Anatomy - Sharma Flashcards
1
Q
What are the average horizontal and vertical measurements of the anterior cornea?
A
12mm H x 11mm V
2
Q
What are the average horizontal and vertical measurements of the posterior cornea?
A
11.7mm H/V
3
Q
What is the average radius of curvature of the anterior cornea?
A
7.8mm
4
Q
What is the average radius of the posterior cornea?
A
6.5mm
5
Q
What is the average CCT?
A
530 microns
6
Q
What is the average peripheral corneal thickness?
A
710 microns
7
Q
Why might WTR astigmatism change to ATR astigmatism in old age?
A
Lens changes
Loss of lid tension
8
Q
What is the refractive power of the cornea?
A
43D
9
Q
What is the refractive index of the tear film?
A
1.336
10
Q
What is the refractive index of the cornea?
A
1.376
11
Q
What are the 5 layers of the cornea, from anterior to posterior?
A
Epithelium Bowman's layer Stroma Descemet's membrane Endothelium
12
Q
How many cell layers thick is the epithelium?
A
5-7
13
Q
What are the 3 cell types of the corneal epithelium?
A
Apical cells
Wing cells
Basal cells
14
Q
Which corneal epithelial layer is the only layer to undergo mitosis?
A
Basal cells
15
Q
How many layers of wing cells are there in the cornea epithelium?
A
2-3 layers
16
Q
How many layers of apical cells are there in the corneal epithelium?
A
2
17
Q
How are wing cells of the corneal epithelium adjoined?
A
Desmosomes
Gap junctions
18
Q
Apical cells of the corneal epithelium secrete what substance? What is its purpose?
A
Glycocalyx
Attaches mucin layer of the tear film
19
Q
What is the only cell layer in the cornea that is adhered with zonula occludens (tight junctions)?
A
Apical cells of the epithelium
20
Q
What are the potential causes of Recurrent Corneal Erosions?
A
Poor attachment of epithelium to basement membrane (BM)
Poor attachment of BM to underlying tissue
Hemidesmosome malfunction
EBMD
21
Q
How thick is Bowman’s layer?
A
8-14 microns
22
Q
When is Bowman’s layer produced?
A
Prenatally
23
Q
What produces Bowman’s layer?
A
Epithelium
24
Q
What type of collagen makes up Bowman’s layer?
A
Type 1
25
What is the purpose of Bowman's layer?
Provides shape and rigidity, resisting penetrating injury
26
If injured, what replaces Bowman's layer?
Scar tissue
| Epithelium (PRK)
27
In keratoconus, what layer of the cornea suffers the initial damage?
Bowman's layer
28
What is broken when corneal hydrops occurs?
Descemet's membrane
29
As a pterygium progresses onto the cornea, what cell layer is destroyed?
Bowman's layer
30
Band keratopathy involves what type of deposits, in what layer of the cornea?
Calcium deposits
| Bowman's layer
31
What is the average thickness of the stroma?
500 microns
32
What 3 main things compose the corneal stroma?
Collagen fibrils
Keratocytes
Extracelular matrix
33
What is the function of keratocytes in the cornea?
Maintain the stroma by synthesizing collagen and ECM
34
Where in the stroma is a higher density of keratocytes present?
Anterior stroma
35
Fibril bundles in the cornea run in what directions?
Limbus to limbus, parallel to the corneal surface
36
What fills in the space between fibril bundles of the cornea?
GAGs
37
GAGs attract and bind what?
Water
38
What is the main purpose of GAGs in the cornea?
Maintiain precise spacing between fibrils
39
How thick is Descemet's membrane?
5-15 microns (thickens with age)
40
What type of collagen makes up Descemet's membrane?
Type IV collagen
41
What layer of the cornea terminates at the limbus and forms Schwalbe's line?
Descemet's membrane
42
Descemet's membrane has weak attachments with what neighboring structures?
Stroma
| Endothelium
43
What are Hassall-Henle bodies?
Bulges of thickening Descemet's membrane bulging into the anterior chamber in the corneal periphery
44
How thick is the endothelium?
5 microns (1 cell)
45
What shape are corneal endothelial cells?
Hexagonal
46
If there is an injury to the corneal endothelium, how is the defect covered?
The endothelial cells stretch to cover the defect
47
Endothelial cells have what type of junctions, creating what kind of barrier?
Macula occludens
| Slightly leaky barrier
48
What is the most metabolically active layer of the cornea?
Endothelium (NaK pump)
49
What is pleomorphism?
Change in cell shape
50
What is polymegathism?
Change in cell size
51
What is corneal gutatta?
Thickening of Descemet's membrane in the central cornea
52
Gutatta indicate what type of dysfunction?
Endothelial dysfunction
53
The cornea sends afferent innervation through which nerve?
V1 - Trigeminal, ophthalmic
54
Nerves in the central cornea are open. At what portion of the cornea do nerves become myelinated?
Limbus
55
Where are most of the corneal nerves concentrated?
Anterior stroma, immediately beneath Bowman's laer
56
Which layers of the cornea are not innervated?
Descemet's membrane
| Endothelium
57
The sclera is continuous at the limbus with what layer of the cornea?
Stroma
58
Scleral opacity is due to what 2 things?
Low water content
| Irregular spacing of fibrils
59
What nerve innervates the posterior sclera?
Short ciliary nerve
60
What nerve(s) innervates all but the posterior sclera?
Long ciliary nerves
61
Is the sclera loose or dense connective tissue?
Dense
62
Is the episclera loose or dense connective tissue?
Loose
63
What layer of tears is secreted from the conjunctiva?
Mucin layer (goblet cells)
64
What are the two layers of the conjunctiva?
Epithelial layer
| Submucosal layer
65
What 3 things are found in the epithelial layer?
Goblet cells
Microvilli
Melanin
66
What things are found in the outer lymphoid layer of the submucosal conjunctiva?
Immune cells
Macrophages
Lymphocytes
PMNs
67
What things are found in the inner fibrous layer of the submucosal conjunctiva?
```
Collagen fibrils
Fibroblasts
Blood vessels
Lymphatic vessels
Nerves
```
68
What nerve innervates the bulbar conjunctiva?
Long posterior ciliary nerve
69
What nerve(s) innervates the palpebral conjunctiva?
V1 and V2
70
What is the purpose of the plica semilunaris?
Allow lateral movements of the eye
71
What is contained in the caruncle?
A large nest of accessory lacrimal and subaceous glandular tissue
Covered in epithelium with goblet cells
72
Where do limbal stem cells reside?
Palisades of Vogt
73
A pinguecula indicates a change in what layer of the conjunctiva?
Submucosal layer
74
A pterygium migrates along which corneal layer, and destroys which other layer?
Migrates along basement membrane
| Destroys Bowman's layer
75
Where is the iris the thickest?
In the collarette region
76
Where is the iris the thinest?
Iris base
77
What is iridodialysis?
Iris root tearing away from the ciliary body
78
What are the 4 layers of the iris?
Anterior border layer
Iris stroma and sphincter
Anterior epithelium and dilator
Posterior epithelium
79
What is the iris anterior border layer composed of?
Fibroblasts
| Pigmented melanocytes
80
What cells are found in the iris stroma?
Melanocytes
Fibroblasts
Lymphocytes
Macrophages
81
In what layer of the iris is the sphincter muscle found?
Iris stroma
82
In what layer of the iris is the dilator found?
Anterior epithelium
83
What type of cells make up the anterior epithelium of the iris?
Myoepithelial cells
84
What direction does the iris dilator muscle run?
Radially
85
What makes up the posterior iris epithelium?
Single layer of pigmented cells
86
What layer of the iris makes up the iris ruff?
Posterior epithelium
87
Aniridia has a high association with what disease?
Glaucoma
88
In Pigment Dispersion Syndrome (PDS), from where on the iris are pigment granules shed?
Posterior iris - midperiphery
89
Heterochromia, if not congenital, can be a sign of what?
Uveal inflammation
90
What is the refractive power of the lens?
20D
91
What is the diameter of the adult lens?
9.0mm
92
What is the lens capsule made of?
Basement membrane, produced by the anterior epithelium
93
What makes up the basement membrane that surrounds the lens?
Type IV collagen
| GAGs
94
What shape of epithelial cells make up the lens epithelium?
Cuboidal
95
What region of the lens contains mitotic epithelial cells?
Pre-equatorial
96
Which type of lens fibers continue throughout life?
Secondary lens fibers
97
What are the 3 types of lens crystallins, and where are they found?
Alpha
Beta
Gamma
Found in the lens fiber cytoplasm
98
What accounts for the gradient refractive index of the lens?
Crystallins
99
When an emmetropic eye is viewing at distance, is the ciliary muscle relaxed, or contracted?
Relaxed
100
When the ciliary muscle is relaxed, what happens to the lens zonules?
They are stretched, and un-accommodate the lens
101
When accommodating, what are the states of the ciliary muscle and the lens zonules?
Ciliary muscle is contracted
| Lens zonules are relaxed
102
Which photoreceptors primarily use retinal blur as a stimulus for accommodation?
Cones
103
What is the extent of the choroid?
Ora serrata to optic nerve
104
Where is the choroid the thickest? How thick?
Posterior pole
| 0.2mm
105
Where is the choroid the thinnest? How thin?
Ora serrata
| 0.1mm
106
What are the 4 layers of the choroid?
Suprachoroid lamina
Choroidal stroma
Choriocapillaris
Bruch's membrane
107
What is the suprachoroid lamina?
A potential space between the sclera and the choroidal vessels
108
Which layer of the choroid can swell without causing detachment?
Suprachoroid lamina
109
Which layer of the choroid carries the LPCA and LPCN from posterior to anterior?
Suprachoroid lamina
110
In which layer of the choroid can Haller's and Sattler's layers be found?
Choroidal stroma
111
What size of vessels are found in Sattler's layer?
Medium sized vessels
112
What size of vessels are found in Haller's layer?
Large vessels
113
The venules of what choroidal layer join to become vortex veins?
Choroidal stroma
114
What layer of the choroid has a high density of melanin granules?
Stroma
115
In what layer of the choroid would fibroblasts, macrophages, lymphocytes, and mast cells be found?
Stroma
116
Where is the choriocapillaris the most dense?
Macula
117
What provides local blood flow regulation in the choriocapilaris?
Pericytes
118
What is the innermost layer of the choroid?
Bruch's membrane
119
Bruch's membrane fuses with what?
RPE
120
What is the purpose of Bruch's membrane?
Allow nutrients to flow into the retina
| Remove waste products from the retina
121
Where to drusen deposit?
Between the inner collagenous layer of Bruch's and the BM of RPE
122
What is drusen?
A deposit of waste material from the RPE
123
What layer of the choroid is damaged by angioid streaks?
Elastic layer of Bruch's membrane
124
Angioid streaks are associated with what 4 systemic diseases?
Pseudoxanthoma elasticum
Ehler's-Danlos syndrome
Paget's disease
Sickle cell disease
125
Choroidal neovascular membranes (CNVM) result from a break in what?
Bruch's membrane
126
CNVM may be due to what 4 things?
Pathological myopia
Exudative ARMD
Histoplasmosis
Choroidal rupture
