Primary Angle Closure and Nanophthalmos
Pathophysiology of Primary Pupillary Block Angle Closure
Definition and Core Mechanism: Primary pupillary block angle closure is a form of glaucoma characterized by the iris moving forward to physically cover the trabecular meshwork (TM).
A relative seal forms between the posterior aspect of the iris and the lens.
This seal traps aqueous humor behind the iris in the posterior chamber.
The resulting pressure gradient drives the iris forward (iris bombé), obstructing the TM and preventing aqueous outflow.
Clinical Outcomes of Mechanism:
Acute Angle Closure: An abrupt and severe elevation of intraocular pressure
Intermittent Problems: Transient spikes in pressure.
Chronic Pressure Elevation: Ongoing high pressure that may be indistinguishable from primary open-angle glaucoma (POAG) without gonioscopy.
Emerging Research and Alternatives:
Current research, notably by Harry Quigley and colleagues, suggests the mechanism may involve more than just pupillary block.
The theory involves changes in iris volume and choroidal thickness.
In normal eyes, the iris loses volume during dilation; however, eyes prone to angle closure often do not exhibit this loss of volume.
The Kitchen Sink Analogy:
Open Angle Glaucoma: The drain (TM) looks normal to the naked eye, but there is resistance deep within the "piping."
Angle Closure Glaucoma: The iris acts like a physical stopper placed in the sink, visibly blocking the drain.
Epidemiology and Demographic Risk Factors
Race and Ethnicity:
Asian Populations: High prevalence. Most notably, of bilateral blindness in China is attributed to angle closure glaucoma.
Asian Heritage Findings: Individuals of Asian descent have been noted to respond less effectively to laser iridotomy compared to Caucasians, though the cause is currently unknown.
Inuits and Eskimo Groups: These populations have a very high prevalence of angle closure and are ethnically closely related to Asian populations.
African Heritage: Acute angle closure is uncommon in this demographic; however, chronic angle closure is more frequent.
Anatomic and Physiological Factors:
Refractive Error: Typically occurs in hyperopic individuals (farsighted) who possess smaller, more "crowded" eyes.
Anatomy: Characterized by a shallow anterior chamber.
Age: Prevalence increases with age because the lens naturally thickens and the pupil becomes smaller (miotic). Both factors exacerbate the pupillary block mechanism.
Biological Sex: Women are at a substantially higher risk than men.
Genetics: A positive family history of angle closure is a significant risk factor.
Triggers for Angle Closure Attacks
Mydriasis (Pupillary Dilation): Anything that causes the pupil to dilate can precipitate an attack. This happens most commonly not during full dilation, but as the iris is slowly coming down from a dilated state to a mid-dilated position.
Environmental: Dim illumination (e.g., dark movie theaters).
Psychological: Emotional stress.
Pharmacological: Mydriatic drops (cold medicines, sleep aids).
Clinical Warnings: Warning labels on cold/sleep medications regarding glaucoma refers specifically to these narrow angles. POAG patients are generally not at risk from these medications.
Strong Cholinergic Agents: High-percentage pilocarpine or agents like echothiophate can actually worsen the condition by moving the lens-iris diaphragm forward and inducing angle closure.
Clinical Classifications and Presentations
Acute Angle Closure:
Symptoms: Severe eye pain, headache, blurred vision, colored halos around lights, nausea, and vomiting.
Differential Misdiagnosis: Because of the systemic distress (nausea/vomiting), these patients are sometimes mistakenly treated for gastrointestinal (GI) issues.
Clinical Case Example: A -year-old white male presented with a 4-day history of intermittent headaches and blurry vision, progressing to constant severe pain and nausea. His pupil was mid-dilated, the cornea was "steamy" (edematous), and the eye was injected.
Diagnostic Questions:
What is the refractive error? (Pupillary block is unlikely in a myope, such as a individual).
What does the other eye's angle look like? (If the fellow eye is wide open, pupillary block is less likely).
Intermittent (Subacute) Angle Closure:
Presentation: Subtle symptoms including transient pain, headaches, and halos that resolve spontaneously.
Case Study: A woman radiologist (frequently working in the dark) suffered from "intractable headaches" for years. She underwent extensive neuro-workups (2 MRIs, CT, lumbar puncture) before gonioscopy revealed critically narrow angles. A laser iridotomy permanently resolved the headaches for over years of follow-up.
Chronic Angle Closure:
Presentation: Often asymptomatic, progressing much like POAG.
Progression: Gradual loss of peripheral and night vision, with central vision loss occurring very late.
Key Findings: Elevated , optic nerve cupping, and visual field loss. Diagnosis is confirmed by narrow angles and frequent peripheral anterior synechiae (PAS) on gonioscopy.
Ocular Examination Findings
Acute Attack Findings:
Injected eye (ciliary flush).
Cloudy/steamy cornea (due to edema).
Fixed, mid-dilated pupil.
Very high : Frequently to or higher.
Iris bombé.
Sequelae of High Pressure:
Iris Atrophy: Can appear as radial or even "spiraling" fibers (resembling twisted bicycle spokes).
Glaucomflecken: Small, sub-epithelial grey-white opacities in the anterior lens capsule caused by aqueous stasis and focal lens necrosis; these can marginate over time.
Pigment Deposition: On the iris and the corneal endothelium.
Optic Disc: Initial hyperemia followed by pallor and cupping after the attack is resolved.
Spontaneous Resolution: Attacks may break on their own, resulting in transient hypotony (low pressure) and cell/flare in the anterior chamber, which complicates diagnosis.
Management and Treatment
Initial Medical Management (Acute Attack):
Aggressive use of pressure-lowering drops.
Pilocarpine: Used only once the has dropped sufficiently for the iris sphincter to respond to the drug; otherwise, ischemia prevents the drug from working.
Systemic Agents: Carbonic anhydrase inhibitors (e.g., Acetazolamide) and hyperosmotic agents (e.g., Mannitol).
Mechanical and Surgical Interventions:
Corneal Indentation: Using a gonio lens (like a Posner-Sussman lens) to push the iris away from the TM and manually break the pupillary block.
Laser Iridotomy (LPI): Creating a hole in the iris to allow aqueous flow. This allows the iris to settle back into a more normal position. Recommended locations are temporal or superior.
Iridoplasty: Used if the cornea is too cloudy to perform a laser iridotomy; involves pulling the iris out of the angle.
Surgical Iridectomy: Rarely performed; reserved for patients who cannot cooperate with a laser (e.g., mentally challenged).
Goniosynechialysis: Using a spatula or forceps to physically pull the iris away from the TM to break fresh synechiae (usually less than a year old), often done during cataract surgery.
Trabeculectomy: Performed if the angle is damaged beyond repair. Caution is required due to the risk of aqueous misdirection (malignant glaucoma); long-term postoperative Atropine is used to prevent this.
Prophylactic Treatment:
The Fellow Eye: The untreated fellow eye of a patient who had an acute attack has a high risk of developing an attack. The anxiety of the first attack can even trigger the second eye due to sympathetic stimulation. A prophylactic iridotomy is mandatory.
Indications for Prophylactic LPI: Elevated with appositional closure (> 180^{\circ}), presence of PAS, or segmental pigmentation in the superior angle.
Nanophthalmos
Definition: A small eye that is usually structurally normal but has specific pathological features.
Anatomy:
Axial length is typically very short (often less than ).
The lens is abnormally large relative to the eye size.
The sclera is very thick and impermeable.
Clinical Risks:
Early-onset angle closure glaucoma.
Choroidal Effusion: Exceptionally high risk during any intraocular surgery because fluid cannot escape through the thick sclera.
Management Strategies:
Avoid intraocular surgery if at all possible.
Use laser iridotomy or iridoplasty first.
If surgery is necessary, "scleral windows" (partial-thickness sclerectomies) are performed in the inferior sclera to allow drainage of prospective suprachoroidal fluid.
Differential Diagnosis
Plateau Iris: Often includes an element of pupillary block.
Phacomorphic Glaucoma: Secondary to a large, cataractous lens.
Aqueous Misdirection (Malignant Glaucoma): The central chamber is often shallower than in simple pupillary block.
Others: Ciliary body swelling and intraocular tumors.
Key Takeaways
Primary pupillary block is a leading cause of blindness, especially in Asia.
Standard treatment is Laser Iridotomy ().
Post-iridotomy angles rarely become "normally deep"; serial gonioscopy is required.
Clinicians should not merely tell patients to avoid dark rooms/cold meds; if a patient is at that level of risk, an iridotomy should be performed immediately.