Accommodation is the ability to shift visual attention from one viewing distance to another and to keep clear focus. The ciliary muscle is responsible for this. The young human eye can change focus from distance (infinity) to 6.7 cm from the eye in 350 milliseconds. The change of the focal power of the eye is 15 diopters (the reciprocal of focal length in metres).
When a person accommodates to a near object, he/she also converges the eyes and, as a result, constricts the pupils. However, the constriction of the pupils is not part of the process called lens accommodation. The combination of these three movements (accommodation, convergence and miosis) is under the control of the Edinger-Westphal nucleus and is referred to as the near triad, or accommodation reflex.
A majority of school children with learning difficulties (according to some studies up to 96%) will show some form of vision problems, particularly with accommodation.
During a regular school day a child needs to facilitate accommodation, to shift focus, to various viewing distances and it is expected from them, it's taken for granted. But as we see, a very high percentage of the children with learning difficulties are not able to that activity well. Again, a majority of them thinks that this is normal, and that it probably happens to everyone.
problems copying off the board
lose place while copying
takes more time than others
The parents are frequently very surprised when children confirm after being asked about the blurred vision when looking at the white board and then at the note book; particularly by the fact that they forget what they just have seen on the board.
HOW DO WE SEE THAT A CHILD HAS PROBLEMS WITH THIS?
Children with reduced ability to facilitate a change of focusing distance will experience problems with copying off the board, it will take them a very long time to clearly focus their eyes while looking at the white-board and then at the note book, very often they lose their place while copying. In addition, often their handwriting might appear sloppy (big letters, small letters, above and below the lines). Frequently, they need more time to accomplish tasks than the majority of children in their class.
Accommodative Insufficiency: Inability of an eye to focus on the object, around 80% of children diagnosed with convergence insufficiency have compromised ocular accommodation.
Accommodative Infacility: inability to adjust focus at different viewing distance with enough speed and accuracy in red to achieve normal function
Spasm of accommodation: A condition in which the ciliary muscle of an eye remains in spasm - the eye can't relax in order to see distant objects. This could cause pseudo myopia or latent myopia.
ACCOMMODATION PROBLEMS IN ADULTS
Ocular accommodation physiologically declines in 5th decade of life dramatically and more and more often we see it earlier, sometimes at the beginning of the 4th decade due to today's lifestyle: Lots of near work, various screens, particularly tablets and smart phones when used for prolonged time affect the dynamic of the ciliary muscle greatly - and this in turn has great repercussions on our ability to accommodate various viewing distances.
There are quite a few studies and clinical randomised trials in recent years in order to get an insight into the efficacy of orthoptics in treatment of dysfunctional accommodation. Vision therapy/orthoptics is effective in improving accommodative amplitude and accommodative facility in school-age children with symptomatic convergence insufficiency and accommodative dysfunction.