Squint surgery

Squint surgery - characteristics

The eyeball is held in the correct, original position in the eye socket by means of an equivalent cooperation of the extraocular muscles of the eye. The movement apparatus of the eyeball consists of four straight muscles (upper, lower, external and internal) and two oblique muscles (oblique upper and oblique lower), which have their trailers within the ring of the tendon eye - with the exception of the oblique muscle attached to the lacrimal bone. They are venerated by the appropriate cranial nerves - coelomic, circulatory and abductive.
When any of the extraocular muscles weakens, the eyeball disorder may appear to be in the original position, i.e. a squint disease with a different angle of deviation - depending on the difference in the strength of the muscles acting antagonistically to each other. To allow correct binocular vision, i.e. the ability to perceive images falling on the retina of both eyes as a single, coherent, distinct three-dimensional image, three conditions must be met:
• correct visual acuity of both eyes,
• the ability to fuse the image in the visual fields,
• simultaneous coordination of eye movement in all directions of the gaze.
The squint is not, as it may seem, only an aesthetic defect. Squint consists in the incorrect setting of the visual axis of the eyes, resulting in the appearance of splinters, scars in front of the eyes, and deepening of the amblyopia. Blunt disease can occur in children and adults, and the earlier the onset of squinting, the more likely it will be a surgical correction. In some cases, it is sufficient to correct the refractive error and the use of prismatic lenses. Correction of surgical strabismus is usually not carried out without prior correction of refractive error.
The simplest test to assess the angle of the squint deflection is the Hirschberg test, which consists of simultaneously illuminating the eyes with a flashlight and observing reflexes (light reflection) on the corneal surface - in the eyes of healthy reflections should be symmetrical and returned slightly nasally. When one of the eyes squints, the corneal reflexes are not symmetrical. It sometimes happens that a seemingly squinting patient has symmetrical corneal reflections - we are talking about a purplish eyelid, which may be caused, for example, by a wide base of the nose or a distinct wrinkle of the diagonal eye. Such strabismus is not treated surgically.

Squint surgery - benefits

The goal of squint is to restore the incorrectly positioned eyeballs to the original position (straight ahead) and to restore the correct binocular vision. Thanks to the squint surgery we gain, apart from the aesthetic effect:
• resignation of split
• improving the sense of depth of the image
• improvement in visual acuity
• correct eye accommodation
• resolution of nystagmus
• equalizing the strength of the eye muscles
• correction of the forced head position
• improvement of self-esteem and well-being

Squint surgery - indications for surgery

Indications for squint surgery t are set individually because there are many types of squint. Some types of squints can be corrected only with optical methods or appropriate visual exercises, so an individual consultation with an ophthalmologist-, a specialist for the treatment of squint. is indispensable. In fact, surgery requires about 25% of squint cases. Certainly, however, surgical treatment is proposed for congenital or cross-over the slightly older children. Surgical treatment of adults, of course, is also possible, because such a procedure can, contrary to popular opinion, be carried out at any age. Generally, surgical treatment is proposed when the angle of the squint is large, early squint, squint has traumatic background (e.g. blow-out orbital fracture) and inoperable solutions have no effect or the patient prefers to abandon them in favour of a faster surgical procedure.

Contraindications for the treatment

The contraindications to the operation of squint surgery can include:
• poor general condition of the patient
• poorly controlled diabetes (prolongs the healing of post-operative wounds and increases the risk of infection)
• coagulation disorders
• pregnancy (as the surgical correction of squint is not an urgent procedure, it is recommended to perform such surgery after delivery, if necessary)
• hypersensitivity to the agents used to perform general anaesthesia

Squint surgery – before the procedure

It should be remembered that surgery is not the only way to correct strabismus. With proper optical treatment with the use of corrective glasses, the refractive error and prisms as well as the visual exercises - like the covering of the leading eye (healthy) - can greatly correct the disadvantage. However, this requires patient patience and commitment.
The surgery itself, however, is not a guarantee of complete eyebrow correction - it happens, just like for example in the correction of high myopia, non-correction or over-correction of the defect.

Type of anaesthetic

Anaesthesia for any surgical procedure obviously depends on the extent
planned operation, but it can be:
• general - during this type of anaesthesia pain, reflexes and patient's awareness are suppressed. General premedication requires proper premedication - administration of substances that will reduce anxiety and fear of surgery, inhibit the secretion of saliva and bronchial content, cause retrograde amnesia, and also enable reducing the doses required for proper anaesthesia.
• ductal - anaesthesia is given to stop the conduction in the sensory nerves, the patient has no pain and reflexes but is aware of the course of the operation;
• local - when an anaesthetic is used to justify the operated area.
Surgical correction of squinting is performed under general anaesthesia. General anaesthesia is considered to be a safe procedure for the majority of patients and used for a wide range of surgical procedures, however there are certain risk groups that are more likely to have intraoperative complications - such as obese people with coagulation disorders, poorly controlled diabetes, breathing disorders, hypertension. However, these are rarely complications related directly to anaesthesia (unless there have been no adverse reactions after administration of anaesthesia), but rather to the patient's own health condition. The risk of subjecting the patient general anaesthesia, of course, remains to be evaluated by the attending physician and anaesthesiologist.

How is the procedure performed?

Operations to improve eyeball settings can be technically divided into:
• strengthening, which strengthen the strength and tension of individual muscles
• weakening, which will reduce the strength and tension of the muscles
• treatments that change the direction of muscle activity
Strengthening treatments may involve resection (shortening) of the muscle, which will increase its potency. This procedure is performed on the simple eyeball muscles. The muscle is exposed, the absorbable seams are sewn backwards from the attachment, then the muscle part is cut off, and the stump is sewn into the place where the trailers originally were. In the case of IV cranial nerve paralysis, muscle folding can be performed to shorten it, this applies to the oblique upper muscle.
By strengthening treatments, you can also make corrections in the case of previously excessively weakened muscle.
Treatments that weaken muscle strength can be done by retracting the muscle, its marginal incision, cutting off and putting on the back fixation stitches. Recession, i.e. muscle retraction, can be performed on all eyeball muscles, both straight and oblique. After the muscle is exposed and the absorbable sutures are placed on it, the tendon is removed from the sclera and sewn backwards from the original attachment. Marginal incision is used when we want to weaken the muscle that has been retracted too far. This is done without changing its attachment, the incision allows changing its length. Sometimes, when the lower oblique muscle is overactive, it is performed just by cutting it off, without playing the attachment on the sclera. The back fixation seams allow for the reduction of the strength of the upper straight muscle while looking up, while the operation of the spinal cord trailer remains intact.
After the surgery, the eye under treatment is put on a sterile dressing that prevents the sensitive structure, which is the eye, from penetrating any contaminants and at least protects the patient from rubbing the eye a bit.

Time and course of convalescence

Immediately after the procedure, the eye under the dressing may excessively water or slightly suppurate, and the secretion may be tinted with blood. In the short period after surgery, this should not be a problem for the patient and it is enough to wash the eye gently with physiological saline.
Due to the stitched seams, the patient may feel a foreign body in the eye for some time after the surgery, but over time the feeling passes, as they are soluble sutures, which are absorbed after about 6 weeks after the procedure and there is no need to remove them. Swelling and redness, which usually worries the patient most, can last for several weeks.
If, after the healing control, 7-10 days after the treatment, nothing disturbing is revealed, the patient can usually return to work. However, it should be remembered that the operated eye should be protected against dirt and irritants (also referred to here as detergents - soaps, shampoos), it is best not to do eye makeup and wear glasses. Excessive physical effort, swimming pool or solarium is not recommended about two weeks after the procedure. Driving a car after surgery is an individual matter - if the patient feels confident enough to sit behind the wheel, there are no more contraindications. However, it should lead without the dressing on the operated eye so that three-dimensional binocular vision can be preserved.

Squint surgery– results

The result of the squint surgery is the restoration of the normal (straight ahead) rest position of the eyeballs, in most cases one treatment is sufficient. It may happen that there is a slight over-correction or under-correction of the defect - then reoperation is to be considered.
It is generally said that the effects of the squint surgery are better in children than in adults, mainly due to the greater plasticity of the children's nervous system and faster adaptation to new binocular vision conditions. This does not mean, however, that the operation of adults has no effect. In adults with fixed strabismus (eg, not operated in childhood) restoring the proper position of the eyeballs may cause the picture to be temporarily doubled until the nervous system adapts to the new visual axis.

Recommendations after the surgery

After the procedure, it is recommended to:
• using antibiotic eye drops for approximately 2 weeks
• healing control 7-10 days after the procedure
• rinsing of mucocutaneous mucus secretions with warm water or saline
• avoiding excessive rubbing of the eye
• avoiding excessive physical exertion
• care for the wound cleanliness - avoiding impurities and irritants, including cosmetics
• avoiding training at the pool about a month after the procedure
• report to the attending physician if any general symptoms occur (chills, fever, excessive sweating, etc.)

How long do the effects last after the treatment last?

Proper technical surgical treatment of squint made by a qualified team is permanent treatment.

How to avoid complications?

To avoid complications after squint surgery, you should inform your doctor before surgery about all diseases of co-existing and prescribed medicines, both those without prescription and prescription. You should inform about the history of hypersensitivity to medicines. Smokers should stop smoking at least a month before surgery, as nicotinic promotes prolonged wound healing and delays recovery from binocular vision. Follow the post-operative recommendations, do not skip the dose of antibiotic in eye drops, take care of proper hygiene of the wound, avoid excessive physical effort and irritants.

Possible complications

Complications after squint surgery are relatively rare, but they include:
• post-operative wound infection
• double vision
• unsatisfactory eye position
• complications related to anaesthesia
• loss of sight

Recommended additional treatment

Although this may seem insignificant, do not forget about the visual exercises, such as covering the eye of the instructor (healthy) to "mobilize" the eye squinting to set in the correct visual axis. As for more invasive interventions, botulinum toxin may be effective to temporarily adjust the eyeball position. The strabismus surgery is in itself an effective treatment and usually there is no need for additional procedures.

Author: Wiktoria Feret, MD
Literature:
Clinical ophthalmology, J. Kanski, Urban & Partner, Wrocław 1997; Basics of ophthalmology ed. 2, M.H. Niżankowska, Volumed, Wrocław 2000; Patient and Parent Guide to Strabismus Surgery, Childrens Eye Foundation, childrenseyefoundation.org

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