Squint Surgery:

Facilities at Eye Surgery

At our facility, there is excellent provision of space, time and equipment to allow our consultants to examine you and provide any necessary treatment. Many factors influence the ease with which squint assessments are achieved. These include experienced eye surgeons, who are uniquely skilled in diagnostic techniques, clinical interpretation and therapeutic modalities.

Squint surgery encompasses neuro-ophthalmology and adult eye muscle disorders, with an emphasis on binocular vision and eye movements. By choosing various test procedures, our ophthalmologists can formulate impressions including a differential diagnosis and possible modes of non-surgical treatment. All the options and outcomes are fully discussed with you.

Definition of Squint

A “squint” is the common name for ‘strabismus’ or ‘heterotropia’ which is the medical term used to describe eyes that are not pointing in the same direction, or which are misaligned. Squints are also sometimes called 'lazy eye', to refer to a turned eye, but this is not an accurate description. Squints can be classified according to the direction of the turn of the eye: esotropia (convergent) refers to an eye that turns inwards towards the nose; exotropia (divergent) refers to an eye that points outwards; hypertropia is when eye is upwards. Binocular vision occurs when both eyes are looking towards the same direction, to produce a single, combined image at the brain.

Classification

The classification of squint may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset (congenital –at birth, or acquired- later in life) and the relevance of any associated refractive error. The type of strabismus is established by a detailed history and examination.

The squint may be present all or only part of the time, in only one eye or alternating between the two eyes. A squint can occur for a number of reasons: these separately or together cause squint.

Refractive (focusing) abnormality
Eye muscle imbalance
It can run in families
Illness - can make it obvious
Fatigue, stress or extended work load
Injury
Rarely, it can be due to other diseases or illness.

Adult Concerns over Squints

A major concern of individuals with squints is the effect on their cosmetic appearance. Double vision (diplopia) is one of the most troublesome visual disorders a patient can experience. This is when a person sees two images of the same object some or all of the time. The two images may be vertically separated (one on top of the other) or horizontally separated (side by side) or both (oblique). The ability to read, walk and perform common activities is suddenly disrupted. The management goal is to establish clear binocular single vision.

Compared to binocular vision, adults with strabismus may have a decrease in their field of vision, absence of stereopsis or depth vision, decreased visual acuity and impaired spatial orientation. Individuals with squints are disadvantaged in visual motor skills, form and colour, and of appreciation of the dynamic relationship of the body to the environment, which facilitates control of manipulation, reaching and balance.

Squints may manifest as difficulties in eye hand coordination, clumsiness, bumping into objects and / or people, ascending or descending stairs or kerbs, crossing the street, driving, various sports and other activities of daily living which require stereopsis and peripheral vision.

Surgical Treatments

The definition of a satisfactory outcome in a given case is a matter for discussion between the patient and eye surgeons. The type and amount of surgery to perform for a particular squint is a decision for our experienced surgeons. This demands an accurate pre-operative decision and necessitates meticulous surgical planning and accurate prediction of surgical outcome.

The surgical aims are re-alignment of the eye muscles where necessary to achieve satisfactory function and cosmetic appearance. This can mean that the non-squinting eye may be operated on. Since some patients may recover function over time, surgery may not be considered initially. Patients need to be advised that, whilst accuracy in measuring and operating upon strabismus is essential, the response to surgery is variable and cannot be guaranteed. Our surgeons employ good practice and discuss the actions necessary if the desired surgical outcome is not achieved.

Non-Surgical Treatment Modalities

Prisms, refractive lenses, vision therapy, eye patching and pharmacologic measures have been used to help patients achieve fusion (alignment of the eyes) and alleviate diplopia, in addition to surgery. Some patients will adapt by suppressing the vision of one eye to eliminate their diplopia. An additional technique is the use of Botulinum toxin.

Botulinum Toxin (Botox)- Therapeutic Uses

Introduction: What is Botulinum Toxin (Botox)?

Botulinum toxin (Botox) is a complex protein produced by the anaerobic bacterium Clostridium botulinum. It produces a total of seven different toxins all of which have the same end result, the paralysis of muscle. One of the toxins, Botulinum Neurotoxin Type A, is now available for medical use under the trade name Botox. Advantage can be taken of the effects of Botox to alleviate muscle spasm or to weaken a muscle for therapeutic purposes. In therapeutic applications, minute quantities of botulinum neurotoxin type A are injected directly into selected muscles. Ocular conditions that respond include squints and spasm of the eyelid (blepharospasm).

Botox therapy is invasive. Its use should be reserved for patients in whom an ophthalmic diagnosis has been established with reasonable certainty. At the Ophthalmic Surgery Centre, Botox therapy is conducted by a skilled interdisciplinary team and sophisticated instrumentation and electromyography are available to ensure valid diagnosis, state-of-the-art treatment, and appropriate follow-up. Our ophthalmologists who administer this drug are highly trained in its use and qualified to manage any complications. Botox treatment of ophthalmic conditions requires proper identification of the affected eye muscles.

What are the Indications for the Use of Botox Treatment?

Botox is effective as an alternative to surgery to realign the eyes of selected patients with congenital or acquired strabismus. The toxin appears to be more effective in esotropia (in-turning of the eyes) of small to moderate angles than in exotropia (out-turning), vertical deviations, or large angle deviations.

Botox may prevent contracture of opposing eye muscles in cases of eye muscle palsy from which some recovery is expected. In these cases, single binocular vision may be enabled or enhanced during the recovery phase, and late contractures that would require surgery may be prevented.

Is Botox Safe?

Since 1990, success rates of over 90% have been reported in medical literature. Wide attention has been given to Botox and more and more applications have been found for it, often with equally impressive success rates. Botox is now the treatment choice for muscular spasms affecting the face, and repeated studies have demonstrated that it is a very safe and effective treatment.

How is Botox Used?

Injections into the target muscle are carried out by a very fine needle. The sites of the injection will vary slightly from patient to patient, and according to the ophthalmologist’s preference.

How Long Does it Take to Work?

Benefits begin in 1-14 days after the treatment and last on average three to four months, after which it can be repeated. All effects of the toxin ultimately reverse with time.

What Are Its Side Effects and Complications?

Many studies have confirmed side effects to be minor in the vast majority of applications. Side effects are generally transitory, well tolerated, and amenable to treatment. They are related to the dose of Botox administered. Persistent complications are distinctly rare, and serious side effects are uncommon. Some of the reported side effects include:

Flu like symptoms. These are mild and transient.

Systemic complications are uncommon

Pain at the site of injection, and headaches again mild and transient.

Muscle weakness. This is to be expected in the muscles injected but in practice this is rarely a problem.

Weakness in other areas is rarely troublesome and is associated with large doses.

Allergy is a theoretical risk but is virtually unknown.

Antibodies can be produced and if this happens the toxin becomes ineffective, but there are no other effects. The antibodies often disappear with time and treatment may be successfully recommenced after an interval.

Other very low incidence of complications of botulinum toxin injections includes droopy eye (ptosis), dry eye and photosensitivity. One of the more common adverse effects, ptosis, is due to diffusion of toxin from the upper eyelid injection sites to the levator muscle.
Although the side effects of the toxin are generally uncommon and not serious there are nonetheless contraindications to treatment with botulinum toxin. Please telephone the Ophthalmic Surgery Centre for further details.

Pregnancy and lactation.

Infection in the vicinity of the injection site.

Current therapy with a certain class of uncommonly used antibiotics, known as the amino glycosides.

Blood clotting disorders or current therapy with drugs inhibiting blood clotting, e.g. Warfarin.

Diseases affecting the muscles, particularly myaesthenia gravis.

Allergy to tetanus toxoid is a potential, but not absolute contraindication.

Eye Movements: The Extra-Ocular Muscles:

The extra ocular muscles work together to produce movements of the eyes in each of the eight cardinal directions of gaze. There are six extra ocular muscles that move the globe (eyeball) These muscles are named the superior rectus, inferior rectus, lateral rectus, medial rectus, superior oblique, and inferior oblique.

Squint refers to abnormal movements of the eyeballs through lack of co-ordination of the muscles that control their movement.

medial rectus (MR)—moves the eye toward the nose

lateral rectus (LR)—moves the eye away from the nose

superior rectus (SR)—primarily moves the eye upward and secondarily rotates the top of the eye toward the nose

inferior rectus (IR)—primarily moves the eye downward and secondarily rotates the top of the eye away from the nose

superior oblique (SO)—primarily rotates the top of the eye toward the nose and secondarily moves the eye downward

inferior oblique (IO)—primarily rotates the top of the eye away from the nose and secondarily moves the eye upward
Upgaze, or turning the eye upward, is primarily the work of the superior rectus muscle, with some contribution by the inferior oblique muscle.

Downgaze, or turning the eye downward, is primarily the work of the inferior rectus, with some contribution by the superior oblique.

Abduction, or turning the eye outward toward the ear, is primarily done by the lateral rectus. Adduction, or turning the eye inward toward the nose, is primarily done by the medial rectus. In addition, the levator palpebrae superioris muscle, which is not seen on the drawing, elevates the eyelid.