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Dark adaptation in relation to choroidal thickness in healthy young subjects: a cross-sectional, observational study.

Munch IC, Altuntas C, Li XQ, Jackson GR, Klefter ON, Larsen M - BMC Ophthalmol (2016)

Bottom Line: 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).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.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, Zealand University Hospital, Sygehusvej 10, DK-4000, Roskilde, Denmark. icm@dadlnet.dk.

ABSTRACT

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.

No MeSH data available.


Dark adaptation curve from a 25-year-old female participant with a choroidal thickness of 310 μm. At time 0 the retina was partially bleached with a white photoflash (0.25 ms duration, 6.38 log scotopic Trolands-second). The dark adaptation curve does not exhibit the initial exponential part of the cone adaptation as the cone adaptation was fast and the retina not fully bleached. The recovery time to reach the pre-specified sensitivity threshold of 3 log units was 6.9 min. The rod adaptation rate was 0.37 log units/min as estimated from the slope of the second part of the curve, which represents the rod-mediated dark adaptation
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Fig1: Dark adaptation curve from a 25-year-old female participant with a choroidal thickness of 310 μm. At time 0 the retina was partially bleached with a white photoflash (0.25 ms duration, 6.38 log scotopic Trolands-second). The dark adaptation curve does not exhibit the initial exponential part of the cone adaptation as the cone adaptation was fast and the retina not fully bleached. The recovery time to reach the pre-specified sensitivity threshold of 3 log units was 6.9 min. The rod adaptation rate was 0.37 log units/min as estimated from the slope of the second part of the curve, which represents the rod-mediated dark adaptation

Mentions: Dark adaptation curves were modeled using the SAS software package (version 9.1, SAS Institute, Cary, NC, USA). A single-exponential, single-linear model was used as previously described [15] with the initial exponential part of the curve corresponding to cone-mediated dark adaptation and the linear part of the curve corresponding to the initial part of rod-mediated dark adaptation (Fig. 1). The rod adaptation rate was estimated by the slope of the linear part of the model. The rod intercept was calculated as the intercept between the linear part of the dark adaptation curve and the pre-defined sensitivity threshold of 5.00 × 10−3 cd/m2 corresponding to 3.0 log units. The adaptometer was set to terminate the test after 20 min, or sooner, if the predefined threshold had been reached. Consequently, the test was not designed to determine final rod threshold. All measurements were performed during daytime between 9am to 4pm.Fig. 1


Dark adaptation in relation to choroidal thickness in healthy young subjects: a cross-sectional, observational study.

Munch IC, Altuntas C, Li XQ, Jackson GR, Klefter ON, Larsen M - BMC Ophthalmol (2016)

Dark adaptation curve from a 25-year-old female participant with a choroidal thickness of 310 μm. At time 0 the retina was partially bleached with a white photoflash (0.25 ms duration, 6.38 log scotopic Trolands-second). The dark adaptation curve does not exhibit the initial exponential part of the cone adaptation as the cone adaptation was fast and the retina not fully bleached. The recovery time to reach the pre-specified sensitivity threshold of 3 log units was 6.9 min. The rod adaptation rate was 0.37 log units/min as estimated from the slope of the second part of the curve, which represents the rod-mediated dark adaptation
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4940899&req=5

Fig1: Dark adaptation curve from a 25-year-old female participant with a choroidal thickness of 310 μm. At time 0 the retina was partially bleached with a white photoflash (0.25 ms duration, 6.38 log scotopic Trolands-second). The dark adaptation curve does not exhibit the initial exponential part of the cone adaptation as the cone adaptation was fast and the retina not fully bleached. The recovery time to reach the pre-specified sensitivity threshold of 3 log units was 6.9 min. The rod adaptation rate was 0.37 log units/min as estimated from the slope of the second part of the curve, which represents the rod-mediated dark adaptation
Mentions: Dark adaptation curves were modeled using the SAS software package (version 9.1, SAS Institute, Cary, NC, USA). A single-exponential, single-linear model was used as previously described [15] with the initial exponential part of the curve corresponding to cone-mediated dark adaptation and the linear part of the curve corresponding to the initial part of rod-mediated dark adaptation (Fig. 1). The rod adaptation rate was estimated by the slope of the linear part of the model. The rod intercept was calculated as the intercept between the linear part of the dark adaptation curve and the pre-defined sensitivity threshold of 5.00 × 10−3 cd/m2 corresponding to 3.0 log units. The adaptometer was set to terminate the test after 20 min, or sooner, if the predefined threshold had been reached. Consequently, the test was not designed to determine final rod threshold. All measurements were performed during daytime between 9am to 4pm.Fig. 1

Bottom Line: 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).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.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, Zealand University Hospital, Sygehusvej 10, DK-4000, Roskilde, Denmark. icm@dadlnet.dk.

ABSTRACT

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.

No MeSH data available.