Questions I got wrong Flashcards
What is the lens that makes up the 0.50 Jackson cross cylinder?
+0.50 DC / -1.00 DS
What percentage of incident light is scattered by the cornea?
10%
This increases in corneal oedema and causes reduced visual acuity
Is diffraction greater at shorter or longer wavelengths?
Longer wavelengths
Pinhole improves ametropia of up to how many dioptres?
4D
What is the power of a concave mirror of radius 10cm?
Power = 1/f = 2/r
= 2/0.1
= 20D
What is the angle of minimum deviation of a crown glass prism with apical angle of 4 degrees?
Angle of minimum deviation = (RI - 1) x apical angle
= (1.5-1)(4) = 2
Where in the retina are hard exudates located?
Outer plexiform layer. Pathophysio = leakage of plasma from the inner blood-retinal layer
When doing keratometry, what does each step on a Javal-Schioltz keratometer correspond to?
1 dioptre
When doing keratometry, the power of the cornea is equal to 337.5 / (length of cornea in mm)
Yes
What sort of image is produced by a panfundoscope?
Real inverted image
What growth factor stimulates the differentiation of lens epithelial cells into secondary lens fibres?
Fibroblastic growth factor (FGF)
What is the trigger for shedding of rod photoreceptors?
First light
How long does it take for the outer segment of a rod cell to undergo complete turnover?
10 days
At what gestational age does myelination of the optic nerve start?
7 months (complete at 1-3 months post birth)
What is the principal DNA polymerase used in mitochondrial DNA replication?
DNA polymerase gamma (POLG gene)
What is the inheritance of Leber’s hereditary optic neuropathy and Kearns-Sayre syndrome?
Mitochondrial inheritance
Is HLA-B27 an MHC I or MHC II molecule?
MHC I
What are the roles of MHC I and MHC II molecules?
MHC I: expressed on all cells of the body, present intracellular antigen, recognised by CD4 T cells
MHC II: expressed on antigen presenting cells, present soluble antigen, recognised by CD8 T cells
What is the approximate volume of the orbit?
30mL
What are the 3 actions of the inferior oblique?
Extorsion, abduction and elevation
Does the superior ophthalmic vein pass within the common tendinous ring?
No
Which of the EOMs assumes a fusiform shape?
Superior oblique
Is the anterior or posterior lens surface more convex?
Posterior (6mm radius of curvature compared to 10mm)
What is the diameter of the lens?
10mm