Abstract
Purpose: :
To examine the influence of cold pressor test on steady-state-pattern electroretinogram (PERG) in normals and glaucoma patients.
Methods: :
PERG was recorded in 69 subjects with a steady-state stimulus of 8 Hz. 23 healthy control persons (normals), 16 patients with ocular hypertension (OHT) and 30 patients with open-angle glaucoma (12 low tension glaucoma (LTG) and 18 high tension glaucoma (HTG)) were examined. All groups were matched for age and sex. PERG recording occurred at baseline, during cold stimulus using a modified cold pressure test involving immersion of the right hand in 2-4°C cold water for three minutes, and during a subsequent warming up phase of three minutes dipping the hand in 30-35°C warm water. Outcome measures were amplitude and peak time of the first and second harmonic (16Hz and 32 Hz) obtained by Fourier analysis. Blood pressure and heart rate were simultaneously recorded in 21 persons (10 normals and 11 glaucoma patients).
Results: :
In LTG and HTG patients PERG amplitudes (at 16 Hz and 32 Hz) were significantly reduced at baseline (p<0,001) and during the whole test (p<0,016). Patients with OHT did not show any significant difference in amplitude at baseline but showed significantly reduced PERG amplitude at 16 Hz during cold provocation (p = 0,03) and the following warm water phase (p= 0,016). Peak time at 16 Hz shortened in all groups during PERG recording (normals p= 0,005, OHT p = 0,011, LTG p = 0,028, HTG p = 0,048), but did not show any differences between the groups. Peak time at 32 Hz did not show any changes. All subjects showed an increase of systolic (p = 0,005) and diastolic blood pressure (p = 0,005) during cold provocation and a decrease of systolic (p = 0,007) and diastolic blood pressure (p = 0,016) under the following warming up conditions. Heart rate did not demonstrate any changes.
Conclusions: :
In PERG additional stress stimulus using cold pressor test might help to differentiate between normals and OHT patients. The reduced peak time under cold provocation in all groups might be due to an altered neurovascular coupling.
Keywords: electrophysiology: clinical • retina • electroretinography: clinical