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Pterygium excision with mitomycin C (MMC)

Rationale: The use of MMC as an anti-fibroblastic agent is useful to help reduce fibroblast proliferation afetr pterygium excision. The use of MMC  reduces the surgical time. Although good results have been reported with its use, the possibility of scleral complications exists – even years after its use. Since abuse of MMC, when prescribed as postoperative drops has been described, it is generally preferable to use it during surgery.

Intraoperative use:
A mitomycin C  (0.02%) soaked sponge  is  kept for a period of   3-5 min over the bare scleral bed – after pterygium excision and then washed off.
This may or may not be followed by a conjunctival autograft. Placing a graft gives the advantage of retaining some vascularity in the area and thus preventing occurrences of complications such as necrotising scleritis postoperatively

Mitomycin  C - 0.02%

Available as 2 mg powder .
Add 10 ml normal saline solution
= 0.2mg/ml (0.02%)

Pterygium excision with amniotic membrane transplantation

In the event of a two headed pterygia or a very large pterygia with conjunctival loss amniotic membrane can be used to cover the defect.

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However, the use of this approach has been reported to have fairly high recurrence rates in most reported studies. In this context, it may be best to reserve the use of this approach in eyes which have had extensive removal of conjunctiva, with an extensive defect, which may be hard to close with a conjunctival graft. In these instances, the use of an amniotic membrane graft can be considered to help reconstruct the ocular surface.

Fibrin Glue

The glue comes in two parts – a vial containing fibrinogen powder and another containing thrombin powder. The conjunctival graft is excised in the usual manner and is place stromal side up on the cornea, with the limbal edge adjacent to the limbus. After reconstituting the vials with the provided solutions and mixing them well – these are applied to the bed – this can be either done simultaneously using the modified syringe applicator provided, or can be used as two separate solutions. If the latter, place the sticky fibrinogen in the scleral bed, and the liquid thrombin on the undersurface of the conjunctival graft. The graft is then flipped over into the bed and two fine tipped forceps are used to stroke the graft to fit it into the bed. The edges of the graft are then coapted with the margins of the host conjunctiva to unite the edges of the graft with the margins of the conjunctival bed. Since fibrin formation occurs over 45 seconds, there is enough time to perform these maneuvers.

Lamellar Keratoplasty

When extensive corneal scarring in the visual axis coexists with the pterygium, a lamellar corneal graft is required along with pterygium excision and adjunctive procedures to improve vision.

Combination Approach

In very extensive pterygia, often recurrent, with significant conjunctival loss, it may be necessary to combine the above approaches – using extensive pterygium excision, with a conjunctival autograft, amniotic membrane transplant and intraoperative MMC. This may or may not need to be combined with a lamellar corneal graft for vision restoration.

Pterygium subconjunctival avastin injection

Rationale: As a pterygium is a fibrovascular proliferation,  its growth requires new vessel formation. It is hypothesised that increased angiogenic inhibitors may regulate the formation and progression of pterygia. Studies have been done using bevacizumab 2.5mg/0.1ml  injected at the limbus at the head of a possible recurrence. More than one injection may be required. Subconjunctival bevacizumab results in a short-term show a decrease in vascularization and irritation. Further long-term studies are needed to  investigate the efficacy of bevacizumab as an adjunct to surgical excision or in combination with topical treatment.

COMPLICATIONS

1. Intraoperative problems: Globe rupture during peribulbar block, damage to the rectus muscle, and intraocular penetration during graft suturing have been reported. Excessive corneal tissue removal during pterygium head removal and perforation can also occur.
2. Recurrence: is the most important complication of pterygium surgery. Fortunately with well performed surgery using the options mentioned above, recurrence rates can be as low as 3.8%. Recurrences can be of two types – across the graft, if the graft used is not viable; or around the graft – if inadequate excision of the pterygium and or a small graft is used.
3. Graft problems: include too large or too small a graft, buttonhole in the graft, improper suturing leading to an unsecured graft on the sclera, inversion of the graft with the epithelial side placed facing the sclera, and a large hematoma under the graft preventing a graft take.
4. Infection: as with any surgery, this can happen in pterygium surgery. can occur if complete excision of the pterygium is not done. Since corneal epithelial injury occurs during surgery, the infection can occur in the cornea, sclera or both. 
5. Granuloma: Usually seen after bare sclera surgery, the granuloma can occur in the scleral bed, or in cases of a conjunctival autograft, can occur at the site of donor graft excision, if the Tenon’s there is hydrated and does not get covered with conjunctiva in the healing period.
6. Surgically induced necrotising scleritis: has been reported. Scleral melts after the use of MMC  have also been reported.
7. Strabismus : recurrent pterygia may be difficult to dissect  and damage to the rectus muscle may result in strabismus.
8. Diplopia: can result from cicatrizing changes in the conjunctiva after excision, affeting free movement of the eye.
9. Vision changes: from the corneal irregularity that can occur after pterygium removal from the cornea.
10. Steroid induced IOP rise: is a problem in some patients, who are steroid responders.

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