In addition to refractive errors, the focus of our eyes and muscle coordination may be impacted by a range of Accommodative & Binocular Vision Conditions. Normal young eyes have a wide range of focus from far distance to a few centimetres with very minimal perceived effort. The change happens so quickly that we don't even realise our eye is refocusing! The lens inside the eye and the eye muscles controlling eye movement usually work with great flexibility and coordination. But when they don’t, they can result in a range of Accommodative (Focusing) and Binocular Vision conditions that can impact reading clarity and comfort.  

These visual skills are particularly important for learning. It’s estimated approximately 20% of those under 18 years have an Accommodative or Binocular vision (BV) condition. This includes Accommodative Infacility, Accommodative Spasm, Accommodative Insufficiency and Convergence Insufficiency.  

Accommodative Infacility

Accommodative infacility is the inability to change the focus (accommodation) of the eye with enough speed and accuracy to achieve clear and comfortable vision. This can lead to symptoms of fatigue, headaches, eyestrain, blurred vision and difficulty reading. Focusing problems are common, but the true prevalence of accommodative infacility is not known. Of those seeking care for focusing problems, one group of researchers found that 5.1% had accommodative infacility.  

Management options include advice on taking visual breaks, reading glasses, and Vision Training or Therapy to train your accommodative system.  

Accommodative Spasm

Accommodative Spasm (or Accommodative Dysfunction) is a condition that causes the eye muscle to accommodate or focus constantly and automatically. Someone with an accommodative spasm has a difficult time relaxing their focusing muscles when looking at a distance. A common example of this is when you’re concentrating on a close task, such as reading, and when you look up, your vision is blurry as your eyes are still focusing on the close-up or near task.  

As well as symptoms of blurred and fluctuating vision, you may have headaches, eye fatigue and trouble concentrating. 

It can be common during school and university but can also affect many doctors, medical technicians and scientists using instruments and microscopes.  

Management options also include advice on taking visual breaks, the use of reading glasses or progressive lenses, and Vision Training or Therapy to train your accommodative system.  

Accommodative Insufficiency

Accommodative Insufficiency is a condition that causes the eyes not to focus correctly on objects up close due to a reduced amount of focusing ability. 

Our ability to focus up close is linked to our age, and there is an expected range of near focus for all age groups. Your optometrist would call this your “amplitude of accommodation”. In Accommodative Insufficiency, the amount of focus is less than expected for your age. It is different from presbyopia, affecting younger age groups, but causes similar symptoms of blurred near vision, headaches, eyestrain, tired eyes and difficulty concentrating. 

Accommodative Insufficiency can also mean you can’t sustain your focus, and your focus can spasm. It can affect one or both eyes and affects about 2% of children. As our focus and eye muscle coordination are linked, it is also often seen in combination with Convergence Insufficiency.  

It occurs because of either premature lens stiffening or due to weakness of the muscle controlling your focus. This may occur because of diabetes, pregnancy, glandular fever, chronic fatigue, stress, malnutrition and some eye diseases. Some medications can also cause changes to your focus, as can head trauma, including concussion.  

Following an eye exam to help identify accommodation insufficiency and its specific cause, glasses and visual training/exercises may be recommended if treatment is needed.  

Convergence Insufficiency

Convergence is the term used to describe when both eyes look and turn inwards towards an object in front of us, such as a book or computer. The closer an object is, the more convergence is needed. Convergence Insufficiency is a sensory and neuromuscular anomaly where the eyes have a reduced ability to turn towards each other.  

It’s a very common condition and can cause symptoms of double vision, eyestrain, transient blurred vision and headaches, particularly with reading and other near vision tasks. As the eyes struggle to focus easily on near tasks, it affects schoolwork, attention span and office performance in adults. It can also affect hand-eye coordination.  

It is most commonly diagnosed in school-age children who may have difficulty reading, making them avoid reading or not complete school work. In this presentation, there is no known cause, but it can also occur in adults following concussion or traumatic brain injury.  

Like other binocular vision conditions, glasses and visual training/exercises may be recommended if treatment is needed. Visual training can be particularly effective in convergence insufficiency.  

Digital Eyestrain

It’s estimated the average kiwi adult spends 70% of their time indoors and nine hours a day staring at a screen. We can all agree there are many benefits to our digital lives, but constant screen time can take a toll on our visual system.  

What was once called “Computer Vision Syndrome” following the growing popularity of computers in the early 1990s is now termed “Digital Eye Strain”. The digital eye strain is defined as “a group of eye and vision-related problems that result from prolonged computer, tablet, e-reader and cell phone use”. Symptoms include tired eyes, headaches, dry eyes and blurry vision. It is suggested prevalence in adults is 50% or more, so the majority of us are struggling with some form of digital eye strain.  

The symptoms of digital eye strain can affect your comfort and visual clarity and the speed and ease at which you can do screen work, negatively affecting productivity.   

Refractive errors can impact digital Eye Strain. Uncorrected long-sight (hyperopia), astigmatism, presbyopia (age-related changes to near focus) and accommodative or binocular vision problems (focus or eye muscle alignment issues) all contribute to Digital Eye Strain symptoms.  

After a full eye exam, we can give you an individualised plan and advice to provide you with the best functionality and productivity at the computer. If glasses are recommended, some lens designs and coatings are better than others. 

Strabismus

Commonly referred to as an “eye turn” or being “cross-eyed”, strabismus is when one or both eyes do not look at the same place at the same time. 

This can be caused due to an in-balance in eye muscle control or poor vision in one or both eyes. Initially, this leads to double vision, as well as a lack of depth perception. To overcome the confusion, the brain shuts off the input from the non-dominant eye, causing it to become a “lazy” eye. Strabismus is often corrected by wearing spectacles that balance the vision in both eyes so that they are aligned correctly and see equally. If this fails, an additional correction can be incorporated into the lens called a prism. Permanent correction of the misalignment can be achieved with surgery which requires referral to an ophthalmologist.  

Amblyopia   

Amblyopia, or a lazy eye, is a common cause of poor vision in childhood and beyond. 

It occurs because part of the brain that deals with vision for that eye has failed to develop normally.  

The vision centre in the brain is constantly developing up to around the age of 7-8 years of age. If the vision during this so-called Developmental Period is interfered with in any way, the vision in one eye doesn’t develop to its full potential, and the brain starts to prefer one eye over another.  

Amblyopia most commonly occurs because of focus or eye alignment problems. Correcting these during the developmental period is the most effective way to manage Amblyopia.  

What causes it?  

Poor focusing problems can occur due to hyperopia (long-sight), myopia (short-sight) or astigmatism. Eye alignment problems, known as strabismus to your optometrist, is commonly known as a squint or eye turn. Both these conditions benefit from correction with glasses, and for eye turns, surgery may be beneficial.  

Less commonly, corneal scars on the eye surface, childhood cataracts and droopy eyelids can cause Amblyopia in childhood.  

Managing Amblyopia  

The first step to managing Amblyopia and improving the vision in the amblyopic eye is often well-fitting glasses. Your optometrist will monitor the effect this has in enhancing vision.  

If vision fails to improve quickly with glasses, the second step is patching the good eye for a certain number of hours per day. Again, frequent monitoring is key to ensure improvements occur. We can supply adhesive patches or patches that secure your child’s glasses.  

Patching when recommended is important but can be challenging. If your child is old enough to understand, discussing that it is making their eye stronger can help. A reward system or providing interesting activities during patching time can also help.  

Less commonly, another option to patching is Atropine Eyedrops. These blur the vision in the good eye. These drops only work in certain cases of Amblyopia and do make the child more light-sensitive because the pupil also gets larger.  

Early detection of Amblyopia is key! Beyond the developmental period, Amblyopia gets increasingly difficult to improve. Before-school vision screenings aim to detect Amblyopia, but a comprehensive eye examination goes further.