diease

Dry Eyes


Dry Eyes overview and Definition

The normal mechanism of the eye is to shed tears. When the eyes are in shortage of tears it might result in dry eyes. Dry eyes also occurs when eyes do not make the right type of tears or tear flim.

It might result in the inflammation the conjunctiva. The conjunctiva is the thin clear tissue that lies over the white part of the eye and lines the inside of the eyelid.

When someone blink a flim of tears spreads over the eye. This keeps the eye’s surface smooth and clear. The tear flim is important for good vision.

The tear film is made of three layers:

  • An oily layer
  • A watery layer
  • A mucus layer

Each layer of the tear film serves a purpose:

The oily layer is the external covering of the tear flim.  It makes the tear surface smooth and keeps tears from drying up too quickly. This layer is made in the eye’s meibomian glands.

The watery layer is the middle of the tear flim. It makes up most of what we see as tears. This layer cleans the eye, washing away particles that do not belong to the eye. This layer comes from the lacrimal gland in the eyelids.

The medical term used for dry eyes is Xerophthalmia

The mucous layer is the inner layer of the tear flim. This helps to spread the watery layer over the eye’s surface keeping the eye moist. Without mucus, the tears would not stick to the  eye and inside your eyelids.

Normally, our eyes constantly make tears to stay moist. If our eyes are irritated, or we cry, our eyes make a lot of tears. But, sometimes the eyes don’t make enough tears or something affects one or more layers of the tear film. In those cases, we end up with dry eyes.

 


Pathophysiology

When allergens or triggering fcators enters the tear flim, it triggers the conjunctival mast cells that bear the IgE antibodies.

Calcium enters the cell

Degranulation of mast cells results in production of Histamine

Histamine release causes Vasodilatation and oedema and resulting reddishness and swelling of the eyes and result in xerophthalmia


Routes of Transmission

Xerophthamia occurs by the exposure to contaminated air and water.  It also spreads by bare exposure of eye to environment


Clinical signs & symptoms

  • the feeling that some irritants in the eye or some gritty sensation in the  eye
  • red eyes
  • burning eyes
  • itchy eyes
  • watery eyes
  • puffy eyelids
  • blurry hazy vision
  • being extra sensitive to light
  • lots of mucus, pus, or thick yellow discharge from the eyes. There can be so much that your eyelashes stick together (usually with bacterial conjunctivitis).
  • Blepharitis( when eyelids are swollen and red)
  • Entropian ( when eyelids are turn in) ectropian ( eyelids turn outward)


Differential Diagnosis

  • External examination of the eye, including lid structure and blink dynamics.
  • Evaluation of the eyelids and cornea using bright light and magnification.
  • Measurement of the quantity and quality of tears for any abnormalities. Special dyes may be put in the eyes to better observe tear flow and to highlight any changes to the outer surface of the eye caused by insufficient tears.
  • Patient history to determine the symptoms, when the symptoms began, and whether any general health or environmental conditions are contributing to the problem.
  • Visual acuity measurements to determine whether vision has been affected.
  • Evaluation of the conjunctiva and external eye tissue using bright light and magnification.
  • Evaluation of the inner structures of the eye to ensure that no other tissues are affected by the condition.
  • Supplemental testing, which may include taking cultures or smears of conjunctival tissue. This is particularly important in cases of chronic conjunctivitis or when the condition is not responding to treatment.

Cytology scraping:

Ophthalmologist acquires the scraping from the conjunctiva and see those abnormalities using microscopy.

  • Polymerase chain reaction:

This is done by the amplification of the DNA of the infectious agents.

  • Direct fluoresecense monoclonal antibody test:

The smears obtained from the conjunctiva are stained and results are examined.

 


Prognosis

Dry eyes can resolve within 5-7 days in 65 % of cases if the triggering factors are removed. 

. And the prognosis is completely dependant on the causative factor.

 


Prevention

  • Don't touch your eyes with your hands.
  • Wash your hands often.
  • Use a clean towel and washcloth daily.
  • Don't share towels or washcloths.
  • Change your pillowcases often.
  • Throw away your eye cosmetics, such as mascara.
  • Don't share eye cosmetics or personal eye care items.