Soemmering Ring

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Article initiated by:

Nikolas Hopkins

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Grant C. Hilliard, Josiah Fahhoum, Sean Pak, Joseph.Fong, Nikolas Hopkins

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Disease Entity

Soemmering’s ring is a known form of after-cataract consisting of retained epithelial lens cells which have proliferated to form a ring of cortical fibers in the capsular periphery and around the implanted intraocular lens (IOL) A form of regenerative Posterior Capsule Opacification (PCO) similar to Elschnig Pearls, Soemmering’s ring typically remains fixated behind the iris by the Zonule of Zinn with practically no disturbance of vision Symptomatic presentation arises either from extensive development involving the central visual axis or when the ring suffers dislocation from its initial, held position behind the iris to thus occlude the visual path and disturb vision

History

Soemmering’s ring is a form of regenerative Posterior Capsule Opacification (PCO) discovered in 1928 by Detmar Wilhelm Soemmering, an ophthalmologist from Mainz, Germany.He was examining the eyes of cadavers who had cataracts surgically removed in life. Bisection of the eye through the equator revealed an after-cataract phenomenon in the shape of a ring in multiple cadaverous eyes. He defined this form of after cataract as a ring-like structure made of equatorial lens epithelial cells, deposited between the posterior capsule and anterior capsule remnant behind the iris.

The rarity in pathology involving Soemmering’s ring in the modern age is likely due to the recent advancements in cataract surgery and management, such as phacoemulsification techniques and posterior chamber-in-the-bag intraocular lens implantations.. Its presence in the literature, however, has grown since Soemmering’s original description, building upon the nature of the ring’s structure and developmental pathophysiology from animal and clinical studies.

Pathophysiology

Soemmering’s Ring develops either as the result of cataract extraction or injury to the lens. With cataract extraction, techniques that tear or excise the central portion of the anterior capsule, such as Fukala’s procedure to treat myopia, can take away its tension and cause the anterior capsule to collapse, forming a ring. This structure adheres to the posterior capsule and becomes an enclosure where epithelial cells, hyaline material, other lens materials, and growth factors can proliferate.Of note, it is theorized that the proliferation of the lens epithelium is a protective measure of the anterior capsule to counter the lytic properties of the aqueous humor. Furthermore, an early-age eye procedure or injury to the lens is a significant risk factor for development of a Soemmering’s Ring due to its proliferative processes having an abundance of growth factors present and decades longer to develop.

Its fixed position posterior to the iris by the Zonule of Zinn, an assortment of extracellular fibers emanating from the ciliary bodies to stabilize the lens, allows for Soemmering’s ring to quietly grow over time, as it is difficult to detect during physical examination due to its transparent, central portion. While this held state does allow for the ring to remain largely asymptomatic, in the event of dislocation or degeneration, this form of PCO can bear serious complications.

Dislocation of Soemmering’s ring in the pupillary zone will result in shrouding of the fundus, producing vision loss. Secondary glaucoma may also occur; as when the structure gradually proliferates in size, reduction of the synechial angle can hinder outflow of the aqueous humor and thus raise the intraocular pressure (IOP). Unmanaged elevated IOP will eventually cause damage to the optic nerve and gradual vision loss. Fragmentation of the lens once dislocated may also be inflammatory and injurious upon corneal contact, presenting as a form of persistent corneal decompensation.²¹

Apart from dislocation, a Soemmering’s Ring may even calcify over time and disintegrate, causing calcified deposits to adhere to the corneal endothelium, retina, and other structures.^3,22 These deposits can result in asteroid hyalosis, corneal edema, and Uveitis-Glaucoma-Hyphema (UGH) syndrome.

Due to its structural nature, involvement or dislocation of Soemmering’s ring should be considered in cases significant in pediatric ocular history, such as severe adolescent myopia or lensectomy, or previous cataract procedures performed with outdated techniques.

Characterization

Soemmering’s ring was originally defined as a ring-like lenticular material posterior to the iris, where the proliferative activity of remaining equatorial lens epithelial cells produces circumferential, cortical fibers that form a ring along the periphery of the capsular bag and remain fixated by the Zonule of Zinn. Histopathologic characterization of Soemmering’s ring validates that the epithelial cells on the posterior capsule and the outside of Soemmering’s ring are both of lenticular origin and continuous with subcapsular epithelial cells, which traverse its fusion site into the ring’s fibers. Soemmering’s rings also express areas of varying transparency, with transparent areas commonly found in the center of the ring and opaque ones more frequently along its peripheral edges; interestingly, the process of central transparency is suggested to be independent of its peripheral opacification.⁴

Electron microscopy studies have demonstrated Soemmering’s rings to be composed of clear lens fibers and densely packed lens fiber proteins. These fibers centrally degenerate inward and are often oriented in parallel with distinct individual borders, with some also presenting compactly and granular in texture. Clear clusters of recrystallized lens-proteins have been visualized along the ring’s fibers to be surrounded by amorphous lens-fiber material. In the fracture faces of these lens fibers, finger-like crystals have been found in the inner parts of Soemmering’s ring. Like the recrystallized areas of initial cataracts, these crystals suggest for Soemmering’s ring to possess an inherent cataractous nature or for degenerative processes in the lens-fiber material to occur during ring formation that may be mechanistically similar to the changes of the lens during cataract development.^11,12

Soemmering’s rings also consist of remnants of the anterior and posterior lens capsule that enclose the equatorial part of the lens fibers.¹³ This residual equatorial cortical material may contain proliferations of vacuolated, disorganized lens epithelial cells in various degenerative stages, such as swollen cells in variable proportions (i.e. Wedl/Bladder cells, Elschnig pearls) or fibrous metaplasia of the lens epithelium.

Physical examination

Soemmering's ring, like other PCO complications, can be diagnosed via slit-lamp microscopy. It is usually diagnosed clinically after it has dislocated, following the creation of an iris coloboma, or when the pupil has been extensively dilated.

Clinical presentations involving Soemmering’s ring are quite rare. However, its dislocation being responsible for vision disturbance should be considered in a patient history significant for cataract surgery or myopic management, especially during adolescence.

FACTORS FOR DISLOCATION

Early Ring Formation:

An early history of ocular trauma leading to Soemmering’s ring development is a significant factor for eventual ring dislocation. Adolescent cell elements in general possess a higher capability of proliferation alongside an abundance of available growth factors, which only enhances ring development by the proliferative activity of equatorial lens epithelial cells. Its birth during a patient’s younger years also leaves substantial time for the ring to grow in mass and weight, further favoring its dislocation from its position behind the iris plane.

Myopia:

Typical structural changes in the myopic eye, such as degeneration of the zonules, atrophy of the ciliary body, and liquefaction of the vitreous, small ciliary muscles, and deep anterior chamber, all significantly contribute to promote the planar dislocation of Soemmering’s ring, even in the context of minimal trauma. Particularly, vitreous liquefaction and anterior chamber deepening favor anterior or posterior dislocation of the ring. Structural degeneration of such ocular components increases the susceptibility of Soemmering’s ring to dislocate in the eye, particularly if it has had time to undergo extensive development.

Ring Degeneration:

Calcific, morgagnian, and fatty degenerations may also occur within the ring itself, visualized by its notable white, crystalline opacity. Such degenerative changes may alter the ring’s structural consistency or density, contributing to the risk of its dislocation.

Trauma:

Both significant and minor trauma may induce Soemmering’s ring dislocation. Injury to the head, direct or indirect shaking of the eyeball, and even falls may produce ring dislocation.

Spontaneous Dislocation:

In rare cases, spontaneous dislocation may also be responsible for ring dislocation.

Management and General treatment

Timely recognition of this condition can help prevent ocular complications such as corneal edema and glaucoma. Patients can undergo Nd:YAG laser capsulotomy which is the most common modality used for treating fibrous and pearl form of PCO. Surgical dissection may also be considered in extensive cases, as demonstrated in resolution of UGH syndrome attributed to dislocation of Soemmering’s ring. Calcium deposits from Soemmering’s ring may require aspiration/removal of calcific lens fragments, removal of the entire capsular bag/PCIOL complex.