Constant luminance (cd·s/m2) versus constant retinal illuminance (Td·s) stimulation in flicker ERGs

Abstract

PurposeTo compare the effect of variable pupil size on the flicker electroretinogram (ERG) between a stimulus having constant luminance and a stimulus having constant retinal illuminance (constant Troland) that compensates for pupil size.MethodsSubjects (n = 18) were tested with 12 pairs of the stimuli. The stimulus pair consisted of the ISCEV standard constant luminance stimulus (3 cd·s/m2 with a 30 cd/m2 background) and a constant retinal illuminance stimulus (32 Td·s with a 320 Td background) selected to provide the same stimulus and background when the pupil diameter is 3.7 mm. Half the subjects were artificially dilated, and their response was measured before and during the dilation. The natural pupil group was used to assess intra- and inter-subject variability. The artificially dilated group was used to measure the flicker ERG’s dependence on pupil size.ResultsWith natural pupils, intra-subject variability was lower with the constant Troland stimulus, while inter-subject variability was similar between stimuli. During pupil dilation, the constant Troland stimulus did not have a dependence on pupil size up to 6.3 mm and had slightly larger amplitudes with longer implicit times for fully dilated pupils. For the constant luminance stimulus, waveform amplitudes varied by 22% per mm change in pupil diameter, or by 48% over the 2.2 mm diameter range measured in dilated pupil size. There was no difference in inter-subject variability between constant Troland natural pupils and the same subjects with a constant luminance stimulus when dilated (i.e., the ISCEV standard condition).ConclusionsThese results suggest that a constant Troland flicker ERG test with natural pupils may be advantageous in clinical testing. Because of its insensitivity to pupil size, constant Troland stimuli should produce smaller reference ranges, which in turn should improve the sensitivity for detection of abnormalities and for monitoring changes. In addition, the test can be administered more efficiently as it does not require artificial dilation.Clinical Trial registration number This trial is registered at ClinicalTrials.gov (NCT02466607).

Factors Affecting Mydriasis-Free Flicker ERGs Recorded With Real-Time Correction for Retinal Illuminance: Study of 150 Young Healthy Subjects

“…The components of the RETeval system have been described in detail. [16][17][18][19][20][21][22][23] In brief, full-field stimuli are presented with a 60-mm diameter dome, and the white stimuli are created by a combination of three colored light emitting diodes. The frequency of the flicker stimulus was 28.306 Hz, and the pulse duration was less than 1 msec.…”

“…A full-field flicker ERG recording system called the RETeval system was recently developed. [16][17][18][19][20][21] This system is comprised of a small, hand-held Ganzfeld dome used with a special single-use, skin electrode array. This system can record flicker ERGs without mydriasis because the device delivers stimulus flashes with constant retinal illuminance (Td-s) by adjusting the luminance (cd-s/m 2 ) to compensate for changes in the pupillary area (mm 2 ) in real time.…”

Pupil Size Estimation Based on Spatially Weighted Corneal Flux Density

“…In some ophthalmological clinical testing, pupil size could have significant effects on the indicators like the flicker electroretinograms [7], [8]. In visual perceptual experiments, pupil size could be an important control parameter which needs to be considered to get a constant troland value [9], [10]. Besides, pupil size affects many performances in near-eye displays such as Maxwellian view optical systems, light field systems [11].…”

Artificial iris performance for smart contact lens vision correction applications

“…Table 1 shows the luminance values and corresponding healthy pupil diameters from 6 to 2 mm. Additionally, the calculation of the estimated retinal illuminance (in Troland [cd/m 2 × mm 2 ]) 37 for: a healthy eye, an aniridia eye with big pupil and an aniridia eye with a GH-LCD active light filter (transmission profile: 65%-pupil center and 32%-pupil periphery) are presented. On one hand, it is noted that the retinal illuminance of the aniridia eye is higher due to the lacking of iris protection, when compared to the healthy eye.…”