Strabismus Surgery Basics for Residents

Last updated: October 2026

Strabismus surgery changes where the eye muscles pull. The principles are simple, but good results depend on careful measurement, sensible planning and respect for the complications. This page covers what every resident should understand before scrubbing in.

Before surgery: measure well

• Measure the deviation with the prism cover test at distance and near, wearing full optical correction.
• Look for consistency: measurements should be stable on at least two visits.
• Measure in different gaze positions to detect A or V patterns and incomitance, and assess the obliques.
• Treat amblyopia first, and correct any significant refractive error. Accommodative esotropia is treated with glasses, not surgery.
• In adults, check for diplopia risk; a prism trial can show what the patient will experience after surgery.

Know the anatomy: spiral of Tillaux

The rectus insertions lie at increasing distances from the limbus:

The sclera is thinnest just behind the rectus insertions, which is where most sutures are placed. Take care.

Basic principles

• Recession (moving the insertion back) weakens a muscle.
• Resection or plication (shortening the muscle) strengthens it.
• Use the surgical dose tables of your unit as a starting point, then adjust for the individual patient. Never memorise a single number as "the" dose.
• Esotropia: commonly bilateral medial rectus recession, or a recess-resect procedure on one eye.
• Exotropia: commonly bilateral lateral rectus recession, or a recess-resect procedure on one eye.
• V pattern with inferior oblique overaction: inferior oblique weakening.
• Adjustable sutures help in adults, restrictive strabismus (such as thyroid eye disease) and reoperations.
• Botulinum toxin is an alternative in selected cases, such as small deviations, acute sixth nerve palsy, or patients unfit for surgery.

Special situations

• Thyroid eye disease: operate only when the disease has been inactive for several months, and after any orbital decompression. Recession of tight muscles (usually inferior and medial rectus) is the rule; resection of a restricted muscle makes things worse. Inferior rectus recession can cause lower lid retraction and late overcorrection. See thyroid eye disease.
• Vertical rectus surgery changes the lid position, because the lids are attached to the vertical muscles. Warn the patient.
• Paralytic strabismus: wait for spontaneous recovery (often around 6 months) before surgery, unless there is a reason to act sooner. See cranial nerve palsies.

Complications to know

• Oculocardiac reflex: traction on an eye muscle (especially the medial rectus) can cause sudden bradycardia. Release traction immediately; the anaesthetist may give atropine.
• Slipped or lost muscle: a sudden large deviation with limited movement after surgery. A lost medial rectus is the most feared. Needs urgent re-exploration.
• Scleral perforation during suturing: check the retina at the end of surgery; treat with laser or cryotherapy if needed.
• Anterior segment ischaemia: a risk when three or more rectus muscles are operated on in the same eye at once, especially in older patients. Plan staged surgery.
• Over- or under-correction, and new diplopia. Set expectations before surgery.
• Rare: infection, endophthalmitis, and adherence syndrome from fat prolapse.

After surgery

• Topical antibiotic and steroid for a short course.
• Review early for slipped muscle or infection, then again for alignment.
• In children, continue amblyopia treatment and refractive correction; surgery does not replace them.

Related: strabismus notes, anti-elevation syndrome, Newcastle control score, and squint treatment at Sadbhaav.