Schnyder corneal dystrophy

The present review of Schnyder corneal dystrophy (SCD) corrects the misconceptions in the published literature about this disease. Understanding the clinical findings facilitates diagnosis of the dystrophy.

Retrospective case series of 115 affected individuals from 34 SCD families identified since 1989 reports the clinical findings in a large cohort and the long-term visual morbidity of SCD. The configuration of the progressive corneal clouding is predictable on the basis of age and, contrary to many older publications, only 54% of affected patients were found to have corneal crystals. Penetrating keratoplasty was reported in 20 of 37 (54%) patients of at least 50 years and 10 of 13 (77%) patients of at least 70 years. Best corrected visual acuity 1 year prior to penetrating keratoplasty in 15 eyes (nine patients) ranged from 20/25 to 20/400 including seven eyes with other ocular disorders. Best corrected visual acuity in the remaining eight eyes was 20/25 to 20/70. These patients often complained of glare preoperatively, which most likely resulted from light scattering from the corneal cholesterol.

The literature on SCD must be changed to reflect new information about the disease. When present, corneal crystals facilitate disease diagnosis but the examiner must be aware that they are only present 54% of the time. Although scotopic vision remains good until old age, disproportionate loss of photopic vision with frequent complaints of glare necessitates penetrating keratoplasty in the majority of patients over 50 years of age.