Obesity can lead to blindness
Overweight and obese people should be aware that their unhealthy lifestyle could put their eyesight at risk, scientists say.
It is common knowledge that expanding waistlines are linked to conditions such as diabetes, heart disease and cancer.
But research shows that obesity is also linked to eye problems which could lead to sight loss.
Two Israeli ophthalmologists are now warning that the prospect of eye disease should also be a powerful incentive to lose weight.
Professor Michael Belkin and Dr Zohar Habot-Wilner, from the Goldschleger Eye Institute at the Sheba Medical Centre, reviewed more than 20 studies involving thousands of patients worldwide.
They said they found a consistently strong link between obesity and the occurrence and development of four major eye diseases that cause blindness - age-related macular degeneration (AMD), cataracts, glaucoma and diabetic retinopathy.
Prof Belkin, a professor of ophthalmology at Tel Aviv University, said: "The purpose behind this review was to acquaint physicians and laypeople with the dangers of being fat as related to ophthalmology.
"All of this existing research had never been pulled together in a comprehensive way."
All the common eye diseases can affect sight to some extent, with most sufferers experiencing deterioration over time.
The main ones highlighted by the researchers were:
- Glaucoma - a group of diseases that can damage the eye's optic nerve, resulting in vision loss and blindness.
The researchers said that although the evidence was out there suggesting a link between obesity and these conditions, the results were not well known by the public.
Prof Belkin said that people with high Body Mass Index (BMI) who are clinically obese have an increased chance of eye disease.
These diseases are also more likely to progress more quickly in obese people.
The researchers said that in some cases the reason for the link between obesity and the diseases was clear.
For example, since glaucoma, diabetes and AMD all affect the vascular system and excess weight is known to create pulmonary problems, the blood vessels in the eye are affected and sight deteriorates.
But the link between weight and cataracts is less clear.
"Nobody has the faintest idea why cataracts are affected since it is a disease of the lens of the eye," Prof Belkin said.
Dr Habot-Wilner said it was likely that the link had something to do with the fact that obese people face a greater chance of developing gout - a disease in which the development of cataracts is more common.
But she stressed that in their study they wanted to raise awareness of the risks of sight problems linked to obesity, rather than why these conditions occur more often and cause more damage
in obese people.
"The message we want to send is that obesity can cause not just cancer and hypertension but also ocular disease.
"While this is something that most ophthalmologists know, it's not common knowledge and it should be.
"It's the risk factor that no one talks about."