Birmingham, AL—Because radiation therapy carries a risk for a variety of acute and late ocular complications, optometrists can have an important
long-term role in the care of cancer patients, said Tammy Than, MS, OD.
Dr. Than
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"About 60% of cancer patients receive radiation at some point in their course of care. With new techniques, radiation can
be very effective, but it is also associated with a number of ocular side effects, some of which can present decades after
the treatment," said Dr. Than, associate professor of optometry, University of Alabama at Birmingham.
Radiation-induced ocular complications are a result of direct damage, so their occurrence requires that the eye is within
the irradiation field. The risk depends on the number of fractions administered, fraction size, and cumulative dose.
Of all ocular structures, the crystalline lens is most sensitive to radiation damage, although placing a corneal lead shield
during the treatment can reduce the risk of cataract development. Radiation-associated dry eye
Dry eye is also very common since the superficially located structures that produce tear film components are highly susceptible
to radiation-induced damage. Practitioners need to realize that radiation-associated dry eye is a very severe disorder mandating
aggressive intervention.
"In one study of patients receiving radiation therapy, almost two-thirds had visual acuity of 20/200 or worse because of their
dry eye disease," noted Dr. Than. "In another study, 12 of 30 patients receiving a radiation dose of at least 5,000 cGy required
enucleation because of dry eye."
This patient has severe dry eye that is typical in patients with a history of head/neck radiation therapy. (Photo provided
by Tammy Than, MS, OD)
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To keep the eyes "moisture protected," patients need frequent instillation of nonpreserved ocular lubricants. Punctal occlusion,
moisture chambers, and topical cyclosporine ophthalmic emulsion (Restasis, Allergan) also may be helpful. Some patients may
need to have a conjunctival flap or tarsorrhaphy to protect the ocular surface.
Systemic therapy with cholinergic agonists that stimulate secretion by the lacrimal gland also should be considered. Two agents
are currently available, pilocarpine (Salagen) and cevimeline (Evoxac), although neither is approved for dry eye.
"Optometrists who are not comfortable prescribing these medications for off-label treatment should at least consult with the
patient's primary care provider about their possible use," said Dr. Than.
Eyelids and lashes
As the thinnest skin in the body, the eyelids and adnexal structures are particularly susceptible to radiation-induced complications.
These include permanent telangiectasia, madarosis, scarring leading to entropion or ectropion, and trichiasis. Topical bimatoprost
ophthalmic solution 0.03% (Latisse, Allergan) may be useful for patients with loss of lashes.
"Lash loss is likely to be permanent if the radiation dose was > 5,000 cGy, so bimatoprost treatment should be started only
if there is evidence of natural regrowth," she said.
The etiology of trichiasis may involve entropion, remodeling of lid tissue, or direct follicular damage, and its management
may require strategies more aggressive than epilation.
Radiation can also cause nasolacrimal duct obstruction leading to epiphora. Intubation with silicone tubes that are placed
prior to the radiation therapy and removed several months after it is completed is recommended to prevent this complication,
although patients will need to be referred for this procedure that requires suture anchoring.
"This prophylactic strategy offers a great service because patients who develop epiphora may need to undergo dacryocystorhinostomy,"
noted Dr. Than.
Epiphora also can occur if the nasolacrimal duct is open but peristalsis has been affected by muscle damage. Placement of
polyvinylpyrrolidone perforated plugs (FCI Ophthalmics) to facilitate tear outflow can be helpful in this situation, although
the device insertion can be somewhat challenging.
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