SubjectiveRefraction

What is Refraction?■ Determination of the refractive status

(prescription) of the eye.

OBJECTIVE

RetinoscopyAutorefraction

SUBJECTIVE

Subjective RefractionPhoropter

Epic

Subjective Refraction■ To determine by subjective means the

combination of spherical and cylindrical lenses necessary to to provide best visual acuity.

■ (with accommodation relaxed)

Principles of Refraction

1. Accommodation-relaxed state2. Maximum PLUS, minimum minus

Principles of Refraction

When can we ignore accommodation?

How can we be sure accommodation is relaxed?■ Use PLUS lens to FOG■ Ensure image is located in front of retina

■ This causes image / VA to become worse if eye attempts to accommodate (Image point becomes further away from the fovea)

Two sets of commonly used instruments

Start from Auto-Ref Results (OD)

1. Best Vision Sphere

2. Jackson Cross Cylinder

3. Best Vision Sphere

Repeat 1-3 on OS

4. Binocular Balancing

5. Binocular Best Sphere

OU

Steps in Subjective Refraction

Fogging

■ Place enough PLUS lenses to FOG vision to 20/40 line■ Pointer: every line is about 0.25 diopter

■ Slowly reduce the plus power until best vision

■ Remember:“Maximum plus power for best visual acuity”

Astigmatism

Step 2: Jackson Cross Cylinder

■ JCC used to find used to determine the cylindrical axis and the cylindrical power for the patient.

Yes, we have th

ese!

Step 2: JCC

■ JCC used to find used to determine the cylindrical axis and the cylindrical power for the patient.

How can we be sure accommodation is relaxed?■ Use PLUS lens to FOG■ Ensure image is located in front of retina

■ This causes image / VA to become worse if eye attempts to accommodate (Image point becomes further away from the fovea)

Cylinder Power

■ Patient directed to observe a round target■ Align red lines OR white lines to trial lens axis

Cylinder Power■ If view one is clearer, ADD +0.25 cylinder power

Steps in Subjective Refraction

Start from Auto-Ref Results (OD)

1. Best Vision Sphere

2. Jackson Cross Cylinder

3. Best Vision Sphere

Repeat 1-3 on OS

4. Binocular Balancing

5. Binocular Best Sphere

OU

Fogging like before...

■ Use PLUS lens to FOG■ Ensure image is located in front of retina

■ This causes image / VA to become worse if eye attempts to accommodate (Image point becomes further away from the fovea)

What about for reading?

I'm over 40 years old and I can't read my phone. What's that from?

Near Addition■ Presbyopic

patients would require a near addition for their reading.

Finding the Near Addition■ Step 1: Estimation from patient’s age

+ 1.00

+ 1.50

+ 2.00

+ 2.25

+ 2.50

40 - 45

46 - 50

51 - 55

56 - 65

65+

Age Estimated Add

Finding the Near Addition■ Step 2: Place the estimated near addition on

top of the distance prescription

■ Step 3: Put near chart at 40 cm or 16” on near point rod and attach to phoropter.

Finding the Near Addition■ Optional stuff after this!

Range of clear vision

20CM 60CM

40CM

■ Patient’s habitual reading distance in the middle of the range of clear vision.

Range of clear vision

10CM 50CM

40CM

■ If range is too close to patient: Add-0.25DS insteps

Range of clear vision

30CM 70CM

40CM

■ If range is too far to patient: Add+0.25DS insteps