Severe eyelid ptosis is a difficult condition to correct. This is because the eyelid elevating muscle (levator palpebrae superioris muscle) is significantly weak. Some of these severe eyelid ptosis patients have either minimal muscle function or no muscle function. Therefore, when there is no muscle function, the typical method of correcting eyelid ptosis (shortening the muscle) does not work. In addition, many patients believe that their eyelid ptosis is due to skin issue and therefore only need double eyelid surgery or blepharoplasty. Performing double eyelid surgery or blepharoplasty on these patients will not improve their condition at all.
In severe eyelid ptosis (severe blepharoptosis), a definitive eyelid ptosis needs to be done. In mild to moderate eyelid ptosis, an internal or non-incision ptosis surgery can be performed. However, in severe eyelid ptosis, a deeper layer known as the conjoint fascial sheath needs to be utilized. This conjoint fascial sheath is also known as intermuscular transverse ligament or check ligament of the superior fornix. This structure is intimately linked to the superior rectus muscle. The advantage of using this structure is that it allows upward eyeball movement to help open eyes. The prior technique of using the forehead muscle led to unnatural eyelid opening and closing. Furthermore, a double eyelid fold or double eyelid crease cannot naturally be created if the forehead muscle is used.
There are several possible mechanisms of effect of the conjoint fascial sheath. One is that it acts as a pulley for the eyelid elevating muscles. Second is that there is a more mechanical advantage when the conjoint fascial sheath is used. The angles of the pull by the levator palpebrae superioris muscle and the superior rectus muscles become more oblique. Therefore, it takes less force to lift the eyelid. The third mechanism is that the nerve that controls eyelid opening and looking upward are supplied by the same cranial nerve 3. Therefore, these muscles work in harmony to open eyes.
Another significant advantage of using conjoint fascial sheath to correct severe eyelid ptosis is that lagophthalmos (inability to close eyes) is decreased. This is due to the elastic property of the conjoint fascial sheath and the downward eyeball movement when one closes one’s eyes.
And another aesthetic advantage is that natural appearing double eyelid fold or supratarsal crease can be created compared to using the frontalis muscle.