Orbit
Overview
Radiation therapy (RT) induced damage:
The severity of RT related side effects depends on:
- Total dose of RT prescribed
- Fractionation schedule (the way the radiation treatment is split up during the course of therapy
- Larger fraction size is a dominant factor in predicting late normal tissue toxicity (the larger the fraction size, then the more likely it is that there will be significant long term side effects7
- Quality of the RT
- RT was given using orthovoltage techniques many years ago. This was low energy RT and the dose was magnified in bone. Leading to increased risks of damage and secondary malignancy.
In ophthalmological cancers different types of radiation therapy can be used such as:
- Implant plaque brachytherapy
- Photon treatment (3 –D conformal therapy or IMRT
- Proton beam RT7
Radiation therapy side effects should always be thought of in terms acute and chronic side effects.
Acute side effects: start during the RT or immediately after it has finished and are usually rapid onset and typically reversible7.
Example:
- Bleopharoconjunctivitis is a common acute side effect from RT
- Due to RT exposure to the eyelids and conjunctiva when treating an orbital tumor7
- Causes patient discomfort for a few weeks to months and then resolves completely
- Topical hydration and silver sulfadiazine 1% cream can help decrease the discomfort and chance of infection7
Chronic or late RT induced side effects: delayed in onset and usually do not improve. These side effects may be serious and result in legal blindness. These include1,7:
- Cutaneous and conjunctival telangiectasia
- Eyelash loss
- Cataract
- Dry eye
- Glaucoma
- Retinopathy
- Optic neuropathy
- Diplopia
Chemotherapy Induced Damage:
Chemotherapy can lead to long term orbital side effects - but these are far less frequent and predictable than those associated with RT.
Overview of orbital late effects related to chemotherapy3and radiation therapy:
Orbital structure |
Chemotherapy Late Effect |
Radiation Therapy Late Effect |
| Eye lid | 5-FU and docetaxol have been associated with stenosis of the punctum and tear drainage system.
Eyelid irritation is secondary to excretion of drug into tears and inflammation of the lacrimal gland:
Ptosis reported with long-term corticosteroid use. |
Loss of eyelashes
Skin changes around eye:
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Dry eye is associated with:
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| Conjunctiva | Conjunctivitis is a commonly reported symptom after induction therapy. This is generally transient:
Drugs implicated include:
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Inflammation leads to:
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Keratitis can develop after many different types of chemotherapy:
Corneal hypoesthesia associated with:
Corticosteroids associated with infective keratitis and ulcers. |
RT associated with:
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| Lens | Cataracts most frequently due to corticosteroids.
Cataracts less commonly associated with:
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Lens most radiosensitive structure in eye.
RT causes posterior sub-capsular cataract |
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Corticosteroids are associated with raised intra-ocular pressure and glaucoma.
Other agents associated with uveal damage:
Severe uveal reactions reported after intra-carotid artery chemotherapy with:
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RT causes:
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| Sclera | Scleral damage from chemotherapy is very uncommon:
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The sclera is a radioresistant structure and rarely damaged by RT. |
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Nitrosoureas given systemically can be associated with:
Nitrosoureas given intra-arterially can be associated with:
Cisplatin has been associated with:
Other drugs associated with retinopathy:
Vinca-alkaloids associated with:
5FU can also rarely cause the same clinical picture
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Radiation retinopathy may occur after RT.
On fundoscopy, similar changes to diabetes with:
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| Orbital bone/tissue | Intra-carotid carboplatin may cause severe orbital inflammation with visual loss.
5FU and methotrexate have both been associated with significant peri-orbital edema. |
RT given to children reduces orbital growth resulting in `hypoplasia`or under-development of the orbital bone and soft tissues
There is an increased risk of a second malignant neoplasm many years after therapy. The risk of this is very high for patients with bilateral retinoblastoma. |
