Vossius Ring is a circular deposit of pigment resulted from blunt trauma that forms a complete or incomplete ring on the anterior lens capsule surface.
Vossius ring is a well-circumscribed complete or incomplete ring of pigment deposition on the anterior lens capsule surface, usually as a result of significant blunt eye trauma. The disease was first described by Vossius in 1903, at which time he discussed both a pigmented variety of the ring and a non-pigmented variety that he thought was the result of degeneration of anterior lens epithelial cells.  The non-pigmented form is no longer considered to be a Vossius ring.
A Vossius ring is a result of compression of the pigmented posterior iris epithelial cells and/or pupillary ruff against the anterior lens capsule with abrupt blunt force to the eye. Rupture of the cells causes deposition of a circular line of melanin pigment on the lens capsule. The ring of pigment is generally the same diameter as the undilated pupil. Interestingly, when evaluating a series of injured combat soldiers who sustained injury at various times of day and night, Gunderson noted in 1945 that the rings were of fairly uniform in size despite variable pupil size at the time of injury. Although his measurement system was relatively crude (a transparent ruler held close to the cornea while looking through a direct ophthalmoscope with +8.00 sphere), the rings in all of his patients were a consistent 2.25 to 2.75 mm in diameter. 
The major risk factor for Vossius ring formation is sudden, blunt trauma to the eye.
Deposition of melanin and cellular debris, from ruptured iris epithelial cells in a concentric ring on the anterior lens capsule. 
Compression of pigmented iris epithelium and/or pupillary ruff cells during blunt compression of the eye results in cellular rupture with deposition of cellular contents and melanin pigment onto the lens capsule surface.
Diagnosis is made at the slit lamp by observing a complete or incomplete ring of pigment on the anterior lens capsule. The ring is seen most easily with a dilated pupil.
A history of blunt eye trauma is critical to making this diagnosis. The shortest interval between injury and appearance of a Vossius ring was two hours, but typically it is not observed until four or more days post injury 
Previously, there was some debate as to the origin of the pigment. Some authors believed that the pigment was a result of hemoglobin deposition on the lens surface as hyphema and vitreous hemorrhage were frequently associated with the condition. These theories are no longer widely accepted as Vossius rings are known to form without hemorrhage, and a Vossius ring does not form after an atraumatic vitreous hemorrhage.
A thin, circular line of pigment on the lens capsule is observed. The circle may be incomplete depending on the vector of the blunt trauma.
A Vossius ring is asymptomatic and generally will improve or resolve with time. 
The diagnosis is made by clinical examination only.
Dilation can assist in making the diagnosis. Generally, no other procedures are necessary.
No laboratory tests are typically indicated in the evaluation of a Vossius ring.
Anterior lens capsule pigment deposition can be observed in other conditions without a history of trauma and can mimic the appearance of a Vossius ring. Pseudoexfoliation syndrome (PXS) is characterized by a defect in the LOXL-1 gene at locus 15q22, which results in deposition of fibrillar, exfoliative material on the pupillary margin, lens capsule and zonules. The fibrillar material can be differentiated from Vossius ring by absence of trauma by history as well as lack of pigmentation. Additionally, pigment dispersion syndrome (PDS) is characterized by release of pigment granules by the iris pigment epithelium. The granules distribute throughout the anterior segment including the lens surface where they can form a ring of posterior pigment peripherally known as a Scheie stripe or line. Location of the line, iris transillumination defects and increased pigment on other anterior segment structures differentiates PDS from Vossius ring. 
Uveitis is another well-known cause of pigment deposition on the lens surface. Intraocular inflammation can result in formation of posterior synechiae. With resolution of inflammation or pharmacologic mydriasis, the synechiae can leave patchy clumps and fragments of pigment on the anterior lens capsule. Uveitis can be distinguished from Vossius ring based on history and presence of other ocular signs of inflammation including cell and flare in the anterior chamber, hypopyon, keratic precipitates, presence of systemic inflammatory disease, etc. 
No medical or surgical treatment is necessary for a Vossius ring, which is usually of little clinical significance but can be an important diagnostic tool if history of blunt trauma is in question. 
An isolated Vossius ring, without other signs of eye injury, has an excellent prognosis with normal long-term visual acuity.
- Lens and Cataract, Section 11. Basic and Clinical Science Course. San Francisco: American Academy of Ophthalmology; 2014.
- Gundersen, T. (1945). Observations on the Vossius Ring. Transactions of the American Ophthalmological Society, 43, 149-162.
- Ophthalmic Pathology and Intraocular Tumors, Section 4. Basic and Clinical Science Course. San Francisco: American Academy of Ophthalmology; 2014.
- Kanski, J. J., & Bowling, B. (2011). Clinical Ophthalmology: A Systematic Approach : A Systematic Approach (7th Edition): Elsevier Health Sciences.
- Gipner, J. F. (1929). Clinical and Experimental Studies on Traumatic Annular Opacity of the Anterior Lens Surface (Vossius' Ring). Transactions of the American Ophthalmological Society, 27, 296-313.