Eye Health

Presbyopia and How the Eyes Autofocus: I am A __________

David Mitchell - Thursday, October 30, 2014

16 Across, 6 letters, I Am A ______.
If you've done enough crossword puzzles, you're bound to have come across this clue. I've struggled through enough puzzles to figure out the answer is "camera," but I've never understood the intertextuality of it.


It does always make me think of the eye, and it's amazing ability to autofocus quickly from distance to near and back again.
When the eye is focused on a distant target, the pupil is wider and the muscles within the eye are relaxed.
When switching fixation to a near target (like when you're reading this), the eye makes a few rapid adjustments. The iris moves much like a camera's aperture, constricting your pupil smaller to increase depth of field and depth of focus. In addition, muscles within the eye constrict, causing an internal crystalline lens to change shape, refocusing light for a near target. This process is called accommodation, and it all happens in just a fraction of a second.


Inflexibility or inefficiency in this focusing system commonly leads to eyestrain, headaches, or poor performance in school or near work tasks. Accommodative insufficiency and accommodative infacility are two binocular vision disorders which can be treated using vision therapy.


The flexibility of the eye's focusing system, unfortunately, declines over time-- this is why reading glasses or bifocal lenses are an eventuality for most people over 40.
Presbyopia is the term used to describe this unavoidable progressive decline in the eyes' ability to focus.  Yes, sorry to say that like death and taxes, presbyopia is inescapable, and will eventually affect us all.


The good news is that there are more options than ever to compensate for presbyopia.  Progressive lenses are the most popular option today. These ‘no-line’ multifocal eyeglass lenses have a gradual curvature across the lens surface and provide clear vision at near and far distances, and also smooth, comfortable transitions in between.
Another option gaining popularity is the multifocal contact lens.  Dr. Lisa Mitchell has successfully fit hundreds of people in Houma, Thibodaux, and the surrounding areas in multifocal contact lenses. I like to think that I am as proficient at fitting multifocal lenses as Dr. Lisa, but there is an art and a science to fitting these lenses, and Dr. Lisa's committment to keeping up with the most current multifocal lenses and fitting techniques has made her the most successful contact lens specialist in our area.


Many people ask if laser vision correction will improve the vision changes due to presbyopia.  The short answer is "no." LASIK and other refractive surgeries work by changing the outer lens of the eye, the cornea.  Unfortunately, the decline in near vision due to presbyopia is due to the breakdown of the ability of the inner crystalline lens to dynamically change shape.  So laser vision correction can correct your eyes to see distance OR near clearly, but not both.


As time goes by, the lens within the eye will continue to change, and the prescription you require for near changes along with it.  We will prescribe stronger correction for near over time as these changes take place.  Each person has a unique subjective experience with presbyopia, and these changes are not the same for everyone. Typically, those who are nearsighted (need glasses to see distance) won't experience these presbyopic changes as early, perhaps not until 42-45 years of age.  Conversely, farsighted people, who may not wear glasses at all, may begin to experience symptoms in their mid to late 30s.   


The good news is that we at Mitchell Family Eye Care offer the newest technology in contact lenses and a wide variety of spectacle lenses to make sure you continue to have the clearest possible vision for everything you do.  If you're starting to notice that your "arms are too short," call or click here to schedule an appointment today.


Oh, and I finally Googled it: "I Am A Camera" was a novel, a play, and a movie.  And now I'm wondering, do people Google crossword puzzle answers? Seems like cheating to me. . .

Presbyopia and How the Eyes Autofocus: I am A __________