Reading up close Flashcards
threats to vision in wet AMD
sub retinal heme
subRPE heme
sub retinal detachment
subRPE detachment (PED)
if someone is a smoker, what is there likelihood of recurrence of a CNVM?
1.7-2.2x more likely
what magnification is required in a telescope in order for the patient to watch TV with 20/40 print?
BCVA dist
- OD: 20/120
- OS: 20/120
SUBJ
- OD: +1.00Ds
- OS: +1.00Ds
3x
want/need
120/40=3x
the pt is Red +6.00D readers. How much BI prism is required
8 BI each eye
what M print size represents standard newspaper print size?
1M
this patient can read 4M letters on the Lighthouse near card at a test distance of 40cm. How is the near VA recorded by convention?
.4m/4M
that patient moves the near acuity card to a test distance of 10cm. what print size should he be able to read at this distance?
1M
RDM
Dold/Dnew=.4/.1=4x larger
the patient was shown a CCTV to help him read his mail. what type of magnification is this?
Relative size magnification
how much mag is provided by a +12D HHM when it is used as a collimating magnifier at a distance of 25cm
3x
M=Fd
M=(12D)(.25)=3x
prism and high add powers
high plus readers with a power off +4D or higher require BI prism bc the high plus lenses result in a high convergence demand at near. The required amount of prism PER EYE is the dioptric power of the lens plus 2
11M subtends ___arcminutes at one meter
5
1M= what snellen
20/20 at 1m
20/50 at 40cm (newspaper size)
E on the 20/20 line
subtends 5 arc minutes, has 5 components, thus, each line within the E subtends 1 arc minute at 1 meter
1M at near
when a 1M letter is viewed at 40cm, the acuity will decrease by a factor of 2.5X because the distance has decreased by 2.5X (1m/0.4m). Thus, reading a 1M letter at 40cm requires a MAR of 2.5, which is appx the same as 20/50 vision (20 x 2.5=50)
relative size magnification
due to the change in actual size of the object WITHOUT a change in the distance of the object from the patient
-a CCTV, large print book, enlarging reading material with a copier are examples
best reading option for someone with advanced visual impairment
CCTV
collimating magnifier
when a plus lens is positioned so that the object that is being viewed is located at the primary focal point of the lens, and parallel like leaves the lens. the magnification of a collimating (often HHM) magnifier is give by M=Fd
DOES NOT need an add or accommodation
non-collimating magnifier
stand magnifier
-the object is inside the focal length of the lens, resulting in divergent light leaving the lens. The patient must accommodate or use an add in order to see the object clearly. The max magnification provided by a stand magnifier is a combination of the original mag of the lens + additional mag provided by accommodation, resulting in the equation M=F/4 +1
this is sometimes called conventional mag
Need an Add or accommodation
