Dark adaptation in relation to choroidal thickness in healthy young subjects: a cross-sectional, observational study.
BACKGROUND
Dark adaptation is an energy-requiring process in the outer retina nourished by the profusely perfused choroid. We hypothesized that variations in choroidal thickness might affect the rate of dark adaptation.


METHOD
Cross-sectional, observational study of 42 healthy university students (mean age 25 ± 2.0 years, 29 % men) who were examined using an abbreviated automated dark adaptometry protocol with a 2° diameter stimulus centered 5° above the point of fixation. The early, linear part of the rod-mediated dark adaptation curve was analyzed to extract the time required to reach a sensitivity of 5.0 × 10(-3) cd/m2 (time to rod intercept) and the slope (rod adaptation rate). The choroid was imaged using enhanced-depth imaging spectral-domain optical coherence tomography (EDI-OCT).


RESULTS
The time to the rod intercept was 7.3 ± 0.94 (range 5.1 - 10.2) min. Choroidal thickness 2.5° above the fovea was 348 ± 104 (range 153-534) μm. There was no significant correlation between any of the two measures of rod-mediated dark adaptation and choroidal thickness (time to rod intercept versus choroidal thickness 0.072 (CI95 -0.23 to 0.38) min/100 μm, P = 0.64, adjusted for age and sex). There was no association between the time-to-rod-intercept or the dark adaptation rate and axial length, refraction, gender or age.


CONCLUSION
Choroidal thickness, refraction and ocular axial length had no detectable effect on rod-mediated dark adaptation in healthy young subjects. Our results do not support that variations in dark adaptation can be attributed to variations in choroidal thickness.
['Munch|Inger Christine|IC|http://orcid.org/0000-0002-0515-5736', 'Altuntas|Cigdem|C|', 'Li|Xiao Qiang|XQ|', 'Jackson|Gregory R|GR|', 'Klefter|Oliver Niels|ON|', 'Larsen|Michael|M|']
D000328:Adult D000367:Age Factors D058452:Axial Length, Eye D001794:Blood Pressure D002829:Choroid D003430:Cross-Sectional Studies D003623:Dark Adaptation D005260:Female D006801:Humans D008297:Male D012029:Refraction, Ocular D017948:Retinal Rod Photoreceptor Cells D012684:Sensory Thresholds D012737:Sex Factors D013997:Time Factors D041623:Tomography, Optical Coherence D014792:Visual Acuity D055815:Young Adult
dark adaptation Choroidal thickness EDI-OCT time-to-rod-intercept enhanced-depth optical coherence tomography