Exotropia

Exotropia Essentials - Outward Eye Turn

• Definition: Outward deviation (divergence) of one or both eyes.
• Types & Features:
  • Intermittent Exotropia (IXT): Most common type. Eye turn occurs sometimes, especially when tired, ill, or viewing distant objects. Good fusional control initially.
    • Often closes one eye in bright sunlight (photo-occlusion).
    • Diplopia rare, suppression common.
  • Constant Exotropia: Eye turn present at all times. May be congenital or develop from IXT.
  • Sensory Exotropia: Due to poor vision in one eye (e.g., cataract, optic atrophy). Eye with poor vision deviates outwards.
  • Consecutive Exotropia: Develops after surgical overcorrection of esotropia.
• Basic Mechanisms: Imbalance between fusional convergence and divergence mechanisms. Innervational factors (e.g., high AC/A ratio in divergence excess) or anatomical factors.

⭐ Intermittent exotropia is the most common type of childhood exotropia, often manifesting between 1-4 years of age. Control is typically worse for distance fixation than near initially in many cases (Divergence Excess type).

Exotropia Evaluation - Spotting the Drift

• History: Onset, duration, frequency (constant/intermittent), triggers (distance, fatigue, inattention), family Hx.
• Visual Acuity (VA): Best corrected; rule out/quantify amblyopia.
• Cover Tests: Key for detection.
  • Cover-Uncover Test: Detects manifest XT (eye drifts OUT, refixates IN on uncover).
  • Alternate Cover Test (ACT): Dissociates; reveals total deviation (phoria/intermittent tropia).
  • Prism ACT (PACT): Measures deviation in PD (distance & near).
• Ocular Motility: Ductions, versions; check A/V patterns, oblique dysfunction.
• Near Point of Convergence (NPC): Receded (>10-15 cm) suggests Convergence Insufficiency.
• Cycloplegic Refraction: Essential for accurate refraction.
• Sensory Evaluation:
  • Worth 4 Dot: Fusion, suppression, diplopia.
  • Stereoacuity: (e.g., Titmus, TNO) quantifies depth perception.

⭐ Control of intermittent exotropia is often assessed using the Newcastle Control Score (NCS), grading home and clinic control.

Intermittent Exotropia - The On-Off Squint

• Most common exotropia; intermittent outward eye turn, often with fatigue, illness, or distance viewing.
• Clinical Features:
  • Onset: Typically 1-4 years.
  • Symptoms: Asthenopia, photophobia; children rarely report diplopia.
  • Signs: Intermittent deviation, initially good fusional control.

  ⭐ Closing one eye in bright sunlight is a characteristic sign.

• Types:
  • Basic: Distance deviation ≈ Near deviation.
  • Convergence Insufficiency Type: Near deviation > Distance deviation.
  • Divergence Excess Type: Distance deviation > Near deviation.
• Management:
  • Goal: Improve control, alignment, and binocular vision.
  • Options:
    • Observation: Small, well-controlled deviations.
    • Non-surgical: Minus lenses (if high AC/A), occlusion, orthoptic exercises (convergence).
    • Surgical: For poor control, ↑ deviation, or significant symptoms (e.g., bilateral lateral rectus recession).

Exotropia Treatment - Aligning the Gaze

• Goal: Ocular alignment, binocular vision (stereopsis), symptom relief.

• Non-Surgical:

  • Observation: Small, well-controlled intermittent XT.
  • Optical Correction: Full cycloplegic refraction for significant errors.
  • Occlusion Therapy: Part-time, for amblyopia or to improve XT control.
  • Orthoptic Exercises: (📌 Pencil Push-ups) For convergence insufficiency (CI) type or small intermittent XT.

• Surgical:

  • Indications: Constant XT, large angle (>20 PD), poor control, progression, asthenopia.
  • Timing: Usually 4-7 years; earlier for constant XT.
  • Procedures: Based on XT type & angle. Bilateral Lateral Rectus (BLR) recession (common); Unilateral Recess-Resect (R&R).

⭐ Surgical success for intermittent exotropia is often defined as alignment within 10 PD of orthophoria and improved fusional control.

High‑Yield Points - ⚡ Biggest Takeaways

• Intermittent exotropia is the most common type, often presenting between 6 months and 4 years.
• Deviation worsens with fatigue, illness, or inattention; improves with visual focus.
• Monocular eye closure in bright sunlight is a characteristic sign.
• Amblyopia is less common than in esotropia but requires monitoring.
• Management includes observation, glasses (e.g., minus lenses for high AC/A), patching, orthoptics, and surgery.
• Surgical aim is often a slight initial overcorrection for better long-term alignment.
• Sensory exotropia results from poor vision in one eye.