Table 2.

Data extraction variables

Article information	Study design	Sample details	Caffeine details	Pupil size measurement details
Title of paper	Description of design	Sample size	Self-reported daily caffeine intake	Design
Authors of paper	Type of study	Number of study groups	Prior caffeine intake control reported?	Pupil size measurement method
DOI	Blinding method	If patient group included, describe condition	Abstinence	Pupil size measurement method performance characteristics
PubMed ID	Within- or between-subjects design	If patient group included, describe diagnostic method	Abstinence duration	Stimulus characteristics
Journal	Time-of-day of study controlled?	Number of female participants per group	Caffeine concentration measured	Main pupil size measure
Publication year	Time-of-day control method	Number of male participants per group	Any further details on caffeine intake control method	General statistical strategy
Funding reported?	Measured outcomes	Mean or median age per group	Caffeine dosing	Report of pupil size values
Funders		Age range per group	Caffeine dose	Report of effect size
		Inclusion criteria per group	Method of administration	Pupil size values
		Exclusion criteria per group	Administration details	Effect size values
		Descriptive variables of sample per group	Type of control	p values of any statistical tests
			Description of placebo, if included