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Glaucoma
Therapy-resistant Inflammatory Glaucoma – 647nm Krypton and
670nm Diode Lasers for Transscleral Contact Cyclophotocoagulation
Päivi Puska and Ahti Tarkkanen
Helsinki University Eye Hospital
Abstract
Only a few reports exist on the treatment of therapy-resistant inflammatory glaucoma with contact transscleral cyclophotocoagulation
(CPC), and only one in which the red 647nm krypton or 670nm diode lasers are used. The lasers most frequently employed in clinical
practice are the 810nm diode and the 1,064nm neodynium:yttrium–aluminium–garnet (Nd:YAG) lasers. Although transmission through the
sclera is lower with the red 647nm krypton and 670nm diode lasers than with the infrared 810nm diode and Nd:YAG lasers, this is
compensated for by using contact application and compressing the sclera with the probe. Also, the red lasers have a higher affinity for
the pigment epithelium of the pars plicata. Transscleral red laser CPC has proved to be an effective, simple and well tolerated procedure
for the treatment of therapy-resistant inflammatory glaucoma, particularly in adults.
Keywords
Secondary glaucoma, inflammatory glaucoma, cyclophotocoagulation, laser surgery
Disclosure: This study was supported by a grant from the Glaucoma Foundation LUX, Helsinki.
Received: 15 July 2009 Accepted: 27 July 2009
Correspondence: Päiva Puska, Helsinki University Eye Hospital, PO Box 220, 0029 HUS, Helsinki, Finland. E:
Paiva.Puska@hus.fi
Laser Transmission and Absorption cell death, the inflammatory reaction following apoptosis is
The choice of laser type for transscleral cyclophotocoagulation (CPC) minimal.
4,5
The hyperthermia produced in the lesions by the low-
has been based on scleral transmission rather than on efficacy at the power, slow-burn laser may partly explain the mild post-operative
target tissue. Since scleral transmission increases at longer uveitis observed after this treatment modality.
6–13
wavelengths, the lasers most frequently employed in clinical practice
have been the 810nm diode and the 1,064nm neodynium: The mechanism of intraocular pressure (IOP) reduction after CPC
yttrium–aluminium–garnet (Nd:YAG). However, the contact application has been debated. In addition to destroying the epithelium and
with pressure on the sclera increases scleral transmission, especially capillaries of the ciliary processes,
14
the findings support the view
at shorter wavelengths.
1
This increase is 2.5-fold for the krypton laser that non-conventional outflow routes, including uveoscleral
compared with 1.5-fold for the Nd:YAG laser. Moreover, the outflow, are increased after CPC.
7,15
wavelength of red 647nm krypton and 670nm diode lasers is near to
that maximally absorbed by melanin granules (600nm) in the retinal Morphological Changes After
pigment epithelium. Melanin granules absorb 670nm laser twice as Red Laser Cyclophotocoagulation
effectively as 810nm diode laser and six times more effectively A histopathological study of an eye after long-term successful
than 1,064nm Nd:YAG laser.
2
Lesions in the pars plicata of the krypton laser CPC showed that effective ablation of the ciliary
rabbit eye, similar to those obtained using contact Nd:YAG lasers, can processes was achieved and only a slight chronic inflammatory
be produced by red lasers using only half the energy.
3
The poorer reaction was present. Also, the sclera, iris, lens and zonules were
scleral transmission and better absorption by melanin of the red intact.
7
The histological changes observed after 670nm diode laser
lasers indicate that less energy enters the eye, the vitreous humour CPC are essentially identical.
8
With the use of in vivo confocal
and the retina of the contralateral wall of the eye, which may be microscopy, no changes were noted in the corneal layers or sub-
of practical importance. basal nerves after krypton laser CPC. In addition, corneal sensitivity,
tested with the Cochet-Bonnet esthesiometer, was normal, as was
Possible Cellular Effects and Mechanisms of tear fluid secretion.
16
Intraocular Pressure Reduction
The low power (0.4W) and the long duration of application (10 Cyclophotocoagulation in the Treatment of
seconds) may result in parts of the ciliary body lesions being Therapy-resistant Inflammatory Glaucoma
warmed to levels above 43°C but not being coagulated. Such There are only a few reports on the treatment of inflammatory
hyperthermic effects may induce apoptosis in the cellular glaucoma with contact transscleral CPC.
17–22
In most studies 810nm
components of the ciliary body
4
instead of necrosis, which occurs diode lasers were used; in only one study were red 647nm krypton
after coagulative lesions. It is known that, compared with necrotic and 670nm diode lasers used.
9
© TOUCH BRIEFINGS 2009 29
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