Case 28 Answers

by Professor Chua & Dr. Tan

These patients underwent bare sclera pterygium excision with intraoperative mitomycin 0.02% applied topically for one minute. At the 4-week post-operative reviews, the patients complained of the following appearance.

Patient 1: Rounded lesion at the edge of the excised conjunctiva.

Patient 2. Raised red lesion on the sclera surface.

Patient 3. Reddish lesion under the excised edge of conjunctiva.

Patient 4. Red lesion under the edge of the excised conjunctiva.

a. What is the diagnosis?

Tenon's capsule granulomas. Some authors have also called this pyogenic granulomas (the term is wrong as shall be seen later).

They are benign vascular tumours of the mucous membranes (and can occur on skin). The lesions develop rapidly over a period of weeks to maximum size of 0.5 to 2 cm; they are soft, elevated and slightly pedunculated¹. In the above patients, the lesions represent overgrowing of the Tenon's capsules during the healing process.  Histologically, the lesions show no suppurative inflammation (as the word pyogenic implied). Spontaneous involution is uncommon despite the use of topical steroids. The treatment of choice is excision of the lesion.

There are two possible explanations for their developments:

1. The exposure of Tenon’s capsule resulted in friction with the upper eyelid during blinking can lead to an overgrowth of the exposed tissue².

2. The fragile epithelium that covers the recipient site can easily erode. The resulting necrotic epithelial cells which are not removed by blinking can incite  a foreign body granuloma.

b. Suggest ways to reduce the occurrence of these problems?

Avoiding exposure of the Tenon's capsule is the most effective way of preventing  Tenon's capsule granuloma. These can be achieved by:

 

i. Following bare sclera excision, the conjunctiva usually contracts more than the Tenon's capsule resulting in Tenon's capsule exposure (Figure 5). To reduce the exposure, the Tenon's capsule is pulled into the centre of the bare sclera and excised until no exposure is seen. This allows the Tenon's capsule to be covered by the conjunctiva.

 

ii. Covering the exposed areas following pterygium excision. This could be achieved by using various transplanted tissues such as autologous conjunctiva and amniotic membrane. 

 

Figure 5. This patient was reviewed one week after pterygium operation. Note the whitish Tenon's capsule under the retracted conjunctiva. Such exposure increases the risk of Tenon's capsule granuloma.

References:

1. Starck T, Kenyon KR, Serrano F. Conjunctival autograft for primary and recurrent pterygia: surgical technique and problem management. Cornea 1991;10:196-202.

2. Vrabec MP, Weisenthal RW, Elsing SH. Subconjunctival fibrosis after conjunctival autograft. Cornea 1993;12:181-