Pattern ERG changes in suspected glaucoma.

Pattern ERG (P-ERG) changes were studied in patients with suspected glaucoma. P-ERG was recorded in 48 eyes with good visual acuity, normal visual fields and elevated intraocular pressure ranging between 18 and 26 mm Hg. The amplitude of the P1 wave was within normal limits and ranged between 1.0 and 1.9 microV in 46 eyes (95.8%). In contrast, the amplitude of the N2 wave in 32 eyes (66.6%) was subnormal, ranging between 0.2 and 0.8 microV. The implicit time of the P1 and N2 waves was normal, ranging from 60.1 to 69.4 and from 95.1 to 103.8 ms, respectively. In conclusion, the N2 wave changes of the P-ERG may predict those hypertonic eyes which will eventually develop glaucoma and need early antiglaucoma therapy. On the contrary, in ocular hypertensives with normal N2 wave the development of glaucoma is less likely.

The effect of low-dose interferon treatment on visual evoked potentials.

Patients suffering from chronic viral hepatitis, treated with interferon alpha-2b in a dose of 3 million units trice weekly subcutaneously, were studied. The influence of interferon on the optic nerve was evaluated by measuring the P100 implicit time of the visual evoked potentials. The results before the treatment were compared with those after 6 and 12 months of therapy, as well as with those of normal subjects. There were statistically significant differences between the groups. Furthermore, in 10 of 56 eyes (17.8%) after 6 months of treatment, and 8 of 22 eyes (36.3%) after 12 months of treatment, the P100 was abnormally delayed. The long term neurovisual effects of low-dose interferon are currently under investigation.

Keratoconus and tapetoretinal degeneration.

In a series of 233 keratoconus cases, electroretinograms (ERGs) and visual evoked responses (VERs) were recorded; the results of this study are discussed. In six cases, the ERGs were extinguished, and the VERs were pathologic. In contrast to this, in four cases, ERGs were normal, but VERs were pathologic. Postoperatively the electrophysiologic findings remained the same, and the ophthalmoscopic examination of the eyes revealed the existence of a diffuse tapetoretinal degeneration or a macular lesion. These data show clearly the coexistence in many cases of keratoconus with diffuse tapetoretinal degeneration or macular lesion. The preoperative value of an electrophysiologic study of keratoconus patients is justified to avoid an unneeded corneal transplant.

Intravitreal application of ganciclovir in rabbits: ERG and electron-microscopic findings.

The retinal toxic effect after intravitreal use of ganciclovir has been the subject of our experimental investigation on 20 New Zealand rabbits. Different doses of ganciclovir ranging from 200 to 600 micrograms/0.1 ml were injected intravitreously, and ERG changes were recorded at different time points after drug administration. Finally the animals were killed and the retinal lesions were studied by electron microscopy. According to our experiments, ganciclovir doses of 300-600 micrograms/0.1 ml have a clearly toxic effect on the retina as shown by ERG changes. One month after the injection, the electroretinogram is either extinguished or clearly affected. Noteworthy is the fact that in a dose of 200 micrograms/0.1 ml, the ERG b-wave shows a 20% reduction of its normal amplitude 4 months after ganciclovir delivery. Electron microscopy of the retina revealed in the inner segment of the receptor cells the existence of dilatation and vesiculation of the endoplasmic reticulum in the surrounding nuclear cytoplasm and swelling of the mitochondria with fragmentation of the cristae in several of them. In the outer segment of the photoreceptor cells, degeneration and destruction of the lamellae accompanied by disintegration of the adjacent protoplasm in parts of certain rods and cones appeared. Finally large vacuoles of irregular shape in the synapses and degenerative mitochondria and empty vacuoles in the optic nerve fibers were shown.

ERG and electron microscopic findings after intravitreal use of aminoglycosides.

The electroretinographic (ERG) changes and the retinal lesions shown by electron microscopy were studied in rabbits after intravitreal use of amikacin and tobramycin. We studied 40 eyes of 20 rabbits in which different doses ranging from 250 micrograms to 1000 micrograms of aminoglycosides were injected into the vitreous cavity. Tobramycin, and to some extent amikacin, were toxic to the retina even in doses of 500 micrograms as shown by ERG changes. The pathologic retinal lesions shown by electron microscopy were characterized by membranous inclusions in the retinal pigment epithelium, tumefaction of the photoreceptors, and partial disorganization of the inner layers. In doses of 250 micrograms or less, these two antibiotics seem to be nontoxic after a follow-up of three months.

C wave study in optic neuritis due to demyelinating disease.

The C wave was recorded from 20 eyes suffering from neuritis due to demyelinating disease and in 5 eyes showing optic atrophy due to trauma or to increased intracranial pressure. Our results show that in cases with optic neuritis the C wave amplitude was clearly lower than normal. It is interesting that in the other 'healthy', at least clinically, eye the C wave was subnormal too. On the contrary, in the eyes with optic atrophy the C wave was normal. These findings are against the possibility of an efferent neuronal pathway involvement, which influences the level of the retinal pigment epithelium, and support the view of its involvement during the course of the demyelinating disease that causes the optic neuritis.

[C-wave changes in macular diseases]. / Onde C et pathologie maculaire.

C-wave and ERG records have been taken from patients with juvenile macular degeneration, cone dysfunction syndrome, non exudative macular degeneration and from patients who have taken hydroxychloroquine for more than a year. The study of these recordings showed that in juvenile macular degeneration the involved area might be larger than ophthalmoscopically visible. In cone dysfunction syndrome the prolonged latence implicit time can serve as a further diagnostic sign of the disease. In non exudative macular degeneration there is more extensive R.P.E. involvement than usually believed and finally in hydroxychloroquine retinopathy, the C-wave is a better criterion to monitor the disease than ERG.

Changes of oscillatory potentials of the ERG in diabetic retinopathy.

Disturbances of the oscillatory potentials of the ERG are examined in diabetic patients with and without vascular lesions of the retina. More specifically, the changes of the oscillatory potentials are investigated in relation to the manifestation and evolution of diabetic retinopathy and neovascularization of the optic disk and the retina. Particular stress is laid on the direct relation between the disturbances of the oscillatory potentials and the occurrence of neovascularization, as well as on the prognostic significance of these disturbances.

[Electroretinographic changes in experimental metalloses]. / Altérations de i'ERG dans les métalloses expérimentales.

In this experimental study the authors studied the Eclectroretinographic alterations and the histological lesions after the introduction of foreign bodies of iron and copper into the vitreous body of eyes of rabbits. The ERG alterations depend on the kind of the intraocular foreign body and on the size and the time it remained into the eye. These alterations are characterised either by a parallel diminution of the a and b wave of the ERG, or by an increase of the a wave while the b wave becomes flat. From the histological studies it was found that the iron is deposited into the nucleus and the cytoplasm in the form of granules, while the copper causes a violent inflammatory reaction and is deposited extracellularly.