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A Simplified Mathematical Model

Natalie A. Afshari, MD; Scott M. Duncan, BS; Tasha Y. Tanhehco, BS; Dimitri T. Azar, MD

Arch Ophthalmol. 2006;124:410-413.

Objective  To calculate clinical guidelines for the optimal location and size of a rotational autokeratoplasty.

Methods  The ideal graft size and trephine decentration for a rotational autograft were calculated based on scar location using geometric models. Mathematical variables were set to maximize postoperative visual acuity and for generalization of the geometric model. This model was used in a rotational autokeratoplasty of a patient with a history of a corneal scar and diplopia. An 8-mm autograft was decentered 0.5 mm superiorly and rotated 180° to relocate the scar to the superior aspect of the cornea, out of the patient's vision.

Results  For cases that satisfy the given variables, a graft diameter of 8 mm with a decentration of 0.5 mm balances maximization of scar removal and scar movement superiorly, with minimization of discrepancy in corneal thickness after rotation. For scars that are ° from horizontal, the graft should be rotated 180 – °. By using these calculations, the autograft in this case successfully resolved the diplopia and improved visual acuity.

Conclusions  A rotational autograft can be an effective alternative to standard penetrating keratoplasty for some patients with corneal scars. We establish a mathematical model for most clinical instances of a rotational autograft, in which an 8-mm graft with a decentration of 0.5 mm best satisfies the goals of surgery.

Author Affiliations: Duke University Eye Center, Duke University Medical Center, Durham, NC (Dr Afshari, Mr Duncan, and Ms Tanhehco); and Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston (Dr Azar).

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Size and Location of Corneal Rotational Autografts
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Arch Ophthalmol. 2007;125(7):992.
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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES

Size and Location of Corneal Rotational Autografts
Jonas
Arch Ophthalmol 2007;125:992-992.
FULL TEXT  

Centration of Clear Zone Over the Pupil Is the Best Strategy for Rotational Autografts
Harris
Arch Ophthalmol 2007;125:992-993.
FULL TEXT