Eye Health Function of the Cornea By Troy Bedinghaus, OD Updated on April 08, 2022 Medically reviewed by Johnstone M. Kim, MD Fact checked by Angela Underwood Print The cornea is the transparent, dome-like structure on the front part of the eye. The cornea gives the eye focus and refracting power. BSIP / UIG / Getty Images Function The cornea functions like a camera lens, helping to focus light coming into the eye onto the retina. The cornea is also filled with nerves that alert us to irritations that could potentially harm our vision and eye health. What Is It Made Of? The cornea is a remarkable piece of tissue made up of specialized cells. One thing unique to the cornea is that there are no blood vessels in the cornea to provide it nourishment. The corneal tissue is arranged in six different layers, with the final layer discovered in 2013: Each layer serves a different purpose. The first five layers below are described in full in the Indian Journal of Opthalmology. The last layer is defined in the journal Opthalmology. Epithelium: This layer acts as a barrier to prevent chemicals, water, and microbes from entering the eye. It also provides a smooth optical surface as an internal part of tear film-cornea interface contributing to the refractive power of the eye, and has Langerhans cells thatperform immunological functions.Bowman’s Layer: This layer maintaitns the corneal shape.Stroma: This layer gives the cornea mechanical strength and is the main refracting lens and transparency of the cornea.Descemet’s Membrane: This layer is the resting layer for the endothelial cells.Endothelium: This layer maintains corneal clarity by removing water from the corneal stroma.Dua's Layer: Its recognition impacts the future of posterior corneal surgery and the understanding of corneal biomechanics, posterior corneal pathology such as acute hyrops, Descematocele, and pre-Descemet's dystrophies. Measurement and Examination Eye doctors can view the cornea under a slit lamp biomicroscope. A slit lamp is basically an upright microscope. A special slit beam is used to illuminate the different layers of the cornea. To measure the thickness of the cornea, doctors perform pachymetry. Pachymetry can be performed using an ultrasonic pachymeter. The power and the curvature of the cornea can be measured by a corneal topographer. This may have implications for prescription contact lenses, corneal surgery, cataract surgery and corneal disease monitoring and management. Frequently Asked Questions What causes corneal abrasion? Corneal abrasion is caused by damage or trauma inflicted to the cornea. In most cases, only the outer layer is affected, but it is still a serious issue. It can be caused by physical contact with a thin or sharp object, wearing contact lenses for too long, conditions like dry eye syndrome, or foreign particles entering the eye. What health conditions can affect the cornea? There are several health conditions that can affect the cornea. This includes allergies, dry eye, corneal dystrophies (eye diseases affecting the cornea), keratitis (inflammation), and injury. Certain eye diseases, such as keratoconus, are sometimes inherited. Are there risks to corneal transplant? Yes, there are risks to corneal transplant. It is a mostly safe procedure, but the biggest risk is the body rejecting a transplant of the cornea. This is less of a risk for partial thickness corneal transplant. Medicine can sometimes be used to help the body accept a different cornea. 11 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Sridhar MS. Anatomy of cornea and ocular surface. Indian Journal of Ophthalmology. 2018;66(2):190-194. PMID:29380756 Shaheen BS, Bakir M, Jain S. Corneal nerves in health and disease. Survey of Ophthalmology. 2014;59(3):263-285. doi:10.1016/j.survophthal.2013.09.002 Southern Illinois University. Cornea. Science Focus. Is There Any Part of the Body That Doesn’t Have Blood Vessels? Dua HS, Said DG. Clinical evidence of the pre-Descemets layer (Dua’s layer) in corneal pathology. Eye. 2016;30(8):1144-1145. doi:10.1038/eye.2016.62 Dua HS, Faraj LA, Said DG, Gray T, Lowe J. Human corneal anatomy redefined. Ophthalmology. 2013;120(9):1778-1785. doi:10.1016/j.ophtha.2013.01.018 American Academy of Opthalmology. What is a Slit Lamp? ScienceDirect. Ultrasonic Pachymeter. National Eye Institute. Corneal Conditions. National Eye Institute. Corneal Dystrophies. American Academy of Ophthalmology. About Corneal Transplantation. By Troy Bedinghaus, OD Troy L. Bedinghaus, OD, board-certified optometric physician, owns Lakewood Family Eye Care in Florida. 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