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Title: A new contact neodymium: YAG laser for cyclophotocoagulation

Abstract

A newly developed compact (40 kg), self-contained contact Neodymium:YAG laser produces high-peak, high-energy (800 mJ/pulse), short (1.0 millisecond) pulses with 1 to 3 pulses/exposure. Energy is delivered via a 320-microns cleaved quartz fiber optic probe. Cyclophotocoagulation was performed in five eyes of three medium-sized Dutch-pigmented rabbits. The eyes received exposures of 1 to 3 pulses/exposure. Energy delivered ranged from 100 to 800 mJ/pulse. Histopathology revealed ciliary body disruption and hemorrhage with no damage to overlying sclera. When used for transscleral cyclodiathermy in the rabbit, the laser created significant ciliary body disruption with minimal scleral injury.

Authors:
; ; ; ; ; ;  [1]
  1. (Foundation for Glaucoma Research, San Francisco, CA (United States))
Publication Date:
OSTI Identifier:
5010249
Resource Type:
Journal Article
Resource Relation:
Journal Name: Ophthalmic Surgery; (United States); Journal Volume: 22:6
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; EYES; SENSITIVITY; LASER RADIATION; BIOLOGICAL EFFECTS; NEODYMIUM LASERS; RABBITS; ANIMALS; BODY; BODY AREAS; ELECTROMAGNETIC RADIATION; FACE; HEAD; LASERS; MAMMALS; ORGANS; RADIATIONS; SENSE ORGANS; SOLID STATE LASERS; VERTEBRATES 560400* -- Other Environmental Pollutant Effects

Citation Formats

Iwach, A.G., Drake, M.V., Hoskins, H.D. Jr., Schuster, B.L., Vassiliadis, A., Crawford, J.B., and Hennings, D.R.. A new contact neodymium: YAG laser for cyclophotocoagulation. United States: N. p., 1991. Web.
Iwach, A.G., Drake, M.V., Hoskins, H.D. Jr., Schuster, B.L., Vassiliadis, A., Crawford, J.B., & Hennings, D.R.. A new contact neodymium: YAG laser for cyclophotocoagulation. United States.
Iwach, A.G., Drake, M.V., Hoskins, H.D. Jr., Schuster, B.L., Vassiliadis, A., Crawford, J.B., and Hennings, D.R.. 1991. "A new contact neodymium: YAG laser for cyclophotocoagulation". United States. doi:.
@article{osti_5010249,
title = {A new contact neodymium: YAG laser for cyclophotocoagulation},
author = {Iwach, A.G. and Drake, M.V. and Hoskins, H.D. Jr. and Schuster, B.L. and Vassiliadis, A. and Crawford, J.B. and Hennings, D.R.},
abstractNote = {A newly developed compact (40 kg), self-contained contact Neodymium:YAG laser produces high-peak, high-energy (800 mJ/pulse), short (1.0 millisecond) pulses with 1 to 3 pulses/exposure. Energy is delivered via a 320-microns cleaved quartz fiber optic probe. Cyclophotocoagulation was performed in five eyes of three medium-sized Dutch-pigmented rabbits. The eyes received exposures of 1 to 3 pulses/exposure. Energy delivered ranged from 100 to 800 mJ/pulse. Histopathology revealed ciliary body disruption and hemorrhage with no damage to overlying sclera. When used for transscleral cyclodiathermy in the rabbit, the laser created significant ciliary body disruption with minimal scleral injury.},
doi = {},
journal = {Ophthalmic Surgery; (United States)},
number = ,
volume = 22:6,
place = {United States},
year = 1991,
month = 6
}
  • The effects of a neodymium: YAG laser, working in the free-running mode (1 and 20 millisecond pulses), upon the ciliary body via the transscleral route have been studied using 16 autopsy eyes. The experiments described were designed to find an efficient strategy of transscleral cyclodestruction of the ciliary body. It was found that pulse energies of between 6 and 7 Joules, an exposure duration of 20 milliseconds, and maximal defocusing are optimal. A beam, tangentially oriented and positioned 1/2 to 1 mm posterior to the limbus has a high probability of hitting the ciliary body and damaging the ciliary processes.more » In these experiments a first generation of contact lenses could not be demonstrated to have an advantageous effect.« less
  • Using a rabbit model we investigated the role of pigmentation of the ciliary body in obtaining ciliodestruction by neodymium-YAG transscleral cyclophotocoagulation. There was marked destruction of the ciliary body in pigmented rabbit eyes, but no histologic effect was observed in albino rabbit eyes. These findings suggest that pigmentation of the ciliary body is important for obtaining the desired response from neodymium-YAG transscleral cyclophotocoagulation in rabbit eyes by our technique. Further study is necessary to define the role of pigmentation in human eyes in this treatment modality.
  • A neodymium: YAG laser operating in the thermal mode was used to irradiate isolated intraocular lenses (IOLs) and to perform transscleral cyclophotocoagulation on pseudophakic autopsy eyes to investigate the potential damage to IOL haptics such irradiation may cause. In the isolated IOLs, 70 mJ of energy deformed and partially melted both polymethylmethacrylate (PMMA) and polypropylene haptics. One of the capsular-fixated PC-IOL haptics in an autopsy eye partially melted when irradiated with the maximum energy level (8.8 J), with the aiming beam focused 1 mm posterior to the limbus and maximal posterior focus offset.
  • The cyclodestructive and inflammatory effects of CW Nd:YAG contact laser were compared to those of conventional cryopexy. CW Nd:YAG light transmitted by fiber optic cable and sapphire crystal was applied transsclerally to the ciliary body of pigmented and albino rabbits. Cyclocryopexy was given to a comparable second group. The intraocular pressure (IOP), flare, iritis, cells and conjunctival hyperemia were monitored clinically up to 3 weeks. The breakdown of the blood-aqueous barrier and time course of ocular inflammation was similar for both modalities and IOP was -12.2 +/- 4.2 mm Hg for laser cyclopexy and -15.1 +/- 5.4 mm Hg formore » cyclocryopexy at 3 weeks. Ciliary body lesions were noted in both groups. Overall, albino rabbits showed less histological damage and faster recovery of IOP. Contact cyclophotocoagulation and cyclocryopexy can be considered models of ocular injury. The similarities in ocular irritative response suggest a similar pathophysiologic mechanism underlying the pressure behavior in both thermal mode injuries.« less
  • A number of recent studies have demonstrated the success of Nd:YAG and diode laser transscleral cyclophotocoagulation in the treatment of advanced glaucoma. Wavelength selection, however, has seldom been based on a clear understanding of the optical properties of tissues involved. The optical properties of conjunctiva, sclera, and the ciliary body adjacent to the limbus were investigated to find an optimal wavelength range for transscleral cyclophotocoagulation. The absorption and scattering coefficients of these layers were determined in the 300{endash}1200-nm wavelength range by the use of a one-dimensional inverse adding{endash}doubling method. The measured optical properties of conjunctiva, sclera, and the ciliary bodymore » provide a basis for a comparative analysis of the laser wavelengths used clinically for transscleral cyclophotocoagulation. {copyright} {ital 1996 Optical Society of America.}« less