Horizontal strabismus, commonly known as inward or outward deviation of the eyes, is a frequent eye condition that may require surgical correction. Although the first surgery is often successful, some patients develop residual or recurrent eye misalignment and require a second operation (reoperation).

This study aims to identify the clinical and surgical factors that may increase the risk of undercorrection, overcorrection, or recurrence after the first surgery. It also evaluates the outcomes and success rate of repeat surgery in patients with horizontal strabismus.

Patients undergoing reoperation will receive a complete ophthalmological examination before surgery. The surgical plan will be individualized based on previous surgical history and current eye findings. All procedures will be performed under general anesthesia by the same surgeon. Participants will be followed for three months after surgery to assess eye alignment, movement, and possible complications.

The results of this study may help improve surgical planning and predict which patients are at higher risk of requiring additional surgery in the future.

Horizontal strabismus, including esotropia and exotropia, represents the most common form of ocular misalignment requiring surgical intervention. Despite advances in surgical techniques, a proportion of patients experience residual deviation, overcorrection, or recurrence after primary surgery, necessitating reoperation. Reoperation presents unique surgical challenges due to altered anatomy, scar tissue formation, possible muscle slippage, and variability in postoperative healing response.

Reported reoperation rates vary across studies and clinical settings, with multiple patient-related and surgical factors implicated in surgical failure. These factors may include age at primary surgery, magnitude of deviation, amblyopia, number of operated muscles, surgical technique, and time interval between surgeries. However, data regarding predictive risk factors and standardized outcome evaluation in reoperated horizontal strabismus remain limited in the local setting.

This prospective interventional study will be conducted at Assiut University Hospital. It will include patients undergoing repeat surgery for correction of horizontal strabismus. Patients with vertical deviations, paralytic or restrictive strabismus, neurological or syndromic associations, or incomplete previous surgical data will be excluded.

Preoperative assessment will include measurement of visual acuity, cycloplegic refraction, anterior and posterior segment examination, evaluation of ocular motility in nine diagnostic positions of gaze, and measurement of angle of deviation using prism and alternate cover test or Krimsky test when appropriate. Documentation of conjunctival scarring and previous surgical details will be performed.

The surgical approach will be individualized according to preoperative findings and prior operative records. Exploration of previously operated muscles will be performed when clinically indicated. Intraoperative forced duction testing will assess muscle tightness. All surgeries will be conducted under general anesthesia by the same surgeon to reduce inter-operator variability.

Participants will be followed postoperatively at 1 day, 1 week, 1 month, and 3 months. Surgical success will be defined as postoperative alignment within ±10 prism diopters of orthotropia at final follow-up. Secondary outcomes include stability of alignment and postoperative complications such as limitation of ocular motility or conjunctival scarring.

Statistical analysis will evaluate associations between demographic and clinical variables and surgical outcomes using multivariate regression to identify independent risk factors for reoperation outcomes.

The findings of this study aim to improve risk stratification, optimize surgical planning, and enhance long-term outcomes in patients undergoing horizontal strabismus reoperation.

Inclusion Criteria:

• Patients diagnosed with horizontal strabismus (esotropia or exotropia).

  • Patients undergoing repeat surgery for correction of residual, recurrent, undercorrected, or overcorrected horizontal strabismus.
  • Availability of sufficient medical records documenting previous strabismus surgery.
  • Ability to attend scheduled postoperative follow-up visits.
  • Written informed consent obtained from the patient or legal guardian.

Exclusion Criteria:

• Combined vertical and horizontal strabismus.

  • Paralytic strabismus.
  • Restrictive strabismus.
  • Strabismus associated with neurological or syndromic conditions.
  • Patients with incomplete or insufficient documentation of previous surgical procedures.
  • Patients unwilling or unable to complete follow-up.