Retinoscopy & Autorefractometry

This include a brief explanation of the clinical refraction methods in the eye examination procedure. In order to get the full video download the ppt. it includes a lot of important things

1. RETINOSCOPY & AUTOREFRACTOMETRY Presented By- Rejuana Mustafee , Paromita Nath B. Optometry 2 nd Year Sri Sankaradeva Nethralaya

2. RETINOSCOPY

3. CONTENTS Introduction History Types of retinoscope Streak Retinoscope Optical Principle Procedure Types of Retinoscopy Problems in Retinoscopy

4. INTRODUCTION An accurate objective measurement of the refractive state of an eye that can be made by using the retinoscope The technique is called retinoscopy Also known as pupilloscopy ,shadow scopy , skiascopy , umbrascopy , scotoscopy .

5. HISTORY 1859 : BOWMAN introduced retinoscopy 1873 : F.CUIGENT known as the father of retinoscopy -first described a retinoscope 1927 : COPELAND introduced the streak retinoscope

6. TYPES OF RETINOSCOPES 1. REFLECTING MIRROR RETINOSCOPES Plane mirror Priestly-smith’s mirror (plane and concave mirror ) 2. SELF ILLUMINATED RETINOSCOPE Spot retinoscope Streak retinoscope

7. Picture of types of retinoscopes

8. COMPARISON Cheaper than the self illuminated. Requires a separate light source. Glare from the source of light is annoying to the patient. To check axis and amount of cylinder is difficult Intensity and type of beam cannot be changed or controlled It is expensive than the reflecting one . The light source and the mirror are incorporated in one. Doesn’t annoy the patient and can be done smoothly . It is not difficult and exact axis of cylinder power can be found easily. Intensity and type of beam can be controlled and is easily manipulated. Reflecting mirror retinoscope Self illuminated retinoscope

9. STREAK RETINOSCOPE - It has two operating systems PROJECTING SYSTEM Main purpose – To illuminate the retina OBSERVATION SYSTEM Main purpose --- To allow the observer to see the retinal reflex of the patient

10. Optical principle The retinoscope works on Focault’s principle. Retinoscopy is based on the fact that when light us 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

11. OPTICAL PRINCIPLE The detail optics of retinoscopy can be considered in three stages— 1. ILLUMINATION STAGE : Light is directed into the patient’s eye to illuminate the retina . 2. THE REFLEX STAGE : An image of the illuminated retina is formed at the patient’s far point . 3. PROJECTION STAGE: The image at the far point is located by moving the illumination across the fundus and noting the behaviour of the luminous reflex seen by the observer in the patient’s pupil.

12. PROCEDURE OF RETINOSCOPY REQUIREMENTS Dim and 6m room Retinoscope Trial lenses Trial frame Visual acuity chart FIXATION TARGET The t arget given to the patient should be 6/60 in snellen chart It is given to the patient to relax the accomodation during retinoscopy

13. WORKING DISTANCE The distance from the retinoscope to the patient’s eye . D=1/F . Our arm length is around 66cm so the power of a lens that focuses parallel light rays at 66cm is +1.50 D. It relaxes accommodation during retinoscopy . It allows no need for mental arithmetic to calculate the working distance .

14. Process of doing retinoscopy We need to tell the patient about the test.. We should instruct the patient to fixate the distance target. The patient right eye should be examine with the examiner’s right eye with the retinoscope in the right hand and vice versa Working distance should be maintained at an arm length of 66cm The examiner should stay close to visual axis and should not obstruct the view of target . Examine the four primary meridians -90 ˚ , 180 ˚ , 45 ˚, 135 ˚.

15. Observation WITH WORKING DISTANCE : No movement of the red reflex– emmetropia . Movement of red reflex along with movement of retinoscope – hypermetropia Movement of red reflex against movement of retinoscope – myopia

16. RECOGNISING THE ASTIGMATISM If one meridian has against movement and streaking 90 ˚ away shows with movement indicate the presence of astigmatism . If both meridian are with movement and incase of astigmatism we will observe different speed and brightness and width from one meridian to other . Neutralise the slow movement first and vice versa in against movement.

17. NEUTRALITY No movement . whole pupil is filled with the light . Sometimes the reflex will break quickly . REASON FOR FALSE READING Inexperience . Not aligning with visual axis of patient . Definite working distance is not maintained . Lack of subject’s accommodation . Defect in trial lenses. Lack of patient’s co-ordination.

18. TYPES OF RETINOSCOPY Static retinoscopy : The patient is looking at a distant object , with accommodation relaxed . Dynamic retinoscopy : The patient is looking at a near object , with accommodation active. Near retinoscopy : Patient looking at a near object with accommodation relaxed. Wet retinoscopy : With cycloplegic drug , retinoscopy is performed. Dry retinoscopy : Without cycloplegic .

19. PROBLEMS IN RETINOSCOPY Red reflex may not be visible –small pupil,hazy media and high degree of refractive error Scissoring shadow —may be seen in healthy cornea but with unusual difference in curvature in the centre and the corneal opacities Patient with strabismus –it is easier to change the fixation of good eye retinoscopy can be performed along the visual axis of the strabismic eye Retinoscopy in nuclear cataract shows index myopia in early stages Spherical aberration –lead to variation in centre and periphery of pupil. Triangular shadow- maybe observed in patients with conical cornea.

20. Video representation of the procedure …… In the next slide….

21. REFRACTOMETER

22. CONTENT Introduction Optical Principles Development of Optometers : ~Early Optometers ~Modern Optometers . Fixation target and Accommodation Procedures New innovations Advantages and Disadvantages

23. INTRODUCTION Refractometry (Optometry) is an alternate method of finding refractive error with an optical equipment called refractometer or optometer . Automated Refractometers are designed to objectively determine refractive errors & are of various types depending upon the underlying principles they are based on. With increasing load of patients in any ophthalmology practice, the practitioners face challenges of completing all tasks( including history , thorough examination , refraction being the most important part ) within a fixed time frame. Therefore, an autorefractometer offers increasing speed and efficiency of refraction process accurately and repeatedly.

24. OPTICAL PRINCIPLES of autorefractometer The present day autorefractometers(AR) are based on the principles used in earlier attempts for automation of refraction. Most of the AR are essentially based on following two principles: i ) The Scheiner’s Principle ii) The Optometer Principle

25. THE SCHEINER’S PRINCIPLE Scheiner in 1619 observed that refractive error of the eye can be determined by using double pinhole apertures before the pupil. Following are the observations: 1. Parallel light rays entering the eye from a distant object which are normally focused on a point on the retina are limited to two small bundles when double pinhole apertures are placed in front of pupils , in emmetropia . 2. In myopia, the two ray bundles cross each other before reaching the retina & two small spots of light are seen. 3. In hypermetropia , the two ray bundles are intersected by retina before they meet & thus again two small spots of light are seen.

26. 4. These two points of light can be brought to a single point moving the double pinhole to far point of the eye. Thus, from the far point of the eye, refractive error can be determined.

27. THE OPTOMETER PRINCIPLE Porterfield , in 1759, coined the term ‘ optometer ’ to describe an instrument for measuring the limits of distinct vision. The optical principle on which this instrument was based is now known as the optometer principle. The principle permits continuous variation of power in refracting instruments. In fig.A . The AR based on this principle- use a single converging lens placed at its focal plane instead of interchangable trial lens. In fig.B,C,D , light from the target on the far side of the lens enters the eye vergence of different amount, minus or plus depending on the position of the target.

28. Vergence of light in the focal plane of the optometer lens is linearly related to the displacement of the target. In fig.E , a scale with equal spacing can thus be made which would say the number of diopters of correction.

29. Development O F O PTOMETER The Scheiner’s principle & Optometer principle and their modifications have been used time and again to automate the clinical refraction. ( 1619 – 1759 ) Numerous automated refractors have been devised during the last century. The modern electronic and computerized autorefractometers have rendered the previous optometers obsolete. In general, development of optometers can be grouped as follows: Early refractometers Modern autorefractometers

30. EARLY REFRACTOMETERS Early Subjective Optometers : Developed during 1895-1920, and require patient to adjust the instrument for best focus of the target. Early Objective Optometers : Developed to offer alternative means relying on examiner’s decision. Based on Optometer principle. LIMITATIONS : Alignment problem Irregular astigmatism Accommodation.

31. MODERN REFRACTOMETERS With the rapid development in electronics and microcomputers, a number of innovative methods and instruments for clinical refraction have appeared since 1960s. The computerized AR gives information about patient’s refractive error in terms of sphere, cylinder with axis and interpupillary distance. The modern refractor can be grouped as follows: Objective AR Subjective AR Over the years, objective AR have evolved as high-tech devices as a result of electronic, electro-optical, cameras and computer evolution.

32. A variety of targets have been used for fixation ranging from animations to pictures with peripheral blur to further relax accommodation. Accommodation is most relaxed when patient identifies the scene as one typically seen at a distance which can be achieved by using visual fixation targets composed of photographs or animations of outdoor scenes. All AR now use the fogging technique to relax accommodation prior to objective refraction. This is the reason why patients state that the target is blurred prior to measurements being taken – this is the effect of the fogging lens. Fixation Target & Control of Accommodation

33. procedure Seat the patient at the instrument. Hold and stabilize the chair as the patient sits down, especially if the chair has wheel. Explain the instrument to the patient. If the patient is wearing corrective lenses, ask him/her to remove them before giving the test. Align the AR to the patient’s eye. This can be accomplished in two parts: a . Coarse alignment b. Fine alignment

34. a) Coarse Alignment : Made using the automatic table, the chin rest height adjust, and/or the vertical adjustment knob with the assistant looking from the side of the instrument. b) Fine Alignment : Made by moving the joystick right and left for horizontal or turning it for vertical movements to adjust the instrument to patient’s eye to gain the necessary measurements.

35. Set the autofractometer’s setting according to the patient’s eye by moving the joystick focusing it and reading is noted. At the end of the procedure, the patient should be praised or told things so that the patient know that the test is over and if they have done it nicely or if they have to sit back and relax . The reading is taken thrice and depending upon system, it will either automatically be transferred to the computer or be printed out in a chart. All the readings for the right eye is listed first & the left eye is listed second.

36. NEW INNOVATIONS IN AUTOREFRACTOMETERS : Portable Autorefractor Hand Held Autorefractor Matrix R 20+ Kerato-Autorefractor Rotatable Kerato-Autorefractor

37. ADVANTAGES & DISADVANTAGES OF AUTOREFRACTOMETERS Easy to see differences in eyes activities when light is focused. Quick, painless and simple. Different reading recorded and average is provided. Does not require pupil dilation. Possible to print out reading in prescription. Children cannot remain still for a longer period of time. Reading is not accurate due to accommodation. Does not provide reading in hazy media , opaque cornea, irregular eye, etc. Sometimes provide incorrect readings. ADVANTAGES DISADVANTAGES

38. Video Representation of the procedure….. In the next slide..

39. THANK YOU