Senile scleral plaque (SSP) is a well-defined, slate-gray, elongated oval area of the sclera that appears posterior to the corneal limbus and anterior to the insertion of the horizontal rectus muscles. The characteristic gray color is due to the underlying uvea showing through the hyaline degeneration of the sclera.
It commonly occurs in elderly individuals aged 70 and older, with incidence increasing with age. The overall prevalence of calcified senile scleral plaques is 3–6.2%, but reaches 22.6% in those over 70. It is more common in women. Calcification is observed in less than half of cases.
Usually asymptomatic and clinically insignificant, but rarely, shedding (expulsion) of calcified plaques can cause senile scleral softening. About 11% of calcified lesions show beam hardening artifacts on CT scans and may be mistaken for intraocular foreign bodies 2).
QDoes senile scleral plaque require treatment?
A
It is usually an incidental asymptomatic finding and does not require treatment. However, rarely, shedding of calcified plaques can lead to senile scleral softening and formation of a scleral defect. If there is a high risk of spontaneous perforation, surgical treatment with scleral grafting may be necessary.
Gross findings: Observed as a well-defined, slate-gray, elongated oval area. It is a vertically elongated, angular oval with an average width of about 2 mm and height of about 5–6 mm.
Location: Located posterior to the corneal limbus and anterior to the insertion of the horizontal rectus muscles (medial and lateral rectus). It shows a distribution corresponding to the palpebral fissure.
Bilaterality: Usually bilateral, but rare unilateral cases have been reported2).
Calcification: Seen in less than half of cases, often occurring in the center of translucent lesions.
CT scan: Calcified senile scleral plaques appear as hyperdense areas. They can be identified by their characteristic location posterior to the corneal limbus and anterior to the rectus muscle insertions, but may be mistaken for intraocular foreign bodies in trauma cases2).
Anterior segment OCT (AS-OCT): Senile scleral plaques appear as hyporeflective structures, while calcified portions appear hyperreflective1). It is also useful for postoperative follow-up, visualizing the process of fissures in calcified plaques being closed by connective tissue1).
QCan it be mistaken for an intraocular foreign body on CT?
A
Yes. Calcified senile scleral plaques appear as hyperdense oval shadows on CT and may be misdiagnosed as intraocular foreign bodies2). Differentiation is particularly difficult in unilateral cases or those with trauma. They are distinguished by their characteristic location posterior to the corneal limbus and anterior to the rectus muscle insertions, and by the clinical feature of being asymptomatic.
The etiology of senile scleral plaques is unknown, but several mechanisms have been proposed.
Proposed Etiologies
Ischemia due to arteriosclerosis: Ischemia of the anterior sclera secondary to arteriosclerosis has been proposed.
Mechanical stress: Repeated mechanical stress and strain on the sclera from the horizontal rectus muscles may contribute to plaque formation. The location of plaques just anterior to the horizontal rectus muscles supports this hypothesis.
Ultraviolet damage: Accumulation of actinic damage from long-term exposure to solar radiation leads to structural degeneration. The distribution of plaques in the interpalpebral fissure supports this hypothesis.
Risk Factors
Aging: The most important risk factor. Prevalence increases sharply after age 70. It has been reported in 20% of individuals aged 80 and older2).
Female: It has been pointed out that it is more common in women.
Multifactorial: Multiple factors such as a combination of mechanical stress and ultraviolet damage may work together to form the spot.
Slit-lamp microscopy: A slate-gray, elongated oval area is observed posterior to the corneal limbus and anterior to the insertion of the horizontal rectus muscles.
Penlight examination: The presence of the spot can be confirmed even with simple observation.
Imaging Tests
CT scan: Useful for detecting calcified spots, but differentiation from intraocular foreign bodies is necessary2).
Anterior segment OCT: Enhanced depth OCT can depict low-reflectivity spots and high-reflectivity calcification1). It can also be used to monitor postoperative wound closure1).
Intraocular foreign body (IOFB): In trauma cases, high-density images on CT are similar. Differentiation is made by clinical findings (location, asymptomatic)2).
Optic disc drusen: Shows calcification on CT, but is differentiated by its location at the optic disc.
Choroidal osteoma: Similar calcification on CT, but located in the choroid.
Trochlear calcification: Differentiated by being localized to the superior medial trochlear area.
Rarely, calcified senile scleral plaques may separate and slough off, forming a scleral defect. This is called senile scleromalacia. Differentiation from perforating scleromalacia is important.
Calcified senile scleral plaques may increase resistance to scleral incision and complicate surgical treatment of other eye diseases. In a case of globe rupture traversing a calcified SSP, the calcified plaque was too hard for suture needles to pass through, requiring a special technique of long-bite suturing in the normal sclera outside the calcified SSP1).
In a case of globe rupture due to blunt trauma during farm work in a 94-year-old man, an 18-mm full-thickness scleral wound traversed a calcified SSP. Direct suturing of the calcified SSP was impossible, so long-bite suturing with 8-0 silk in the normal sclera outside the calcified area successfully closed the wound. Postoperative AS-OCT confirmed that the crack in the calcified plaque was closed by connective tissue1).
QWhat is senile scleral softening?
A
This is a condition in which a calcified senile scleral plaque separates and detaches, forming a defect in the sclera. It appears as a vertical, irregularly oval defect located only anterior to the horizontal rectus muscles and covered by a thin conjunctival layer. It differs from scleromalacia perforans in that inflammation is minimal and there is no necrosis. Scleral grafting is necessary if there is a high risk of spontaneous perforation.
On light microscopy with H&E staining, the plaque area shows increased hematoxylin density and decreased cellularity of the sclera. The thickness of the sclera in the plaque area is similar to that of normal sclera. The episclera covering the lesion contains fibers with a corkscrew appearance.
Calcification often occurs in the central part of translucent lesions. Since calcification is most frequently observed in large lesions, it is presumed to be secondary to decreased scleral cellularity. Calcium phosphate, calcium carbonate, and calcium sulfate have been reported as calcium components. Von Kossa and Alizarin red staining confirm deposits of calcium phosphate or calcium carbonate.
Normal sclera is largely composed of extracellular matrix such as collagen fibers and elastic fibers, with an irregular tissue arrangement. In senile scleral plaques, age-related collagen degeneration and decreased cellularity progress, ultimately leading to hyaline degeneration and calcification.
QHow often does calcification of senile scleral plaques occur?
A
Calcification is observed in less than half of cases. Larger lesions have a higher frequency of calcification. The overall prevalence of calcified senile scleral plaques is 3–6.2%, but reaches 22.6% in those aged 70 and older. About one-third of calcified plaques are solitary.
