Retinoscopy

• • objective method of refraction
  • measures the optical state of the eye and is accurate up to 0.25D correction
• it is importatnt to: To determine the nature of the patient’s refractive error. To approximate the lens power that will neutralise the error and improve vision (usually refined subjectively), To assess the refractive error in infants, small children, illiterate persons, mentally retarded, uncooperative individuals and patients with speech loss, Screening for ocular disease: Keratoconus, media opacities
• retinososcopy can assess the clarity of the media and can give a measure of the persons accommodation
• • Spot – circular patch of light
  • Streak – slit of light that can be rotated around 360°
  • Divergent – plane mirror mode
  • Convergent – concave mirror mode
• • Clinician watches shape and movement of the light within the pupil (the Retinoscopic reflex)
  • The Retinoscopic reflex colour is usually red or orange
  • Trial lenses added until the shape and movement reach a state called “reversal” “neutral point”
• • The vergence of the rays that leave the patients eye is dependant on the refractive error of the patient’s eye. The rays leave to the far point of the patient’s eye.
  • In emmetrope the rays leave parallel
  • In myope the rays leave convergent
  • In hyperope leave divergent
• • emmetropic eye: Far point is the point farthest from the eye at which an object is clearly focused on the retina when accommodation of the eye is completely relaxed
  • myopic: far point lies a finite distance in front of the eye
  • hyperopic eye: far point is virtual as only converging light can be focussed on the retina
• • If the image formed between the eyes of the patient and the , the red reflex moves opposite to the movement of the retinoscope (high to moderate myope)
  • If the image formed behind the eye of the observer (low myopia) or the eye of the patient (hyperopia) the red reflex moves with the movement of the retinoscope
• • Retinoscopy concerns manipulating the FAR POINT PLANE to be coincident with the examiner’s retinoscope
  • Finding the lens that places the far point in the plane of the observers eye, at this point the retinoscopic reflex is said to be neutralised. That is, there is neither with nor against movement, and the patients pupil seems to be filled with light (no movement of red reflex is noticed
• • with - light patch moves in the same direction as the reflex
  • against - the light patch moves in teh opposite direction of the reflex
  • neutral - no apparent movement/ the light is moving infinitely fast
• performing retinoscopy - Static distance fixation retinoscopy (accommodation relaxed), Dim room illumination, Px observes target at 6m, Both eyes open, Examiner sits at a wd of 2/3 m, Use RE, ret in R hand when examining Px’s RE and vice versa
• • brightness - Dull - Far from neutral, Bright - Close to neutral
  • speed - Slow - Far from neutral, Fast - Close to neutral
  • size - Small - Far from neutral, Big - Close to neutral
  • correct with movements with positive lens and correct against movement with negative lenses
• Retinoscopy can be done using a lens rack or retinoscopy bar.
• Retinoscopy can also be done using a phoropter.
• Cycloplegia, such as cyclopentolate HCl 1%, can be used to relax accommodation.
• Retinoscopy with cycloplegia may result in a refraction of RE +5.00DS +3.25DS, indicating latent hyperopia.
• Static retinoscopy involves the patient fixating on a distance target with accommodation relaxed.
• Reflex moves simultaneously in opposite directions from pupil centre is a characteristic of keratoconus.
• Split or scissors reflex is a characteristic of keratoconus.
• Keratoconus is a condition where the cornea takes on a conic shape.
• Increase room illumination to reduce the patient’s pupil size is a method used in keratoconus.
• Use lens step larger than 0.25DS and bracket technique is a method used in keratoconus.
• Reflex swirls over a cone are a characteristic of keratoconus.
• The Near fixation or Barrett method is used when the examiner is unable to do ret accurately with both eyes, using only one of the practitioner’s eyes.
• In the Barrett method, retinoscopy of both eyes is performed while the patient fixates the ret, and the spherical component of the initial result is checked when the patient fixating in the distance using the examiner’s good eye.
• Speed of reflex= (W-X)/(W-K) Along 10 speed of reflex= (-2.00)/(-2.00-1.00)= 0.66 (1 mark)
• Retinoscopy mirror is at 67 cm: 1.50DS working distance.
• The Mohindra technique or near retinoscopy is useful in children that cannot fixate a distant target, performed in a dark room with the patient fixating the retinoscope light at a distance of 50cm, and correcting for -1.25D.
• Dynamic retinoscopy is used to investigate the accommodative state of the eye in near vision.
• In large pupils, retinoscopy may show a WITH movement in the centre of the pupil and an AGAINST movement in the periphery, requiring concentration in the centre of the pupil and ignoring the reflex from the edges of the pupil.
• In the presence of opacities, retinoscopy may be duller and more difficult, possibly requiring dilation of the pupil or moving closer to the patient.
• • Neutral: neutralisation of retinoscopy reflex in any meridian
  • Reversal: Overcorrection by 0.25DS should cause reversal of the movement
• Patient observes a distant target (duochrome)

  Dim the room light

  set the retinoscope to plano mirror position (collar down) and examiner’s RE and right hand to view Px’s RE

  Fog the other eye of Px (to ensure patient is not accommodating)

  Keep the same working distance

  Work on axis (align yourself with visual axis of patient’s eye
• At neutral the reflex will have no movement, it will be very large and very bright
• varying teh working distance is Not a useful way to approach retinoscopy from scratch BUT is very useful close to neutral to confirm neutral has been achieved. moving forward you should have a with movement and moving backward you should have an against movement
• • Direction of reflex movement coincident with ret movement only when ret is moved along a principal meridian
  • The orientation of the beam and the scanning motion are always perpendicular to one another
• How to correct astigmatism: Corrected slowest with or fastest against (if they are both with correct the slowest first and if they are all against correct the fastest first), Leave sphere in place, Should be an against movement in the other meridian, Use a negative cyl to correct, Refine axis
• • If cyl is small in power – won’t see cyl until close to neutral with sphere
  • If cyl axis is correct – reflex moves in same meridian as ret
  • If cyl axis is off-set – reflex moves in different meridian to ret