Controversies in Treatment
There are a number of unique clinical scenarios for which treatment is controversial. Two such scenarios are described below.
Unilateral ptosis with poor levator function:
Unilateral sling: Recruiting the ipsilateral frontalis muscle using a unilateral frontalis sling is an option for unilateral ptosis and poor levator function. This is an attractive option because it does not rely on the poorly functioning levator and because it does not require surgery on the unaffected eyelid. One of the concerns with a unilateral sling is asymmetry between the lids especially on downgaze, with pronounced lagophthalmos on the operative side. Another concern is whether patients will have spontaneous unilateral frontalis action to utilize the sling. This may not be a problem for non-amblyopic patients, but patients who are amblyopic on the operative side or have a fixation preference may have variable success with the unilateral sling (Kersten 2005).
Bilateral sling with unilateral disinsertion of levator: To overcome the potential asymmetry associated with a unilateral sling, Beard proposed disinserting the levator on the unaffected side (causing an iatrogenic severe ptosis) and performing a bilateral frontalis sling (Beard 1965). This, he found, results in a better cosmetic appearance and prevents the asymmetric lagophthalmos associated with the unilateral sling. The disadvantage of this procedure is the need to make a previously normal eyelid abnormal and subjecting the unaffected eyelid (and globe) to the standard risks of surgery. This may make the Beard procedure less appealing to parents of patients.
Bilateral sling without disinsertion of levator: In this modification of the classic Beard technique (sometimes called the Chicken Beard technique), a bilateral frontalis sling procedure is performed, but the unaffected levator is not disinserted. This has the advantage of maintaining better symmetry in downgaze than a unilateral sling, and does not require destruction of the normal levator. This may theoretically be more acceptable to parents of patients, as it does not disturb the integrity of the non-ptotic eyelid.
Super-maximal levator advancement: Some advocate a super-maximal (greater than 30 mm) resection of the levator muscle in these cases. While this approach can result in a better cosmetic outcome than a unilateral sling, problems such as conjunctival prolapse and significant lagophthalmos have been reported (Epstein 1984).
Whitnall's sling: An alternative to the super-maximal levator advancement is the Whitnall's sling in which the levator aponeurosis is removed and Whitnall's ligament and levator muscle are advanced to the superior aspect of the tarsal plate. This, too, can provide a better cosmetic result than a unilateral sling, and by keeping Whitnall's ligament intact, it has the added advantage of maintaining support of the lacrimal gland and temporal eyelid. Like the super-maximal resection, lagophthalmos and corneal exposure can occur after the Whitnall's sling procedure as well (Anderson 1990).
Marcus-Gunn Jaw Winking:
These cases represent a special type of unilateral ptosis in which treatment is based on both the amount of ptosis and the severity of the wink. If the wink is mild (i.e. if the lid height variation is minimal with jaw movement) and the ptosis is significant, the ptosis is corrected unilaterally, usually by advancing the levator. If, however, the wink is moderate to severe, the levator may have to be extirpated to eliminate the wink completely. The surgical options then are similar to those for unilateral ptosis with poor levator function discussed earlier (specificially, unilateral sling, bilateral levator extirpation with bilateral sling, or bilateral sling with preservation of the sound levator).