Objective, subjective and cyclopegic refraction

$: Objective, subjective and cyclopegic refraction$
Objective, Subjective and Objective, Subjective and Cyclopegic refractionCyclopegic refraction

Objective, Subjective and Objective, Subjective and Cyclopegic refractionCyclopegic refraction

Gauri S Shrestha, M.Optom, FIACLE

Lecturer and Optometrist


Objective refractionObjective refractionObjective refractionObjective refraction

• Examiner determines the refractive state of the eye on the basis of the Optical Principles of refraction.

• Purpose: To obtain an objective measurement of the patient’s refractive state.

• Example– Keratometry

– Retinoscopy

– Optometers

– Auto refractometer


RetinoscopyRetinoscopyRetinoscopyRetinoscopy

• Static retinoscopy– To determine refractive state by patient fixating at distance

so that accommodation is at rest

• Dynamic retinoscopy– To determine refractive state by patient fixating at near,

accommodation is active.

• Principle: – Estimate the patients refractive state by bringing patient’s

far point at the entrance pupil of examiner with the help of appropriate lens.

– The state of refraction at this particular point is called as neutralizationneutralization.


ProcedureProcedureProcedureProcedure

• Working distance

• Fixation target

• Patient instructions

• Starting point

• Locating principal meridian

• Procedure for spherical ametropia

• Procedure for astigmatism


Principle of subjective refractionPrinciple of subjective refractionPrinciple of subjective refractionPrinciple of subjective refraction

• Subjective determination of the combination of sphere and cylindrical lenses that artificially places the far point of Each Eye of patient at infinity

• This is the combination of lenses that provides best VA with accommodation relaxed


PurposePurposePurposePurpose

• To find the strongest plus lens or the weakest minus lens which allows the patient to obtain the best possible visual acuity


When to start subjective refraction?When to start subjective refraction?When to start subjective refraction?When to start subjective refraction?

• After objective retinoscopy/Auto refraction

• Accurate refining when objective retinoscopy is inaccurate– Media opacities, keratoconus, oblique and

irregular astigmatism

• Post mydriatic cycloplegic refraction

• When retinoscope or auto-refractor is absent


Subjective refraction techniquesSubjective refraction techniquesSubjective refraction techniquesSubjective refraction techniques

• Fogging

• Stenopaic slit

• Jackson’s cross- cylinder


Subjective refraction techniquesSubjective refraction techniquesSubjective refraction techniquesSubjective refraction techniques

• Astigmatic fan/ Clock dial/ Sunburst dial

• Phoropter


The sequence of the subjective The sequence of the subjective refractionrefraction


• Monocular sphere check– The Step-Down Technique (Visual acuity method) for

monocular sphere check– The Red-Green Technique for monocular sphere check




• Astigmatism power and axis– Jackson Cross Cylinder

– poweraxispower

– If the power of cylinder is 1.00 diopter or more

• Axis check

• Power check

• Note: Add constant spherical equivalent




Clock DialFan chart




• Monocular sphere endpoint– The Step-Down Technique for monocular sphere

check– The Red-Green Technique for monocular sphere

check

– Note: Perform monocular visual acuity test


Binocular BalancingBinocular BalancingBinocular BalancingBinocular Balancing

• Purpose: – Equalize accommodation between the 2 eyes

• Method– Prism dissociation technique– Prism dissociation bichrome balance– Alternate occlusion technique

Final Fused Binocular Sphere Power DeterminationFinal Fused Binocular Sphere Power DeterminationFinal Fused Binocular Sphere Power DeterminationFinal Fused Binocular Sphere Power Determination


Difficulties with Subjective Difficulties with Subjective Refractive TestingRefractive Testing

Difficulties with Subjective Difficulties with Subjective Refractive TestingRefractive Testing

• Intelligence

• Cooperation

• Past experience

• Poor JND ability

• Language barrier


Principle of cycloplegic refractionPrinciple of cycloplegic refractionPrinciple of cycloplegic refractionPrinciple of cycloplegic refraction

• Determination of total refractive error during temporary paralysis of cilliary muscles as an instillation of cycloplegic drugs which otherwise doesn’t manifest on subjective non-cycloplegic refraction

Total HyperopiaTotal Hyperopia

Latent hyperopia

Manifesthyperopia

facultativehyperopia

Absolutehyperopia


Indication for cycloplegic refractionIndication for cycloplegic refractionIndication for cycloplegic refractionIndication for cycloplegic refraction

• Accommodative esotropia

• All children younger than 3 yrs

• Suspected latent hyperopia

• Suspected pseudomyopia

• Uncooperative/noncommunicative patients

• Variable and inconsistent end point of refraction


Indication for cycloplegic refractionIndication for cycloplegic refractionIndication for cycloplegic refractionIndication for cycloplegic refraction

• Visual acuity not corrected to a predicted level

• Strabismic children

• Amblyopic children

• Suspected malingering and hysterical patients


Selection and use of specific Selection and use of specific cycloplegic agentscycloplegic agents

Selection and use of specific Selection and use of specific cycloplegic agentscycloplegic agents

• Variable degree of pupil dilatation and cycloplegia• Instill cycloplegic alone or with mydriatrics

Agent [C%] Dosage Max cyclople

Duration of effect

Residual accom

Atropine sulfate

1, 2 1D TID 3 days

3-6 hrs 10-18 days

Ngble

Sco-mine HBR

0.25% 1D TID 60 mins 5-7 days ngble

Cyclo-late HCL

0.5, 1, 2 1D TID 30-45 mins

24 hrs minimal

Tro-mide HCL

0.5, 1 1D TID 20-30 mins

4-8 hrs moderate


Cyclopentolate HClCyclopentolate HCl is the drug of is the drug of choice in most of the timechoice in most of the time

Cyclopentolate HClCyclopentolate HCl is the drug of is the drug of choice in most of the timechoice in most of the time

• Use 1% [C] in children and adult,• Use 0.5% [C] in infants in combination with 2.5%

phenylephrine

Age (Yrs) Amount deduced

0-6 1.00 DS

10 0.75 DS

15 0.50 DS

20 0.25 DS

30 0-0.25 DS

40 0 DS


What does our practice say?What does our practice say?What does our practice say?What does our practice say?

• Advise atropine cycloplegic refraction invariably in the children younger than 2 years

• Advise atropine cycloplegic refraction in esotropic children (accommodative type) up to 4 years

• After 4 years, advise cyclopentolate cycloplegic refraction up 25-30 years

• Above 30 years, check amplitude and lag of accommodation, then advise cycloplegic refraction


Spectacle prescribingSpectacle prescribingSpectacle prescribingSpectacle prescribing

• Prescribing spectacle from cycloplegic finding is an art rather precise science

• How to prescribe spectacle? – Concept of emmetropization is necessary– Esotropic children younger than 4 years, full

refractive correction is prescribed– With older children, amount of plus can be

reduced till fusion is maintained

Objective, subjective and cyclopegic refraction

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