Schnyder Crystalline Dystrophy Research Articles

Corneal opacities in children

The corneal opacities in childhood could be either, congenital or acquired. The congenital could either localized/non‐systemic disease, like the congenital hereditary endothelial dystrophy, posterior polymorphous corneal dystrophy, congenital hereditary stromal dystrophy, peters anomaly, congenital anterior staphyloma, sclerocornea, cornea plana, cornea tumours, epibulbar dermoid, or related to systemic/metabolic Disorders like mucopolysaccharidoses, cystinosis, tyrosinemia, schnyder crystalline dystrophy, fetal alcohol syndrome. The acquired corneal opacities could be either traumatic, like traumatic breaks in descemet membrane, corneal blood staining, corneal keloids, or non traumatic like keratoconus, posterior corneal depression, keratoglobus, congenital or infantile glaucoma, Corneal ulcers, Familial dysautonomia (Riley‐Day syndrome), Stevens‐Johnson syndrome and toxic epidermal necrolysis. We will discuss these cases, their clinical picture, work up and management.

Recurrence of corneal dystrophies after penetrating keratoplasty

The authors conducted a retrospective study to assess the rates of simple and clinically significant recurrent corneal dystrophy in eyes undergoing penetrating keratoplasty over a 17-year period for this indication. Simple recurrence was defined as any biomicroscopic findings in the graft button. Clinically significant recurrence was defined by either the presence of recurrent corneal epithelial erosions or decreased visual acuity. The study consisted of 17 eyes (10 patients) with dystrophy of the Bowman layer, 35 eyes (21 patients) with lattice dystrophy, 14 eyes (8 patients) with macular dystrophy, 7 eyes (5 patients) with granular dystrophy, and 4 eyes (4 patients) with Schnyder crystalline dystrophy. Simple and clinically significant recurrences were seen with all dystrophies. The highest rates of simple recurrence were seen with Bowman corneal dystrophy (88%) and lattice corneal dystrophy (60%). The median time to simple recurrence was 2.0 years for Bowman corneal dystrophy and 8.4 years for lattice dystrophy. The highest rates of clinically significant recurrence were seen with lattice corneal dystrophy (17.1%, first eye; 20% second eye) and Bowman corneal dystrophy (11.8%, first eye; 17.6% second eye), whereas the lowest rates were with macular and Schnyder crystalline dystrophy.—Michael D. Wagoner

Recurrence of corneal stromal dystrophies after penetrating keratoplasty.

To assess the rates of simple and clinically significant recurrences of stromal dystrophies in corneal grafts. We conducted a retrospective review of Wills Eye Hospital records from 1984 to 2001, identifying all patients with stromal corneal dystrophies who had penetrating keratoplasties. Kaplan-Meier curves and chi analysis were performed. The study population consisted of 35 eyes (21 patients) with lattice dystrophy, 17 eyes (10 patients) with corneal dystrophy of Bowman's membrane (CDB), 14 eyes (eight patients) with macular dystrophy, seven eyes (five patients) with granular dystrophy, and four eyes (four patients) diagnosed with Schnyder's crystalline dystrophy. There was a simple recurrence in 21 (60%) eyes (14 patients) with lattice and in 15 (88%) eyes (eight patients) with CDB. The median time to simple recurrence for the first eye transplanted of each patient was 8.4 years for lattice and 2.0 years for CDB. After 5 years of follow-up, there was a clinically significant recurrence, manifested by recurrent erosions or associated with decreased visual acuity, in the first eye transplanted of each patient, respectively, in six (17.1%) and seven (20%) eyes with lattice and in two (11.8%) and three (17.6%) eyes with CDB. Corneal dystrophy of Bowman's membrane has the highest rate of simple recurrence followed by granular and lattice dystrophies, respectively. However, the rate of clinically significant recurrence, both recurrent erosions and decreased visual acuity, in the first 5 years is similar in CDB and lattice dystrophies. Recurrence is infrequent in macular and Schnyder's crystalline dystrophy. As expected, in genetic diseases, the potential for recurrence exists and increases with follow-up time.

Recurrence of corneal dystrophy after excimer laser phototherapeutic keratectomy

Background Excimer laser phototherapeutic keratectomy (PTK) can be useful to treat anterior corneal dystrophies both before and after penetrating keratoplasty. Objective To evaluate the recurrence of corneal dystrophies after excimer laser PTK. Design Retrospective case series. Participants Fifty excimer laser PTK procedures were performed in 43 eyes of 33 patients with corneal dystrophies. Preoperative diagnoses included Reis-Bücklers dystrophy (13 eyes), granular dystrophy (11 eyes), anterior basement membrane (ABM) dystrophy (11 eyes), lattice dystrophy (7 eyes), and Schnyder crystalline dystrophy (1 eye). Intervention Two excimer lasers (VISX 20/20 model B and VISX Star) were used to perform all PTKs. Main outcome measures After PTK, patients were followed on a regular basis with measurement of best-corrected visual acuity and biomicroscopic examination. Evidence of recurrent dystrophy was noted according to specific criteria. Results Follow-up range was from 1.1 to 71.2 months (mean, 19.5 months). Clinically significant recurrent dystrophy occurred in 17 eyes. The ABM dystrophy recurred in the form of recurrent corneal erosions in 5 (42%) of the 12 eyes within 6 to 9 months of PTK. Four of these five eyes had mild erosions, which were treated successfully with topical medications while one eye required an additional PTK for an erosion outside the initial treatment area. Eight (47%) of 17 eyes with Reis-Bücklers dystrophy developed clinically significant recurrence an average of 21.6 months after PTK. Three (23%) of 13 eyes with granular dystrophy were found to have a significant recurrence a mean of 40.3 months after PTK. Only one (14%) of seven eyes with lattice dystrophy developed a significant recurrence at 6 months after PTK. Six eyes with significant recurrence after PTK were retreated successfully with additional PTK. Three eyes later developed recurrence of granular and Reis-Bücklers dystrophy after the second PTK. The probability of recurrence of these dystrophies after PTK was calculated using the Kaplan-Meier survival analysis. Conclusion Phototherapeutic keratectomy can restore and preserve useful visual function for a significant period of time in patients with anterior corneal dystrophies. Even though corneal dystrophies are likely to recur eventually after PTK, successful retreatment with PTK is possible.

Schnyder Crystalline Dystrophy Sine Crystals: Recommendation for a Revision of Nomenclature

To determine the percentage of patients with Schnyder crystal line dystrophy who had corneal crystal deposition. Thirty-three patients with Schnyder crystalline dystrophy were identified by the author since 1987. Each patient had a complete ophthalmic evaluation, including slit-lamp examination by the author. Only 51% (17 of 33) of patients with Schnyder crystalline corneal dystrophy actually had clinical evidence of corneal crystalline deposits. Because of the confusing nomenclature, many ophthalmologists presume that the presence of corneal crystals is an integral part of the diagnosis of Schnyder crystalline dystrophy. The clinician should be aware that despite the fact that the noncrystalline form of the dystrophy has been poorly recognized, it is equally common.

Clinical and Histopathologic Features of Corneal Dystrophies in Japan

To examine retrospectively the frequency of various corneal dystrophies among Japanese patients who underwent keratoplasty or keratectomy at the authors' institution over a 34-year period, and to compare the histopathologic features of these disorders in the Japanese population with those reported in the Western literature. Corneal specimens obtained during keratectomy or keratoplasty (lamellar and penetrating) performed at the authors' institution from 1959 through 1992 were reviewed. Immunohistochemical studies were performed using monoclonal antibodies to keratan sulfate and gelsolin, as well as two lectins (concanavalin A and wheat germ agglutinin). Of 1259 corneal specimens, 159 (12.6%) specimens from a total of 80 patients showed corneal dystrophy. Virtually all were non-Fuchs dystrophies; only one case of primary Fuchs dystrophy was identified histologically. Granular dystrophy and gelatinous drop-like dystrophy were the most common dystrophies identified in the specimens, largely because of multiple specimens from individual patients with recurrent disease. These two disorders accounted for 86 of the 159 specimens. In terms of numbers of patients, lattice dystrophy was the most common (26 patients, 32.5%), followed by macular dystrophy (16 patients, 20%), gelatinous drop-like dystrophy (15 patients, 18.8%), granular dystrophy (14 patients, 17.5%), and Avellino dystrophy (3 patients, 3.75%). Dystrophies represented by only one or two patients included congenital hereditary endothelial dystrophy, primary spheroidal keratopathy, posterior polymorphous dystrophy, Schnyder crystalline dystrophy, and Fuchs dystrophy. This histopathologic study showed a very low incidence of Fuchs dystrophy in the authors' Japanese patient population, compared with the incidences seen in studies of populations in Western countries. Of the non-Fuchs dystrophies, lattice dystrophy was the most common among the patients, although there were large numbers of specimens with granular dystrophy and gelatinous drop-like dystrophy due to their recurrent character. The causes of clinical and histopathologic differences and similarities among the Japanese patients and the patients described in the Western literature are likely related to genetic factors, but a complete understanding of their specific mechanisms awaits future molecular biologic and genetic elucidation.

Progressive Schnyder's Corneal Dystrophy

Schnyder's crystalline dystrophy is a central anterior bilateral corneal dystrophy characterized by the deposition of crystals composed of cholesterol and other lipids. This condition classically is described as nonprogressive after childhood, but a series of recent studies following patients over time has challenged this teaching. The authors present a family pedigree including a patient first reported in 1954 and followed for 25 years with dramatic progression of the corneal condition in a dense, discoid pattern of crystals. Best-corrected visual acuity decreased from 20/30 to 20/80 in both eyes. This patient now has three children, all with typical corneal involvement. Ocular pathologic examination performed on corneal biopsies submitted for light and electron microscopy demonstrated cholesterol deposition consistent with a diagnosis of Schnyder's. Schnyder's corneal dystrophy may progress significantly over time. The characterization of this condition as stationary may need to be reconsidered.

Schnyder's dystrophy of the cornea. A Swede-Finn connection.

Schnyder's crystalline dystrophy is an uncommon hereditary disease in which there is abnormal deposition of cholesterol and/or lipid usually in the anterior stroma of the central and peripheral cornea. Four families with Schnyder's dystrophy have been identified in central Massachusetts. Of the 173 living members of these pedigrees, 60 patients were examined by the author. Eighteen patients had Schnyder's dystrophy. Affected individuals less than 23 years of age had bilateral, central disc-like corneal opacification. Those greater than 23 years of age also demonstrated prominent arcus lipoides. By age 40, all affected individuals developed a diffuse stromal haze. Only 50% of affected individuals had corneal crystalline deposits. Abnormal cholesterol deposition affected the entire stromal thickness in the majority of patients. Although the four families said that they were not related to each other, all had ancestry from towns within a 100-k area on the southwest coast of Finland. Patients in this area of Finland were examined by the author and demonstrated signs of Schnyder's dystrophy. This may represent the largest cohort of Schynder's dystrophy described to date.

Effects of cholestanol feeding on corneal dystrophy in mice

A cholestanol-enriched diet administered for 8 months to BALB/c mice produced in 20% two kinds of corneal opacities resembling calcific band keratopathy and Schnyder's crystalline dystrophy in humans. The concentrations of cholestanol in serum, liver and cornea of the corneal opacity bearing mice were 30-40-times higher than those of normal mice. On the other hand, brain cholestanol level increased only 7-times in the opacity group as compared with that of control group. There was no significant difference in the cholesterol concentrations of serum and several tissues among opacity, non-opacity and the control group. The crystal particles were observed between epithelial basement membrane and superficial stroma by the electron microscopy. Energy dispersive analysis of the particles revealed that the deposits were composed principally of calcium and phosphorus with other crystalline materials, which was presumed to be cholestanol. These results suggest that the cholestanol may deposit in the cornea from elevated serum levels. Deposition of cholestanol in cornea and related area may be a cause of corneal dystrophy in CTX.

Stoffwechselstörungen und Hornhautveränderungen

The following inborn errors of metabolism may show corneal changes: A. Inborn errors of metabolism affecting the corneal epithelium: (1) familial dysautonomia, (2) tyrosinaemia type II, (3) Fabry's glycolipidosis. B. Inborn errors of metabolism affecting the corneal stroma: I. Localized amyloidosis (lattice dystrophy of the cornea), II. Defects in carbohydrate metabolism: (1) localized mucopolysaccharidosis (macular dystrophy of the cornea), (2) systemic mucopolysaccharides, (3) glycogen storage disease. III. Defects in lipid metabolism: (1) localized from (Schnyder's crystalline dystrophy), (2) systemic forms (hyperlipoproteinaemia, hypolipoproteinaemia, Lecithin-cholesterol acyl transferase deficiency, Wolman's disease, Gaucher's disease). IV. Combined defects in lipid and carbohydrate metabolism (mucolipidoses). V. Other inherited metabolic disorders: (1) aminoacidopathies (cystinosis, Wilson's disease, ochronosis, Chediak-Higashi syndrome), (2) hemochromatosis.