Melanopsin is a photopigment allowing a small subset of

retinal ganglion cells to absorb light energy directly and fire

action potential with or without synaptic input form rods and

cones. Intrinsic photo response of melanopsin-containing

retinal ganglion cells (MGCs) provides sustained irradiance

coding for non-visual photoperception functions including

circadian photoentrainment and the pupillary light response.

A sustained pupil constriction can be observed after the

offset of a bright blue light stimulus. This post-illumination

pupil response (PIPR) is produced by MGC, and can be

measured by chromatic pupillometry. Measuring PIPR holds

promise as a novel tool to assess MGC function. Current

testing protocols use central-field stimulation and require a

very bright light of long duration which can be difficult for

some subjects. We test the hypothesis that a consistent

PIPR can be induced with full-field blue light stimuli of

shorter duration and lower intensity than with central-field

stimulation.

IntroductionIntroduction

Apparatus:

•Full-field and central-field light stimulation were presented

with a Colordome® Ganzfeld bowl originally designed for

ERG testing.

•Pupillary light response was monitored with a video based

eye tracker at 60Hz.

MethodsMethods

Experimental Conditions (cont.):

For each of the intensity and duration steps, a red flash was

presented first followed by a blue flash 45 s after the offset of

the red flash. Participants were provided with a short break at

45 s after the offset of the blue flash to allow the pupil size to

return to baseline and to prevent fatigue.

Measurement and Data Analysis:

Pupil size data were normalized to baseline calculated from

the mean pupil size during a 1 s period before the onset of

each stimulus.

Primary Outcome Measure

PIPR: mean of the normalized pupil size over a 20 s period

from 10-30s after the offset of light stimuli (smaller number

means greater pupil constriction).

• 400 cd/m2, full-field blue stimulus induced significantly

larger PIPR than central-field blue stimulus of the same

intensity.

• PIPR to red flashes did not differ significantly full-field vs.

central-field.

• No further increase in PIPR was observed when the

duration increased from 400-1000 ms.

• 400-1000 ms, 400 cd/m2 blue full-field stimuli induced

significantly greater PIPR than 1000 ms blue central-field

stimulus of the same duration.

• Full-field stimulation is more effective that central-field

stimulation in inducing PIPR, suggesting that PIPR is a

function of stimulus intensity, duration and area.

• This study is the first to demonstrate that saturating PIPR

up to 30 seconds post illumination can be induced in vivo

with a strong blue flash lasting only a few hundred

milliseconds.

• This updated understanding of the relation between PIPR

and stimulus intensity, duration and area will allow

investigators to tailor their PIPR testing paradigm to target

a specific research question, and greatly facilitate the

development of a convenient and comfortable technique to

assess MGCs function for emerging clinical use.

shao-bo.lei@sickkids.ca

ConclusionsConclusions

Contact InformationContact Information

FullFull--Field Field ChChroromamatictic Pupillometry in the Assessment of the PostPupillometry in the Assessment of the Post--Illumination Pupil ResponseIllumination Pupil Response

Driven by MelanopsinDriven by Melanopsin--Containing Retinal Ganglion CellsContaining Retinal Ganglion Cells

1Shaobo Lei, 1,2H.C. Goltz, 1M. Chandrakumar, 1,2,3A.M.F. Wong

1Program in Neuroscience & Mental Health, Hospital for Sick Children; Department of Ophthalmology and Vision Sciences, 2University of Toronto & 3Hospital for Sick Children, Toronto Canada

No.4110 - A0098

Session: 413

Participants:

•10 visually-normal adult subjects (mean age: 31 years,

range 22 – 56), only right eyes were stimulated and

recorded, left eyes were patched during recording.

Experimental Conditions:

Experiment 1 (intensity trials): After 10 min dark adaptation,

PIPR was induced with alternating red (640±10 nm) and

blue (467±17 nm), 1-second full-field stimuli of increasing

intensity from 0.1 to 400 cd/m2 (11 steps) . For comparison

with a previously published protocol, a 60°×90° central-field

blue stimulus at 400 cd/m2 was also presented for 1 second.

Experiment 2 (duration trials): 10 min dark adaptation, 100

cd/m2 and 400 cd/m2, red and blue full-field stimulations of

increasing duration from 4-1000 ms were presented

alternately. 100 cd/m2 and 400 cd/m2 trials were conducted

on different days.

* Mean (n=10) normalized post-illumination pupil response (PIPR) tracings in response to 1 s stimulation of varying intensity from 10 visually-normal participants.

• PIPR to full-field blue stimulation increased monotonically

with increasing stimulus intensity.

• Red light (internal reference) induced no or minimal PIPR

at all intensity level.

Results: Results: Experiment 1 (intensity Experiment 1 (intensity trials)trials)

* Comparison of PIPR induced using 400 cd/m2 central-field stimuli (dashed line) vs 100-400 cd/m2 full-field stimuli (solid lines)

• PIPR in response to 400 cd/m2 increased as the duration of

stimulus increased from 4-200 ms.

* Mean PIPR to 100 cd/m2 and

400 cd/m2 full-field stimulation

of varying duration from 10

visually-normal observers.

Results: Results: Experiment 2 (duration trials)Experiment 2 (duration trials)

* comparison of PIPR to full-field blue stimuli of 400 cd/m2 intensity of the 6 longest duration steps (100, 200, 400, 600, 800, and 1000 ms.

*Authors have no commercial interest to disclose.

Statistic Analysis

One-way ANOVA with post hoc corrected for pairwise

multiple comparisons using the Tukey–Kramer method.

Full-Field vs. Central-field Stimulation

* Intensity-response function of PIPR to full-field stimulation vs. PIPR to 1s, 400 cd/m2 central-field stimuli

* Duration-response function of PIPR to full-field stimulation vs. PIPR to 1s, 400 cd/m2 central-field stimuli