refraction
DESCRIPTION
Autorė: Irina KezikaTRANSCRIPT
Refraction
Author: Irina Kezika
Page 2
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
Page 3
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
Page 4
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.
Page 5
Objective Refraction
Retinoscopy (or skiascopy)
Page 6
Subjective RefractionDistance vision
Determining the sphere
- fogging method (reduce patient’s vision to the level 0,16)
Determining the cylinder
-
- Cross cylinder
Page 7
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
Page 8
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
Page 9
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
Page 10
Head position
Page 11
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)
Page 12
Tropia and Phoria recognition
Cover test Prism Cover test
Page 13
Hirschberg
15°0° 30° 45°
Precise: 1°=1,75 1=0,57°
Aprox: 1°=2 1=0,5°
Light source
Page 14
Madox
orto esoexo
orto hipo (od) hiper (os)
Madox cylinder in fron of OD + light source
hipo (os) hiper (od)
Page 15
Von Graefe
+
5-6 pd base up in front of OD
os
od
exo eso
orto
Prism Light source
Page 16
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.
Page 17
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
Page 18
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
Page 19
Bagolini test
Binocular
MonocularMonocular alternating
Simultaneous
+ Light source
Page 20
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
Page 21
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)
Page 22
Lang test
Near distance stereopsis test
Page 23
Polarized bar test
Far distance stereopsis test
Polarized glases + distance polarized test
Page 24
Polarized bar test
Binocular and stereovision
No stereovision in far distance
direction of gaze
Page 25
Titmus test
Polarized glases + polarized test
Near distance stereopsis test
Page 26
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.
Page 27
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)
Page 28
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.
Page 29
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)
Page 30
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
Page 31
Referrences
Essilor. Ophtalmic and Optics Files. Practical Refraction.
Page 32
Thank you!