Near Point Vision Stress & Nearsightedness

Baltimore Washington Eye Center, Maryland

Tuesday, January 10, 2012

Near Vision Stress & Nearsightedness

A perfectly seeing or emmetropic eye allows distant objects to focus clearly on the retina of the eye. A near sighted or myopic eye focuses distant light too quickly and the image of a distant target is blurred on the retina. If the object being viewed is moved closer to the eye it eventually reaches a point that allows it to be focused perfectly on the retina. This is called the patients “far point”. The more near sighted or myopic someone is the closer in to the eye you need to bring an object for it to be viewed clearly. When we “correct” a nearsighted patients vision, we place a lens in front of the eye that bends light in a way as to make distant objects focus clearly on the retina.

When we look at a near object our eye, which in its relaxed state is set to make distant objects focus on the retina, must refocus to zoom in on the near object and allow the divergent light rays coming from the near object to focus sharply on the retina. This process is called accommodation. Also when we regard near objects our eyes turn in to point at the target. Some people have poor accommodative function. Others have a tight posture so that even when the eyes are relaxed and not regarding a near target they are still slightly turned in relative to each other. This is called esophoria.

It has long been postulated that the effort and stress of near work can cause progression of myopia. For years many behavioral optometrists have recommended magnifying reading glasses or bifocals in children to slow the progression of myopia. A recent study published in April demonstrated that progressive lenses (no line bifocals) were more effective than single  vision distance spectacles in school age children with accommodative insufficiency and esophoria in slowing myopic progression. Another study published this fall in Survey of Ophthalmology analyzed nine different studies and found progressive lenses reduced progression of myopia compared to single vision lenses and that the effect was greater in patients with higher myopia and the outset and in patients of Asian descent.
Ask to have your child evaluated for risk factors related to near point stress at their next eye exam and see if progressive spectacle lenses can help slow down myopic progression.

Guest Blogger: Shari E. Strier, O.D., Optometrist with the Baltimore Washington Eye Center