Dr. Dimple PrakashHead Post Graduate Training Programme

SHADOW PLAY - RETINOSCOPY

MyopiaHyperopia

Astigmatism

in case of Welsch Allen retinoscope when the lens is pushed down the

mirror acts like a plane mirror and the rays are divergent.

Plane Mirror Retinoscopy

When the lens is pushed up the mirror acts like a concave mirror so the rays are

convergent.Practical importance : in plane mirror

retinoscopy a with movement will need + lenses but in concave mirror retinoscopy

a with movement will need – lenses.

Concave Mirror Retinoscopy

Illumination Stage Reflex Stage

Projection Stage

Illumination

• Rays are from S1

• Image is at far point of subject

• Shadow at pupil of subject

• Projected to the examiner

Normal Eye

+1.50

66 cm

Hyperopia (Small Eyes)

+58 D

Myopia (Large Eyes)

+62 D

StreakStreakRetinoscopyRetinoscopy

Break :

Width : Narrowest when allingned with true axis

Intensity : Brightest when along with true axis

Skew : When axis is not assigned reflex breaking into two

Low Errors High Errors

Speed High Low

Brilliance Bright Dull

Width Wide Narrow

Neutralization point : complete illumination of entire pupillary area.

Swirl

Checking axis : Swirl 2.00DC @ 80

Add 45 degrees = 125

Minus 45 degrees = 35

Keep the streak at 125 and 35

Note the width : should be equal

Side that is less : change axis

slowly towards wider side.

WAKE UP

GROSS NET

Power of lens that is held in front of the examined eye at which neutralization occurs

Following subtraction of distance and cycloplegic drops

Distance Subtraction Cycloplegic

1 mt = 1 D

2/3 mt = 1.50 D

Atropine = -1.00 D

Homatropine = -0.50 D

Cyclopentolate = -0.75 D

Example Distance (lm) Atropine+6.00 DS +5.00 DS +4.00 DS

Few Algebraic rules for signs of Cylinders

- - = + - 6.00 - 4.00 = - 2.00

- + = + - 6.00 + 4.00 = - 10.00

Practice Situations

Net + 6.00

+ 4.00

Lower Value = Sphere = +4.00

Difference = Cylinder = +2.00

+ 4.00 - +6.00 = - Sign of cylinder

Axis at lower value = 180°

+ 4.00 DS / -2.00 DC @ 180° Axis

Net - 6.00 DS

- 4.00 DS

90° Axis

180° Axis

* Lower value here is – 6.00 DSThe rest is the same

- - = +- 6.00 DS / +2.00 DC x 90° Axis

- 8.00 DS

- 10.00 DS

- 10.00 / +2.00 DC x 180° Axis

Sample Transpositions- 2.00 DS / -4.00 DC x 180° Axis

1. Allegebric sum of the sphere and cylinder- 6.00 DS

2. Change the sign of the cylinder- 6.00 DS / +4.00 DC

3. Change the axis if above 90° = minus 90 if below 90° = add 90

- 6.00 DS / +4.00 DC @ 90 ° Axis

WAKE UP

RefinementRefinementofof

RefractionRefraction

Methods Easiest : fogging. Over refraction,

over retinoscopy

Duchrome testing

Jackson cross cylinder

Astigmatic dial

Astigmatic fan and block

Jackson Cross Cylinder Components: sphere

Cylinder

Power: ½ that of cylinder

Axis of Cylinder : 2 are perpendicular to each other

Handle: 45 degrees always.

How it works?

Axis first: handle in direction of the cylinder in the frame already. Eg) 2.00DC at 180 then keep handle at 180

Va chart 2 lines above least visible. eg)6/12 if BCVA is 6/6.

Flip + 0.50 or – in front of patient.

At best vision point, rotate the DC by 10 degrees towards the red mark in case of – and towards white mark in +.

E.g.) DC in trial frame= +2.00DC @ 180

BCVA CLEAR when +0.50 DC is in front

Rotate 10 degrees towards white mark

+2.00 DC@ 170.

Power of DC. This is easy.

Keeping the correct axis. Flip the JC by + or – and then add or subtract the correct power.

E.g.) DC in trial frame = +2.00,Va better at +0.50 DC then final value= +2.50 DC.

If equal Va at 2 flips: correct power.

How it works?WAKE UP

Summary

Most plus or least minus sphere: BCVA

Va chart 2 lines above least visible. eg)6/12 if BCVA is 6/6.

No cylinder, still flip at 90,180,45,135.

Axis first : Why?

Lower powers 0.25 for 20/30 Va .Flip + 0.50 or 1.00 for lower visions : Why?

Duchrome

Chromatic aberration

Duchrome Normal : both equal Start with Red slightly better Focus on the letters

Hyperope of +5.00 sees green better, increase to +5.25 D so sees red better.

• Increasing the converging power so that “STRONGEST + LENSES “ are given. (asthenopia)

P ON F

T EA K

Myope: - 5.00D sees red better leave him alone

-5.00 D sees green then – 4.75 D get the rays in front.

• “WEAKEST (– )LENSES”

P ON F

T EA K

Astigmatic dial technique

Fogging

Indications : Young: Recurrent Asthenopia: H/O Squeezing / frowning: Difficulty in near work

(E.g.) Needle work, Microscope

Reference Chart :If we start pt +20.00 DS upto +16 D: Decrease in lens in strengths of +2.00 DS

(E.g.) +20.00 D = Next lens + 18.00 DS

+16 D TO +12/10 D: Decrease in strengths of 1.00 DS (E.g.) +10.00 +9.00 DS, +8.00 etc

Upto (+6.00 DS. From then upto +4.00 DS : +0.50 DS decrease+5.50, +5.00, +4.50 etc

Giving Glasses

Giving Glasses

Hyperopia

Age

Fogging

Refinement methods

1) Less than 3 years = Full retinoscopic correctionEg; +4.00 DS = Give + 4.00 DS

2) 3 to 8 yearsPresence of tropia

Presence of phoria

Esotropia = Full gross value subjective to AC/A ratio

Phoria = Full net optimal, under correction

Eg. Net Value

+4.00 D in phoria = +3.50 / +3.75 which is accepted

3) Adults follow : rule of strongest +

0 1 2 3 4 5 6 7 8 9 10 11 12 YRS

HM 6.50

6.00

5.50

5.00

4.50

4.00

3.50

3.00

2.50

2.00

1.50

1.00

HyperopiaCorrection

with Age

Giving Glasses : MYOPIA

Thumb rules Normal patients

1) From -1.00 to -6.00 DS : Full correction

2) Above -6.00 DS : Under correct to meet subjectiveness

Esotropia

High presence of -6.00 DS and above are under correctedmeet acceptance followed by optimal to full correction

ExotropiaOver correct in intermittent EXOTROPIAS

Giving Glasses : Astigmatism

Normal patients

: In a child less than 3 years = 1.25 DC, Regular

: Older than 3 years = all astigmatism to be corrected

• Child : follow-up 6 months• Adult yearly• Frequent change : over correct (0.25 D)

WAKE UP

Giving glasses: child Ideal frame: large, sturdy, well

balanced Ideal lenses: plastic, polycarbonates Ideal refraction: Less than 3 years: solely on

retinoscopy All strabismus : retinoscopy Beyond 3 years: myopes do not need

Cycloplegic studies Rosenbaum and associates: atropine

estimation of hyperopia 0.34 D more as compared to homatropine

Hurol et al: no difference between 2 and 3 days of cycloplegia

Stolovich: 8 instillations vs 4 instillations.

Bifocals

Bifocals Working distance

0.2 m wide or smallest test type

Blurred/ not readable = near point

No doubling

Keep 1/3rd reserve

Tips on bifocals

Keep 1/3rd reserve

Undercorrect

Full correction 23 mm of near point max (3.5D)

Prisms for convergence thereafter

Practical Tips

Do Don't

Read Previous prescription

Bifocal to progressive

Adjust sphere firstE.g.) +1.25 DS / -0.75 DC

Change to +1.75 to +1.50

Don’t make drastic glass changes from past “Suspicion”

progressive to Bifocals

Do not try to change to higher astigmatism+1.25 DS / -1.25 DC

Practical Tips

Do Don't

4. Try to correct the axis rather than the number

Eg) -0.75 DC @ 90° Axchange to -0.75 DC @ 100° Ax rather than -1.00 DC @ 90° Ax

Final Example-1.25 DS / -0.75 @ 80° Ax

(a) -1.50 DS / -1.75 DS with -0.75 DC @ 80° Ax

(b) -1.25 DS / -0.75 DC @ 90° Ax (c) -1.25 DS / -1.00 DC @ 80° Ax

-1.50 DS / -1.50 DC @ 80° Ax

Make the right choice

Low powers : smile and bye bye

High plus: think!Chromatic aberrationsprismatic aberrations

High index lenses: 1.6 and 1.74

Thinner, flatter, lighter +4.00 D = high index

Gets higher : plastic lenticular lenses Aspheric lenses : curves that flatten

away from the center. Prismatic effects

Myopes: higher powers -4.00 above 1.6 high index

-7.00 D above : 1.7 high index.

Power refraction you are now armed

Retinoscopy

Interpretation of numbers

Giving glasses

Refinement of numbers

What not to do

Dr. DIMPLE PRAKASHSenior Consultant

Pediatric and SquintHead Post Graduate Training Programme