gms | German Medical Science

The natural avascularity of the cornea is a special privilege for the corneal microsurgeon. In the vascularized cornea, mechanical incisional approaches are feasible, but may lead to bleeding. In contrast, nonmechanical photoablative laser surgery (PTK, PRK, LASIK, penetrating keratoplasty) is typically impossible. A vascularized pannus (i.e. fibrous tissue between epithelium and stroma) can be removed easily before further surgical interventions. In contrast, vascularized stromal scars are by far the greater challenge. Especially concerning a planned corneal transplantation the vascularized cornea requires a differentiated pre-, intra- und postoperative medical and/or surgical assessment and treatment. Strategies to avoid intraoperative complications related to corneal bleeding include pretreatment with high-dose topical steroids or amniotic membrane transplantation (AMT), the intraoperative removal of a vascularized pannus before trephination, topical vasoconstringent agents (e.g. Privin), ice-cold BSS solution, kauterization or incision of major arterial vessels at the limbus as well as preoperative "photodynamic therapy." As an alternative, smaller vessels may be occluded at least temporarily by direct coagulation using the Er:YAG or Ho:YAG laser. In the presence of wide defects of Bowman's layer single interrupted sutures are preferred to a running suture with respect to threatening suture loosening. A simultaneous amnion patch may have antiangiogenic effects. In vascularized herpetic scars the risk of immune reactions exceeds the risk of recurrent herpetic eye disease, since vascularized herpetic scars bear by far less HSV antigens than avascular scars. In conclusion, microsurgery in the vascularized cornea represents a special challenge not only for the surgeon, but also for the patient and the ophthalmologist in charge of the follow-up care. These challenges and the overall limited prognosis of a planned surgical intervention have to be discussed clearly with the patient at an early stage.