Binocular Indirect Ophthalmoscopy

Question 1

difference between DO and BIO?

Answer 1

DO: image is upright, virtual, large with small field of view

BIO: image is inverted, real, small image with large field of view

Question 2

Condensing lens

Answer 2

• helps view aerial image of fundus
• mag dec. as power of lens inc.
• field of view inc. as power of condensing lens inc.

Question 3

Reasons for BIO (indications)

Answer 3

routine dilated exam flashes/floaters 
uveitis 
diabetes/vascular diseases 
trauma hx 
cancer
foreign bodies
peripheral vf loss
high myopia
systemic infections (HIV)

Question 4

contraindications for BIO

Answer 4

SAME as DILATION:

• narrow angles
• glaucoma - narrow angle
• iris fixed IOL
• subluxated lens or IOL
• need of clear vision

Question 5

3 ways for BIO mag: 1) linear

Answer 5

1. Linear (lateral) - mag fundus to image is proportional to ondensing lens

M = power of eye / power of condensing lens

Question 6

3 ways for BIO mag: 2) linear

Answer 6

2. Linear (lateral) - mag from image to observer is proportional to dist. which observer views image

M = (Deye/Dlens)(25/d)
where d = distance from which image is viewed

Question 7

3 ways for BIO mag: 3) axial mag

Answer 7

3. Axial mag (depth mag) = square of first linear mag –> determines effect on stereopsis

axial mag = (linear mag)^2 = (Deye / Dlens)^2

Question 8

Field of View for BIO

Answer 8

larger diameter of lens = larger field of view

vignetting can occur

Question 9

BIO Advantages?

Answer 9

good overview of retina during exam

• large field of view
• stereoscopic image
• high resolution
• brightness of image
• lack of distortion
• lack of sensitivity to RE
• access to peripheral retinal

Question 10

BIO disadvantages

Answer 10

• Learning difficulty
• dilation required
• length of exam
• brightness/discomfort for pt
• image orientation difficulties

Question 11

BIO filters

Answer 11

red-free (green): inc. contrast blood

cobalt-blue: enhance ONH drusen, use with fluorescein dye

yellow: protection and comfort, safe practices
diffuser: increasing and diffusing large spot

Question 12

BIO Clinic technique

Answer 12

• pupil dilation
• align pupil in light
• silver ring to pt
• line up purkinje images
• expand field of view by tromboning lens
• fill lens
• examine 8 cardinal positions of gaze

Question 13

Rocking rules

Answer 13

rocking toward the pupil = more posterior pole

rocking away from pt looking = more peripheral

Question 14

Patients at risk for prolonged bio

Answer 14

aphakes
pseudophakes
pt on photosensitizing durgs (ibuprofen, antibiotics, hydrochlorothiazide, statins)
children

Question 15

landmarks in fundus exam

Answer 15

• short ciliary arteries and nerves
• macula and fovea
• vortex vein
• optic nerve head
• long ciliary arteries and nerves
• vortex ampulla
• ora serrata

Question 16

Slit Lamp ophthalmoscopy

Answer 16

non contact: negative lens or aspherical lens (90 D)

contact: 3mirror, mainster lens, panfunduscopic lens

Question 17

Slit lamp uses

Answer 17

1. Evaluation of optic disc
2. evaluation of macula (esp. macular edema and diabetic retinopathy)
3. evaluation of vitreous cavity
   (esp. PVD, vitreoretinal adhesions/traction)

Question 18

SAFETY

Answer 18

20 lens (BIO) - 2.5 min

90 lens (SLE) - 52 sec

Question 19

scleral indentation

Answer 19

further in periphery, expose defects, vitreo-retinal profile