Involutional entropion is an age-related medical condition where the lower eyelid margin turns inward, causing eyelashes to rub against the eye’s surface. This condition is most frequent in older adults, with a prevalence of 2.1% in individuals over age 60. The constant friction is a source of discomfort and can lead to serious complications if not addressed.
Underlying Causes of Eyelid Inversion
A primary factor is horizontal lid laxity, where the eyelid loses its tautness due to the stretching of the medial and lateral canthal tendons. These tendons anchor the eyelid to the bony orbit. Without this firm support, the eyelid becomes unstable, which is a significant contributor to the inward rotation of the lid margin.
Another cause is the weakening or detachment of the lower eyelid retractors. These small muscles are responsible for pulling the lower eyelid down and keeping it properly positioned. When these retractors disinsert or lose tension, the lower edge of the eyelid’s internal plate, the tarsus, can rotate, allowing the upper margin to turn inward.
The orbicularis oculi, the muscle that closes the eyelid, also plays a role. The preseptal portion of this muscle can move upward and override the pretarsal portion during blinking. This action pushes the eyelid margin inward, exacerbating the inversion caused by other structural weaknesses.
Associated Symptoms and Complications
The symptoms of involutional entropion result from the abrasion of eyelashes and skin against the cornea. Patients experience a persistent foreign body sensation, feeling as though something is in their eye. This irritation leads to eye pain, redness, itching, and discomfort.
Excessive tearing, or epiphora, is another frequent symptom, as the constant irritation stimulates the lacrimal gland to produce more tears. This can be accompanied by a mucous discharge, crusting along the eyelids, and a heightened sensitivity to light and wind.
If left untreated, the continuous rubbing can lead to serious complications. The cornea’s protective outer layer can become eroded, creating a painful corneal abrasion. These abrasions make the eye vulnerable to infection, which can result in a corneal ulcer, scarring, and potential vision loss.
The Diagnostic Examination
An ophthalmologist diagnoses involutional entropion during a clinical eye examination, often using a slit-lamp for a magnified view. The physician inspects the eyelids and their position, confirming the margin is turned inward and checking for irritation on the ocular surface.
To assess underlying causes, the doctor performs several tests. The lid distraction test involves pulling the lower eyelid away from the eyeball; pulling it more than 8 millimeters indicates significant horizontal laxity. The snapback test observes how long the lid takes to return to its position after being pulled down, as a slow return suggests poor tendon and muscle tone.
The physician also evaluates the function of the lower lid retractors by observing the eyelid’s movement as the patient looks down. Diminished excursion can point to retractor weakness or disinsertion. A visible white line through the conjunctiva on the inside of the eyelid may represent a complete detachment of the retractors.
Surgical and Non-Surgical Treatments
Management ranges from temporary measures to definitive surgical correction. Non-surgical options provide temporary relief or are for patients unsuitable for surgery. These include:
- Frequent use of artificial tears and lubricating ointments to protect the ocular surface.
- Taping the lower eyelid to the cheek to hold it in an everted position.
- Placing a bandage contact lens on the eye to act as a shield from abrasive lashes.
- Injecting botulinum toxin into the orbicularis oculi muscle to prevent the overriding action that contributes to inversion.
The definitive treatment is surgery to correct the anatomical defects, performed on an outpatient basis under local anesthesia. The specific technique used depends on the primary cause but aims to tighten the eyelid and re-establish its proper rotational position.
Common surgical approaches include the lateral tarsal strip procedure, which tightens the eyelid by shortening and reattaching the lateral canthal tendon. To address retractor disinsertion, a surgeon performs a retractor reinsertion to reattach the weakened muscles. These procedures stabilize the eyelid and provide a long-term resolution.