Granular corneal dystrophy

Granular Corneal Dystrophy (GCD), also known as Groenouw type I dystrophy, is a rare, inherited eye disorder that primarily affects the cornea, the clear, front surface of the eye. This condition is characterized by the accumulation of granular deposits within the cornea, leading to visual impairment. Granular corneal dystrophy is classified as a type of corneal dystrophy, a group of genetic, progressive eye disorders that can affect the clarity and health of the cornea.

Causes and Genetics

Granular corneal dystrophy is caused by mutations in the TGFBI (transforming growth factor, beta-induced) gene, located on chromosome 5q31. This gene is responsible for producing a protein that plays a crucial role in the development and maintenance of the cornea. Mutations in the TGFBI gene lead to the abnormal accumulation of protein in the cornea, forming granular deposits that can impair vision. The condition is inherited in an autosomal dominant manner, meaning only one copy of the altered gene is necessary to cause the disorder.

Symptoms

The primary symptom of granular corneal dystrophy is the presence of granular, opaque deposits in the cornea. These deposits typically appear in the first or second decade of life and can progress, leading to:

• Decreased visual acuity
• Increased sensitivity to light (photophobia)
• Foreign body sensation in the eye

Symptoms can vary significantly in severity among affected individuals, and in some cases, vision may remain relatively unaffected until later in life.

Diagnosis

Diagnosis of granular corneal dystrophy is primarily based on clinical examination, including a detailed patient history and visual inspection of the cornea using a slit-lamp microscope. Genetic testing can confirm the diagnosis by identifying mutations in the TGFBI gene.

Treatment

Treatment options for granular corneal dystrophy are aimed at managing symptoms and improving vision. In the early stages, visual impairment may be corrected with eyeglasses or contact lenses. As the disease progresses, more invasive treatments may be necessary, including:

• Laser therapy, such as phototherapeutic keratectomy (PTK), to remove superficial corneal deposits
• Corneal transplantation in cases where vision is severely affected

Prognosis

The prognosis for individuals with granular corneal dystrophy varies. While the condition is progressive, the rate of progression and the degree of visual impairment can differ significantly among affected individuals. With appropriate management, most people with granular corneal dystrophy can maintain functional vision well into adulthood.

See Also

• Corneal dystrophy
• TGFBI
• Corneal transplantation
• Laser therapy