JOIN NOW

Caffeine and Eyes: Balancing the Benefits and Risks

by | Feb 1, 2025 | Manuscripts | 0 comments

Moesha Rudo Mavangira B.Optom Student,

Parul University, Vadodara, India

 

Caffeine (1,3,7-trimethylxanthine) with molecular formula as (C8H10N4O2) is the most popular psychoactive drug consumed by 80% of the world’s population.(1,2) Caffeine has nearly 100% oral bioavailability with primary route of administration, in which it is absorbed into bloodstream and distributed into body systems, where it binds with adenosine receptors to produce antagonistic effects.(1,2) Its consumption is associated with certain symptoms such as migraine and insomnia. Caffeine is known for its effect on CNS, heart rate, muscles, and blood pressure, but there are very few studies conducted to see its effects on the ocular system. Adenosine receptors are found in various ocular tissues, including the cornea, iris, ciliary body, choroid, and retina. (3,5)

Effect of Caffeine on eye health:

Positive Effects of Caffeine on Eye Health:

1. Increase of tear production:

Tears are secreted continuously throughout the day by accessory lacrimal glands (basal secretion) and the main lacrimal gland (reflex secretion). As an adenosine antagonist, caffeine increases acetylcholine levels, (7,8) a key neurotransmitter of the parasympathetic pathway. Acetylcholine acts on muscarinic receptors in the main lacrimal gland, activating G proteins and raising intracellular calcium levels. (7) This, in turn, triggers ion channels in the apical and basolateral membranes, resulting in the secretion of electrolytes, water, and proteins, thereby stimulating tear production.(11) Caffeinated coffee consumption has been associated with a reduced risk of Dry eye disease, while tea and decaffeinated coffee have been linked to an increased risk.(11)

2. Caffeine with antioxidant Properties:

Lens is responsible for accommodation (focusing on near objects by itself becoming more convex). Lens transparency is maintained by antioxidants like glutathione and ascorbic acid. Advanced aging, UV exposure and diabetes are factors which may cause depletion of antioxidants leading to cataract formation. (9) Caffeine, known for its antioxidant properties, may help protect the crystalline lens from oxidative damage and reduced risk of cataract development, highlighting its protective antioxidant effects.(9,10)

Negative Effects of Caffeine on Eye Health:

1. Effect of caffeine on accommodation and pupil size:

Caffeine stimulates dilator sphincter muscles responsible for pupil dilation and relaxes zonules on lens capsules responsible for increasing. (6,12) This increase in amplitude of accommodation might have occurred due to the stimulatory effect caused by caffeine on parasympathetic nerves. (12,13) These parasympathetic nerves are responsible for ciliary constriction, leading to increase in refractive power due to the thickening of the crystalline lens, this allows the eyes to focus the objects closer than needed, thus leading to an increase in amplitude of accommodation. (13)

2. Effect of Caffeine on Glaucoma:

In glaucoma, elevated intraocular pressure can impair blood supply to critical ocular tissues, including the retina, choroid, and optic nerve head14. Caffeine’s vasoconstrictive properties contribute to decreased ocular blood flow, which may aggravate glaucoma progression. (15) Caffeine antagonistic property to adenosine receptors, reduce aqueous humor outflow, by causing smooth muscle relaxation in the filtration system resulting in closure of trabecular meshwork, causing improper drainage of aqueous fluid, leading to Acute angle-closure glaucoma (AACG) which cause vision loss generation. (14,16)

3. Effect of caffeine on the vascular layer:

Caffeine can result in decreased circulation in the choroid, retina, and ocular nerve head. (17)  Suggesting that caffeine had an effect on ocular blood vessels and reduction in choroidal thickness. (17,18) Caffeine exerts its antagonist effect at adenosine A2A receptors leading to vasoconstriction. Changes in superficial retinal vasculature could be due to vasoconstriction. Caffeine exerts its antagonist effect at adenosine A2A receptors leading to vasoconstriction. (17,19)

Conclusion:

Caffeine, a widely consumed psychoactive substance, has significant effects on eye health through its interaction with adenosine receptors in ocular tissues. It has both positive and negative effects on ocular health. Regular eye exams and early detection of issues are essential for maintaining eye health. Further research is needed to clarify caffeine’s ocular effects and provide guidelines for safe consumption.

 

References:

  1. Heckman, M. A., Weil, J., & De Mejia, E. G. (2010). Caffeine (1, 3, 7‐trimethylxanthine) in foods: a comprehensive review on consumption, functionality, safety, and regulatory matters. Journal of food science, 75(3), R77-R87.
  2. Redondo, B., Vera, J., Carreño–Rodríguez, C., Molina-Romero, R., & Jiménez, R. (2020). Acute effects of caffeine on dynamic accommodative response and pupil size: a placebo-controlled, double-blind, balanced crossover study. Current Eye Research, 45(9), 1074-1081.
  3. Lutty, G. A., & McLeod, D. S. (2003). Retinal vascular development and oxygen-induced retinopathy: a role for adenosine. Progress in retinal and eye research, 22(1), 95-111.
  4. Sorenson, C. M., Song, Y. S., Zaitoun, I. S., Wang, S., Hanna, B. A., Darjatmoko, S. R., … & Sheibani, N. (2021). Caffeine inhibits choroidal neovascularization through mitigation of inflammatory and angiogenesis activities. Frontiers in Cell and Developmental Biology, 9, 737426.
  5. Arita, R., Yanagi, Y., Honda, N., Maeda, S., Maeda, K., Kuchiba, A., … & Amano, S. (2012). Caffeine increases tear volume depending on polymorphisms within the adenosine A2a receptor gene and cytochrome P450 1A2. Ophthalmology, 119(5), 972-978.
  6. Abokyi, S., Owusu-Mensah, J., & Osei, K. A. (2017). Caffeine intake is associated with pupil dilation and enhanced accommodation. Eye, 31(4), 615-619.
  7. Magno, M. S., Utheim, T. P., Morthen, M. K., Snieder, H., Jansonius, N. M., Hammond, C. J., & Vehof, J. (2023). The relationship between caffeine intake and dry eye disease. Cornea, 42(2), 186-193.
  8. Chandra, P., Gaur, A., & Varma, S. (2011). Effect of caffeine on the intraocular pressure in patients with primary open angle glaucoma. Clinical Ophthalmology, 1623-1629.
  9. Dervişoğulları, M. S., Totan, Y., Yüce, A., & Kulak, A. E. (2016). Acute effects of caffeine on choroidal thickness and ocular pulse amplitude. Cutaneous and ocular toxicology, 35(4), 281-286.
  10. Grey, A. C., Demarais, N. J., West, B. J., & Donaldson, P. J. (2019). A quantitative map of glutathione in the aging human lens. International journal of mass spectrometry, 437, 58-68.
  11. Magno, M. S., Utheim, T. P., Morthen, M. K., Snieder, H., Jansonius, N. M., Hammond, C. J., & Vehof, J. (2023). The relationship between caffeine intake and dry eye disease. Cornea, 42(2), 186-193.
  12. Abokyi, S., Owusu-Mensah, J., & Osei, K. A. (2017). Caffeine intake is associated with pupil dilation and enhanced accommodation. Eye, 31(4), 615-619.
  13. Gilmartin B, Mallen EA, Wolffsohn JS. Sympathetic control of accommodation: evidence for inter-subject variation. Ophthalmic Physiol Opt 2002; 22(5): 366–371.
  14. Jiwani, A. Z., Rhee, D. J., Brauner, S. C., Gardiner, M. F., Chen, T. C., Shen, L. Q., … & Turalba, A. V. (2012). Effects of caffeinated coffee consumption on intraocular pressure, ocular perfusion pressure, and ocular pulse amplitude: a randomized controlled trial. Eye, 26(8), 1122-1130.
  15. Rahamin Avisar, R. A., Erez Avisar, E. A., & Dov Weinberger, D. W. (2002). Effect of coffee consumption on intraocular pressure.
  16. Chandrasekaran, S., Rochtchina, E., & Mitchell, P. (2005). Effects of caffeine on intraocular pressure: the Blue Mountains Eye Study. Journal of glaucoma, 14(6), 504-507.
  17. Higginbotham, E. J., Kilimanjaro, H. A., Wilensky, J. T., Batenhorst, R. L., & Hermann, D. (1989). The effect of caffeine on intraocuular pressure in glaucoma patents. Ophthalmology, 96(5), 624-626.
  18. Karti, O., Zengin, M. O., Kerci, S. G., Ayhan, Z., & Kusbeci, T. (2019). Acute effect of caffeine on macular microcirculation in healthy subjects: an optical coherence tomography angiography study. Retina, 39(5), 964-971.
  19. Polska, E., Ehrlich, P., Luksch, A., Fuchsjäger-Mayrl, G., & Schmetterer, L. (2003). Effects of adenosine on intraocular pressure, optic nerve head blood flow, and choroidal blood flow in healthy humans. Investigative ophthalmology & visual science, 44(7), 3110-3114.

 

Submit a Comment