trial frame

Question 1

ocular findings in albinism

Answer 1

hypo pigmented RPE
foveal hypoplasia
nystagmus
strabismus

Question 2

a trial frame refraction is attempted to determiner the patients BCVA. What is the JND OS?

Dist VA (Feinbloom)

• OD: 10/140
• OS: 10/100

Near VA (lighthouse)

• OD: 0.4m/4M
• OS: 0.4m/3M

Answer 2

-2.00D

10/100=20/200
200/20=2.00D JND

you would show them +/-1D (total of 2D difference)

Question 3

Sphere lenses should be placed in which well of the trial frame during trial frame refraction?

Answer 3

back

Question 4

the cylinder power is checked during the trial frame refraction with the patient looking through -1.00 -0.25 x 180. The patient states the letters are clearer with the JCC lens when the red marking is parallel to the 180 meridian. What lenses should now be placed in front of the trial frame?

Answer 4

-0.50 -1.25 x 180

remember the maintain the spherical equivalent! (for every -0.50D of cyl power added to the refraction, add +0.25D of sphere power

Question 5

what is the definition of legal blindness in the US

Answer 5

cannot read any letters on the 20/100 line in the best eye or 20 degrees or less of VF diameter in the better eye

Question 6

the patient is RXed a 4X keplarian telescope. what are the signs of the objective and ocular lens, respectively?

Answer 6

positive, positive

Question 7

A keplarian telescope has a 20D ocular lens and a 5D objective lens. How much mag does it provide?

Answer 7

-4X

M=(-Foc/Fob)
M=-(20/5)
M=-4X

Question 8

the patient wants to use her 4X telescope to read her computer at 50cm. What power is required in a reading cap?

What is the total dioptric power providing by the keplarian telescope and the reading cap?

Answer 8

+2.00D

• power of the reading cap is the reciprocal of the patients working distance in meters
• 1/0.50m=+2D

+8.00D
-(+2)(4x)=8D

to find mag of the telemicroscope
8D/4=2X

Question 9

Galilean telescopes

Answer 9

• negative ocular, positive objective
• mag up to 4X
• shorter tube length and lighter weight
• exit pupil is located inside the telescope, leading to a reduce field of view
• upright image

Question 10

keplarian telescope

Answer 10

• positive ocular and objective
• higher mag
• longer tube length and heavier
• exit pupil located outside the telescope, leading to a larger FOV
• inverted image

Question 11

telescope labeling

Answer 11

YxZ
Y=mag
Z=diameter of the objective lens

5x20
5x mag
20mm objective lens

Question 12

exit pupil and markings on the telescope

Answer 12

E=d/M
d=diameter of the objective lens
M=Mag
E=exit pupil size

can also use Dent/Dex=M

Question 13

equations for tele microscopes

Answer 13

diopters
-Reading cap x magnification

Mag
-power (D) of telemicroscope/mag of microscope