Blepharitis overview

# Overview
Blepharitis is characterized by inflammation of the eyelid margins.
Blepharitis may be classified according to the anatomic location of the disease into 2 subtypes: anterior and posterior. Additionally, blepharitis may be classified based on the duration of symptoms into either acute or chronic.
The exact pathogenesis of blepharitis is not fully understood. 
It is thought that blepharitis is caused by either bacterial colonization (Staphylococcus aureus or Staphylococcus epidermidis) in the eyelids or meibomian gland dysfunction. Blepharitis may also caused by allergens and mites that affect the eyelashes.
Blepharitis must be differentiated from conjunctivitis, trichiasis, dry eye syndrome, keratitis, hordeolum, and chalazion.
Blepharitis is usually asymptomatic until the disease progresses. As it progresses, the patient begins to notice a foreign body sensation, itching, irritation, and crusting of the eyelids. Blepharitis can frequently be improved but is rarely eliminated. If left untreated, severe blepharitis may cause loss of eyelashes, scarring of the eyelids, corneal involvement, and ultimately blindness. Common complications of blepharitis include loss of eyelashes, hordeolum, chalazion, corneal ulcer, and conjunctivitis.
Blepharitis is associated with a favorable long-term prognosis.
Physical examination of patients with blepharitis is usually remarkable for irritated eyelid edges, crusting of the lashes, entropion, ectropion, poliosis, and diffuse conjunctival injection.
In general, blepharitis is diagnosed based on clinical features alone.
There are no diagnostic lab findings associated with blepharitis. Blepharitis is diagnosed based on clinical features alone.
Eyelid hygiene and regular cleaning are the mainstay of therapy for blepharitis. 
Antimicrobial topical therapy may be indicated in some cases depending on the causative pathogen and the underlying cause.

# Historical Perspective
Blepharitis was first described in the late 19th century as "conjunctivitis meibomianae" in a patient with accumulated sebaceous-like material in the meibomian glands.

# Classification
Blepharitis may be classified according to the anatomic location of the disease into 2 subtypes: anterior and posterior. Additionally, blepharitis may be classified based on the duration of symptoms into either acute or chronic.

# Pathophysiology
The exact pathogenesis of blepharitis is not fully understood. 
It is thought that blepharitis is caused by either bacterial colonization (Staphylococcus aureus or Staphylococcus epidermidis) in the eyelids or meibomian gland dysfunction.
Blepharitis may also caused by allergens and lice that affect the eyelashes.

# Causes
Common causes of blepharitis include bacterial infections, dysfunctional meibomian glands, allergies (less common), and Demodex folliculorum (small parasitic mites).

# Differentiating Blepharitis from other Diseases
Blepharitis must be differentiated from allergic contact dermatitis, conjunctivitis, trichiasis, dry eye syndrome, keratitis, hordeolum, chalazion, rosacea, and sebaceous carcinoma.

# Epidemiology and Demographics
Blepharitis is one of the most common ocular disorders encountered in clinical practice.
Up to 20,000 per 100,000 adults over the age of 45 report some discomfort from blepharitis and meibomian gland dysfunction (MGD).

# Risk Factors
Common risk factors in the development of blepharitis are dry eye syndrome, dermatologic conditions (acne rosacea, seborrheic dermatitis), demodicosis (chronic blepharitis), lice, and allergies.

# Screening
Screening for blepharitis is not recommended.

# Natural History, Complications and Prognosis
Blepharitis is usually asymptomatic until the disease progresses. As it progresses, the patient begins to notice a foreign body sensation, itching, irritation, and crusting of the eyelids. Blepharitis can frequently be improved but are rarely eliminated. If left untreated, severe blepharitis may cause alterations in the eyelid margin, loss of eyelashes, scarring of the eyelids, conjunctivitis, corneal involvement, superficial keratopathy, and ultimately blindness. Common complications of blepharitis include loss of eyelashes, hordeolum, chalazion, corneal ulcer, and conjunctivitis.
In general, blepharitis is associated with a favorable long-term prognosis. Severe blepharitis is rarely associated with permanent alterations in the eyelid margin or vision loss from superficial keratopathy. Therefore, severe blepharitis is associated with a poor prognosis.

# Diagnosis

## History and Symptoms
A detailed and thorough history from the patient is necessary. Specific areas of focus when obtaining a history from the patient include history of smoking, use of retinoids, prior history of acne rosacea, and history of seborrheic dermatitis. Common symptoms of blepharitis include red, swollen,and itchy eyelids, burning sensation, crusting or matting of eyelashes in the morning, light sensitivity, blurred vision, and oily skin.

## Physical Examination
Physical examination of patients with blepharitis is usually remarkable for irritated eyelid edges, hard crusting of the lashes, entropion, ectropion, poliosis, and diffuse conjunctival injection.

## Laboratory Findings
There are no diagnostic lab findings associated with blepharitis. Blepharitis is diagnosed based on clinical features alone. Culture of eyelid margins may be indicated for some patients with blepharitis who have recurrent anterior blepharitis with severe inflammation, as well as patients who are not responding to therapy.

## Other imaging findings
Posterior blepharitis overlaps with meibomian gland dysfunction (MGD). Dynamic meibomian imaging (DMI) can be used to obtain a distinct picture of the entire everted inferior tarsal plate in a patient with blepharitis.
There are no electrocardiogram, X ray, CT scan, MRI, and ultrasound findings associated with blepharitis.

## Other diagnostic studies
Other diagnostic studies for blepharitis include Slit lamp examination, tear break up time (TBUT), and measurement of tear osmolarity.

# Treatment

## Medical Therapy
Eyelid hygiene and regular cleaning are the mainstay of therapy for blepharitis. 
Antimicrobial topical therapy may be indicated in some cases depending on the causative pathogen and the underlying cause.

## Surgery
Surgery is not the firstline treatment option for patients with blepharitis. Surgery is usually reserved for patients with complications, such as chalazion, entropion, ectropion, or horizontal eyelid laxity.

## Primary Prevention
Effective measures for the primary prevention of blepharitis include good self-hygiene and anti-dandruff shampoo.

## Secondary Prevention
Secondary prevention strategies following blepharitis include good self-hygiene, anti-dandruff shampoo, removing eye makeup before bedtime, and avoiding eyeliner.