Draft:Shortening of the eye muscle

The shortening of the eye muscle is a common type of surgery for treating the misalignment of the eyes. A misalignment in the eyes happens when one eye deviates inward (esotropia), outwards (exotropia). , upwards (hypertropia) or downwards (hypotropia), while the other eye remains focus. The above symptoms are collectively referred to as strabismus. Other types of less common strabismus include patterned strabismus, bilateral strabismus and cyclic strabismus. Among these several forms of strabismus, esotropia and exotropia could be treated by the shortening of the eye muscle, which is achieved by a resection or plication procedure.

Strabismus is one of the most common ocular diseases among the pediatric population and it falls under the category of both hereditary diseases and acquired diseases. Symptoms of strabismus include double vision, misalignment of eyes such as crossed eyes, ptosis and eye fatigue. Other than that, strabismus also imposes significant social challenges on the patient.

In a resection surgery, a small part of the eye muscle is cut and removed or folded over to strengthen the targeted weak eye muscle. In a plication surgery, the muscle is shortened by folding itself over and sutured without muscular incision. This is more effective in altering small prism changes and reducing surgery and recovery duration. However it can't be utilised for repositioning muscles in instances of pattern strabismus or small vertical deviations requiring a transposition of the horizontal rectus muscle.

Post surgery, patients frequently experience moderate soreness, bruising, and edema. Mucus discharge and coloured tears may be seen at first. Temporary double vision is possible, and it can take several months for the alignment of the eyes to settle. The desirable outcome of the surgery is to align the eyes/ eye movement and overall enhance visual comfort and function. However it may not be the most effective solution for strabismus caused by neurological coordination issues. Although the surgery is generally considered safe, potential risks such as infection, bleeding, scarring, residual or recurrent strabismus, overcorrection or undercorrection, temporary/ permanent double vision, and a small risk of decreased vision exists.

History
The earliest treatment included potions, purification, and dust, later followed with face masks with holes for the eyes to look through. The first surgical intervention to correct strabismus was eye muscle shortening surgery, which was credited to the english surgeon Chevalier John Taylor. However, the earliest recorded successful surgery is known to be performed by Johann Friedrich Dieffenbach. Dieffenbach performed eye muscle shortening surgery on a 7-year-old esotropic child, on 26th October 1839. Dieffenbach sectioned the medial rectus muscle (MR), the muscle functioning to keep the pupil close to the midline and moves the eye in lateral direction, by incising the conjunctiva, the thin mucous membrane covering the sclera. Sectioning the conjunctiva allows the access to the underlying tissues and cutting of the muscle to correct the eye misalignment.

Complete tenotomy often resulted in surgical complications and had limited success rates. Fortunately, partial tenotomy of the MR evolved, and many subsequent surgical variations were generated across the 19th and 20th century by Abadie, Stevens, Ziegler, Verhoeff, O’Connor, Blascovis, Bishop-Harmon, Astruc, Todd, Terrien, and others.

Hereditary Factors
Strabismus is one of the most common ocular disease among children, affecting approximately 2-4% of the population. Most forms of strabismus tend to run in families, meaning if your parent or siblings has strabismus, there are greater chances of you developing it. However the inheritance patterns for strabismus are not entirely clear, some forms of the disease are inherited in an autosomal dominant pattern, while there are also forms of the disease showing an autosomal recessive pattern.

Several genes are known to contribute to strabismus by coding transcription factors crucial to the ocular, cranial and motor neurons' development, being KIF2A, PHOX2A, and TUBB3 , respectively. Genetic diagnostic tests are now available for testing strabismus syndromes.

Environmental Factors
Strabismus can be developed throughout life as an acquired disease. Age-related changes in the eye, such as weakened or improperly functioning eye muscles, are often responsible for the emergence of strabismus in adults. Several environmental factors have been identified as potential causes, including vision problems like uncorrected refractive errors (nearsightedness, farsightedness, astigmatism), which can disrupt eye muscle balance. Neurological disorders such as a stroke, multiple sclerosis, or brain tumours can impact the nerves responsible for eye movement, potentially causing strabismus. Trauma or injury to the head or eyes, leading to damage of the muscles or nerves controlling eye movement, may result in strabismus as well.

Symptoms and Challenges
A primary symptom of strabismus is the misalignment of one or both eyes, where the eyes may appear to be crossed, turned, or not aligned in the same direction. Misaligned eyes can further cause eye strain, fatigue, and headaches when using the eye. Strabismus may also cause double vision, an individual seeing two images at the same time, causing confusion and discomfort as the brain is unable to process two different images simultaneously.

Strabismus can cause loss of depth perception, meaning the inability to accurately judge distances, impairing the individual’s ability to participate in sports or certain career.

It can present challenges for diseased individuals. Strabismus may cause impaired vision, limiting the individual’s ability to drive. Other than impaired vision, eye fatigue and discomfort, strabismus also leads to social challenges such as decreased quality of life for patients and their family members. Diseased individuals may feel self-conscious about their eye misalignment, leading to lower confidence, self-esteem, and social interactions.

Types and Processes of Surgery
Before the surgery, the patient’s medical history is reviewed, prior eye muscle surgeries and current medications are most important. An eye exam is performed before the surgery to clarify which muscles need to be modified, then general or local anaesthesia will be applied in preparation for the procedure. Before any general eye surgery, the surgical team will hold the patient’s eye open using an eye speculum and proceed to cut open conjunctiva to allow access to the target muscle.

Resection (Cut)
During a resection surgery, the muscle will be pulled up with a hook and have a small part of it cut, then removed or folded over and sutured, allowing the shortened muscle to reattach to the eye.

Resection is effective for large angle strabismus as it allows for a more significant muscle alteration to improve muscle function. Moreover, some studies suggest that resection provides a superior long-term stability compared to plication, such that patients receiving resection showed better survival and more stable outcome while patients receiving plication showed high rates of recurrence of exodeviation. Furthermore, resection appears to have greater versality as it can be applied to a broader range of strabismus and severities and is effective in treating both horizontal and vertical muscle correction or unilateral and bilateral strabismus, and it is an effective tool in treating under-corrected or recurrent strabismus.

Plication (Tightening)
Plication, a non-incisional surgical technique, entails the folding of a muscle over itself to accomplish shortening. It is frequently employed as a substitute for rectus muscle resection during rectus muscle surgery. The necessary amount of shortening or strengthening of the muscle is determined. Using specific suturing procedures, a section of the muscle is folded or tucked within itself without making an incision, resulting in muscle pleats or folds. The sutures are securely tied to maintain the intended effect. This effectively reduces its length or increases its tension, achieving the desired plication.

Plication has various benefits over resection. There is no risk of losing the muscle since it stays attached to the sclera throughout the treatment, allowing for future surgical modifications to better align the eye, if necessary. Plication retains anterior ciliary circulation and causes less tissue stress and haemorrhage than resection, possibly reducing the duration of recovery. The procedure is thought to be reasonably simple, with the potential to shorten operational time. Studies indicate that plication is especially suitable for small-angle deviations compared to recession/resection. Limitation is that this technique cannot be employed for the cases of pattern strabismus or small vertical deviations where a vertical transposition of the horizontal rectus muscle is desired.

Recovery
Following the shortening surgery, it is common for patients to experience minor discomfort, bruising, and swelling. Pink/crimson tears and mucus discharge are common throughout the first post-procedure days. As blood gets closer to the eye's surface, it can appear bright red. The duration of the redness varies, with some individuals showing relief within a few days and others taking weeks or even months. Double vision is another common occurrence after surgery, as the brain needs time to adjust to the new eye position. Throughout the recovery time, the alignment of the eyes will gradually change; it may take several months to reach the objective alignment. It is advised to keep irritants like shampoo away from the eyes for a few days and refrain from swimming for at least a week to avoid infections. Oral medications or eye drops are advised as long as they are approved by the optometrist in charge. Contact lenses should be avoided for one to two weeks, and attending follow-up appointments is crucial for proper post-operative care

Desired Outcome
The shortening of the eye muscle surgery aims to achieve multiple positive outcomes. One primary goal is to properly align the eyes, which can restore binocular vision. When the eyes are aligned, it becomes easier for the brain to combine visual input from both eyes, leading to improved depth perception and 3D vision. Additionally, successful surgery can improve the cosmetic appearance of the eyes by correcting misalignment. Furthermore, strabismus surgery aims to alleviate visual symptoms such as double vision, eye strain, and difficulty focusing, resulting in enhanced visual comfort and overall visual function. However, surgical correction may not be optimal if the underlying cause of strabismus is related to the neurological pathway and nervous system's ability to coordinate the eyes.

Potential risks and complications
The procedure is generally regarded as safe, however it has potential risks and complications. Bleeding during or after surgery is possible, though surgical techniques and meticulous hemostasis techniques help mitigate this risk. . Conjunctival scarring, although typically minimal, may occur at or around the surgical site. However, this effect is often purely of cosmetic importance. Although unlikely, the most common infections that can occur after strabismus surgery include conjunctivitis and surgical site infections, such as cellulitis or abscess formation. Overcorrection or undercorrection of eye alignment is also a potential complication, which may lead to an imbalance in eye position, resulting in residual or recurrent strabismus. Temporary or, in rare cases, permanent double vision can be experienced post-surgery. Additionally, there is a small risk of decreased vision, although this is more commonly associated with pre-existing ocular conditions rather than the surgical intervention itself