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Transiency of Fleischer's Rings in Forme-Fruste Keratoconus
Keratoconus has characteristic biomicroscopic signs that increase in prevalence as the disease progresses. Vögt striae and Fleischer's ring are considered pathognomonic 1 ; however, no comment has been made regarding their relative permanency. This report describes the bilateral disappearance of Fleischer's rings in a patient with forme-fruste keratoconus after orthokeratology.
Baseline corneal topography demonstrated subtle inferior-superior axial power asymmetry (Fig 1C, D, available at http://aaojournal.org); the corneal apices were decentered inferonasally, consistent with the location of Fleischer's rings (both eyes). Videokeratographic indices were used to quantify baseline corneal asymmetry (Table 1, available at http://aaojournal.org); 1 index was beyond normative ranges in the right eye and 4 parameters were outside expected levels in the left eye. Central-corneal thicknesses were: right eye, 535 m; left eye, 512 m.
Given these corneal findings, a corneal specialist assessed the patient's suitability for orthokeratology. Ophthalmologic opinion was that given the long-term refractive stability and excellent BCVAs, forme-fruste keratoconus did not contraindicate orthokeratology.
In July 2010, the patient commenced overnight-wear of Paragon CRT (Paragon Vision Sciences; Mesa, AZ) orthokeratology lenses. The corneal area inclusive of the Fleischer's rings was overlaid by the lens optic zone (Fig 1E, F, available at http://aaojournal.org). After 3 months, unaided vision was 20/10 in the right eye and 20/10 in the left. Videokeratographic maps demonstrated large treatment zones with mild inferior displacement. Fleischer's rings were absent; each cornea had a normal biomicroscopic appearance (Fig 2, available at http://aaojournal.org). This patient has been successfully undertaking orthokeratology without adverse event for more than 2 years; the Fleischer's rings have not reappeared.
Superficial corneal iron lines develop in physiologic and pathologic contexts. The Hudson-Stähli line occurs in the aging cornea. Refractive procedures including radial keratotomy, intrastromal corneal ring, and LASIK can induce corneal iron lines. Ocular disease also produces characteristic pigmented corneal arcs; Stocker's line for pterygia, Ferry's line at filtering blebs, and Fleischer's ring in keratoconus. Although the emergence of 'new' iron lines is well-documented, this is the first report describing the loss of a Fleischer's ring.
Fleischer's rings consist of ferritin deposits within basal corneal epithelial cells that form at sites of local discontinuity in curvature. 2 Although the reported prevalence of the rings in keratoconus is 87%, 3 their pathogenesis remains unclear.
Orthokeratology involves using reverse-geometry, rigid, gas-permeable contact lenses to reduce manifest refractive error. 4 In myopic orthokeratology, the central zone of the lens imparts a positive hydraulic pressure to induce corneal flattening; the epithelium is compressed such that basal cells assume a rounded configuration compared with their normally elongated morphology. Both the decentered corneal apices and region possessing Fleischer's rings were therefore remolded to a flatter curvature. Although only a low myopic correction, this degree of remodeling was sufficient to induce the necessary, and presently poorly understood, epithelial changes to reverse the iron deposition.
Should the disappearance of a Fleischer's ring be specifically related to a reduction in corneal apical power, similar effects would be expected after corneal cross-linking for keratoconus; there are currently no published reports to this effect. A further possibility is that orthokeratology alters basal epithelial cell turnover. This hypothesis is supported by evidence that orthokeratology increases epithelial cell proliferation rates. 5 Further work is required to elucidate the mechanism underlying the observation.
This case highlights that Fleischer's rings can occur with mild topographic asymmetry, average central corneal thickness, stable refraction, normal BCVA, normal retinoscopic reflexes, and without other signs of keratoconus. This report also demonstrates that