a 51-year old man presented to our hospital suffering from vertical and torsional diplopia after reduction of a blowout fracture at another hospital one year ago . the man described seeing double images separated vertically , and the right image was slightly slanted toward his nose . no head position abnormalities or facial asymmetry were noted . a thin - section coronal ct scan revealed multiple fractures in the right facial bone , including the orbital floor , medial wall , and zygomatic arch , and also a metallic screw fixed to the inferior orbital walls . we detected no fracture line on the anterior orbital floor , but we did note that a fracture remained on the posterior orbital floor ( fig . also , the portion of the right inferior oblique muscle in front of the equator was vertically reoriented . the medial portion of the inferior oblique muscle was not traced on a coronal ct scan ( fig . the alternate prism cover test indicated a 14pd right hypertropia ( rht ) , 4pd esophoria ( e ) in the primary gaze , 18pd rht , 4pd e in levoversion with the head turned to the right , and 6pd rht , 4pd e in dextroversion , with the head turned to the left . the patient was orthophoric in upgaze , and 35pd rht , 10pd e in downgaze . the bielschowsky head tilt test generated a negative response , and we recorded an 8pd rht on tilting the head to the right shoulder , and 6pd rht on tilting the head to the left shoulder . underaction of the right inferior rectus ( rir ) and right superior oblique ( rso ) muscles associated with downgaze limitations were evident , but io overaction of the right eye was determined to be minimal . we noted no overaction or limitation of the right superior rectus ( rsr ) or contralateral io ( fig . the patient 's binocular single visual field was limited in the right superior temporal quadrant ( fig . the double maddox rod test ( dmrt ) revealed a10-degree extorsion in the right eye . foveal extorsion was also found to be minimal in the right eye . under general anesthesia , results of the ntraoperative forced duction test were not remarkable , and only a mild loosening of the rir was noted . the technique for the 14 mm recession of the io was as described by parks.5 the rir resection was also performed because the approach to the ir was relatively easy , following the io recession in the forniceal incision , and because the anterior portions of the ir might have been relatively paretic , as was mentioned previously.3 two weeks after the surgery , 4pd esophoria only was noted in the patient 's primary gaze . 2b ) and the patient 's field of single binocular vision was expanded in the primary gaze and in the downgaze . first , the increased angle of contact of the ir is attributable to an inferior looping of the muscle itself . the second mechanism relevant to hypertropia is a relative anchorage of the muscle to the fracture , resulting in a faden - like effect . these effects create a relative ir paresis , and cause the sr of its antagonist to generate hypertropia . our patient exhibited none of the restrictions or overactions of the rsr and contralateral lio which had been exhibited in the preoperative version and binocular single visual field tests . also , they noted that the tethering of io , as proposed by nardi,4 should induce torsional diplopia , but this did not occur in any of their patients . in cases involving ir paresis after a posterior blowout fracture , fundus intorsion is normally evident , because the ir is an extorter.6 however , manifested extorsions such as those described in our study , might be quite exceptional , and might be explained by co - existent so palsy.7 our patient manifested no ocular torticollis , had a negative response on a bielschowsky head tilt test , and exhibited no rso loosening on the intraoperative forced duction test , all of which are telltale signs of so palsy.8,9 however , true so palsy could not be excluded , as it does not necessarily require toricollis to be present and although mild , there is in fact a difference in right hypertropia on head tilt . moreover , a slack so tendon would be expected only if the palsy was congenital , not acquired.10 therefore , we believe that the fixed io in the floor fracture might disturb the manifestation of co - existent so palsy , as evidenced by the observations of anomalous head posture for fusion , distinct io overaction , and the positive bielschowsky head tilt test . we assume that the torsional symptoms manifested by our patient might be attributable to so paresis combined with entrapment of a portion of the anterior torsional fiber of the rio into the fracture site . we also believe that the so paresis observed in our patient might indicate true palsy , as the torsional diplopia was so severe . in conclusion , nardi 's hypothesis for the major role of io in hypertropia following blowout fractures might not have been confirmed by our case . if the connective tissue of the io muscle or muscle itself has become entrapped in the orbital floor , the involved eye would be unable to be lowered due to the restriction of the so on downgaze , and definitive iooa would not be noted . we suggest that the entrapment of the io in the orbital floor following a blowout fracture may alter the manner in which so palsy manifests or may induce a restrictive so paresis .
a 51-year old man presented with vertical and torsional diplopia after reduction of a blowout fracture at another hospital one year ago . 
 he had no anormalies of head position and 14 prism diopters ( pd ) right hypertropia ( rht ) in the primary position . 
 in upgaze no vertical deviation was found , and hyperdeviation on downgaze was 35pd . 
 bielschowsky head tilt test showed a negative response . 
 distinct superior oblique ( so ) and inferior rectus ( ir ) underaction of the right eye was noted but io overaction was mild on the ocular version test . 
 double maddox rod test ( dmrt ) revealed 10-degree extorsion , but fundus extorsion was minimal in the right eye.thin-section coronal ct scan showed that there was no fracture line on the anterior orbital floor , but a fracture remained on the posterior orbital floor . 
 also , the anterior part of the right inferior oblique muscle was vertically reoriented and the medial portion of the inferior oblique muscle was not traced on the coronal ct scan . 
 the patient underwent 14 mm right io recession and 3 mm right ir resection . 
 one month after the surgery , his vertical and torsional diplopia were eliminated in the primary position .