Objective structured practical question (ospe)
- 1. Objective Structured Practical Question (OSPE) Topic: Optics According to the course curriculum of Bangladesh College of Physician & Surgeon (BCPS)
- 2. AUTHOR: Dr Md Anisur Rahman Anjum. MBBS (Dhaka Medical College). DO (Dhaka University) FCPS (EYE) Associate Professor National Institute of Ophthalmology Dhaka, Bangladesh. Chamber: Mojibunnessa Eye Hospital House: 18 Road: 6. Dhanmondi, Dhaka, 1205. Bangladesh. Email: [email protected] Cell: 01711-832397 7/14/2014 [email protected]
- 4. Question The following are the results of the retinoscopy on a 20 year-old man using a streak retinoscope.(Assuming a working distance of 2/3 metre) OD With the streak in the vertical meridian and sweep horizontally, the retina reflex is neutralized with +0.50D. With the streak in the horizontal meridian and sweep vertically, the retina reflex is neutralized with -1.00D. 7/14/2014 [email protected]
- 5. Question OS With the streak orientated at 30o and sweep at 120o, the retina reflex is neutralized with +1.00D. With the streak orientated at 120o and sweep at 30o, the retina reflex is neutralized with -0.50D Question: 1 Draw the power cross (taking into account the working distance). = 5 Question: 2 Write down the glasses prescription for this patient (using negative cylinder) = 5 7/14/2014 [email protected]
- 6. Answer • the power of the cylinder is 900 to the axis • 2/3 meter is equivalent to -1.50 which has to be taken off) 7/14/2014 [email protected]
- 8. • OD = -1.00 Dsph/-1.50 Dcyl 90 • OS = -0.50 Dsph/-1.50 Dcyl 120 7/14/2014 [email protected]
- 10. Question Calculate the spherical equivalent of the following prescriptions and draw the power cross for each. a. +2.50 / -1.50 X 80 b. -4.00 / + 6.00 X 90 c. +1.50 / -3.50 X 45 7/14/2014 [email protected]
- 12. Answer a. +2.50 / -1.50 X 80 = +1.75 (spherical equivalent) b. -4.00 / + 6.00 X 90 = -1.00 (spherical equivalent) c. +1.50 / -3.50 X 45 = -0.25 (spherical equivalent) • To draw the power cross remember that the power of the cylinder is 90 degrees to the axis. The spherical equivalent is calculated by adding the value of the sphere and half the value of the cylinder.) 7/14/2014 [email protected]
- 14. Convert them into spectacle forms with minus cylinder notation • Working distance is 67 cm 7/14/2014 [email protected]
- 15. 1) The power crosses translate to spherocylindrical corrections (with minus cylinder) of RE +1.50 / - 4.00 X 135 LE -0.75 / -1.25 X 90 • As the working distance is 2/3 meter, -1.50 D is subtracted from the above giving RE PL / -4.00 X 135 LE -2.25 / -1.25 X 90 7/14/2014 [email protected]
- 16. 2) The power crosses translate to spherocylindrical corrections (with positive cylinder) of RE -2.50 / +4.00 X 45 LE -2.00 / +1.25 X 180 • As the working distance is now 1/2 meter, - 2.00D is subtracted from the above RE -4.50 / +4.00 X 45 LE -4.00 / +1.25 X 180 7/14/2014 [email protected]
- 18. Question A 18 year-old university student presents to the optician one week before his final examination complaining of intermittent double vision and poor distance vision. He was seen one month earlier and the refraction was emmetropic. Q: 1 What is the most likely diagnosis? Q: 2 What treatment would you prescribe? 7/14/2014 [email protected]
- 19. Question A 40 year-old myopic woman is recently prescribed soft contact lenses for the first time. She returned two weeks later and complains that her reading vision is not as good as with her glasses. Retest shows her visual acuity to be 6/6 in both eyes with the contact lenses and the lenses were of the right prescription and well-fitted. Q: 3 Why does she have problem reading with her contact lenses but not with her glasses? 7/14/2014 [email protected]
- 20. Answer Ans: 1 Accommodation spasm. (When the symptoms occurs the patient is likely to have constricted pupils and esotropia. The spasm can be broken with cyloplegia.) Ans: 2 The following treatment is useful: Frequent looking up from work or Prescription of reading glasses Ans: 3.The patient is pre-presbyopic. Myopes require less accommodation with glasses than contact lenses. In addition, the prismatic effect (base-in prism) offered by the concave glasses assist convergence during reading. • 7/14/2014 [email protected]
- 22. Question A 15 year-old emmetropic boy has an amplitude of accommodation is 30 D. Q: 1. What is his range of accommodation? Another 20 year-old man has a +10 D hypermetropia with 20 D amplitude of accommodation. Q: 2. What is his near point and the range of accommodation when he is not wearing the spectacle correction? Q:3 What is his near point and the range of accommodation when he is wearing his +10.00 dioptres?7/14/2014 [email protected]
- 23. Answer Answer: 1 Infinity to 3.3cm. =3 (The range of accommodation is the linear distance between the far point and the near point. In the absence of accommodation, the boy is in focus at infinity. With maximal accommodation, he is in focus at 1/30 = 0.033m = 3.3cm) Answer:2. 10cm = 3 (To be in focus in infinity, the man needs to use up +10.00D of his accommodation amplitude. As a result, he has only 20 - 10 = 10 D for near vision. His near point is 1/10 = 0.10 m = 10 cm) 7/14/2014 [email protected]
- 24. Answer Answer: 3. The near point is 5 cm and the range of accommodation is infinity to 5 cm. = 4 (With hypermetropic correction he does not need to use up any of his accommodation and can therefore use all the 20 D for near vision. The near point is therefore 1/20 = 0.05m = 5cm. The range of accommodation is therefore from infinity to 5 cm) 7/14/2014 [email protected]
- 26. This is a concave mirror, 5 objects are placed in 5 different location, Q:1 Write down the location of the images. Q: Write down where it will be real and virtual 7/14/2014 [email protected]
- 27. Answer • Case 1: Between C and F. REAL IMAGE • Case 2: Image will be at C. REAL IMAGE • Case 3: Image will be beyond C. REAL IMAGE • Case 4: No image will be form • Case 5: the image will always be located somewhere on the opposite side of the mirror. • VIRTUAL IMAGE 7/14/2014 [email protected]