5. DISCUSIÓN
5.3. Interacciones miARNs-ARNm conservadas en cáncer
Ptosis
Definition
Drooping of the upper eyelid(s).
Etiology
Aponeurotic (Involutional)
Disinsertion, central dehiscence, or attenuation of the levator aponeurosis causing lowering of the upper eyelid. Most common form of ptosis, often associated with advanced age, eye surgery, ocular trauma, pregnancy, chronic eyelid swelling, and blepharochalasis; good levator function.
Mechanical
Poor upper eyelid elevation due to mass effect of tumors, or to tethering of the eyelid by scarring (cicatricial ptosis); good levator function.
Myogenic
Inherent weakness of levator palpebrae superioris due to muscular disorders including chronic progressive external ophthalmoplegia, myotonic dystrophy, and oculopharyngeal dystrophy; extremely poor levator function.
FIGURE 3-18 Significant acquired ptosis of the left eye. Most commonly caused by levator aponeurosis
attenuation or dehiscence.
Neurogenic
Defects in innervation to cranial nerve III (oculomotor palsy) or sympathetic input to Müller’s muscle (Horner’s syndrome) or generalized dysfunction of neuromuscular junction such as myasthenia gravis; variable levator function depending on etiology.
FIGURE 3-19 Bilateral acquired ptosis due to myasthenia gravis.
Congenital
Poor levator function from birth; usually unilateral, nonhereditary, and myogenic with fibrosis and fat infiltration of levator muscle; rarely results from aponeurosis dehiscence (possibly birth trauma), in which case good levator function would be expected.
Congenital Horner’s syndrome (ptosis, miosis, anhidrosis, iris hypopigmentation) with poor Müller’s muscle function from decreased sympathetic tone, or congenital
neurogenic with Marcus Gunn jaw-winking syndrome from aberrant connections between cranial nerve V (innervating the pterygoid muscles) and the levator muscle.
FIGURE 3-20 Congenital ptosis of the right eye in a child.
FIGURE 3-21 Same patient as Figure 3-20, demonstrating poor levator function with upgaze of the right eye. Note reduced levator excursion.
Symptoms
Superior visual field defect, brow ache, loss of depth perception; may have decreased
vision (congenital cases with deprivation amblyopia).
Signs
Drooping of upper eyelid(s) with impaired elevation on upgaze, recruitment of brow muscles with brow furrows, higher lid crease and apparently smaller eye on ptotic side, abnormally high contralateral eyelid (Hering’s law); in downgaze, affected lid may be higher than contralateral lid in congenital ptosis (lid lag) and lower in acquired cases;
may have decreased visual acuity when visual axis obscured or head tilt with chin-up position when bilateral; other associated abnormalities in congenital ptosis include lagophthalmos, decreased superior rectus function, high astigmatism, anisometropia, strabismus, amblyopia, epicanthus, and blepharophimosis.
Differential Diagnosis
Dermatochalasis (excess skin of upper eyelids, pseudoptosis), lid swelling, lid tumor, enophthalmos (e.g., orbital floor fracture), hypotropia, contralateral eyelid retraction or proptosis (e.g., thyroid-related ophthalmopathy), and small eye (phthisis bulbi,
microphthalmia, anophthalmia).
Evaluation
• Complete ophthalmic history with attention to age of onset, previous surgeries or trauma, degree of functional impairment and time of day when worst, associated symptoms such as generalized fatigue, breathing problems, diplopia.
• Complete eye exam with attention to amblyopia in children, visual acuity, pupils, motility, Bell’s phenomenon, lids, corneal sensation, and cornea.
• Eyelid measurements: margin reflex distance (MRD, distance between upper eyelid margin and corneal light reflex – normal is 4.5 mm), palpebral fissure height, upper lid crease height (high in aponeurotic), and levator function (LF; distance the upper lid
margin travels between downgaze and upgaze – normal is greater than 11 mm; normal in aponeurotic, decreased in congenital).
• Consider neurologic evaluation with edrophonium chloride (Tensilon) test to rule out myasthenia gravis.
• Consider phenylephrine 2.5% to stimulate Müller’s muscle and rule out Horner’s syndrome; may also use topical cocaine 4–10% or hydroxyamphetamine 1% or both.
• Check visual field test with and without upper lids being held up by tape or finger (ptosis visual fields) to document visual impairment prior to surgery.
• External photos to document lid appearance prior to surgery.
Management
• Ptosis is treated with surgery:
Good levator function: Levator aponeurosis advancement, levator resection, muellerectomy, Fasanella–Servat tarsoconjunctival resection.
Poor levator function (< 6 mm): Frontalis suspension with silicone rods, polytetrafluoroethylene sling, fascia lata, or frontalis flap. Maximal levator resection may be useful in some cases.
Horner’s syndrome or mild ptosis with good levator function: Superior tarsal (Müller’s muscle) resection.
• Surgery for aponeurotic ptosis is performed in an awake, mildly sedated patient with intraoperative adjustment. Surgery for mechanical ptosis involves removal of any mechanical elements (i.e., excision of tumors or removal of tethering adhesions) followed by levator adjustment as needed.
Surgery for congenital ptosis depends on the levator function: with normal levator function, a levator advancement works well but still has variability because many patients are children who require general anesthesia, which prevents intraoperative fine-tuning; as the levator function approaches 6 mm the success of levator advancement decreases, and under 6 mm most surgeons will opt for a frontalis sling procedure.
• Ptosis is a difficult surgical challenge that often is confused with the
simpler technique of blepharoplasty. Ptosis surgery should be performed by an experienced eyelid surgeon.
• Avoid surgery or undercorrect when poor Bell’s reflex or decreased corneal sensation exists.
• Treat underlying medical condition.
Prognosis
Excellent for aponeurotic and mechanical ptosis; fair to good for congenital ptosis, depending on the levator function; variable for myogenic and neurogenic ptosis.
Dermatochalasis
Laxity of the upper eyelid tissues resulting in redundancy of skin and subcutaneous tissue. Frequently associated with herniation of orbital fat through an attenuated orbital septum. May be associated with upper lid ptosis or pseudoptosis (mechanical effect of dermatochalasis). Profound dermatochalasis may result in superior visual field defect.
Management is surgical with careful attention given preoperatively to coexisting conditions (e.g., ptosis). Lower lid dermatochalasis, on very rare occasions, may limit vision in downgaze due to extreme orbital fat herniation.
FIGURE 3-22 A patient with pseudoptosis from dermatochalasis.
FIGURE 3-23 Dermatochalasis with redundant upper eyelid skin and subcutaneous tissue and herniated orbital fat. When the excess skin is retracted, the upper lid margin can be seen in the normal position.
Ectropion
Definition
Eversion of the eyelid margin.
Etiology
Cicatricial
Due to burns (thermal or chemical), ocular trauma (surgical or mechanical), or chronic inflammation with anterior lamellar contraction.
Congenital
Due to vertical shortening of anterior lamella (skin and orbicularis oculi), rarely isolated, may be associated with blepharophimosis syndrome (blepharophimosis, ptosis,
epicanthus inversus, and telecanthus).
Inflammatory
Due to chronic eyelid skin inflammation (atopic dermatitis, herpes zoster infections, rosacea).
Involutional
Due to horizontal lid laxity and tissue relaxation, followed by lid elongation, sagging, and conjunctival hypertrophy; usually involves lower eyelid; most frequent cause of ectropion in adults.
Mechanical
Due to lid edema, bulky lid tumors, orbital fat herniation, or lid-riding spectacles.
Paralytic
Usually follows cranial nerve VII (Bell’s) palsy; can be temporary.
Symptoms
Tearing, chronic eyelid or ocular irritation, or asymptomatic.
Signs
Eversion of eyelid margin, conjunctival keratinization, injection and hypertrophy,
superficial punctate keratitis, dermatitis (from chronic tearing and rubbing); may have corneal ulceration or scarring.
FIGURE 3-24 Involutional ectropion of the left lower eyelid.
Evaluation
• Complete ophthalmic history with attention to history of eye surgery, trauma, burns, infections, or facial droop (Bell’s palsy).
• Complete eye exam with attention to lids, orbicularis function, lateral canthal tendon laxity, herniated fat and scarring, conjunctiva, and cornea.
Management
• Treat ectropion-related corneal and conjunctival exposure with topical lubrication with preservative-free artificial tears up to q1h and ointment qhs.
CICATRICIAL
• Four-step procedure: (1) cicatrix release and relaxation; (2) horizontal lid tightening with lateral tarsal strip; (3) anterior lamella lengthening with full-thickness skin graft or cheek lift; and (4) posterior lamellar spacer (with ear cartilage or other material).
CONGENITAL
• Mild ectropion often requires no treatment. Moderate or severe ectropion treated like cicatricial ectropion with horizontal lid tightening and full-thickness skin graft to vertically lengthen anterior lamella.
INFLAMMATORY
• Treat underlying dermatologic condition. Temporizing measures include taping temporal side of eyelid, using moisture chamber goggles, and topical
lubrication with preservative-free artificial tears up to q1h.
INVOLUTIONAL
• Three procedures may be used individually or in combination: (1) medial spindle procedure for punctal ectropion; (2) horizontal lid shortening using lateral tarsal strip procedure, lateral lid wedge resection, or canthal tendon plication; and (3) lower lid retractor reinsertion.
MECHANICAL
• Relieve mechanical force causing ectropion (tumor or fat removal, eyeglass adjustment, etc.), and horizontal lid tightening.
PARALYTIC
• Often resolves spontaneously within 6 months if due to Bell’s palsy.
Temporizing measures include taping temporal side of eyelid, suture
tarsorrhaphy, using moisture chamber goggles, and topical lubrication with preservative-free artificial tears up to q1h; rarely, if chronic, consider
canthoplasty, lateral tarsorrhaphy, brow suspension, and horizontal lid tightening with or without middle lamellar buttress such as ear cartilage.
Prognosis
Usually good with surgical treatment; cicatricial and inflammatory ectropion are prone to recurrence; paralytic ectropion may resolve spontaneously within 6 months after Bell’s palsy.
Entropion
Definition
Inversion of the eyelid margin; may affect either eyelid, although the lower lid is affected more frequently.
Etiology
Cicatricial
Due to posterior lamella (tarsus and conjunctiva) shortening with lid inversion and rubbing of lashes and lid margin on globe; associated with Stevens–Johnson syndrome, ocular cicatricial pemphigoid, trachoma, herpes zoster, eye surgery, ocular trauma, thermal or chemical burns, and chronic conjunctivitis from long-term topical glaucoma medications.
Congenital
Due to structural tarsal plate defects, shortened posterior lamellae, or eyelid retractor dysgenesis; horizontal tarsal kink is an unusual form of congenital entropion that usually affects the upper eyelid.
Involutional
Most common cause of entropion in older patients, usually affects lower lid;
predisposing factors include horizontal lid laxity, overriding preseptal orbicularis, disinserted or atrophied lid retractors, and involutional enophthalmos.
Spastic
Due to ocular inflammation or irritation; often occurs following eye surgery in patients with early underlying involutional changes.
Symptoms
Tearing, foreign body sensation, and red eye.
Signs
Inturned eyelid margin, keratinized eyelid margins (cicatricial), horizontal lid laxity, overriding preseptal orbicularis, enophthalmos, symblepharon (cicatricial), conjunctival injection, superficial punctate keratitis; may have corneal ulceration or scarring.
FIGURE 3-25 Cicatricial entropion of the right lower eyelid.
Differential Diagnosis
Trichiasis, distichiasis, blepharospasm.
Evaluation
• Complete ophthalmic history with attention to history of eye surgery, trauma, burns, or infections.
• Complete eye exam with attention to lids, lid tone (snapback test), lower lid margin (sagging), medial and lateral canthal tendons, inferior fornix (unusually deep), digital eversion test at the inferior border of tarsus to distinguish involutional from cicatricial entropion (involutional rotates, cicatricial does not).
Management
• If corneal involvement exists, topical antibiotic ointment (erythromycin or bacitracin bid to qid).
CICATRICIAL
• Excision of scar and consider anterior lamellar resection or recession for minimal involvement; tarsal fracture procedure for lower lid involvement;
tarsal graft from preserved sclera, ear cartilage, or hard palate if the tarsus is badly damaged; may also require conjunctival and mucous membrane grafts in severe cases.
CONGENITAL
• Rarely improves and often requires surgical treatment to correct underlying anatomic defect.
INVOLUTIONAL
• Three procedures may be used individually or in combination: (1)
temporizing measure with lid taping below lower lid, Quickert suture, or thermal cautery; (2) horizontal lid tightening with lateral tarsal strip procedure; and (3) lid retractor repair with full-thickness transverse
blepharoplasty and eyelid margin rotation (Wies’ procedure) or retractor reinsertion.
SPASTIC
• Break entropion–irritation cycle by taping inturned lid to evert margin, thermal cautery, or suture techniques to temporarily evert lid; consider botulinum type A toxin (Botox) injections; often requires more definitive procedure as involutional changes progress (see above).
Prognosis
Good except for autoimmune or inflammatory-related cicatricial entropion.
Blepharospasm
Definition
Bilateral, uncontrolled, episodic contraction of the orbicularis oculi.