Krukenberg Spindle in Pigment Dispersion Syndrome and Pigmentary Glaucoma

The fine vertical brown line on the posterior surface of this cornea is referred to as “Krukenberg spindle” and results from pigment staining of the corneal endothelium secondary to excessive liberation of pigment from the posterior surface of the iris.¹ Krukenberg spindle occurs in the spectrum of anterior segment conditions that includes pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG).¹ The deposition of pigment is not limited to the corneal endothelium and often extends throughout the anterior segment.¹ The classic presentation includes dense pigmentation of the trabecular meshwork, midperipheral iris transillumination defects, and vertically oriented pigment deposition on central corneal endothelium.²

An underlying pathophysiology in both presentations is a genetically inherited anomaly resulting in a concave posterior iris configuration. This may, and often does, lead to rubbing of the posterior iris leaf against lens zonules, ultimately releasing pigment into the anterior chamber.² Histologic evaluation of tissues reveals that pigment granules are actually phagocytosed by trabecular meshwork cells.³

In cases in which accumulation of pigment in the trabecular meshwork does not reduce outflow enough to elevate intraocular pressure (IOP) to the point of causing optic nerve changes and visual field loss, the condition is known as PDS.¹ If pigment accumulates to an extent that it ultimately leads to IOP elevation, optic nerve changes, and field loss, the diagnosis is PG.¹

In a post-mortem study of two patients who had PDS but not glaucoma, Kampik et al used light microscopy, scanning electron microscopy, and transmission electron microscopy to evaluate intraocular structures.⁴ They found disruption of the iris pigment epithelium and loss of pigment granules in areas of the posterior leaf corresponding to transillumination defects.⁴ They also reported that in the trabecular meshwork, pigment was free (i.e., not within any tissue), inside macrophages, and inside endothelial cells.⁴

Kuchle et al used a laser flare-cell meter to count aqueous melanin granules in 21 individuals who had PDS and in a control group of 21 individuals who did not have PDS. They found an abundance of melanin granules in the aqueous of eyes subjects who had PDS but not in controls. They noted that medical dilation of pupils led to increased numbers of aqueous melanin granules in PDS subjects but not in controls. Finally, they found that exercise did not significantly alter the density melanin granules of study subjects or controls.⁵

The discovery of Krukenberg spindle in patients should alert practitioners to the potential for PDS or PG and the need to educate, evaluate, and monitor for signs and symptoms consistent with a diagnosis of ocular hypertension or glaucoma. It is also worthwhile to evaluate their IOP before and after medical dilation to determine whether there is an increase in IOP.

1. Ramulu PY, Aref AA, Akkara JD, et al. Pigmentary glaucoma and Pigment Dispersion Syndrome. EyeWiki. 2019. Available at https://eyewiki.aao.org/Pigmentary_glaucoma_and_Pigment_Dispersion_Syndrome . Accessed Feb. 6, 2020.
2. Lahola-Chomiak AA, Walter MA. Molecular Genetics of Pigment Dispersion Syndrome and Pigmentary Glaucoma: New Insights into Mechanisms. J Ophthalmol. 2018 Mar 26;2018:5926906.
3. Campbell DG, Schertzer RM. Pathophysiology of pigment dispersion syndrome and pigmentary glaucoma. Curr Opin Ophthalmol. 1995 Apr;6:96-101.
4. Kampik A, Green RW, Quigley HA, Pierce LH. Scanning and Transmission Electron Microscopic Studies of Two Cases of Pigment Dispersion Syndrome. Am J Ophthalmol. 1981 May;91:573-587.
5. Küchle M, Mardin CY, Nguyen NX, Martus P, Naumann GO. Quantification of aqueous melanin granules in primary pigment dispersion syndrome. Am J Ophthalmol. 1998 Sep;126:425-431.