Assessing Diurnal Variation in Choroidal Thickness

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C O R R E S P O N D E N C E
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Assessing Diurnal Variation in Choroidal
Thickness
Milton C. Chew, MBBS; Louis W. Lim, MBBS; Kai Xiong Cheong, MBBS; SriniVas R. Sadda, MD;
Colin S.H. Tan, MBBS, MMed (Ophth), FRCSEd (Ophth)
To the Editor:
We read with interest the article by Toyokawa
et al1 describing the differences between morning
and evening choroidal thickness measurements in
Japanese subjects, which the authors concluded
could be attributed to diurnal variation. This study,
however, does not provide strong evidence for the
pattern of diurnal variation, because measurements
at only two time points do not provide compelling
evidence of a specific trend.
We would like to highlight three other studies in
healthy subjects that provide additional evidence to
support the presence and pattern of diurnal variation
in choroidal thickness. These studies measured
choroidal thickness over at least five time points
during a single day, allowing a more comprehensive
analysis of the trend and pattern of diurnal variation.2
In a study of 12 healthy individuals, Tan et
al3 performed sequential spectral-domain optical
coherence tomography (SD-OCT) scans using the
Spetralis OCT (Heidelberg Engineering, Heidelberg,
Germany). The authors found significant diurnal
variation in subfoveal choroidal thickness, with a
mean amplitude (difference between the thickest and
thinnest values) of 33.7 ± 21.5 µm, despite virtually
no change in the neurosensory retinal thickness
measured at the same time. This is greater than the
mean of 20.3 µm reported by Toyokawa et al (the
calculated difference between the morning and
evening foveal choroidal thickness). One wonders
From the National Healthcare Group Eye Institute, Singapore (MCC, LWL,
KXC, CSHT); Fundus Image Reading Center, National Healthcare Group
Eye Institute, Singapore (CSHT); and Doheny Eye Institute, University of
Southern California, Los Angeles, California (SRS, CSHT).
Supported in part by the Beckman Institute for Macular Research and
Research to Prevent Blindness Physician Scientist Award (SRS) and the
National Healthcare Group Clinician Scientist Career Scheme (CSHT).
Dr. Sadda is a co-inventor of Doheny Eye Institute intellectual property related to optical coherence tomography that has been licensed by Topcon
Medical Systems, is a member of the scientific advisory board for Heidelberg Engineering, and receives research support from Carl Zeiss Meditec
and Optovue. Dr. Tan receives conference support from Bayer, Heidelberg
Engineering, and Novartis. The remaining authors have no financial or
proprietary interest in the materials presented herein.
Address correspondence to Colin S.H. Tan, National Healthcare Group Eye
Institute, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433;
(+65) 63577726; fax: (+65) 63577718; email: [email protected]
doi: 10.3928/23258160-20140522-02
Ophthalmic Surgery, Lasers & Imaging Retina | Healio.com/OSLIRetina
whether, in the patients studied by Toyokawa et
al, there may have been other time points when the
choroidal thickness may have been thicker or thinner
than their reported values, and whether this would
have affected the amplitude of choroidal thickness
variation. Tan et al also demonstrated a decreasing
trend of choroidal thickness progressively from 9 a.m.
to 5 p.m., consistent over 2 separate days, in contrast
to the apparent increase between morning and
evening measurements reported by Toyokawa et al.
Similarly, a study conducted in Japanese patients
by Usui et al,4 which was performed over a 24-hour
period, reported the same decreasing trend in choroidal
thickness from 9 a.m. to 6 p.m., with the thinnest
measurements occurring at 6 p.m. Furthermore, the
reported amplitude was 33.0 ± 14.3 µm, consistent
with that reported by Tan et al. Chakraborty et al5
used an optical biometer instead of OCT to measure
choroidal thickness and also reported a significant
diurnal variation in choroidal thickness, with a mean
change of 29 ± 16 µm, but reported a differing pattern
of diurnal variation between the 2 days.
In summary, we agree with Toyokawa et al that
there appears to be significant diurnal variation in
choroidal thickness in normal individuals, although
the exact pattern of diurnal variation, and whether
this is consistent in all individuals, remains uncertain.
Therefore, when assessing choroidal thickness in
clinical practice and trials, it is important to take into
account the time of measurements.
REFERENCES
1. Toyokawa N, Kimura H, Fukomoto A, Kuroda S. Difference in morning and evening choroidal thickness in Japanese subjects with no chorioretinal disease. Ophthalmic Surg Lasers Imaging. 2012;43(2):109114. doi: 10.3928/15428877-20120102-06.
2. Tan CSH, Ngo WK, Chew MC, et al. Diurnal variation of retinal
thickness measured by optical coherence tomography in normal
adults. Invest Ophthalmol Vis Sci. 2012;53(3):1639-1639.
3. Tan CS, Ouyang Y, Ruiz H, Sadda SR. Diurnal variation of choroidal
thickness in normal, healthy subjects measured by spectral domain optical
coherence tomography. Invest Ophthalmol Vis Sci. 2012;53(1):261-266.
4. Usui S, Ikuno Y, Akiba M, et al. Circadian changes in subfoveal
choroidal thickness and the relationship with circulatory factors in
healthy subjects. Invest Ophthalmol Vis Sci. 2012;53(4):2300-2307.
5. Chakraborty R, Read S, Collins M. Diurnal variations in axial length,
choroidal thickness, intraocular pressure, and ocular biometrics. Invest
Ophthalmol Vis Sci. 2011;52(8):5121-5129.
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