Amyloidosis is a rare group of disorders characterized by the accumulation of abnormal proteins called amyloid in various organs and tissues throughout the body. These proteins, which are misfolded and insoluble, can deposit in spaces both inside and outside cells, leading to gradual organ damage. When these deposits affect the eyes, the condition is known as ocular amyloidosis. Understanding how amyloidosis impacts vision is important for managing its effects.
Understanding Ocular Amyloidosis
Amyloid proteins can accumulate in various parts of the eye and surrounding structures, impairing their normal function. Deposits have been observed in nearly every part of the eye, including the vitreous (the clear gel filling the eye), conjunctiva (the membrane covering the white part of the eye), eyelids, extraocular muscles (which control eye movement), and the optic nerve. For instance, deposits in the trabecular meshwork, the eye’s drainage canals, can lead to increased intraocular pressure and glaucoma.
Amyloidosis can be classified as either localized, affecting only one area like the eye, or systemic, involving multiple organs. The type of amyloid protein present further categorizes systemic disease, with common types including amyloid immunoglobulin light chain (AL), amyloid A protein (AA), and amyloid transport protein transthyretin (ATTR). Localized AL amyloidosis is the most frequent type of ocular amyloidosis, while systemic AL amyloidosis is a more widespread form. Hereditary ATTR amyloidosis can cause significant visual issues due to dense opacities in the vitreous.
Recognizing the Signs
The symptoms of ocular amyloidosis vary depending on the specific part of the eye affected by amyloid deposits. Visual disturbances are common, such as blurry vision or the appearance of “floaters” in the field of vision, particularly if the vitreous is involved. Double vision (diplopia) can occur if amyloid infiltrates the extraocular muscles, restricting eye movement.
Eye discomfort can manifest, including redness, dryness, or irritation. Visible changes around the eye include drooping of the eyelid (ptosis), swelling, or waxy, yellow, or salmon-colored nodules on the conjunctiva. Recurrent bleeding under the conjunctiva can occur due to weakened blood vessel walls. Eyelid discoloration, such as purple or blue skin, may also appear.
Diagnosing Ocular Amyloidosis
Diagnosis begins with a comprehensive eye examination by an ophthalmologist. This assessment involves evaluating various eye structures and noting any visible signs or reported symptoms. Specialized ophthalmological tests, such as a slit-lamp examination, allow for detailed inspection of the front and inside of the eye, helping to identify amyloid deposits in areas like the conjunctiva, cornea, or vitreous. Imaging techniques, including ultrasound or optical coherence tomography (OCT), can provide further insights into the extent and location of deposits within the eye.
A biopsy confirms the presence of amyloid deposits, which is important for definitive diagnosis. This procedure involves taking a small tissue sample, such as from the conjunctiva or vitreous, for microscopic analysis. The tissue is then stained with Congo Red dye, exhibiting a characteristic “apple green” birefringence under polarized light. If systemic amyloidosis is suspected, further evaluation includes blood tests, urine tests, or genetic testing to identify the amyloid protein type and assess other organ involvement.
Treatment Approaches
Treatment strategies for ocular amyloidosis are individualized, depending on the type of amyloidosis, the extent of deposits, and the specific eye structures involved. For mild cases with minimal symptoms, a watchful waiting approach may be adopted, where the condition is closely monitored without immediate intervention. If symptoms progress or vision is significantly affected, more active management becomes necessary.
Surgical interventions address specific issues caused by amyloid accumulation. Vitrectomy, a surgical procedure to remove the vitreous gel, can clear dense vitreous opacities that impair vision. Eyelid surgery may be necessary to correct ptosis (drooping eyelids) or remove masses affecting the eyelids or surrounding tissues. Cryotherapy, a cold treatment, can manage remaining abnormal tissue after surgical removal.
When ocular amyloidosis is a manifestation of a systemic condition, systemic treatments become a primary focus. These treatments aim to reduce the production of amyloid proteins throughout the body. Options include chemotherapy, targeted therapies that interfere with amyloid formation, or organ transplantation. Emerging therapies are being developed to target amyloid deposits more directly. The goal of treatment is to manage symptoms, prevent further damage, and preserve vision, requiring a collaborative effort between ophthalmologists and other specialists.