COMPUTER-ASSISTED PLANNING OF SQUINT SURG ERY

Background Two different program systems can be used when planning squ int surgery. In the first system's algorithms (Robinson-Miller-Simonsz ) are modelled the mechanical and innervational laws that govern eye m ovements (ophthalmotrope program). With ocular deviations and surgical procedures as input the program estimates postoperative deviations. T he second program (Russmann-Konen) mimics any surgeon's planning of sq uint surgery using a defined decision tree and an appropriate number o f mm-degree-relations (planning program). If ocular deviations, axial length, monocular excursions, and head posture are input the program p roposes a surgical procedure. I combined both programs to enable the o phthalmotrope program to evaluate the propositions of the planning pro gram. Material and Methods I translated Simonsz' version 1/1989 of Rob inson's program from FORTRAN to the programming language of my plannin g program (Turbo BASIC for IBM-PC) and connected both, the former beco ming a module of the latter. Thus data entered into the planning progr am as well as the surgical procedure proposed may be immediately proce ssed by the ophthalmotrope program to compute the presumed postoperati ve result. Several program loops allow a wide variation of data and pr ocedures in successive program runs. Turbo BASIC being somewhat slower than FORTRAN quick computers (INTEL 80486, Pentium) are necessary les t processing lasts more than 1 minute. Results A concomitant esotropia of 20 degrees and a head posture with elevation of the chin of 20 deg rees are used to illustrate program properties. In the first case the planning program proposes a reasonable recess-resect-procedure 6 mm ea ch, which is estimated to give a very slight overcorrection by the oph thalmotrope module. In the second case the planning module proposes a gaze shift procedure (Kestenbaum) on the vertical recti, which - in go od agreement with my own experience - is estimated to produce an A-phe nomenon of 19 degrees with an incyclotropia up to 30 degrees by the op hthalmotrope module. If an anterior margin recession of the superior o blique and an anterior margin tuck of the inferior oblique are added t o the gaze shift procedure in both eyes neither any phenomenon nor any significant deviation are predicted by the ophthalmotrope module. Con clusions The combination of a planning module with an ophthalmotrope m odule in one program considerably enhances the usefulness of both.