Low Vision Evaluation

1. Low Vision Evaluation Ms MB JAN- 24/01/2012

2. Content • The difference between a low vision exam and a regular exam • The Case History • Evaluating visual performance

3. 4. Evaluating visual performance • Visual acuity • Visual field evaluation • Contrast sensitivity • Colour vision 5. Objective refraction 6. Subjective refraction 7. Ocular health evaluation

4. OUTCOMES At the end of this lecture, learners should be able to:

5. Discuss the importance of a case history specifically for a low vision patient • Discuss specific questions that will be asked to a low vision patient • Describe the different techniques and charts used to measure a low vision VA (near, distance, aided, unaided etc.)

6. Discuss the need for evaluating visual fields in a LV patient • Discuss methods and techniques for evaluating visual fields in a LV patient • Discuss the need for evaluating contrast sensitivity in a LV patient

7. Discuss the need for evaluating colour vision in a LV patient • Discuss the methods and techniques used for evaluating colour vision in a LV patient • Discuss the objective refraction techniques available to the low vision optometrist • Discuss the technique and implications of radical retinoscopy

8. Discuss the method used for refracting a low vision patient • Analyze a low vision case based on a history, and then decide on and describe the most appropriate evaluation routine for a specific patient • Distinguish between a low vision refraction routine and a normal refraction routine • Explain the concept of JND (just noticeable difference) and be able to use it to test a low vision patient

9. The pre-evaluation information sheet • It sets clear boundaries on what you will be able to do • Draw up your own sheet in practice

10. Information sheet • The appointment duration • Schedule appointment around a time when patient’s vision is stable • Bring with old glasses, magnifiers – even if not usable anymore

11. Think about specific problems the patient is experiencing • Start thinking in terms of goals – write down what you would like to achieve

12. Bring along special materials he/she want to be able to use (E.g. books) • Bring along a report from the ophthalmologist

13. Follow-up visits or training sessions with equipment may be necessary • State that there are no miracles, we will use your remaining vision effectively

14. The difference between a low vision examination and a regular exam Give the differences and explain each point given

15. Disadvantages of using phoropter • Why not phoropter?

16. Case History NB. Very important, It has to be even more detailed

17. The patient interview • The successful patient interview has 3 functions (Cohen-Cole) • Gathering data to learn about the patient’s problem • Developing rapport, and responding to the patient’s emotions • Educating patients about their problems, and motivating them to adhere to the prescribed treatment

18. Interview techniques • Both parties should be seated at eye-to-eye height • Seating should be comfortable • Control lighting – not too dim or bright • Carefully observe the patient

19. Use both open-ended and specific questions • May be emotionally charged • Note taking should be done subtly

20. Be alert to inconsistencies • Take sufficient time that patient doesn’t feel rushed • BUT keep it brief – old people tire more easily • Use positive language • Question in a friendly, enthusiastic manner

21. Adjust pace to that of patient. • Don’t use medical jargon, explain patient’s condition if they do not understand it • Never give false reassurances • Primary aim is to help patient – don’t fear to be inquisitive – but respect privacy too!

22. The purpose of the case history Why is it important to take LV case history?

23. The real questions you want answered are: • What does the patient want? • What does the patient need? • What is the real reason for the patient’s visit?

24. Information required • Basic identifying information • Name, address etc • Who accompanied the patient? • Support system / self-sufficient? • Relative, friend, counselor, teacher etc • Contact person • Provide insight into history

25. Referral source • Send thank you note • Reports • Diagnosis of eye condition • In patient’s own words • See if patient understands condition • Begin with patient education on problems.

26. Visual history • Duration • Previous care • Nature of vision loss (congenital or acquired? Stable or progressive?) • Fluctuation of vision

27. Problems with color vision • Is there a preferred eye? • Problem with glare or lighting? • Current glasses / low vision aid • Current visual capability (specific task-related questions) • Smallest print read? • Newsprint • Headlines • Large print

28. Able to watch television? • What viewing distance? • Size screen? • Can you recognize faces at a distance? • Can you see well enough to get around? • Family visual history

29. 5. Medical history • Undergoing treatment for medical condition? • Does the patient have a disease with known ocular implications? • Is there medical problems that might affect the use of a LVA? (stroke) • Family history • Allergies and drug sensitivities • Medications (many systemic drugs have ocular side-effects)

30. 6. Employment or school history • Investigate the effect the visual loss has on the work/school performance • Investigate the use of appropriate devices to alleviate problems • Some older people might want to continue their education • Avocations • Hobbies or activities

31. 8. Social assessment • Does the patient live alone or with family? • How is daily life affected by the vision problem? • Does the patient have a support network? • Is the patient’s independence threatened?

32. 10. General appearance of patient • Well groomed, clean or untidy? • Food stains – cannot see that level of detail • Poor grooming - emotional disorders such as depression • Walk without assistance? • Mobility • Does the patient look ill?

33. Patient goals (Chief complaint) • Possibly the most important part of the case history • Allow a full elaboration of the visual disabilities • Patient’s new problem should be fully investigated

34. After the patient has completed a list of complaints, several issues should be addressed regardless of the patient’s failure to mention them • Distance vision • Near vision • Orientation and mobility skills • Glare • Lifestyle

35. External evaluation • Some do this just after VA’s, but depends on circumstances. Give an example • Brief look into the eyes, do not shine bright lights into the eye

36. Note the following about the eyes: • Position of eyes (strabismus) • Pupil – size, reaction to light, appearance, • Cornea – opacities: size, density, position • Lens – opacities, position (especially IOL) • Motility – strabismus, nystagmus, restrictions • Binocular dysfunction is usually of secondary importance

37. Evaluating visual performance

38. Why? • Compare with normal performance, or accepted standard (eg driving regulations) • Set a baseline for monitoring the condition • Quantify the patient’s own subjective impression of visual performance

39. Early detection and diagnosis of (other) visual disorders • Assessment of the benefits of an intervention (medical, surgical, rehabilitation) program • Predicting visual function in every day tasks

40. Visual acuity

41. Visual acuity 1.Why do we want to accurately measure acuity? 2. Limitations of VA measurement 3. Factors affecting VA measurements 4. Distance Visual Acuity 5. Near Visual Acuity

42. Why do we want to accurately measure acuity? • It establishes a baseline from which to monitor pathology • Used to predict the magnification level of the optical devices that will be required to achieve the patient’s goals • Often requested by other agencies to establish legal blindness, driving privileges, job eligibility etc.

43. Limitations of VA measurement • The clinical acuitydoes notgive an accurate indication of the functional acuity. Explain • Clinical measure of person’s ability to read letters under controlled circumstances • It doesn’t always correlate with daily activities

44. Function can be influenced by differences in contrast sensitivity, glare sensitivity, motivation and numerous other factors • VA can vary due to test setting, illumination, doctor-patient relationship and target contrast

45. Factors affecting VA measurements

46. How does each of the following factors affect VA measurement? • Lighting • Optotype • Mental state of the patient • Instructions to patient/attitude / encouragement • Glare recovery • Educational level • Recognition/memory/speech • Motivation

47. Distance Visual Acuity • VA Notations • Acuity chart design • Currently used charts • Measuring distance VA

48. VA Notations • Snellen • Either metric or imperial • We use imperial (feet) • LogMar (logarithm of the minimum angle of resolution) • Decimal: Snellen fraction • Angular (specified in minutes of arc) • Not used clinically

49. Acuity chart design The following aspects of chart design can be considered • Optotype – • style of print and selection of letters • Should yield equivalent results to Landolt C • Number of letters per row • Equivalent – equal task progression • 5 good clinically

50. Sequence of Letters • not form words/part of words • Optotype Size • 0.1 logarithmic progression of character size • Accurate measurements at both standard and non-standard test distance • Letter spacing • systematic