Dr Ben Wild
Overview |
Our eye muscles are all interconnected in a complicated pathway with a common goal of delivering comfortable vision in any gaze and at any distance. To have comfortable near vision, the medial rectus muscles of each eye must pull the eyes inwards (converge the eyes) the appropriate amount, the pupils must shrink to help with depth of field, and the ciliary body, a muscle inside the eye, must constrict to change the shape of the lens inside the eye to focus the light from the near target on the retina.
Sagittal view of an eye with the ciliary body highlighted.
Accommodative insufficiency refers to the inability of the ciliary body to constrict, thereby allowing the lens inside the eye to change shape, leading to blurry vision at near. Sometimes, the ciliary body tries so hard to constrict at near, that it spasms and actually causes distance blur instead of near blur. This is not to be confused with presbyopia that occurs in everybody in early to mid 40s. Presbyopia refers to the natural ageing and stiffening of the lens with what is thought to be a fully functioning ciliary body. It also results in difficulty with near vision.
Signs and Symptoms |
Signs
Inability to change focal distance (near to far or vice-versa), takes longer to change focus.
Symptoms
Blurred vision, holding reading materials further away, avoiding near work, eye fatigue, eye strain, headaches, decreased reading comprehension, words moving on a page, skipping words, inability to change focal distance (near to far or vice-versa), takes longer to change focus.
Causes and Risk Factors |
Causes
The causes are unknown.
Risk Factors
Concussion, traumatic brain injury, convergence insufficiency.
Prevention and Treatment |
Prevention
Allow children to crawl and develop their near vision, avoid head trauma, apply the 20-20-20 rule (after 20 minutes of near work look at a target at least 20 feet away for 20 seconds).
Treatments
· Vision therapy including eye exercises that stimulate gradual accommodation (pencil push ups, Brock string, etc.), jump accommodation (Brock string, Hart Chart, etc.), lens training to simulate change in focal distance, computer-based training, in office-based training, and many more.
· Seek out an optometrist who specializes in vision therapy.
· Digital lenses with a small amount of reading power at the bottom of the lens.
· Bifocals.
Prognosis |
Vision therapy can be effective in strengthening the ciliary body so that it can constrict and relax more efficiently and more timely. This can reduce some, if not all, symptoms of accommodative insufficiency. Vision therapy takes allot of dedication. For a more immediate remedy, try the 20-20-20 rule and/or the digital lens design or bifocals.