Refraction

Author: Irina Kezika

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Case history

Patient’s personal details

Visual history

When patient will use his new glasses: concerning professional and leisure activities

Eye health: family history of eye problems, eye infections, eye surgery, vision trainings undertaken etc.

Patient’s general health: diabetes, high blood pressure, allergies, medications taken

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Case history

Reason of the visitNature of the problem: visual fatigue, blurred vision, double

visionLocation at which problem occurs: in far distance, mid-

distance, close-up, centrally, peripherallyThe circumstances in which the problem occurs: reading,

working at computer screen drivingThe time and frequency of occurrenceDate and mode of occurrence: sudden or gradual

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Objective Refraction

Auto-Refractometry (the sphere often over-minused, because of the stimulation of accommodation. Cylinder often over-estimated). The higher degree of ametropia, the greater the degree of imprecision.

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Objective Refraction

Retinoscopy (or skiascopy)

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Subjective RefractionDistance vision

Determining the sphere

- fogging method (reduce patient’s vision to the level 0,16)

Determining the cylinder

-

- Cross cylinder

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Subjective RefractionDistance vision

After determining the cylinder

- final check of sphere (+/- 0,25 D)

- with an extra +0,25D vision should be slightly reduced; if it is not add the +0,25D and repeat the checking of sphere

- with an extra -0,25D, vision should remain the same (or slightly reduced)

- duochrome test

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Binocular Balance

Dissociate the two eyes by:

- alternate occlusion

- vertical prism (3ΔBDR and 3ΔBUL)

- polarizing filters

Note which is patient’s dominant eye, a slight imbalance in favour of that eye may be conserved. Be careful never to reverse the natural dominance of one eye relative to the other

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Binocular Vision Evaluation

Evaluation of motor component:

Head position

Eye movements

Tropia and Phoria recognition

Hirschberg

Madox

Von Graefe

Cover test un Prism cover tests

Polarized cross test

Physional reserves

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Head position

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Eye Movements

Ductions : - adduction- nasal

- abcuction- lateral

- elevation- superior movement of one eye

- depression- inferior

Versions: - in 8 directions movement of two eye (conjunctive)

Vergences: - convergence

- divergence movement of two (disjunctive)

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Tropia and Phoria recognition

Cover test Prism Cover test

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Hirschberg

15°0° 30° 45°

Precise: 1°=1,75 1=0,57°

Aprox: 1°=2 1=0,5°

Light source

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Madox

orto esoexo

orto hipo (od) hiper (os)

Madox cylinder in fron of OD + light source

hipo (os) hiper (od)

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Von Graefe

+

5-6 pd base up in front of OD

os

od

exo eso

orto

Prism Light source

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Polarized cross test

Polarized glases + distance polarized test

Helps to evaluate phoria. Depending on the test conditions (type of dissociation) the phoria will be said to be associated or dissociated. Whether the test used involves the an element of fusion, perceived in common by both eyes or not.

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Physional reserves

Prism bar and fixation object

For divergence (have the patient focus on vertical line)

- base in prism blur/break/recovery

For convergence (have the patient focus on vertical line)

- base out prism blur/break/recovery

Vertical reserves (have the patient focus on horizontal line)

Sheard’s criteria fusional reserves opposing the phoria should be equal to at least twice the phoria for the phoria correctely compensated

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Binocular Vision Evaluation

Evaluation of sensory component:

Type of binocular vision:

Bagolini test

Worth test

Schober test

Stereovision:

Lang test

Titmus test

Polarized bar test

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Bagolini test

Binocular

MonocularMonocular alternating

Simultaneous

+ Light source

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Worth test or 4 dot test

Red-green filters + projector test

4 objects = binocular

3 objects = monocular (green filter)

2 objects = monocular (red filter)

5 objects = simultaneous

Either 3 or 2 (changing) = alternating

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Schober test

Red-green filters + projector test

Can be phoria test and type of binocular vision test (but will not show simultaneous type of binocular vision, because no physional stimulus)

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Lang test

Near distance stereopsis test

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Polarized bar test

Far distance stereopsis test

Polarized glases + distance polarized test

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Polarized bar test

Binocular and stereovision

No stereovision in far distance

direction of gaze

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Titmus test

Polarized glases + polarized test

Near distance stereopsis test

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Subjective Refraction. Near Vision

Minimum addition method

1. Correct distance vision precisely

2. Determine the minimum addition at 40 cm

3. Add +0,75D 0r +1,00D to the minimum addition

4. Check the patient’s visual comfort

- bring the test closer to the patient until the smallest characters are no longer able to be seen clearly. This should occur at approximately 25 cm from the eyes (if < 20 cm, the addition is too strong, if > 30 cm the addition is too weak.)

- adjust the value of addition (from 0,25D to 0,50 D) in accordance with required working or reading distance. If different from 40 cm at which the test was conducted. Reduce the addition for longer working distance, increase for shorter working distance.

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Verification of Binocular Balance at Near

Have the subject compare the vision of the right and left eyes and determine the balance:

- if there is equality of vision between OD and OS the balance is achieved

- if there is difference in vision between two eyes , balance by introducing +0,25DS on the worse eye or -0,25DS on better eye. Usually no more that 0,50D adjustment is necessary.

Remember about the dominant eye

Assess acceptance of near vision balance at distance

If the near vision balance differs from the distance balance, in general it is preferable to favour the near balance and check for that it is acceptable at distance.

Dissociate the patient’s binocular vision at near

- optoprox at 40 cm, gaze lowered (polarized or red-green filters)

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Amsler

Directions:1. Do remove glasses or contacts normally worn for reading.2. Distance 13 in/33 cm from the grid in a well-lighted room.3. Cover one eye say to the patient to focus on the center dotuncovered eye. Repeat with the other eye.4. If patient sees wavy, broken or distorted lines, or blurred or missing areasof vison, you may be displaying symptoms of AMD.

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In the Case of Non-Presbiopic Patient

1. Uncorrected ametropia ( hypermetropia, astigmatism)

2. Binocular vision disorder (convergence insufficiency, severe heterophoria)

3. Accommodative problems:

- excess/spam (low NRA , ok PRA, low AA)

- insufficiency (not corrected myopia, low PRA, low AA)

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Prescribing prism

Minimum value of the prism that restores comfortable fusion

Prefer trial frame rather than phoropter

Consider associated phoria tests and dissociated

Distribute most of the prism value on non dominant eye (aberration)

Remember decentration rule P=d(cm)xF(D)

Follow up visits each 0,5 year

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Referrences

Essilor. Ophtalmic and Optics Files. Practical Refraction.

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Thank you!