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Showing posts with label vision physiology. Show all posts
Showing posts with label vision physiology. Show all posts

Wednesday, March 28, 2012

Atopic keratoconjunctivitis (AKC)

Atopic  keratoconjunctivitis (AKC) can be thought of as an adult equivalent of vernal keratoconjunctivitis and is often associated with atopic dermatitis. Most of the patients are young atopic adults, with male predominance.

Symptoms include:
  • Itching, soreness, dry sensation.
  • Mucoid discharge.
  • Photophobia or blurred vision.
Signs
  • Lid margins are chronically inflamed with

Saturday, March 24, 2012

VIRAL CONJUNCTIVITIS

Most of the viral infections tend to affect the epithelium, both of the conjunctiva and cornea, so, the typical viral lesion is a 'keratoconjunctivitis'. In some viral infections, conjunctival involvement is more prominent (e.g., pharyngo-conjunctival fever), while in others cornea is more involved (e.g., herpes simplex).

Viral infections of conjunctiva include:
  • Adenovirus conjunctivitis
  • Herpes simplex keratoconjunctivitis
  • Herpes zoster conjunctivitis
  • Pox virus conjunctivitis
  • Myxovirus conjunctivitis
  • Paramyxovirus conjunctivitis
  • ARBOR virus conjunctivitis
Clinical presentations. Acute viral conjunctivitis may
present in

ADULT INCLUSION CONJUNCTIVITIS

Adult Inclusion conjunctivitis is a type of acute follicular conjunctivitis associated with mucopurulent discharge. It usually affects the
sexually active young adults.

Etiology
Inclusion conjunctivitis is caused by serotypes D to
K of Chlamydia trachomatis. The primary source of
infection is urethritis in males and cervicitis in

Friday, March 23, 2012

Trachoma Management

Management of trachoma should involve curative as
well as control measures.

A. Treatment of active trachoma
Antibiotics for treatment of active trachoma may be
given locally or systemically, but topical treatment is
preferred because:

  • It is cheaper,
  • There is no risk of systemic side-effects, and

TRACHOMA Complications & Diagnosis

Complications
The only complication of trachoma is corneal ulcer
which may occur due to rubbing by concretions, or
trichiasis with superimposed bacterial infection.

Diagnosis
A. The clinical diagnosis of trachoma is made from
its typical signs; at least two sets of signs should be
present out of the following:

Grading of trachoma

McCallan's classification
McCallan in 1908, divided the clinical course of the
trachoma into following four stages:
  • Stage I (Incipient trachoma or stage of infiltration). It is characterized by hyperaemia of palpebral conjunctiva and immature follicles.
  • Stage II (Established trachoma or stage of florid infiltration). It is characterized by appearance of mature

TRACHOMA Symptoms & Signs

Symptoms
  • In the absence of secondary infection, symptoms are minimal and include mild foreign body sensation in the eyes, occasional lacrimation, slight stickiness of the lids and scanty mucoid discharge.
  • In the presence of secondary infection, typical symptoms of acute mucopurulent conjunctivitis develop.
Signs
A. Conjunctival signs
1. Congestion of upper tarsal and forniceal conjunctiva.

2. Conjunctival follicles. Follicles (Fig. 1 and Fig.2) look like boiled

what is trachoma ?

Trachoma (previously known as Egyptian ophthalmia) is a chronic keratoconjunctivitis, primarily affecting the superficial epithelium of
conjunctiva and cornea simultaneously. It is characterised by a mixed follicular and papillary response of conjunctival tissue. It is still one of the
leading causes of 

Wednesday, March 21, 2012

ACUTE MEMBRANOUS CONJUNCTIVITIS

It is an acute inflammation of the conjunctiva,
characterized by formation of a true membrane on the
conjunctiva. Now-a-days it is of very-very rare
occurrence, because of markedly decreased
incidence of diphtheria. It is because of the fact that
immunization against diptheria is very effective.

Etiology
The disease is typically caused by Corynebacterium
diphtheriae and occasionally by virulent type of

Sunday, March 18, 2012

Structure of conjunctiva

Histologically, conjunctiva consists of three layers
namely, (1) epithelium, (2) adenoid layer, and (3)
fibrous layer (Fig. 1 below ).


1. Epithelium. The layer of epithelial cells in
conjunctiva varies from region to region and in its
different parts as

follows:
  • Marginal conjunctiva has 5-layered stratified squamous type of epithelium.
  • Tarsal conjunctiva has

Friday, March 16, 2012

INSUFFICIENCY OF ACCOMMODATION

(continue  ACCOMMODATION ANOMALIES) Insufficiency of accommodation

The term insufficiency of accommodation is used when the accommodative power is significantly less than the normal physiological limits for the patient's
age. Therefore, it should not be confused with presbyopia in which the physiological insufficiency of accommodation is normal for the patient's age.

Causes

1. Premature sclerosis of lens.
2. Weakness of ciliary muscle due to

Wednesday, March 14, 2012

Accommodation eye

Definition. As we know that in an emmetropic eye, parallel rays of light coming from infinity are brought to focus on the retina, with accommodation being at rest. However, our eyes have been provided with a unique mechanism by which we can even focus the
diverging rays coming from a near object on the retina in a bid to see clearly (Fig. 1).
This mechanism is called accommodation. In it there occurs increase in

 FIG 1 Effect of accommodation on divergent rays
entering the eye
Fig. 2. Changes in the crystalline lens during
accommodation.
the power of crystalline lens due to increase in the
curvature of its surfaces (Fig. 2).
At rest the