Parapapillary Chorioretinal Atrophy
Overview
Parapapillary atrophy (PPA)1 is more frequently observed in patients with glaucoma than in those with ocular hypertension and normal individuals.2,3 The incidence of PPA has been found to be significantly higher in eyes with glaucomatous structural and/or functional progression compared to eyes without glaucomatous structural and/or functional progression.2,3 PPA progression is associated with progressive structural and functional glaucomatous damage.2,3
The alpha and beta zones of PPA are larger in eyes with glaucoma than in eyes without glaucoma.4,5,6 The frequency of beta-zone PPA is strongly correlated with the stage of the disease as well as the associated structural glaucomatous damage such as neuroretinal rim loss, decreased retinal vessel diameter, decreased retinal nerve fiber layer (RNFL) visibility, and correlating visual field defects.4,5,6
The presence of beta-zone PPA can be very helpful in the diagnosis of early glaucoma and can be a predictive factor for glaucomatous progression in those already diagnosed with glaucoma.7,8
PPA is important in the morphologic diagnosis of glaucomatous optic neuropathy.
Pearls
Appearance:
In normal eyes, both alpha and beta zones are largest and most frequently located in the temporal horizontal sector followed by the inferior temporal and superior temporal sectors. This PPA is smallest and least frequently observed in the nasal parapapillary area.
Alpha zone:
Peripheral zone of irregular hypopigmentation/hyperpigmentation with chorioretinal thinning.
Outer border is adjacent to the retina.
Inner border is adjacent either to the peripapillary scleral ring or to the beta zone (visible sclera and visible large choroidal vessels).
Equivalent to pigmentary irregularities in the retinal pigment epithelium.
Found in almost ALL normal eyes (15% to 20%), therefore more common than beta zone.
Relative scotoma.
Beta zone:
If present, beta-zone PPA is adjacent to the peripapillary scleral ring.
The beta zone borders the optic nerve.
Characterized by smooth margins with the adjacent alpha zone on its outer border and with the peripapillary scleral ring on its inner border.
If both zones are present, the beta zone is always closer to the optic disc than the alpha zone.
Significant RPE atrophy with easily visible sclera and large choroidal vessels.
Associated with significant thinning of the chorioretinal tissue and reduced choroidal volume.
May suggest reduced vascular perfusion in patients with primary open-angle glaucoma (POAG).9
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