Torpedo Maculopathy

Key Points at a Glance

Key Points of This Disease

• Torpedo maculopathy is a hypopigmented lesion shaped like a torpedo (with the tip pointing toward the fovea) located on the temporal side of the macula.
• It is thought to be caused by a congenital abnormality of the retinal pigment epithelium (RPE).
• Almost all cases are asymptomatic and are often discovered incidentally during fundus examination.
• Typically unilateral and solitary, with very slow progression.
• Classified into four types by OCT according to the Wong classification.
• Most cases require only observation, but those complicated by choroidal neovascularization (CNV) need treatment.
• The most plausible mechanism is the “temporal bulge theory” during embryonic development.

1. What is Torpedo Maculopathy?

Torpedo Maculopathy is a congenital hypopigmented lesion located temporal to the macula. It is named for its torpedo-like shape, with the narrow tip pointing toward the fovea.

This is a relatively rare disease first reported by Roseman and Gass in 1992. The prevalence is estimated at approximately 2 per 100,000 in the population under 16 years of age. It is typically unilateral and solitary, although a few cases of multiple lesions or bilateral involvement have been reported (Menezes et al. 2021, systematic review of 110 cases).

A congenital abnormality of the RPE is considered the main etiology, but the detailed pathogenesis remains unclear (see “Pathophysiology” section).

Other Names

English name: Torpedo Maculopathy

Also known as: Solitary Hypopigmented Nevus, Congenital Retinal Pigment Epithelium Defect (as referred to in some literature)

First reported: 1992 (Roseman & Gass)

Epidemiology

Prevalence: Approximately 2 per 100,000 people (under 16 years of age)

Sex difference and laterality: No clear predilection

Onset pattern: Typically unilateral and solitary

Characteristics of the lesion

Shape: Torpedo-shaped (tip pointing toward the fovea)

Color tone: Hypopigmented (depigmented, grayish-white)

Location: Temporal to the horizontal raphe of the macula and around the fovea

Border: Well-defined

Q In what situation is torpedo maculopathy discovered?

A

Since almost all cases are asymptomatic, it is incidentally discovered during fundus examinations such as health checkups or preoperative tests for other diseases. It is rare for patients to visit a doctor due to subjective symptoms and receive a diagnosis.

2. Main Symptoms and Clinical Findings

Subjective Symptoms

Torpedo maculopathy is almost always asymptomatic. Subjective symptoms such as decreased visual acuity, metamorphopsia, and scotomas are usually not observed. Since the lesion is almost always located outside the fovea, its impact on central vision is extremely small.

Symptoms appear only when secondary changes such as choroidal neovascularization occur.

Clinical Findings

Key fundus findings are as follows.

• Lesion morphology: Hypopigmented lesion with torpedo- or teardrop-shaped outline.
• Orientation of the lesion: The narrow tip (head) points toward the fovea. The tail extends toward the temporal periphery.
• Color: Gray-white to depigmented appearance due to localized loss of RPE pigment. The border with the surrounding retina is distinct.
• Retinal vessels: No abnormality in their course over the lesion.
• Unilateral and solitary: Bilateral or multiple occurrences are exceptional.

Q How large is the lesion?

A

The longest diameter of the lesion is generally reported to be about 1 to 5 disc diameters, with individual variation. The lesion size rarely changes significantly over the long term, and in many cases, it remains stable for more than 10 years.

3. Causes and Risk Factors

Etiological Hypotheses

The etiology of torpedo maculopathy has not been established. Currently, four main hypotheses have been proposed.

• Nerve fiber layer hypoplasia hypothesis: A localized developmental defect of the nerve fiber layer on the temporal side of the macula secondarily causes RPE abnormalities.
• Choroidal circulation abnormality hypothesis: Impaired choroidal blood flow during the embryonic period leads to localized RPE differentiation failure.
• Temporal bulge hypothesis: The most plausible hypothesis (see Section 6 for details).
• Intrauterine chorioretinitis theory: This theory proposes that local inflammation due to infection during the fetal period leads to impaired differentiation of the retinal pigment epithelium (RPE).

Neither environmental risk factors nor genetic predispositions have been clearly identified. Reports of familial occurrence are extremely rare.

Impact on Daily Life

Torpedo maculopathy is a congenital condition, and it is believed that lifestyle habits or external factors do not worsen the lesion. It is important to continue regular eye examinations and periodic follow-ups.

4. Diagnosis and Examination Methods

Diagnostic Approach

The diagnosis of torpedo maculopathy is based on a combination of characteristic fundus findings and ancillary tests. When a typical hypopigmented torpedo-shaped lesion is observed on fundus examination, OCT is used to evaluate the internal structure of the lesion and classify its type.

Wong Classification (OCT Type Classification)

The Wong classification based on OCT findings (Wong et al. 2015) is widely used. The original report described a two-type classification: Type 1 (only outer retinal attenuation, no cavity) and Type 2 (outer retinal attenuation plus outer retinal cavity). Subsequently, an expanded classification including subtypes with choroidal neovascularization and subretinal lesions (Type 3 and Type 4) was proposed in later reports and is used clinically in combination.

The following is an overview of the expanded Wong classification.

Type	OCT findings	Notes
Type 1	Only attenuation of the outer retinal layers (ellipsoid zone and interdigitation zone)	Original classification, most common
Type 2	Outer retinal attenuation + outer retinal cavity formation	Original classification, cavitary type
Type 3	Lesion with subretinal component	Suspected choroidal neovascularization
Type 4	Mixed findings (cavity + subretinal lesion)	Most complex type

Ancillary Tests

• Fluorescein angiography (FA): Shows window defect corresponding to the lesion. If choroidal neovascularization is present, leakage findings appear.
• Fundus autofluorescence (FAF): Detected as an area of hypoautofluorescence corresponding to the lesion. This reflects RPE dysfunction.
• Optical coherence tomography (OCT): Provides detailed visualization of structural changes in the RPE and outer retina. This test is essential for Wong classification.
• Optical coherence tomography angiography (OCTA): Allows noninvasive evaluation of the presence of choroidal neovascularization. It is actively used in recent diagnosis.
• Multicolor imaging: Evaluates lesion contours and pigment distribution at multiple wavelengths, useful for lesion mapping.

Differential Diagnosis

It is important to differentiate from the following diseases.

Differential diagnosis	Key differentiating features
Choroidal nevus	Pigmentation present, irregular shape
Chorioretinal atrophy	Progressive and bilateral in course
Vitelliform macular dystrophy	Yellow egg-yolk-like lesions, often bilateral

Q Is OCT examination mandatory?

A

OCT is indispensable for definitive diagnosis and classification of disease type. In particular, evaluation by OCT and OCTA is essential to determine the presence or absence of choroidal neovascularization (Types 3 and 4). Classification of disease type is impossible based on fundus findings alone.

5. Standard Treatment

Observation

The basic treatment is observation. Since most cases are asymptomatic and follow a stable course, active therapeutic intervention is unnecessary. A long-term follow-up case series (Trevino et al. 2024, BMC Ophthalmol) reported that the majority of cases maintained stable lesion size and visual function for over 10 years.

Regular monitoring with fundus examination, OCT, and OCTA is performed to check for the following changes.

• Changes in visual acuity
• Signs of choroidal neovascularization (subretinal fluid, hemorrhage, exudation)
• Morphological changes of the lesion

Management of cases with choroidal neovascularization

When type 3 or 4 is confirmed with choroidal neovascularization, intravitreal injection of anti-VEGF drugs is selected. Treatment indications and strategies follow those for typical exudative age-related macular degeneration.

Caution: Overlooking choroidal neovascularization

Torpedo maculopathy is asymptomatic, so regular follow-up tends to be interrupted. Even when choroidal neovascularization occurs, it may be asymptomatic in the early stages. If decreased vision or metamorphopsia appears, it is important to promptly see an ophthalmologist and undergo detailed examination with OCT and OCTA.

Q Does torpedo maculopathy heal on its own?

A

Spontaneous regression has not been reported. However, most cases remain stable throughout life. Unless complications such as choroidal neovascularization occur, it often does not significantly affect vision.

6. Pathophysiology and Detailed Mechanism of Onset

Temporal bulge theory (most plausible hypothesis)

The most widely supported mechanism at present is related to the temporal bulge during embryonic development.

During fetal eye development, a transient accumulation of RPE cells known as the “temporal bulge” occurs on the temporal side of the macula (most prominent around 4–6 months of gestation, regressing toward birth). The location of this bulge anatomically corresponds to the predilection site of torpedo maculopathy lesions in adults (Trevino et al. 2014).

According to this theory, when the temporal bulge forms during embryonic development, local RPE cells deviate from normal differentiation and maturation, leading to incomplete pigmentation and resulting in a permanent hypopigmented lesion.

Anatomical Location of the Lesion

The tip of the torpedo-shaped lesion points toward the fovea because the lesion is located on the macular horizontal raphe, and its axis aligns with the line connecting the fovea and the temporal periphery. This unique orientation has been suggested to be related to embryonic vascular development and the course of nerve fibers.

Comparison of Four Etiological Theories

Nerve Fiber Layer Hypoplasia Theory

Overview: A theory that the retinal nerve fiber layer on the temporal side of the macula fails to develop locally, secondarily affecting the RPE.

Evidence: Association with thinning of the outer retinal layer in the lesion area.

Choroidal Circulation Abnormality Theory

Overview: A theory that fetal choroidal blood flow is locally reduced, impairing RPE differentiation and pigmentation.

Evidence: Findings of choroidal thinning beneath the lesion.

Temporal bulge theory (most plausible)

Overview: This theory proposes that RPE differentiation is impaired at the site of the temporal bulge formed during the embryonic period.

Evidence: The predilection site of the lesion anatomically coincides with the temporal bulge.

Intrauterine Chorioretinitis Theory

Overview: This theory proposes that local inflammation due to prenatal infection (e.g., viruses, protozoa) inhibits RPE development.

Evidence: Histological similarity to post-inflammatory scars.

7. Latest Research and Future Perspectives (Research-stage Reports)

For patients: Please read this

The following content is currently at the research stage or under clinical trial and is not standard treatment available at general hospitals. It is reference information for professionals regarding future medical developments.

Establishment of OCT-based disease classification and its clinical significance

In recent years, the widespread use of the Wong classification has standardized OCT-based disease classification. This classification contributes to risk stratification for choroidal neovascularization and helps determine follow-up frequency. Regarding the formation mechanism of Type 2 cavities, a combined involvement of localized outer retinal degeneration, fluid accumulation, and RPE defects has been suggested, but details remain unclear.

New evaluation using OCTA and multicolor imaging

The introduction of OCTA has enabled non-invasive and highly sensitive detection of choroidal neovascularization. Regular monitoring with OCTA is also considered useful in torpedo maculopathy, and it is attracting attention as an alternative evaluation method to conventional fluorescein angiography.

Multicolor imaging (multi-wavelength scanning laser ophthalmoscopy) can depict pigment changes and contours of lesions in greater detail. Future large-scale cohort studies are expected to accumulate data on the natural course, rate of choroidal neovascularization, and long-term prognosis for each disease subtype.

Q Is it possible to lose vision in the future?

A

In many cases that do not develop complications such as choroidal neovascularization, vision is maintained throughout life. However, in disease types with a high risk of choroidal neovascularization, such as Type 3 and 4, continuing regular OCT and OCTA monitoring and early therapeutic intervention are key to preserving vision.

References

1. Wong EN, Fraser-Bell S, Hunyor AP, Chen FK. Novel optical coherence tomography classification of torpedo maculopathy. Clin Exp Ophthalmol. 2015;43(4):342-348. doi:10.1111/ceo.12435. PMID: 25266677
2. Trevino R, Kiani S, Raveendranathan P. The expanding clinical spectrum of torpedo maculopathy. Optom Vis Sci. 2014;91(4 Suppl 1):S71-S78. doi:10.1097/OPX.0000000000000181. PMID: 24584305
3. Raval V, Rao S, Sudana P, Das T. Torpedo Maculopathy. J Ophthalmic Vis Res. 2020;15(1):113-115. doi:10.18502/jovr.v15i1.5960. PMID: 32095216
4. Menezes K, Mancera N, Patel H, Kattih Z, Mhaskar R. Torpedo Maculopathy: A Systematic Review of Case Reports. Ophthalmic Surg Lasers Imaging Retina. 2021;52(2):78-83. doi:10.3928/23258160-20210201-04. PMID: 33626168
5. Trevino RC, Ridder WH 3rd, Laul A, Hill J. Long-term follow-up of torpedo maculopathy: a case series and mini-review. BMC Ophthalmol. 2024;24(1):5. doi:10.1186/s12886-023-03254-z. PMID: 38172762