Several complications can result from pterygium surgery
Recurrence is the most common complication after excision.
Conjunctival surgery has a variety of indications including removing problematic lesions such as pterygium or neoplasm, remodeling to protect other tissues as in conjunctival grafts or trabeculectomy, or bandaging a compromised cornea injured by trauma or infection. My special guests in this column are Sara Akbari and John A. Hovanesian, who are experts on pterygium surgery.
Amar Agarwal, MS, FRCS, FRCOphth
OSN Complications Consult Editor
Histologically, pterygium manifests with elastotic degeneration of the conjunctival substantia propria secondary to ultraviolet light. Indications for removal of this fibrovascular proliferation include with-the-rule or irregular astigmatism, ocular irritation, visual axis encroachment or threat thereof, difficulty with contact lens use, cosmesis, and restriction of extraocular movement. Problems can occur, though, with pterygium surgery (Figures 1 and 2).
Recurrence of the pterygium is the most common complication after excision. The bare sclera technique is associated with 60% recurrence in comparison to 10% with conjunctival autograft placement and 14% with amniotic membrane transplant (AMT) in primary excision. Re-excision of the pterygium with conjunctival autograft and concomitant application of mitomycin C 0.01% to 0.04% to the sclera bed for 3 to 5 minutes has been seen to decrease the chance of recurrence. Recurrence rates of 3% to 43% have been cited with this approach and are similar to postoperative MMC drop use at 0.005% to 0.04% four times daily for 1 to 2 weeks. However, intraoperative MMC use is more tolerable for the patient. Close attention should be paid to delivering appropriate concentrations of MMC to the scleral bed because intraoperative MMC is associated with sclera melting and delayed conjunctival healing, Additionally, corneal contact should be avoided because its use can be associated with corneal melting and punctate keratitis.
Recurrent pterygia are more difficult to remove, with distorted tissue planes and strong scar tissue attachments, which may be attached to rectus muscles, the corneal stroma and the scleral bed. The rectus muscle should be hooked and the insertion site identified to avoid inadvertent disinsertion. Care must be taken to avoid deep dissection into the corneal stroma.
In advanced or recurrent pterygium involving an extensive area of dissection, AMT is a viable alternative to conjunctival autograft (Figure 3). The AMT should be placed basement membrane side up to allow for epithelialization and placed up to the canthal area because fibrovascular encroachment to the graft edges is more likely than with conjunctival autograft. Hemostasis is important because postoperative sub-AMT hemorrhage can serve as a nidus for recurrence. Gluing of the graft or anchoring of the AMT with 10-0 Vicryl sutures should be done to prevent sagging of the graft, which might impede epithelialization. Less recurrence has been seen with the use of tissue glue vs. suture-assisted anchoring.
The conjunctival autograft is placed over the area of bare sclera and may be sutured to the underlying sclera. Another option is the use of fibrin tissue glue, which is placed on the underlying scleral bed for proper positioning of the autograft. In this arena, wound dehiscence and graft dislocation are possible. Both of these can be treated with resuturing or gluing.
Immediate postoperative complications include conjunctival chemosis and graft edema, which are self-limited, resolving with time or topical agents. Improper hemostasis intraoperatively can lead to sub-graft free fluid and blood, which may cause partial or complete dehiscence and may rarely require evacuation to allow for graft adhesion to the underlying scleral bed. An isolated hematoma beneath a conjunctival autograft without significant edge dehiscence can be monitored safely. A small degree of dehiscence, especially at the nasal edge of the graft, can generally be monitored safely as well.
Images: Hovanesian JA
Images: Hovanesian JA
Images: Hovanesian JA
Epithelial inclusion cysts may also occur. Improper apposition of the autograft to the host conjunctiva will increase the risk of this complication, but it also occurs with properly positioned grafts. These cysts are usually translucent with no associated injection and may be excised if the patient is symptomatic.
Poor positioning of the conjunctival autograft and excessive subconjunctival fibrosis may result in bulky, fibrosed and redundant conjunctiva, which, if positioned next to the limbal surface, may result in dellen formation given abnormal tear pooling. Dellen formation, which leads to chronic desiccation, may be treated with excision of excessive subconjunctival fibrosis.
Excision of fibrovascular tissue
The epithelial layer of the cornea is scraped during pterygium removal, resulting in an epithelial defect. The epithelial defect is usually self-limited and heals over time. In the case of extensive pterygium excisions with conjunctival autograft, limbal stem cell deficiency may lead to persistent epithelial defects, which may require punctal plugs, bandage contact lens, tarsorrhaphy and autologous tears. A visually significant scar that limits best corrected visual acuity may require lamellar keratoplasty.
Application of 0.02% to 0.05% (0.2 mg/mL to 0.5 mg/mL) MMC for 1 to 5 minutes to bare sclera during pterygium surgery is most useful for recurrent pterygia. Care must be taken to avoid corneal or conjunctival epithelial contact because epithelialization is markedly affected in cases in which inadvertent contact occurs, leading to persistent epithelial defects. Copious irrigation is necessary, and all instruments should be passed off the surgical tray after MMC application. MMC use can be associated with scleral thinning with uveal tissue show-through or even possibly prolapse requiring a scleral patch. Other complications include photophobia, secondary glaucoma, sudden onset mature cataracts, corneal melt, iridocyclitis, symblepharon formation and punctal occlusion.
Adjuvant beta irradiation is a consideration for prevention of pterygium recurrence. It is dosed between 1,000 rad and 3,000 rad, depending on the tissue depth. The long-term effects of radiation may be observed up to 20 years after its use. Radiation therapy is fraught with complications, including cataract, iritis, episcleritis, and scleral or corneal necrosis with reported cases of endophthalmitis.