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Corneal epithelial defects related to high postoperative astigmatism
  1. R Singh,
  2. T Umapathy,
  3. B B Kulkarni,
  4. H S Dua
  1. University Hospital, Queens Medical Centre, University of Nottingham, Nottingham, UK
  1. Correspondence to: Professor H S Dua Division of Ophthalmology, University Hospital, Queens Medical Centre, B Floor, Eye ENT Centre, Nottingham NG7 2UH, UK; harminder.duanottingham.ac.uk

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High and sometimes irregular astigmatism is not an infrequent complication following anterior segment surgery such as suturing of large wounds and corneal transplants. Abnormal corneal topography may affect tear film stability adversely. We present the case of two patients who had persistent postoperative epithelial defects in the lower third of the cornea, in the presence of high corneal astigmatism despite aggressive lubrication. Upon addressing their high corneal astigmatism their epithelial defects resolved.

Case 1

An 84 year old man underwent a repeat, HLA matched, penetrating keratoplasty following a failed graft for pseudophakic bullous keratopathy. He had had dry eye symptoms with his primary graft with signs of punctate keratitis treated with non-preserved lubrication. His repeat graft was uneventful. He was treated with tacrolimus postoperatively to minimise risk of rejection.

Postoperatively, he had persistent dry eye symptoms for which he was prescribed non-preserved topical lubricants. Six months postoperatively sutures in the horizontal meridian were removed to address “against the rule” astigmatism. He presented a month later with an epithelial defect in the lower third of his graft with an underlying superficial stromal melt (fig 1A). Corneal topography at this time revealed significant “with the rule” corneal astigmatism of 13 dioptres (fig 1B). Tight sutures were cut and non-preserved lubrication, dexamethasone 0.1% and chloramphenicol 0.5%, was continued. Resolution of the epithelial defect followed rapidly with no further progression of stromal melting.

Figure 1

 (A) Diffuse slit lamp photograph of the corneal graft showing an epithelial defect and superficial stromal melting in the lower third. (B) Corneal topography showing steep with the rule astigmatism.

Case 2

A 72 year old woman with progressive cataract underwent uncomplicated extracapsular cataract surgery. She had been diagnosed with keratoconjunctivitis sicca 15 years previously, which at times required aggressive topical lubrication to control. Postoperatively, she developed a large central corneal defect in the lower third of the cornea. Despite aggressive lubrication the epithelial defect persisted for weeks. She had tight superior wound sutures causing 11.0 dioptres of astigmatism. It was suspected that this could be impeding normal corneal wetting. Upon their release and continued topical lubrication the epithelial defect resolved.

Comment

It is possible that an irregular corneal surface interferes with normal maintenance of the ocular surface tear film. This abnormal tear distribution is likely to be exacerbated by an underlying dry eye state. If tear deficiency and degree of astigmatism are extreme, desiccation of the corneal epithelium is possible, leading to non-healing defects and associated sequelae.

In cases where high or irregular astigmatism is associated with postoperative non-healing corneal defects, addressing the degree of corneal astigmatism may help restore physiological tear dynamics and resolution of the epithelial defect. Corneal sutures may themselves impede epithelial migration,1 but if this were the only explanation all grafts would be exposed to the same risk. Conversely, not all patients with high astigmatism (non-surgical) have epithelial defects. This would suggest that more than a single factor is at play in such situations. To our knowledge high astigmatism as a contributory factor to development of persistent epithelial defects post operatively, has not been previously considered.

Reference

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