Skip to main content
SpringerLink
Log in

Iris color and day–night changes in the sympathovagal ratio

  • Original Article
  • Published:
Sleep and Biological Rhythms Aims and scope Submit manuscript

Abstract

Iris melanocytes are innervated by parasympathetic and sympathetic nerve endings. Light affects autonomic nervous system activity via the retino-hypothalamic pathway. The hypothesis that the day-to-night variations in the sympatovagal ratio (LF/HF) may differ among individuals with different brown iris patterns was tested. A total of 621 healthy adults, aged between 16 and 50, with brown eyes and not diagnosed with a disease that might affect the autonomous nerve system were included in the study. A digital camera was used to acquire iris photos. Subjects were grouped into iris color groups (2–0 bg, 1–0 bg, 1–1 db, 1–1 lb, 2–0 b, and 1–0 b). Iris photos were analyzed with Picture Color Analyzer RBG software. The Central/Peripheral (R/RGB) ratio was used for objective distinction between the groups. Using 24-h Holter ECG monitoring, the change in the sympathovagal ratio from day (between 07:00 and 23:00 h) to night (between 23:00 and 07:00 h) was determined with the formula [(Day–Night) LF/HF)/Day LF/HF]. The frequency of subjects with a decrease in the LF/HF ratio from day to night was the highest in the 1–1 db group (65.7%), followed by the 1–1 lb group (56.4%). The highest increase was in the 2–0 bg group (76.5%), followed by the 1–0 B group (68.9%) (p < 0.001). Based on the findings of this study, iris color may be a predictive factor in diseases in which the circadian change of autonomic nervous system activity is effective.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2

Similar content being viewed by others

References

  1. Hu DN, Simon JD, Sarna T. Role of ocular melanin in ophthalmic physiology and pathology. Photochem Photobiol. 2008;84(3):639–44. https://doi.org/10.1111/j.1751-1097.2008.00316.x.

    Article  CAS  PubMed  Google Scholar 

  2. Mukuno K, Witmer R. Innervation of melanocytes in human iris. An electron microscopic study. Albrecht Von Graefes Arch Klin Exp Ophthalmol. 1977;203(1):1–8. https://doi.org/10.1007/BF00410042.

    Article  CAS  PubMed  Google Scholar 

  3. Pavan WJ, Raible DW. Specification of neural crest into sensory neuron and melanocyte lineages. Dev Biol. 2012;366(1):55–63. https://doi.org/10.1016/j.ydbio.2012.02.038.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  4. Hannibal J. Comparative neurology of circadian photoreception: the retinohypothalamic tract (RHT) in sighted and naturally blind mammals. Front Neurosci. 2021;15: 640113. https://doi.org/10.3389/fnins.2021.640113.

    Article  PubMed  PubMed Central  Google Scholar 

  5. Kiessling S, Sollars PJ, Pickard GE. Light stimulates the mouse adrenal through a retinohypothalamic pathway independent of an effect on the clock in the suprachiasmatic nucleus. PLoS ONE. 2014;9(3): e92959. https://doi.org/10.1371/journal.pone.0092959.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  6. Panza JA, Epstein SE, Quyyumi AA. Circadian variation in vascular tone and its relation to α-sympathetic vasoconstrictor activity. N Engl J Med. 1991;325:986–90. https://doi.org/10.1056/NEJM199110033251402.

    Article  CAS  PubMed  Google Scholar 

  7. von Rosenberg W, Chanwimalueang T, Adjei T, et al. Resolving ambiguities in the LF/HF ratio: LF-HF scatter plots for the categorization of mental and physical stress from HRV. Front Physiol. 2017;8:360. https://doi.org/10.3389/fphys.2017.00360.

    Article  Google Scholar 

  8. Parmeggiani PL, Morrison AR. Alterations in autonomic functions during sleep. In: Loewy AD, Spyer KM, editors. Central regulation of autonomic functions. New York: Oxford University Press; 1990.

    Google Scholar 

  9. Mackey DA, Wilkinson CH, Kearns LS, Hewitt AW. Classification of iris colour: review and refinement of a classification schema. Clin Exp Ophthalmol. 2011;39(5):462–71. https://doi.org/10.1111/j.1442-9071.2010.02487.x.

    Article  PubMed  Google Scholar 

  10. Otaka I, Kumagai K, Inagaki Y, et al. Simple and inexpensive software designed for the evaluation of color. Am J Ophthalmol. 2002;133(1):140–2. https://doi.org/10.1016/s0002-9394(01)01213-2.

    Article  PubMed  Google Scholar 

  11. Task Force of the European Society of Cardiology the North American Society of Pacing Electrophysiology Heart Rate Variability Standards of Measurement, Physiological Interpretation, and Clinical Use Circulation. 1996;93:1043–1065

  12. Billman GE. The LF/HF ratio does not accurately measure cardiac sympatho-vagal balance. Front Physiol. 2013;20(4):26. https://doi.org/10.3389/fphys.2013.00026.

    Article  Google Scholar 

  13. Hale BD, Landers DM, Snyder Bauer R, Goggin NL. Iris pigmentation and fractionated reaction and reflex time. Biol Psychol. 1980;10(1):57–67. https://doi.org/10.1016/0301-0511(80)90007-1.

    Article  CAS  PubMed  Google Scholar 

  14. Markle A. Eye color and responsiveness to arousing stimuli. Percept Mot Skills. 1976;43(1):127–33. https://doi.org/10.2466/pms.1976.43.1.127.

    Article  CAS  PubMed  Google Scholar 

  15. Rosenberg A, Kagan J. Iris pigmentation and behavioral inhibition. Dev Psychobiol. 1987;20(4):377–92. https://doi.org/10.1002/dev.42020040.

    Article  CAS  PubMed  Google Scholar 

  16. Takeda K, Takahashi NH, Shibahara S. Neuroendocrine functions of melanocytes: beyond the skin-deep melanin maker. Tohoku J Exp Med. 2007;211(3):201–21. https://doi.org/10.1620/tjem.211.201.

    Article  CAS  PubMed  Google Scholar 

  17. Dryja TP, Kimball GP, Albert DM. Light stimulation of iris tyrosinase in vivo. Invest Ophthalmol Vis Sci. 1980;19(5):559–62.

    CAS  PubMed  Google Scholar 

  18. Albert DM, McGuire JS, Bernard GD, Sherry P. Iris melanocyte response to MSH and related drugs. Yale J Biol Med. 1973;46:702.

    Google Scholar 

  19. Applebury ML, Hargrave PA. Molecular biology of the visual pigments. Vision Res. 1986;26(12):1881–95. https://doi.org/10.1016/0042-6989(86)90115-x.

    Article  CAS  PubMed  Google Scholar 

  20. McCartney AC, Riordan-Eva P, Howes RC, Spalton DJ. Horner’s syndrome: an electron microscopic study of a human iris. Br J Ophthalmol. 1992;76(12):746–9. https://doi.org/10.1136/bjo.76.12.746.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  21. Foster RG, Hughes S, Peirson SN. Circadian Photoentrainment in Mice and Humans. Biology (Basel). 2020;9(7):180. https://doi.org/10.3390/biology9070180.

    Article  CAS  PubMed  Google Scholar 

  22. Iyengar B. Melatonin and melanocyte functions. Biol Signals Recept. 2000;9(5):260–6. https://doi.org/10.1159/000014648.

    Article  CAS  PubMed  Google Scholar 

  23. Osborne NN, Chidlow G. The presence of functional melatonin receptors in the iris-ciliary processes of the rabbit eye. Exp Eye Res. 1994;59(1):3–9. https://doi.org/10.1006/exer.1994.1076.

    Article  CAS  PubMed  Google Scholar 

  24. Dominguez-Rodriguez A, Abreu-Gonzalez P, Reiter RJ. Melatonin and cardiovascular disease: myth or reality? Rev Esp Cardiol (Engl Ed). 2012;65(3):215–8. https://doi.org/10.1016/j.recesp.2011.10.009.

    Article  PubMed  Google Scholar 

  25. Bashkatov AN, Genina E A, Koblov E V, et al. Proc. of SPIE Vol. 6085, 60850N, Complex Dynamics and Fluctuations in Biomedical Photonics III 2006;1605–7422/06/15. Estimation of melanin content in iris of human eye: prognosis for glaucoma diagnostics. https://doi.org/10.1117/12.659176

  26. Vandewalle GG, Schwartz S, Grandjean D, et al. Spectral quality of light modulates emotional brain responses in humans. Proc Natl Acad Sci U S A. 2010;107(45):19549–54. https://doi.org/10.1073/pnas.1010180107.

    Article  PubMed  PubMed Central  Google Scholar 

  27. Lucas RJ, Peirson SN, Berson DM, et al. Measuring and using light in the melanopsin age. Trends Neurosci. 2014;37(1):1–9. https://doi.org/10.1016/j.tins.2013.10.004.

    Article  CAS  PubMed  Google Scholar 

  28. IJspeert JK, de Waard PW, van den Berg TJ, de Jong PT. The intraocular straylight function in 129 healthy volunteers; dependence on angle, age and pigmentation. Vision Res. 1990;30(5):699–707. https://doi.org/10.1016/0042-6989(90)90096-4.

    Article  CAS  PubMed  Google Scholar 

  29. van den Berg TJ, IJspeert JK, de Waard PW. Dependence of intraocular straylight on pigmentation and light transmission through the ocular wall. Vision Res. 1991;31(7–8):1361–7. https://doi.org/10.1016/0042-6989(91)90057-c.

    Article  PubMed  Google Scholar 

  30. Mien IH, Pin CEC, Lau P, et al. Effects of exposure to intermittent versus continuous red light on human circadian rhythms, melatonin suppression, and pupillary constriction. PLoS ONE. 2014;9(5): e96532. https://doi.org/10.1371/journal.pone.0096532.

    Article  CAS  Google Scholar 

  31. Eglen RM. Muscarinic receptor subtype pharmacology and physiology. Prog Med Chem. 2005;43:105–36. https://doi.org/10.1016/S0079-6468(05)43004-0.

    Article  CAS  PubMed  Google Scholar 

  32. Yamada M, Miyakawa T, Duttaroy A, et al. Mice lacking the M3 muscarinic acetylcholine receptor are hypophagic and lean. Nature. 2001;410(6825):207–12. https://doi.org/10.1038/35065604.

    Article  CAS  PubMed  Google Scholar 

  33. Niggemann B, Weinbauer G, Vogel F, Korte R. A standardized approach for iris color determination. Int J Toxicol. 2003;22(1):49–51. https://doi.org/10.1080/10915810305081.

    Article  CAS  PubMed  Google Scholar 

  34. Koblova EV, Bashkatov AN, Dolotov LE, et al. Monte Carlo modeling of eye iris color. Saratov Fall Meeting 2006: Optical Technologies in Biophysics and Medicine VIII. Proceedings of the SPIE, Volume 6535, 653521. https://doi.org/10.1117/12.741086

Download references

Funding

None.

Author information

Authors and Affiliations

  1. Ankara Ataturk Sanatorium Training and Research Hospital, Ankara, Turkey

    Şahbender Koç & Aslı Enzel Koç

  2. Psychiatry, Trabzon Fatih State Hospital, Trabzon, Turkey

    Aslı Enzel Koç

Authors
  1. Şahbender Koç
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Aslı Enzel Koç
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

ŞK: selection of subjects, their clinical evaluation, acquisition of Holter ECGs and their analysis, iris photo shoot, iris color measurement, interpretation of data for the work, and writing. AEK: data interpretation, iris color measurement, final approval of the version to be published, revision of the manuscript.

Corresponding author

Correspondence to Şahbender Koç.

Ethics declarations

Conflict of interest

Authors declare that they have no conflict of interest.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Koç, Ş., Koç, A.E. Iris color and day–night changes in the sympathovagal ratio. Sleep Biol. Rhythms 22, 191–198 (2024). https://doi.org/10.1007/s41105-023-00492-y

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s41105-023-00492-y

Keywords

Search

Navigation