Haab’s Striae Notes

Haab’s Striae Notes

Definition & Clinical Significance

• Haab’s striae are horizontal, curvilinear, or concentric breaks in Descemet’s membrane (DM) caused by mechanical stretching of the infant cornea under high intraocular pressure.
• They are a hallmark sign of primary congenital glaucoma (PCG) and other forms of infantile-onset glaucoma(e.g., secondary congenital glaucoma, glaucoma associated with congenital anomalies or anterior segment dysgenesis).
• Their presence indicates significantly elevated intraocular pressure (IOP) during the first 3 years of life, when the sclera and cornea are still elastic, pliable, and prone to stretching.

Pathophysiology

• Elevated IOP in infants causes corneal enlargement (buphthalmos) due to the inherent elasticity of the young cornea.
• The Descemet’s membrane is a non-elastic basement membrane secreted by corneal endothelial cells.
• As the cornea stretches, DM ruptures along lines of stress, creating Haab’s striae.
• Why horizontal?
  • The cornea stretches more in the horizontal meridian due to the elliptical shape of the infantile cornea and the distribution of stress forces.
  • The endothelium migrates over the breaks and lays down new DM, creating a double-contoured appearance on histology.

Clinical Features

Feature	Description
Appearance	Horizontal or curvilinear, glass-like lines on the posterior cornea.
Location	Typically central or paracentral, sparing the periphery.
Number	Usually multiple, but a single striae may be seen in mild cases.
Associated Signs	– Buphthalmos (enlarged cornea, >12 mm diameter in newborns). – Corneal edema (due to endothelial dysfunction). – Photophobia, blepharospasm, epiphora (classic triad of congenital glaucoma).
Age of Onset	<3 years (cornea loses elasticity after this age).

Differential Diagnosis of Descemet’s Membrane Breaks & Enlarged Cornea

Condition	Key Distinguishing Features
Birth Trauma (Forceps Injury)	– Vertical or oblique DM breaks (due to compression of the globe against the orbital rim). – Unilateral (frequently left eye due to Left Occiput Anterior birth presentation). – Normal corneal diameter (no buphthalmos) and normal IOP.
Megalocornea	– Bilateral enlarged cornea ($>13\text{ mm}$) without IOP elevation or Haab’s striae. – X-linked recessive; clear cornea, normal cup-to-disc ratio, normal anterior segment.
Corneal Dystrophies (e.g., CHED)	– Congenital Hereditary Endothelial Dystrophy: Diffuse, bilateral corneal edema from birth. – No DM breaks, normal corneal diameter, normal IOP.
High Axial Myopia	– Increased axial length without corneal stretching or DM breaks. – Normal IOP and normal corneal diameter.

Diagnostic Workup

1. History & Examination
   • Assess for photophobia, tearing, blepharospasm.
   • Measure corneal diameter (normal newborn: 9.5–10.5 mm; >12 mm suggests buphthalmos).
   • Slit-lamp exam: Haab’s striae appear as refractile lines on the posterior cornea.
2. IOP Measurement
   • Use Tonopen or Perkins tonometer under anesthesia (avoid general anesthesia if possible in infants).
   • Normal IOP in infants: ~10–15 mmHg; >20 mmHg is suspicious.
3. Gonioscopy
   • Evaluate the anterior chamber angle for trabeculodysgenesis (e.g., flat iris insertion, Barkan’s membrane).
4. Axial Length & Pachymetry
   • Increased axial length and thin central cornea (due to stretching).
5. Imaging
   • UBM (ultrasound biomicroscopy) or AS-OCT to assess angle structures.

Management

1. Medical Therapy (Temporizing Bridge to Surgery)

Primary congenital glaucoma is essentially a surgical disease. Medical therapy is used only to temporarily lower IOP prior to surgery or as adjunctive therapy in refractory cases.

• Topical beta-blockers (e.g., timolol 0.25%) or carbonic anhydrase inhibitors (e.g., dorzolamide).
• Avoid: Prostaglandin analogs (ineffective in infants) and miotics (paradoxical IOP rise).

🛑 CRITICAL SAFETY CONTRAINDICATION:

See also: Notes on Diffraction of Light

Alpha-2 Agonists (e.g., Brimonidine, Apraclonidine) are STRICTLY CONTRAINDICATED in infants and young children

2. Surgical Therapy (Definitive Treatment)

Procedure	Indication & Approach
Goniotomy	– First-line option when the cornea is clear enough to visualize angle structures. – Ab-interno incision of the trabecular meshwork under direct gonioscopic visualization.
Trabeculotomy (Incisional or 360° GATT)	– First-line option when corneal opacity/edema obscures the anterior chamber angle. – Ab-externo cut into Schlemm’s canal to cleave the trabecular meshwork into the anterior chamber.
Combined Trabeculotomy + Trabeculectomy (CTT)	– Preferred in severe presentations, advanced buphthalmos, or developing regions where single interventions carry lower success rates.
Glaucoma Drainage Devices / Cyclophotocoagulation	– Reserved for refractory cases after failed primary angle surgeries (e.g., Ahmed or Baerveldt implants).

Postoperative Care & Long-Term Rehabilitation

• Regular Monitoring: Lifelong follow-up of IOP, corneal diameter, axial length, optic nerve cupping, and visual acuity.
• Refractive Error Correction: Haab’s striae and axial elongation cause high astigmatism and axial myopia. Prompt optical correction (glasses/contact lenses) is required.
• Amblyopia Management: Occlusion therapy (patching) for anisometropic or deprivation amblyopia.

Prognosis & Complication

Prognosis

• Early diagnosis & surgery: 80–90% success in IOP control.
• Poor prognostic factors:
  • Late presentation (>1 year).
  • Severe corneal edema or buphthalmos.
  • Associated ocular anomalies (e.g., aniridia, Sturge-Weber syndrome).
• Visual outcomes depend on:
  • Duration of elevated IOP before treatment.
  • Optic nerve damage at presentation.
  • Amblyopia (due to corneal opacities or anisometropia)

Long-Term Complications

Complications

1. Corneal
   • Persistent edema (if endothelial damage is severe).
   • Band keratopathy (chronic edema).
2. Optic Nerve
   • Glaucomatous cupping (irreversible if untreated).
3. Refractive
   • High myopia (due to axial elongation).
   • Anisometropia (if unilateral).
4. Amblyopia
   • Deprivation amblyopia (corneal opacity) or anisometropic amblyopia.

Key High-Yield Exam Points

• ✅ Haab’s Striae = Breaks in Descemet’s Membrane due to horizontal stretching in infantile glaucoma.
• ✅ Horizontal/Concentric Orientation (vs. Vertical/Oblique in forceps birth trauma).
• ✅ Classic Symptom Triad of PCG: Epiphora, Photophobia, Blepharospasm.
• ✅ Surgical Choice: Goniotomy (Clear cornea) vs. Trabeculotomy (Cloudy cornea).
• ✅ Black Box Contraindication: Brimonidine is contraindicated in infants (causes CNS depression and apnea).
• ✅ Primary Cause of Permanent vision Loss: Amblyopia (anisometropic or deprivation).

High-Yield Mnemonics

• “Haab’s = Horizontal” (vs. Vertical in Forceps Birth Trauma).
• “3 P’s of PCG Symptoms”: Photophobia, Palpebral spasm (blepharospasm), Profuse tearing (epiphora).
• “3 H’s of Physical Examination”: Haab’s striae, Hazy cornea, Huge eye (buphthalmos).

Primary References

1. American Academy of Ophthalmology (AAO): Basic and Clinical Science Course (BCSC), Section 6: Pediatric Ophthalmology and Strabismus.
2. American Academy of Ophthalmology (AAO): Basic and Clinical Science Course (BCSC), Section 10: Glaucoma.
3. Beck, A. D., et al. Childhood Glaucoma. Childhood Glaucoma Research Network (CGRN) Classification.
4. Becker-Shaffer’s Diagnosis and Therapy of the Glaucomas (8th Edition).