Miscellaneous Secondary Glaucomas Notes

Iridoschisis: Characteristics and Pathophysiology

• Definition and Epidemiology

  • Iridoschisis is an extremely rare ocular disease primarily affecting elderly individuals.
  • It typically manifests in the inferior portion of the iris.
  • The etiology is believed to be related to actinic damage (cumulative sun exposure) affecting the iris tissue.

• Mechanisms of Secondary Glaucoma

  • Secondary Open-Angle Glaucoma: The anterior iris stroma splits from the deeper layers of the iris. This fragmented iris tissue and associated pigment cells can migrate and impair the trabecular outflow system, leading to elevated intraocular pressure.
  • Secondary Angle-Closure Glaucoma: In some cases, the anterior lamella of the iris splits but does not fragment. Instead, it bows forward, physically covering or overlaying the trabecular meshwork to cause angle closure. The speaker noted this mechanism is theoretically possible but observed less frequently than the fragmented open-angle variety.

• Clinical Presentation

  • On gonioscopy, iris fragments may be seen floating in the anterior chamber or touching the corneal endothelium.
  • Physical appearance: The iris may look "scrambled," with visible splitting between the anterior and posterior layers.
  • The condition develops into glaucoma in approximately $50\%$ of affected patients.

• Surgical Management

  • If iris fragments are in direct contact with the cornea, it can lead to corneal decompensation.
  • Surgical intervention involves trimming the fragmented iris tissue back to clear it from the corneal surface and address the glaucoma.

Posterior Polymorphous Corneal Dystrophy (PPMD)

• Overview and Genetics

  • PPMD is a rare, bilateral condition that can lead to angle-closure glaucoma.
  • It is often familial and can be inherited in an autosomal dominant pattern, though sporadic cases occur.
  • Glaucoma develops in roughly $14\%$ of patients with PPMD.

• Pathophysiology

  • The corneal endothelium develops epithelial-like characteristics.
  • This abnormal endothelium grows as a membrane across the iridocorneal angle, similar to the pathology seen in Iridocorneal Endothelial (ICE) syndrome.
  • Unlike ICE syndrome, PPMD is typically bilateral and lacks the distinct iris structural changes (like polycoria or corectopia) characteristic of ICE.
  • The membrane contraction results in synechial angle closure.

• Clinical Examination Findings

  • Presence of endothelial vesicles or "blisters" on the posterior corneal surface.
  • These vesicles may form linear patterns or clusters.
  • Associated findings include corneal edema and eventual corneal decompensation, which is often the primary symptomatic complaint of the patient.
  • Extensive peripheral anterior synechiae (PAS) can be observed during gonioscopy.

• Treatment Approach

  • Management is similar to ICE syndrome, focused on treating chronic angle-closure glaucoma.
  • Medical management involves aqueous suppressants.
  • Patients frequently require corneal transplants to address decompensation.

Ciliary Body Swelling and Drug-Induced Glaucoma

• Post-Surgical Causes

  • Ciliary body swelling can occur following retinal surgeries, specifically scleral buckling procedures and pan-retinal photocoagulation (PRP).

• Systemic Medication Triggers

  • When angle closure is bilateral, systemic medications must be investigated.
  • Topiramate (Topamax): This is the classic systemic cause of drug-induced ciliary body swelling. It is primarily used for the treatment of depression and seizures.
  • Other triggers include sulfa-based drugs.

• Clinical Signs of Topiramate-Induced Glaucoma

  • Induced Myopia: Patients often experience a sudden shift toward nearsightedness because the lens moves forward.
  • Timing: Symptoms typically manifest within the first month of starting the medication.
  • Mechanics: The condition is NOT caused by pupillary block; therefore, laser peripheral iridotomy (LPI) is not indicated.

• Management Strategies

  • Discontinuation: The primary treatment is stopping the offending medication (in consultation with the prescribing physician).
  • Medical Therapy: Treatment includes cycloplegics (to rotate the ciliary body back) and topical steroids.
  • Choroidal Effusions: If present, these may need to be surgically drained.
  • Contraindications: Cholinergics such as pilocarpine should be avoided.
  • Procedures: Peripheral iridoplasty may be utilized if necessary.

Anti-VEGF Injections and Elevated Intraocular Pressure

• Background

  • Anti-Vascular Endothelial Growth Factor (anti-VEGF) injections are widely used to treat various retinal vascular diseases.
  • While highly effective for their primary purpose, their long-term impact on intraocular pressure (IOP) is a growing area of study.

• Statistics and Correlations

  • A prospective study found that after a mean of $6.7$ injections, nearly $5\%$ of patients developed elevated IOP.
  • There is a statistically significant correlation between the peak intraocular pressure and the total number of injections received.
  • Patients with pre-existing glaucoma are at a higher risk for this secondary pressure elevation.

Miscellaneous Secondary Conditions

• Fuchs Endothelial Corneal Dystrophy

  • This condition leads to progressive thickening of the cornea.
  • In patients who already have narrow angles, the increased thickness of the cornea can further crowd the anterior chamber and precipitate angle-closure glaucoma.

• Schwartz-Matsuo Syndrome (Schwartz Syndrome)

  • This is an uncommon condition associated with rhegmatogenous retinal detachment.
  • Pathophysiology: A retinal break allows the outer segments of photoreceptors to be released into the subretinal space and eventually into the anterior chamber. These photoreceptor segments mechanically plug the trabecular meshwork.
  • Clinical Appearance: On slit-lamp exam, the photoreceptor segments can resemble "cell" (inflammatory cells), but aqueous taps confirm they are actually photoreceptor segments.
  • Treatment: Aqueous suppressants are used for temporary pressure control, but the definitive treatment is surgical repair of the underlying retinal detachment.

• Posterior Masses

  • Glaucoma can be secondary to posterior segment issues that displace the lens-iris diaphragm forward.
  • Examples include:
  • Suprachoroidal hemorrhage.
  • Intraocular tumors.
  • Ciliary body cysts.