Pterygium removal

Surgical removal of pterygium

The treatment of pterygium mainly involves surgical excision and approaches to reduce recurrence of the lesion after surgery. Techniques range from the simplest procedure of bare sclera excision to more complex procedures involving extensive removal of the conjunctiva and Tenon's tissue combined with large conjunctival autografts. Recurrence is the most common cause of failure in pterygium removal surgery, and recurrence rates vary, ranging between 0% and 89% depending on the surgical technique. Complications arising from adjuvant treatments used in pterygium surgery, such as β radiation and Mitomycin C, are also well recognized.

Pterygium surgery can be divided into four main groups, in ascending order of complexity:

1. Bare sclera excision.
2. Excision with primary closure or transposition of the conjunctiva.
3. Bare sclera excision with anti-mitotic adjuvant treatments.
4. Graft transplantation techniques, including conjunctival autograft, conjunctival-limbal autograft, or amniotic membrane graft.

At present, excision of pterygium with a conjunctival autograft is considered the most accepted treatment for primary pterygium removal, with the lowest recurrence and complication rates. In general, the approach to pterygium surgery may vary according to: 1) the extent, size and number of pterygia (single or double head), 2) whether it is a primary or recurrent pterygium, and 3) whether conjunctiva is available for performing a conjunctival autograft. We will delve into these various techniques here.

Pterygium removal using the bare sclera technique

In 1948 the idea was first described of excising the head and body of the pterygium up to the nasal canthus area, allowing the exposed scleral bed to re-epithelialize on its own. Today it is generally thought that simple bare sclera excision is not a good enough method for preventing recurrence, and simple excision should not be performed even for small primary lesions. Recent studies using bare sclera excision as a surgical control for more advanced surgeries report unacceptably high recurrence rates, between 24% and 89%. Pterygium recurrences after bare sclera excision may be very aggressive, sometimes more so than the primary lesion, with the development of symblepharon, restriction of eye motility and gaze-dependent diplopia. Scleral necrosis with a secondary infectious process has been reported following bare sclera excision without adjuvant treatment.

Pterygium removal surgery with conjunctival closure / transposition

Since 1940, many surgeons have felt that leaving bare sclera after pterygium excision does not comply with the general principles of wound healing and closure, hence the many techniques describing closure of the wound/conjunctival defect created after pterygium removal. Closure can be performed by simple approximation of the conjunctival edges, with or without relaxing incisions, or by transposition of the conjunctiva using a pedicle flap from above or below. However, recurrence rates do not appear to be significantly lower than after bare sclera excision. Studies using simple closure or a pedicle flap show high recurrence rates of 37% and 29%, respectively.

Pterygium removal with bare sclera combined with adjuvant treatments

Several adjuvant treatments have been described to reduce the risk of recurrence after pterygium removal. These adjuvant treatments remain popular in many countries because of the relative simplicity of the surgical procedure.

Beta radiation

Strontium-90 was introduced as a treatment for malignant diseases in the fifties, and it was used as an addition after pterygium removal surgery to reduce recurrence of the disease, with recurrence rates around 10%. Today this treatment is no longer in wide use. Its popularity has been declining since the nineties as a result of complications such as late scleral necrosis and infections in areas that had been exposed to radiation, which sometimes appear years later. It is believed that complications associated with ß irradiation are related to the treatment dose and may appear more than ten years after surgery. Severe complications include scleral necrosis, infectious scleritis with or without secondary endophthalmitis, corneal perforation, cataract formation, iris atrophy, secondary glaucoma and a scleral calcium plaque. Milder complications include conjunctivitis, conjunctival scarring, keratitis (inflammation of the cornea), ptosis and limbal stem cell dysfunction which may eventually progress to more severe diseases of the external ocular surface.

Mitomycin C after pterygium removal

Mitomycin C (MMC) is an alkylating agent that inhibits cell division by inhibiting cellular DNA and RNA. Mitomycin C therefore has an anti-proliferative effect and thus reduces the formation of fibrovascular tissue. In this way mitomycin C has a direct effect on reducing pterygium recurrence after simple excision of the lesion.

Mitomycin C is used to treat pterygium in several ways:

1. Subconjunctival injection of mitomycin C directly into the pterygium tissue in the limbus area, a month before bare sclera excision of the pterygium. The accepted volume is 0.1 ml at a concentration of 0.15 mg/ml. The reported recurrence rate was 6% during a two-year follow-up.
2. Intraoperative application of surgical sponges soaked in mitomycin C solution directly onto the scleral bed during bare sclera excision of the pterygium. The accepted concentration is 0.02% for 30 seconds to 5 minutes. Thorough irrigation with a fluid solution such as BSS is then performed. Reported recurrence rates with this application range between 3% and 43%.
3. Postoperative use in the form of mitomycin C drops. The accepted concentration is 0.02%, but concentrations range between 0.005% and 0.04%, instilling one drop 4 times a day for 1 week. Recurrence rates with this method range between 0% and 38%. Reported complications of postoperative mitomycin drops include iritis, limbal avascularity, scleral necrosis, corneal decompensation, perforation of the cornea or sclera, secondary glaucoma and cataract.

Of the three applications mentioned, intraoperative application of mitomycin C is currently the most common approach, because it appears to minimize the total exposure to mitomycin C; however, the reported complications still include keratitis, chemosis, delayed conjunctival healing, granuloma formation, loss of corneal endothelial cells and necrosis of the cornea and sclera. In general, complications of mitomycin C are more likely with higher concentrations and longer exposure times. Although the conjunctival autograft remains the accepted procedure for treating primary pterygium and the potential risks of long-term complications associated with mitomycin C are known, MMC can still have a role as an adjunct to performing an autograft in cases of aggressive recurrent pterygium, but further studies are needed.

Techniques for reconstructing the external ocular surface after pterygium removal surgery

There are several techniques for reconstructing the external ocular surface after pterygium excision, the most common of which include:

1. Conjunctival autograft.
2. Conjunctival-limbal autograft.
3. Amniotic membrane transplantation.

We discuss these techniques below, together with descriptions of the surgical techniques for primary or recurrent pterygium surgery, as well as the use of additional materials in combination with a conjunctival autograft.

Conjunctival autograft after pterygium removal

Conjunctival autograft transplantation is the accepted technique for primary pterygium surgery and represents a gold standard against which other treatments can be compared. It is a safe treatment with low recurrence rates and excellent cosmetic outcomes. The procedure involves obtaining a free conjunctival autograft (usually from the superior temporal conjunctiva) and placing the graft on the exposed scleral bed after pterygium excision (an example of a pterygium before excision, and subsequently an autograft after excision, secured to the scleral bed with fibrin glue and without the use of sutures).

The surgical principles of the conjunctival autograft:

• Excision of the pterygium with adequate removal of all the surrounding fibrovascular tissues and Tenon's tissue.
• Measuring the resulting defect and harvesting a conjunctival autograft that is large (larger by 1 mm compared with the exposed scleral defect).
• Obtaining a relatively thin graft that is relatively free of Tenon (using superficial dissection techniques) in order to ensure minimal graft retraction and better cosmesis.
• Avoiding creating a buttonhole in the conjunctival autograft.
• Securing the graft with sutures or with fibrin glue.
• Pterygium removal can also be performed with a laser — that is, the graft-harvesting step can be carried out using a femtosecond laser.

Evidence supporting the conjunctival autograft after pterygium removal surgery

Five randomized controlled trials reported statistically significant reductions in recurrence rates of primary pterygium after the use of a conjunctival or conjunctival-limbal autograft compared with performing a bare sclera excision. Moreover, two studies found a statistically significant reduction in recurrence after using a conjunctival autograft to treat cases of recurrent pterygium.

Beyond this, five randomized controlled trials compared the efficacy of a conjunctival autograft versus mitomycin C. These trials used a similar technique of conjunctival autograft transplantation after pterygium excision and reported that recurrence rates ranged between 1.9% and 4%. However, the duration of intraoperative mitomycin C application at a concentration of 0.02% ranged between 2 and 5 minutes, and recurrence rates ranged between 5.8% and 20%. These studies had a follow-up period of 12 to 38 months, and the results showed a clear advantage for the conjunctival autograft compared with mitomycin C in preventing pterygium recurrence. Recently, 10-year results after primary pterygium surgery were reported comparing mitomycin versus a conjunctival autograft, and found recurrence in 25.5% of the mitomycin C group and 6.9% in the conjunctival autograft group (p=0.021). They also noted that 71% of the recurrences appeared in the first year after surgery and reported no long-term complications resulting from mitomycin C use.

The use of a conjunctival autograft has been shown to be more effective than the use of an amniotic membrane. Randomized clinical trials comparing the two showed significantly lower recurrence rates in the conjunctival autograft group.

Use of vascular endothelial growth factor inhibitors (anti-VEGF) in pterygium surgery

It has been shown that vascular endothelial growth factor (VEGF) levels are elevated in pterygium, and it has thus been suggested that anti-VEGF agents may have a role as part of pterygium treatment. Avastin (bevacizumab) is a humanized anti-VEGF that binds all VEGF isoforms and has a neutralizing effect by inhibiting the interaction between the VEGF receptors and VEGF. In a recently conducted meta-analysis of 474 patients with 482 eyes in nine randomized controlled trials, it was shown that Avastin had no statistically significant effect on preventing pterygium recurrence, although the safety profile was good. Avastin use was combined with a conjunctival autograft, as an adjunct to the bare sclera technique, or in an attempt to prevent a pterygium about to develop. It should be noted that anti-VEGF treatments have a short half-life and often have to be repeated at high frequency, and they were therefore given subconjunctivally (seven studies) or topically as drops (two studies).

Use of polytetrafluoroethylene in recurrent pterygium

Expanded polytetrafluoroethylene (e-PTFE), known by its nickname Gore-Tex, is a biocompatible fluoropolymer that promotes epithelialization while producing a minimal inflammatory response. A 0.1 mm thick e-PTFE sheet (GORE PRECLUDE pericardial membrane, Gore, Flagstaff, Arizona, USA) was used in a non-randomized comparative study for treating recurrent pterygium with symblepharon and/or restriction of eye movement. This study included 62 eyes from 62 patients with ≥2 recurrences of pterygium of grade T3 or higher (fleshy) with symptoms of binocular diplopia associated with restricted eye movement or symblepharon. All the eyes underwent pterygium excision followed by application of 0.03% mitomycin C, amniotic membrane transplantation and conjunctival-limbal autograft transplantation. The e-PTFE was then inserted into 30 eyes between the amniotic membrane and the conjunctiva (group A), but was not inserted in the other 32 eyes (group B). The e-PTFE was removed four weeks after surgery. Over a mean follow-up period of 17.2 ± 2.3 months, symblepharon, restriction of eye motility, diplopia and conjunctival hyperemia improved significantly in group A compared with group B. After surgery, corneal recurrence developed in one eye (3.3%) from group A, versus eight eyes (25%) from group B. This may be a new method for treating severe recurrent pterygium, although further studies are needed to confirm its efficacy.

Use of 5-fluorouracil (5FU) in cases of impending pterygium recurrence

5FU is a pyrimidine analog that interferes with the synthesis of DNA and RNA. It causes apoptosis of Tenon's fibroblasts and has anti-proliferative properties. A retrospective study showed that weekly intralesional injections of 5FU at a volume of 0.1 to 0.2 ml (an amount of 2.5–5 mg) within a month of recurrence lead to regression of the fibrovascular thickness in 93.3% of cases. About 80% (12 cases) required three injections or fewer, and no complications were observed.

Use of autologous blood to secure the conjunctival graft after pterygium removal

The use of autologous blood as a source of fibrin glue instead of commercial fibrin glue was examined. To date, three studies have directly compared autologous blood with fibrin glue. A small study (20 eyes) compared fibrin versus autologous blood (10 eyes in each group) with similar results between the two groups. Subsequently, in a randomized controlled trial of patients with primary pterygium, 100 eyes in each group, no significant differences were shown in graft detachment rates (2–3%) or recurrence rates one year after surgery (6%–8%). Another randomized trial of 90 patients compared conjunctival fixation with a suture versus fibrin glue versus autologous blood after pterygium excision (30 eyes in each group). Recurrence rates were similar in all three groups. The surgery duration was 2 times longer in the suture group compared with the glue group and the autologous blood group. The use of autologous blood to secure the graft is a good alternative to the use of fibrin glue or sutures for securing the conjunctival autograft after pterygium excision.

Histology / pathology of pterygium

It is advisable to send the removed pterygium to pathology at the end of surgery for histological examination, since the chance of detecting a subclinical malignancy is about 2% (with variation across different geographical regions). Because the clinical features of a pterygium with a subclinical malignancy (conjunctival epithelial neoplasia) do not differ greatly from a pterygium without these changes, it is advisable to send all the specimens for histological examination. In fact, about 60% of the subclinical malignancies discovered after excision of a pterygium lesion were found by surprise/incidentally.

Treatment / drops after pterygium removal surgery

It is customary to give topical treatment with steroids and antibiotics for one to three months after surgery. This is because significant inflammation is possible after the use of a conjunctival autograft. It is important to identify patients who respond to steroids with a rise in intraocular pressures (steroid responders). Although the use of a conjunctival autograft can be highly successful, the technique is complex and requires high surgical skill. Therefore there is probably high variability in the different reports of recurrence.