Hypotony maculopathy is a condition in which persistent low intraocular pressure (IOP) due to various causes leads to the formation of chorioretinal folds at the posterior pole of the fundus, resulting in visual dysfunction. It is often accompanied by optic disc edema, dilation and tortuosity of retinal veins, and dilation of choroidal veins, with common subjective symptoms including decreased visual acuity and metamorphopsia.
This disease was first reported by Dellaporta in 1954 as fundus changes associated with low IOP, and in 1972 Gass proposed the term “hypotony maculopathy” to clarify the pathogenesis of visual loss related to choroidal folds 8). Although low IOP itself is relatively common after surgery or trauma, only a subset of cases develop maculopathy leading to visual dysfunction. Individual factors such as scleral rigidity and axial length influence the onset.
Hypotony maculopathy can develop at IOP levels of 8–10 mmHg or lower, with the incidence increasing at 5 mmHg or below. Statistically, an IOP of less than 6.5 mmHg (more than 3 standard deviations below the mean IOP) is defined as “hypotony.” Clinically, it refers to a state where IOP is low enough to cause visual dysfunction.
Gass’s hypothesis, which states that mechanical strain on the retinal pigment epithelium (RPE) and photoreceptors due to chorioretinal folds is the main cause of visual dysfunction, is widely accepted. When the ocular wall collapses inward due to low IOP, redundancy in the choroid and retina leads to the formation of folds. If this change resolves within a short period, visual function may recover, but if it persists for a long time, irreversible visual dysfunction may result.
Statistically, hypotony is defined as an IOP less than 6.5 mmHg, which is 3 standard deviations below the mean IOP. However, hypotony maculopathy can develop at IOP levels of 8–10 mmHg or lower, and the incidence clearly increases at 5 mmHg or below. At 4 mmHg or below, severe visual loss (corrected visual acuity of 0.2 or worse) often occurs. Clinically, the level of hypotony that impairs visual function is the concern.
The most common cause is excessive filtration after glaucoma filtration surgery, particularly after trabeculectomy with mitomycin C (MMC). According to the glaucoma practice guidelines, the frequency of hypotony maculopathy as a complication that can cause visual dysfunction one month or more after surgery is reported to be 0.9–5% 1). In a review by Costa & Arcieri (2007), the incidence is summarized as ranging from 1.3% to 18% 8). The next most common cause is cyclodialysis associated with blunt trauma.
It is known to occur more frequently in young individuals and those with high myopia 2). In young and myopic eyes, the scleral rigidity is low, so the sclera tends to collapse inward under low intraocular pressure, and choroidal folds are easily formed. Elderly patients are more prone to choroidal effusion, while young patients tend to develop hypotony maculopathy. Since the use of antimetabolites became widespread, reports of hypotony maculopathy after filtration surgery have increased.
The causes of hypotony maculopathy are broadly divided into increased aqueous outflow and decreased aqueous production.
Fannin et al. (2003) identified the following risk factors for hypotony maculopathy 7).
In young patients, the scleral flap heals with weaker scarring, and excessive filtration tends to persist postoperatively. In myopic individuals, especially those with high myopia, the sclera is thin and fragile, so even with the same low IOP, chorioretinal folds are more likely to form. When these factors combine, the risk increases further.
The development of hypotony maculopathy involves a close interplay between abnormal aqueous humor dynamics and mechanical deformation of the ocular wall.
Abnormalities in aqueous humor dynamics leading to hypotony can be broadly divided into two categories.
In cyclodialysis after trauma, an open communication pathway is created in the ciliary body, allowing aqueous humor to flow into the suprachoroidal space, while damage to the ciliary epithelium reduces aqueous production. In filtering surgery using antimetabolites (MMC, 5-FU), scarring around the scleral flap is suppressed, increasing aqueous leakage1).
When ocular hypotony occurs, the scleral wall collapses inward, creating redundancy in the choroid and retina, leading to characteristic chorioretinal folds. The anteroposterior diameter of the eye shortens, resulting in hyperopic shift as a refractive error.
Sakamoto et al. (2018) reported that excessive scleral contraction, rather than choroidal thickening, is a major contributing factor in the development of hypotony maculopathy after trabeculectomy2). Persistent hypotony leads to relaxation and contraction of scleral collagen fibers, causing irreversible shortening of the axial length.
In the hypothesis proposed by Gass in 1972, chorioretinal folds cause mechanical strain on the RPE and photoreceptors, which is considered the essence of visual dysfunction. This hypothesis remains widely accepted.
Recent OCT studies have identified photoreceptor folds distinct from choroidal folds9). Photoreceptor folds form directly beneath choroidal folds and are accompanied by disruption of the photoreceptor outer segments. This mechanical damage to photoreceptors is the main cause of irreversible central vision loss; even if choroidal folds resolve, if photoreceptor damage persists, visual recovery is poor9).
With ocular hypotony, the lamina cribrosa bulges forward, restricting axonal flow and causing optic disc edema in the acute phase. In advanced glaucoma with few surviving axons, disc swelling may be inconspicuous even with hypotony.
When the posterior segment of the eye buckles due to low intraocular pressure, retinal venous outflow is obstructed, leading to stasis. This is clinically observed as dilation and tortuosity of retinal veins.
The duration of hypotony does not necessarily correlate with final visual acuity, but early recovery of intraocular pressure can lead to improvement in visual function.
The fundus findings of hypotony maculopathy share common features regardless of the cause, but associated findings differ by etiology.
Chorioretinal Folds
Folds in the posterior pole: Arranged radially or concentrically. This is the most characteristic finding of hypotony maculopathy.
Association with visual impairment: The direction, density, and distance from the fovea of the folds affect visual prognosis.
Vascular Tortuosity
Tortuosity of retinal arteries: Due to collapse of the ocular wall, retinal vessels become redundant and tortuous.
Dilation and tortuosity of retinal veins: Reflects venous stasis and becomes prominent.
Optic disc changes
Papilledema: Appears in the acute phase. It involves axonal transport impairment due to anterior bulging of the lamina cribrosa.
Tortuosity of optic disc vessels: In the chronic phase, peripapillary vascular tortuosity may persist.
Anterior segment findings
Shallow anterior chamber: This finding indicates aqueous humor leakage or cyclodialysis.
Hyperopic shift: Axial shortening leads to hyperopia. It may be accompanied by choroidal detachment.
Post-filtering surgery type
Chorioretinal folds: Radial to concentric folds form in the posterior pole.
Optic disc edema: Accompanied by redness and swelling of the disc.
Retinal venous dilation and tortuosity: Reflects venous stasis.
Shallow anterior chamber: Due to forward displacement of the iris, lens, and vitreous.
Choroidal detachment: Frequently associated with overfiltration.
Traumatic type (cyclodialysis)
Macular folds: Chorioretinal folds in the posterior pole.
Optic disc edema and hyperemia: Swelling around the optic disc is observed.
Retinal vascular tortuosity and dilation: Tortuosity of retinal veins and arteries.
Shallow anterior chamber: Associated with forward movement of the lens-iris diaphragm.
Angle recession: Angle abnormalities corresponding to the area of cyclodialysis may be observed.
Recent OCT studies have identified not only choroidal folds but also photoreceptor folds, and mechanical damage to the photoreceptor layer is considered the main cause of irreversible central vision loss 9). Hyperreflectivity of the Henle fiber layer has also been reported as a characteristic OCT finding 9).
When hypotony persists, the sclera contracts excessively, shortening the axial length. Sakamoto et al. (2018) reported that excessive scleral contraction contributes more to the development of hypotony maculopathy after trabeculectomy than choroidal thickening 2). Ultrasound B-scan may show thickening of the posterior sclera and choroid, and many cases are accompanied by choroidal detachment.
Maheshwari et al. (2022) reported a case of a 70-year-old man with primary open-angle glaucoma 3). After combined cataract and glaucoma surgery, severe hypotony (1 mmHg) and 360-degree choroidal detachment occurred, leading to hypotony maculopathy. Transconjunctival scleral flap suturing resolved the choroidal detachment, and both intraocular pressure and visual acuity improved.
The diagnosis of hypotony maculopathy is relatively straightforward based on history, confirmation of low intraocular pressure by tonometry, and characteristic fundus findings.
The characteristics of each examination method are shown below.
| Examination method | Main evaluation target | Characteristics |
|---|---|---|
| OCT | Chorioretinal folds / photoreceptor folds | Simple and first choice. Can detect fine folds. |
| FA | Linear hypofluorescence at folds, optic disc leakage | Also useful for evaluating retinal circulation delay. |
| ICG | Choroidal vein dilation, hypofluorescence at folds | Complementary when FA is unclear. |
| UBM / Anterior segment OCT | Location and extent of cyclodialysis | Essential for investigating cause of traumatic type. |
| B-scan ultrasound | Choroidal thickening, choroidal detachment | Can be used even in cases with opaque media. |
OCT is the first-line test and has higher detection ability than fundus examination. It is important to carefully check all radial scans. Even when the fundus appears clinically normal, OCT can detect pathological changes 9).
Fluorescein angiography (FA) characteristically shows linear hypofluorescence corresponding to RPE thinning at the folds and enhanced choroidal fluorescence at the fold peaks. Indocyanine green angiography (ICG) is useful as a complementary test in cases difficult to diagnose with FA, showing dilated and tortuous choroidal veins and multiple linear hypofluorescences.
In hypotony maculopathy after trauma, ultrasound biomicroscopy (UBM) and anterior segment OCT are essential for evaluating the extent of ciliary body detachment. Ciliary body detachment can also be observed by gonioscopy.
OCT can detect chorioretinal folds with high precision and can identify subtle folds that may be missed on fundus examination. Furthermore, it can evaluate findings related to visual prognosis, such as photoreceptor folds and hyperreflectivity of the Henle fiber layer 9). It is also useful for follow-up after treatment, allowing objective assessment of fold improvement and residual photoreceptor damage.
Diagnosis is made by the combination of hypotony and characteristic fundus findings. Inquire about history of glaucoma surgery, trauma, vitreous surgery, and anti-VEGF injections.
The mnemonic “THIN RPE” is known for the differential diagnosis of diseases causing chorioretinal folds.
Proceed with differential diagnosis considering the presence of hypotony, history of glaucoma surgery, and trauma history.
As the THIN RPE mnemonic indicates, chorioretinal folds can occur in many diseases such as tumors, inflammation, papilledema, and orbital space-occupying lesions. It is necessary to proceed with differential diagnosis considering the presence of hypotony, history of glaucoma surgery, and trauma history.
Treatment of hypotony maculopathy prioritizes identifying and addressing the cause. Since many cases resolve spontaneously, conservative treatment is first attempted, and if no improvement occurs, active intervention is considered stepwise.
Important time constraint: It has been reported that hypotony maculopathy persisting for more than 3 months tends to leave permanent visual impairment. Surgical treatment is recommended before visual dysfunction becomes permanent, and a decision is generally made within 1 to 6 months. Marked hypotony of 4 mmHg or less persisting for 2 to 3 months tends to leave metamorphopsia and relative central scotoma. On the other hand, if intraocular pressure is higher than 4 mmHg, visual function may recover even if it persists for about half a year.
Different approaches are taken depending on the cause.
If conservative treatment does not improve, consider the following interventions.
Surgical options if the above do not improve or if intraocular pressure recovery is not achieved are as follows.
The stages and timing of treatment are summarized as follows.
| Timing | Management |
|---|---|
| Early (up to 1 month) | Conservative treatment (pressure patch, SCL, atropine, steroids) |
| No improvement | Autologous blood injection, viscoelastic injection, transconjunctival scleral flap suture |
| 1–3 months | Laser photocoagulation (to the cyclodialysis cleft), continued observation |
| Within 6 months | Surgery (cyclopexy, bleb revision, scleral buckling, etc.) |
Hypotony maculopathy may resolve spontaneously, so conservative treatment is attempted first. However, if low intraocular pressure persists for more than 3 months, permanent visual impairment is likely, so surgical intervention should be considered within 1 to 6 months if conservative treatment fails. In particular, for marked hypotony with intraocular pressure of 4 mmHg or less, restoration of intraocular pressure within 2 months is desirable.
If intraocular pressure of 4 mmHg or less continues for a long time, fibrosis within the retina, sclera, and choroid may progress, leading to irreversible visual impairment. Restoration of intraocular pressure within 2 months is considered an important guideline. If intraocular pressure is higher than 4 mmHg, recovery may be possible even after about six months.
If intraocular pressure is restored early, improvement in visual function can be expected. On the other hand, if photoreceptor folds or fibrosis of the sclera and choroid become established, irreversible visual impairment remains 9). If intraocular pressure of 4 mmHg or less persists for 2 to 3 months, metamorphopsia and relative central scotoma tend to remain.
Lee & Woo (2021) reported two cases of hypotony maculopathy (53-year-old woman and 20-year-old man, South Korea) that developed after vitrectomy for epiretinal membrane removal. Both presented with unmeasurable low intraocular pressure after 25-gauge sutureless vitrectomy, and OCT identified characteristic photoreceptor folds and hyperreflectivity of the Henle fiber layer. Even after normalization of intraocular pressure, photoreceptor damage persisted, and visual acuity at one year was worse than before surgery. Previous vitrectomy history, young age, and myopia were listed as risk factors for hypotony maculopathy 9).
Barbosa et al. (2022) reported a case of a woman in her 70s who developed hypotony maculopathy with intraocular pressure of 2 mmHg three years after non-penetrating glaucoma surgery (deep sclerectomy). Complete recovery was achieved after eight weeks of dexamethasone eye drops five times daily and cyclopentolate twice daily, but recurrence occurred two months after stopping steroids. When steroid eye drops were resumed and continued at a maintenance dose, stable intraocular pressure (14–17 mmHg) and good visual acuity were maintained for 14 months 14). This is an interesting report applying the characteristics of steroid responders to treatment.
Maheshwari et al. (2022) reported a minimally invasive technique of suturing the scleral flap transconjunctivally without incising the conjunctiva 3). In a 70-year-old male glaucoma case who developed severe hypotony (1 mmHg) and 360-degree choroidal detachment after combined cataract and glaucoma surgery, this technique resolved the choroidal detachment and improved both intraocular pressure and visual acuity. This technique is introduced as a promising method that is minimally invasive and can be performed on an outpatient basis.
Lima-Fontes et al. (2022) reported a case of a 52-year-old man with pseudoxanthoma elasticum who developed hypotony maculopathy after intravitreal ranibizumab injection (after the 78th injection). The cause was scleral dehiscence at the injection site with a 30-gauge needle. High myopia, pseudoxanthoma elasticum, repeated injections, and absence of vitreous due to prior vitrectomy were considered factors of scleral fragility. Recovery was achieved with scleral suturing and atropine and dexamethasone eye drops 11).
Markopoulos et al. (2023) reported a 78-year-old man who developed peripapillary retinoschisis (PPRS) associated with low intraocular pressure (6 mmHg) after trabeculectomy. PPRS completely resolved after 4 weeks of treatment with dexamethasone 0.1% eye drops twice daily and nepafenac eye drops three times daily, and intraocular pressure recovered to 16 mmHg. It is speculated that the mechanism of PPRS development involves changes in capillary hydrostatic pressure gradient due to low intraocular pressure, promoting fluid movement into the extracellular space15).
For refractory hypotony maculopathy, methods combining vitrectomy with internal limiting membrane (ILM) peeling and flattening of chorioretinal folds using perfluorocarbon liquid (PFCL) have been reported. These are all at the case report level and have not been established as standard treatment.
