Routine eye exam reveals distinctive macular lesion

A 36-year-old Caucasian male presented with a chief complaint of mild blur in the left eye at distance and near that improved to 20/20 with spectacle correction. The patient’s medical and ocular histories were unremarkable without ocular trauma. He denied taking any medications.

Extraocular motilities had full range of motion. Confrontation visual fields were full to finger counting in both eyes. Both pupils were equal, round and reactive to light and accommodation, without a relative afferent pupillary defect. Anterior segment biomicroscopy was negative for disease. IOP was 19 mm Hg OD and 20 mm Hg OS as measured by noncontact tonometry.

Dilated fundus examination showed round, well-perfused optic nerves with distinct margins. Fundoscopy revealed a well-demarcated, hypopigmented lesion with slightly tapered ends temporal to the macula in the right eye, and the left eye was free of pathology.

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Source: Mary G. Hoang, OD

This patient was diagnosed with torpedo maculopathy, which was first described as a “solitary, sharply circumscribed, oval, pinkish-white, placoid lesion with a wedge-shaped ‘tail’ at the level of retinal pigment epithelium (RPE)” (Roseman et al.). It is a congenital and nonprogressive, amelanotic lesion of the RPE although hyperpigmentation may be present at its tail. It is unilateral and located along the horizontal raphe, temporal to macula. Acuity and visual field testing are generally normal; however, patients may rarely notice a mild scotoma. Hyper-reflectivity of the RPE and choroid on OCT at the lesion location is an early clinical sign, and mild outer retinal attenuation may be present.

There are several theories regarding torpedo maculopathy’s etiology, including in utero alteration of choroidal or ciliary vasculature in the macula, underdevelopment of the retinal nerve fiber layer at the horizontal raphe or RPE defects at the temporal bulge during development. Because most patients are asymptomatic, its diagnosis is usually incidental.

Wong and colleagues put forth a classification system of torpedo maculopathy based on spectral domain OCT observations. Type 1 lesions exhibit mild outer retinal changes including thinning at the interdigitation zone (IZ) and ellipsoid zone (EZ) without outer retinal cavitation or inner retinal changes. Type 2 lesions include all of the type 1 clinical signs plus outer retinal cavitation. Type 1 lesions occur more commonly in children, and type 2 is typically found in adults; therefore, it is suggested the classification system may represent the same disease process but at different stages. Recent literature identifies a possible type 3 lesion that exhibits cavitation of the lesion with associated retinal thinning, increasing reflectivity of inner retinal spaces, and presence of a subretinal cleft (Tripathy et al.). The patient’s OCT findings indicated a type 2 torpedo maculopathy lesion.

Differential diagnoses

Because of torpedo maculopathy’s distinct clinical presentation, seldom other retinal lesions such as congenital hypertrophy of retinal pigment epithelium (CHRPE), congenital albinotic spots of retinal pigment epithelium or chorioretinal scarring would be possible differential diagnoses. Chorioretinal scarring is unlikely due to the patient’s absence of ocular trauma.

The prevalence of CHRPE is approximately 1.2% and it can be solitary or grouped (Coleman et al.). CHRPE vary from gray to brown to black in color, are typically oval or round in shape with distinct borders, and are approximately 1 to 2 disc diameters in size. Conversely to torpedo maculopathy lesions, CHRPE are commonly located temporal to the optic nerve within the peripheral retina. Hypopigmented lacunae can occur within CHRPE that can progressively enlarge, especially with age.

OCT imaging of CHRPE demonstrates thickened RPE with outer retinal loss extending from photoreceptors to outer nuclear layer, and a subretinal cleft may be present. The lesion will hypoautofluoresce; however, lacunae within CHRPE with exhibit hyperautofluorescence on fundus autofluorescence (FAF) imaging.

Grouped, bilateral CHRPE, otherwise known as “bear tracks,” is an early diagnostic marker associated with Gardner’s syndrome, which is a subtype of familial adenomatous polyposis. Lesions attributed to Gardner’s syndrome present with an ovoid shape with a distinct, fishtail-like taper to one or both ends that is usually hypopigmented at one end.

Patient management

Although torpedo maculopathy is distinctive in its clinical presentation, it is important for clinicians to note that this disease is not due to an absence or excavation of retina but rather a hypopigmented presentation of RPE.

Due to this patient’s lack of symptoms and stability of disease process, no further testing is indicated at this time. Rarely, choroidal neovascularization or visual field defects corresponding to the lesion can occur, and self-monitoring of central vision with an Amsler grid and annual dilated exams are appropriate.

References:

Coleman P, et al. Ophthalmic Physiol Opt. 2007;doi:10.1111/j.1475-1313.2007.00513.x.

Golchet PR, et al. Br J Ophthalmol. 2010;doi:10.1136/bjo.2009.162669.

Kanski JJ, Bowling B, Nischal KK, Pearson A. 2011. Clinical Ophthalmology: A Systematic Approach; 7th ed. New York:Elsevier/Saunders.

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Kim DY, et al. Retina. 2010;doi:10.1097/IAE.0b013e3181cea5a5.

Pian D, et al. Optom Vis Sci. 2003;doi:10.1097/00006324-200308000-00008.

Roseman RL, et al. Arch Ophthalmol. 1992;doi:10.1001/archopht.1992.01080220020005.

Shields C, et al. Arch Ophthalmol. 2010;doi:10.1001/archophthalmol.2010.132.

Shirley K, et al. Eye. 2018;doi:10.1038/s41433-018-0074-7.

Teitelbaum BA, et al. J Am Optom Assoc. 1997;68:373–376.

Trevino R, et al. Optom Vis Sci. 2014;doi:10.1097/OPX.0000000000000181.

Tripathy K, et al. Indian J Ophthalmol. 2018;doi:10.4103/ijo.IJO_656_18.

Villegas VM, et al. Ophthalmic Surg Lasers Imaging Retina. 2014;doi:10.3928/23258160-20140410-01.

Wong EN, et al. Clin Exp Ophthalmol. 2015;doi:10.1111/ceo.12435.

For more information:

Mary G. Hoang, OD, is an assistant professor at the Southern College of Optometry in Memphis, Tenn. She can be reached at: mhoang@sco.edu.

Edited by Leo P. Semes, OD, FAAO, a Primary Care Optometry News Editorial Board Member and Professor Emeritus in the Department of Optometry and Vision Science at the University of Alabama at Birmingham. He can be reached at: leopsemes@gmail.com.

Disclosure: Hoang reports no relevant financial disclosures.