Navigating, Measuring, and Evaluating Ocular Ptosis

Patients presenting with ptosis with or without additional ocular complications can offer a challenge to the optometric physician due to its potential urgency and variables leading to proper diagnosis, treatment, and management (such challenges include underlying etiologies ranging from neurological to mechanical and treatments ranging from eye drops to surgical interventions). This article details a clinical approach to examining patients with ptosis.

EXAMINING THE PTOTIC PATIENT

Choosing the appropriate method by which to measure ptosis depends on whether the ptosis is unilateral or bilateral. Normal upper eyelid positioning rests approximately 2 mm below the superior limbus. For all measurements, the brow must be in a relaxed position in order to avoid contribution from the frontalis muscle.

For unilateral ptosis, the measurement should come from the distance between the upper and lower eyelids; in a normal eye, this aperture is approximately 10 mm. For bilateral ptosis, the measurement should come from the distance between the central corneal light reflex to the upper eyelid, known as marginal reflex distance-1. Its normal values are approximately 4 mm to 4.5 mm.¹

To measure and evaluate levator function, place your hand on the patient’s forehead to avoid frontalis contribution. Have the patient look down, and mark their upper eyelid location with your ruler. Then have them look as far up as possible, measuring the distance between the upper eyelid positioning in downgaze and upgaze. The normative values and categorizations are:²

• Excellent: 13 mm to 15 mm
• Very Good: 10 mm to 13 mm
• Good: 8 mm to 10 mm
• Fair: 5 mm to 7 mm
• Poor: < 4 mm

In addition to obtaining a thorough case history and the ptosis measurements described above, the physical evaluation should also include pupillary appearance, function, and ocular motility.

THE PHYSICAL EVALUATION

For general purposes, ptosis can be placed into one of two categories: congenital or acquired.

Congenital Ptosis

Congenital ptosis is the most common form of this condition seen in childhood. This form of ptosis is secondary to a developmental dystrophy of the levator muscle, which results in about 75% of cases being idiopathic.³ This ptosis can also run in families because there can be a genetic component.

When congenital ptosis is suspected, visual acuity will help rule out any deprivational amblyopia secondary to obscuration of the visual axis. This only occurs in approximately 3% of all congenital cases.³ Strabismus is also a concomitant finding in approximately 31% of cases.³

An evaluation of pupil size and color is needed to rule out Horner syndrome. It is important to note that in Horner syndrome present before age 2, the iris of the affected eye may be lighter in color than that of the unaffected eye. The patient may present with eyelid elevation or their head in a chin-up position to alleviate any visual obscuration caused by the ptosis. Additionally, it is important to perform palpation of the eyelid and orbital rim to rule out a lid mass, which can cause ptosis by the extra weight added to the eyelid.

A unique congenital presentation to note is Marcus Gunn Jaw Winking ptosis, which is caused by synkinesis in which when the mouth opens, the eyelid retracts, and the mandible moves to the side opposite of the involved lid.

Other differentials to be considered, but that are not within the capacity of this article, include periorbital tumors, such as plexiform neuroma, lymphoma, leukemia, rhabdomyosarcoma, neuroma, neurofibroma, or other deep orbital tumors, in addition to Kearns-Sayre syndrome.

Acquired Ptosis

The main contributors of acquired ptosis are involutional and neurogenic ptosis.⁴

Involutional Ptosis

Involutional, or aponeurogenic, ptosis is the most common type of acquired ptosis and is caused by disadhesence of the levator aponeurosis, where the levator becomes overstretched. Its characteristic features include droopy eyelids, good levator function, higher eyelid crease, and worsening of ptosis on downgaze.⁵ The likely causes are secondary to aging and excessive eyelid rubbing or pulling.⁵ Both soft and hard contact lens wear is also thought to contribute to disadhesence.⁶

Neurogenic Ptosis

Neurogenic ptosis occurs when there is a problem with the nerve pathway that controls the eyelid muscle. It typically accompanies additional ocular and possible systemic complications. The main causes of neurogenic ptosis are myasthenia gravis, third nerve palsy, and Horner syndrome.⁷

Myasthenia gravis is a condition characterized by unresponsiveness to released acetylcholine secondary to a defect at the neuromuscular junction. Common patient complaints that can lead to myasthenia include variable ptosis, decreased orbicularis function, and diplopia with or without ptosis.⁸ The ptosis is secondary to an implication of the levator muscle and can be unilateral or bilateral; if presenting bilaterally, it will most often be asymmetric.⁸

When ptosis is present, the fellow eyelid may be more retracted due to Hering’s law of equal innervation. If the ptotic eyelid is manually raised and the fellow retracted eyelid droops, this is called enhanced ptosis and is specific toward ocular myasthenia gravis.⁸ A way to increase suspicion of ocular myasthenia gravis is to test lid fatigability. Optometrists can do this by having the patient look upward; if the presenting ptosis increases after prolonged upgaze, then the test is positive.

Additionally, the patient may present with decreased orbicularis function. To test this, have your patient squeeze their eyes closed and then try to open their eyelids manually with your fingers. A weakened orbicularis will offer little resistance to eyelid separation. Lagophthalmos with lid closure indicates orbicularis weakness known as the “peek a boo” sign.

In a diplopic patient with variable incomitant strabismus with or without ptosis, ocular myasthenia gravis should be highly considered.⁸

Ptosis associated with a suspected third nerve palsy can be worrisome because a space-occupying lesion must be ruled out. There are two types of third nerve palsies. The first is complete, in which there is a full ptosis. The affected eye presents down and out, there is a dilated pupil with sluggish to minimal response, and the eye cannot elevate, depress, or abduct. The fellow eye is partial, in which there will be variable ptotic presentations, variable pupil involvement, and variable duction limitations.⁹ A majority of third cranial nerve palsies without pupillary involvement are secondary to ischemic processes. These patients typically observe improvement after 1 month and full resolution within 3 months of onset.⁹ A pupil-involved third nerve palsy is likely secondary to a compressive process. If a longstanding third nerve palsy is suspected, the pupil will be paradoxically small and minimally reactive to light.⁹

When suspecting Horner syndrome, expect the triad of ptosis, ipsilateral miosis, and ipsilateral anhidrosis. Ptosis tends to be slight, as the underlying cause is secondary to an interruption of sympathetic innervation to Müller muscle. Additionally, a lack of sympathetic innervation to melanocytes can cause ipsilateral heterochromia.¹⁰

Grave disease is an autoimmune condition caused by hyperthyroidism. Thyroid eye disease is a result of this thyroid dysfunction. Patients with thyroid eye disease may possess a variety of ocular symptoms secondary to an overactive thyroid, such as eyelid retraction due to sympathetic hyperactivity of Müller muscle.¹¹ Eyelid retraction that is unilateral can give off the appearance of ptosis in the unaffected eye. Fortunately, an understanding of the anatomy and innervation of the eyelids can help spot this mimicker.

TREATMENT OPTIONS

The levator function, severity, and underlying etiology will aid in determining the best treatment and management approach. Although levator enhancement is the most commonly performed surgical procedure to treat ptosis, other surgical approaches include, but are not limited to, frontalis suspension and Müller muscle conjunctival resection.⁴

There are also observational or pharmaceutical approaches to consider that may be more appropriate for treatment or management. There are three main pharmaceutical approaches for the treatment or management of ptosis. These include botulinum toxin injections, apraclonidine drops, or oxymetazoline HCl 0.1% (Upneeq, RVL Pharmaceuticals). Botulinum toxin injections into the pretarsal orbicularis oculi muscle tend to be indicated for mild ptosis and small eyelid asymmetries.¹² Apraclonidine drops are typically not considered, due to their sensitivity to long-term administration. Oxymetazoline is an alpha 1 and partial alpha 2 adrenergic agonist. This compound, when administered as a topical eye drop, contracts Müller muscle, providing approximately 1 mm of eyelid lift for about 6 hours.

SKILLS AND KNOWLEDGE GO A LONG WAY

Given its structural, functional, and cosmetic roles, the eyelid and its positioning play dynamic roles in both vision and ocular health. Therefore, approaching ptosis with confidence plays an important role in complete eye care. Knowledge and strong evaluation skills can arm the optometrist to make a proper ptosis assessment and to proceed with appropriate management, including treatment, monitoring, or referral.