CALCULATION OF SIZE AND LOCATION OF AUTOLOGOUS IPSILATERAL ROTATING KERATOPLASTY

Background: Autologous ipsilateral rotating keratoplasty is a special form of keratoplasty in which a nonprogressive opacification of the ce ntre of the cornea is rotated towards the limbus and the clear periphe ral cornea is rotated into the optical axis of the eye. This study was performed to find an equation for calculating the best size and locat ion of the trephine for this special kind of keratoplasty Methods: Geo metrical calculations were used to derive the formula Results: We arri ved at the following equation for the best diameter of the trephine: d iameter(trephine) = 3/4 diameter(cornea)-1/2e(e = preoperative distanc e between corneal centre and nearest edge of opacity covering corneal centre). The postoperative diameter of the optical zone is: 2 x diamet er(trephine)-diameter(cornea). A postoperative clear optical zone of h alf the corneal diameter is achieved if the opacity just touches but d oes not extend beyond the corneal centre. For a postoperative optical zone of at least 30% (40%) of the corneal diameter, the opacity is pre operatively not allowed to extend beyond the corneal centre for more t han 20% (10%) of the corneal diameter Conclusion: This equation can be used for calculating the optimum size and location of the trephine fo r autologous ipsilateral rotational keratoplasty. For that purpose it is advisable to take photographs preoperatively.