Upgaze eyelid position allows differentiation between congenital and aponeurotic blepharoptosis according to the neurophysiology of eyelid retraction.

To differentiate between congenital and aponeurotic blepharoptosis, we investigated whether upgaze with stretching of the mechanoreceptor of Mueller muscle increases involuntary reflex contraction of the levator slow-twitch muscle fibers. In 50 cases each of unilateral congenital blepharoptosis and of asymmetric aponeurotic blepharoptosis, the mean increases by upgaze in the upper eyelid margin to the line between the medial and lateral canthi as upper eyelid retraction distance (UERD) of the ptotic eyelid 0.4 mm and 2.9 mm, respectively. These were significantly smaller and significantly larger than those of the corresponding nonptotic eyelid, 2.0 mm and 2.3 mm, respectively.Worsening of ptosis on upgaze is common in congenital ptosis and is an abnormal differentiating sign, lacking the involuntary reflex contraction. Improvement of ptosis on upgaze is common in aponeurotic blepharoptosis and likely represents a normal physiological process, restoring the involuntary reflex contraction.

Pathogenesis and surgical correction of involuntary contraction of the occipitofrontalis muscle that causes forehead wrinkles.

Assuming that an agonistic function is present to maintain an adequate visual field, we hypothesized that stretching of the mechanoreceptor of Mueller muscle induces involuntary contraction of the occipitofrontalis muscle, as well as the levator muscles. In patients with aponeurotic blepharoptosis, both unilateral instillation of phenylephrine to contact Mueller smooth muscle fibers and unilateral aponeurotic fixation ipsilaterally reduced the eyebrow height during primary and upward gazing. Bilateral aponeurotic fixation bilaterally reduced the eyebrow height, with fewer forehead wrinkles. Stretching of the mechanoreceptor of Mueller muscle induces involuntary contraction of the bilateral levator muscles. Its increased stretching may induce involuntary contraction of the ipsilateral occipitofrontalis muscle via the mesencephalic trigeminal nucleus and the facial subnucleus as another stretch reflex. The involuntary contraction of the occipitofrontalis muscle that causes forehead wrinkles during primary gazing can be corrected by the aponeurotic fixation to reduce the stretching of Mueller muscle.

Pathogenesis and surgical correction of dynamic lower scleral show as a sign of disinsertion of the levator aponeurosis from the tarsus.

The purpose of this study was to confirm whether lower scleral show is caused by the disinsertion of the levator aponeurosis from the tarsus. Aponeurotic advancement by vascular clips or by surgery involving the orbital septum significantly lowered the global position in the orbit and significantly diminished the degree of retraction of the lower eyelid, resulting in satisfactory improvement of lower scleral show in 100 patients with various aponeurotic blepharoptosis. Therefore, we propose the pathogenesis of lower scleral show as follows: additional contraction of the levator muscle to compensate for the disinsertion of the levator aponeurosis from the tarsus for maintenance of an adequate visual field is accompanied by additional contraction of the superior rectus muscle through the strong intermuscular fascia, resulting in upward rotation of the globe. To maintain the horizontal visual axis and foveation without inclination of the head in the primary gaze position, additional contraction of the inferior rectus muscle is induced, which pulls upon the inferior suspensory ligament of Lockwood and the capsulopalpebral fascia. The former displaces the globe upwards and the latter retracts the lower eyelid, resulting in dynamic lower scleral show as a sign of disinsertion of the levator aponeurosis from the tarsus, which can be surgically corrected.

Efferent and afferent innervations of Mueller's muscle related to involuntary contraction of the levator muscle: important for avoiding injury during eyelid surgery.

Because stretching of Mueller's muscle induces involuntary contraction of the levator muscle, we hypothesised that Mueller's muscle functions as a serial kind of muscle spindle of the levator muscle. To confirm the presence and location of efferent and afferent innervations of Mueller's muscle, cadavers' eyelids were microscopically and macroscopically examined, and the resultant findings were physiologically confirmed in patients' eyelids during surgery. Fine neural myelinated structures acting as a mechanoreceptor were found in the proximal Mueller's muscle. Mueller's muscle is doubly innervated by the unmyelinated sympathetic efferent nerve and the myelinated trigeminal proprioceptive afferent nerve, both of which run transversely on the proximal Mueller's muscle to join the lacrimal nerve. Electrical stimulation of the transverse nerve fibres induced involuntary contraction of both the levator muscle as the Hoffmann reflex and Mueller's muscle. Surgical injury to these nerve fibres should be avoided to preserve involuntary contraction of the levator muscle.