Tendinous muscle insertions (scleromuscular junctions of the recti muscles) in patients with ocular alignment problems.

BACKGROUND

The purpose of this study was to prove the hypothesis whether the scleromuscular junction of extraocular recti muscle is tendinous.

PATIENTS AND METHODS

Muscle samples of the 41 extraocular recti muscles of 33 patients and 4 muscle-/eye-matched samples from 2 postmortem eyes, were processed for light/electron microscopy and immunohistochemistry with antibodies against desmin, smooth-muscle actin and muscle regulating proteins like myf3 and myf4 (myogenin), tenascin C and for 8 samples against collagens I to IV.

RESULTS

Histological examination of the muscle samples confirmed a thick collagen-structured tissue, specific for muscle tendon; without appearance of muscle tissue. This was confirmed by immunohistochemistry with antibodies against desmin, smooth-muscle actin, myf3 and myf4 (myogenin) and for eight samples with collagens I to IV. Anti-tenascin C marker was only strongly positive in the connective tissue of the blood vessel walls. Electron microscopy demonstrated collagen bundles composed of parallel oriented fibrils with a moderate amount of ground substance.

CONCLUSIONS

The absence of contractile fibers at the sclerotendinous junction is an entirely normal finding in humans and cannot be related to ocular alignment pathogenesis.