Overview
Definition:
Strabismus, commonly known as crossed eyes or squint, is a condition in which the eyes do not properly align with each other when looking at an object
One eye may turn inward (esotropia), outward (exotropia), upward (hypertropia), or downward (hypotropia)
It is a common childhood eye condition that can affect vision development.
Epidemiology:
The prevalence of strabismus in children varies, with estimates ranging from 2% to 5% of the pediatric population
It can occur at any age but is most often diagnosed in early childhood
Risk factors include family history, prematurity, certain genetic syndromes, and conditions affecting vision like cataracts or significant refractive errors.
Clinical Significance:
Untreated strabismus can lead to significant visual impairment, including amblyopia (lazy eye), reduced depth perception, and long-term cosmetic and psychosocial concerns
Early detection and appropriate management are crucial for optimal visual outcomes and preventing permanent vision loss, making it a key topic for pediatricians and residents preparing for DNB and NEET SS examinations.
Red Reflex Assessment
Technique:
The red reflex test is performed using an ophthalmoscope or a penlight at a distance of about 1-2 feet
Shine light towards the child's eyes from a moderate distance, observing the reflection in the pupils
Ideally, a symmetrical, bright reddish-orange reflex should be seen in both eyes.
Abnormalities:
An abnormal red reflex can manifest as a diminished reflex, an asymmetrical reflex (one eye brighter than the other), a whitish reflex (leukocoria), or the presence of shadows
White pupils (leukocoria) are particularly concerning and warrant urgent investigation for conditions like retinoblastoma or cataracts.
Interpretation:
A symmetrical and brisk red reflex suggests clear optical media
Asymmetry or absence of the reflex indicates an obstruction or misalignment
A consistently asymmetric reflex, where one eye's reflex is dimmer or absent, strongly suggests strabismus or amblyopia and requires further ophthalmological evaluation
This is a foundational screening tool for pediatricians.
Clinical Presentation
Symptoms:
Parents may report noticing one eye turning in or out
Blurred vision or difficulty focusing
Double vision (diplopia) may be reported by older children
Head tilting or covering one eye to see better
Poor depth perception
Reduced visual acuity in one eye.
Signs:
Visible misalignment of the eyes (manifest strabismus)
Inability to maintain eye alignment during fixation (intermittent strabismus)
Poor fixation or wandering eye movements
Corneal light reflex asymmetry (Krimsky test)
Cover test demonstrating phoria or tropia
Poor follow-up of moving objects.
Diagnostic Criteria:
Strabismus is diagnosed clinically based on observation of ocular alignment
The cover-uncover test is gold standard for differentiating between tropia (manifest deviation) and phoria (latent deviation)
Documentation of ocular misalignment at distance and near fixation is essential
Absence of a normal red reflex or significant asymmetry is highly suspicious.
Diagnostic Approach
History Taking:
Inquire about the onset and duration of eye misalignment
Ask about family history of strabismus, amblyopia, or refractive errors
Determine if the child experiences double vision or headaches
Enquire about any history of prematurity, birth trauma, or perinatal complications
Assess if vision screening has been done and any prior concerns raised by parents or caregivers.
Physical Examination:
Perform a complete eye examination including visual acuity assessment (Snellen chart, E-chart, or picture charts)
Assess the red reflex and pupillary reactions
Perform the cover-uncover test at distance and near to assess for phorias and tropias
Evaluate ocular motility in all gazes
Assess convergence
Check for nystagmus
Assess extraocular muscle function
Fundoscopy to rule out retinal abnormalities.
Investigations:
Refractive error assessment using retinoscopy or autorefraction
Cycloplegic refraction is often necessary in children to accurately determine refractive error and rule out accommodative esotropia
Visual evoked potentials (VEP) may be used in infants or non-cooperative children
MRI or CT scan of orbits and brain if neurological cause is suspected, especially with associated other neurological signs
Fundus photography for documentation and monitoring.
Differential Diagnosis:
Accommodative esotropia (due to uncorrected hyperopia)
Pseudostrabismus (due to epicanthal folds or wide nasal bridge)
Cranial nerve palsies (e.g., CN VI palsy)
Intermittent exotropia
Hypertelorism or hypotelorism
Neurological conditions affecting eye movements (e.g., brain tumors, hydrocephalus)
Congenital cataracts
Retinoblastoma.
Management And Referral Timing
Initial Management Pediatrician:
Perform a red reflex test on all newborns and infants during routine well-child visits
Educate parents on warning signs of strabismus
If any abnormality is noted in the red reflex or eye alignment, a prompt referral is indicated.
Referral Criteria:
Refer immediately to an ophthalmologist if: Leukocoria (white pupil) is observed
Significant asymmetry in the red reflex
Any visible eye turn (strabismus) is noticed
Child exhibits head tilting to see clearly
Poor visual fixation or eye pursuit
History of family eye disease like strabismus or amblyopia
Uncorrected refractive errors suspected during screening.
Ophthalmologist Management:
Management depends on the type and severity of strabismus
Options include optical correction (glasses), patching therapy (for amblyopia), vision therapy, and surgical correction of the eye muscles
Early intervention is key to prevent permanent vision loss.
Follow Up:
Regular follow-up with an ophthalmologist is crucial to monitor visual development, refractive error progression, and the stability of eye alignment
The frequency of follow-up depends on the child's age, the type of strabismus, and the treatment plan.
Complications
Early Complications:
Amblyopia (lazy eye) due to suppression of the deviated eye's image
Decreased visual acuity
Inability to achieve binocular single vision
Diplopia (double vision) if the brain fails to suppress the image from the deviated eye.
Late Complications:
Permanent visual impairment if amblyopia is not treated early
Poor depth perception affecting daily activities and future careers
Social and psychological issues related to cosmetic appearance
Recurrence of strabismus after surgery.
Prevention Strategies:
Routine vision screening in children by pediatricians, including the red reflex test and visual acuity assessment
Prompt referral of any suspicious findings to an ophthalmologist
Educating parents about warning signs and the importance of regular eye check-ups.
Key Points
Exam Focus:
The red reflex test is a critical screening tool for pediatricians
Leukocoria and asymmetric red reflexes are urgent red flags
Early referral for any suspected strabismus is paramount for preventing amblyopia and ensuring optimal visual outcome
Understanding the cover-uncover test and its interpretation is vital.
Clinical Pearls:
Always perform the red reflex test in a dimly lit room for better visualization
Compare the red reflex of both eyes simultaneously
Do not delay referral for any concerning finding, especially leukocoria
Even seemingly minor eye turns warrant a formal evaluation
Educate parents that strabismus is treatable if caught early.
Common Mistakes:
Overlooking or inadequately performing the red reflex test
Delaying referral despite abnormal findings
Mistaking pseudostrabismus for true strabismus without proper assessment
Failing to consider amblyopia development in a child with strabismus
Not performing cycloplegic refraction when indicated.