Inferior Rectus Muscle Injury is More Common
The inferior rectus muscle is the most commonly damaged extraocular muscle during inferior blepharoplasty, not the inferior oblique. 1
Evidence from Guidelines
The American Academy of Ophthalmology explicitly identifies the inferior rectus as the most frequently injured extraocular muscle during lower eyelid blepharoplasty, with overall strabismus incidence remaining under 3%. 1 This occurs through multiple mechanisms including:
- Direct surgical trauma from excessive cautery, hemorrhage, and misdirected dissection 1
- Scarring and fat adherence in periorbital tissues that restrict muscle movement 1
- Local hemorrhage causing transient dysfunction even without permanent damage 1
The inferior rectus demonstrates anatomical vulnerability across multiple periocular procedures—it represents 70% of muscle injuries following retrobulbar or peribulbar anesthesia, further confirming its susceptibility in this anatomical region. 1
Contradictory Research Evidence
While the guideline evidence clearly favors inferior rectus injury, some older research studies present conflicting data:
- One 1998 case series found equal injury rates between inferior rectus and inferior oblique (4 of 6 cases each) following transconjunctival blepharoplasty 2
- A 2012 anatomical study emphasized inferior oblique vulnerability due to its position between medial and central fat compartments, particularly during transconjunctival approaches 3
- A 2002 study noted the inferior oblique lies "in the direct path of dissection" during transconjunctival fat pad exposure 3
However, these individual case series and anatomical studies are superseded by the 2026 guideline synthesis from the American Academy of Ophthalmology, which represents the most recent and authoritative evidence. 1
Clinical Presentation and Management
Patients with inferior rectus injury typically present with:
- Vertical diplopia that is incomitant, making prism correction rarely satisfactory long-term 1
- Transient symptoms in many cases, with improvement occurring after 8-15 months if injury results from local trauma or hemorrhage without significant scarring 1
Critical Timing Considerations
- If diplopia persists beyond 6 months without improvement, spontaneous resolution becomes unlikely and referral to a strabismus specialist is warranted 1
- Surgical intervention should be considered at this 6-month threshold rather than continuing observation 1
Common Pitfalls to Avoid
The inferior oblique's anatomical position makes it vulnerable during transconjunctival approaches specifically, as it originates 5.14 mm posterior to the inferior orbital rim and courses obliquely toward the lateral canthus. 3 However, this anatomical proximity does not translate to higher overall injury rates compared to the inferior rectus across all blepharoplasty techniques. 1
Surgeons should maintain meticulous dissection technique under direct visualization and use careful cautery to minimize risk to both muscles, though the inferior rectus remains the primary concern. 1, 4