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A.M. Palmowski, W. Vilser, U. Laak, D. Müller, K.W. Ruprecht; Retinal Perfusion Response to a Multifocal M-Sequence Flicker Stimulation . Invest. Ophthalmol. Vis. Sci. 2003;44(13):105.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To assess, if a slow multifocal stimulus (mfS) can provoke a perfusion response that can be measured with the retinal vessel analyzer (RVA). In the mfERG this stimulus seemed to be more sensitive to normal tension glaucoma (NTG) than to high tension glaucoma (HTG) (Allgayer, 2000), pointing to a possible underlying difference in retinal perfusion.While an influence of light on retinal perfusion has been documented for flicker illumination (Polak, 2002) little is known about the perfusion changes induced by the mfERG stimulation. Methods: 17 eyes were examined. Pupils were dilated. A 120 s baseline recording was obtained with the RVA. With the RVA still turned on, the patient then turned to view a mfS on a monochrome monitor for 56 ms. The mfS consisted of 103 hexagons flickering according to an m-sequence with a stimulus base interval of 54 ms, stimulating the central 50° of the retina (Lmax 100cd/m^2, Lmin<1cd/m^2). Immediately thereafter the patient turned to the RVA, where measurements were resumed as soon as the same retinal vessel was targeted (ideal starting point at 176 s) and continued for 104 s. Stimulation and recording was then repeated twice.Results: The diameter of a retinal vein and artery was measured for a length of at least 1 mm. For each vessel, the 3 consecutive measurements were normalized to the mean of the baseline and superimposed to generate a mean response curve. The maximum of the vessel response at the end of mfS was obtained by linear interpolation of the measured response within the 20 ms following mfS, as previous studies have shown a flicker response to occur within this time frame. On average veins dilated by 6.8% and arteries by 7% following mfS (p>0.005). Such a dilatation could be observed in 9 veins and in 7 arteries. 3 venous and 2 arterial measurements did not show a dilatation following mfS. However, 13 of 34 measurements could not be analyzed due to signal problems or because the time from the end of mfS and the uptake of measurement exceeded 20 ms.Conclusions: The visual stimulus applied in the mfERG results in a dilatation of arteries and veins that can be measured with the RVA. Coupling a mfS to the RVA has the potential to topographically map changes in retinal perfusion in relation to the respective retinal area stimulated. Implementation of the mfS into the RVA setup, so that no time is lost due to fixation uptake following mfS is required to take the transient nature of this perfusion change into consideration.
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