Squint

Squint (strabismus) is the name given to usually persistent or regularly occurring misalignment of the eyes. Around 150,000 fellow citizens suffer from a squint. They suffer not only from the frequently disfiguring externally visible abnormality, the visual impairment associated with squint is an even greater burden. Squint is not just a blemish but often a severe visual impairment.

The earlier a child develops a squint and the later it can be treated by a doctor, the worse the visual impairment will be. By the time the child reaches school age, the prospects of successful treatment decline dramatically. Babies and small children with a squint should be treated at the earliest possible moment.

The effect of a squint on vision

In order that we can correctly perceive the space around us our two eyes must look in the same direction. This causes almost identical images to be generated in each eye. These two images are then fused together in the brain to form a single three-dimensional visual impression. If a squint is present the difference between the two images caused by the misalignment is too great and the brain is unable to converge them. The result is irritating double vision. The juvenile brain is able to respond to double images by simply suppressing the image arriving from the deviant eye.

This process generally has calamitous consequences: vision in the unused eye gradually becomes weak (amblyopic). Amblyopia is the name used to describe weak vision in an otherwise organically healthy eye. In the absence of treatment almost 90% of all children who suffer from a squint develop amblyopia on one side. If this squint-related visual weakness is not detected and treated in good time it will remain a lifelong affliction.

The child will then never learn to see with both eyes or even have three-dimensional vision. He or she will be at greater risk of accidents and restricted in career choice. Prompt treatment can almost always prevent or cure amblyopia and sometimes also produce good spatial vision.

How babies see and learn to see

Babies are able to perceive their environment through their eyes quite soon after birth - but only indistinctly. Visual acuity still has to be developed through constant exercise. Only a limited period is available for this purpose. By the time school age is reached, the eyes’ learning program is virtually complete. The old adage that “what you don't learn as a child, you'll never learn as an adult” applies to eyesight, too.

n the first weeks of life a child is still unable to coordinate the movements of the two eyes. Brief misalignments during this time are no cause for concern. They may also occur occasionally again in the course of the coming months. The ability to gaze also has to be learnt. If one eye constantly deviates from the direction of the other, there is no time to loose. The ophthalmologist can diagnose the problem even in infancy and will initiate the treatment at the right time.

The various forms of squint

When a squint is present, one eye deviates from the direction of gaze of the other. The deviation can be so small as to escape the attention of even the most observant parent. Often the same eye squints because it has the poorer visual acuity or lesser mobility.

The ophthalmologist describes this as a one sided (monolateral) squint. If both eyes are equal an alternating squint is present. The squinting eye can deviate from the non-squinting eye in various directions: inward (cross-eye, or esotropia), outward (walleye, or exotropia), upward (hypertropia) or downward (hypotropia) or by rotating on the optical axis (torsional strabismus). It is not uncommon for a child to have deviations in different directions at the same time.

Latent squint can only be proved when the binocular vision is restricted by covering an eye or in some similar manner. Latent squints can trigger headaches and disinclination to read in school-age children. If a misalignment in any direction is repeated or continuously present, this is known as a manifest squint. Manifest squints also include micro-squints - as a general rule on one side and directed inward. These are so slight that the parents do not recognize it or find it cute.

Squinting is never harmless or simply cute, it will not go away by itself but cause a one-sided visual weakness and severe problems with binocular and especially three-dimensional vision, if there is any delay seeking the necessary ophthalmological treatment.

The origin of a squint

Squints have many causes. The fact that squints occur frequently in some families leads to the conclusion that there may at least be a hereditary predisposition. Above all, in cases where one parent has a squint or has been treated for squint, the child should be taken to the ophthalmologist during the first year of life. Frequently, however, the misalignment remains a one-off case in the family from which boys are as likely to be affected as girls. In addition, risk factors to which the child is exposed during pregnancy or birth can cause squints.

In many cases the cause can be found in the eye itself, e.g. congenital unbalanced refractive errors, one-sided lens cataracts, tumors in the eye or injuries. Even with congenital causes the squint is not necessarily visible immediately after birth. With congenital refractive errors a squint only becomes apparent when the child begins to fix its gaze more precisely. At this point the child exclusively uses the functionally better eye, with the consequence that weak vision develops in the poorer eye (amblyopia), unless it is “trained” by additional ophthalmological measures. Sometimes an “acquired” misalignment also appears suddenly e.g. during children’s diseases, with a high temperature, after accidents - such as concussion, cataract or retinal detachment - but also during severe psychological crises.

Early or warning signals with squint

Children with conspicious squint have the best prospects because they are taken to the ophthalmologist in good time by their parents on account of the "blemish". Unfortunately the number of barely visible or invisible deviations are in the majority. They are only detected when one eye is already amblyopic - such as during the eye test on starting school, when it is generally too late for successful treatment. For this reason alone 4% of our fellow citizens suffer from serious one-sided visual deficiency. It is therefore very important to know and to heed all characteristics that might indicate an impending or existing squint:

sensitivity to light, tears, squeezing one eye shut, bad mood or irritability, chronic blepharitis, head held to one side and clumsy motion are alarm signals. Each sign is a valid reason in its own right to obtain an ophthalmologist’s opinion immediately.

If the deviation is not too small, you can identify a squint in your baby as follows: stand with your back to the window or under a ceiling light. Hold your baby in front of you, so that his eyes are facing the light. On the corneas you will see small mirror images of the window or the ceiling lamp. The mirror images in both eyes should correspond in position on both pupils. If one mirror image is out of place, tell your ophthalmologist your observation immediately.

How do you know that an eye is becoming amblyopic?

Unfortunately a lay person is unable to recognize a one-sided visual weakness without squint in small children. Even the medical check-ups that all small children are entitled to have by law unfortunately could not pick up existing problems in every case. This is due on the one hand to the fact that far from all parents make use of this service, and on the other that none of these examinations take place in an ophthalmological practice, which offers the best prerequisites for identifying amblyopia even in infants and small children.

The care measures with eye examinations proposed on starting kindergarten also come a bit too late for very early onset amblyopia. All parents are therefore urged to take advantage of all medical check-ups available and, in addition, to take their child to the ophthalmologist when it is two years old.

Treatment of squint

First the ophthalmologist determines the cause of the squint. Cross-eye that only develops in the second year of life or later, is caused by uncorrected defective vision in more than half of the children. As a general rule this involves a significant degree of farsightedness. Many of these children are cured of squint by the right glasses, with others it is at least reduced. Sometimes an attempt must be made to treat a child suffering from a squint with glasses as early as in its second year.

Amblyopia treatment

Occlusion treatment in which a sticking plaster is applied alternately over the squinting and normal eyes in a specific rhythm as instructed by the ophthalmologist serves to prevent as well as combat the amblyopia. The plaster covering on the normal eye is intended to have the effect of exercising the squinting eye. Changing over the plaster prevents weak vision in the normal eye caused by the occlusion. If a child cannot get along with the skin plaster treatment, the ophthalmologist will prescribe eye drops or ointment, which is applied to the normal eye in accordance with a fixed schedule. This dilates the pupil of the better eye; the inner eye muscles are temporarily relaxed, so that the child primarily uses the squinting eye thus exercising it.

The main prerequisite for the success of the amblyopia treatment is strict adherence to the treatment / exercise phases for the squinting eye and the normal eye that have been precisely determined by the ophthalmologist in every single case. If glasses, occlusion and eye-drops / ointment do not result in an improvement in visual acuity in older pre-school children and younger school children with amblyopia a training program prescribed by the ophthalmologist can occasionally provide further help. The amblyopia check-ups and treatment must generally be continued over a period of years into the growth phase, in addition to glasses and even after a successful operation. The skin plaster can often be replaced by an occlusion over a spectacle lens.

The squint operation

Half of the children with a squint need correction of the faulty alignment by means of an operation on the outer eye muscles. Sometimes the operative positional correction is a prerequisite for all other measures. As a general rule the operation is only carried out when the child wears glasses reliably, can see more or less equally well in both eyes and can be adequately examined (normally shortly before starting school). The operation does not eliminate the weak vision, neither does it produce an immediate improvement in spatial vision. Both generally require further ophthalmic treatment.

The operation does not eliminate the need for glasses, because they are the only means of correcting refractive errors. Squint operations are low-risk and have good prospects of success. They are carried out on the children under general anaesthetic by the ophthalmologist i.e. following the sedative injection the child feels nothing more of the procedure. There is of course a reaction from the operated eye, especially in response to eye movements, for around 48 hours after coming round from the anaesthetic but this is not so as to be unbearable. The eye is not removed or cut open during the operation. The ophthalmologist solely opens the rapidly healing conjunctiva in order to regulate the eye muscle. The type of misalignment and the result of the preliminary treatment determine whether a single operation is sufficient.

Co-operation between the parents and the ophthalmologist

With the exception of the operation, the ophthalmologist can only succeed with the other therapeutic measures, if the parents can be relied upon to co-operate. The ophthalmologist must be able to rely on the prescribed glasses being worn without exception and at all times by the child, that in the case of occlusion treatment, skin or glasses plaster do not remain on the eye longer than prescribed, nor are they simply removed “now and again” or too early, that eye drops and ointment are administered exactly according to plan and that no appointment – whether for a check-up or for training – is omitted.

The treatment of an amblyopia can last until the 12th year and sometimes beyond, because relapses are possible up to the final growth period. Your ophthalmologist knows that you and your child need great patience. He will support you in every way: medically, psychologically and through in-depth exchange of information.