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Descemetocele following a simple avulsion procedure for pterygium
  1. Singapore National Eye Centre,
  2. 11 Third Hospital Avenue, Singapore 168751
  1. M Sivakumar.

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Editor,—Simple excision of a pterygium with or without a conjunctival autograft is a routine surgical procedure with generally minimal complications unless adjunctive antimitotic agents are used. We report an unusual and severe intraoperative complication of severe descemetocele formation in a patient who underwent a routine avulsion procedure1 2 for a primary pterygium.


A 47-year-old Malay woman with end stage renal failure on haemodialysis was found to have bilateral severe nasal primary pterygium, grade 4 in the right eye covering the pupillary axis and grade 3 in the left eye (Fig 1). In the right eye, areas of the cornea not directly affected by the pterygium invasion were also noted to be abnormal with diffuse peripheral stromal opacities and perilimbal superficial vascularisation. There was no history of previous ocular disease or trauma.

Figure 1

Right eye showing a nasal pterygium covering the pupillary axis.

A pterygium excision with a conjunctival graft was performed in the right eye via a simple avulsion technique. Surgery was performed by a senior corneal surgeon who has performed over 300 conjunctival autograft procedures for primary and recurrent pterygium. The avulsion procedure involves grasping the inferior horizontal edge of the pterygium with conjunctival forceps and exerting traction to avulse the head and inferior aspect of the pterygium from the cornea, at the level of the Bowman’s membrane (Fig 2). Concomitant scraping with a No 64 Beaver blade was additionally performed to facilitate clean division from Bowman’s membrane. This procedure has a theoretical advantage over sharp dissection or superficial keratectomy in that the natural cleavage plane3 between the pterygium and Bowman’s membrane is respected, whereas sharp dissection may inadvertently result in a deeper stromal plane with excessive loss of corneal stromal tissue.

Figure 2

Right eye showing a bulging descemetocele following an avulsion procedure for a nasal pterygium.

In this patient, modest traction to disinsert the pterygium resulted in avulsion of the pterygium together with significant adjacent corneal stromal tissue, resulting in a cleavage plane deep within the posterior stroma. This plane, which occurred over approximately two thirds of the surface area of the cornea (over the original pterygium site), resulted in a residual corneal thickness of less than one quarter of the original stroma, and a bulging central descemetocele (Fig 2). The corneal stroma was noted to be opaque and abnormally friable in consistency. After removal of the pterygium, a conjunctival autograft was performed to cover the scleral bed. The large corneal defect was left bare, as corneal donor tissue was unavailable.

Postoperatively, the degree of corneal stromal loss associated with bulging of the descemetocele was confirmed by slit-lamp microscopy, and the patient subsequently underwent successful tectonic lamellar keratoplasty 2 days after the initial pterygium excision, when a corneal donor was obtained (Fig 3). Six months postoperatively, the lamellar graft remains clear, and visual acuity is correctable to 6/30 with corrective glasses. The conjunctival autograft remains in place and no recurrence of the pterygium has occurred. Histology of the pterygium tissue combined with deep corneal stromal tissue revealed a total lack of stromal lamellae, with fibrovascular tissue containing numerous dilated capillaries and a perivascular lymphocytic infiltrate.

Figure 3

Right eye showing tectonic lamellar graft for a bulging descemetocele.


Excision of a pterygium is generally not associated with significant corneal loss unless superficial keratectomy is performed without undue attention to the depth of keratectomy. The avulsion procedure performed in this patient is similar to that described by Coroneo.4 A combination of pterygium tissue traction, blunt dissection, and scraping of Bowman’s membrane enables clean division between pterygium tissue and Bowman’s membrane. This, therefore, theoretically reduces the risk of inadvertent loss of corneal tissue. The opaque and friable nature of the underlying corneal stroma suggests significant degenerative changes of the underlying corneal stroma, which is consistent with the histology. Although underlying stromal scarring is common beneath pterygia, stromal density and consistency are usually unaffected, and careful dissection at the plane of Bowman’s membrane is usually possible.

Retrospectively, the presence of pre-existing deep stromal opacification and vascularisation in adjacent corneal tissue unaffected by pterygium invasion may have suggested a pre-existing abnormal corneal state. The possibility of systemic disease affecting corneal status in this patient is raised. It is not inconceivable that the systemic or metabolic abnormalities present in end stage renal failure or haemodialysis may have played a role in the development of corneal stromal degeneration.

Pterygium excision is generally regarded as a routine surgical procedure which may be performed by residents in training. In Cameron’s words ‘Many surgeons consider the humble pterygium to be unworthy of their talents and sometimes for this reason, or under pressure of work, delegate the excision to junior staff who in turn treat the condition in cavalier fashion, with in some cases poor results’.5

This case illustrates that pterygium surgery may not be routine and free from complications. We propose caution during surgery when severe pterygium is associated with significant stromal disease.