Choroidal folds (CF) are linear or groove-shaped morphological abnormalities that occur in the posterior pole of the fundus. They result from undulation of the choroid, Bruch’s membrane, and retinal pigment epithelium (RPE).
On ophthalmoscopy, the crests appear bright yellow and the troughs appear dark brown. On fluorescein angiography (FA), they appear as alternating hyperfluorescent and hypofluorescent linear patterns. They usually run horizontally or obliquely in parallel, and in hypotony, they radiate from the optic disc. It is rare for them to extend anteriorly beyond the equator.
The term “chorioretinal folds” is also used, sometimes referring to a condition where not only the choroid and RPE but also the full thickness of the retina undulates. The distinction between the two can be evaluated by OCT (see Clinical Findings).
The mnemonic T.H.I.N. R.P.E. is known for remembering the causes1).
Tumors, Hypotony, Hyperopia, Inflammation, contracting Neovascular membrane, Retrobulbar mass, Papilledema, Extraocular hardware.
Ocular/Choroidal Origin
Hypotony: Postoperative, traumatic, ciliary body hypofunction, etc. Characterized by a radial pattern around the optic disc.
Choroidal tumor/Choroidal neovascularization: Due to local elevation or contraction.
High hyperopia / microphthalmos: The posterior pole is relatively compressed due to axial shortening.
Orbital / systemic causes
Orbital tumor / thyroid eye disease: Compression force is applied to the posterior wall due to retrobulbar pressure.
Increased intracranial pressure (IIH / Chiari malformation): Optic nerve sheath dilation leads to posterior wall compression.
Posterior scleritis: Caused by inflammatory thickening and deformation of the sclera.
Postoperative / Idiopathic
After trabeculectomy: May occur due to low intraocular pressure or in combination with cataract surgery.
After scleral buckling: Directly caused by deformation of the sclera.
Idiopathic: Unknown cause. Some cases are bilateral and not accompanied by papilledema.
CF itself is not a lesion that directly leads to blindness, but it may be a sign of serious systemic or ocular diseases such as IIH, orbital tumor, or posterior scleritis. In particular, unilateral, acute-onset CF with papilledema requires investigation of the cause, and prompt systemic examination is necessary.
Symptoms of CF vary greatly depending on the location and severity of the lesion.
Major examination findings are shown below.
Fluorescein angiography (FA): A characteristic striped pattern with alternating hyperfluorescence (ridges = areas where RPE is thin) and hypofluorescence (valleys = areas where RPE is thick and overlapping) is observed. Importantly, there is no leakage in the late phase, and staining does not occur unless CNV is present. It has been reported that in VKH disease, FA also shows linear hypofluorescence at CRF sites 5).
OCT: This is the most important test for evaluating the characteristics of CF. It can distinguish between CF and CRF as follows.
When the appearance of folds is evaluated with SD-OCT, wrinkling findings, increased foveal thickness, and fluid clefts between the outer granular layer and the outer plexiform layer may be observed 2).
Organize the morphology of folds and examination findings.
| Finding | Characteristic |
|---|---|
| Choroidal folds | RPE/choroidal undulation, retinal surface is flat |
| Chorioretinal folds | Full-thickness retinal undulation |
MRI/B-scan ultrasound: In cases of SAHCF (acquired hyperopia and choroidal folds syndrome), MRI shows flattening of the posterior pole and a “V” sign of the optic nerve 4). It is also useful for excluding retrobulbar mass and posterior scleritis.
Optic disc findings: In cases of Chiari 1 malformation with basilar invagination, Fresnel Grade I papilledema has been reported 3), which is an important finding suggesting the presence of increased intracranial pressure.
Choroidal thickness: In one reported case, the parafoveal choroidal thickness (PCT) of the eye with SAHCF measured by EDI-OCT was 138 μm, significantly increased compared to 91 μm in the healthy eye4).
CF is a wrinkling of the underlying tissues (choroid, Bruch’s membrane, and RPE), while the retinal surface remains flat (in the case of choroidal folds). In contrast, an epiretinal membrane is a membranous tissue formed on the retinal surface, primarily causing inner layer wrinkling due to traction. OCT can clearly differentiate between the two.
The causes of CF are diverse. Clinically, the differential diagnosis differs depending on whether it is unilateral or bilateral.
Common causes for unilateral and bilateral cases are shown below.
| Common causes in unilateral cases | Common causes in bilateral cases |
|---|---|
| Orbital tumor, ocular hypotony | Thyroid eye disease, high hyperopia |
| Posterior scleritis, trauma | IIH, microphthalmos |
The characteristics by main cause are as follows.
SAHCF (Syndrome of Acquired Hyperopia and Choroidal Folds) is an acquired hyperopia and choroidal folds syndrome accompanied by flattening of the posterior pole of the eye and axial shortening. There may be underlying increased intracranial pressure, and lumbar puncture for cerebrospinal fluid pressure measurement is recommended even in the absence of papilledema 4). Posterior pole flattening and the optic nerve “V” sign on MRI are diagnostic clues.
Diagnosis of CF begins with assessment of fundus findings, and multifaceted examinations are necessary to search for the cause.
Fluorescein Angiography (FA)
Alternating hyperfluorescent and hypofluorescent stripes: Hills and valleys are depicted in a striped pattern. This is the basis for diagnosis.
No late leakage: If there is no CNV complication, staining and leakage are not observed. Also useful for severity classification.
Optical Coherence Tomography (OCT)
Imaging tests (MRI, B-scan)
Exclusion of retrobulbar mass and scleritis: Search for orbital and intracranial lesions using CT/MRI.
Posterior globe flattening and optic nerve “V” sign: Characteristic MRI findings of SAHCF4).
Other important examination findings are shown below.
There is no specific treatment for CF itself. Addressing the underlying cause is the basis of treatment.
Restoring intraocular pressure is the top priority. In cases of CRF after trabeculectomy, it has been reported that CRF resolved with inflammation suppression and intraocular pressure recovery using steroid eye drops 2).
Anti-VEGF therapy is selected. There is a report of a case in which bevacizumab was ineffective, but switching to aflibercept led to resolution of subretinal fluid and improvement of visual acuity to 20/20 (1.0) 1). Subsequently, it was maintained for 4 years with a treat-and-extend regimen every 6–8 weeks 1). However, CF often persists even after CNV treatment 1).
In a case of pattern dystrophy-associated bilateral CF reported by Xu and Faridi (2021), bevacizumab was ineffective for CNV in the right eye, but after switching to aflibercept, SRF resolved and corrected visual acuity reached 20/20 1). The left eye was maintained with observation only.
Oral acetazolamide and weight management are standard treatments 4). Correction of intracranial pressure can be expected to improve CF.
The indication for surgical decompression (e.g., posterior fossa decompression) should be evaluated in collaboration with neurosurgery 3). Since intermittent CRF depends on fluctuations in intracranial pressure, surgical intervention can be a definitive solution.
Some cases resolve after removal of the underlying cause. Improvement has been reported after correction of ocular hypotony or tumor resection. On the other hand, choroidal folds often persist in SAHCF or chronic cases. In cases with CNV, even if CNV is controlled with anti-VEGF therapy, CF may persist 1).
According to Friberg’s biomechanical model, compressive forces within the choroid cause buckling of Bruch’s membrane and the RPE, leading to the formation of choroidal folds 2, 3). External forces applied to the posterior wall of the eye (such as tumors, orbital compression, or scleral deformation) or traction on the posterior wall due to low intraocular pressure from within the eye generate this compressive force.
The pathogenesis of choroidal folds during intracranial hypertension is as follows4).
Furthermore, the translaminar pressure difference (TLPD) across the lamina cribrosa also plays an important role4). It is thought that CF appears before papilledema because the flexible optic nerve sheath causes flattening of the posterior pole earlier than axonal transport disruption4).
In highly myopic eyes with scleral thinning, the posterior sclera is prone to deformation even with slight external pressure or intraocular pressure fluctuations2). Even with normal intraocular pressure, deformation of the posterior sclera may fall below the threshold for CRF formation. This mechanism is thought to underlie the occurrence of CRF in a case of cataract surgery after trabeculectomy, even though the intraocular pressure was within the normal range at 9 mmHg2).
Three scenarios are hypothesized for the relationship between CNV and CF1).
In cases of Chiari 1 malformation with basilar invagination, transient increases in intracranial pressure due to Valsalva maneuvers are thought to cause intermittent episodes of CRF that appear and resolve repeatedly3). The mechanism by which CRF resolves when intracranial pressure normalizes is due to the release of pressure on the posterior pole.
Research using OCTA is increasingly showing that decreased perfusion of the choriocapillaris can be detected as a linear signal coinciding with CF sites. Whether this decreased perfusion is a cause or a consequence of CF formation remains unclear at present.
Comacchio et al. (2023) reported that in cases of SAHCF, the affected eye PCT was significantly increased at 138 μm compared to 91 μm in the healthy eye4). They suggest that PCT may serve as a disease marker for SAHCF, and that choroidal thickening may increase mechanical stress on Bruch’s membrane.
The following table summarizes values from a literature review of SAHCF cases.
| Item | Value | Notes |
|---|---|---|
| Mean age | 41 years | SD 12.42 |
| Male ratio | 83% | Out of 35 cases |
| Bilaterality | 37% | — |
In microgravity environments, cephalad fluid shift occurs, leading to increased intracranial pressure, choroidal folds, optic disc edema, and hyperopic shift, collectively known as SANS (Spaceflight-Associated Neuro-ocular Syndrome) in astronauts 4). The similarity between SAHCF and SANS has attracted attention, and CSF dynamics research (such as CSF trapping mechanisms due to a one-way valve effect) may contribute to elucidating the pathophysiology of both conditions 4).
In pattern dystrophy, which involves lipid deposition in Bruch’s membrane, weakening of Bruch’s membrane can independently or synergistically cause choroidal folds and choroidal neovascularization 1). Reports that choroidal folds persist even after controlling choroidal neovascularization with anti-VEGF therapy suggest that the pathophysiology of choroidal folds is independent of choroidal neovascularization.
In a comprehensive review of pachychoroid disease, Cheung et al. (2025) suggested that anastomosis formation between vortex veins (choroidal vascular remodeling) may contribute to reducing congestion 6). Whether this venous remodeling is involved in the onset and resolution of CF is a topic for future research.
As part of a condition known as SANS (Spaceflight-Associated Neuro-ocular Syndrome), CF has been reported to occur in microgravity environments 4). The cephalad fluid shift caused by microgravity increases intracranial pressure, leading to CF, papilledema, and hyperopic shift through a mechanism similar to SAHCF. This is also an important finding in visual function assessment after long-duration spaceflight.
