Retinoscopy

Question 1

What is retinoscopy?

Answer 1

Objective way of determining refractive status

Emits light towards pupil of eye being analysed, and allows clinician to view red reflex of the light reflected back through pupil from ocular fundus.

Objective: to find far point of Px’s eye and shift plane of ret mirror by adding lenses in front of Px’s eye so that the far point and position of the mirror coincide.

Question 2

Indications

Answer 2

Objective first measure of RE
Non communicative Px (language barrier, stroke, etc.)
Intellectually disabled Px
Infants/pre-verbal children
Low vision Px
Uncooperative/poorly discriminating Px

Question 3

Other objective measures

Answer 3

Automated refractometers: expensive, variable accuracy due to accommodative control

Optometers (refractometers): historial/not clinically used

Keratometry/corneal topography: only corneal power/astigmatism

Question 4

What characteristics of the reflex gives information about Px’s prescription?

Answer 4

1. Direction of beam:
   ‘with’ = +
   ‘against’ = -
   Neither = NP
2. Brightness: increases closer to NP
   May be dimmer with opacities
3. Speed: increases closer to NP
   ±3D = speed very slow
   ±1.50D = speed of movement and reflex matches
4. Width:
   ±3D = width similar to pupil diameter
   Gets smaller and then enlarges again to infinity at NP
5. Orientation of beam

Question 5

Features of retinoscope

Answer 5

1. Rotatable illumination streak assists in determination of axis of astigmatic error
2. Rheostat to adjust brightness
3. Sleeve for divergent vs. convergent mirror

Question 6

Clinical application of retinoscopy

Answer 6

Static: used to quantify amount of ametropia objectively

Dynamic: investigate accommodative posture of eye in near vision (MEM)

Question 7

Clinical procedure of static ret

Answer 7

Align phoropter or trial frame on Px.
Place WD lens in BE, BE open.
Px fixates on D target (visible at all times), relax accom.
RE with RE.

Divergent beam
Quick sweep to determine direction, brightness, any astigmatism.
Align streak with principle meridian - neutralise most hyperopic/least myopic meridian
Instrument moved perpendicular to streak

Question 8

Relaxing accommodation in ret

Answer 8

WD lens
Contralateral eye fog
“Gaze into distance & make no attempt to see clearly”
Minus cyl trial lens to maintain fog during procedure
Cycloplegia (young, uncoopoerative Px)

Question 9

Potential problems

Answer 9

Undetectable initial reflex: large ametropia, move closer if suspect high myopia (but account for WD)

Undetected cyl: recheck alternate axes as you approach NP

Small pupils/media opacities: shorter WD inc. speed and visibility, however inc. error also

Split reflex: occurs with cycloplegia, spherical aberration, concentrate on centre of beam

Scissors reflex: irregular cornea

Excessive reflections

Incorrect WD

Viewing off axis (>5deg): oblique astigmatism, spherical, cyl & axis errors

Poor accommodative control

Failure to locate principle meridians and obtain reversal

Question 10

Moving closer or further from WD @ NP…

Answer 10

Closer = ‘with’

Further = ‘against’