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Previously unknown risk factors linked to keratoconus

eye check

Keratoconus is an eye condition that weakens the rounded clear covering of the eye, the cornea, and leads it to become cone-shaped over time. This causes serious progressive near-sightedness at a relatively young age.

Now, the largest clinical study ever of the condition has provided new insights into those at greatest risk. The researchers say that patients with keratoconus and their families, as well as doctors, should be aware of other potential health problems uncovered in the study.

The investigation checked medical insurance data of than 16,000 people – half with confirmed keratoconus and half from those with similar characteristics but no keratoconus. This enables researchers to see which characteristics and medical conditions were most associated with keratoconus, and which weren’t. The people in the study were mostly in their 30s and 40s.

Lead author, Dr Maria Woodward, Assistant Professor of Ophthalmology at University of Michigan, put the importance of this research into context by saying: “Eye health relates to total body health, and we as ophthalmologists need to be aware of more than just eyeballs when we see patients.”

The study confirmed many suspicions about the condition raised by previous small studies – but casts doubt on others. For instance, men were already known to have a higher risk, which the study confirmed.
And people with Down syndrome have a six times higher susceptibility to keratoconus than the general population. This reinforces the high importance of screening and treatment for the condition in members of the Down syndrome community, starting at a young age.

One major revelation, previously unknown, is that people of African American and Latino heritage have 50 percent higher chance than whites of contracting keratoconus. Equally revealing is the finding of a 39 percent lower rate among people of Asian heritage that contradicts previous research.

Diabetes and other chronic illness: what’s the link to keratoconus?

In a real conundrum it appears that while diabetes causes other negative effects to the eye, the cornea may be strengthened as a by-product of those changes. This is suggested by a finding of 20 percent lower prevalence of keratoconus among people with diabetes.

The researchers also looked at other chronic conditions thought to be associated with keratoconus – such as allergic rhinitis, mitral valve prolapse, collagen vascular disease, aortic aneurysm and depression – and found no higher odds of the condition.

But when it came to people who had been diagnosed with sleep apnoea – which interrupts breathing during sleep, and can cause snoring, daytime sleepiness and a higher risk of heart disease and stroke – there was a statistically significant higher chance of also having keratoconus. Similarly, people with asthma had higher susceptibility to also having the eye condition.

The authors note that because they used insurance data, they can only see associations of conditions recorded on medical bills, and not cause and effect. And, their findings might not apply to people with no health insurance and therefore less access to medical care. They also can’t tell which of the people had other risk factors for keratoconus, such as eye rubbing, a family history of the condition, and other conditions not present in the database.

University of Michigan Health System

Last updated: November 29, 2018

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