Krukenberg’s spindle is the name given to the pattern formed on the inner surface of the cornea by pigmented iris cells that are shed during the mechanical rubbing of posterior pigment layer of the iris with the zonular fibrils that are deposited as a result of the currents of the aqueous humor. The sign was described in 1899 by Friedrich Ernst Krukenberg (1871-1946), who was a German pathologist specialising in ophthalmology. It runs the course of being mild to a condition known as pigmentary glaucoma where the loose pigment in the eye can plug up the drainage system leading to high intra-ocular pressure and optic nerve damage.
Risk Factors
- Male gender. Pigmentary glaucoma has a strong male predominance, with all case series showing a male to female ratio of between 2:1 and 5:1.
- Male patients with Pigmentary Glaucoma (PG) and Pigment Dispersion Syndrome (PDS) most often present in their 30s, whereas female patients typically present roughly a decade later in life. Cases of PDS have been identified in patients as young as 12-15 years of age. Disease may be more frequent in middle age when the lens has enlarged and the iris is flexible enough to form a concave position.
- The most common refractive error noted in eyes with PDS and PG is moderate myopia, with mean spherical equivalents typically in the range of -3 to -4 D. A broad range of refractive errors is typically found, though hyperopia is relatively rare, usually accounting for only 5-10% of patients in most case series.
- Both pigment dispersion syndrome and PG occur infrequently (<5% of patients identified in case series) in persons of African ancestry. However, the actual prevalence may be higher than reported as persons of African ancestry have thick brown irides making detection of iris transillumination defects more difficult.
- Concave iris and posterior iris insertion. Patients with PDS and PG have greater iris-lens contact than individuals without the disease. Increased iris-lens contact results from a combination of a concave iris and a more posterior iris insertion, both of which are more common in patients with PDS or PG.
- Flat corneas. Patients with PDS and PG have significantly flatter corneas than control subjects of similar age and refractive error. A flat cornea might be more likely to result in burping of aqueous humor from the posterior chamber to the anterior chamber with blinking, resulting in increased iridozonular contact.
- Family history. Direct examination of a small set of family members of PDS patients showed that disease was present in 2/19 (12%). A second examination of family members reported signs of PDS in 36% of subjects’ parents and 50% of siblings, but no children, suggesting a possible autosomal dominant inheritance pattern with incomplete penetrance. Families with PG have also been described across multiple generations. Roughly 50% of family members in the described families had PDS or PG, reinforcing the idea of an autosomal dominant inheritance pattern.