Optics
what's the primary refractive interface of the eye
air-tear interface
BONUS QUESTION: if the cornea was 100% dry (ie- air-tear interace replaced by air-cornea interface), would you still need a gonio lens to view the angle?
(*paint pic)
(1) What nerve and muscle close the eyelids?
(2) What nerve and muscle open the upper eyelid
(1) Close = CN7, Orbic
(2) Open =
(a) CN3, LPS
(b) Symp, Muller
Name the 3 layers of the tear-film AND the sources of each.
- Lipid (Meibomian Glands)
- Aqueous (primarily Lacrimal Gland)
- Mucin (Goblet)
BCSC Note: rather than separate layers "It is now thought of as a uniform gel consisting of soluble mucus, which is secreted by conjunctival goblet cells, mixed with fluids and proteins secreted by the lacrimal glands."
Average corneal height & width?
10-11(h) x 11-12(w)
What region of the Cornea is thickest?
Periphery ~700
(*pentacam)
What's the total dioptric power of the eye? (+/-1)
58.60 D
Eyelashes are replaced every ___ - ___ months.
2-3 months
(important for f/u after mech epilation)
What is the arterial supply of the conjunctiva?
(hint: this artery also feeds eyelids)
Anterior Ciliary Artery <-- Muscular branch of ophthalmic artery
(*knee or quad of "one-armed dude")
Where does the cornea get Nutrition?
Where does the cornea get Oxygen?
Nutrition = glucose from aqueous
Oxygen = air diffusing through tear-film
(a) normal range for central endothelial cell count?
(b) threshold count for corneal edema?
(a) 2,000-3,000 cells/mm2
(b) <500 cells/mm2
(note: count declines by 0.6% per year)
What's the dioptric power of the Cornea? (+/-1)
43.25 D
(74% of total power of eye)
arrange the following in order of least to greatest regarding corresponding blink rate
- in conversation
- while concentrating (ex: reading)
- at rest
conversation(20/min) > rest(10-15) > reading(5)
(Important for DES & diagnosing incomplete blink*)
Where does the conjunctiva insert?
A: inserts into Limbus
- bulbar conj loosely adherent to Tenon's
- palpebral conj tightly adherent to Tarsus
(these attachments forms the fornices, email pic*)
name the SIX (not 5) layers of the cornea
***DAILY TRIPLE!***
(1) Epithelium
(2) Bowman Layer
(3) Stroma
(4) Pre-Descemet Layer or "Dua's Layer"
(essentially residual stroma after DALK & DSEK)
https://en.wikipedia.org/wiki/Pre-Descemet%27s_Endothelial_Keratoplasty
https://www.youtube.com/watch?v=M4n4bCxApAc
(5) Descemet Membrane
(6) EndotheliuM
What are the Palisades of Vogt?
Niche for limbal stem cells
https://www.dovepress.com/cr_data/article_fulltext/s83000/83676/img/OPTH-83676-F01.jpg
What is the refractive index of:
(1) Air
(2) Water
(3) Cornea
(1) Air = 1.0
(2) Water = 1.33
(3) Cornea = 1.37
Name the layers of the Pretarsal Upper Eyelid
Skin, Orbic, (LPS inserting on Tarsus and sub-Q making lid-crease), Tarsus, Conj
(a) Recurrent Corneal Erosions are following a traumatic corneal abrasion may be due to improper formation of ________________, which normally anchor the basal epithelial cells the basement membrane.
(a) What percent of stromal content is water? (+/-3)
(b) What two layers function as corneal "barriers" to over-hydration?
(a) 78%
(b) epi-barrier, endo-barrier & pump
What nerve innervates the Cornea?
What is the formula for calculating the Refractive Power of a lens surface (ex: cornea)?
(difference in refractive indices) / (radius) = Power
(1.3375-1.00) / (0.0078m) = 43.2
(of note: tear-cornea & cornea-aqueous cancel out, see paint pic*)
Name the layers of the Pre-Septal Upper Eyelid
Skin, Orbic, Septum, Pre-Aponeurotic orbital fat, LPS, Mullers, Conj
What types of collagen are in the Stroma?
at least 1, 5, & 6 per BCSC...
"4 makes the floor (lens cap & DM), 2 in the goo (vitreous), everything else in the stroma"
Match layers & corresponding thickness in microns
-Layers: epi, BL, stroma, DM, Endo, Full-thickness
-Thickness: 540, 90%, 40-50, 15, monolayer of cells
Cornea=540, Epi=40-50, BL=15, Stroma=90% DM=3 at birth--> 10-12 as an Adult, Endo=monolayer
Explain the Richard Thoft's "XYZ Hypothesis" of Corneal Epithelial Regeneration...
***DAILY DOUBLE***