Eye Accommodation
Accommodation of the eye, or eye accommodation, is the eye’s extraordinary ability to modify the focal length of the lens by changing the curvature of the eye lens. Accommodation allows the eye to adjust focus from seeing things at a distance and “tune” itself to seeing nearer objects.
Similar to breathing or blinking, this process is a reflex action. It brings near objects into focus in three parts — thickening the lens, constricting the pupil and automatic inward rotation of the eyes (known as eye convergence).
What is Accommodation of the Eye?
To define accommodation of eye, we need to uncover the function of the eye’s lens and the action of the ciliary muscles (muscles that support the ligaments around your eye’s lens).
In resting state: The ciliary muscles are usually relaxed. During this time, the aqueous humour (spaced between the lens and the cornea) and vitreous humour (spaced between the lens and the retina) push outward on the sclerotic coat (the outermost membrane surrounding the eye), and the ligaments become tensed. This causes the lens to pull itself into a thin shape, resulting in a short focal length for distance vision.
Definition of accommodation of eye: When we need to see objects nearby, like a book or a smartphone screen, the ciliary muscles contract, so the ligaments pulling your lens taught relax, causing the lens to become more rounded and thicker. This adjustment enables your lens to refract light more powerfully and bring nearby objects into clear focus.
Process of Accommodation of Eye
The cornea (the transparent front part of the eye covering the iris and pupil), provides only 2/3 of the refractive power and the lens, 1/3 of it. However, it is our eye that changes the curvature of the lens during the accommodation process, and not the cornea.
Put simply, the cornea doesn’t naturally change shape. It is the changing of the thickness of the lens which lets you see longer or shorter distances.
But how does the eye accommodate? Here’s a breakdown of the process of visual accommodation:
The process of accommodation in the eye is a finely orchestrated dance between the ciliary muscles and the crystalline lens. Together, they ensure that you can shift your focus from distant vistas to up-close details, allowing clear and adaptable vision.
When we grow old, our lens will turn hard. Our accommodation ability will decrease and it will get more and more difficult to focus. This defect is called presbyopia.
Why Does the Eye Need to Accommodate?
The ciliary muscles, responsible for accommodation of the eye, are usually at rest. When at rest, parallel light rays that form distant objects converge onto the retina, giving you a sharp and clear view of the object.
If the eye were to remain in such a state of rest and an object placed nearer to it, the light rays would converge behind the retina. But then, since the sharp image is behind the retina, our brain will only detect a blurry image of the closer object.
Therefore, in order to bring that image of the closer object back into focus, the eye performs the process of accommodation.
Types of Accommodative Dysfunctions
A group of eye conditions collectively known as accommodative dysfunctions, can lead to challenges in focusing, eye strain, and discomfort.
Explore the types of accommodative dysfunctions, their distinct characteristics, and the impact they can have on vision:
1) Accommodative Infacility
Infacility is characterised by difficulties in smoothly transitioning between near and far vision. This condition can lead to eye strain, blurred vision, and reduced focus flexibility.
2) Accommodative Insufficiency
In cases of accommodative insufficiency, the eyes struggle to maintain focus, especially when looking at near objects for extended periods. Individuals may experience difficulty reading or working on tasks that require sustained close-up vision.
3) Accommodative Excess
Accommodative excess occurs when the eyes over-focus on near objects, making it challenging to shift focus to distant objects. This can lead to eye strain, blurred vision, and discomfort when trying to see things at a distance.
4) Accommodative Spasm (Accommodative Cramp)
Accommodative spasm involves a sudden, involuntary contraction of the ciliary muscles, which control the shape of the eye’s lens. This can result in blurred vision and difficulty adjusting focus. It may be temporary or chronic.
5) Accommodative Paresis (Accommodative Insufficiency)
Accommodative paresis is defined as a total loss of accommodation, in either one, or both eyes. The affected eye is unable to focus properly on an object.
6) Accommodative Vergence
This condition involves issues with the coordination of eye movements when adjusting focus. Individuals with accommodative vergence may experience double vision or eye strain.
Each type of accommodative dysfunction has its own set of symptoms and challenges, but they all involve difficulties in the eye’s ability to adjust focus effectively.
If you suspect you may have an accommodative dysfunction, consulting with an eye care professional is essential. They can diagnose the specific issue and recommend suitable treatments, which may include vision therapy, prescription lenses, or lifestyle adjustments.
Symptoms of Accommodative Infacility
Symptoms of accommodative infacility can vary from person to person, but they typically involve difficulties with focusing the eyes on near objects and transitioning between near and distant vision. Some common symptoms include:
Blurry Vision
Individuals with accommodative infacility often experience blurred vision, especially when trying to read or view objects up close.
Eye Strain
Prolonged periods of reading or performing tasks that require near vision can lead to eye strain. This can manifest as discomfort, fatigue, or aching around the eyes.
Headaches
Eye strain associated with accommodative infacility can sometimes lead to headaches, particularly around the forehead or temples.
Difficulty Shifting Focus
People with this condition may find it challenging to quickly shift their focus from near to distant objects or vice versa. This can impact activities like driving, where rapid changes in focus are necessary.
Loss of Concentration
Accommodative infacility can make it challenging to concentrate on tasks that involve frequent changes in focus, such as reading and computer work.
Slow Reading Speed
Some individuals may notice that their reading speed is slower than expected due to the need for extra time to adjust focus.
Double Vision
In some cases, accommodative infacility can lead to double vision or seeing multiple images of the same object.
It’s important to note that these symptoms may not always be exclusive to accommodative infacility and can overlap with other vision-related issues.
If you experience persistent vision problems or any of these symptoms, it’s advisable to consult an eye care professional as soon as possible for a comprehensive evaluation and diagnosis. They can provide personalised guidance and recommend appropriate treatments or vision therapies to address these symptoms sooner rather than later, before symptoms get worse or complications arise.
Treatment for Accommodative Infacility
Accommodative Infacility Exercises
Accommodative infacility exercises are vision therapy techniques designed to enhance the eye’s ability to adjust focus smoothly and efficiently. These exercises are often recommended for individuals experiencing eye strain or difficulties with tasks like reading or computer work.
1) One common exercise involves focusing on a near object and then quickly shifting focus to a distant one, repeating this process to improve the speed of accommodation.
2) Another technique may involve tracking moving objects to enhance convergence and divergence abilities.
Vision therapy, often administered by optometrists specialising in binocular vision, is tailored to an individual’s specific needs. To determine the most suitable treatment approach, a consultation with an eye care professional is essential.
Relation to Laser Eye Surgery
For individuals with accommodative infacility, LASIK (Laser-Assisted In Situ Keratomileusis), a type of refractive surgery, can provide an immediate and long lasting solution. Refractive surgery is used to correct eyesight and restore near-perfect vision. LASIK is a surgical technique that corrects a person’s vision, reducing the need for spectacles or contact lenses. Known as Laser Assisted in Situ Keratomileusis or LASIK, the surgery involves changing the shape of the cornea.
Refractive surgery primarily targets refractive errors and may not directly treat accommodative infacility. However, by improving visual clarity, it can reduce eye strain associated with accommodative difficulties, especially during close-up tasks.
Refractive surgery can also be used to treat presbyopia. Monovision or laser blended vision is used to provide the patient with good vision for both near and distance. It is a very effective way of combating the loss of accommodation in later life.
Conclusion
To sum up the main points on this page:
- Accommodation occurs when the eye automatically adjusts its focus for short vision.
- During accommodation, the ciliary muscles contract, the supporting ligaments relax, and crystalline lens of your eye becomes thicker — focusing your vision for nearby objects.
- Several types of accommodative dysfunction can be remedied through at-home vision therapy designed to improve the overall accommodative function of the eyes.
- LASIK can be a lasting solution for those with refractive errors contributing to accommodative dysfunction.
- Consult with an eye care specialist for a comprehensive assessment to guide you toward the most effective treatment plan for your specific condition.
If you’d like to know more about your visual condition or what treatment options are available for you, call and speak to our specialist team here. They will provide you with personalised advice to best manage your vision.
