What is Strabismus
Strabismus is a misalignment of the eyes where the visual axes fail to align properly with each other, which can be either congenital or acquired. 1
Core Definition and Epidemiology
Strabismus represents a failure of the two eyes to simultaneously focus on the same image, resulting in loss of binocular vision. 2 This ocular disorder affects approximately 4% of the adult population and 2-4% of the general population overall. 1, 2
Key Clinical Characteristics
The misalignment can manifest in multiple directions:
- Esotropia (inward deviation) - the most common type, accounting for approximately 63% of pediatric cases 3
- Exotropia (outward deviation) - representing about 34% of cases 3
- Hypertropia (upward deviation) 3
- Hypotropia (downward deviation) 1
The deviation may be comitant (same in all gaze positions) or incomitant (varying with gaze direction). 4
Etiology and Origins
Strabismus is not a single disease entity but rather a consequence of underlying problems affecting visual perception and oculomotor control. 5 The causes span from peripheral structures to central nervous system pathways:
Peripheral Origins
- Extraocular muscle dysfunction or injury 5
- Nerve palsies (3rd, 4th, or 6th cranial nerves) 1
- Genetic syndromes 2
- Orbital trauma 1
Central Origins
In most cases of comitant, non-restrictive, non-paralytic strabismus, the extraocular muscles and their innervations function properly, suggesting deficits in central neural pathways involved in visual perception and oculomotor control as the primary etiology. 5
Common Adult Presentations
Notable causes of adult strabismus include: 1
- Recurrent or decompensated childhood strabismus
- Sensory strabismus (from vision loss)
- Convergence insufficiency (15.7% of new-onset adult cases) 1
- Divergence insufficiency (10.6% of new-onset cases) 1
- Sagging eye syndrome (age-related, common in 60-80 year olds) 1
- Graves' disease
- Myasthenia gravis
- Iatrogenic causes from ophthalmic surgery 1
Clinical Consequences
The primary functional impacts include:
- Diplopia (double vision) - particularly problematic in adults with acquired strabismus 1
- Amblyopia - impaired vision from disuse, affecting the misaligned eye, particularly when strabismus develops in childhood 6
- Loss of binocular vision and stereopsis 2
- Psychosocial impacts affecting quality of life, self-esteem, employment opportunities, and social interactions 1
Treatment Goals
Modern treatment philosophy extends beyond simple motor alignment to encompass: 1
- Restoration of binocular vision when possible
- Control of diplopia
- Reconstruction of normal-appearing alignment
- Improved eye contact and self-image
- Gains in psychosocial and functional domains of vision-related quality of life
Surgical success rates are approximately 80% after one procedure and may exceed 95% with a second intervention if needed. 1 Intractable postoperative diplopia in primary gaze occurs in 1% or fewer cases. 1