A 67-year-old man was referred for evaluation of a small mass on the sclera of the right eye. Ultrasound biomicroscopy of the mass suggested the diagnosis of Axenfeld loop.
From the Department of Ocular Oncology, Princess Margaret Hospital/UHN, Toronto, Ontario, Canada.
The authors have no financial or proprietary interest in the materials presented herein.
The authors thank Tatyana Milman, MD, Co-director, Ophthalmic Pathology, Institute of Ophthalmology and Visual Science, UMDNJ-New Jersey Medical School.
Address correspondence to Ronaldo A. Santiago, MD, Department of Ocular Oncology, Princess Margaret Hospital, 610 University Avenue Toronto, Ontario M5G 2M9, Canada. E-mail: firstname.lastname@example.org
Received: November 24, 2011
Accepted: May 29, 2012
Posted Online: August 02, 2012
Ultrasound Biomicroscopy Diagnosis of an Axenfeld Loop
Axenfeld first described intrascleral nerve loops of the long, posterior ciliary nerves. Since his description, there have been several reports in the literature of these lesions being mistaken for other pathologies requiring unnecessary investigative procedures.1 We describe a patient referred for a suspicious lesion in his right eye that was diagnosed as an Axenfeld loop with ultrasound biomiscroscopy.
A 67-year-old man was referred for evaluation of a small mass on the sclera of the right eye. He had no ocular symptoms and could not recall when this lesion first appeared in the eye (Fig. 1). On examination, best-corrected visual acuity was 20/20 in both eyes. The slit-lamp examination was unremarkable for both eyes except for the presence of a slightly raised, 1.5-mm diameter scleral nodule at the 5-o’clock meridian. The nodule was translucent, and it was not attached to the overlying conjunctiva. There was no associated pigmentation, dilated vessels, or scleral thinning detected on clinical examination. Ultrasound biomicroscopy was performed and showed a lesion with low internal reflectivity elevating the episclera, traversing the scleral wall and entering the suprachoroidal space (Fig. 2). It extended to the tip of the pars plana. No other pathology could be demonstrated by ultrasound biomicroscopy. The ciliary body appeared normal. The findings were consistent with a non-inflammatory, non-neoplastic process and suggestive of the diagnosis of Axenfeld loop.
Figure 1. Slit-lamp photograph of the lesion showing an elevated semi-translucent episcleral nodule.
Figure 2. Ultrasound biomicroscopy image of Axenfeld loop as a lesion with low internal reflectivity elevating the episclera, traversing the scleral wall and entering the suprachoroidal space. Arrows show surrounding anatomy: 1 = sclera; 2 = conjuunctiva; 3 = Axenfeld loop.
Axenfeld nerve loops are fairly common, but large loops are rarely seen. It has been reported that approximately 12% of eyes have nerve loops and 1% are bilateral. The intrascleral nerve loop of Axenfeld is an extension of the posterior ciliary nerve. It makes a loop through the sclera in the region of the anterior ciliary arteries or between the rectus muscle insertions. Histopathology of Axenfeld loops shows the nerves penetrating the sclera and bending 180 degrees, creating a mushroom-shaped loop on the scleral surface (Fig. 3). Nerve loops are not found in the horizontal plane anterior to the medial or lateral rectus muscles and 70% are present inferiorly.2 When part of the long posterior ciliary nerve that traverses the sclera and loops back to the ciliary body is associated with neurilemmal or connective tissue proliferation, it may form a prominent elevation 4 to 7 mm posterior to the limbus.3 The loop may demonstrate pigmentation at its scleral entry. The pigment in the nerve loop may increase over time, and the loop could then be mistaken for a foreign body, a nevus, or an invasive malignant melanoma.4 The nerve loops are generally asymptomatic, but they may produce symptoms of irritation and tenderness on manipulation.
Figure 3. Hematoxylin–eosin staining of a histopathologic section of an Axenfeld loop demonstrating surrounding anatomy corresponding to findings in Figure 2: 1 = sclera; 2 = conjunctiva; 3 = Axenfeld loop (original magnification × 100) (photograph courtesy of Dr. Tatyana Milman).
In this report, we present the ultrasound biomicroscopy image of an Axenfeld loop as a non-invasive diagnostic method. This image shows a low reflective lesion penetrating the sclera and connecting a superficial component to a choroidal component. The ultrasound biomicroscopy images are comparable to the histologic appearance of such a lesion as illustrated on Figure 3. Ultrasound biomicroscopy findings clearly differentiate an Axenfeld loop from other lesions, including ones of neoplastic nature with episcleral or extrascleral extension, which makes it a useful tool in the differential diagnosis of episcleral lesions.
- : Crandall AS, Yanoff M, Schaffer DB. Intrascleral nerve loop mistakenly identified as a foreign body. Arch Ophthalmol. 1977;95:497–498. doi:10.1001/archopht.1977.04450030139020 [CrossRef]
- : Stevenson TC. Intrascleral nerve loops: a clinical study of frequency and treatment. Am J Ophthalmol. 1963;55:935–939.
- : Reese AB. Intrascleral nerve loops. Arch Ophthalmol. 1931;6:698–703. doi:10.1001/archopht.1931.00820070725005 [CrossRef]
- : Katz D. Intrascleral nerve loops. Indian J Ophthalmol. 1971;19:2–6.