Children's Eye Conditions
Lazy Eye (amblyopia)
What is amblyopia?
Amblyopia is poor vision in an eye that did not develop normal sight during early childhood. It is commonly called ‘lazy eye’.
When one eye develops normal vision while the other does not, the eye with poor vision is called amblyopic. Usually, only one eye is affected by amblyopia, but it is possible for both eyes to be ‘lazy’.
This condition is quite common, affecting approximately two or three out of every 100 people. The best time to correct amblyopia is during infancy or early childhood.
If a child cannot use his or her eyes normally, vision does not develop properly and may even decrease. After the first nine years of life, the visual system is normally fully developed and usually cannot be changed.
The development of equal vision in both eyes is necessary for normal vision. If the vision in one eye should be lost later in life from an accident or illness, it is essential that the other eye have normal vision. For these reasons, amblyopia must be detected and treated as early as possible.
What causes amblyopia?
Amblyopia is caused by any condition that affects normal use of the eyes and visual development. In many cases, the conditions associated with amblyopia may be inherited. Amblyopia has three major causes:
1. Strabismus (squint or misaligned eyes)
Amblyopia occurs most commonly with misaligned or crossed eyes. The crossed eye ‘turns off’ to avoid double vision, and the child uses only the better eye. The misaligned eye then fails to develop normal vision.
2. Unequal focus and refractive errors
Refractive errors are eye conditions that are corrected by wearing glasses. Amblyopia occurs when one eye is out of focus because it is more nearsighted, farsighted or astigmatic than the other.
The unfocused (blurred) eye ‘turns off’ and becomes amblyopic. The eyes can look normal, but one eye has poor vision. This is the most difficult type of amblyopia to detect since the child appears to have normal vision when both eyes are open.
Amblyopia can also occur in both eyes if both eyes have very blurred vision. This can happen when there is a high amount of nearsightedness, farsightedness or astigmatism (irregularity of the focus).
3. Cloudiness of normally clear inner eye structures
An eye disease such as a cataract (a clouding of the eye’s naturally clear lens) may lead to amblyopia. Any factor that prevents a clear image from being focused inside the eye can lead to the development of amblyopia in a child. This is often the most severe form of amblyopia.
How is amblyopia diagnosed?
It is not easy to recognise amblyopia. A child may not be aware of having one strong eye and one weak eye. Unless the child has a misaligned eye or other obvious abnormality, there is often no way for parents to tell that something is wrong.
Amblyopia is detected by finding a difference in vision between the two eyes or poor vision in both eyes. Since it is difficult to measure vision in young children, your ophthalmologist often estimates visual acuity by watching how well a baby follows objects with one eye when the other eye is covered.
Using a variety of tests, the ophthalmologist observes the reactions of the baby when one eye is covered. If one eye is amblyopic and the good eye is covered, the baby may attempt to look around the patch, try to pull it off or cry.
Poor vision in one eye does not always mean that a child has amblyopia. Vision can often be improved by prescribing glasses for a child.
At Eye Doctors, we will also carefully examine the interior of the eye to see if other eye diseases may be causing decreased vision. These diseases can include cataracts, inflammations, tumors and other disorders of the inner eye such as retinal dystrophy.
How is amblyopia treated?
To correct amblyopia, a child must be made to use the weak eye. This is usually done by covering or blurring the strong eye for weeks or months.
Glasses may be prescribed to correct errors in focusing. If glasses alone do not improve vision, then patching is necessary.
Amblyopia may also be treated by blurring the vision in the good eye with special eyedrops or glasses to force the child to use the amblyopic eye.
If there is a cataract or other abnormality, surgery may be required to correct the problem. An intraocular lens may be implanted. After surgery, glasses or contact lenses can be used to restore focus while patching improves vision.
Early detection and treatment
If the amblyopia is detected and treated early, most children will gain improved vision. Amblyopia caused by squints or unequal refractive errors may be treated successfully during the first nine years of age. After this time, amblyopia does not normally recur.
If amblyopia is not detected until after early childhood, treatment may not be successful. Amblyopia caused by cloudiness of the eye tissue needs to be detected and treated extremely early, within the first few months of life, in order to be treated successfully.
If you have additional questions or would like any further information, contact your ophthalmologist at Eye Doctors.
What is strabismus?
Strabismus (commonly known as squints) is a visual defect in which the eyes are misaligned and point in different directions. One eye may look straight ahead, while the other eye turns inward, outward, upward or downward.
The eye turn may be constant, or it may come and go. Which eye is straight (and which is misaligned) may switch or alternate.
About 3-4% of all children are born with squints making it a common condition in New Zealand. Squints occur equally in males and females. They may run in families, however, many people with squints have no relatives with the condition.
What causes squints?
The exact cause is not fully understood. Any factors influcencing the brain’s control of binocular vision, or the eye muscle functions can cause it. Occasionally children with down syndrome, brain tumor’s or infections can present with squints.
What are the indications of squints?
The main indication is that an eye is not straight. Sometimes the child may squint an eye to see, or tilt their head to see. Favouring one eye over the other can lead to amblyopia (lazy eye) which will lead to long term poor sight in that eye.
What is Pseudoesotropia?
The eye of an infant appears to be crossed, though they actually are not. This is often due to a wide, flat nose, or a fold of skin in the inner lids making the eyes appear crossed. Children often grow out of the pseudoesotropia but they never grow out of a true esotropia. Our Paediatric Ophthalmologist Dr Shuan Dai will help you make the correct diagnosis.
The most common types of squints in children are:
- Infantile esotropia
Infantile esotropia, where the eye turns inward, is the most common type of squint in infants and it usually occurs between 3-6 months of age. The correct treatment for infantile esotropia is early intervention with surgery. This restores eyes to their normal alignment and it also gives the child a better chance to develop the ability to use two eyes together( 3D vision).
- Accommodative esotropia
Accommodative esotropia is a common form of squint and often occurs in children two years of age, or older. The eye turns inward due to excessive use of accommodative effort for better vision. It can present when the child is looking at distant or near objects. Often the children with this condition are farsighted, wearing appropriate corrective glasses helps with the control of misalignment. Sometimes children will need eye muscle surgery to correct the misalignment.
Exotropia refers to the outward turning of the eye. This type of squint more often occurs when the child is looking at far distance objects though it can occur for any distance of visual fixation. It becomes more noticable when the child is tired, or sick. Exotropia often needs surgical correction if it becomes constant, or noticeable for most of the time during the day.
Exotropia - outward turning of the eye
How are squints treated in children?
After a complete medical eye examination the child may be prescribed glasses as a treatment for the squint and also more importantly to improve the child’s vision.
If glasses cannot control the squint, or are not needed then eye muscle surgery will be recommended to restore normal alignment and binocular vision.
How is squint surgery performed on children?
Squint surgery on children is carried out as a day stay procedure performed under a general anesthetic. Our anesthetists are experienced in children’s anesthesia and surgery is performed in a fully equipped private hospital where all recovery facilities and expertise are available.
The eye muscle causing the eye to turn inward, or outward is ‘loosened’, or ‘tightened’ as required. The eyes are not normally patched and recovery is fast so the child can resume normal activities within a few days.
A child with divergent squints pre-surgery.
When should treatment start?
Children suspected of a squint should be seen without delay by a specialist. No child is too young to be seen and for treatment options to be discussed.
Myopia, commonly called near-sightedness, is the most common human eye disorder in the world, affecting 85% to 90% of young adults in some Asian countries such as Singapore and Taiwan,and between 25% and 50% of older adults in the United States and Europe.