Treatment of gross corneal opacification by lamellar and annular lamellar keratoplasty.

PERFORATING keratoplasty is found to be most successful in cases of small central corneal nebulae and keratoconus. In both these conditions the graft lies completely surrounded by healthy cornea. Where there is gross opacification extending widely throughout the thickness of the cornea and especially if degenerative changes are present, then a simple perforating graft rapidly becomes completely opaque and takes on the characteristics of the tissue into which it was placed. The presence of vascularization within the recipient cornea appears to accelerate this process. Experience would show that a perforating graft, to survive as a clear structure, must be placed in a cornea of recognizable structure and that the opacities therein must not exceed two-thirds of the area and thickness of the cornea in contact with the graft. The basic problem therefore is to establish within these grossly opaque, degenerative, and possibly vascularized corneae tissue which will maintain a perforating graft as an optically clear structure. It is common knowledge that a lamellar graft placed in an opaque cornea frequently survives as clear corneal tissue and that in many cases some clarification of the surrounding cornea is seen. When such a lamellar graft has remained clear for a period of atleast 6 months, then a smaller perforating keratoplasty may be successfully performed through its centre. This is a valuable and effective method of dealing with a dense nonvascularized opacity no larger than 7 x 8 mm. and where the peripheral zone of the cornea is clear. An opacity of this size, it is true, could be successfully treated by a single, large perforating graft, but such a method has the following disadvantages: (1) The operation is more difficult and hazardous than a 5-mm. graft and the attendant complications of anterior synechiae and peripheral anterior synechiae due to late reformation of the anterior chamber are more likely to occur. (2) The assessment of the suitability of the peripheral cornea to support a clear graft is frequently difficult.