Presbyopia and Blended Vision 

PRESBYOPIA

The natural human lens, in our youth, works much like a camera lens, in that it is quite supple and can rapidly change shape like a zoom lens. This allows us to quickly focus up close without the need for reading glasses or bifocals. As we pass 40, the lens becomes progressively more rigid so that the zoom function takes longer and longer to occur so that by age 50-55 there is no zoom function at all! This explains the gradual loss of reading ability for most of us between the ages of 40 and 55. Those who have never worn glasses at all, suddenly, at age 45, are running off to the pharmacy to get reading glasses! Taking this one step further, as the human lens continues to age, in our 60’s and 70’s, it becomes more and more rigid, yellow and cloudy and is then called a cataract.

BLENDED VISION

The need for reading glasses after a surgical procedure is frequently a topic we spend a lot of time discussing. The concept of blended vision is often a good option for presbyopia patients. Typically, with blended vision, the dominant eye is set for distance and the non-dominant eye is set for near or intermediate distances. Blended vision can be performed in patients having LASIK, PRK, Phakic IOL, Refractive Lens Exchange and premium cataract surgery. We will determine which of your eyes is dominant during your pre-operative testing.

“I had blended vision performed on my eyes in 1994 when I was 38 years old. I didn’t need reading glasses at all until I was 50 and today I only wear them about 15-30 minutes per day,” says Dr. Kameen. While not for everyone, blended vision is a good option for many patients over 40. We can determine your tolerance for blended vision quite accurately during your preoperative testing.

It is important not to confuse blended vision with mono-vision. Mono-vision is really a contact lens term that rather radically creates one eye for distance and one eye for near. Sometimes patients can tolerate this, but more often, not. Obviously, mono-vision is easy to try with contact lenses, because if the patient doesn’t like it the contact can just be removed. It is not that easy to reverse surgical corrections, so we make sure to figure this out well before your procedure. Blended vision is milder than mono-vision because there is less difference between the two eyes. As a result, it is easier to tolerate because there is a nice overlap between distance, near and intermediate. It may take a few weeks for the brain to adapt to blended vision through a process known as neuro-adaptation.

The decision to have blended vision is best made between you and the doctor. Please know that some occupations such as law enforcement, aviation and military services require best distance correction in both eyes, so blended vision is sometimes not an option. Also, some patients who have blended vision, though legal to drive without glasses, choose to wear a very thin pair of eyeglasses for late night driving. Again, we will test your eyes, as well as better educate you regarding whether blended vision is a good option for you.