Biomedical subjects

P Ciavarella

Publications and source records attributed to P Ciavarella.

3 recordsLinked to original sources

PubMed1997

The pattern electroretinogram (PERG) after laser treatment of the peripheral or central retina.

PURPOSE: To understand whether laser photocoagulation of the retina for the treatment of diabetic retinopathy (DR) alters directly or indirectly the function of the macular region. METHODS: Transient pattern electroretinograms (PERGs) to 30' checks have been recorded in DR patients before and 7-10 days after one treatment session (established protocol with Argon laser) of either the peripheral retina (panretinal treatment) or the central retina (paramacular focal treatment). RESULTS: Treatment of the peripheral retina causes, in most eyes, a small increase (about 15% on average) of the PERG amplitude. Focal paramacular treatment causes a marked decrement (about 40% on average) of the PERG amplitude. Simulated retinal amputation induced by focal treatment, obtained by means of adequate stimulus masking, resulted in a 15-20% PERG decrement only. CONCLUSIONS: The PERG increase after peripheral treatment may be due to rearrangement of both retinal and choroideal hemodynamics and does not necessarily result in useful long term changes. The PERG decrease after focal, paramacular treatment is far larger than that expected on the basis of the amputated area only. This may result from thermal and/or toxic damaging effects spreading outside the treated area. The results are relevant for both a better monitoring of central retinal function in the course of laser treatment and a better evaluation of the cost/benefit ratio after photocoagulation in DR.

Adult↗

PubMed1995

Spatial-temporal interactions in the steady-state pattern electroretinogram.

It is currently assumed that steady-state pattern electroretinograms can be obtained only at high rates of pattern reversal. However, steady-state responses can also be obtained at very low temporal frequencies (less than 1 Hz), provided that the reversal is sinusoidal. In five healthy volunteers, we studied the frequency characteristics of the pattern-reversal electroretinogram in response to sinusoidal gratings of 0.4 and 4 c/deg, reversed sinusoidally in contrast at frequencies ranging from 1 to 27 Hz. Steady-state responses dominated by the second harmonic component were obtained at all temporal frequencies tested; the amplitude of the second harmonic changed with stimulus temporal frequency. In the low-temporal-frequency range, stimuli of high spatial frequency appear to elicit larger contribution of generators with sustained or tonic characteristics compared with stimuli of low spatial frequency.

Electroretinography↗

PubMed1993

The second harmonic of the electroretinogram to sinusoidal flicker: spatiotemporal properties and clinical application.

The photopic, focal electroretinogram elicited by sinusoidal modulation (8 Hz) of the luminance of a uniform field (flicker electroretinogram) presented in the macular region contains two main components: the first harmonic at the stimulus frequency (1F) and the second harmonic at twice the stimulus frequency (2F). Physiologic and clinical studies have demonstrated that the 1F originates in the outer retina, whereas the 2F has multiple postreceptoral sources, with a contribution of the innermost retina. The 2F, unlike 1F, is selectively altered in amplitude and phase in the early stages of optic neuritis and glaucoma. Both 1F and 2F are altered in maculopathies. An additional property of the focal electroretinogram is that the 2F, unlike 1F, has a very limited summation area (i.e., the function relating 2F amplitude with stimulus area is saturated for central stimulus sizes of the order of the macular region). This overrepresentation of the macular activity suggests that the 2F component of the flicker electroretinogram may provide a specific macular test even for full-field stimuli presented through opacities of the optical media.

Cataract↗