Evaluation of short-term increased intraocular pressure on flash- and pattern-generated electroretinograms of dogs

Abstract

Data suggest that short-term increases in IOP affect PERG and FERG waveforms, and PERG waveforms are more sensitive to increases in IOP Differences were not detected between treated and control eyes on histologic examination. Further studies are necessary to determine at what IOP permanent damage to ganglion and photoreceptor cells will develop and whether PERG is a reliable clinical diagnostic technique for use in dogs to reveal retinal damage that is secondary to increased IOP prior to changes in waveforms generated by FERG in dogs.

The effects of medetomidine hydrochloride on the electroretinogram of normal dogs

“…The IOP was significantly higher (mean = 16.48 mmHg) following dilation prior to medetomidine than the mean after medetomidine administration (mean = 14.12 mmHg). With markedly raised IOP, both the flash and pattern ERGs of the dog are depressed 38 . Though there was a significant difference in these IOP means, both values are within the normal reported range for the dog, and any influence on the ERGs is unlikely, but can not be fully excluded 39 .…”

Clinical Signs and Diagnosis of the Canine Primary Glaucomas

“…43 The standard full-field electroretinogram (ERG), which is predominately driven by the outer retina, is generally not helpful in the diagnosis or treatment of glaucoma, especially PACG, in which the IOP increase may be very sudden. 43–45 If IOP is very high, the full-field ERG may be extinguished, and although this has negative prognostic significance, in the authors’ experience it is still possible for vision to be temporarily regained once IOP returns to normal and adequate perfusion to the retina is returned. 24,43–45 …”

“…43–45 If IOP is very high, the full-field ERG may be extinguished, and although this has negative prognostic significance, in the authors’ experience it is still possible for vision to be temporarily regained once IOP returns to normal and adequate perfusion to the retina is returned. 24,43–45 …”

“…43–45 Initial testing in humans and dogs suggests that the PERG is more sensitive than the full-field ERG to IOP increases. 43–45 …”

Response to letter

“…Electroretinography analysis of canine eyes 1 h after elevation of IOP always shows complete absence retinal electrical activity (pattern ERG, scotopic, and photopic ERG responses -manuscript in preparation), which is the best evidence that elevated IOP has significant effects on retinal function as previously reported by other investigators. 8,9 3. We would like to remind authors that Millichamp and Dziezyc study used argon laser to disrupt the anterior lens capsule structure in canine eyes as a model of uveitis induction, 10 which cannot be compared to minimal uveitic changes induced by anterior chamber centesis performed in the manner so the lens damage is avoided.…”