ANATOMY OF THE EYE AND PTOSIS
There are two muscles that are responsible for raising or elevating the eyelid—the levator muscle and the Müller’s muscle. The levator muscle is a more superficial muscle and sits above the Müller’s muscle. These two muscles work in concert to lift the eyelid. The levator muscle is controlled by voluntary signaling, whereas the Müller’s muscle is controlled by involuntary signaling.
Patients with severe congenital ptosis have a weakening of both levator and Müller’s muscles; therefore, correction requires tightening of both muscles.
In mild to moderate cases, ptosis surgery can be performed with correction of Müller’s muscle only. In patients with acquired ptosis, correction requires the strengthening of the levator muscle or the Müller’s muscle. In this case, determining which muscle to correct is based on which muscle is dysfunctional.
The traditional method of the surgical correction of ptosis was merely the tightening of the levator muscle. This method was further advanced with the tightening of the levator as well as the Müller’s muscles, providing more efficacy. The latest advancement involves a minimally invasive technique which is done by plicating or resecting the muscle without making an incision on the skin. This method can be performed on patients with borderline to moderate ptosis. Borderline ptosis can be difficult to correct with the traditional open technique, as mild ptosis requires a very fine tightening of the muscle. Non-incisional ptosis correction method can be useful for patients with borderline ptosis. This involves flipping the eyelid and working on the inner, deep aspect of the eyelid. This technique is especially useful when the patient has had prior eyelid surgery and would like to avoid having further incisions. The result is less traumatic to the eyelid tissue since less additional surgical incision is made. It is also helpful in creating the most natural and dynamic double eyelid fold, as the anatomy that is involved in fold formation is not disturbed. An advancement with ptosis correction for severe ptosis involves simultaneously tightening both muscles to provide maximal eyelid functionality and durability to the ptosis repair compared to the prior method. Another advancement with severe ptosis is coupling the eye elevating muscle to the superior rectus muscle. The advantage of this technique, compared to the traditional method of elevating to the forehead, is that the eyelid mechanism is significantly more natural.