Intrinsically photosensitive retinal ganglion cell function in relation to age: A pupillometric study in humans with special reference to the age-related optic properties of the lens

Table 2 Pupil responses to blue (470 nm) light and their correlations to lens transmission

Parameter	Stimulus intensity cd/m ²	Mean	95% CI	Correlation to age			Correlation to lens transmission
Parameter	Stimulus intensity cd/m ²	Mean	95% CI	b	R ²	p value	b	R ²	p value
LIGHT ON PARAMETERS
Maximal CA, %	3	41.7	38.2–45.1	0.21	0.09	0.18	–0.17	0.08	0.34
	30	48.4	46.0–50.9	0.19	0.07	0.10	–0.15	0.06	0.23
	100	51.8	49.5–54.0	0.10	0.04	0.33	–0.02	0.01	0.89
	300	55.3	53.4–57.3	0.16	0.09	0.07	–0.07	0.05	0.44
Sustained CA, %	3	33.3	29.9–36.7	0.30	0.14	0.048*	–0.21	0.09	0.22
	30	44.6	42.4–46.9	0.17	0.10	0.09	–0.13	0.07	0.25
	100	49.7	47.6–51.8	0.19	0.12	0.043*	–0.12	0.06	0.22
	300	52.5	50.4–54.5	0.23	0.15	0.014*	–0.20	0.11	0.06
LIGHT OFF PARAMETERS
Early post-stim. AUC	1.5	1.3–1.7	0.02	0.15	0.016*	–0.01	0.06	0.21
	30	2.1	1.9–2.2	0.01	0.08	0.09	–0.004	0.02	0.63
	100	2.6	2.4–2.8	0.02	0.19	0.005*	–0.01	0.08	0.22
	300	3.1	2.9–3.3	0.03	0.29	0.0003*	–0.03	0.18	0.02*
Late post-stim. AUC	3	0.8	0.6–1.0	0.01	0.05	0.20	–0.002	0.02	0.88
	30	1.2	0.9–1.5	0.008	0.04	0.56	0.009	0.04	0.60
	100	1.8	1.4–2.3	0.02	0.05	0.30	0.009	0.06	0.69
	300	2.8	2.4–3.3	0.04	0.08	0.07	–0.03	0.04	0.29

Each pupil response parameter is given as mean and its 95% confidence interval.
Correlations between pupil responses and age and between responses and lens transmission were calculated with adjustment for baseline pupil size and gender using a multiple linear regression model. Results are given as: b, the slope of the regression (response change per transmission unit), R², the correlation coefficient, i.e., the fraction of variance explained by the regression model and the p-value.
For abbreviations and definitions of parameters, see Table 1 and Methods.
Blue (470 nm) light stimulus luminance of 300 cd/m² corresponded to photon flux irradiance of 14.8 log photons/cm²/s.
* Level of significance p < 0.05. CI, confidence interval; b, slope of the regression; R², correlation coefficient; CA, contraction amplitude; AUC, area under the curve.

ISSN: 1471-2415