The cornea is the clear outer layer at the front of your eye, which allows you to focus light and see clearly. Glaucoma is typically caused by a combination of genetic and environmental factors. 

A small percentage of cases (nearly one in 20) is the result of a mutation in a single gene, POU6F2, that may affect corneal thickness. The BrightFocus Foundation takes a look at this genetic factor, corneal thickness, and how it may lead to glaucoma.* 

What are the risk factors for glaucoma?  

The Ocular Hypertension Treatment Studies (OHTS) examined a large group of glaucoma patients in the ’90s and found the following risk factors for developing primary open-angle glaucoma (POAG): 

• Aging is a major factor, with the majority of glaucoma patients in their 60s and 70s. 
• The higher a person’s intraocular pressure (IOP) was, the greater the risk for developing glaucoma. Fortunately, medication is now available to lower IOP. 
• Family history (genetics) is an uncontrollable risk factor found in glaucoma patients. 
• The thinner the cornea, the higher the risk of developing glaucoma. Corneal thickness may also affect the severity of visual field loss and glaucoma progression.

Is there a relationship between corneal thickness and IOP? 

While a definitive answer is unavailable, many medical professionals believe that corneal thickness affects IOP. Even if there is an effect, the effect is small and, ultimately, will not increase your risk for glaucoma.  

Is genetics responsible for corneal thickness?

The answer is yes. A study done on mice has shown the POU6F2 gene affects corneal thickness. When this gene was inactivated in mice, their corneas were thinner. Dr. Janey L. Wiggs, MD, a professor of ophthalmology at Harvard Medical School, also looked at human populations and found this gene to be a risk factor for glaucoma. Moreover, the POU6F2 gene is responsible for retinal ganglion cells, which connect the eye to the brain and are the first to die in glaucoma. 

Genetics contribute to corneal thickness more than any other eye feature. If you have a thin cornea, your children will more than likely have a thin cornea. The converse is also true. In addition, corneal thickness can differ among racial and ethnic groups. For this reason, Black people are at higher risk for glaucoma, as they tend to have thinner corneas.

*Geisert, E. (2020, Aug. 17). Glaucoma and Corneal Thickness. BrightFocus Foundation. https://www.brightfocus.org/glaucoma/article/glaucoma-and-corneal-thickness

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