Diabetes can cause cataracts

Diabetes can cause cataracts. The silent thief, the vicious thief, the ruthless, etc., all these are not enough to describe the devastating effects caused by diabetes on the human body, and on the eyes in particular.

The shocking fact is that diabetes is the most common cause of adulthood blindness. This is because diabetes can result in three of the most serious eye complications, which are: diabetic retinopathy, diabetic cataract and diabetic glaucoma.

The vicious thing about diabetes is that it works in silence, hidden from the eyes. A person might be suffering from diabetes several years before accidentally discovering that he is suffering from diabetes after the disease has established its harmful effects all over his body. This is the moment where the patient starts complaining of health problems. In the following, we will illustrate the relation between diabetes and cataract.

Diabetes increases the risk of developing cataract

This is absolutely true. Diabetic patients are more prone to develop cataract, by as much as 60%, compared to non-diabetics. This is because diabetes leads to early formation of cataract in young patients. It also accelerates the development of adult diabetic cataract.

Mechanism of cataract formation in diabetics

In order to better understand the mechanism of cataract formation in diabetics, we first have to realize some physiological properties of the human eye.

The crystalline lens is avascular in structure; by this, we mean that there is no blood supply that reaches the lens (neither arteries nor veins). The lens gets nutrients (glucose) and oxygen through diffusion from the surrounding aqueous humor (a fluid that fills the anterior half of the eye ball).

In diabetic patients who don’t have tight control over their blood glucose levels, the blood glucose level rises to values higher than the normal range (the normal range is 90 – 125 mg/dl before meals and less than 180 mg/dl two hours after meals). Consequently, the glucose level in the aqueous humors rises. This leads to diffusion of a very big amount of glucose inside the lens.

Presence of a high concentration of glucose inside the lens leads to its swelling, due to absorption of large amounts of water inside the lens. This affects the clarity of the crystalline lens as well as its refractive index, leading to acute deterioration of vision.

The aldose reductase enzyme

This is an enzyme found in the human lens. It is responsible for conversion of glucose to a substance called sorbitol. Accumulation of sorbitol inside the lens leads to a sequence of pathological and chemical changes in the structure of lens proteins, ending in the formation of lens opacities.

The free oxygen radicals

These are harmful molecules produced throughout the natural metabolic processes happening inside our bodies, and are removed by specific counter acting mechanisms. When high levels of sorbitol are accumulated inside the lens, a great amount of free radicals is generated.

Free radicals have destructive effect on the surrounding structures. They alter the chemical and physical composition of the transparent lens fibers rendering them opaque thus helping in formation of cataract.

The interesting thing is the presence of a scavenger system (antioxidants) responsible for removal of these free radicals so as to limit their harmful effects.

High levels of sorbitol lead to impairment of these antioxidants. This leads to accumulation of free oxygen radicals inside the lens thus accelerating the formation of lens opacities.

Cell death (apoptosis)

Accumulation of sorbitol inside the lens leads to death of the epithelial cells responsible for formation of new lens fibers. This leads to formation of lens opacities and cataract.

Types of cataract associated with diabetes

From the previously mention information we can conclude the following: Diabetes leads to early formation of cataract in young patients and acceleration of cataract formation in old patients.

  • In young patients: the sudden rise in blood sugar leads to formation of a type of cataract known as “Snow flake cataract”. Snow flack cataract is characterized by rapid progression. It is more likely to occur in diabetes mellitus type I patients. The good thing about this type of cataract is that it can be reversed with good glycemic control. Snow flack cataract is the only reversible type of cataract.
  •  In old patients: high levels of blood glucose are associated with development of two particular types of cataract namely; the posterior sub capsular cataract, and the cortical cataract.

In a nutshell

Diabetes mellitus is one of the major risk factors for developing cataract. It is the most common cause of adulthood blindness.

Tight glycemic control prevents or delays the harmful effects caused by diabetes, on the eyes. Regular visits to your ophthalmologist ensure continuous monitoring of the state of your eye as well as early detection and treatment of any complication. Prevention is always better than cure. When you realize diabetes can cause cataracts, your best option is to not let it happen at all.

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