Last Minute Optics

kuleya's version from 2016-03-09 06:20

part 1 and 2

Question Answer
distance from secondary focal point of eye to nodal point?17 mm
distance from nodal point to focal plane of model eye?5.5 mm
potential acuity meter showed what?if someone could see after cataract surgery
what is minimum resolvable acuity?1 minute of arc
what is minimum visible acuity defined as?recognizing an object on wall.. 10 sconds of arc
what is definition of vernier acuity?ability to determine if a straight line is broken
20/20 E subtends what amount of angle?5 minutes
20/200 E subtends what amount of angle?50 minutes
when can you use OKN?6 wks
when do kids fix and follow?3 months
Define far point?point where light converges after being projected from inside eye
Where is far point in myopia? in front or front
Where is far point measured from?cornea
where do you place a lens to correct myopia/hyperopia?at point where far point and focal point meet
moving a plus lens toward eye does what to effective plus power?decreases…need more as you get closer…for aphakic a 15D CL is cool but a 20D IOL is used
Absolute hyperopia is whatleast amount of plus power needed to correct at distance
Manifest refraction is what?most plus the eye can accept without blurring
Facultative refraction is what?difference between absolute and manifest
Latent refraction is what?difference between manifest and cycloplegic
astigmatism is with the rule if within what degree of 90?20 either way
spherical aberration is what?when peripheral rays are refracted more strongly than paraxial rays…~most common in biconvex lens
What should be correction for patient with K1 40 at 30 and K2 46 at 120?-6 at 30
RK did what to cornea?steepen periphery flatten the center
starburst at night is caused by what?RK
scatter at night is caused by what?lasik
what can help prevent multifocality in refractive surgery?larger optical zone
coma is what?off centered treatment directs light to the side
SRKII a constant changes how?short eyes – Add 3 to A contant for AL <20, Add 2 for AL 20-21, add 1 for AL 21-22..long eyes subtract 0.5 from A constant for AL > 24.5 mm
how long before keratometry do you need to remove hard contact lens?at least 2 hrs
where are there errors in SRK? amount of damage per unit of error in K and AL?1D = 1D keratometry, axial length 1 mm error = 2.5 D error
SRK formula for IOL power?A (A constant) – 2.5 xL (length in mm) – 0.9 K (keratometry in diopters)
SRK is empirical or theoretical?empirical

part 3 and 4

Question Answer
minus lenses in aniseikonia is changing image size how?minify
plus lense in aniseikonia is changing image size how?magnify
kestenbaums rule is what?used to estimate strength of plus lens required ot read newpaper print without accommodation
advantage of high add spectacles? disadvantage? large field of view…(short reading distance…expensive)
advantage of handheld/stand magnifiers?variable eye to lens distance, portable…stand are good for arthritis and tremor…disadvantage is small field
what is magnicam?point a camera and it shows up at tv
absorptive lenses help in what diseases?albinism, congenital achromatopsia, ARMD….. glare control
how do you fix vertical deviations from prentice shit?slab off, contact lenses, lower the optic center
Worse image jump in what?round top > flat top > executive = progressive
Flat top axts like what?base up
Round top acts like what?base down
blue bends where?down
night myopia caused by?dilation (spherical aberration), patient is overcorrected..(add -0.25 to glasses), lower light levels (photoreceptors more sensitive to blue, add minus), overaccomodation in dark
Aphakic spectacles have what problemsprismatic effect causing ring
in contact lenses vergence is greater from near target is greater after entering eye through minus or plus lens?minus…opposite is true for hyperopes in glasses
which has more distortion – plus or minus cyl?minus
manual K refractive index assumption in cornea?1.335
where do you you place the applanation tip in oblique astigmatism to get most accurate iop?minus cyl axis
goldmann contact lens is what power?-64D
operating microscope is what kind of system?galillean
what is PD of small pupil indirect?smaller – 15
aerial mag = what?power of eye / power of lens
blue green absorbed by what in photocoag?RPY, xanthophyll, iris and hemoglobin
red is absorbed by what?melanin no Hb or xanthophyl
yellow absorbedrpe
diode 815 nm burns what?RPE
photodisruotionplasma formation and shockwaves… optical breakdown 1064
which thing causes sublimation?photoablation excimer laser (163)