Effects of cyclophotocoagulation with a neodymium:yttrium-aluminum-garnet laser on corneal sensitivity, intraocular pressure, aqueous tear production, and corneal nerve morphology in eyes of dogs.
OBJECTIVE
To determine effects of cyclophotocoagulation via administration of 100 J with a neodymium:yttrium aluminum garnet (Nd:YAG) laser on corneal touch threshold (CTT), intraocular pressure (IOP), aqueous tear production, and corneal nerve morphology in eyes of dogs.


METHODS
15 dogs.


METHODS
Noncontact Nd:YAG laser was transsclerally applied (10 applications; 25 W for 0.1 seconds for each application to each of 4 quadrants) to the ciliary body of the left eye of 15 dogs; the right eye was the control eye. Corneal integrity, CTT, tear production as measured by the Schirmer tear test (STT), and IOP were evaluated for 14 days following laser treatment. On day 14, dogs were euthanatized, eyes harvested, and corneas stained with gold chloride. Major nerve bundles were analyzed by use of a drawing tube attached to a light microscope, and maximum diameters were measured by use of image analysis software.


RESULTS
All laser-treated eyes had significantly higher CTT values, compared with control eyes. Six of 15 laser-treated eyes developed ulcerative keratitis. On most days, IOP was significantly lower in laser-treated eyes in both morning and evening. Laser-treated eyes had a significant decrease of approximately 1 nerve bundle/corneal quadrant. Values for STT or nerve bundle diameters did not differ significantly.


CONCLUSIONS
Administration of 100 J with a Nd:YAG laser effectively reduced IOP while increasing CTT and caused a significant decrease in number, but not diameter, of major corneal nerve bundles. Nerve damage and corneal hypoesthesia are etiologic factors in ulcerative keratitis following Nd:YAG cyclophotocoagulation.
Weigt
Anne Kelley
AK
Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, VA 24061, USA.
Herring
Ian P
IP
Marfurt
Carl F
CF
Pickett
J Phillip
JP
Duncan
Robert B
RB
Ward
Daniel L
DL
D000818:Animals; D003315:Cornea / Q000294:innervation / Q000502:physiology* / Q000601:surgery; D004285:Dogs / Q000502:physiology* / Q000601:surgery; D005260:Female; D017612:Gold Compounds / Q000737:chemistry; D007429:Intraocular Pressure / Q000502:physiology*; D017075:Laser Coagulation / Q000009:adverse effects / Q000662:veterinary*; D008297:Male; D009882:Ophthalmic Nerve / Q000473:pathology; D013666:Tears / Q000378:metabolism
D017612:Gold Compounds; C038016:gold chloride