Dynamic retinoscopy srijana

dynamic retinoscopy types ,procedure and interpretation

1. DYNAMIC RETINOSCOPY Srijana lamichhane B.optom,IOM (MMC)

2. What is retinoscope ? Is an instrument used to determine the refractive error Is an objective method What is retinoscopy ? The purpose of retinoscopy is to obtain an objective measurement of patient’s refractive state it is based on the fact that when the light is reflected from a mirror into the eye, the direction in which the light will travel across the pupil will depend upon the refractive state of the eye

3. Types of retinoscopy static retinoscopy : the patient is looking at a distance object, with accommodation relaxed Dynamic retinoscopy : the patient is looking at a near object ,with accommodation active near retinoscopy : the patients is looking at a near object, with accommodation relaxed

4. Dynamic retinoscopy Objectively determines the point that is conjugate to the retina when the pt. is viewing a particular target NO WORKING DISTANCE POWER IS ADDED OR SUBSTRACTED FROM THE FINDING

5. Movements same as that of static retinoscopy With movement : eye conjugate to a point either behind the eye or behind the retinoscope. Against movement : eye conjugate to a point between the eye (patient’s) and retinoscope. Neutrality : eye conjugate with retinoscope

6. History early 1900s, various investigators began utilizing the retinoscope to determine the amplitude or status of accommodation in non-verbal patients - term dynamic retinoscope emerged A.J. Cross is credited with introducing the basic theory and method for dynamic retinoscopy Sheard, Nott, and Skeffington - elaborated on the theory and procedure

7. Goals to determine accommodative Response also helped to determine the most appropriate near prescription with testing conditions Reveals the degree to which accommodation is fluctuating when attending to a near target & if the eyes are balanced equally at near provide the information and insights regarding the patient’s abilities and level of visual processing at the chosen distance

8. Accomodation Accomodative stimulus is defined by the near target stimulus Because of depth of focus and depth of field the accommodative response is generally less than the stimulus Near point is usually located around 10-17cm beyond near target at 40cm

9. Accommodation Accomodative demand is provided by the target distance as well as the refractive error Over minus or under plussed : has extra accommodative demand required to see target clearly Under minused :does not have to accommodate as much

10. Accommodation Accommodative response is a measure of the actual accommodation that is present If your accommodative system likes to “hang out” Right on the target accommodative response = stimulus In front of the target accommodative response >stimulus (i.e. accommodative lead) Behind the target accommodative response< stimulus ( i.e.accommodative lag)

11. Types of dynamic retinoscopy Monocular Estimation Method (MEM) Nott retinoscopy Bell retinoscopy

12. MEM (monocular estimated method) Founder Dr. Harold Haynes Clinician neutralize the reflex of the eye while patient accommodates to fixate a target placed at the patient’s customary reading distance (usually at 40cm)

13. Materials series of cards with a central aperture mounted on a retinoscope cards can have printed letters, or words, or pictures that range in size from 20/160 (6/120) to 20/30 (6/9) Arranged around the aperture

14. Procedures instructed to keep the targets clear sweeps the retinoscope beam observes the motion of the retinoscopic reflex quickly interposes a trial lens at the spectacle plane

15. Interpretation “lag of accommodation” is the amount of plus lens that neutralizes the reflex has been found to accurately measure the lag of accommodation in an objective manner Example If the retinoscopic reflex is neutralized by +1.75D then lag is ADD = +1.75 – (+0.75) = +1.00

16. Limitation Plus lenses – relaxation of accommodation – accommodative response measured by this value found to be 10% less No longer than one fifth of a second

17. Bell retinoscopy Developed by Drs. W.R. Henry and R.J. Appel Evaluate the performance of the accommodative system under moving & real life conditions in free space cognitive demand is low  term “Bell” is used because the procedure was done originally using a cat-bell suspended on a string.

18. Materials Three dimensional viewing target a small, highly reflective bell dangling from String – replaced with a Wolff Wand(½ inch diameter, metal ball mounted on the end of a rod)

19. Procedures wand is held by the examiner moved closer to and farther from the patient - slower than 2 inches/sec retinoscope is positioned at a fixed distance of 50 cm (20 inches) patient fixates the target and the examiner notes the direction of the reflex

20. Contd target is moved closer to the patient there will be a point where the motion changes from “with” to“against ’’ Target is again moved away from patient until with motion is observed

21. Interpretation The two measurements are recorded as a fraction e.g. 30/40 (meaning that the inward change from “with” to “against” occurred at 30cm and the outward change from “against” to “with” occurred at 40cm. The expected values for Bell retinoscopy are: Inward shift at 42.5 to 35cm and outward shift at 37.5 to 45cm. If the lag of accommodation does not fall within these ranges, the procedure is repeated with plus lenses. Lenses which normalize these ranges are considered an acceptable nearpoint prescription. 

22. Contd eye movement control can be assessed by judging the extent to which the ball can be fixated eye-hand coordination can be evaluated by asking the patient to touch the Wolff Ball during the procedure NPC can be determined by the normal means limitation patient converges - scoping more off axis

23. Nott’s retinoscopy developed by I. S. Nott in the 1920s main purpose is identical to the MEM method cognitive demand is moderate

24. materials reduced block of 20/20 (6/6) letters is placed at 16 inches (40 cm) from the patient

25. Procedures Patient wearing their best correction is instructed to view a detailed and high contrast target placed on the retinoscope Retinoscopic reflex is examined from the plane of target and retinoscope is moved closer or farther away from the target until neutrality is achieved

26. Interpretation Dioptric difference between these two distances equals the lag of accommodation Example Distance from the target to spectacle plane = 40cm Distance from retinoscope to spectacle plane = 50cm Lag of accommodation = +2.50D – 2.00D = +0.50D

27. Book retinoscopy Also known as getman retinoscopy. Developed at gesell institute of child development at yale university. Develop to obtain information about the visual processing of nonverbal infants . Cognitive demand is high.

28. Getman and kephart described the following response levels with this technique. A. free reading level : Desirable , reflex varies from neutral to with B. Instructional level : more demanding than the free reading level , reflex is a varying fast against motion. • C. Frustration level : Even though the subject is “focused” on the page he is not interpreting the information properly slow against motion Reflex color is bright and white when the words are understood.

29. Contd Reflex color is more pink and dims slightly if the patient is struggling to comprehend a word or passage. Reflex color is dull and brick colored when the patient has given up on comprehending a word or reading passage.

30. Cross retinoscopy Andrew J. Cross (1911) • Start with static retinoscopy finding . Patient made to view target at 40cm . Examiner performs retinoscopy adding plus lens till neutrality. A alternative to cycloplegic refraction Method of adding plus lens power to obtain a reversal

31. Determining the correction in cases of Astigmatism Presbyopia Subnormal accommodation in young patients

32. Limitation A measurement of negative relative accommodation Plus power recommended – patient would not persist

33. Sheard’s method Charles Sheard (1920) Introduced the concept of “ Lag of accommodation” add plus lens power until neutrality occurred

34. Tait’s method Tait(1953) Working distance = 33cm Fogging with a considerable amount of plus lens power and then approaches neutral by reducing the plus lens power Found an average of approximately +1.50 D more than sheard system , thus total lag of accommodation = +2.25 D Close to +2.50D i.e Negative relative accommodation.

35. low neutral and high neutral methods Sheard ( low neutral method) The end point is the least plus power required for a neutral reflex to be observed. Cross ( high neutral method) Addition of plus power beyond neutrality until a reversal occurs.

36. Stress point retinoscopy developed by Harmon and Kraskin evaluate the response of the entire organism to stress in stress-point retnoscopy - looking at the change in reflex quality Cognitive demand is moderate to high

37. reasoning behind stress-point retinoscopy is that vision is intimately related to the whole body and that a physiological change in stress occurring in the body can be perceived through a change in the retinal reflex Three things occur when near-point stress is experienced Firstly - there is a change in the individual's pulse Secondly - there is an inner canthal twitch and lastly - change in the colour of the retinal reflex is observed

38. Procedures Wolff ball is moved closer to the patient - looks at which distance the reflex "pops" initially brightened and then became dull and finally brightened again - termed "popping" of the reflex - about 4 inches in front of the patient distance is noted and then different lenses are placed binocularly and the procedure is repeated

39. ideal lens is the one which makes the stress point as close to the subject as possible more desirable to have the stress-point closer to the patient - they are not working under physiological stress For example; if the stress-point of a subject is 40cm and they habitually read at 30cm they would be under constant near-point stress

40. plus lenses move the stress-point closer to the subject and minus lenses move it away in children the stress-point should be 10cm closer to the subject than the Harmon distance. In adults, the stress point is 20 to 22.5cms from face. 

41. Near retinoscopy by mohindra Near retinoscopy by mohindra in 1977. For use in determining the refractive state of infants and children The stimulus or fixation is the dimmed light source of the retinoscope in a darkened room. The retinoscope is held at a distance of 50 cm with hand-held trial lenses.

42. Near retinoscopy differs from other forms of dynamic retinoscopy in the following ways: it is performed in complete darkness , the only illumination in the room is supplied by retinoscope with child fixating at retinoscope light . It is monocular procedure that is eye not being examined is occluded. The adjustment factor of -1.25 D is algebrically combined with the spherical component of the gross sphero - cylindrical lens powers.

43. Contd

44. Lag of accommodation Time lapse between the presentation of an accommodative stimulus and occurrence of the accommodative response Average time - Far to near accommodation is 0.64 seconds - Near to far accommodation is 0.56 seconds

45. Lag of accommodation Accommodative lag = accommodative demand ( +2.50D at 40 cm) – accommodative response Lags are greater when closer test distances are used Lag of accommodation exhibits a slow but progressive increase to adult levels Binocular accommodative system normally respond with only +1.75D to +2.00D of increased plus power

46. Normal Lag: +0.50 or +0.75 diopters High Lag: +1.00 diopters or higher Lead : +0.25 diopters or less

47. Lag > +0.75D/ High Lag Inadequate accommodative response:- as a result of :- near esophoria poor negative vergences accommodative insufficiency uncorrected hyperopia Patient is Overminused

48. Low Lag /lead of accommodation < +0.50 Overaccommodating As a result of :- near exophoria spasm of accommodation Over Plus Correction inadequate positive vergences

49. Source of error Same as those with static: scissors, small pupils, dim media (cataracts, etc.), angle More sensitive to physical arrangement for the measurement (distance, lens adaptation), instructions given and patient’s cooperation Changes in patient’s fixation or accommodative level (often related to failure to understand task or to cooperate)

50. Patient looking at a target at a different distance than requested A +0.50 to +0.75 lag is not normal if not testing at 40cm Lag increases as fixation distance is reduced Adaptation to lenses with MEM: relaxes with plus lenses, stimulates with minus lenses

51. Refrences Clinical Procedures in Optometry by J.D. Bartlett, J.B. Eskridge , J.F. Amos Theory and Practice of Squint and Orthoptics by A.K.Khurana Borish’s Clinical Refraction by W.J. Benjamin Internet