What is it?
Ocular surface squamous neoplasia (OSSN) is a common malignancy of the conjunctiva and cornea. It can be thought of as a “skin cancer” of the eye.
Typical features of OSSN include:
- Arises near the limbus (junction of cornea and sclera)
- Most commonly found at the 3 or 9 o’clock position
- Fleshy, gelatinous appearance
- Round or oval shape
- Irregular blood vessel pattern
- Minimal symptoms
- Slow growing
Who gets OSSN?
OSSN is more common in patients who are:
- Have had significant sunlight exposure
- Are taking immune system supressing drugs
Differences between OSSN and pterygia
OSSN can mimic a pterygium. In general pterygia:
- Occur at a younger age
- Are more triangular in shape
- Appear flatter rather than gelatinous
- Have more linear blood vessels
- Cause more symptoms
How is it diagnosed?
Some OSSN are first noticed by patients and their friends. In most cases the diagnosis is made by an optometrist or ophthalmologist.
Unusual looking pterygia and definite cases of OSSN are referred to eye specialists for examination with the slit lamp microscope.
OSSN may look very like a pterygium and in some cases only surgical removal and examination of the abnormal tissue by a pathologist will confirm the diagnosis.
Some OSSN can be treated by chemotherapy with Mitomycin C eyedrops.
Mitomycin C (MMC)
MMC is a drug used to treat some types of cancer and to reduce scarring after surgery. It is regularly used in a number of eye conditions including glaucoma surgery. MMC has been used to treat OSSN for the last decade.
MMC in OSSN
MMC is used to treat OSSN when:
- Patients decline surgery
- Tumours are small
- Surgery was unsuccessful in removing all the tumour
- The tumour is aggressive or invasive
- Surgical removal of a large tumour would threaten the viability of the eye
Treatment with MMC
Same eye as above, following successful treatment of OSSN with Mitomycin C.
Patients with suspected or confirmed OSSN typically receive a course of treatment:
- Four times a day
- Week on, week off cycles
- For two to four cycles
Risks of MMC
The risks of MMC therapy are very low but include:
- Failure to achieve eradication of the tumour
- Irritation of the surface of the eye
The traditional treatment of OSSN is surgery.
Indications for surgery
Some patients are best treated by surgical excision. This includes those with:
- Large tumours
- An uncertain diagnosis
Surgery for OSSN
Removal of OSSN is usually performed under local anaesthesia. Traditionally at the time of surgery the surrounding area was frozen or painted with alcohol to eradicate any residual tumour cells. Now the tumour is simply excised and follow up treatment with Mitomycin C is arranged if the diagnosis is confirmed by a pathologist.
FAQs and Links
What causes OSSN?
The most common cause is ultraviolet light.
Can it cause blindness?
Yes, but only if left untreated.
Can it spread to other parts of the eye and body?
Spread is extremely rare.