RETINOSCOPY

By: Vineela.Ch 11IMMO07 I.M.Sc OVS

Is an objective technique for the investigation, diagnosis and evaluation of the refractive errors of the eye.

Work by utilising the natural optics of the eye to determine the refractive error.

In retinoscopy the fundus acts as a fixed screen

over which a spot of light is moved.The practitioner watches the shape and movement of the patch of reflected light within the pupil(the reflex) and by placing trail lens in front of patient’s eye, modifies the speed of movement of reflex to arrive at a particular condition called reversal.

Retinoscopy

History of retinoscopy

Cuignet 1873 first description and utilising a retinoscope AJ Cross 1902 teaching a course in it

Greet 1895, Axenfeld, Heine & Hess 1898

Original work on dynamic retinoscopy

Retinoscope and its parts

Retinoscopy consists of a Head,Neck and Tail. Observing the optics of retinoscope we find two main systems - Projection system: Light source Condensing lens Focusing sleeve Current source - Obsevation system: Peep hole

Retinoscope and its parts• Bulb projects a streak of light.• Resting in the light path is the lens focuses the rays onto mirror which bends

the path of light at right angles to the axis of handle.• Focusing sleeve controls• Meridian:Turning the sleeve rotates the streak of light.• Vergence:By varrrying the distance between the lens and the bulb• Bulb: Moved up-Plane mirror effect(Parllel rays) Moved down-Concave mirror effect(converging rays)• Lens: Moved up-Concave mirror effect Moved down-Plane mirror effect• The light rays illuminate(Pigment epithelium and choroid) of retina and retinal

reflex is seen through the peep hole.• The rays emerging from retina are acted upon by the optical components of

eye and they tell’s about optics of petient eye.

Hold the scope in your dominant hand before your dominant eye.Keep both the eyes open and lights low.Hold the scope against your brow and wiggle it perpendicular to the streak axis.

Far point concept

• The far point of eye is defined as the point in space that is conjugate with the fovea when accomodation is relaxed.

• Emmetropia: Parallel rays focus on fovea.• Retina conjugate with infinity.• Far point is at infinity.• Ammetropias:Parllel rays do not focus on retina.• Ammetropic eyes require a correcting lens to make retina conjugate

with infinity, ie, to move far point to infinity• Hyperopia:Deficient refractive power.• Parllel rays focus behind retina.• Far point is beyoned infinity.• Plus lens converges rays on to retina and conjugate fovea

with infinity.

Far point concet

• Myopia: Excessive refractive power.• Parllel rays focus infront of retina.• Far point is between infinity and eye.• Minus lens diverges rays on to the retina and

conjugate fovea with infinity.• Aspherical ammetropias:• This indicates different types of astigmatism.• This type of errors have two two far points.• As a set of rays coverge at one place and other at different

place due to cornea not having same radius of curvature in all the meridians.

Retinoscopy Techniques

• Two main techniques of retinoscopy are• Static Retinoscopy:• It is the refractive state determined when

patient fixates an object at a distance of 6cm with accomodation relaxed.

• Dynamic Retinoscopy:• The refractive state is determined while

the subject fixates an object at some closer distance, usually at or near the plane of retinoscope itself with accomodation under action.

Retinoscopy Techniques

• Static Retinoscopy include Spot retinoscope: Light scource is

spot of light.

Streak retinoscope: The bulb is constructed so that is provides a beam in the form of a streak rather than a spot.

Retinoscopy Techniques

The modern retinoscope differs in 2 aspects: It incorporates a concave mirror in addition to plane

mirror.The light source is in the form of streak rather than

spot. Mirrors BeamsConcave mirror Covergent beam (most frequently used) Convex mirror Divergent beam Plane mirror Parallel beam

When using “parallel” or “divergent” beam,

“Against” movement - myopic - neutralizes

with minus lenses “With” movement – hyperopic - neutralizes

with plus lenses.

When using “convergent” beam - opposite

Streak retinoscope

• It incorporates both plane and concave mirror.The orientation of streak across the patients face is

always at right angles to the meridian eye being scoped.

• Thus – When scoping the vertical meridian the examiner moves the instrument vertically with streak oriented horizontally.

• -In scoping the horizontal meridian the instrument is moved horizontally while the streak is oriented vertically.

Procedure

• It is a monocular procedure.• The examiner head blocks the eye that is being scoped.• Before beginning the examiner must choose a working

distance depending upon the arm length of examiner. 67cm- +1.50D 50cm- +2.00DTarget fixation: First letter in 6/60 line of log MAR chart so that it

relaxes accomodation and gives appropriate readings of the refractive error.

Procedure Patient instructions: The patient is instructed to Watch the letter E on distance chart. Told to be sure to let the examiner know if his or her head blocks the letter

E for the other eye that is not being scoped. Starting point: If the habitual priscription or poor distance visual acuity indicates patient

is highly myopic, choose moderate amount of minus lens for starting point. Otherwise begunwith no lens at all not even a WDL.When this is done

“With” motion tipically indicates that the patient is 1) Hyperopic 2) Emmetropic 3) Myopic less than 2D “Agaist” indicate he or she is myopic more than 2D

Procedure for spherical ammetropia

Steps: Measure PD, fit trial frame/phoropter. Usually use divergent beam to avoid confusion. Darken room and control accommodation (appropriate target and

WDL) Eg:Assume the examiner uses a working distance of 50cm. With no lens in the refractor “with” motion would be seen in both the

vertical and horizontal meridians, using the plane mirror. Plus lens power would be then added in steps of 0.50 or 0.75 D, the

reflex being observed “with” each added lens power until a definite “against” motion is observed in all meridians.

Plus lens power would then be reduced 0.25D at a time until “neutral” motion is observed

Procdure for spherical ammetropia

When the examiner believes that “neutral” motion has been observed a usefull procedure is to

1)Reduce plus lens power 0.25D which should result in the observation of “with” motion and

2)Increase plus lens power to 0.25D more than when neutrality was thought to be observed,with should result in observation of “against” movement.

Conclusion: If neutrality is found to occur with a +2.00D lens in the refractor, the

conclusion is that the patient is emmetropic since the +2.00D sphere corresponds to the working distance lens (for the 50cm distance)

If the neutrality is found with a +2.75D lens in the refractor, the patient is a +0.75D hyperope;If neutrality is found with a +1.00D lens in the refractor, the patient is -1.00D myope.

Final prescription

Using WDL : Your Rx = amount of DS added Eg. WDL = +2.00D, DS added = -3.00DS Rx = -3.00DS Eg. WDL = +1.50D, DS added = -3.00DS Rx = -3.00DS

Not Using WDL : Your Rx = amount of DS added – WD (D) Eg. WD = 50cm (2.00D), DS added = -3.00DS Rx = -3.00 – (2.00) = -5.00DS DS added = +2.00DS Rx = 2.00-(2.00) = plano Eg. WD = 67cm (1.50D), DS added = -3.00DS Rx = -3.00 – (1.50) = -4.50DS

Procedure when astigmatism is present

Because most people have astigmatism, with each addition of spherical lens power the examiner should scope both vertical and horizontal meridian.

We correct the astigmatism with cylindrical lens.Cylindrical lens may be plus or minus, but have power

in only one meridian, that which is perpendicular to the axis of the cylinder.

The axis meridian is flat and has no power.Vertical meridian is stronger(with greater refraction)

and horizontal is weaker(with least refraction)

Procedure when astigmatism is present

Steps: Measure PD, fit trial frame/phoropter. Usually use divergent beam to avoid confusion. Darken room and control accommodation (appropriate target and WDL) Eg: Assume again the examiner is uses50cm working distance and that with

no lens in the refractor, with motion is foud in both the horizantel and vertical meridians.

Plus sphere power is added, 0.50 or 0.75D at a time, until neutrality is found in the least plus meridian.

At this point , “with” motion is would still be observed in the opposite meridian.

If for example neutral motion is found in the vertical meridian, and with motion is still present in the horizotal meridian.

Now count the number of clicks(each click being 0.25D) as additional plus

Procedure when astigmatism is present

lens power is added to neutralize the most plus meridian(horizontol) If for example 5 clicks of plus lens power is added then we should make a

note that this eye has 1.25D of astigmatism. Now we will find the vertical meridian shows against motion. Minus cylinder power is then added with the horizontal axis to neutralize

the against motion in the vertical meridian. In this case it would be expected that 1.25D of minus cylinder power

would be required to neutralize motion of vertical meridian. At the end the lens in the refractor would be recorded as +3.00D

spherical and -1.25D@180 cylindrical. After removing the WDL from the spherical power the finding would be

recoded as +1.00 -1.25@180. The examiner is then ready to scope the left eye.

Final prescription

Using WDL : Rx = amount of DS added/amount of DC added at its axis sphere/-cyl x axis (-ve cyl form) Eg. WDL = +2.00D, DS added = -3.00DS, DC added = -1.00 axis 180 Rx = -3.00/-1.00 x 180

Not Using WDL: Rx = amount of DS added - WDL/amount of DC added at its axis (-ve cyl form) Eg. WD = 50cm, DS added = -3.00DS, DC added = -1.00 axis 180 Rx = -3.00 (-2.00) / -1.00x180 = -5.00/-1.00x180

Locating the principal meridian.

• The principal meridians may be always at 90 or 180.• The examiner should carefully observe the orientation of the reflex in patient’s

pupil as the beam is moved horizontally and vertically.• Eg: Assume that the examiner neutralized the motion in the least plus

meridian(imagine vertical) and neutralization of horizontal meridian is approached, where reflex in the being oriented 20 or 30 degrees vertical rather than being oriented vertically.

• The orientation of streak is then altered in the direction corresponding to the streak in the patients pupil.

• In completing the neutralization in the vertical meridian the streak should be moved in the 120-degree meridian until neutralization of 120-degree meridian has achieved.

• The 30-degree meridian is then neutralized, after which against motion will be seen in 120-degree meridian to which minus cylinder’s are added until it is again neutralized.

Control of patients accomodation

Subject should be constantly reminded to watch the letter E or other fixation target to make sure that accomodation is being relaxed through the process.

Because retinoscopy is monocular procedure as the examiner blocks the eye that he is scoping, it should be understood that any accomodation exerted by the eye that fixates the distant target will also be present in the eye being scoped, since both eyes accommodate equally.

Some examiners avoid the possibility of fixating eye accomodating by adding +2.00D power before each eye.

Some prefer not to do this, however, unless concave mirror is used as it involves working with against motion.

The examiner can avoid the problem of accomodation by rescoping the right eye after the left eye has been scoped.

Varying the width of the streak

• Mechanism that controls the width of the streak also allows to switch between plane mirror and concave mirror.

• Eg: Copeland streak retinoscope: All the way up, plane mirror is in position with a wide streak.As

it is lowered gradually , the streak decreases in width. And widens again.At the lowest adjustment the streak is again

at its maximum width but with concave mirror effect. American Optical and Welch Allyn: These instruments

are in plane mirror mode when the mechanism is all the down rather than all the way up.

Bright, speed and motion of reflex

The high the myopia or hyperopia the reflex seen in the patient’s pupil is not only dull(because it is badly out of focus) but larger than the diameter of patient’s pupil.

This is being the case the examiner cannot see a boundary between light and shadow, making it impossible to judge the speed of movement of reflex(size of illuminated area of retina is more)

As the reflex approaches the neutrality, (the illuminated area of retina becomes increasingly smaller) causes the reflex to appear increasingly brighter to the examiner

For 5mm diameter peep hole and 40cm working distance, the diameter of illuminated area of retina at neutrality would be 0.23mm.

Accuracy of retinoscopy

Bearing in mind that a retinoscopy finding is a monocular and should be compared with monocular rather than binocular subjective findings, experience indicates that there are many possible cause of inaccurate retinoscopy findings, including the following:

1)Incorrect working distance.2)Scoping off the patient’s visual axis.3)Failure of patient to fixate the distant target.4)Failure to obtain a reversal.5)Failure to locate the principal meridin.6)Failure to recognize scissor’s motion.

Thank you