W2 Subjective Refraction and Recording Vision

What’s near vision blur with good distance vision?

Hyperopia/presbyopia

What’s good near vision with distant vision blur?

Myopia

What’s blur at all distances?

Hyperopic person becomes presbyopic or astigmatism

What do letters in the Snellen notation mean?

• Letter height subtends 5 mins of arc

• Letter limb subtends 1 min of arc

What should you do if the px cannot see the largest letter?

• Record distance which px can see your hand movement

• If not, hold pen torch at 50cm and ask if px can see light from a number of angles

• If yes, px has LP (light perception). If not, px has NLP

How do you calculate logMAR?

Switch the fraction, divide the numbers, log the value

When is pinhole used?

Reduced vision/VA, reduces ametropic blur by reducing pupil size

What does 6/12 NIPH mean?

Vision did not improve with a pinhole, visual defect is due to pathology rather than ammetropia

When is a slit used?

Locates principle meridian in an astigmatic/elderly eye with marked lens opacities

What do you ask when doing subjective refraction?

Is it clearer, more blurred, or the same

What do we do before JCC?

Add -0.25DS so the px accommodates slightly so image stays on retina

What do you ask during JCC?

Do the concentric rings look clearer, rounder or the same in 1 or 2

How do you adjust sphere and cyl?

For every -0.5DC you have to add +0.25DS