Experimental Use of Semiconductor Diode Laser in Contact Transscleral Cyclophotocoagulation in Rabbits Joel S.
Schuman, MD; John J. Jacobson, MD; Carmen A. Puliafito, MD; Robert J. Noecker, MD; Wini T. Reidy
\s=b\ Acute and long-term effects of contact transscleral semiconductor diode laser cyclophotocoagulation were studied in rabbits. Immediately following cyclo-
photocoagulation, light microscopy
re-
vealed coagulation necrosis of the ciliary pigmented and nonpigmented epithelia and stroma; destruction increased in relation to power. There was architectural disruption with higher energy levels. The findings with diode and continuous-wave contact neodymium-YAG lasers were similar. In rabbits treated and followed up for 6 weeks there was a decrease in intraocular pressure during the observation period (P < .05, paired Student's t test). The gross and light microscopic examination revealed focal atrophy and fibrosis of the ciliary processes, with pigment-laden macrophages on the ciliary processes and in the outflow pathways. Higher energy levels caused lens capsule damage and vitritis. The diode laser produced ciliary destruction similar to the continuous-wave contact neodymium-YAG laser in rabbits, with significant intraocular pressure lowering during the 6-week follow-up. (Arch Ophthalmol. 1990; 108:1152-
1157)
T^he semiconductor diode laser has been used to perform transpupillary retinal photocoagulation and ret¬ inal endophotocoagulation.14 The di¬ ode laser produces light in the 780- to
850-nm spectrum; this is in contrast to the 1064-nm light delivered by the neodymium (Nd)-YAG laser. The Accepted for publication April 3, 1990. From the Morse Laser Center, Howe Laboratory of Ophthalmology, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston. Reprint requests to the Massachusetts Eye and Ear Infirmary, Howe Laboratory of Ophthalmology, Glaucoma Consultation Service, 243 Charles St, Boston, MA 02114 (Dr Schuman).
wavelengths produced by both
in¬ well transmitted by the sciera, but the near infrared light generated by the diode laser has better melanin absorption than the struments
are
longer wavelength light produced by
the Nd-YAG laser.5·6 The infrared light of the diode laser causes ther¬ mal tissue damage, much like the ruby7 and the continuous-wave NdYAG laser.810 We have investigated the use of the semiconductor diode laser for contact transscleral cyclo¬ photocoagulation, and compared this with contact transscleral continuous wave Nd-YAG laser cyclophotocoag¬ ulation. MATERIALS AND METHODS
We performed this study in two phases: investigation of the immediate histo¬ pathologic changes due to contact trans¬ scleral diode laser cyclophotocoagulation (acute phase) as well as an evaluation of the long-term intraocular pressure (IOP) ef¬ fects and histopathologic changes due to contrast transscleral diode laser cyclopho¬ tocoagulation (longitudinal phase). All an¬ imals were treated in accordance with the Association for Research in Vision and Ophthalmology's resolution on the treat¬ ment of animals in research. Animals were anesthetized with intramuscular ketamine (25 mg/kg), xylazine (1.4 mg/kg), and acean
promazine (0.35 mg/kg).
Acute Phase
We compared acute effects with contact transscleral Nd-YAG laser cyclophotocoag¬ ulation. Four dutch-belted rabbits under¬ went contact transscleral continuous wave semiconductor diode laser cyclophotocoag¬ ulation in one eye (818 nm, 400-µ quartz fiberoptic probe, Nidek DC-1200, Palo Alto, Calif); the contralateral eye received con¬ tact transscleral continuous wave Nd-YAG laser cyclophotocoagulation (1064 nm, 600µ quartz fiberoptic fiber with synthetic sapphire tip, Surgical Laser Technologies Ine, Malvern, Pa). With both the diode and
Downloaded From: http://archopht.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
the Nd-YAG lasers, three evenly spaced applications were placed at the limbus in each of the four quadrants, using 0.6, 0.9, 1.8, and 2.7 J, respectively. The eyes were immediately enucleated and fixed in Karnovsky's solution following satisfactory se¬ dation, and the rabbits were killed.
Longitudinal
Phase
Twelve dutch-belted rabbits underwent contact diode cyclophotocoagulation in one eye; the contralateral eye received no treat¬ ment (control eye). The rabbits were fol¬ lowed up for 6 weeks postoperatively prior to enucleation. One group of four rabbits was treated with 0.9 J per application, an¬ other group of four was treated with 1.8 J,
and the last four rabbits were treated with 2.7 J. Twenty evenly spaced applications were placed at the limbus in each group. The IOP was measured in the unrestrained rabbits using 0.5% proparacaine hydro¬ chloric acid preoperatively and three times per week postoperatively by pneumotonography (Digilab, Cambridge, Mass). The eyes were enucleated and examined as in the
acute-phase study. RESULTS Acute Phase
The gross examination revealed
blanching of the ciliary processes at 0.6 J and 0.9 J, with more intense whiten¬ ing at 1.8 J (Color Figs 1 and 2). Explo¬ sive destruction of the ciliary pro¬ cesses was seen occasionally at 1.8 J and frequently at 2.7 J. There were rare instances of scierai perforation at 2.7 J. These findings were confirmed with scanning electron microscopy (Fig 1). Light microscopy revealed co¬ agulation necrosis of the pigmented and nonpigmented ciliary epithelium at all energy levels, with destruction increasing in relation to power. There was coagulation necrosis of the ciliary body stroma and vasculature as well;
this was mild at 0.6 J and moderate at
Color
Fig 1.—Gross photographs demonstrate
tact semiconductor diode laser transscleral
acute lesions with con¬
cyclophotocoagulation.
Black-on-white arrow indicates 0.6 J; black-on-white curved arrow, 0.9 J; white arrow, 1.8 J; and curved white arrow 2.7 J. Note the explosive destruction of the ciliary body with 2.7 J, and the progressive intensity of whitening of ciliary processes with increasing treatment energy.
Color Fig 2.—Gross photographs demonstrate acute lesions with con¬ tact Nd-YAG laser transscleral cyclophotocoagulation. Black-on-white arrow indicates 0.6 J; curved arrow, 0.9 J; white arrow, 1.8 J; and curved white arrow, 2.7 J. Note the striking similarity of lesions to those created with the diode laser. There is explosive destruction of ciliary processes at higher energy levels and progressive intensity of whitening of ciliary processes with increasing treatment energy. Explosive tissue destruc¬ tion is seen in one location treated with 2.7 J (white arrowhead).
Color Fig 3.—High-power gross photographs of contact semiconductor diode transscleral cyclophotocoagulation illustrate focal atrophy of ciliary processes associated with selected chronic lesions at 0.9 J (left). Compare with the acute lesion cre¬ ated with 0.9 J (right).
0.9 to 1.8 J. There
was
architectural
disruption of the ciliary stroma and epithelia at 2.7 J (Fig 2). The findings with diode and Nd-YAG lasers were similar on gross, scanning electron microscopic, and light microscopic ex¬ amination (Figs 1 through 4).
Longitudinal Phase There was a decrease in IOP in all groups. Lowering of IOP below base¬ line was statistically significant by
paired Student's t test through the first 2 weeks postoperatively in group 1 (0.9 J) and throughout the 6-week follow-up (except for one time point) in group 2 (1.8 J); the IOP effects were variable in group 3 (2.7 J) (Fig 5). Gross examination of the globes from the 0.9-J group revealed focal at-
rophy of the ciliary processes in the areas of cyclophotocoagulation, with
occasional vitreous condensation over the lesions (Fig 6). The 1.8-J group had more extensive ciliary process atro¬ phy, with rupture of the lens capsule in one animal. The vitreous body in the rabbit with the ruptured capsule was white and solid. The 2.7-J group had a white solid vitreous body; the ciliary processes
were
not
seen on
gross
ex¬
amination. An occasional peripheral iridotomy was seen in all groups. Scan¬ ning electron microscopy confirmed the presence of ciliary process atrophy in the 0.9-J and 1.8-J groups (color
Fig 3). Light microscopy revealed atrophy and fibrosis of the ciliary nonpigmented and pigmented epithelium and
Downloaded From: http://archopht.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
(Fig 7). The rab¬ bits showed pigment-laden macroph¬ ages on the ciliary processes and in the outflow pathways. There was disorga¬ nization present in some lesions in the 1.8-J group, which was much more pronounced in the 2.7-J group. Lens capsule damage was evident in one rabbit in the 1.8-J group and in all rabbits in the 2.7-J group (Fig 8). The opacified vitreous body contained large amounts of amorphous material (pro¬ tein) and acute and chronic inflamma¬ tory cells. stroma in all groups
COMMENT
Laser cyclophotocoagulation causes destruction of the ciliary processes and lowering of IOP. Treatments have been performed using a ruby laser7 or
1. Scanning electron photomicrographs of acute diode laser lesions illustrate coagula¬ tion necrosis of ciliary epithelium, progressing from minimal at 0.6 J (top left) to mild at 0.9 J (top right) and moderate at 1.8 J (bottom left). The 2.7-J lesion (bottom right) shows architec¬ tural disruption of tissue (arrows). Magnifica¬ tions of the four parts are between X25 and X29.
Fig
—
Fig 2.—Light micrographs of acute diode laser lesions show coagulation necrosis at all energy levels delivered (0.6 J [top left], 0.9 J [top right], 1.8 J [bottom left], and 2.7 J [bottom right]). There is coagulation necrosis of the pigmented and nonpigmented ciliary epithelia (arrows). Stromal coagulation necrosis is evi¬ dent at 0.6 J through 2.7 J, and is more intense at the higher energy levels. Vascular conges¬ tion and thrombosis are evident (asterisks). Architectural disruption is seen at 2.7 J (curved arrow). The coagulation necrosis is progres¬ sively more intense with increasing energy de¬ livered (hematoxylin-eosin, X200).
Fig 3.— Scanning electron photomicrographs of acute Nd-YAG laser lesions illustrate coagulation necrosis of ciliary epithe¬ lium, progressing from minimal at 0.6 J (left, X38) to mild at 0.9 J (center, X35) and moderate at 1.8 J (right, X21).
Downloaded From: http://archopht.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
Fig 4.—Light micrographs of lesions created with contact transscleral Nd-YAG laser cyclo¬ photocoagulation using energy levels identical to those used with the diode laser (0.6 J [top left], 0.9 J [top right], 1.8 J [bottom left], and 2.7 J [bottom right]). Histopathologic findings for the two lasers are nearly the same (hema¬ toxylin-eosin, X200).
Fig 5.—Intraocular pressure (IOP) measurements during the 6-week follow-up of contact semiconductor diode transscleral cyclophotocoagulation in rabbits (left, 0.9 J; center, 1.8 J; and right, 2.7 J). Note the significant decrease in IOP in all groups following cyclophotocoagulation with the most prolonged IOP lowering in rabbits treated with the highest energy levels. The early IOP rise (center and right) is likely related to intraocular inflammation noted clinically.
Fig 6.—Scanning electron micrographs of chronic diode laser lesions show focal atrophy of the ciliary processes. Left, 0.9 J, and right, 1.8 J (arrows) (X28).
Downloaded From: http://archopht.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
Fig 7.—Light micrographs of chronic diode laser lesions demonstrating focal atrophy of the ciliary body 6 weeks after treat¬ ment with cyclophotocoagulation (left, 0.9 J; center, 1.8 J; and right, 2.7 J). Processes are shortened, with fusion occurring in some areas (asterisk). Focal disruption and necrosis of the pigmented and nonpigmented ciliary epithelium is seen at all energy levels. Pigment-laden macrophages are found on the ciliary processes and along the outflow pathways (arrow) (he¬ matoxylin-eosin, X200).
Fig 8.—Breaks in the lens capsule are seen in eye treated wilth 1.8 J (left) and all eyes treated with 2.7 J (right). An abnormal prolifer¬ ation of fibroblastic-appearing cells and extra¬ cellular material is seen underlying the capsu¬ lar breaks (Stevenol's blue, X400). one
Nd-YAG laser (either with a contact probe or a slit-lamp delivery sys¬ tem).917 The results of these experi¬ ments indicate that it is possible to use the semiconductor diode laser for the purpose of contact transscleral cyclo¬
photocoagulation.
The semiconductor diode laser has been used with a slit-lamp delivery
system to perform transpupillary ret¬
inal photocoagulation.13 Puliafito and colleagues4 were the first, to our knowl¬ edge, to report the use of the diode la¬ ser for endophotocoagulation of the
retina. As with the 1064-nm wave¬ length of the Nd-YAG laser, the infra¬ red wavelength of the diode laser pen¬ etrates the sclera well, and the diode laser is well suited for transscleral cy¬
clophotocoagulation. Lowering of IOP was achieved with
contact transscleral semiconductor di¬
ode laser cyclophotocoagulation for the 6-week follow-up of the study in rabbits treated with 1.8 to 2.7 J; rabbits treated with 0.9 J tended to return to baseline IOP within 3 to 5 weeks after treatment. These results are similar to those of Wilensky and coauthors, ' ' who
found
a
reduction in IOP
noncontact Nd-YAG laser
following cyclophoto¬
coagulation in rabbits, with a return of
the IOP to baseline in 2 to 6 weeks, as well as the findings of Latina and coworkers,' who described comparable effects with contact Nd-YAG laser cy¬
clophotocoagulation.
Short-duration IOP elevations were with 1.8-J and 2.7-J treatments, and were more pronounced with higher energy procedures. There was a profound and prolonged IOP lowering following the IOP rises; however, the intense IOP decrease in these cases may be related to the intraocular in¬ flammatory response, either related to decreased aqueous production or in¬ creased aqueous egress (through con¬ ventional outflow pathways, or transseen
sclerally, as suggested by some authors17). Lens capsule rupture and vitreous opacification were only seen in eyes that developed a transient pressure elevation followed by a deep and prolonged IOP decrease.
Contact transscleral semiconductor diode laser cyclophotocoagulation pro¬ duced coagulation necrosis, and subse-
Downloaded From: http://archopht.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
quent atrophy, of the ciliary body with
prolonged IOP lowering in rabbits. Higher energies correlated with greater tissue damage on gross and histologie examination. Energies of 1.8 J or higher ruptured the lens capsule
with resultant intraocular inflamma¬ tion in this animal model. There did not appear to be a significant differ¬ ence histologically in lesions created with the diode laser and those pro¬ duced with the Nd-YAG laser. This study demonstrated that the semiconductor diode laser can be used to perform contact transscleral cyclo¬ photocoagulation, and this treatment results in ciliary body coagulation ne¬ crosis and IOP lowering. Moreover, the effects of this laser are titratable and localized, with greater tissue damage occurring at the higher energy levels delivered. The semiconductor diode la¬ ser provides excellent scierai energy transmittance and better melanin ab¬ sorption than longer wavelength la¬ sers. In addition, the diode laser offers the advantages of portability, small size, and light weight, and it uses standard current and air-cooling.
This study was supported by the Heed Oph¬ thalmic Foundation, Chicago, 111 (Dr Schuman); National Institutes of Health grant 5T32 EY07097-02 (Dr Schuman); and the Office of Na-
val
Research
contract
N0014-86K-0117
Puliafito).
(Dr
The authors have no proprietary interest in the devices used in this study.
The authors are most grateful to Ellen Hertzmark for her assistance with statistical analysis of the data.
References 1. McHugh JDA, Marshall J, Capon M, Rothery S, Raven A, Naylor RP. Transpupillary retinal
photocoagulation in the eyes of rabbit and human using a diode laser. Lasers Light Ophthalmol. 1988;2:125-143.
2. Brancato R, Pratesi R, Leoni G, Trabucchi G, Vanni U. Histopathology of diode and argon laser lesions in rabbit retina: a comparative study. Invest Ophthalmol Vis Sci. 1989;30:1504-1510. 3. Brancato R, Pratesi R, Leoni G, Trabucchi G, Vanni U. Semiconductor diode laser photocoagulation of human malignant melanoma. Am J Ophthalmol. 1989;107:295-296. 4. Puliafito CA, Deutsch TF, Boll J, To K. Semiconductor laser endophotocoagulation of the retina. Arch Ophthalmol. 1987;105:424-427. 5. Smith RS, Stein MN. Ocular hazards of transscleral laser radiation, I: spectral reflection and transmission of the sclera, choroid and retina. Am J Ophthalmol. 1968;66:21-31. 6. Watts GK. Retinal hazards during laser irradiation of the iris. Br J Ophthalmol. 1971; 55:60-67. 7. Beckman H, Kinoshita A, Rota AN, Sugar
HS. Transscleral ruby laser irradiation of the ciliary body in the treatment of intractable glaucoma. Trans Am Acad Ophthalmol Otolaryngol.
1972;46:423-436. 8. Allingham RR, de Kater AW, Bellows AR, Hsu J. Probe placement and power levels in contact transscleral neodymium:YAG cyclophotocoagulation. Arch Ophthalmol. 1990;108:738-742. 9. Latina MA, Patel S, de Kater AW, Goode S, Nishioka NS, Puliafito CA. Transscleral cyclophotocoagulation using a contact laser probe: a histologic and clinical study in rabbits. Lasers Surg
Med. 1989;9:437. 10. Brancato R, Leoni G, Trabucchi G, Trabucchi E. Transscleral contact cyclophotocoagulation with CW Nd:YAG laser: experimental study on rabbit eyes. Int J Tissue React. 1987;6:493-498. 11. Wilensky JT, Welch D, Mirolovich M. Transscleral cyclocoagulation using a neodymium:YAG laser. Ophthalmic Surg. 1985;16:95\x=req-\ 98. 12. Fankhauser F, van der Zypen E, Kwasniewska S, Rol P, England C. Transscleral
cyclophotocoagulation using
a
laser. Ophthalmic Surg. 1986;17:94-100. 13. England C, van der Zypen E, Fankhauser F, Kwasniewska S. Ultrastructure of the rabbit ciliary body following transscleral cyclophotocoagulation with the free-running Nd:YAG laser: preliminary findings. Lasers Ophthalmol. 1986;1:61\x=req-\ 72. 14. Federman JL, Ando F, Schubert HD, Eagle RC. Contact laser for transscleral photocoagulation. Ophthalmic Surg. 1987;18:183-184. 15. Schubert HD, Federman JL. A comparison of CW Nd:YAG contact transscleral cyclophotocoagulation with cyclocryopexy. Invest Ophthalmol Vis Sci. 1989;30:536-542. 16. Schubert HD, Federman JL. The role of inflammation in CW Nd:YAG contact transscleral photocoagulation and cryopexy. Invest Ophthalmol Vis Sci. 1989;30:543-549. 17. Schubert HD. Noncontact and contact pars plana transscleral Nd:YAG laser cyclophotocoagulation in postmortem eyes. Ophthalmology.
1989;96:1471-1475.
neodymium:YAG
Currently in Other AMA Journals ARCHIVES OF NEUROLOGY The Clinical Course of Multiple Sclerosis During Pregnancy and the
Puerperium Kathy Birk, MD; Corey Ford, MD; Suzanne Smeltzer, RN, EdD; Daniel Ryan, MD; Richard Miller, PhD; Richard A. Rudick, MD (Arch Neurol. 1990;47:738-742) Viral Antibodies in Multiple Sclerosis: A Nationwide Co-twin Study Esko Kinnunen, MD; Martii Valle, MD; Liisa Piirainen, MSc; Marjaana Kleemola, MD; Marja-Keena Kantanen, MSc; Juhani Juntunen, MD; Matti Klockars, MD; Markku Koskenvuo, MD (Arch Neurol. 1990;47:743-746) Positron Emission Tomography Study in Progressive Supranuclear Palsy: Brain Hypometabolic Pattern and Clinicometabolic Correlations Jerome Blin, MD; Jean Claude Baron, MD; Bruno Dubois, MD; Bernard Pillon, PhD; Henri Cambon, MD; Jean Cambier, MD; Yves Agid, MD, PhD (Arch Neurol. 1990;47:747752) Isolated Pupil-Sparing Third-Nerve Palsy as the Presenting Sign of Multiple Sclerosis Nancy J. Newman, MD, Simmons Lessell, MD (Arch Neurol. 1990;47:817-818)
Downloaded From: http://archopht.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
Schuman, MD; John J. Jacobson, MD; Carmen A. Puliafito, MD; Robert J. Noecker, MD; Wini T. Reidy
\s=b\ Acute and long-term effects of contact transscleral semiconductor diode laser cyclophotocoagulation were studied in rabbits. Immediately following cyclo-
photocoagulation, light microscopy
re-
vealed coagulation necrosis of the ciliary pigmented and nonpigmented epithelia and stroma; destruction increased in relation to power. There was architectural disruption with higher energy levels. The findings with diode and continuous-wave contact neodymium-YAG lasers were similar. In rabbits treated and followed up for 6 weeks there was a decrease in intraocular pressure during the observation period (P < .05, paired Student's t test). The gross and light microscopic examination revealed focal atrophy and fibrosis of the ciliary processes, with pigment-laden macrophages on the ciliary processes and in the outflow pathways. Higher energy levels caused lens capsule damage and vitritis. The diode laser produced ciliary destruction similar to the continuous-wave contact neodymium-YAG laser in rabbits, with significant intraocular pressure lowering during the 6-week follow-up. (Arch Ophthalmol. 1990; 108:1152-
1157)
T^he semiconductor diode laser has been used to perform transpupillary retinal photocoagulation and ret¬ inal endophotocoagulation.14 The di¬ ode laser produces light in the 780- to
850-nm spectrum; this is in contrast to the 1064-nm light delivered by the neodymium (Nd)-YAG laser. The Accepted for publication April 3, 1990. From the Morse Laser Center, Howe Laboratory of Ophthalmology, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston. Reprint requests to the Massachusetts Eye and Ear Infirmary, Howe Laboratory of Ophthalmology, Glaucoma Consultation Service, 243 Charles St, Boston, MA 02114 (Dr Schuman).
wavelengths produced by both
in¬ well transmitted by the sciera, but the near infrared light generated by the diode laser has better melanin absorption than the struments
are
longer wavelength light produced by
the Nd-YAG laser.5·6 The infrared light of the diode laser causes ther¬ mal tissue damage, much like the ruby7 and the continuous-wave NdYAG laser.810 We have investigated the use of the semiconductor diode laser for contact transscleral cyclo¬ photocoagulation, and compared this with contact transscleral continuous wave Nd-YAG laser cyclophotocoag¬ ulation. MATERIALS AND METHODS
We performed this study in two phases: investigation of the immediate histo¬ pathologic changes due to contact trans¬ scleral diode laser cyclophotocoagulation (acute phase) as well as an evaluation of the long-term intraocular pressure (IOP) ef¬ fects and histopathologic changes due to contrast transscleral diode laser cyclopho¬ tocoagulation (longitudinal phase). All an¬ imals were treated in accordance with the Association for Research in Vision and Ophthalmology's resolution on the treat¬ ment of animals in research. Animals were anesthetized with intramuscular ketamine (25 mg/kg), xylazine (1.4 mg/kg), and acean
promazine (0.35 mg/kg).
Acute Phase
We compared acute effects with contact transscleral Nd-YAG laser cyclophotocoag¬ ulation. Four dutch-belted rabbits under¬ went contact transscleral continuous wave semiconductor diode laser cyclophotocoag¬ ulation in one eye (818 nm, 400-µ quartz fiberoptic probe, Nidek DC-1200, Palo Alto, Calif); the contralateral eye received con¬ tact transscleral continuous wave Nd-YAG laser cyclophotocoagulation (1064 nm, 600µ quartz fiberoptic fiber with synthetic sapphire tip, Surgical Laser Technologies Ine, Malvern, Pa). With both the diode and
Downloaded From: http://archopht.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
the Nd-YAG lasers, three evenly spaced applications were placed at the limbus in each of the four quadrants, using 0.6, 0.9, 1.8, and 2.7 J, respectively. The eyes were immediately enucleated and fixed in Karnovsky's solution following satisfactory se¬ dation, and the rabbits were killed.
Longitudinal
Phase
Twelve dutch-belted rabbits underwent contact diode cyclophotocoagulation in one eye; the contralateral eye received no treat¬ ment (control eye). The rabbits were fol¬ lowed up for 6 weeks postoperatively prior to enucleation. One group of four rabbits was treated with 0.9 J per application, an¬ other group of four was treated with 1.8 J,
and the last four rabbits were treated with 2.7 J. Twenty evenly spaced applications were placed at the limbus in each group. The IOP was measured in the unrestrained rabbits using 0.5% proparacaine hydro¬ chloric acid preoperatively and three times per week postoperatively by pneumotonography (Digilab, Cambridge, Mass). The eyes were enucleated and examined as in the
acute-phase study. RESULTS Acute Phase
The gross examination revealed
blanching of the ciliary processes at 0.6 J and 0.9 J, with more intense whiten¬ ing at 1.8 J (Color Figs 1 and 2). Explo¬ sive destruction of the ciliary pro¬ cesses was seen occasionally at 1.8 J and frequently at 2.7 J. There were rare instances of scierai perforation at 2.7 J. These findings were confirmed with scanning electron microscopy (Fig 1). Light microscopy revealed co¬ agulation necrosis of the pigmented and nonpigmented ciliary epithelium at all energy levels, with destruction increasing in relation to power. There was coagulation necrosis of the ciliary body stroma and vasculature as well;
this was mild at 0.6 J and moderate at
Color
Fig 1.—Gross photographs demonstrate
tact semiconductor diode laser transscleral
acute lesions with con¬
cyclophotocoagulation.
Black-on-white arrow indicates 0.6 J; black-on-white curved arrow, 0.9 J; white arrow, 1.8 J; and curved white arrow 2.7 J. Note the explosive destruction of the ciliary body with 2.7 J, and the progressive intensity of whitening of ciliary processes with increasing treatment energy.
Color Fig 2.—Gross photographs demonstrate acute lesions with con¬ tact Nd-YAG laser transscleral cyclophotocoagulation. Black-on-white arrow indicates 0.6 J; curved arrow, 0.9 J; white arrow, 1.8 J; and curved white arrow, 2.7 J. Note the striking similarity of lesions to those created with the diode laser. There is explosive destruction of ciliary processes at higher energy levels and progressive intensity of whitening of ciliary processes with increasing treatment energy. Explosive tissue destruc¬ tion is seen in one location treated with 2.7 J (white arrowhead).
Color Fig 3.—High-power gross photographs of contact semiconductor diode transscleral cyclophotocoagulation illustrate focal atrophy of ciliary processes associated with selected chronic lesions at 0.9 J (left). Compare with the acute lesion cre¬ ated with 0.9 J (right).
0.9 to 1.8 J. There
was
architectural
disruption of the ciliary stroma and epithelia at 2.7 J (Fig 2). The findings with diode and Nd-YAG lasers were similar on gross, scanning electron microscopic, and light microscopic ex¬ amination (Figs 1 through 4).
Longitudinal Phase There was a decrease in IOP in all groups. Lowering of IOP below base¬ line was statistically significant by
paired Student's t test through the first 2 weeks postoperatively in group 1 (0.9 J) and throughout the 6-week follow-up (except for one time point) in group 2 (1.8 J); the IOP effects were variable in group 3 (2.7 J) (Fig 5). Gross examination of the globes from the 0.9-J group revealed focal at-
rophy of the ciliary processes in the areas of cyclophotocoagulation, with
occasional vitreous condensation over the lesions (Fig 6). The 1.8-J group had more extensive ciliary process atro¬ phy, with rupture of the lens capsule in one animal. The vitreous body in the rabbit with the ruptured capsule was white and solid. The 2.7-J group had a white solid vitreous body; the ciliary processes
were
not
seen on
gross
ex¬
amination. An occasional peripheral iridotomy was seen in all groups. Scan¬ ning electron microscopy confirmed the presence of ciliary process atrophy in the 0.9-J and 1.8-J groups (color
Fig 3). Light microscopy revealed atrophy and fibrosis of the ciliary nonpigmented and pigmented epithelium and
Downloaded From: http://archopht.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
(Fig 7). The rab¬ bits showed pigment-laden macroph¬ ages on the ciliary processes and in the outflow pathways. There was disorga¬ nization present in some lesions in the 1.8-J group, which was much more pronounced in the 2.7-J group. Lens capsule damage was evident in one rabbit in the 1.8-J group and in all rabbits in the 2.7-J group (Fig 8). The opacified vitreous body contained large amounts of amorphous material (pro¬ tein) and acute and chronic inflamma¬ tory cells. stroma in all groups
COMMENT
Laser cyclophotocoagulation causes destruction of the ciliary processes and lowering of IOP. Treatments have been performed using a ruby laser7 or
1. Scanning electron photomicrographs of acute diode laser lesions illustrate coagula¬ tion necrosis of ciliary epithelium, progressing from minimal at 0.6 J (top left) to mild at 0.9 J (top right) and moderate at 1.8 J (bottom left). The 2.7-J lesion (bottom right) shows architec¬ tural disruption of tissue (arrows). Magnifica¬ tions of the four parts are between X25 and X29.
Fig
—
Fig 2.—Light micrographs of acute diode laser lesions show coagulation necrosis at all energy levels delivered (0.6 J [top left], 0.9 J [top right], 1.8 J [bottom left], and 2.7 J [bottom right]). There is coagulation necrosis of the pigmented and nonpigmented ciliary epithelia (arrows). Stromal coagulation necrosis is evi¬ dent at 0.6 J through 2.7 J, and is more intense at the higher energy levels. Vascular conges¬ tion and thrombosis are evident (asterisks). Architectural disruption is seen at 2.7 J (curved arrow). The coagulation necrosis is progres¬ sively more intense with increasing energy de¬ livered (hematoxylin-eosin, X200).
Fig 3.— Scanning electron photomicrographs of acute Nd-YAG laser lesions illustrate coagulation necrosis of ciliary epithe¬ lium, progressing from minimal at 0.6 J (left, X38) to mild at 0.9 J (center, X35) and moderate at 1.8 J (right, X21).
Downloaded From: http://archopht.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
Fig 4.—Light micrographs of lesions created with contact transscleral Nd-YAG laser cyclo¬ photocoagulation using energy levels identical to those used with the diode laser (0.6 J [top left], 0.9 J [top right], 1.8 J [bottom left], and 2.7 J [bottom right]). Histopathologic findings for the two lasers are nearly the same (hema¬ toxylin-eosin, X200).
Fig 5.—Intraocular pressure (IOP) measurements during the 6-week follow-up of contact semiconductor diode transscleral cyclophotocoagulation in rabbits (left, 0.9 J; center, 1.8 J; and right, 2.7 J). Note the significant decrease in IOP in all groups following cyclophotocoagulation with the most prolonged IOP lowering in rabbits treated with the highest energy levels. The early IOP rise (center and right) is likely related to intraocular inflammation noted clinically.
Fig 6.—Scanning electron micrographs of chronic diode laser lesions show focal atrophy of the ciliary processes. Left, 0.9 J, and right, 1.8 J (arrows) (X28).
Downloaded From: http://archopht.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
Fig 7.—Light micrographs of chronic diode laser lesions demonstrating focal atrophy of the ciliary body 6 weeks after treat¬ ment with cyclophotocoagulation (left, 0.9 J; center, 1.8 J; and right, 2.7 J). Processes are shortened, with fusion occurring in some areas (asterisk). Focal disruption and necrosis of the pigmented and nonpigmented ciliary epithelium is seen at all energy levels. Pigment-laden macrophages are found on the ciliary processes and along the outflow pathways (arrow) (he¬ matoxylin-eosin, X200).
Fig 8.—Breaks in the lens capsule are seen in eye treated wilth 1.8 J (left) and all eyes treated with 2.7 J (right). An abnormal prolifer¬ ation of fibroblastic-appearing cells and extra¬ cellular material is seen underlying the capsu¬ lar breaks (Stevenol's blue, X400). one
Nd-YAG laser (either with a contact probe or a slit-lamp delivery sys¬ tem).917 The results of these experi¬ ments indicate that it is possible to use the semiconductor diode laser for the purpose of contact transscleral cyclo¬
photocoagulation.
The semiconductor diode laser has been used with a slit-lamp delivery
system to perform transpupillary ret¬
inal photocoagulation.13 Puliafito and colleagues4 were the first, to our knowl¬ edge, to report the use of the diode la¬ ser for endophotocoagulation of the
retina. As with the 1064-nm wave¬ length of the Nd-YAG laser, the infra¬ red wavelength of the diode laser pen¬ etrates the sclera well, and the diode laser is well suited for transscleral cy¬
clophotocoagulation. Lowering of IOP was achieved with
contact transscleral semiconductor di¬
ode laser cyclophotocoagulation for the 6-week follow-up of the study in rabbits treated with 1.8 to 2.7 J; rabbits treated with 0.9 J tended to return to baseline IOP within 3 to 5 weeks after treatment. These results are similar to those of Wilensky and coauthors, ' ' who
found
a
reduction in IOP
noncontact Nd-YAG laser
following cyclophoto¬
coagulation in rabbits, with a return of
the IOP to baseline in 2 to 6 weeks, as well as the findings of Latina and coworkers,' who described comparable effects with contact Nd-YAG laser cy¬
clophotocoagulation.
Short-duration IOP elevations were with 1.8-J and 2.7-J treatments, and were more pronounced with higher energy procedures. There was a profound and prolonged IOP lowering following the IOP rises; however, the intense IOP decrease in these cases may be related to the intraocular in¬ flammatory response, either related to decreased aqueous production or in¬ creased aqueous egress (through con¬ ventional outflow pathways, or transseen
sclerally, as suggested by some authors17). Lens capsule rupture and vitreous opacification were only seen in eyes that developed a transient pressure elevation followed by a deep and prolonged IOP decrease.
Contact transscleral semiconductor diode laser cyclophotocoagulation pro¬ duced coagulation necrosis, and subse-
Downloaded From: http://archopht.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
quent atrophy, of the ciliary body with
prolonged IOP lowering in rabbits. Higher energies correlated with greater tissue damage on gross and histologie examination. Energies of 1.8 J or higher ruptured the lens capsule
with resultant intraocular inflamma¬ tion in this animal model. There did not appear to be a significant differ¬ ence histologically in lesions created with the diode laser and those pro¬ duced with the Nd-YAG laser. This study demonstrated that the semiconductor diode laser can be used to perform contact transscleral cyclo¬ photocoagulation, and this treatment results in ciliary body coagulation ne¬ crosis and IOP lowering. Moreover, the effects of this laser are titratable and localized, with greater tissue damage occurring at the higher energy levels delivered. The semiconductor diode la¬ ser provides excellent scierai energy transmittance and better melanin ab¬ sorption than longer wavelength la¬ sers. In addition, the diode laser offers the advantages of portability, small size, and light weight, and it uses standard current and air-cooling.
This study was supported by the Heed Oph¬ thalmic Foundation, Chicago, 111 (Dr Schuman); National Institutes of Health grant 5T32 EY07097-02 (Dr Schuman); and the Office of Na-
val
Research
contract
N0014-86K-0117
Puliafito).
(Dr
The authors have no proprietary interest in the devices used in this study.
The authors are most grateful to Ellen Hertzmark for her assistance with statistical analysis of the data.
References 1. McHugh JDA, Marshall J, Capon M, Rothery S, Raven A, Naylor RP. Transpupillary retinal
photocoagulation in the eyes of rabbit and human using a diode laser. Lasers Light Ophthalmol. 1988;2:125-143.
2. Brancato R, Pratesi R, Leoni G, Trabucchi G, Vanni U. Histopathology of diode and argon laser lesions in rabbit retina: a comparative study. Invest Ophthalmol Vis Sci. 1989;30:1504-1510. 3. Brancato R, Pratesi R, Leoni G, Trabucchi G, Vanni U. Semiconductor diode laser photocoagulation of human malignant melanoma. Am J Ophthalmol. 1989;107:295-296. 4. Puliafito CA, Deutsch TF, Boll J, To K. Semiconductor laser endophotocoagulation of the retina. Arch Ophthalmol. 1987;105:424-427. 5. Smith RS, Stein MN. Ocular hazards of transscleral laser radiation, I: spectral reflection and transmission of the sclera, choroid and retina. Am J Ophthalmol. 1968;66:21-31. 6. Watts GK. Retinal hazards during laser irradiation of the iris. Br J Ophthalmol. 1971; 55:60-67. 7. Beckman H, Kinoshita A, Rota AN, Sugar
HS. Transscleral ruby laser irradiation of the ciliary body in the treatment of intractable glaucoma. Trans Am Acad Ophthalmol Otolaryngol.
1972;46:423-436. 8. Allingham RR, de Kater AW, Bellows AR, Hsu J. Probe placement and power levels in contact transscleral neodymium:YAG cyclophotocoagulation. Arch Ophthalmol. 1990;108:738-742. 9. Latina MA, Patel S, de Kater AW, Goode S, Nishioka NS, Puliafito CA. Transscleral cyclophotocoagulation using a contact laser probe: a histologic and clinical study in rabbits. Lasers Surg
Med. 1989;9:437. 10. Brancato R, Leoni G, Trabucchi G, Trabucchi E. Transscleral contact cyclophotocoagulation with CW Nd:YAG laser: experimental study on rabbit eyes. Int J Tissue React. 1987;6:493-498. 11. Wilensky JT, Welch D, Mirolovich M. Transscleral cyclocoagulation using a neodymium:YAG laser. Ophthalmic Surg. 1985;16:95\x=req-\ 98. 12. Fankhauser F, van der Zypen E, Kwasniewska S, Rol P, England C. Transscleral
cyclophotocoagulation using
a
laser. Ophthalmic Surg. 1986;17:94-100. 13. England C, van der Zypen E, Fankhauser F, Kwasniewska S. Ultrastructure of the rabbit ciliary body following transscleral cyclophotocoagulation with the free-running Nd:YAG laser: preliminary findings. Lasers Ophthalmol. 1986;1:61\x=req-\ 72. 14. Federman JL, Ando F, Schubert HD, Eagle RC. Contact laser for transscleral photocoagulation. Ophthalmic Surg. 1987;18:183-184. 15. Schubert HD, Federman JL. A comparison of CW Nd:YAG contact transscleral cyclophotocoagulation with cyclocryopexy. Invest Ophthalmol Vis Sci. 1989;30:536-542. 16. Schubert HD, Federman JL. The role of inflammation in CW Nd:YAG contact transscleral photocoagulation and cryopexy. Invest Ophthalmol Vis Sci. 1989;30:543-549. 17. Schubert HD. Noncontact and contact pars plana transscleral Nd:YAG laser cyclophotocoagulation in postmortem eyes. Ophthalmology.
1989;96:1471-1475.
neodymium:YAG
Currently in Other AMA Journals ARCHIVES OF NEUROLOGY The Clinical Course of Multiple Sclerosis During Pregnancy and the
Puerperium Kathy Birk, MD; Corey Ford, MD; Suzanne Smeltzer, RN, EdD; Daniel Ryan, MD; Richard Miller, PhD; Richard A. Rudick, MD (Arch Neurol. 1990;47:738-742) Viral Antibodies in Multiple Sclerosis: A Nationwide Co-twin Study Esko Kinnunen, MD; Martii Valle, MD; Liisa Piirainen, MSc; Marjaana Kleemola, MD; Marja-Keena Kantanen, MSc; Juhani Juntunen, MD; Matti Klockars, MD; Markku Koskenvuo, MD (Arch Neurol. 1990;47:743-746) Positron Emission Tomography Study in Progressive Supranuclear Palsy: Brain Hypometabolic Pattern and Clinicometabolic Correlations Jerome Blin, MD; Jean Claude Baron, MD; Bruno Dubois, MD; Bernard Pillon, PhD; Henri Cambon, MD; Jean Cambier, MD; Yves Agid, MD, PhD (Arch Neurol. 1990;47:747752) Isolated Pupil-Sparing Third-Nerve Palsy as the Presenting Sign of Multiple Sclerosis Nancy J. Newman, MD, Simmons Lessell, MD (Arch Neurol. 1990;47:817-818)
Downloaded From: http://archopht.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
