Amyloidosis is a group of disorders characterized by the abnormal accumulation of misfolded proteins, known as amyloid, in various organs and tissues. These proteins aggregate into insoluble deposits, progressively impairing organ function. While often associated with damage to the heart or kidneys, these deposits frequently target the eye and its surrounding structures. Ocular involvement can be the first noticeable sign of a broader systemic disease, making detection of these changes an important clue for diagnosis.
How Amyloid Deposits Affect Eye Structures
Amyloid protein deposition causes functional and structural changes across the eye. Amyloid can infiltrate nearly any ocular structure, including the external adnexa, the transparent front surface, and the internal cavities. The location of these deposits determines the type of symptom a patient experiences.
In the vitreous humor, the clear, gel-like substance filling the eyeball, amyloid aggregates form dense opacities. These deposits are often described as sheets, cobwebs, or pearls, physically blocking light passage to the retina. This clouding is common in hereditary forms of amyloidosis, such as transthyretin (ATTR) amyloidosis.
The cornea, the transparent front layer of the eye, is another frequent site of protein accumulation. Amyloid deposits here cause various forms of corneal dystrophy. They often manifest as distinctive, branching, lattice-like patterns within the corneal tissue, compromising its clarity.
The delicate draining system of the eye, the trabecular meshwork, can become clogged with protein material. This blockage impedes the outflow of aqueous humor, the fluid that nourishes the front of the eye. The resulting fluid buildup increases pressure inside the eye, leading to optic nerve damage and secondary glaucoma.
Recognizing the Specific Ocular Symptoms
Ocular amyloidosis symptoms vary widely depending on whether deposits are localized to the surface, adnexa, or internal structures. Symptoms related to the external ocular adnexa, including the eyelids and surrounding tissues, are often the most noticeable. Amyloid deposits in the eyelid muscles can cause ptosis, a progressive drooping of the upper eyelid.
Amyloid infiltration can make small blood vessels in the surrounding skin fragile, leading to purpura (dark or purple patches), especially around the eyes. If deposits affect the extraocular muscles, patients may experience restricted eye movement and double vision (diplopia). The conjunctiva, the clear membrane covering the white of the eye, may develop firm, waxy-looking masses that are pink or yellow.
Corneal involvement frequently results in irritation, a foreign body sensation, and light sensitivity (photophobia) due to the rough surface. Lattice corneal dystrophy, characterized by fine, thread-like lines, causes progressive visual reduction as corneal clarity is lost. Accumulation of amyloid in the lacrimal glands can also contribute to severe dry eye, known as keratoconjunctivitis sicca.
When amyloid affects internal structures, symptoms are more disruptive to vision. Vitreous opacities cause patients to see floaters, often described as “cobwebs” or “snowball” clouds, leading to progressive, painless blurring of vision. Dense deposits can severely impair visual acuity. Glaucoma, caused by trabecular meshwork blockage, progresses slowly and painlessly, requiring regular monitoring to prevent permanent vision loss.
Confirming the Diagnosis of Ocular Amyloidosis
Confirming that eye symptoms are caused by amyloidosis requires a specialized approach beyond a standard eye exam. The ophthalmologist uses a slit-lamp microscope to examine the cornea for characteristic lattice-like patterns or gelatinous deposits. This examination also checks the iris and pupil for irregularities, such as a scalloped appearance, which signals internal amyloid deposition.
For deposits deeper inside the eye, imaging techniques visualize the vitreous humor and retina. Ocular ultrasound or optical coherence tomography (OCT) detects and maps the extent of vitreous opacities, which may be invisible during a routine examination. These scans help determine the density and location of the protein aggregates.
The definitive diagnosis relies on a biopsy of the affected tissue, often taken from the conjunctiva, eyelid, or vitreous. The sample is stained with Congo red dye, causing amyloid deposits to exhibit a unique apple-green color under polarized light. A confirmed diagnosis of ocular amyloidosis necessitates a subsequent systemic workup to determine if the condition is localized or part of a widespread systemic disease.
Treatment Strategies for Eye Involvement
Management of ocular amyloidosis is tailored to the specific structures involved and symptom severity. For mild adnexal or conjunctival involvement, observation may be appropriate. If deposits form a significant mass or cause functional issues like severe ptosis, surgical excision is often the preferred treatment.
Surgical debulking removes the physical mass from the eyelids or orbital tissues, aiming to restore function and appearance. When vision is severely compromised by dense vitreous opacities, a pars plana vitrectomy is performed. This surgery removes the cloudy vitreous gel and amyloid aggregates, substantially improving visual acuity.
Corneal symptoms, such as dryness, are managed with topical lubricating eye drops and artificial tears. For advanced corneal dystrophy that significantly impairs vision, a corneal transplant may be considered, though amyloid re-deposition in the transplanted tissue is a risk. Glaucoma is treated with pressure-lowering eye drops or, in complex cases, with surgery to maintain safe intraocular pressure. While these treatments manage local eye problems, preventing new ocular damage depends on concurrently treating any underlying systemic amyloidosis.