A 22-year-old male presented for a routine check up. Uncorrected visual acuity was 20/20 in both eyes. Slit lamp examination revealed superior yellow-white stromal opacities extending circumferentially from 9 o’clock to 3 o’clock in the right eye [Fig. 1a and b] and around 12 o’clock in the left eye [Fig. 2a and b] along with superficial vascularisation and lipid deposition at the leading edge of the corneal thinning. There was no epithelial defect. Intraocular pressure was 16 mmHg in both eyes using Goldmann applanation tonometry. A dilated fundus examination was within normal limits bilaterally.
Figure 1.
(a) Slit lamp photograph of the right eye showing superior lipid deposition and vascularization with a clear zone separating the limbus and an intact epithelium. (b) There was stromal thinning preceding the lipid deposits. (c) Anterior segment OCT through this part revealed, in addition, hyporeflective spaces in the anterior stroma
Figure 2.
(a) Slit lamp photograph of the left eye showing lipid deposition and vascularization around the 12 o’ clock position. (b) Mild stromal thinning was also present. (c) Anterior segment OCT through the involved cornea demonstrated hyperreflectivity in the anterior stroma
Keratometric measurements were 44.4 × 43.8 and 44.7 × 44.4 dioptres, respectively. Ultrasonic pachymetry revealed central and mean peripheral thickness of 514 μm and 476 μm respectively in the right cornea. Corresponding values for the left cornea were 508 μm and 518 μm. The patient underwent anterior segment optical coherence tomography AS-OCT of both eyes using RTVue-100°CT (Optovue, Inc., Fremont, California, USA) with a corneal adaptor module (CAM). AS-OCT confirmed the presence of an intact epithelium and peripheral stromal thinning. In addition, hyporeflective spaces were observed in the anterior stroma in the right eye [Fig. 1c]. These spaces were less prominent in the left eye [Fig. 2c].
A diagnosis of bilateral Terrien marginal degeneration (TMD) was made. At 3 months follow up the clinical picture remained stable. The patient was educated about the progressive nature of the condition and advised eye protection and regular follow up.
TMD is a rare, slowly progressive, bilateral, though asymmetric, peripheral corneal ectatic disorder seen in males in the third to fifth decade of life. Patients are often asymptomatic but may complain of irritation or decreased vision due to against-the-rule or oblique astigmatism. Initially it presents as small, yellowish-white stromal opacities composed of lipids with superficial vascularization, which begin superiorly and spread circumferentially. There is a distinct interval between the limbus and site of infiltration. With progression, a gutter may form in the affected area due to stromal thinning, leaving the epithelium intact.[1] Corneal perforation is rare, and the risk can be further reduced by use of polycarbonate lenses.[2]
AS-OCT provides non invasive, cross sectional, high resolution images of the corneal microstructure. However, its utility in peripheral corneal thinning disorders has not been well elaborated. Hattori et al. demonstrated cavity formation in two patients with TMD in the area of peripheral corneal thinning.[3] A novel staging system has been proposed based on corneal curvature as assessed by AS-OCT in pateints with TMD.[4] Both eyes of the above case belonged to stage 2 as per this classification. Recently, differentiating features between TMD and inflammatory peripheral corneal ectatic disorders on AS-OCT have been described.[5] In the above patient, AS-OCT revealed hyporeflective spaces in the peripheral cornea in TMD, in addition to the peripheral thinning that is characteristic of TMD. This was observed in the eye that had greater involvement clinically. This has not been described previously and may proved new insights into the pathogenesis of TMD.
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The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
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References
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