Pterygia are fibrovascular growths extending from the bulbar conjunctiva onto the cornea. Despite their high prevalence, there is still no consensus regarding the pathophysiology of pterygium formation. Exposure to ultraviolet (UV) radiation is a major risk factor for pterygium formation, but no mechanism has definitively identified which UV light induces the disease. UV exposure is known to cause mutations in the p53 tumor suppressor gene. Studies have linked mutations in the p53 tumor suppressor gene with pterygium formation. ^1,​2 The corneal limbal epithelium has been suggested to provide a barrier between the conjunctiva and the cornea. Limbal stem cells (LSCs) help maintain a healthy corneal surface by renewing epithelial cells. Pterygia have been proposed to represent a zone of LSC deficiency. Histopathologically, pterygia are characterized by a fragmented Bowman’s layer and altered limbal epithelial cells. ^1,​2

Surgical excision of a pterygium is indicated when the pterygium approaches the visual axis threatening occlusion or inducing significant irregular astigmatism. Severe irritation, inflammation, restriction of eye movements, or cosmesis can also be surgical indications. ³ The recurrence of pterygium after excision is the primary complication after surgery. Therefore, modern surgical techniques are designed with the primary goal of reducing the recurrence rate of pterygium.

3.2 Defining Recurrence

After excision, pterygium recurrence appears to be related to accelerated fibrovascular proliferation. Recurrence is one of the most commonly encountered postoperative complications. A fibrovascular extension onto the cornea is considered a true corneal recurrence. This is the most common form described in the literature. However, recurrence is sometimes defined in different stages. The most common method to grade recurrence of pterygium is defined by Prabhasawat et al ⁴ on a 1 to 4 grading scale (▶ Table 3.1).

3.2.1 Current Surgical Management Techniques

3.2.1.1 Bare Sclera Technique

The first successful management technique for pterygium surgery was introduced in the 1940s. This was the bare sclera technique which involves complete excision of the pterygium head, body, and some of the surrounding normal bulbar conjunctiva including Tenon’s capsule. The surrounding normal bulbar conjunctiva is then sutured to the sclera, leaving a bed of bare sclera next to the corneal limbus. ⁵

When primary pterygium excision is completed with the bare sclera technique, the recurrence rate has been reported to be as a high as 24 to 89%. ⁶ This is likely secondary to compromise to the LSCs in the cornea and lack of coverage of the exposed scleral bed. Because of this high recurrence rate, in modern medicine, this technique is now typically combined with some type of grafting such as a conjunctival or amniotic membrane graft (AMG).

3.2.1.2 Conjunctival Autograft

Conjunctival Autograft (CAG) involves placement of an autograft over the exposed sclera after pterygium excision. This autograft is generally obtained from the ipsilateral superior bulbar conjunctiva, but can be obtained from the contralateral eye or other quadrants if needed. The preparation is generally made without inclusion of Tenon’s capsule. ⁷ Many surgeons still consider this the first-line approach both for primary and recurrent pterygium. The recurrence rate when CAG is used is 2.6 to 39%. ⁸ The conjunctival graft can be adhered in several different manners. The most common include sutures, tissue adhesive, and autologous blood (▶ Fig. 3.1).

Sutures

Sutures are the classical method for adhering the CAG and are still favored by many surgeons. Advantages of sutures are that they are easily available, attained at a low cost, and provide excellent graft stability. Intraoperative issues associated with sutures are that their placement does require more time, which prolongs the total case operating time. Postoperative complications include patient discomfort, possibility of granuloma formation, suture abscesses, giant papillary conjunctivitis, necrosis, and scarring.

Tissue Adhesive

The use of tissue adhesive for adhering the CAG is regarded by some authors as superior to sutures. The two types of fibrin glue most commonly used are the TISSEEL VH fibrin sealant (Baxter) and Evicel (Ethicon). ⁸ Other preparations include Tissucol Duo Quick (Baxter) and Beriplast P (Aventis). ⁹ Tissue adhesive preparations are composed of two components: fibrin sealer protein concentrate and thrombin, which are mixed for application. These components are derived from human plasma and are virus inactivated through a treatment process.

Benefits of tissue adhesive include a reduction in surgical time, reduction in postoperative inflammation, and possible reduction in recurrence rate. Graft displacement and graft loss are complications that can occur postoperatively. This can be reduced by ensuring excess glue is removed from the scleral bed intraoperatively. Because of preparation from human plasma, there is a potential risk of transmission of blood-borne diseases. However, preparations are created from a screened donor pool and do go through a viral inactivation process. International safety studies have not shown evidence of transmission of hepatitis virus or human immunodeficiency virus. A risk of allergic reactions has been reported, but the occurrence rate is low at 0.5/100,000 (all reactions) and 0.3/100, 000 (serious reactions). The cost of fibrin adhesive is significantly higher than sutures. ⁸

Sutures versus Tissue Adhesive

There have been numerous studies performed directly comparing the efficacy of fibrin glue versus sutures with regard to the recurrence rate. There is a trend that recurrence may be less frequent when fibrin glue is used. For primary pterygium excision with CAG with fibrin glue reported recurrence rates range from to 3.3 to 14% ^10,​11 and CAG with sutures 8.0 to 20%. ^12,​13 It is theorized that the reduction in postoperative inflammation is responsible for this. Factors associated with this indicate that less graft manipulation is typically needed intraoperatively when fibrin adhesive is used and that sutures may contribute to mechanical postoperative stress.

Autologous Blood

The use of autologous blood has been used as an alternative method to adhere the conjunctival graft. In this technique, the bare sclera is allowed to bleed for several minutes until a small film forms. The free graft is then held in firm apposition to the scleral bed for 6 to 7 minutes. ^9,​14 The graft is checked for stability after surgery, and a pressure patch is applied until postoperative day 1. Benefits of this procedure are that it uses the patient’s own clotting factors, which avoids any chance of allergic or immune response to fibrin adhesives. Drawbacks include increased operating times and risk of graft dehiscence or loss as the adherence can be less pronounced than traditional adhesive.

As this technique is a relatively newer application, and there are fewer trials evaluating its success, a study of 10 patients by Xu et al ⁹ with this technique indicates recurrence rate comparable to that of fibrin adhesive (10%) with no cases of graft dehiscence, which leads the authors to recommend its use. A larger trial of 62 eyes by Nadarajah et al ¹⁴ with this technique did show a similar recurrence rate (10.6%), but a significant risk of graft dehiscence (24.2%), which leads the authors to express caution about its use. Surgeon-dependent factors are likely responsible for this difference, but further study on this technique is needed.

3.2.2 Pterygium-Extended Removal Followed by Extended Conjunctival Transplant

Pterygium Extended Removal Followed by Extended Conjunctival Transplant (PERFECT) is a variation of conjunctival allograft. In this technique, a significantly larger portion of the surrounding conjunctiva is excised surrounding the pterygium, and a corresponding large graft is dissected and placed. Subconjunctival Tenon’s fascia dissection is completed from the limbus to 10 to 15 mm posterior to the limbus. The dissection extends approximately 2 clock hours above and below the conjunctival wound margins almost to the superior and inferior rectus muscles. A corresponding area of superior bulbar conjunctiva is excised to Tenon’s capsule. The large graft is placed and sutured to the bare sclera bed.

The recurrence rate for this technique is reported between 0 and 1.6%. The low recurrence rate is the primary benefit of the procedure. Intraoperative drawbacks include longer operating times, the need for peribulbar or retrobulbar anesthesia, and increased surgical trauma. There is also risk for donor-site complications due to the large size of conjunctival graft that is needed. Transient diplopia has also been reported due to the close proximity to the extraocular muscles encountered during the surgery. ¹⁵

Hirst reported a series of 1,000 patients who had excision with PERFECT. All patients completed at least 1 year of follow-up. A recurrence was observed in only 0.1% of patients. Complication rates were low, but included strabismus, inclusion cyst, granuloma, and a corneal ulcer. ¹⁶

3.2.3 Limbal Conjunctival Allograft

Limbal conjunctival allograft (CLAG) is a variant of conjunctival allograft that involves dissection and inclusion of a portion of the corneal limbus in the graft. The pterygium is excised in the usual manner. The conjunctival graft is created with a length matching the limbal defect with inclusion of clear cornea between 0.5 and 1.0 mm. ^3,​17 The graft is then translocated to the recipient bed and is secured with either sutures or tissue adhesive.

This technique has been shown to have a reduced recurrence rate versus a free conjunctival flap with rates ranging from 0 to 14.6%. ^3,​18 It is hypothesized that the inclusion of LSCs acts as a barrier to recurrence. The low recurrence rate is a benefit of this procedure. Drawbacks include increased operating time and potential for donor-site complications.

Masters and Harris reported a large retrospective study of 234 procedures with CLAG with a median follow-up of 25.5 months. A 0.5 mm of clear cornea was included in the conjunctival graft, which was adhered with sutures. Recurrences were observed in 2.14% of patients overall with recurrence in 0.57% of eyes with primary pterygium and 6.9% cases with recurrent pterygium. ³

3.2.4 Amniotic Membrane Graft

AMG have been described considerably for the treatment of pterygium. AMG are used for their anti-inflammatory, anti-scarring, and anti-angiogenic properties. AMG are either cryopreserved or dehydrated. For pterygium surgery, the pterygium is excised in the usual manner, and an amniotic membrane is applied over the exposed scleral bed, generally with fibrin glue. ¹⁹ The recurrence rate for these procedures has been demonstrated between 0 and 40.9% ^{20,​21,​22} (▶ Fig. 3.2).

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