What is Tropia (Strabismus) of the Eye?
Tropia, also known as strabismus, is a misalignment of the eyes where the visual axes are not properly aligned, resulting in one or both eyes deviating from the normal position. 1
Core Definition
Strabismus represents a manifest ocular deviation that can be:
- Congenital or acquired throughout life 1
- Present in approximately 4% of the adult population, though it is more commonly associated with pediatric patients 1
- Characterized by the inability of both eyes to simultaneously fixate on the same target 1
Types of Strabismus
The condition manifests in several directional patterns:
Horizontal Deviations
Vertical Deviations
Torsional Components
- Cyclotropia: Rotational misalignment around the visual axis 1
Clinical Significance and Impact
The condition affects multiple domains of health and function:
Visual Consequences
- Binocular diplopia (double vision) in patients who develop strabismus after establishing normal binocular vision 1
- Suppression of the deviated eye's image in early-onset cases to avoid diplopia and visual confusion 4
- Amblyopia (lazy eye) development, particularly when strabismus begins in childhood 5, 6
- Loss of stereopsis and depth perception 1
Functional Impairments
- Compensatory head postures to maintain single vision or improve alignment 1
- Reduced field of binocular vision 1
- Difficulty with activities requiring depth perception such as driving, sports, and fine motor tasks 1
Psychosocial Effects
- Negative impact on self-image and social interactions due to abnormal appearance 1
- Employment discrimination and social stigma 1
- Reduced quality of life across multiple domains 1
Common Etiologies in Adults
The American Academy of Ophthalmology identifies numerous causes:
- Decompensated childhood strabismus that was previously controlled 1
- Sensory strabismus from unilateral vision loss 1
- Age-related conditions including divergence insufficiency and sagging eye syndrome 1
- High myopia with axial lengths exceeding 27mm, potentially leading to strabismus fixus 1
- Thyroid eye disease (Graves' disease) causing restrictive myopathy 1
- Neurologic disorders including cranial nerve palsies (3rd, 4th, 6th nerve) and myasthenia gravis 1
- Orbital trauma and iatrogenic causes from eye surgery 1
Treatment Goals
Management is symptom-directed and prioritizes:
- Elimination or reduction of diplopia 1
- Restoration or improvement of binocular vision when possible 1
- Reconstruction of ocular alignment for functional and cosmetic purposes 1
- Reduction of compensatory head positions 1
- Improvement in quality of life and psychosocial functioning 1
Treatment Modalities
Non-Surgical Options
- Optical correction with glasses for refractive errors, particularly in accommodative esotropia 1, 5
- Prism correction in spectacles for smaller deviations 1
- Occlusion therapy when other options fail 1
Surgical Intervention
- Extraocular muscle surgery remains the definitive treatment for most cases 1
- Success rates of approximately 80% after one procedure, exceeding 95% if a second procedure is performed 1
- Intractable postoperative diplopia in primary gaze occurs in 1% or fewer cases among patients without preoperative diplopia 1
Critical Clinical Pearls
Important considerations for diagnosis and management:
- Early intervention is crucial in children as binocular vision degrades rapidly, leading to suppression and amblyopia 1, 5
- Neurologic causes must be excluded, particularly in acute-onset adult strabismus 1
- Forced duction testing helps distinguish restrictive from paretic causes 1
- High-resolution orbital imaging is valuable for evaluating mechanical causes like sagging eye syndrome or thyroid eye disease 1
- The natural history varies by type: conditions like strabismus fixus are progressive and will not resolve spontaneously 1