Nerve damage in the eyes begins long before type 2 diabetes is diagnosed, Dutch study suggests

  • Cornea provides a window to nerve damage elsewhere in the body 

New research presented at the annual meeting of the European Association for the Study of Diabetes in Stockholm, Sweden (19-23 Sept) suggests that damage to nerves in the cornea begins before type 2 diabetes is diagnosed.

Nerve damage, or neuropathy, is a common, serious, complication of type 2 diabetes. It can affect nerves in different parts of the body, causing pain and numbness in the legs, feet and hands, as well as muscle and organ problems.  

Loss of nerves in the cornea can cause a range of problems from dry eye to vision loss. It was used in this study as proxy for neuropathy throughout the body.

Dr Sara Mokhtar, of the Department of Internal Medicine, Maastricht University Medical Center+, Maastricht, Netherlands, and colleagues studied the health of the corneal nerves in people with diabetes, pre-diabetes (where blood sugar levels are higher than normal but not high enough to be classed as T2D) and people without T2D or pre-diabetes (people with normal glucose metabolism).

The 3,471 participants (48.4% men) had an average age of 59.4 years.  21% had T2D, 14.7% had pre-diabetes and 64.3% had neither T2D nor pre-diabetes. 

The amount of damage to the corneal nerve fibres rose in line with the amount of impairment to glucose metabolism.  The amount of corneal nerve damage was 8% higher with pre-diabetes than in those with normal glucose metabolism and 8% higher in those with T2D than in those with pre-diabetes. When comparing those with T2D with people with normal glucose metabolism, those with T2D at 14% more nerve damage. 

Higher blood sugar levels, including higher HbA1c (average blood sugar level over several months) and 2-hour post-load glucose (blood sugar level two hours after a meal), were also associated with higher levels of corneal nerve damage.

And the higher the blood sugar levels were, the greater the damage.

Participants who had had diabetes for longer also had more damage to their corneal nerves. 

The researchers conclude that the amount of damage to the corneal nerve fibres increased linearly with the amount of impairment to glucose metabolism and with blood sugar levels.

Dr Mokhtar says: “We know from other studies that it typically takes three to five years to progress from prediabetes to type 2 diabetes. Our results, from the first study of its kind, suggest that high levels of blood sugar can begin to damage corneal nerves long before type 2 diabetes develops.

“Nerve damage in the cornea is relatively easy to measure and provides a window to nerve damage elsewhere in the body.  If we could pick up nerve damage early on, we might be able to delay or prevent it and the problems it causes, and so significantly improve quality of life.

“Further research is needed, however, to prove that higher glucose level is the cause of the damage, as well as whether early blood sugar control may delay or prevent it.”


The authors declare no conflicts of interest.

This press release is based on oral presentation 155 at the annual meeting of the European Association for the Study of Diabetes (EASD). The material has been peer reviewed by the congress selection committee. There is no full paper at this stage. Please note, there is no poster with this presentation. 

For full abstract, click here 

For full press conference slides, click here



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