Lecture 1- Tear Film Optics

Question 1

Anterior chamber of the ey contains 6 things:

Answer 1

Epithelium
Bowman's Membrane
Stroma
Descemet's membrance
Endothelium
Dua's Layer

Question 2

:Protects the cornea mainly by providing a barrier against water, larger molecules and toxic substances

Answer 2

Epithelium

Question 3

:consists mainly of randomly arranged collagen fibrils

Answer 3

Bowman’s Membrane

Question 4

Comprises 90% of corneal thickness and over 200 collagen lamellae

Answer 4

Stroma

Question 5

Stroma: Collagen fibrils within each lamella run ______ to each other and the successive lamellae run across the cornea at
_____ to each other

This arrangement maintains an ordered ___________ while enhancing_________

Answer 5

parallel

angles

transparency

mechanical strength

Question 6

: is single layered formed as hexagonal or honey comb structure. The
_______ regulates the ________ of the cornea in order to maintain the stroma at
about _____ hydration and thus retain transparency

Answer 6

endothelium
endothelium
fluid balance
78%

Question 7

is the basement membrane of the endothelial cells

Answer 7

Descemet’s membrane

Question 8

(a recent discovery) is located between the stroma & Descemet’s membrane. It
is composed of type-1 collagen bundles.

Answer 8

Dua’s layer

Question 9

Pre-corneal tear film :
the most _______ refractive surface of the eye
Basically, made of two thin surfaces of almost _________
• It is composed of
___________layers.

• R.I of TF is ______.

• Optical power of the tear film is _______ [Coupled with cornea, power is
_______]
• Essential for a ______ and reduces_________when the tear film dries
out.
• Its _________is important of the optical quality of the eye.

Answer 9

anterior

equal radii

oily, aqueous and mucous

1.336

48. 35D.
49. 36D

clear vision transparency
stability

Question 10

TF stability is measured by ____________

and refers primarily to ‘_______’. A stable tear film is one in
which a minimum amount of ___________
Instability of TF occurs due to the depletion of _______________

Answer 10

lack ofstability

evaporation rate

tears evaporate.

aqueous component of tears.

Question 11

“Since the change in refractive index at the ________interface is far ________
(e.g. Dn=0.37) than at any other optical interface in the eye, irregularities in the
___________have the potential to significantly degrade the optical
quality of the eye.”

Answer 11

air-tear
greater

anterior surface of the tears

Question 12

____ million people in US over ____ yrs of age have Dry eye

syndrome

Answer 12

5

50

Question 13

It is a multifactorial disease, defined as “symptoms of________________,
_________________,
________________

with potential damage to the ocular surface.”

Answer 13

discomfort, visual disturbance, and tear film instability

Question 14

Higher order abberations like ________ and ________ are ______ more likely in dry eye then healthy

Answer 14

spherical
coma
2.5

Question 15

Irregularities in the tear film structure that appears after an extended period of
___________ can cause significant changes in the retinal image quality

Answer 15

non-blinking

Question 16

The contact lens sits ___, and not ____ the tear film

Answer 16

in

on

Question 17

contact lens is ~____ times thicker than the aqueous layer.

Answer 17

10

Question 18

The contact lens interaction with the tear film is dependent both on the _________ and _________

Answer 18

lens material, and on

the individual’s tear chemistry.

Question 19

The effects of the contact lens wear on the tear film is

• Lens can deplete the levels of specific components in the tear film by ________
• Lens can stimulate the biochemical generation of ______________

Answer 19

sorption

additional component

Question 20

Tear film stability ________with age
significantly.

• In general, men have significantly _____
  TBUT compared to women.
• It is also found that Caucasians have ____
  TBUT compared to Asian counterparts.
  -

Answer 20

decreases

longer

higher