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ISCEV Standard Protocols for the Espion Ophthalmic Electrodiagnostic System

Your Espion System is shipped pre-programmed with protocols that make it easy to perform ISCEV standard ERG and VEP testing quickly and ac-curately right out of the box. Using these protocols is as easy as 1,2,3.

To access these protocols, touch START

Select a patient

Then press Protocols...

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To organize your protocols, press Category Filter

Note that VEP protocols are organized by stimulus type: flash, alternating flicker, or onset flicker.

ERG protocols are organized as LIGHT (photopic) or DARK (scotopic). Separating light and dark protocols makes it easy to test both eyes monocularly in the same state of adaptation.

Press ISCEV LIGHT ERG

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Like most of the protocol categories, ISCEV LIGHT ERG contains three protocols: one for each eye, and one for both eyes. The “OS” and “OD” protocols are monocular protocols designed primarily for the ColorBurst hand-held Ganzfeld. These protocols assign the referenced eye to channel 1. The “Both” protocol is intended for use when both eyes will be stimulated simultane-ously, as with a desktop Ganzfeld, and accordingly it provides one test step for each condition. This protocol assigns OD to channel 1 and OS to channel 2.

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The Dark Adapted ERG Protocol (p. 7)

The Light Adapted ERG Protocol

(p. 25)

The following pages completely document both the dark adapted and light adapted ERG protocols for the Espion system, showing in detail how each protocol complies with every aspect of the relevant ISCEV standard. Only the right eye protocol is explained in detail; the left eye protocol is identical except for “eye tested” entries.

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The Dark-Adapted Protocol

This is the home page of the protocol creation area. Here, selections can be made to set up the choices available during the creation or modification of the protocol. The first selection is Test Type. Each Espion protocols is classified as ERG, VEP, or Combined ERG/VEP. Each test type configures the protocol setup pages which follow to offer a different set of parameter choices. The dark-adapted response test type is ERG. The second choice is Stimulus Generator. This list automatically includes all of the stimulators that came with or have been added to your Espion system. In this protocol, the stimulus generator is the ColorBurst hand-held Ganzfeld. The last choice is the number of channels (Total Channels) the protocol will use. The present proto-col will use two channels which share the raw digital data coming in from a single physical connec-tion to the eye. Channel 1 will filter the data in one way to present the ERG waveform, while Chan-nel 2, when invoked, will filter it simultaneously in a different way to display the oscillatory poten-tial. This protocol is stored under the category ISCEV DARK ERG and has been given the name ISCEV Standard ERG OD Dark Rev 4.

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The Test page contains parameters that determine the overall course of the test, and some options that control the default appearance of the testing screen and printed reports. The comments offered here are necessarily brief; for detailed explanations of all options, consult the Espion manual. The ISCEV recommended dark adaptation time for this test is 20 minutes. Entering this number in the Adaptation Time box as shown will cause a twenty minute timer to commence upon entering the protocol. This timer may be overridden if necessary, but it requires positive user action to do so. Option Code is always zero unless custom testing modules have been provided by Diagnosys. Because Step Sequencing is manual in this protocol, Trial Interleaving has no meaning and is grayed out. Save Trials is checked so that all trials that make up an averaged result will be separately saved along with the result. Normals are not displayed because they must first be developed by the user. For help in doing this, contact Diagnosys. The default screen layout is chosen as Tile so flash responses and their OPs will be displayed side-by-side. .

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The Table is displayed so marker values can be read onscreen, and Cycle Colors is chosen so each new waveform will be displayed in a different color. Printer options were chosen to generate a complete report on a single page in landscape format.

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STEP 1: The Dark-Adapted Rod Response

The first step in the dark adapted ERG is the Rod Response. An abbreviation of the step name is en-tered in the Step Description window under the red bracketed [1] which indicates the step number. There is one marker for this test. The ISCEV standard suggests two results be taken for each condi-tion, so 2 is entered in the Results Per Run box. This setting means that two results will be taken automatically when the RUN button is pressed after entering the protocol. The second result will automatically start after the first result is complete, and after the Time Between Results interval has elapsed. After the number entered in Results Per Run have been acquired, no more results will be taken automatically, but more can be taken manually if desired. The standard suggests that flashes be presented at least two seconds apart, so this value is entered in the Time Between Results box. There is no adaptation time for this step because dark adaptation for the entire test has been allowed for on the main page. Clip Region lets the user specify a sub-region of the waveform located between two time markers. This does not affect the waveform as displayed on screen, however only the region of the waveform lying between the markers will be printed on the report. Here these boxes contain the default zeroes, so the entire waveform will be printed. The check in “Display Text…” will cause the text in the box to the right to pop up when RUN is first pressed after entering this protocol step. The text can be modified to include whatever runtime re-minders are desired.

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The Ganzfeld stimulator has been set up to deliver a white stimulus flash with a metameric color temperature of 6500ºK at an energy of 0.006 cd-sec/m2. This is 2.5 units beneath the standard flash, as prescribed by the standard. The fixation point has been set to a dim value comfortable to a dark-adapted patient and positioned for relaxed viewing by the right eye.

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The acquisition has been set up in Manual Rejection Mode to average four Trials Per Result to form each displayed waveform. In Manual Rejection Mode, a trial is started by pressing RUN. The stimulus flashes and the result-ing waveform is displayed onscreen. A pop-up window then stops the system and asks the user to accept or reject the trial. There is no time pressure for this decision. If the trial is accepted or rejected before the Inter-trial delay time has elapsed, the system will wait until it has before triggering the next trial; if not, the system will start the next trial as soon as the choice is made. When a total of four trials has been accepted, the result is displayed, and, because Results per Run has been set to two (previous page), a second result is started after the Time Between Results interval has elapsed. In-ter-trial delay and Time Between Results are both set to 2 seconds to ensure that flashes are pre-sented no closer than 2 seconds apart, as the standard requires. Baseline Removal has been checked to remove any linear baseline drift which might occur in each trial. Autozero has been checked to re-center the trace before each trial. Beginning at the Start pre-trigger and lasting throughout the Range, an average signal value is calculated that will be used as the zero voltage point for re-centering the trace and for establishing the default zero voltage for cur-sor reference.

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Only Channel 1 is used in the dark-adapted rod response. Channel 2 is defined for later use but is not enabled in this step. A default Y-axis Scaling of 50�V/division has been found to be generally best, but this can be changed at run-time without referring back to or affecting the protocol. Trial divide is a factor by which trials are divided when displayed onscreen together with averaged results. Averages containing many trials may be much smaller than the individual trials because they contain less noise. The Trial divide scaling factor lets both coexist on the same screen. Here the av-erage contains only four trials, so a scaling factor of one is appropriate. The ISCEV standard recommends that the waveform include at least the range of frequencies from 0.3 to 300 Hz. The default parameters of 0.15 to 300 Hz were chosen because waveforms acquired under these conditions best match samples shown in the standard and in published literature, but the unit is capable of showing a much wider bandwidth ( 0—1000 Hz) if desired. The default setting of the Line filter is off because this filter is normally not necessary. It may be invoked at run time if needed, but should be used with caution, since excessive line noise is often a symptom of abnormally high electrode impedance or other problems which could distort the signal. Also, even the best digital notch filters such as the Espion employs distort the phase of frequencies near the line frequency (that’s how they work), so they should be avoided unless needed. The Gain setting is a scale resolution setting only and has nothing to do with the actual analog ampli-fier gain. It should be left at the default setting of one for standard ERG protocols.

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Only one marker, B wave peak, is used on the dark adapted rod response. This page defines that marker. Both period and amplitude are enabled, meaning both numbers will be displayed adjacent the marker name B in the table. Relative boxes are not ticked, so the marker value will be calculated from the default time and amplitude zeros. The default time zero is the center of the stimulus flash. The de-fault amplitude is the average amplitude measured during the window beginning at the Start pretrig-ger point and ending after an amount of time equal to the Start pretrigger range (page 8). This marker applies only to channel 1, so the Apply Channel 1 button is checked while the Apply Channel 2 button is x’ed out. (A bug in the graying feature that applies only to these two buttons prevents this from being shown correctly in this view).

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STEP 2: The Dark Adapted Maximal Response

The dark adapted maximal response and the dark OPs will be obtained and displayed simultaneously in this protocol. This will require a total of 4 markers: the A and B wave for the maximal response, and the OP Peak and OP Trough for the oscillatory potential. The standard recommends a ten second interval between dark adapted maximal response flashes, but a 15 second interval between OPs. The longer interval, 15, is therefore entered in Time Between Re-sults. Also, the standard recommends that the first OP be discarded. The user is prompted to do so by the Display Text at Start of Step popup. Dark adaptation has already taken place so the Adaptation time is zero. The Clip Region is again not set up because the whole waveform should be printed. The stimulator is programmed to deliver one standard flash (2.25 cd-sec/m2) for each trial with no background. The fixation point is as it was for the rod response.

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Acquisition is set up as for the rod response, except that now both Time Between Results and Inter-trial delay have been set to 15 seconds to comply with the minimum time between dark-adapted OP flashes recommended by the ISCEV standard.

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Channel 1 is set up exactly as before on page 9.

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Channel 2 will display the OP and is set up as a Virtual Channel with Input from channel 1. Filter-ing is 100-300 Hz as recommended by the standard. Care should be taken; the Low Filter legend in the parameter table means “low frequency filter” but is technically called the high pass filter, and conversely. Y Axis Scaling is set at 10 �V to better display the small OP waveform.

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Four markers are set up in the marker section: an A and B wave marker for channel 1, and OP Peak and OP Trough markers for channel 2. This page sets the A wave marker to be automatically placed at the most Negative Peak occurring between the stimulus flash (Minimum 0 ms) and a Range of 25 ms following the flash. Because the Relative buttons are not checked, the table will report the marker’s position relative to time zero of the flash, and to the voltage equal to the average input voltage during the 20 msec preceding the flash (autozero pre-trigger and range). The Apply Channel button number one is pressed, applying this marker to Channel 1, but Channel 2 is not, so the marker will not be applied to channel 2. The graying bug which applies only to these two buttons once again prevents this from being shown.

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This page sets up the B-wave marker. Timing is, like the A marker, relative to the stimulus flash, but Amplitude is reported Relative to the A marker. The Placement section indicates that the marker will be placed at the most positive peak between 25 and 45 msec after the flash. As in the previous step, the Apply Channel button has been checked applying this marker to channel 1.

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The OPs are quantified with two markers, OP Peak and OP Trough, placed respectively at the high-est and lowest points in the first 25 msec of the OP after the flash. This page defines OP Peak, in which period is relative to the flash, but Amplitude is Relative to the Trough OP marker. This marker is assigned to channel 2, but as before that is not visible when the buttons are grayed out.

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This page defines the Trough OP marker, which is placed in time relative to the flash, and in Ampli-tude Relative to the average voltage measured in the 20 milliseconds preceding the flash (the Rela-tive button is x’ed, not checked). As before, this marker applies to channel 2 only, but that can not be seen on this page. This is the final page of the Dark Adapted OD Protocol. The Dark adapted OS Protocol is identical except that everywhere OD is replaced by OS. Other Dark Adapted Protocols The “Both” dark adapted protocols uses identical stimulator, amplifier and acquisition settings, but is set up so OD data is taken from Channel 1 and OS data from Channel 2. Channel 3 is set up virtual to Channel 1 to display OD OPs, and Channel 4 is set up virtual to Channel 2 to display OS OPs. The “Both” protocol assumes both eyes will be stimulated simultaneously and therefore displays all channels at once, with one step per condition. This protocol is not intended for use with the Color-Burst hand-held Ganzfeld.

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The Light Adapted Protocol

This is the home page of the ISCEV standard light-adapted OD protocol. Like the dark-adapted response, the light adapted response Test Type is ERG. The Stimulus Generator is the ColorBurst hand-held Ganzfeld. Two channels are used, even though only one will be physically connected to the eye. The second channel will process unfiltered digital data from channel one to display the oscillatory potential in the first step. This protocol is stored under the category ISCEV LIGHT ERG and bears the name shown in the description field.

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The ISCEV recommended light Adaptation time for this test is 10 minutes. Entering this number in the box as shown will cause a ten-minute timer to commence upon entering the protocol. This timer may be overridden if necessary, but it requires positive user action to do so. Option code is always zero unless custom testing modules have been provided by Diagnosys. Because Step sequencing is manual in this protocol, trial interleaving has no meaning and is grayed out. Save Trials is checked so that all trials that make up an averaged result will be saved with the result. Normals are not displayed because they must first be developed by the user. For help in doing this, contact Diagnosys. The default screen layout is chosen as Tile so flash responses and their OPs can be displayed side by side. The Table is displayed so marker values can be read onscreen, and cycle colors is chosen so each new waveform will be displayed in a different color. Printer options were chosen so a complete report will be printed on a single page in landscape format.

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This is the base setup page for the light-adapted cone response protocol. Four markers will be used for this test: A and B wave for the ERG, and OP Peak and OP Trough for the OPs. The ISCEV standard suggests two results be taken for each condition, so 2 is entered in the Results Per Run box. More can be taken at run time if desired. The standard suggests that cone flash stimuli be presented at least 0.5 seconds apart, however, the light adapted oscillatory potential, which uses the same stimulus, is measured simultaneously, and the standard suggests light adapted OPs be spaced at least 1.5 seconds apart. For that reason the value 2 is entered in the Time Between Results box. There is no adaptation time for this step because dark adaptation for the entire test series has been allowed for on the main page. Clip Region lets the user specify a sub-region of the waveform located between two time markers. The entire waveform is displayed on screen, but only the region lying between the markers is printed on the report. Here these boxes are left at the default zeroes, so the entire waveform will be printed. The tick in Display Text… will cause the text in the box to the right to pop up upon first pressing RUN after entering this protocol step. The text can be modified to include whatever reminders are desired. The Ganzfeld stimulator has been set up to deliver a white stimulus flash with a metameric color temperature of 6500ºK at an energy of 1 ISCEV Standard Flash, or 2.25 cd-sec/m2, on a steady 6500ºK white background at 25.5 cd/m2. The fixation point has been set to a value comfortable to a light-adapted patient and positioned for comfortable viewing by the right eye.

STEP 1: The Single Flash Cone Response

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The acquisition has been set up in manual rejection mode (see page 8) to average four trials to form each displayed waveform. In this mode, the stimulus flashes and the resulting waveform is displayed onscreen. A pop-up window asks the user to accept or reject the trial. When a total of four trials has been accepted, the result is displayed, and, because “Results per Run” has been set to two, a second result is immediately started. The “Inter trial delay” and “Time Between Results” are both set to en-sure that flashes are presented no closer than 2 seconds apart, (the standard requires at least 1.5). The acquisition has been set up to remove any linear baseline drift which might occur in each trial, and to autozero, or re-center the trace before each trial. Beginning at the autozero pretrigger and last-ing throughout the autozero range, an average signal value is calculated that will be used as the zero voltage point for re-centering the trace and for establishing a default zero voltage for cursor refer-ence.

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Two channels are used. Channel 1, here named LtAdSglFlash (Light Adapted Single Flash) records the light-adapted cone response, and Channel 2, set up virtual to Channel 1, records the Ops (see next page). A default scaling of 20�V/division has been found to be generally best for the light adapted response, but this can be changed at run-time without referring to or affecting the protocol. Trial divide is set to 1 as before. The standard recommends that the waveform include at least the range from 0.3 to 300 Hz. The de-fault parameters of 0.15 to 300 Hz were chosen because waveforms acquired under these conditions best match samples shown in the standard and in published literature, but the unit is capable of show-ing a much wider bandwidth ( 0—1000 Hz) if desired. The default line filter setting is off because this filter is normally not necessary. It may be invoked at run time if necessary, but should be used with caution, since line noise is often a symptom of abnor-mally high electrode impedance or other problems. As before, the Gain setting should be left at 1 (see page 9).

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Channel 2, here named LtAdOP (LightAdapted OP) will display the OP and is set up as a Virtual Channel with Input from channel 1. Filtering is 100-300 Hz as recommended by the standard. Scal-ing is set at 10 �V to better display the small OP waveform.

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As with the dark adapted maximal response, four markers are set up in the marker section: an A and B wave marker for channel 1, and OP Peak and OP Trough markers for channel 2. This page sets the A wave marker to be automatically placed at the most negative point occurring during the first 30 msec after the flash. The table will report the marker’s position relative to time zero of the flash, and to the voltage equal to the average input voltage during the 20 msec preceding the flash (autozero pre-trigger and range). The Apply Channel button number one is pressed, applying this marker to Channel 1, but the Chan-nel 2 button is not, so the marker will not be applied to Channel 2.

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This page sets up the B-wave marker. Timing is, like the A marker, relative to the stimulus flash, but Amplitude is reported relative to the A marker. The Placement section indicates that the marker will be placed at the most Positive Peak between 25 and 55 (25+30) ms after the flash. As in the previous step, the Apply Channel buttons have been set applying this marker only to Channel 1.

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The OPs are quantified with two markers, OP Peak and OP Trough, placed respectively at the high-est and lowest points in the first 25 ms of the OP after the flash. This page defines OP Peak, in which Period is relative to the flash, but Amplitude is Relative to the Trough OP marker. This marker is assigned to Channel 2.

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This page defines the Trough OP marker, which is placed in time relative to the flash, and in ampli-tude relative to the average voltage measured in the 20 milliseconds preceding the flash. Like the Peak OP marker, this marker applies only to Channel 2.

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This page starts the last step in the light-adapted ERG series protocol, the 30 Hz Flicker. Two markers will be defined, A and B. The ISCEV standard suggests two runs be taken on non-averaged waveforms. Though this test is av-eraged, it does not take long, and therefore 2 Results Per Run are specified. The standard does not specify a time between flicker tests, but a 15 second rest for the patient seems reasonable and is specified here in Time Between Results. As before, we wish to print the entire waveform and therefore no clip region is defined. The standard specifies a stimulus intensity of 1 standard flash, so the intensity is set as before to 2.25 cd-sec/m2. (The standard warns of stimulus intensity sag at high stimulus rates; this does not occur with the Espion system.) Background is set to the standard 25.5 cd/m2. The stimulus is set to flicker at precisely 30.3 Hz. This sat-isfies the standard, which suggests “approximately 30 stim-uli per second”, while avoiding synchronizing the stimulus to a line harmonic.

STEP 2: The 30 Hz Flicker Response

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The acquisition has been set up to average fifty Trials Per Result to form each displayed waveform. The ISCEV standard points out that the first few stimuli of the 30 Hz flicker will elicit flash re-sponses which should be ignored. The First Trial Delay is therefore set to 500 ms. (It is important to note that First Trial Delay does not work the same way for flicker settings as it does for single flash. In single flash mode, the flash is not produced until the First Trial Delay has elapsed. In flicker mode, the stimulus starts immediately, and is guaranteed to be on for at least the duration of the First Trial Delay before data acquisition starts.) Baseline Removal has been checked to remove any linear baseline drift which might occur in each trial. Autozero has been checked to re-center the trace before each trial. Beginning at the Start pre-trigger (20 ms prior to start of flicker) and lasting throughout the Range (here, until flickering be-gins), an average signal value is calculated that will be used as the zero voltage point for re-centering the trace and for establishing the default zero voltage for cursor reference. Sample frequency is left at the default rate of 1,000 Hz.

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Only Channel 1 is used in the flicker response. Channel 2 is not enabled in this step. A default Y-axis Scaling of 20�V/division has been found to be generally best for this test, but this can be changed at run-time without referring back to or affecting the protocol. Even though this is an average, the signals are large, so a Trial Divide of 1 is appropriate. Auto-rejection is Enabled and is set to reject voltages which exceed 95% of a window of 200�V. The Line filter is not enabled. The ISCEV standard recommends that the waveform include at least the range of frequencies from 0.3 to 300 Hz. This test is set up with a bandpass of 0.15-1,000 Hz The Gain is set to 1 as before.

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The flicker response is set up for two markers, A and B. This page sets the A wave marker to be automatically placed at the most Negative Peak occurring between the stimulus flash (Minimum 0 ms) and a Range of 40 ms following the flash. Because the Relative buttons are not checked, the table will report the marker’s position relative to time zero of the flash, and to the voltage equal to the average input voltage during the 20 msec preceding the flash (autozero pre-trigger and range). The Apply Channel button number one is pressed, applying this marker to channel 1, but channel 2 is not, so the marker will not be applied to channel 2. Since these buttons are not grayed out in this protocol the graying bug does not prevent this from being shown.

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This page sets up the B-wave marker. Timing is, like the A marker, relative to the stimulus flash, but Amplitude is reported Relative to the A marker. The Placement section indicates that the marker will be placed at the most positive peak between 25 and 45 msec after the flash. As in the previous step, the Apply Channel button has been checked applying this marker to channel 1. This is the final page of the Light Adapted OD Protocol. The Light adapted OS Protocol is identical except that everywhere OD is replaced by OS. Other Light Adapted Protocols The “Both” Light adapted protocol uses identical stimulator, amplifier and acquisition settings, but is set up so OD data is taken from Channel 1 and OS data from Channel 2. Channel 3 is set up virtual to Channel 1 to display OD OPs, and Channel 4 is set up virtual to Channel 2 to display OS OPs. The “Both” protocol assumes both eyes will be stimulated simultaneously and therefore displays all channels at once, with one step per condition. This protocol is not intended for use with the Color-Burst hand-held Ganzfeld.

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Notes on ISCEV Standard Test Procedures Dilation The standard recommends that pupils be dilated for all ERG recordings, and that pupil size be noted if it is less than maximal. Diagnosys provides an entry for pupil size for all normal patients, and rec-ommends pupil size be noted in all patients. Some versions of Espion software permit Ganzfeld light levels to be specified in Trolands if pupil size is entered on the stimulator setup page. Dark Adaptation The standard requires that patients be dark-adapted for at least 20 minutes prior to testing for the first two types of responses, and light adapted for at least 10 minutes prior to testing for the last two. These times are directly entered in the “Adaptation time” box on the “Test” page of each protocol—twenty minutes for dark adaptation, 10 for light. If the patient is already adapted, these times may be over-ridden by the user by suppressing a warning pop-up. Corneal Electrodes The standard recommends a corneal electrode as the active electrode for ERGs. Skin electrodes are strongly discouraged. Acceptable electrodes include bipolar corneal electrodes, such as the Gold-Lens, or fibre electrodes, such as the DTL. Diagnosys recommends the use of DTL thread electrodes for most standard ERG testing. These electrodes do not irritate the cornea and may be left in place for both dark and light adaptation. Reference Electrodes If a bipolar corneal electrode is not used, the standard suggests a reference skin electrode applied on the temple near the orbital rim, and a ground skin electrode applied to the forehead or ear. Reference and ground electrodes should have impedances of 5K or less measured with a low-current AC source at a frequency between 10 and 100 Hz. Diagnosys equipment measures these impedances at 30 Hz and displays them together onscreen for convenient reference. Fixation Lights Fixation lights are incorporated into Diagnosys Ganzfelds as recommended by the standard. They are positioned and given luminance appropriate to light level through setup entries in the “Stimulator” section of each protocol. Light Sources The standard suggests that instruments using LED light sources be calibrated both photopically and scotopically to ensure proper scotopic performance. Diagnosys stimulators containing LEDs are fully calibrated to both photopic and scotopic external standards, and maintain that calibration through use of highly stable internal light meters.

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Stimulus duration The standard requires flash stimuli have a duration of 5 ms or less. All Diagnosys flash stimuli have maximum duration of 4 ms. Stimulus wavelength Diagnosys standard ERG protocols employ white stimuli calibrated to a color temperature of 6500ºK. In addition, metameric colors may be produced and electronically modulated, but this is well beyond the scope of the basic standard, and these colors are not used in the furnished standard protocols. Stimulus Strength The “standard flash” is vaguely defined as a flash less than 5 msec in duration having a luminous energy of between 1.5 and 3.0 cd-sec/m2. Diagnosys equipment is calibrated to the maximum light transfer standard accuracy of ± 10%, with instrument-to-instrument precision considerably better than that, and is therefore capable of meeting a much tighter tolerance than the standard demands. For this reason the Diagnosys standard flash is defined as 2.25 cd-sec/m2. Background illumination The standard requires that the stimulator produce a steady, even background luminance of 17-34 cd-sec/m2. Diagnosys standard protocols define a 6500ºK white background at 25.5 cd-sec/m2. Light adjustment and calibration The standard recommends that the standard system be capable of attenuating flash strength 3 log units beneath the standard flash strength in steps no smaller than 0.3 log units. Diagnosys equip-ment can produce flash strengths up to 6.6 log units smaller than the standard flash, and up to 1.3 log units brighter. Resolution is high: anywhere within this range, light level may be changed by as little as 1% or less. Metameric wavelength of both flash and background are held constant across the entire range. Calibration The standard suggests that manufacturers document the stimulus strength of each flash using an integrating photometer, and background luminance using a non-integrating photometer, placed at the location of the eye. Diagnosys uses an International Light IL1700 research radiometer to cali-brate its stimulators as mandated. All stimulators are calibrated in both photopic and scotopic units. Diagnosys offers the same photometer for sale including an adaptor to couple the unit to the Ganzfeld. In addition, each unit is spectrally calibrated using a spectro-radiometer. Light output per flash of Diagnosys equipment does not vary with repetition rate, though power limits in the software may reduce the maximum flash intensity that can be programmed as repetition rate in-creases.

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Recalibration All Diagnosys stimulators are self calibrating: they request permission to calibrate whenever the user enters an associated protocol. Yearly calibration intervals are internationally mandated, but changes in Diagnosys Ganzfeld calibration are rarely seen at this interval. Because of the technology em-ployed, light output from the dome does not vary from changes in the light elements or their power source, and is unaffected by changes in bulbs or attenuation systems. The dome paint is durable and will not yellow, flake or wash off. The standard mentions stabilizing transformers. Like most modern equipment, the Espion system does not need these. Its internal power supply can maintain tight control over internal voltages when supplied with any standard line voltage and frequency available in any country of the world. Electronic recording equipment Amplification: ERG protocols are set by default to 0.15-300 Hz, though any filtering from DC to 1,000 Hz is avail-able. The standard suggests an input impedance of 10 million ohms: the Espion input impedance is 100 times greater at 1 billion ohms. Espion amplifiers may be AC coupled through digital filters, but even when DC coupled can handle any offset potential that can be produced by a safe biological electrode. Patient Isolation Diagnosys is an ISO 9001-46001/1 certified company. All Diagnosys photic stimulators are type BF double insulated products. Patient contacts are isolated to 2500V from line ground and 4000V from line potential, as required by the standards quoted below. Diagnosys products are not simply “designed to meet” these standards; they are exhaustively type-tested and proven to meet them by a third party standards organization (SEMKO) to meet the follow-ing standards: Safety EMC Emissions EN60601-1:1990,A2:1996 EN60601-1-2:1993 EN60601-2-26:1994 UL2601, 2nd Edition 1997 CAN/CSA C22.2 No.601-M90, SI:1995

Display of data and averaging The LCD screen can represent the full amplifier bandpass without attenuation. The default sample rate per channel is 1 KHz. Responses are displayed immediately, and a preview option can display incoming data in real time to aid in eliminating noise.