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Jun Shimazaki, Naoyuki Maeda, Osamu Hieda, Yuichi Ohashi, Akira Murakami, Kohji Nishida, Kazuo Tsubota, Japan Pellucid Marginal Corneal Degeneration Study Group; National Survey of Pellucid Marginal Corneal Degeneration in Japan. Invest. Ophthalmol. Vis. Sci. 2013;54(15):884.
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Pellucid marginal corneal degeneration (PMCD) is a rare, progressive ecstatic disorder characterized by thinning of peripheral cornea. Early detection of the disorder is important to avoid keratectasia following refractive surgery. However, there is no diagnostic criterion, and large-scale clinical reports have been scarce. Here, we report a result of national survey on PMCD in Japan.
We sent questionnaire to all members of the Japan Cornea Society. The questionnaire included demographic and clinical findings of PMCD and its suspects. Eyes with a history of corneal surgery, active inflammation, and other corneal diseases were excluded.
There were responses from 27 medical facilities, and data of 320 patients (527 eyes) were collected. They were 240 males and 80 females, with a mean age of 38.9 ± 10.6 years. Approximately 32 % of cases showed unilateral involvement, and 97 (30.3%) of them had allergic diseases such as asthma, atopic dermatitis, seasonal allergic rhinitis or conjunctivitis. Hard contact lenses were the most common optical correction devise (61%), followed by soft contact lenses (18%), and glasses (12%). Approximately half of them (51%) had more than 20/20 corrected visual acuity and only 4% showed less than 20/200. We classified them into following 3 categories; 1) Classical PMCD; presence of band-shaped peripheral corneal thinning detected either by slit-lamp biomicroscopy or pachymetric map (n=145 eyes), 2) PMCD suspects; Eyes with “crab claw pattern” in corneal topography without presence of obvious peripheral thinning (n=266 eyes), and 3) Others (n=116 eyes). There were no significant differences among the three groups neither in demographic profile nor ophthalmic findings including the topographic patterns.
We conducted a largest scale of clinical survey of PMCD and its suspects. In our series, we observed a male predominance, relatively high incidence of unilateral involvement and associated allergic diseases. Corneal topography was used most commonly in diagnosis, however, “crab claw pattern” in topography itself seemed to have limited diagnostic value. As it is likely that there is an overlap with other diseases such as keratoconus, further refinements in diagnostic methods are needed.
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