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Editor,—The report on Descemet’s membrane detachment by Mulhern and coauthors1 requires comment.
In a report last year, we detailed three cases of Descemet’s membrane (DM) detachment after intraocular surgery, one of which occurred after preparation of a phacoemulsification scleral pocket.2 The detachment involved the visual axis, was recognised intraoperatively, and an attempt at primary repair was made. After a successful secondary repair, final visual acuity attained was 6/6. We suggested that efforts should be made at the time of primary surgery to repair a recognised large DM detachment, and that an expanding gas such as SF6, with or without suture fixation, should be used.
The management of the case reported by Mulhern and coauthors involved primary excision of a large fragment of detached DM. This action takes no account of the possibility that the detachment may settle spontaneously postoperatively, nor of the varied techniques available for secondary repair which we summarised.2
None of the potential complications of DM repair mentioned by the authors precludes later penetrating keratoplasty if the outcome of the repair is sufficiently unsatisfactory, and it is difficult to imagine how a subsequent penetrating keratoplasty could be ‘facilitated’ by excising the membrane.1 Similarly, it seems implausible to suggest that sutures transfixing the membrane would induce unacceptable astigmatism, when they would straddle no corneal incision, could be removed within months of the repair, and when the alternative, by excising DM and its attendant endothelium, is to irrevocably commit the patient to a procedure with a much higher potential to generate astigmatism, which has a visual rehabilitation in excess of 1 year and a lifetime follow up.
Our cases were repaired under general anaesthesia, but this is almost certainly not essential, and topical, sub-Tenon’s, or regional block anaesthesia could be employed: if required, a series of relatively brief attempts to reattach the membrane could be undertaken before considering surgery as major as penetrating keratoplasty.
With the range of options available it is difficult to envisage any situation in which primary excision of a large fragment of detached Descemet’s membrane can be justified.
References
Reply
Editor,—We welcome Walland’s recent letter concerning our case of Descemet’s membrane detachment during phacoemulsification surgery. In our article, we did allude to the various techniques which may help reappose Descemet’s membrane to the stroma; and to the fact that spontaneous reattachment of small planar detachments can occur. However, if our case report was read carefully, it can be seen that, given the tiny apical residual attachment of the involved fragment, and the fact that the detachment involved almost 40% of the corneal surface, reattachment was unlikely. Furthermore, if the decision is reached that the fragment cannot be reattached, this fragment should be excised as the extent of the detachment may increase further during trephining in a subsequent penetrating keratoplasty procedure, thus increasing the detachment and potentially extending it into the peripheral cornea.
Author’s reply
Editor,—Thank you for the opportunity to offer further comments in relation to Mulhern’s report and his letter of reply.
I would assure Mr Mulhern that his case report was read carefully: part of the difficulty with the report lies in the fact that the text makes no mention of a tear XY (Fig 1), while the illustration footnote makes no mention of a tear YZ. Either the membrane was torn along three sides and secured only at an apex point (Z), in which case it would be highly unlikely that the tear would extend peripherally upon trephination for penetrating keratoplasty (PK) (as suggested in his reply), but would rather complete its detachment at point Z; or the membrane was detached along two sides with the flap based along the third, in which case it would be ideally suited to a trial of either spontaneous reattachment or active intervention. In neither situation is excision of the DM fragment helpful, and excision commits the patient to a PK.
There have been several reports in the literature (some cited in our article, ref 2 in my original letter) of DM detachment in excess of the 40% area in Mulhern’s case including subtotal, non-planar detachments, which have successfully resolved either spontaneously, or with active intervention, and these criteria therefore offer no justification for excision of a detached DM fragment.