OPTOMETRIC REFRACTION

Transcription

1 DIVISION OF VISION SCIENCES SESSION: 2007/2008 DIET: 2 ND OPTOMETRIC REFRACTION VISP208 LEVEL:2 MODULE LEADER: DR GUNTER LOFFLER B.Sc/B.Sc. (HONS) OPTOMETRY AUGUST 2008 DURATION: 2 HOURS CANDIDATES SHOULD ATTEMPT FIVE QUESTIONS PLEASE READ THE QUESTIONS CAREFULLY Students for whom English is not their first language are permitted to use a Standard English/Foreign Language dictionary, e.g. French/English/English/French. Please ensure that the dictionary does not contain any notes or other materials and note that electronic dictionaries are not permissible MATERIALS TO Lined Examination Script Books BE SUPPLIED/ALLOWED: Unlined Examination Script Books Other Materials, e.g. Graph paper, statistical tables (please specify) Page 1 of 6

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3 All questions carry equal marks. 1. Objective Refraction a) i) Outline your procedure for performing retinoscopy in the right eye of a 20 year old patient with a prescription of +1.50/-1.25 x 100. (5) ii) List the most common sources of error made during retinoscopy. (5) b) Subjective refraction Your retinoscopy result for the left eye is: +1.50/-2.00 x 90. The 20-year old patient s actual refractive correction in the left eye is: +1.25/-1.25 x 80. i) Describe (in note form) how you would use the cross-cylinder technique to reach the actual refractive correction. Indicate this patient s likely responses for each step. (5) ii) Describe (in note form) how you would use the Fan and Block technique to reach the actual refractive correction. Indicate this patient s likely responses for each step. (5) 2. a) Interpupillary distance i) Why is it important to measure distance and near PD? (4) ii) Describe how distance and near PD are measured with a facial rule. (4) iii) List 4 clinical situations where monocular PDs should be measured. (2) b) Accommodation i) What clinical methods are available to measure a patient s accommodation function? (6) ii) List the anomalies of accommodation. (4) Page 3 of 6

4 3. Refractive Error Development a) Discuss the clinical methods that can be employed to measure the biometric factors of the eye. (5) b) Discuss the various methods that have been employed to stop the development of myopia. Give some indication of how successful each method has been. (10) c) Briefly describe five ocular complications that are associated with myopia. (5) 4: Retinoscopy a) With the aid of a few simple ray diagrams, show how the speed of the red-reflex movement depends on the position of the patient s far-point relative to the observation stop. (8) b) With the aid of a few simple ray diagrams, show what type of retinoscopy movement do you see if the patient s far point falls at the position of the observation stop. (8) c) The situation described in (b) is a special case of those in (a). How can you describe the speed of the retinoscopy movement in (b)? (4) Page 4 of 6

5 5. Subjective refraction a) Monocular refraction: Your retinoscopy of a 13 year old patient yields: DS VA 6/18 Using a pinhole, you find a visual acuity of 6/5. Explain each step of the following subjective refraction. Your answer should include the questions you ask at each point, any instructions to your patient, the lenses you use, the targets for your patient and what the patient s most likely response would be. You can assume that the patient does not require a cylinder for his prescription BUT you must describe the cross-cylinder test(s), which you would carry out and which would lead you to this conclusion. (10) b) At the end of your monocular refraction, you decide to carry out a duo-chrome test on this patient. Describe, using a diagram including the test, and an eye, the theory on which the test is based. (5) c) Following monocular refractions for both eye, you want to use Polaroid dissociation to balance the refraction of the eyes. Describe, using a diagram, how this test allows each eye to be tested independently. (5) 6. Binocular Refraction a) What is binocular refraction and what are its requirements? State 3 techniques that can be used to carry out binocular refraction. (10) b) What is/are the advantage(s) of binocular over monocular refraction? (4) c) Give an example when binocular refraction might be particularly useful. (3) d) State cases where binocular refraction might not work well. (3) END OF PAPER Page 5 of 6

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