DIABETIC RETINOPATHY

What is diabetic retinopathy?

Diabetic retinopathy is degeneration of the retina as a result of diabetes induced changes in retinal vasculature. It affects over half of diabetics and advances with age. As the diabetes progresses, the capillaries of the eye swell and leak. Abnormal blood vessels are formed, a process called neovascularization. These blood vessels do not supply the retina with adequate oxygen and bleed into the vitrious humor. Some people also develop a macular edema which is swelling of the macula caused by the fluid and lipids that leak onto it from the blood vessels.

How does diabetic retinopathy affect vision?

An early warning sign is blurring of vision and a loss of acuity. Blindness can result from this if not treated. The retinal bleeding can interfere with the passage of light to the retina or retinal detachment can occur. This causes the photoreceptors to separate from the RPE (retinal pigment epithileum) and die, causing blindness wherever detachment has occurred.

Treatment:

The first step in treatment for diabetic retinopathy is controlling the diabetes. This involves stablizing blood sugar levels. If neovascularization has already occured, laser photocoagulation can be used to seal off the leaking blood vessels. Panretinal photocoagulation is another treatment which uses a laser to create hundreds of small holes in the retina to reduce its metabolic needs. This reduces the retina's oxygen requirements and causes the blood vessels to dry up. A vitrectomy can be performed if the blood vessels have invaded the vitreous. This procedure uses a hollow needle to eliminate the blood and vitreous humor within the eye. The area left empty is then filled with a saline solution to restore clarity of vision.

 

CATARACTS

What are cataracts?

Cataracts are changes in the lens of the eye that decrease its ability to transmit light and to deliver a clear image to the retina. They can occur alone or as a secondary consequence of other eye problems or diseases such as retinitis pigmentosa, ocular contusion, smoking, diabetes, injury, complications of eye surgery, or systematic use of steroids. Cataracts are usually identified by their location in the lens, or by their general cause. The major types of cataract identified by their origin or appearance during development are:

• Congenital / Infantile: present in the first year of life
• Secondary: caused by an eye disease
• Traumatic: caused by an injury
• Senile: occur in later adult life.
  

The most common type of cataracts are senile cataracts. They develop in 75% of people over 65 years of age and in 95% of those over 85 years of age.

How do cataracts affect vision?

By scattering and reducing the light reaching the retina, cataracts reduce image luminance and contrast. Some common symptoms of cataract include a reduction in acuity, night vision, light sensitivity, and color discrimination, especially for blues. Blurring and yellowing of vision, and increased sensitivity to glare are also common. During old age the hardening of the lens associated with cataract can induce myopia, allowing an eldery observer to regain the ability to read up close. This phenomenon is called second sight.

The photos below simulate the possible effects of a cataract on vision. Notice the decreased illumination, acuity, and color saturation in the view through a cataract compared to the view without a cataract.

Treatment

Surgery is the only treatment for cataracts. Nowadays, cataract is usually treated using the technique of phacoemulsification, in which the lens is broken up using an ultrasonic vibrating probe (40Hz) and aspirated through a small incision at the margin of the eye. A small, plastic intraocular lens (IOL) is then inseted into the eye to replace the refractive power lost by the removal of the lens. Some cataract patients experience blurry vision after surgery due to scar tissue that results from the surgery. For most, however, cataract surgery is highly effective. About 95% of post-operative patients have excellent vision, with improved acuity, color discrimination, and sensitivity in low light.

The link that follows (with permission of the author), provides more detailed information on cataracts, cataract surgery and cataract care:

Information on Cataracts

 

EXPLORE DIABETIC RETINOPATHY & CATARACTS:
MARY CASSATT