Diagnosis and surgical management of isolated inferior oblique palsy

Isolated inferior oblique pareses

PURPOSE

To describe etiology, clinical characteristics, radiological features and management of isolated inferior oblique pareses.

METHODS

A diagnosis of inferior oblique paresis was made after a thorough strabismus examination and neuroimaging. The patients were managed surgically with adjustable strabismus surgery, or conservatively. Surgical success was defined as average horizontal deviation within ≤ 10 prism diopters [PD] post-operatively and for vertical deviation, it was ≤ 5 PD, at last follow-up.

RESULTS

Seven cases were congenital, 6 cases were bilateral, with esotropia in 6 cases; 'A' pattern in 7 cases and hypotropia in 3 cases. The mean preoperative horizontal deviation was 52.5 PD, and the mean postoperative horizontal deviation was 2.37 PD (p = 0.028). The pre-operative vertical deviation was 18 PD and post-operative vertical deviation was 5 PD. MRI showed reduced IO muscle size; average area being 11.27 mm² in the affected eyes, with normal sized inferior recti (average: 24.63 mm²) and medial recti muscles (average: 30.08 mm²). Surgical success was seen in all six cases. Average follow-up was 265 days. The Parks' three step test was not valid, except for one acquired unilateral case.

CONCLUSION

Isolated pareses of inferior oblique muscle exhibit defective elevation in adduction of the affected eye, 'A' pattern and fundus intorsion, and is confirmed by neuroimaging. These can be successfully managed surgically to correct the deviation.

Congenital dysplasia involving both medial and inferior recti: clinical features and surgical outcomes

AIM

To investigate the clinical features and surgical outcomes of congenital dysplasia involving both inferior recti (IR) and medial recti (MR) muscles.

METHODS

A retrospective review was conducted including cases of simultaneous congenital dysplasia of IR and MR that were diagnosed and surgically treated at the Zhongshan Ophthalmic Center, Sun Yat-sen University, China, from July 2009 to November 2019. Ocular motility, ocular alignment at distance (6 m) and near (33 cm) by prism alternating cover test and stereoacuity were assessed in all patients before and after surgery.

RESULTS

A total of five patients (four males and one female; three with right eye and two with left eye congenital dysplasia) were included in this review. The patients ranged in age from 10 to 42y (21±13.4y). The main clinical findings were hypertropia and exotropia of the affected eye, along with motility limitations in adduction and depression. Lateral rectus (LR) recession/transposition combined with IR resection was performed in one case. Two scheduled surgeries were performed in four cases, with one involving superior rectus recession and IR resection and the others LR recession and MR resection. Mean±SD pre-surgical exotropia of 51.0±31.11 prism diopter (PD) and hypertropia of 29.20±7.12 PD in the primary position were decreased to 3.6±12.90 and 3.2±10.09 PD, respectively, at two years after surgery, with a success rate of 60% and an under-correction rate of 40%.

CONCLUSION

The main clinical features associated with simultaneous MR/IR congenital dysplasia are hypertropia and exotropia of the affected eye along with motility limitations in adduction and depression. Scheduled two-stage surgeries achieved a success rate of 60%.

The oblique extraocular muscles in cetaceans: Overall architecture and accessory insertions

The oblique extraocular muscles (EOMs) were dissected in 19 cetacean species and 10 non-cetacean mammalian species. Both superior oblique (SO) and inferior oblique (IO) muscles in cetaceans are well developed in comparison to out-groups and have unique anatomical features likely related to cetacean orbital configurations, swimming mechanics, and visual behaviors. Cetacean oblique muscles originate at skeletal locations typical for mammals: SO, from a common tendinous cone surrounding the optic nerve and from the medially adjacent bone surface at the orbital apex; IO, from the maxilla adjacent to lacrimal and frontal bones. However, because of the unusual orbital geometry in cetaceans, the paths and relations of SO and IO running toward their insertions onto the temporal ocular sclera are more elaborate than in humans and most other mammals. The proximal part of the SO extends from its origin at the apex along the dorsomedial aspect of the orbital contents to a strong fascial connection proximal to the preorbital process of the frontal bone, likely the cetacean homolog of the typical mammalian trochlea. However, the SO does not turn at this connection but continues onward, still a fleshy cylinder, until turning sharply as it passes through the external circular muscle (ECM) and parts of the palpebral belly of the superior rectus muscle. Upon departing this "functional trochlea" the SO forms a primary scleral insertion and multiple accessory insertions (AIs) onto adjacent EOM tendons and fascial structures. The primary SO scleral insertions are broad and muscular in most cetacean species examined, while in the mysticete minke whale (Balaenoptera acutorostrata) and fin whale (Balaenoptera physalus) the muscular SO bellies transition into broad fibrous tendons of insertion. The IO in cetaceans originates from an elongated fleshy attachment oriented laterally on the maxilla and continues laterally as a tubular belly before turning caudally at a sharp bend where it is constrained by the ECM and parts of the inferior rectus which form a functional trochlea as with the SO. The IO continues to a fleshy primary insertion on the temporal sclera but, as with SO, also has multiple AIs onto adjacent rectus tendons and connective tissue. The multiple IO insertions were particularly well developed in pygmy sperm whale (Kogia breviceps), minke whale and fin whale. AIs of both SO and IO muscles onto multiple structures as seen in cetaceans have been described in humans and domesticated mammals. The AIs of oblique EOMs seen in all these groups, as well as the unique "functional trochleae" of cetacean SO and IO seem likely to function in constraining the lines of action at the primary scleral insertions of the oblique muscles. The gimble-like sling formed by SO and IO in cetaceans suggest that the "primary" actions of the cetacean oblique EOMs are not only to produce ocular counter-rotations during up-down pitch movements of the head during swimming but also to rotate the plane containing the functional origins of the rectus muscles during other gaze changes.