Binocular vision is one of the hallmarks of the human race that has bestowed on it the supremacy in the hierarchy of the animal kingdom. It is an asset with normal alignment of the two eyes, but becomes a liability when the alignment is lost.
Binocular Single Vision may be defined as the state of simultaneous vision, which is achieved by the coordinated use of both eyes, so that separate and slightly dissimilar images arising in each eye are appreciated as a single image by the process of fusion. Thus binocular vision implies fusion, the blending of sight from the two eyes to form a single percept.
Binocular Vision requires
1) Clear Vision in both eyes
2) Motor Fusion (both eyes aligned to look at an object)
3) Sensory Fusion ( Brain fuses two slightly different vision into one)
Common Binocular Vision anomalies often missed in Children
1) Convergence Insufficiency
CI is the inability to obtain or maintain sufficient convergence for comfortable binocular vision for close work. Occasionally, they may develop into an intermittent outward squint when fatigued. Subject will usually complain of frontal headaches or poor concentration at close work.
2) Convergence Excess
It is the condition where the eyes over converge while reading. The main symptoms are frontal tension headache, often accompanied with transient blurred vision for far distance after a period of close up work. In children, it often goes wrongly diagnosed at an increase in myopia. Children with convergence excess in combination with high accommodative-convergence ratio is also likely to be at risk for progressive myopia without the right lenses or visual therapy
3) Accommodative infacility
The inability of the ciliary muscles within both eyes to change focus from far to near and/or vice versa. This condition usually is co-existent with convergence excess. The symptoms may also be very similar,where the child may complain of transient blurred vision at distance after a period of close reading
4) Divergence excess
This condition usually manifest in children where the eye muscles tend to over divergence while looking far. The signs are usually that the child’s eyes may intermittently turn outward while day dreaming or when fatigued.
How can parents detect such anomalies?
Depending on the severity of the condition, some of it can go often undetected with minimal symptoms. The child may also commonly complain of sleepiness, fatigue or headache after prolonged close up work or transient blurred vision. An optometrist who is trained in Binocular vision is able to perform an assessment to detect such anomalies. He/She is then able to recommend certain visual therapy or special lenses to help assist you child in his vision.
So do not dismiss your child’s complains of headaches or tiredness as plain laziness. Perhaps there is something more to it that can be done. As parents, it is our prerogative to ensure that their health and well being is being taken care of. So do the right thing, bring your child to visit an optometrist today.
*Patrick & Linda @ Precision Optics rountinely perform binocular vision assessment on kids and adults to ensure that you get the best out of both your eyes. Consultation (Usual $35) is waived for children between the age of 5 to 12.
Precision Optics @ United Square 