This small retrospective study used high resolution optical coherence tomography (OCT) Heidelberg Spectralis to identify features which could determine the underlying aetiology of peripheral corneal thinning. Ten patients were included; five with diagnoses of degenerative peripheral thinning; Terrien’s marginal degeneration and five with inflammatory peripheral corneal thinning on a background of rheumatoid arthritis, varicella zoster infection or inflammation not associated with any systemic condition. All patients in the inflammatory group were symptomatic with pain, tearing and redness at some point in their disease history, whereas the degenerative group patients were symptom free. At the time of the OCT only one patient in the inflammatory group had concurrent symptoms, and two were using topical anti-immunosuppressive therapy. OCT images of the degenerative group demonstrated corneal thinning, associated with focal stromal loss, an intact epithelium, and normal stromal reflectivity directly under the epithelium in the area of thinning. OCT images of patients in the inflammatory group showed broad corneal tissue loss with a hyper-reflective band directly below the intact epithelium in the area of corneal thinning. This hyper-reflective band was stipulated to be a sign of previous inflammatory response or indicate stromal scarring. It is thought to be a marker of prior corneal inflammation and could be used to help distinguish underlying aetiology of peripheral corneal thinning using OCT. Further studies are needed in more patients including those with acute peripheral ulcerative keratitis (PUK) and Mooren’s ulcers.