Is PPCD Bilateral or Unilateral?
Posterior polymorphous corneal dystrophy (PPCD) is classically a bilateral disease, but unilateral presentation occurs and is particularly common in pediatric cases. 1
Laterality Patterns
The 2024 AAO guidelines explicitly state that "corneal dystrophies are typically bilateral" 1, and PPCD follows this pattern in most cases. The disease is inherited in an autosomal dominant fashion and affects both eyes 2.
However, important exceptions exist:
- Pediatric presentations are frequently unilateral: In a 2022 pediatric series, 11 of 19 patients (58%) presented with unilateral PPCD 3
- Unilateral cases present with anisometropic astigmatism: The affected eye consistently shows greater astigmatism (≥1.5 diopters difference) and lower endothelial cell counts 4
- Risk of amblyopia in unilateral cases: Children with unilateral PPCD require aggressive amblyopia screening and treatment, as 7 of 27 affected eyes in one series had amblyopia at presentation 3
Clinical pitfall: Don't dismiss PPCD as a diagnosis simply because only one eye appears affected on examination. The contralateral eye may have subclinical disease or develop manifestations later.
Treatment Options for PPCD
Most patients with PPCD require only observation, as the disease is often asymptomatic; however, treatment becomes necessary when corneal edema, glaucoma, or amblyopia develop. 5
Treatment Algorithm by Disease Severity
Asymptomatic/Mild Disease (Most Common)
- Observation only with regular monitoring of:
- Intraocular pressure (IOP) - critical because glaucoma is a major complication 5
- Endothelial cell counts via specular microscopy
- Refractive error in children to detect anisometropia
Refractive Amblyopia (Pediatric Cases)
- Corrective spectacles as first-line treatment 4
- Occlusion therapy and/or atropine penalization for established amblyopia 4
- Early intervention is critical - visual prognosis depends on lesion position, age at diagnosis, and early spectacle correction 4
Glaucoma Management
- Medical management of elevated IOP is first-line
- Filtering surgery may be required for refractory cases 2
- Critical consideration: All patients with broad-based iridocorneal adhesions develop elevated IOP 2
Corneal Edema Requiring Surgery
Endothelial keratoplasty (EK) is now the preferred surgical approach over penetrating keratoplasty (PK) for PPCD with corneal edema. 1
Surgical Options in Order of Preference:
DMEK (Descemet's Membrane Endothelial Keratoplasty)
DSAEK (Descemet's Stripping Automated Endothelial Keratoplasty)
Penetrating Keratoplasty (PK) - reserved for cases unsuitable for EK
- Major concern specific to PPCD: High failure rate (41% in one series) 2
- Glaucoma caused 27% of all graft failures in PPCD patients 2
- Retrocorneal membrane formation occurred in 18% of grafts, exclusively in eyes with preoperative iridocorneal adhesions 2
- Disease recurrence: Abnormal host endothelial cells can overgrow the donor graft within 3.5 years 6
Key Surgical Considerations
The presence of slit lamp-visible iridocorneal adhesions is the most important prognostic factor for keratoplasty failure in PPCD. 2 These patients have:
- Higher risk of retrocorneal membrane formation
- Increased glaucoma risk
- Poorer overall graft survival
Common pitfall: The epithelial-like endothelial cells characteristic of PPCD can proliferate and migrate across the trabecular meshwork and onto donor grafts, causing both glaucoma and graft failure 2, 6. This unique pathophysiology makes PPCD more challenging to manage surgically than other endothelial dystrophies like Fuchs.