What is Accommodative Excess?
The human eye has a remarkable ability to adjust its structure to see objects at different distances. This process is known as accommodation. Sometimes, issues can occur with this process, known as accommodative dysfunction, which is common in children, even if they don’t have other vision or eye alignment issues. This dysfunction could be either accommodative insufficiency or accommodative excess.
Accommodative excess refers to a situation where a person’s eye makes more effort than needed to focus on an object at a certain distance, or when the eyes struggle to stop focusing. Another related issue is what’s called a spasm of accommodation or accommodative spasm. This term describes a continuous tightening of the eye’s focusing muscle, which can trick the eyes into thinking they’re nearsighted, also known as pseudomyopia.
Both of these conditions fall within the same category and share similar symptoms – unclear vision (especially after looking at something up close for a long time), a hard time switching focus from near to far, and even headaches and eye discomfort. In fact, the symptoms are almost always present. If you come across these symptoms, it’s likely due to an excessive focus issue or pseudomyopia.
What Causes Accommodative Excess?
Excessive Eye Focus
Spending too much time doing activities up close is a primary reason for overuse of the eye’s focusing ability. Here are other reasons this may happen:
* Young people with farsightedness can overuse their eye’s focusing ability to see clearly without glasses.
* Young nearsighted individuals who spend a lot of time doing up-close work can also overuse their focusing ability, causing unnecessary eye strain.
* An uneven shape of the eye (astigmatism) in young people can also lead to overuse of focusing.
* Older individuals with weaker eye focus (presbyopia) may overuse their eye’s focusing ability to see clearly for close-up activities.
Eye Focus Spasm
This is when a child with an eye condition that affects their vision (farsightedness, astigmatism, or sometimes short-sightedness) experiences sudden tightening of the eye’s focusing muscles. It can happen in one or both eyes. These children often do a lot of close-up work in poor conditions, such as low lighting, or when experiencing emotional stress or anxiety.
Overactivity of the part of the nervous system that controls the body’s rest and digest functions (parasympathetic nervous system) is also linked to muscle fatigue, excessive eye focus, eye strain, and small pupils. This condition is known as the near reflex spasm (NRS).
Various things can trigger this condition:
* Eye drops and medicines that mimic the rest and digest nervous system actions, like pilocarpine
* A muscular weakness condition called Myasthenia gravis
* Emotional factors like anxiety
* Following eye surgery, such as laser eye surgery (LASIK) and PRK
* Head injuries
* Opioid use disorder
Certain drugs like sulphonamides and antipsychotics like haloperidol and biperiden, can also trigger a negative reaction causing this condition.
Risk Factors and Frequency for Accommodative Excess
Research has been conducted regarding a condition called accommodative dysfunction, which affects vision. This is commonly studied in groups of people who do not have eye turn (strabismus) or age-related loss of close vision (presbyopia). However, only a few studies exist on another vision condition called accommodative excess.
- A study in South Africa found a prevalence of 2.8% among students aged 13 to 19 years.
- In a study with university students, 10.8% had accommodative excess, while 32.3% had binocular dysfunction, another vision problem involving both eyes.
- An Indian survey done on children and teenagers from 7-17 years of age revealed 0.8% of them had accommodative excess in rural schools.
- In 2019, a study on males with opioid use disorder in Iran found a 3.75% prevalence of accommodative excess.
Signs and Symptoms of Accommodative Excess
It’s crucial to understand the signs and symptoms of excessive eye strain, also known as “accommodative excess.” Medical professionals often see this occur when the eyes are overworked from activities like reading or staring at a computer screen for too long. This condition is also known as “asthenopia.”
The common symptoms of accommodative excess include:
- Blurred vision, both close up and at a distance
- A connection to excessive near work
- Headaches
- Eyestrain
- Pain above the eye
- Eye deviation, also known as “esotropia”
- And sometimes double vision, or “diplopia”
In more severe cases, known as “spasms of accommodation,” the asthenopic symptoms are even more intense. Patients may notice size distortion due to optical illusions (macropsia). Both far and near points appear closer to the eye, and the pupil size may become smaller (miosis).
Testing for Accommodative Excess
In assessing cases with Accommodative Excess (AE), medical professionals often use a series of tests:
A) Vision testing: The clarity of a patient’s vision is checked in each eye separately and both together, both up close and at a distance, with and without corrective lenses. It’s important to note that some patients with AE may experience changeable vision.
B) Refraction testing: The eye’s ability to properly focus light is evaluated. An ideal method to do this is cycloplegic refraction which gets a more accurate measurement. People with AE, hyperopia, and astigmatism can adjust their ability to focus, making up for some vision defects.
C) Eye movement test: Doctors monitor how your eyes move and whether you’re having any difficulty looking in a particular direction. This helps them find any overactivity or underactivity in the eye muscles.
D) Cover test: This test is done to see if the eyes are aligned properly. If any eye deviation is seen, prism lenses may be used to correct it during the test.
E) Near point of convergence test: This test measures when the eyes’ ability to focus on a nearby object fails and the object appears double. This is important for evaluating binocular vision (how the eyes work together).
F) Amplitude of Accommodation test: This checks the lens’s flexibility in the eye. The more flexible the eye lens, the closer you can focus on objects clearly. This amplitude can be calculated for different ages using Hoffstetter’s equation, and can also be measured using the Donder’s push-up method and the minus lens methods, which involve focusing exercises and lens adjustments.
G) Relative accommodation test: This measures the changes in focus needed to clearly see an object at a specific distance when the eye convergence (inward movement of the eyes) is fixed. It can be either positive (focused) or negative (relaxed). Results from this test help to identify issues with focusing, like over- or under-focusing.
H) Accommodative Facility test: This checks the speed of changing the eye focus. In the clinic, this is measured by using an accommodative flipper, which contains pair of plus and minus lenses. The cycle of changing focus using both lens types is repeated and how many cycles completed per minute is recorded.
I) Monocular Estimated Method (MEM): This test is used to identify whether a patient’s focus is leading or lagging from where it should be. In a normal case, MEM values should be between +0.25D to +0.75D. If the values are less, it usually indicates accommodative excess.
J) Health assessments: A thorough check of the eyes and the overall systemic health of the patient is also important. This includes checking for exophthalmos and ptosis (eye disorders), media abnormalities (issues with light focusing components of the eye), and any retinal abnormalities. It also checks for systemic conditions like multiple sclerosis, diabetes, Graves disease, myasthenia gravis, and even the patient’s mental health.
K) MRI and CT scans: In cases involving head trauma, detailed imaging techniques like MRI or CT scans are needed to rule out other potential causes.
Treatment Options for Accommodative Excess
The strategy to manage over-active eye focusing (accommodative excess) centres on removing the cause – whether it’s functional or organic – and better eye care (visual hygiene). This is especially important in cases where the cause is functional.
There are different approaches to treating over-active eye focusing which include using eyeglasses, eye exercises (vision therapy), drugs, or a mix of these.
– Using eyeglasses: The first thing to consider to manage over-active eye focusing is correcting any present vision errors with the right spectacles. If these errors are not corrected, they can lead to eye focusing fatigue. This correction has to be done after a certain eye test (cycloplegic refraction). Furthermore, tasks needing close focus should be limited for some time. Patients with overactive eye focusing may not gain much from using positive lens glasses alone due to some specific factors. However, with the addition of specific medication, the positive lens glasses may aid near vision.
Eye exercises (Vision therapy, or VT): The goal of the eye exercises for patients with over-active eye focusing is to enhance the amount and quality of focusing. Commonly used methods to manage over-active eye focusing include alternating focus, certain eye charts, computer applications, and home exercises. The aim of these exercises is to normalize the amount of eye focus, then speed up the focusing response, and finally maintain normal focusing and the normal interaction between the eyes.
– Using drugs: One of the most effective approaches is to use certain medication (cycloplegic drugs) that relaxes the overactive eye focusing muscle. A specific drug (Atropine 1%) has shown better results than other similar drugs; but these can often cause eye discomfort and issues with near vision. These eye drops should be gradually reduced after using them for four weeks or switched to a less strong version.
What else can Accommodative Excess be?
When a person’s eyes have difficulty adjusting to different distances, a condition known as accommodating excess, it can sometimes be mistaken for nearsightedness (known as myopia) if testing isn’t properly conducted – in this case, if a procedure called cycloplegic refraction isn’t done. Accommodating excess can also be mistaken for a condition where both of the nerves that control horizontal movement of the eyes (bilateral sixth nerve palsy) aren’t functioning properly.
What to expect with Accommodative Excess
The best treatment approach includes cycloplegia of a specific eye muscle, therapy done at the doctor’s office, and at-home treatment. Patients who still have excess focusing power after successful treatment should see their doctor for check-ups every six months. Those who wear glasses should have check-ups every three to six months.
Possible Complications When Diagnosed with Accommodative Excess
If we don’t treat accommodation excess, it could result in a condition called accommodative esotropia.
Preventing Accommodative Excess
Excessive eye accommodation, or the eye’s ability to adjust its focus, isn’t just an issue about vision. It’s also associated with the nerves and muscles that control the eyes. Glasses aren’t the only solution; vision exercises, practicing good eye care habits, and mental health support can all be part of the treatment plan. People with this condition, especially those with false nearsightedness, might feel discouraged about wearing glasses. Parents might also feel unhappy if their kids are advised to wear glasses.
