also Using ultrasound for ciliary released in such a way ablation began in 1964. By Laser Wavelengths that the resulting light 1985, high-intensity focused is in a narrow range of ultrasonic technique showed wavelengths referred that in addition to decreasing aqueous production by dam to as monochromatic (Shields, 1992). Laseraging the ciliary epithelium, tissue interactions aqueous outflow was also depend on laser light improved due to the separa wavelength, power tion of the sclera from the cil intensity (irradiance), iary body (Shields, 1992). and the composition However, over time, patients Near Green Orange Infrared of the target tissue presented with marked scleral Blue Yellow Red Infrared (Balles & Puliafito, __ L thinning. Staphyloma—the mi i XI I 1990). Laser surgery condition when the uvea 200 300 400 500 600 700 800 900 W avelength (nm) produces three types of bulges into the thinned tissue effects: photo stretched sclera, and ectasia— chemical, mechanical the condition when uveal tis Figure 2 . Laser wavelengths or ionized, and ther sue is not included in the mal. stretched scleral area were often reported. Continued on page 28 Since 1950, freezing the ciliary processes to -
IRIS Medical G-Probe™
In visible L ight
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Overview and new technology in cydodestructive procedures Continued from page 27
Figure 3.
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In a photochemical laser-induced reaction, short-pulsed ultraviolet radiation is used to vaporize and condense target tissue. An example is the excimer laser which operates at a ultravio let wavelength of 193 nm producing a photoablation Melanin Absorption reaction. Neodymium-yttri um aluminum garnet (NdYAG) producing an infrared wavelength of 1,064 nm is the most commonly used mechanical laser-induced reaction. Its action of very intense and extremely short pulse duration of laser light is referred to as photodisrup tion. Lasers producing visible wavelengths that cause ther mal damage to target tissues are argon blue-green (488 nm Wavelength (nm) log units and 514 nm), krypton red (647 nm), tunable organic Melanin absorption dye (560 nm to 650 nm), and semiconductor diode lasers (780 nm to 850 nm) (Balles & Puliafito, 1990). For an illustration of laser wave lengths in relation to the light spectrum, see Figure 2. Referred to as photocoagulation, ther mal effects to target tissue produce local inflam mation and scar ring (Shields, 1992). Laser energy for cyclodestruc tive treatment can be delivered to the ciliary body through transpupillary cyclophotocoag ulation, endophotocoagulation, or transscleral cyclopho tocoagulation. The transpupil lary approach is Figure 4. IRIS Medical G-Probe™ generally used when a clear cornea is present with a large pupil through which to distinctly view the ciliary processes. However, the posterior portion of the ciliary body can be difficult to destroy from this approach (Alward, 1992). Endophotocoagulation is an involved, inva sive procedure which requires a pars plana surgi cal incision approach for the laser probe. For patients who require a vitrectomy for other rea
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sons, this method allows direct visualization of the ciliary processes for laser ablation (Shields, 1992), but is generally too risky to perform solely for cydodestructive purpQses. Ciliary ablation using transscleral laser cyclophotocoagulation was first reported in 1972 using a ruby laser and in 1973 using the neodymium laser (Schuman & Puliafito, 1990). It is still the most popular approach today even though the laser currently being used is the semiconductor diode. The trans-scleral method can be performed either by a contact technique using a probe with the patient lying in a supine position or a non-contact technique through a slit lamp. With both techniques, laser energy is delivered through nonpigmented intact con junctiva and sclera and is absorbed by the pig mented ciliary body. The contact technique is generally preferred over the non-contact method because there is more coagulative necrosis of the ciliary body without conjunctival blistering. This results in less pain, inflammation, and visual loss (Alward, 1992). Currently, the advantages of using a semicon ductor diode laser over the Nd-YAG laser are numerous. Mainly, the complications seen after cyclophotocoagulation are not so severe or harmful to the eye as those observed in cyclocryotherapy. Also, diode laser produces light in the nearinfrared wave length at 810 nm which is almost two times more effective for absorption of uveal melanin than Nd-YAG light at 1,064 nm (Gaasterland & Pollack, 1992), (Figure 3). With the recent FDA approval for commercial use of the IRIS Medical GProbe™ with the IRIS Oculight® SLx Diode Laser for the selective destruction of ciliary processes, patients are experiencing better results with fewer negative side effects. The G-Probe™ is a specially designed quartz glass fiberoptic noninvasive laser handpiece with a tip that assures consistent location and spacing for treatment sites (IRIS Laser System Operator Manual). Its curved surface matches the anatomic curved surface of the scle
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ra (Figure 4). A protrusion of the fiber optic beyond the smooth curved surface on the tip of the probe accurately indents the scleral tissue to reproducible transmission depths ensuring repeatable results with no conjunctival burning at the treatment sites. Burns are then centered on the ciliary process with the laser energy directed parallel to the visual axis. Laser energy misses the equator of the lens making lens pro tection unnecessary. Procedure
Patients are given a retrobulbar block and receive seventeen to nineteen laser applications for 2 seconds spaced half the width of the G-Probe™ apart at 1.5-2.0 Watts power for 270 degrees cir cumference, omitting 90 degrees temporally to avoid hypotony (Gaasterland & Pollack, 1992). It should be noted that dark colored irides will absorb more laser energy than those with less pigmentation and power settings should be adjusted accordingly. While the diode laser is in use with the G-Probe™, safety glasses must be worn by all persons in the treatment room, including the ophthalmologist. It is important to keep the cornea moist throughout the laser procedure. The operator's manual suggests providing moisture at least after every 4th laser application. The G-Probe™ is intended for one time use because build up of debris on the tip of the probe may cause local ized tissue burning. Postoperatively, the patient is patched for 4-6 hours to protect the eye until the retrobulbar injection has worn off. A long acting cycloplegic is prescribed twice a day (b.i.d.) and a steroid is used four times a day (q.i.d.). Both are tapered as inflammation subsides. All glaucoma medica tions used preoperatively are continued with the exception of miotics (Gaasterland & Pollack, 1992). Postoperative discomfort is mild but not as severe as in cyclocryotherapy. Ocular pain is rare but can typically be controlled using Tylenol with codeine and an ice pack. Patients return for an IOP check after twenty-four hours. Summary
When management df glaucoma has exhausted all medical and surgical therapy and the oph thalmologist turns as a last resort to cyclophoto coagulation, the IRIS Medical G-Probe™ used in conjunction with the contact semiconductor diode laser offers a promising alternative for successful treatment for patients with severe glaucoma. S Jill Fishbaugh is the Cornea Center Clinic Coordinator for the Department of Ophthalmology, University of Iowa Hospitals insight
and Clinics in Iowa City IA. She is on the insight Editorial Board and has been a member of ASORN since 1986.
References Alward, W.L.M. (1992). Chapter 14: Laser cyclophotoco agulation. In T. A. Weingeist, S. R. Sneed (Eds.) Laser Surgery In Ophthalmology - Practical Applications (1st ed.) (pp. 159-166.) Norwalk, CT/San Mateo, CA: Appleton & Lange. Balles, M.W., & Puliafxto, C.A. (1990). Semiconductor diode lasers: A new light source in ophthalmology. International-Ophthalmology Clinics, 30(2), 77-83. Gaasterland, D.E., & Pollack, I.P. (1992). Initial experience with a new method of laser transscleral cyclopho tocoagulation for ciliary ablation in severe glauco ma. Transactions o f the American Ophthalmological Society, Vol. LXXXX, 225-246. IRIS Oculight Diode Laser System Operator Manual, Part No. 11256. Chapter 12: IRIS G-Probe, 12-1 to 12-13. Schuman, J.S., & Puliafito, C.A. (1990). Laser cyclophoto coagulation. International Ophthalmology Clinics, 30(2), Spring, 111-119. Shields, M.B. (1992). Chapter 32: Principles of laser surgery for glaucoma. Textbook o f Glaucoma (3rd ed.). (pp. 527-533). Baltimore: Williams & Wilkins. Shields, M.B. (1992). Chapter 37: Cyclodestructive surgery. Textbook o f Glaucoma (3rd ed.). (pp. 612628). Baltimore: Williams & Wilkins. Shields, M.B. (1985). Cyclodestructive surgery for glauco ma: Past, present, and future. Transactions o f the American Ophthalmological Society, Vol. LXXXX, 286-303. Bibliography Gaasterland, D.E., Abrams, D.A., Liebmann, J.N., Pollack, I. P., Ritch, R., Schuman, J.S., Shields, M.B., Wise, J. B., Baird, M.A., & Boutacoff, T.A., (1992). A multi center study of contact diode laser transscleral cyclophotocoagulation in glaucoma patients. ARVO Abstracts. Investigative Ophthalmology and Visual Science 33(Suppl)::1644. Hampton, C., Shields, M.B., Miller, K.N., & Blasini, M. (1990). Evaluation of a protocol for transscleral Nd:YAG cyclophotocoagulation in one hundred patients. Ophthalmology 97:910-917. Hennis, H.L., & Stewart, W.C. (1992). Semiconductor diode laser transscleral cyclophotocoagulation in patients with glaucoma. American Journal of Ophthalmology 113:81-85. Jennings, T., Fuller, T., Vukich, J.A., Lam, T., Joondeph, B.C., Ticho, B., Blair, N.P., & Edward, D.P. (1990). Transscleral contact retinal photocoagulation with and 810 nm semiconductor diode laser. Ophthalmic Surgery 21:492-496. Van Mellaert, C.E., & Missotten, L. (1992). Review article: On the safety of 193-nanometer excimer laser refractive corneal surgery. Refractive & Comeal Surgery, 8, May/June, 235-239.
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