Mechanical ectropions may be recognized by accompanying periorbital edema and proptosis, whereas paralytic ectropion is distinguished from other forms by presence of facial nerve palsy-related symptoms such as incomplete ocular closure, epiphora, sagging tissue surrounding the eyelid and impaired mouth control [2]. In virtually all cases, the lower lid is affected [3]. Epiphora may be seen in almost all subtypes, but most frequently suggests either involutional or paralytic forms [9].

A careful physical examination with a particular emphasis on the lower eyelid is usually sufficient for the diagnosis. The position of the eyelid in relation to the eyeball and its tension should be evaluated, most frequently through the snap test [2]. This probe comprises downward pulling of the eyelid and its subsequent release. A pathological result is observed if the eyelid does not return to its normal anatomical position within a few seconds [3]. A full neurological examination that includes facial nerve evaluation is important as well, as Bell's palsy is an important cause of paralytic ectropion [2].

Before deciding on the choice of therapy, it is essential to determine which subtype is present [2], as significant differences exist depending on the underlying cause [10]. Surgery is performed in practically all cases and the goal is to correct instability of the lid through several approaches. Stabilization of both medial and lateral canthal tendons, tarsal strip procedure, shortening of the lid horizontally through plication, reinsertion of the lower lid retractors and skin or palate grafting are all described in literature [2]. A transconjuctival approach that includes plication of the inferior retractor muscles has been described as well [9]. Although surgery has been considered as first-line therapy, non-surgical alternatives such as injection of hyaluronic acid has been proposed as well [4]. The procedure has shown good results and poses no risk compared to surgery [4]. The use of adhesive strips has shown to be a valid temporary solution that can be performed by the patient him/herself [3], until permanent surgery is carried out. For patients in whom drug-induced ectropion is diagnosed, simple discontinuation of the drug may lead to complete resolution [5].

Because eversion of the eyelid results in exposure of the conjunctiva and the cornea [1], patients are at an increased risk ocular inflammatory diseases, but overall prognosis is very good with timely surgery. Although complications such as bleeding, infection, wound dehiscence and poor positioning of the tarsal strip may occur, the benefit of surgery heavily outweighs the risks.

The cause somewhat depends on the subtype. In most cases, congenital forms are associated with some other ocular condition, such as blepharophimosis, ichthyosis, euryblepharon and several other [1]. Each acquired form, on the other hand, possesses a distinct etiologic mechanism. Involutional ectropion stems from age-related laxity of the horizontal lid, together with weakness of the canthal ligaments, whereas cicatricial ectropion develops as a result of scarring and shortening of the anterior lamella, most commonly in the setting of burns, trauma or tumors [1]. Mechanical ectropion is seen in conditions that literally "push" the eyelid outward, such as periocular edema, tumors or spasm of the orbicularis muscle [2]. Paresis of the facial nerve (Bell's palsy) is responsible for paralytic ectropion in virtually all cases. In a small subset of patients, a drug-induced mechanism of development was established [5]. Dorzolamide and brimonidine were identified as potential causative agents, which are thought to induce cicatricial changes in the anterior lamella [5].

Ectropion is considered to be the most frequent form of eyelid malposition [1], but overall prevalence and incidence rates are currently unknown. Certain large-scale studies conducted in the adult population have shown a prevalence rate of 3.9%, with much higher rates observed older individuals, reaching up to 16.7% in individuals older than 80 years [7]. In the same study, a slight gender predilection toward male gender was observed [7]. In terms of risk factors, patient suffering from ichthyosis and erythroderma show significantly higher rates of ectropion compared to the general population, particularly neonates [6]. Several reports have established much higher rates of this eyelid malformation in the Asian population, suggesting that ethnicity is also an important factor [8]. Although the exact correlation between diabetes, hypertension, cerebrovascular disease and ectropion is unknown, their close association has been determined [7].

The pathogenesis model varies across different forms. In the setting of cicatricial ectropion, conditions that reduce skin elasticity and cause shortening the anterior lamella of the lid, such as trauma, burns, allergies and scarring skin tumors, contribute to its development [1]. On the other hand, mechanical ectropion is thought to occur as a result of inflammatory disorders that cause spasm of the orbicularis muscle, or in the presence of an eyelid tumor [1]. Bell's palsy (facial nerve palsy) triggers various lower motor neuron lesions that affect the muscles of the forehead, the orbicularis muscle, but also impaired secretion from the lacrimal gland [2]. Eventually, marked elongation and sagging of the facial tissues, including the eyelid is observed.

As the majority of subtypes are related to causes that cannot be prevented, such as age, bell's palsy and weakening of the anatomical structures that support the eyelid, preventive strategies are currently not possible.

Ectropion is thought to be the most frequent eyelid disorder and results in eversion of either upper, but much more commonly the lower eyelid [1]. Ectropion may appear in congenital and acquired forms. Congenital ectropion is rare and is usually accompanied by additional malformations, such as ptosis, epicanthus inversus and euryblepharon [1], whereas involutional, paralytic, mechanical, and cicatricial subtypes of acquired ectropion have been described in literature [1]:

• Involutional ectropion, considered as the most common type, is caused by age-related laxity of the lid, leading to eversion and exposition of the conjuctiva to the external environment [2].
• Paralytic ectropion is most frequently associated with facial nerve palsy, the end-result being marked elongation of the lid and associated functional problems such as incomplete eye closure and epiphora [2], since the nasolacrimal system is innervated by the facial nerve [3].
• Cicatricial ectropion is thought to occur as a result of shortening of the anterior lamella [4], most frequently in the setting of trauma, burns and possibly skin tumors [1].
• Mechanical ectropion can appear due to various conditions that physically push the eyelid outward, including large tumors, periocular edema, chemosis of the conjuctiva and spasm of orbicularis muscle [1] [2].

In rare cases, ectropion was induced by topical drugs such as dorzolamide (a carbonic anhydrase inhibitor used in the setting of glaucoma) and brimonidine (an alpha 2 adrenergic receptor agonist used for the same indication), inducing similar changes to those seen in cicatricial forms [5]. When describing potential risk factors, it was revealed that patients who suffer from ichthyosis are much more prone to develop ectropion, primarily due to hyperkeratosis of the eyelid and significant drying of the stratum corneum [6]. Asian ethnicity and older age were established as risk factors as well [7], while various conditions, including hypertension, diabetes mellitus and cerebrovascular disease have been correlated with an increased prevalence of ectropion [7]. The clinical presentation may somewhat vary across different subtypes, but usually involves epiphora and incomplete ocular closure [2]. The diagnosis is made by simple physical examination and conduction of probes such as the snap back test, but a full neurological examination is necessary in order to exclude Bell's palsy as a potential cause [2]. Various forms of surgical treatment have been described in literature and the approach significantly depends on the underlying type and cause [8]. Apart from exposure of the conjuctiva to the eternal environment and increased susceptibility to infection, ectropion does not pose a major risk for the patient. Moreover, the prognosis is very good with surgery.

Ectropion is a medical term for outward eversion of the eyelid, most frequently appearing in older individuals and in the Asian population. Ectropion may be either congenital, in which this malformation is seen from birth, whereas several acquired forms (involutional, mechanical, paralytic and cicatricial) have been documented in literature. The cause across various forms stems from reduced stability or integrity of anatomical structures that provide support of the eyelid and many cases have been associated with burns, trauma, underlying tumors and various additional ocular diseases, in addition to older age. Paralytic ectropion is almost always a manifestation of Bell's palsy, or paralysis of the 7th cranial nerve, the facial nerve. Although a clear association has not been made yet, the appearance of ectropion has been correlated with conditions such as diabetes mellitus, hypertension and stroke. Diseases such as ichthyosis and erythroderma have shown to be significant risk factors for ectropion in neonates and children, as these condition significantly alter the structural integrity of the skin, including the eyelids. The clinical presentation depends on the underlying subtype, ranging from abundant production of tears (epiphora), swelling of the eye and the orbit, as well as incomplete closure of the eye. The diagnosis can be made by simple observation during physical examination, whereas a confirmation can be made by performing a "snap-back" test, in which pulling of the eyelid will result in a delayed return to its normal anatomical position. Although ectropion poses minimal risk for the patient, surgery is indicated in order to reduce the chance of conjuctivitis, but also for cosmetic reasons. Depending on the underlying subtype, various surgical approaches have been proposed, but the overall prognosis of patients with ectropion is good with proper surgical management.

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