What is a Cataract?

What is a Cataract?

It is the eye’s natural lens that has become cloudy. This can be caused by age, sunlight, diabetes, certain drugs, trauma, smoking and nutritional deficiencies.

How is a Cataract treated?

When a cataract is mild, there is no need to remove it.  But once it impacts the vision and the person cannot see well, cataract surgery is performed. This is done with local anesthesia; the natural lens is removed and replaced with an intra-ocular lens (artificial lens).

Intra-ocular Lenses

Question: Why do you have to replace the lens?

Answer: If you leave the eye without a lens, the vision will be very blurry and the person will only see using very thick powerful glasses.

Question: Does everyone get the same type of replacement lens?

Answer: No. Lenses come in different powers measured in diopters. To figure out what lens is the correct fit for an eye, we need to take a few measurements.

Question: What measurements do you take to choose the correct lens?

Answer:  The length of the eye and the steepness of the cornea. Once we have these measurements we use a math formula.

Question: Are the measurements important?

Answer: Yes, it determines whether a person sees well after cataract surgery.

Question: What is the formula

Answer: A simplified formula is the SRK devised by Donald R. Sanders, PhD, MD; John A. Retzlaff, MD; and Manus C. Kraff, MD.

The SRK formula uses the following equation to calculate IOL power: 

P = A – 2.5L – 0.9K

P = final IOL power

A is the A Constant noted on the IOL box-based on the manufacturer guide (EX: 118.50)

L is the length of the eye

K is the average keratometry focusing power of the cornea

Question: How do you take these measurements?

Answer: A keratometer measures the curvature of the anterior corneal surface based on the power of a reflecting surface. An ultrasound is used to measure the length of the eye.