Acute corneal edema in pellucid marginal degeneration or acute marginal keratoconus

This article reports a case of bilateral corneal pellucid marginal degeneration. The right cornea had an acute hydrops. Both eyes underwent penetrating keratoplasty. A histopathological study of the corneal specimens was performed by light and electron microscopy. The histological changes observed on the right cornea showed breaks on Bowman's layer, edema and disorganization of the stromal collagen, and break of Descemet's membrane. The ultrastructural changes were similar to those observed in acute keratoconus, leading to the belief that these two corneal diseases are closely related.     

Characteristics of keratoconus and pellucid marginal degeneration in mean curvature maps

PURPOSE: To characterize keratoconus and pellucid marginal degeneration (PMD) on mean curvature maps. DESIGN: Observational case series. METHODS: A retrospective analysis of clinical records of 19 keratoconus eyes and eight PMD eyes. Keratometric mean curvature maps were computed from a placido-disk-based corneal topography system. The peak location and amplitude of distortions were quantified by fitting two-dimensional Gaussian functions. Computer simulations of keratoconic corneal topography were used to help interpret the results. RESULTS: Keratoconus and PMD eyes had a characteristic localized increase in convexity (cone) on mean curvature maps. Computer simulations showed that the peak on the mean curvature map accurately represented the peak of the cone-like distortion. However, the peak location and appearance of the same conic distortion on axial and tangential maps were greatly influenced by coexisting astigmatism. The Gaussian function provided an excellent model of keratoconus on mean curvature maps, with a mean cross-correlation of 0.80. According to Gaussian fitting, the vertical cone peak locations were -1.10 +/- 0.43 mm (mean +/- SD) in keratoconus eyes and -1.94 +/- 0.53 mm in PMD eyes (P < .01). The locations of peaks on axial and tangential maps differed considerably from those on mean curvature maps. Advanced keratoconus tended to have higher cones (amplitude 13.31 +/- 6.87 diopters) than early keratoconus (amplitude 10.65 +/- 1.56 diopters). CONCLUSIONS: Gaussian fitting of mean curvature maps accurately quantifies the peak location and amplitude of the cone in keratoconus and PMD eyes. This new topographic analysis might be useful in the diagnosis and tracking of corneal ectatic diseases.     

Spontaneous corneal hydrops and perforation in keratoconus and pellucid marginal degeneration

PURPOSE: To report two cases of pellucid marginal degeneration and one case of keratoconus associated with spontaneous corneal hydrops leading either to perforation or imminent perforation, requiring urgent keratoplasty. METHOD: Retrospective interventional case series of three patients with noninflammatory peripheral corneal degenerations. A retrospective review was done of the clinical courses, surgical interventions, and pathologic specimens, development of spontaneous hydrops, perforation, need for surgical intervention, and final visual outcome. RESULTS: Two patients with pellucid marginal degeneration and one with keratoconus developed spontaneous hydrops followed by aqueous leakage through markedly thinned anterior stroma. In one case, the leak site was successfully sealed after three separate applications of tissue adhesive, although the remaining two cases required penetrating keratoplasty. CONCLUSIONS: These cases document the very unusual occurrence of corneal hydrops leading to spontaneous corneal perforation in patients with keratoconus and pellucid marginal degeneration.     

Progression of pellucid marginal degeneration and higher-order wavefront aberration of the cornea

PURPOSE: To report the time course of changes in corneal wavefront aberrations in a patient with pellucid marginal degeneration. CASE: A 59-year-old man with pellucid marginal degeneration was followed-up annually with slit-lamp microscopy and videokeratography for 11 years. The anterior corneal height data of the videokeratography were expanded into the set of orthogonal Zernike polynomials to calculate wavefront aberrations for the central 3-mm cornea. OBSERVATIONS: Although the patient complained of gradual deterioration of vision, there was no evident sign of disease progression on slit-lamp examination and visual acuity measurement. Color-coded maps of videokeratography showed slight deterioration over time, but no remarkable and decisive changes were seen. Coma-like aberration displayed a gradual, but apparent increase with a 1.67-fold worsening (0.473 microm to 0.792) during the 11-year follow-up period. Spherical-like aberration remained almost stable throughout the observation period. There were no obvious changes in crystalline lens and retina. CONCLUSIONS: The results suggest that increases in coma-like aberrations of the cornea reflect the subclinical progression of pellucid marginal degeneration over the years.     

Management of pellucid marginal corneal degeneration

PURPOSE: This study was designed to determine how patients with pellucid marginal corneal degeneration (PMCD) are managed in a tertiary corneal practice. METHODS: A retrospective chart review of 45 patients with PMCD from a corneal referral practice was performed. Information collected from the medical records included demographic data, best-corrected visual acuity, videokeratography, contact lens use, and surgical procedures. RESULTS: Forty-five patients (85 eyes; 30 males, 15 females) with PMCD were included in this study. They were followed-up for an average of 4.7 years (standard deviation (SD), +/-8.7). Seventy-five eyes (88.2%) were managed nonsurgically with spectacles in 31 eyes (36.4%) or contact lenses in 44 eyes (51.8%). Contact lens management was initially attempted in 51 eyes (60%); however, 7 eyes failed contact lenses. Visual acuity of 0.5 (20/40) or better was noted in 34 eyes (75.5%) after contact lens fit. Ten eyes (11.8%) underwent penetrating keratoplasty with an average postoperative follow-up of 9 years (SD, +/-8.2; 1.5-20.5). Clear grafts were present in all 10 eyes at the end of the study (average, 9 years; SD, +/-82). CONCLUSIONS: Nonsurgical management of PMCD continues to play a predominant role in the management of this disorder. Poor best-corrected visual acuity at presentation of 0.2 (20/100) or worse and long follow-up (8 years or more) were significantly associated with surgery.     

Quantitative assessment of topographical parameters to differentiate keratoconus from pellucid marginal corneal degeneration and

INTRODUCTION: The purpose is to compare videokeratometric data (Fourier series harmonic analysis and wave-front analysis) in eyes with ectatic corneal disease (keratoconus; pellucid marginal corneal degeneration [PMCD]) and to determine parameters for early diagnosis and distinction of keratoconus and PMCD. PATIENTS AND METHODS: 13 eyes with PMCD, 32 eyes with keratoconus and 18 healthy eyes were included. Computerized videokeratographic methods were assessed, using Fourier series harmonic analysis, Zernike coefficients and eccentricity. RESULTS: Irregular astigmatism (Fourier series harmonic analysis: decentration and/or irregularity) and the aberration coefficient were out of the normal range in all pathologic eyes. Both the nasal and the temporal eccentricities were greater than 0.63 in all PMCD patients, whereas either the superior or the inferior eccentricity was negative in all patients. In keraotoconic eyes, all quadrant eccentricities were positive and greater than 0.4. CONCLUSIONS: Irregular astigmatism and the aberration coefficient are useful parameters in detecting ectatic corneal disease using a computerized videokeratoscope. The calculation of the spherical equivalent (Fourier series harmonic analysis: no decrease of spherical equivalent in PMCD subjects) and of quadrant eccentricities are useful tools in distinguishing PMCD and keratoconus.     

Corneal topography of pellucid marginal degeneration

Our computer-based corneal topography analysis system was used to study the keratoscope photographs (keratograms) from two patients with classic pellucid marginal degeneration and a third patient with no inferior corneal thinning, whose keratoscope mire pattern was suggestive of the condition. All three patients showed marked flattening of the central cornea along a vertical axis and marked steepening of the inferior corneal periphery, which also extended into mid-peripheral inferior oblique corneal meridians. The mid-peripheral cornea gradually decreased in power above the inferior oblique meridians.     

Surgical treatment of advanced pellucid marginal degeneration

PURPOSE: To determine the efficacy of simultaneous peripheral crescentic lamellar keratoplasty (LK) and central penetrating keratoplasty (PK) for advanced pellucid marginal degeneration (PMD). DESIGN: Retrospective, noncomparative, interventional case series. PARTICIPANTS: Five patients with advanced PMD. METHOD: Simultaneous peripheral crescentic LK and central PK followed by selective suture removal and astigmatic keratotomy in the postoperative period. MAIN OUTCOME MEASURES: These included interval of time required for visual rehabilitation, best spectacle-corrected visual acuity achieved, and amount of corneal astigmatism, as measured by videokeratography. Measuring the change in corneal astigmatism by videokeratography over the subsequent follow-up period after spectacle correction had been prescribed assessed stability of the achieved refraction. RESULTS: Visual acuity results were 20/40 in three eyes, 20/80 in one eye, and 20/400 in one eye. The latter two had decreased acuity from posterior subcapsular cataract formation, which may have been caused by topical steroid use. The time required for visual rehabilitation ranged from 5.13 to 10.93 (mean, 9.92) months, and the amount of corneal astigmatism at the end of this period ranged from 0.3 diopters (D) to 5.3 D. A tendency for an increase in "with the rule astigmatism" after the rehabilitation period was noted. Two patients had elevations of intraocular pressure that responded to reduction in topical steroid dose. CONCLUSIONS: The short-term results with this technique are excellent in that it provides early and stable visual rehabilitation in patients with advanced PMD. Low to moderate levels of postkeratoplasty astigmatism were achieved in all the eyes treated. The usual tendency of an increase in "against the rule astigmatism" that occurs when PK alone is done for PMD was eliminated.