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Fundus lesion targets the central macula
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The evaluation of a fundus lesion requires pattern recognition. Differentiating sight-threatening lesions from those with a benign prognosis is always the first priority. This case demonstrates that for some lesions, the unique features on examination may be all that is required to reassure a patient of a benign diagnosis. Multimodal imaging serves to further our understanding of the pathophysiology and classification of rare macular lesions when a significant number of examples is added to the literature.
The case
A 21-year-old Asian man was referred to our clinic to rule out choroidal melanoma. The patient complained of a gradual visual decline at distance over the past several months but was otherwise healthy. A complete review of systems, ocular history and family history was negative.
On examination, visual acuity was 20/30 in the right eye and 20/40 in the left, with manifest improvement to 20/20 in each eye with –5.00 +1.00 × 090 in the right eye and –4.50 +1.00 × 090 in the left. The pupils were round and reactive. There was no afferent pupillary defect. Extraocular movements were smooth and full. The patient was orthophoric, and visual fields were full to confrontation bilaterally. IOP was 16 mm Hg in the right eye and 18 mm Hg in the left. Slit lamp examination showed normal lids and lashes. There was a normal tear film and conjunctiva and clear corneas. The anterior chambers were deep and quiet. The irises were round and free from neovascularization. There was trace nuclear sclerosis in each eye.
David S. Chin Yee
Michael D. Ober
Funduscopic examination in the right eye showed a clear vitreous with a normal disc, macula and vessels. Indirect ophthalmoscopy showed the periphery was flat without breaks.
Funduscopic examination in the left eye showed sharp disc margins with a clear vitreous and a cup-to-disc ratio of 0.5. The macula was flat. There was a hypopigmented, ovoid lesion temporal to the macula with a pigmented border superiorly and inferiorly and peaks laterally and temporally. The vessels were normal, and indirect ophthalmoscopy showed the remainder of the periphery was unremarkable (Figure 1).
Figure 1. Color fundus photo of patient described in article showed ovoid lesion temporal to the macula with a pigmented border superiorly and inferiorly and peaks laterally and temporally.
Images: Chin Yee DS, Ober MD/Griffin C
Figure 2. OCT of the lesion in Figure 1, showinged thinning of the photoreceptor layer and RPE but no subretinal fluid or cystic change.
Images: Chin Yee DS, Ober MD/Griffin C
Optical coherence tomography through the lesion showed thinning of the photoreceptor layer and retina pigment epithelium (RPE) but no subretinal fluid or cystic change. There was also no significant change in choroidal thickness (Figure 2).
The diagnosis
Torpedo maculopathy is a unilateral torpedo-shaped RPE defect located in the temporal macula. It has been described as an asymptomatic, congenital, solitary, sharply circumscribed, hypopigmented lesion of the RPE. The term torpedo maculopathy was first introduced in 1993 by Daily due to its location in the temporal fovea and tip, which points toward the central macula.
Clinically, the lesion appears as an oval, flat, hypopigmented lesion with well-defined margins in the temporal macula, centered at the horizontal raphe, with the tip pointed toward the center of the macula, as noted in our patient (Figure 1). The temporal tail of the lesion also tends to have increased pigmentation and to be longer in the horizontal axis than in the vertical axis; it usually does not involve the foveal center (Figures 1 and 4).
Figure 3. Blue light FAF of the lesion in Figure 1 showed mottled hyper- and hypo-autofluorescence.
Images: Chin Yee DS, Ober MD/Griffin C
Figure 4. Fundus photo of a second patient with Torpedo Maculopathy demonstrating typical hypopigmented lesion pointing at the fovea with increased pigmentation at the temporal tail end.
Images: Chin Yee DS, Ober MD/Duffy K
The differential diagnosis includes infectious chorioretinal scars (eg, toxoplasmosis) and other RPE developmental abnormalities. The latter includes large hypertrophic epithelial cells containing many melanin granules (congenital hypertrophy of the RPE); hypertrophic cells with presumed white pigment of an unknown nature (congenital albinotic spots of the RPE-grouped type); and RPE cells containing no pigment (congenital albinotic spot of the RPE-solitary type). Care must also be taken to distinguish this lesion from those associated with familial adenomatous polyposis (Gardner’s syndrome) in which the diagnosis carries a near 100% risk of colorectal malignancy without treatment at a young age. Lesions from the latter tend to be multiple (also known as grouped pigmentation), are not restricted to the horizontal raphe, and vary in size, shape, color and degree of pigmentation.
Humphrey visual field testing demonstrates a paracentral scotoma corresponding to the lesion. OCT findings include normal inner with thinned outer neurosensory retina overlying a wide cleft and a nearly absent RPE signal resulting in increased optical transmission to the choroid (Figure 2). Fluorescein angiography demonstrates transmission hyperfluorescence of the lesion. Blue light fundus autofluorescence (FAF) of the lesion showed mottled hyper- and hypo-autofluorescence (Figure 3) in our case, but it may show uniform hypo-autofluorescence, especially with fundus camera-based systems due to the absence of RPE.
Figure 5. OCT of same eye as in Ffrom figure 4 showing abnormal photoreceptor and RPE with mild cystic change.
Images: Chin Yee DS, Ober MD/Duffy K
Figure 6. Blue light FAF, again showing mottled hyper- and hypo-autofluorescence, and temporal hypo-autofluorescence correlating with blocking from increased pigmentation at temporal tail end of lesion.
Images: Chin Yee DS, Ober MD/Duffy K
Patients usually are asymptomatic, and the lesion is found most commonly on routine ophthalmological examination. Previous literature has denoted the lesion as being an RPE nevus, but more recent findings, as supported by ancillary tests and seen in our patient on spectral-domain OCT and FAF, suggest the presence of thin and non-functional RPE. The peculiar location and size of the lesion may be explained by its proximity to the emissary canal of the long temporal posterior ciliary artery and the long posterior ciliary nerve.
During embryological development, modification of the sclera allows passage of the nerve and artery from the sclera to the choroid in this pathway. This may in turn have an impact on the developing choroid and RPE, resulting in irregular RPE and leading to the lesion known as torpedo maculopathy. The course of this congenital lesion is benign, with most patients developing no change in appearance or function of the involved eye. Figures 4 through 6 show the variation in lesions in a second asymptomatic patient. Due to its benign nature, routine annual follow-up was recommended for each patient.