Retinoscopy.pdf

Principles and Practice of Primary Care Optometry 2 Dr. Ariette Acevedo Rodríguez, O.D. Retinoscopy Synonyms of Retinoscopy Skiascopy Skiametry Umbrascopy Pupilloscopy Retinoskiascopy Skia: derived from greek meaning shadows from internal structures. Definitions Refract: to change the direction of a...

Principles and Practice of Primary Care Optometry 2 Dr. Ariette Acevedo Rodríguez, O.D. Retinoscopy Synonyms of Retinoscopy Skiascopy Skiametry Umbrascopy Pupilloscopy Retinoskiascopy Skia: derived from greek meaning shadows from internal structures. Definitions Refract: to change the direction of a ray of light when it passes from one medium into another of different optical density. Determining the nature and degree of the eye's refractive errors and its correction with lenses. Retinoscopy: method of determining error of refraction by illuminating the retina and observing the rays of light emerging from the eye. Refractometer: optical instrument to determine in an objective manner the refractive state of the eye (autorefraction- depends on refractive indexes). Definitions Refractor: instrument designed for refraction and phorometry, equipped with spheres and cylinders, prims, and other accessories for refraction and binocular vision testing. Phorometry: used to test oculomotor function. Vergences, phorias. Can be performed behind refractor or trial frame. Retinoscopy During retinoscopy, the retina acts as the primary reflector of the light that has traveled through the eye structures with different refractive indexes. Greatest index of refraction is the cornea (needs to be clear). Retina Layers The incident light rays that strike the outer limiting membrane (OLM), are transmitted to the photosensitive pigments in the outer segments of photoreceptors by a waveguide mechanism. The light that returns from the RPE and choroid is the result of competition between light absorption and backscatter. Because of this, the fundus reflex is of red/orange color during retinoscopy or photorefraction. Retina Layers The RPE and choroid contain important light absorbers Melanin: highest concentration in RPE Hemoglobin: higher concentration in choriocapillaris Xanthophyll: yellow pigment which absorbs blue light. Lutein and zeaxanthin Responsible for macular color Retinoscopy Types/Modalities Static Retinoscopy Streak Retinoscopy: uses a streak of light, converging or diverging rays. Mostly used modality. Spot Retinoscopy: uses a spot of light, with a plane mirror. Good for children. Not good if you want to refine astigmatism from the start. Radical Retinoscopy Hindra Mohindra Retinoscopy Dynamic Retinoscopy Bell MEM Types Retinoscopy Static Retinoscopy: the determination of ametropic correction during fixation at a set distance with accommodation relaxed. Radical Retinoscopy: used with small pupils or media opacities that make the reflex faint and indistinct. Examiner will have to use a closer WD (2010cm). Important to note new WD Hindra Mohindra: used for children. The patient fixates the light on the retinoscope, the WD is 50cm. When compensating the WD, 1.25D is subtracted instead of 2.00D. Dynamic Retinoscopy: when retinoscopy is performed while the patient is fixating a target at near. MEM or BELL Accommodation is in use Instrumentation Refractor or phoropter Skioscopy bars Trial lenses and trial frame Simplest to use ±0.12D to ±20.00D Minus cylinder from: -0.12DC to 6.00DC Prisms: 1-15𝝙 Occluders, pinholes, Maddox Rods, red and green lenses, neutral density (ND) filters, polarized lenses Trial Frame Why trial lenses and frame? Trial lenses and frame: For children that cannot stand behind phoropter (also some elderly). Bedridden patients: patient’s home, assisted living homes, hospitals. Lenses are larger in diameter; examiner can observe better the eye movements. Verify distance Rx Verify near Rx Screenings Mohindra’s Set Up Examiner at 50cm from the patient. Usually performed in children, have them sit in their parent's lap if unable to keep in chair. Completely dark room. Use loose lenses or skiaoscopy bars. Retinoscope light intensity enough to observe the reflex, but the patient still feels comfortable. Have the patient look at the light while scoping the meridians and neutralizing. Write down the optical cross Remove the 1.25D WD from the results to obtain Mohindra Retinoscopy Phoropters Refractors or Phoropters are interchangeable terms Sphere and cylinder lenses Jackson cross cylinder for astigmatic axis and power Risley rotating prisms (for phorias and vergences) Near vision tests Objective Retinoscopy Refractive error is determined without the input of the patient. Requires either a (an): Human operator with a retinoscope Automated refractor-several. Pros and cons. Photorefractor Retinoscopy Purpose To determine the distance refractive status of the patient’s eyes. Goal: locate the far point of the spherical eye or the two far-point planes of an astigmatic one. It is an objective measurement Used as the starting point for subjective refraction Know your working distance Retinoscopy brings the patient’s far point to a location that is a predetermined distance from the patient, the working distance, in front of the eye, with the use of lenses. Retinoscopes Optical head The most widely used retinoscopes are the Copeland, Keeler, Heine, and the Welch-Allen. They consist of an optical head, a sleeve, and a battery handle. Streak vs Spot Retinoscopy Streak: more accurate-fast. Developed by Copeland. Spot: external light source, very fast, for estimation. http://www.oculist.net/downaton5 02/prof/ebook/duanes/pages/v1/v 1c037.html Sleeve Battery handle Spot Retinoscopy Optic are the same, except that cylinder axis and power determination is more accurate with the streak method. For some, the brightness of the reflex is much better with the spot retinoscope. Meridional axis control are not necessary and not present with spot retinoscopy. Will look at the center of a diverging light through the patient’s pupil. Not manufactured anymore Retinoscopic Reflexes to Determine the Principal Meridians The principal meridians correspond to the orientation of the streak that provide the thickest and the thinnest reflexes or the brightest and dimmest reflexes. Spherical error: same thickness reflex in all meridians Astigmatic error: thickness varies in different meridians Break phenomenon Thickness phenomenon Skew phenomenon Astigmatic Reflex Skew phenomena is used more to refine the axis of small cylinders (astigmatism) When the streak is of the axis, the reflex and intercept move in different directions (their motion is skewed) The reflex moves parallel to the intercept when the streak is on the axis. Straddling Used to confirm the axis Perform with the estimated cylinder in place. Then the streak is turned 45° off axis in both directions. Results: if the axis is Correct: widths are equal in both positions Incorrect: widths are not equal in positions Scissor reflex Sometimes one half of the reflex goes with the other half goes against… Confusing Fundus Reflex Motion will be confused, according to the: Number of separate optical areas existing and Degree of ametropic refractive differences between these areas. Possibilities are the patient is having: Irregular astigmatism Distorted corneas- ex. Keratoconus, PMD Monochromatic optical aberrations (especially coma and spherical aberration, which are the most common) Confusing Fundus Reflexes The usual situation is encountered when spherical and coma aberrations coexist, and the refracting power of the eye is greater throughout the periphery than the center of the pupil. Then the eye is relatively myopic in the periphery and becomes more myopic peripherally when the pupils dilates (dim or by pharmacological agents) https://www.youtube.com/watc h?v=fWsSy8vU13w Center is thicker and has with motion and the periphery is thinner and has against motion (horizontal meridian being scoped). That is what happens with scissors motion. Scissor Motion: The retinoscopy reflex moves more quickly in the center than in the periphery of the pupil as neutrality is approached from less minus/more plus direction and appears to have a wider streak in the central area than in the periphery. Neutrality is reached first in the center of the pupil and more minus is needed to neutralize the periphery. More common in: very myopic eyes Light irises Younger adults When confused reflex is encountered: Is best to neutralize the central portion and rely on bracketing to reduce the error in neutralization. False Neutrality Can be created by focusing the incident beam on the entrance pupil. The beam is well focused on the iris, which is approximately in the same plane as the entrance pupil. You will do this in slit lamp/biomiocroscopy evaluation, for retro illumination technique. Doctor says: “I am going to do your refraction.” “Voy a hacer su refracción.” Patient thinks: What??!! Explain in plain simple words “I am going to determine the power of your eyes.” ”Voy a determinar el poder (o aumento) de sus ojos.” Sources of Error in Retinoscopy Incorrect working distance Failure to remove the working distance Scoping off the patient’s visual axis many times, examiner is away from visual axis Failure of the patient to fixate the distance target Looking at you will cause accommodation, making it a dynamic retinoscopy. Failure to obtain reversal Failure to locate the principal meridians Failure to recognize the scissors motion Interpupillary Distance Is the distance from the center of one pupil to the center of the other pupil, in mm. From temporal limbus OD to nasal limbus OS or Measured from center to center of pupils Necessary before ordering SRx and before performing retinoscopy Why? Interpupillary Distance To measure Binocular PD Instrument: millimeter rule (PD ruler) Examiner and patient are at the same eye level, at a distance of 40cm (16 inches) Position the PD ruler at the nose bridge of the patient, tilted back, resting on the nose Hold the PD ruler between the thumb and forefinger and the other 3 fingers are used to rest in the subject's head (temple) 1. Close your OD. Ask the patient to fixate at your OS. 2. Zero the PD ruler at the center OD pupil, or to OD temporal margin of pupil or OD temporal limbus Read the marking on the contralateral side 3. Examiner closes OS, subject fixates at your OD 4. Examiner reads off scale directly in line with OS pupil center, OS left nasal pupillary border or OS nasal limbus. 5. DO NOT MOVE THE PD RULER: Now examiner closes OD, opens OS and patient fixates to OS and check to make sure zero point is still correct. Highest number is distance PD, the lowest is near PD Record always Distance/Near in mm (largest always first) Using the corneal reflexes IPD Measure from the center of the nose bridge to the corneal reflex Also gives you Monocular PD Method to be used of patients with strabismus or only having one eye. Phoropter The first far line is neutralized with a sphere and the other one (second far line) with a cylindric lens (plano-cyl), added over the sphere, with its axis at the orientation of the retinoscopic bar/streak reflex (in the phoropter). Adjustment knobs: PD, leveling, VD, pantoscopic tilt Sphere controls Minus-plano cylinder control: power knob and axis knob Auxiliary lens/aperture control: O, OC, R, -0.50, JCC, PH, RL (red lens), RMH/RMV (red Maddox rod), P (polaroid), +0.12DS, H (10 I) and V (6 U) prism. Ancillary units: Jackson Cross cyl unit, rotary prism unit Auxiliary Lens Knob IPD Vertex Distance Spherical Lens Control Cylinder Power Knob Level JCC Unit Risley Prism Unit Cylinder Axis Knob Set up for Phoropter Disinfect with alcohol the phoropter Remove corrective lenses Measure IPD (distance/near) Adjust height of the chair, so your eyes and patient eyes are at the same level Adjust IPD in phoropter, level phoropter, vertex distance (12mm) and check pantoscopic tilt Set Up Phoropter Place the target of 20/200 or larger with R/G filter at distance To fixate and help relax accommodation Instruct to keep both eyes open and if you block their view, let you know Look at the big letter E (Red/Green part). Not at me. Tell me if I block the letter. “Mire a la letra E (parte roja/verde), no a mi. Digame si le tapo la letra.” Using DIM illumination Place a lens ≥+1.50D to relax the accommodation For NBEO you need to perform a 3-eye retinoscopy: OD-OS-OD For proficiency purposes DO NOT use the retino (R) lens Hold retinoscope 50 or 67 cm from the patient’s eye. Working distance for 50cm is -2.00D and for 67cm is -1.50D. The patient’s OD is scoped with the examiner’s OD and the patient’s OS is scoped with the examiner’s OS. This allows the examiner to stay as close to the patient's visual axis as possible, however, the examiner should not obstruct the patient’s view of the target. Stay close to the visual axis without obstructing the patient’s view One of the most common errors in retinoscopy is eccentricity due to wrong examiner’s position The patient should be instructed to tell the examiner if the view of the target is blocked. ”Mire la letra E, lado rojo/lado verde. Digame si le tapo la letra Look at the letter E, red or green side. Tell me if I am blocking the E. Procedure Identify the principal meridians Identify the meridian with the most WITH motion (thicker reflex). This is the most plus meridian. Neutralize this meridian first. Add plus lenses (black numbers) to neutralize the with motion. Dioptric wheel down Add minus lenses (red numbers) to neutralize an against motion. Dioptric wheel up 1ST MERIDIAN WITH 2ND MERIDIAN AGAINST NEUTRALIZE FIRST THE WITH 1ST MERIDIAN SLOW WITH 2ND MERIDIAN FAST WITH NEUTRALIZE FIRST THE SLOW WITH 1ST MERIDIAN SLOW AGAINST 2ND MERIDIAN FAST AGAINST NEUTRALIZE FIRST THE FAST AGAINST Retinoscopy in the Phoropter Once you neutralized the most plus meridian, go 90° away and change the direction of the streak to 90° away and align the cylinder axis arrow in phoropter with the direction of the streak. Now neutralize the other meridian This time you should have against motion if the patient is astigmatic. If not, it was spherical and should have a neutral motion. Retinoscopy in the Phoropter In the phoropter: The axis of the cylinder lens should now be aligned with the streak of the retinoscope. Neutralize this meridian by adding minus cylinder power in the phoropter. The axis must be aligned with the streak. When both meridians have been neutralized, the number indicates the GROSS retinoscopy. Remove the WD to your SPHERE ONLY. Now you have the NET retinoscopy. Take VA This is your objective retinoscopy using a phoropter. Different Phoropters Optometrist use minus cylinder form, spectacle prescriptions (SRx) are done in minus cylinder form. You will find all phoropter in pre-clinic and clinic are minus cylinder, therefore using minus-cylinder form the axis is recorded according to the orientation of the streak and not the movement. This is because you already neutralize with the cylinder at that axis. Alternatively, in the phoropter, spherical lenses can be used to neutralize both principal meridians, like using loose lenses or skiaoscopy bars. Ex: useful when cyl is higher than 6DC Need to use optical cross Plus (+) cylinder form Rather than overplus the against motion (as in (-) cyl form), you will “overminus” the tested eye, so “with” motion will be achieved. Spherical (+) power is then added at the spectacle plane until neutrality is obtained in the least plus meridian. Next, (+) cyl lenses are added until neutrality is obtained in the most plus meridian (using phoropter) Transpositions Transposition negative to positive form: +3.00 − 1.00𝑥090 = +2.00 + 1.00𝑥180 +3.00 − 1.00 = +2.00 −1.00 𝑐𝑜𝑛𝑣𝑒𝑟𝑡𝑠 𝑡𝑜 + 1.00 090 + 090 = 180 For the Lab Use skiaoscopy bars and/or loose lenses Once mastered go to the phoropter If your partner is an emmetrope, place trial frame with lenses Work with several sets of lenses (+) and (–) and do the crosses. This is what you will use in screenings. Recording Objective Retinoscopy: OD: +2.00-1.00x060. 20/30 NIPH OS -3.00-3.00x120 20/20 Record the objective retinoscopy and VA of OD and OS Do PH if 20/20 is not achieved Write Mohindra’s Retinoscopy/Dynamic, MEME, Bell, ect… if it was used. Photorefraction Photorefractions: Axial and paraxial techniques Is a photographic technique that can measure the refractive error and accommodative response. It is rapid and objective Only requires the patient to pay attention for short periods of time A specific photographic pattern, which varies with the degree of eye defocus with respect to the plane of the camera. Photorefractive methods are not as accurate as retinoscopy but can be very useful for testing infants and young children. Light emitted from a small flash source, placed close to the camera lens, is reflected from the eye and returned to the camera. Photorefraction Paraxial Photorefraction: if the eyes are focusing light for normal vision, the image shows a smooth “full moon” of red over the retina. If the eyes have abnormalities, the image changes. Myopia: reflects a bright half moon over the top of the pupil. Hyperopia: the light reflects as a brighter crescent moon in the bottom half of the eye. Myopia Hyperopia Photorefraction taking 3 photos 3 photos will be taken at an axial plane 1st: at 75cm: to determine pupil size 2nd: at 50cm 3rd: at 150cm 2nd and 3rd photos are compared to see which pupil is larger. If pupil is larger at 150cm, then eye is hyperope. If larger at 50cm, then the eye is myope. References for clarification on movements http://www.youtube.com/watch?v=vCWvQD58reo&feature =related (movements) http://www.youtube.com/watch?v=kAreDffuVCQ (general usefulness of retino) http://www.youtube.com/watch?v=zVmMjOx6rV8 http://www.youtube.com/watch?v=lj5GOU7O2Ik (espanol, plus) /*http://www.youtube.com/watch?v=VMjKLDvMnC0 espanol, minus) http://www.youtube.com/watch?v=IITNng1dWP4 (espanol, en phoropter)