Causes of Choroidal Effusion
Choroidal effusion results from fluid accumulation in the suprachoroidal space, most commonly caused by postoperative hypotony following glaucoma surgery, but also arising from inflammatory conditions, structural scleral abnormalities, certain medications, and various ocular pathologies. 1, 2
Primary Mechanisms of Formation
Choroidal effusion develops through three distinct pathophysiologic mechanisms 3:
- Intact membrane filtration: Increased serum filtration through an intact choriocapillary membrane with molecular sieving of proteins (67% of plasma protein concentration in suprachoroidal fluid) 3
- Membrane disruption: Hemorrhagic suprachoroidal fluid appearing acutely or subacutely through a disrupted isoporous membrane 3
- Elevated episcleral venous pressure: Intraoperative choroidal effusion with minimal protein content (18% of plasma concentration) in patients with elevated episcleral venous pressure 3
Surgical Causes
Postoperative Complications
The most common etiology is glaucoma surgery, particularly trabeculectomy and glaucoma drainage device implantation 1, 2:
- Hypotony-related: Postoperative hypotony combined with inflammation is the primary mechanism 4
- Cataract surgery: Can occur after cataract extraction alone or combined cataract-glaucoma procedures 3
- Retinal detachment surgery: Including scleral buckle placement 5
- Panretinal photocoagulation: Can cause ciliary body edema leading to forward lens-iris displacement 5
Non-Surgical Causes
Inflammatory Conditions
Multiple inflammatory diseases cause choroidal effusion through uveal inflammation 4:
- Posterior scleritis: Presents with deep pain, hyperemia, choroidal folds, and fluid in sub-Tenon space (T-sign on ultrasonography) 5
- Sympathetic ophthalmia: Associated with bilateral inflammation 4
- Pars planitis: Intermediate uveitis causing uveal effusion 4
- Vogt-Koyanagi-Harada disease: Bilateral uveitis with serous detachment 4
Structural/Idiopathic Conditions
Uveal effusion syndrome (UES) represents a primary abnormality requiring special consideration 6:
- Scleral pathology: Amorphous glycosaminoglycan-like material fills interfibrillary spaces with collagen fiber disruption 6
- Impaired transscleral drainage: Reduced macromolecular diffusion interferes with normal albumin egress, causing fluid retention 6
- Vortex vein abnormalities: Hypoplasia or partial absence of vortex venous system in idiopathic cases 4
- Demographics: Most typically affects middle-aged men with relapsing-remitting course 6
- Associated conditions: Hypermetropia and nanophthalmos 4, 6
Medication-Induced
Recent evidence identifies specific drug classes causing choroidal effusion 1:
- Monoclonal antibody medications 1
- Antiseizure medications (including topiramate and sulfonamides) 5
- Bisphosphonate medications 1
Vascular/Retinal Conditions
Retinal pathology can cause forward lens-iris displacement leading to secondary effusion 5:
- Central retinal vein occlusion: Causes ciliary body edema 5
- Intraocular gas or silicone oil: Forward displacement of lens-iris diaphragm 5
- Persistent fetal vasculature 5
- Retinopathy of prematurity 5
Neoplastic Causes
Tumors cause effusion through mass effect or direct invasion 5:
- Intraocular tumors: Direct angle invasion or mass effect 5
- Choroidal melanoma: Can present with associated choroidal detachment 5
- Choroidal metastases: Yellow-white elevated lesions with high internal reflectivity 5
Patient-Specific Risk Factors
Certain patient characteristics increase effusion risk 1:
Clinical Pitfalls
Critical distinction: Chronic serous choroidal detachment differs from acute postoperative effusions—chronic cases often indicate uveal effusion syndrome requiring full-thickness sclerectomies rather than conservative management 4, 6. The presence of bilateral disease strongly suggests UES or systemic inflammatory conditions rather than surgical complications 2.
Medication history is essential: Always inquire about recent initiation of monoclonal antibodies, antiseizure medications, or bisphosphonates, as these represent increasingly recognized iatrogenic causes 1.