LACRIMAL APPARATUS
| A | Lipid layer | |
| B |
Aqueous layer |
|
| C |
Mucinous layer |
|
| D |
None of the above |
Which of the following layer of the tear film is the superficial layer which is in contact with air?
| A |
Lipid layer |
|
| B |
Aqueous layer |
|
| C |
Mucinous layer |
|
| D |
None of the above |
Layers of the tear film:
- The superficial lipid layer is a monomolecular film at the air-tear interface derived from meibomian glands. It is thought to retard evaporation and form a watertight seal when the lids are closed.
- The middle aqueous layer is elaborated by the major and minor lacrimal glands and contains water-soluble substances (salts and proteins).
- The deep mucinous layer is composed of glycoprotein and overlies the corneal and conjunctival epithelial cells. It is elaborated by goblet cells of the conjunctiva and also by the crypts of Henle and glands of Manz.
| A |
Rotation of femur on tibia |
|
| B |
Menisci do not heal |
|
| C |
Locking and unlocking episodes |
|
| D |
All |
A i.e. All of the above
All are true regarding tear film except:
| A |
Consists of aqueous, lipid & mucus layer |
|
| B |
Lipid layer is secreted by meibomian glands |
|
| C |
Aqueous layer is formed by filtration from blood capillaries |
|
| D |
Deficiency cause dry eye |
C i.e. Aqueous layer is formed by filtration from blood capillaries
Absence of tear film is seen in:
| A |
Conjunctivitis |
|
| B |
Lacrimal gland removal |
|
| C |
Herpes keratitis |
|
| D |
Keratoconjunctivitis sicca |
- Keratoconjunctivitis Sicca (KCS) or Dry eye syndrome is mainly caused due to aqueous tear deficiency.
- KCS is defined as a multifactorial disease of the tear film and ocular surface that results in symptoms of discomfort, visual disturbance, and tears film instability with potential damage to the ocular surface. It is accompanied by the increased osmolality of the tear film and inflammation of the ocular surface.
- A defect in any component of tear film may lead to dry eye syndrome but primarily it is from aqueous tear deficiency.
The tear film has three components:-
- Outer lipid layer: It is the outer oily layer which retards evaporation of aqueous tears. It lubricates eyelids and prevents spillover of tears over lid margin.
- Middle aqueous layer: It supplies oxygen to cornea (transparent layer covering the front of the eye ) and makes the surface smooth by filling minute irregularities. It prevents bacterial infection and also washes away the debris.
- Inner mucin layer: It makes cornea wettable by aqueous in the middle layer.
| A |
Keratoconjunctivitis sicca |
|
| B |
Lacrimal gland removal |
|
| C |
Canalicular block |
|
| D |
Herpetic keratitis |
A i.e Keratoconjunctivitis sicca
- Mucin synthesising goblet cells are destroyed in Keratoconjunctivitis sicca caused by trachoma and ocular pemphigoid.
| A |
Mucus layer |
|
| B |
Aqueous layer |
|
| C |
Oily layer |
|
| D |
None of the above |
Ans. Mucus layer
Thickest layer of tear film is:
| A |
Mucus layer |
|
| B |
Aqueous layer |
|
| C |
Oily layer |
|
| D |
None of the above |
Ans. Aqueous layer
Keratoconjunctivitis sicca refers to:
| A |
Aqueous tear deficiency dry eye |
|
| B |
Mucin deficiency dry eye |
|
| C |
Lipid deficiency dry eye |
|
| D |
All types of dry eye |
Ans. Aqueous tear deficiency dry eye
Normal values of tear film break up time range from:
| A |
5 to 10 seconds |
|
| B |
10 to 15 seconds |
|
| C |
15 to 20 seconds |
|
| D |
15 to 30 seconds |
Ans. 15 to 30 seconds
Tear film break-up-time is the time:
| A |
Between the last blink and the appearance of first dry spot on the cornea |
|
| B |
Taken for appearance of dry spot between two blinks |
|
| C |
Taken by successive blinks to break the tear film |
|
| D |
Taken for disappearance of dry spots on the cornea |
Ans. Between the last blink and the appearance of first dry spot on the cornea
Tear lysozyme levels are decreased in:
| A |
Keratoconjunctivitis sicca |
|
| B |
Stevens Johnson syndrome |
|
| C |
Ocular pemphigoid |
|
| D |
All of the above |
Ans. Keratoconjunctivitis sicca
The normal pH of tears is:
March 2007
| A |
6.0 |
|
| B |
6.5 |
|
| C |
7.0 |
|
| D |
7.5 |
Ans. D: 7.5
Human tear film/ precorneal film has three distinct layers, from the most outer surface:
I. Lipid layer secreted by meibomian glands (or tarsal glands) – coats the aqueous layer; provides a hydrophobic barrier that evaporates and prevents tears spilling onto the cheek.
These glands are found among the tarsal plates.
Thus, the tear fluid deposits between the eye proper and oil barriers of the lids
II. Aqueous layer- secreted by lacrimal gland – promotes spreading of the tear film; promotes the control of infectious agents; promotes osmotic regulation
III. Mucous layer- secreted by conjunctival goblet cells – coats the cornea;provides a hydrophilic layer;allows for even distribution of the tear film; covers the cornea
Teardrops formed by all except ‑
| A | Glands of Manz | |
| B | Meibomian, Zeis and Moll glands | |
| C |
Lacrimal glands |
|
| D |
Lacrimal puncta |
Ans. is ‘d’ i.e., Lacrimal puncta
The major function of lacrimal apparatus is to secrete and drain the tear. Tear film consists of 3 layers :‑
- Mucous or mucin layer (innermost):- Secreted by conjunctival goblet cells, crypts of Henle, glands of Manz.
- Aqueous layer (intermediate) :- This forms the bulk of the tear. It is secreted by main lacrimal and accessory lacrimal glands.
- Lipid layer (outermost) :- Secreted by the Meibomian Zeis, and Moll glands.
