Eyes are amazing structures, moving about, translating visual pictures into cognitive information that tells us an awful lot about our world. Seeing things up close requires something called accommodation. The amount of change that occurs in the lens of an eye, as it moves from relaxed to what is termed fully accommodated, is called the amplitude of accommodation. Contraction of the ciliary muscle causes the lens to move away from the sclera, becoming rounder and changing the diopter power of the eye. The measurement of accommodation in each eye is taken separately.
For adults, the measurement at which things in the near visual field can be seen clearly is about 20 inches. For a child, that field is reduced to just 2-3 inches. For a young adult the field is about at 4-6 inches, and for an 80-year-old? 60 inches. The greatest change in accommodation amplitude seems to occur between the third and fifth decade of life.
As we age, our lenses lose elasticity, and thus, we are unable to focus on near field objects as clearly as we when we were young. Tasks such as threading a needle or reading label ingredients on personal care products or food cartons become next to impossible without magnifying glasses.
To test for near field accommodation, schedule an appointment with Dr. Tod Davis Developmental Optometry & Vision Therapy Services. Dr. Davis has been treating patients and helping them work through vision disorders with vision therapy programs for over 25 years in Easter Virginia.