Radiation effects on Eye & Periorbital Tissues
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A recent article in the Red Journal has a nice summary of radiation effects on eye and periorbital tissues. You should be reading the full text but for those who are too busy here is the summary.
Ocular Risks From Orbital and Periorbital Radiation Therapy: A Critical Review. V. Swetha E. Jeganathan, Andrew Wirth and Michael P. MacManus. International Journal of Radiation Oncology*Biology*Physics Volume 79, Issue 3, 1 March 2011, Pages 650-659
The full article is available at Sciencedirect
Structure | Acute RT effects | Late RT effects |
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Eyelids | Loss of eyelashes (~ 20 Gy in 2 Gy/#), Skin desquamation (as skin elsewhere) and erythema, Meibomian gland dysfunction (33% risk of chronic xeropthalmia with 20 -24 Gy) | Cutaneous telengeiectasis, ciliary madarosis depigmentation (>50 Gy), scarring of eyelid with entropion, disturbances in growth of eyelashes |
Conjunctiva | Acute conjuctival injection, watering and discomfort (>30Gy). Differentiate from viral conjunctivitis which is more painful, lasts longer and can cause nodal enlargement | Conjuntival telengiectasia (> 30Gy), chronic conjunctivits, conjunctival squamous metaplasia and conjunctival keratinization ( > 50 Gy); symblepharon and permanent scarring of conjunctiva ( > 60 Gy) |
Lacrimal Gland | Very common during course of RT but dose volume estimates not available. Manifest as xerophthalmia | Atrophy & fibrosis of Gland (> 50Gy/ 20 Gy SF), corneal vascularization & opacification ( > 57 Gy), Keratoconjunctivitis Sicca ( >60 Gy). Latency of effect 4 - 10 year with 30 - 35 Gy and < 1 year with > 57 Gy. Tolerance dose for entire gland estimated around 30 - 40 Gy. Illappreciated effect is canalicular fibrosis secondary to RT, typically observed with doses > 60 Gy. Paclitaxel can increase risk further. |
Cornea | Mostly 2ndary to dry eye. Punctate epithelial erosions (30 - 50Gy), Corneal edema (40 - 50 Gy), corneal ulceration ( > 60 Gy) | Rarely corneal conjunctivazation ( > 50 Gy) |
Iritis | Transient Irits (10 Gy SF) | Persistent Iritis (>70 Gy with conventional frractionation); Neovascular glaucoma is a rare complication. Typically after ischemia of iris and angle |
Lens | NA | Cataract formation. Emami estimates are 10 Gy for TD5/5, Hall estimates 50% risk after 1 Gy exposure in childhood. 2.5 - 6.5 Gy has a 33% risk of progressive cataract after 8 - 10 years |
Retina | NA | Radiation Retinopathy (severe if involves macula) - Risk increases steeply after 50 Gy dose. TD 5/5 - 45 to 50 Gy, Threshold dose 30 - 35 Gy. Hyperfractionated RT can reduce risk. |
Optic Nerve | NA | Radiation induced Optic Neuropathy (RION) 0% at doses ≤50 - 55 Gy, 3% -7% between 55 - 60 Gy. Toxicity lowered for pituitary tumors. Fraction size < 1.9 Gy significant sparing effect. |
Jeganathan et al have published a nice review of radiation related side effects in eyes and periorbital tissue. They deal with acute and late effects as well as the treatment and dose volume parameters. A very nice summary specially useful for the juniors and exam going.