Optometry & Visual Performance 286 Volume 13 | Issue 4 | December 2025 "cross-wiring" between the horizontal and vertical gaze centers in the brainstem (e.g., involving the posterior commissure or oculomotor nuclei). This leads to inappropriate upward movement when binocular fusion is disrupted. • Fixation Loss: In congenital esotropia, poor early visual development may contribute to latent nystagmus or unstable fixation, exacerbating the deviation. • It is not typically linked to cranial nerve palsies. • DVD is benign in terms of vision-threatening effects but can contribute to sensory adaptations like anomalous retinal correspondence. A side note on Inferior Oblique Overaction in Infantile Strabismus Inferior oblique overaction (IOOA) is a condition where the inferior oblique muscle is hyperactive, leading to abnormal eye elevation. In the context of infantile strabismus (typically infantile esotropia, but sometimes exotropia), bilateral IOOA is a common associated finding that contributes to vertical or torsional eye misalignment. IOOA typically becomes evident by 1-3 years of age, often as infantile esotropia (diagnosed before age 6 months) progresses. The inferior oblique muscle elevates the eye when it is adducted, contributes to excyclotorsion, and works in concert with other extraocular muscles to maintain binocular alignment. In IOOA, this muscle contracts excessively or inappropriately, causing characteristic bilateral (may be asymmetric) eye movements of excessive elevation on adduction, where the eyes are more convergent (esotropic) in downgaze. The obliques are weak abductors. Therefore, when inferior oblique muscles overact in IOOA and/or superior oblique muscles underact in SOP, it causes a relative divergence in upgaze compared to downgaze, resulting in a V-pattern esotropia. IOOA is often seen alongside dissociated vertical deviation (DVD), though the two are distinct: IOOA is more prominent in adduction, while DVD occurs independently of gaze direction and is triggered by occlusion / fixation. The exact cause of IOOA in infantile strabismus is not fully understood but may involve: • Neuromuscular imbalance: Abnormal innervation to the inferior oblique muscle, possibly due to developmental issues in the oculomotor system. • Compensatory mechanism: In infantile esotropia, the brain may over-activate the inferior oblique to compensate for horizontal misalignment, leading to secondary vertical deviation. • Congenital factors: IOOA is more common in congenital strabismus and may be linked to abnormal muscle anatomy or neural control. Inferior Oblique Overaction (IOO) vs. Superior Oblique Palsy (SOP) It is important to understand that when you have a palsy of one muscle (SOP), you are going to have an overaction of its antagonist (IO is antagonist to SO), so an SOP is going to look very similar to an IOO, it’s just that the inferior oblique overaction is secondary to the superior oblique palsy vs. a primary IOO due to a congenital esotropia.
RkJQdWJsaXNoZXIy MjEyMDQ0Nw==