Year : 1984 | Volume
: 32 | Issue : 5 | Page : 421--423
Clinical study of the neodymium: Yttrium aluminum-garnet (ND:YAG) laser
VS Nirankari, RD Richards
Department of Ophthalmology, University of Maryland School of Medicine, Baltimore, Maryland, USA
V S Nirankari
Department of Ophthalmology, University of Maryland School of Medicine, Baltimore, Maryland 21201
|How to cite this article:|
Nirankari V S, Richards R D. Clinical study of the neodymium: Yttrium aluminum-garnet (ND:YAG) laser.Indian J Ophthalmol 1984;32:421-423
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Nirankari V S, Richards R D. Clinical study of the neodymium: Yttrium aluminum-garnet (ND:YAG) laser. Indian J Ophthalmol [serial online] 1984 [cited 2022 Dec 6 ];32:421-423
Available from: https://www.ijo.in/text.asp?1984/32/5/421/27528
The Neodymium: Yttrium-AluminumGarnet (Nd:YAG) laser is a solid state laser that delivers pulses in the near infrared (1064 nanometers). Two types of such lasers are currently available. The Q-switched laser consists of single pulses each lasting several billionths of a second (12-20 nanoseconds), whereas the mode-locked laser produces a train of pulses each lasting a trillionth of a second (25-30 picoseconds). Both these lasers concentrate very small amounts of energy into high peak power by delivering energy in a short time. Through this process, they can cut non-pigmented and pigmented ocular tissue by promoting optical breakdown and causing plasma formation with a resultant shock wave. Because the Nd:YAG laser beam is invisible, a helium-neon (HeNe) laser beam is used as focusing device.
We have used the Q-switched Nd:YAG laser to treat a variety of ocular conditions. This paper describes our experiences.
MATERIAL AND METHODS
Our series included 60 eyes of 58 patients. Patients ranged in age from 2 years to 84 years, with a mean age of 63 years. Diagnosis was posterior capsular opacification following extracapsular cataract surgery in 42 eyes, persistent cystoid macular edema (confirmed by fluorescein angiography) with vitreous strands to the surgical wound in eight eyes, blockage of filtration tubes due to vitreous/ pigment debris in four eyes, and avascular cyclitic membranes in six eyes. Follow-up ranged from 3 months to 9 months, with a mean of 5 months.
The Nd:YAg laser used in all patients was an American Medical Optics 100 Q-switched laser. We used it in posterior capsulotomies in 42 eyes due to opacification of the posterior capsule following extracapsular surgery. Of these, 26 eyes were also pseudophakic, with 20 eyes having a posterior chamber lens and six eyes having an anterior chamber lens. The Nd:YAG laser was also used to cut anterior vitreous strands in patients with cystoid macular edema, in patients who had blocked ACTSEB tubes with vitreous or debris, and to cut avascular cyclitic or pupillary membranes.
This procedure, especially its experimental nature, was explained in detail to all patients who underwent it and the patients signed informed consent forms. All laser surgery was performed on an outpatient basis. Most patients who required posterior capsulotomies were dilated. Intraocular pressure was measured in all patients prior to and immediately following use of the Nd:YAG laser and at subsequent follow-up visits. A special contact lens was required in a few patients with excessive movement, and a Gonio lens was used to cut vitreous strands near the limbus.
Power settings were adjusted until a spari, was seen indicating optical breakdown, and treatment continued until the capsule or vitreous strand was cut or over 200 applications had been made. In the latter case, treatment was repeated after a one-week interval.
Following treatment, patients were examined at the slit lamp and intraocular pressure was measured to record any complications. No new topical or systemic medications were prescribed. Patients were seen one week, one month, and three months following treatment, to assess visual acuity and intraocular pressure. Flourescein angiography was done in patients with cystoid macular edema.
Patients requiring posterior capsulotomies were treated with power ranges from 0.4 mJ to 3.1 mJ, with the majority of eyes receiving 40 applications at 1.4 mJ. Vitreous strands were cut with an average of 60 applications at a power setting of 2.1 mJ. Dense cyclitic membranes required a power setting of 4.1 mJ and needed 100-150 applications.
Aphakic eyes: Preoperative vision ranged from count fingers (CF) to 20/40. Following Nd:YAG laser capsulotomy, vision improved in 15 eyes to 20/30 or better. In one eye a retinal detachment which was not visualized prior to treatment was observed following capsulotomy.
Pseudophakic eyes: Vision ranged from 20/100 to 20/40 and improved to an average of 20/30 following capsulotomy.
Cutting of Vitreous Strands
The eight eyes with vitreous strands and persistent cystoid macular edema all showed resolution of the edema with improvement from an average visual acuity of 20/80 to 20/30 over a mean follow-up of 4 months. In three patients, microhyphemas were seen due to inadvertent hits on the iris. These were all controlled by gentle pressure.
Blockage of Filtration Tubes
Blockage of filtration tubes occurred in four eyes, due to vitreous membranes in two eyes and iris pigment debris in two eyes, with elevation of intraocular pressure. The Nd:YAG laser was successful in re-establishing filtration in all four cases.
The Nd:YAG laser was used with power settings of up to 4.1 mJ and 150 applications. Openings of 2-3 mm with adequate visualization of the fundus were noted in all cases.
Complications in our series included hits on the pseudophakos in 11 eyes, vitreous face rupture in six eyes, microhyphemas in three eyes, and transient elevation of intraocular pressure in 10 eyes.
Pulsed Neodymium: Yttrium-AluminumGarnet lasers are now being used to cut intraocular tissue non-invasively. The pioneering work of Aron-Rosa in France,, and Fankhauser in Switzerland with the use of such lasers has encouraged others to fully explore the clinical potential of the Nd:YAG laser.
Our study confirms the efficacy and safety of the Nd: YAG laser. We could cut opaque membranes in the anterior segment of the eye non-invasively with no significant complications. This is consistent with earlier studies.,,, Our success in cutting vitreous strands with resolution of persistent cystoid macular edema was also very heartening and was similar to a previous study by Katzen et al. Previous surgical treatments of cystoid macular edema have had variable results.,
Other successful uses of the Nd:YAG laser in our study included cutting vitreous/ pigment strands blocking filtration tubes and cutting cyclitic membranes. Others have reported its use to reopen closed filtration blebs following trabeculostomy and its use in the posterior segment of the eye to cut vitreous strands close to the retina. Use of the Nd:YAG laser with the addition of a thermal effect by either a longer pulsed. mode, continuous wave, or combination with the argon laser offers a great potential in future applications, including iridotomies, trabeculoplasties, cyclodialysis and retinal photocoagulation.
We feel that both initial clinical and experimental studies show that the pulsed Nd: YAG laser is a relatively safe instrument and provides a new approach to many common ophthalmic diseases.
The Neodymium: Yttrium-AluminumGarnet (Nd:YAG) laser was used to treat patients undergoing posterior capsulotomies, discission of pupillary membranes, and cutting of vitreous strands with cystoid macular edema. This laser is a "cold laser" and cuts intraocular tissue non-invasively. The primary mechanism of action is the mechanical rupture due to a shock wave emanating from an optical breakdown. Indications, results and complications of its treatment are analyzed and newer applications of its use are discussed.
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