Test 17

1. Charts used for testing contrast sensitivity include:  a. Snellen's chart  b. Logmar  c. Vistech  d. Bailey Hi-Lo  e. Pelli-Robson    answera.F   b.F   c.T   d.T   e.F     2. The following are true:  a. measurement of strabismic deviation in the presence of      high-plus spectacle underestimate the deviation  b. measurement of strabismic deviation in the presence of      high-minus spectacle overestimate the deviation  c. a high-plus lens provide a base-in prism in exotropia  d. a high-plus lens provide a base-out prism in esotropia  e. strabismus is exaggerated cosmetically if the patient wears a      high-plus spectacle.  answera.T   b.T   c.T   d.T   e.T A high spectacle correction can distort the true values of strabismic deviation. If the measurement were performed with a high-plus  spectacle the value is usually underestimated and vice versa for high-minus spectacle. The cosmetic appearance of strabismus is exaggerated with high-plus glasses and made less obvious in patients with high-minus glasses.    3. Combined astigmatic keratotomy and cataract surgery is useful in the      following situation:  a. keratometry:                  44.25/ 46.00 @ 90      cycloplegic refraction:    -2.00/-1.75 X 175  b. keratometry:                  42.00/45.25 @ 10      cycloplegic refraction:    +2.00/+2.50 X 15  c. keratometry:                  43.00/43.75 @45      cycloplegic refraction:    -2.00/+2.00 X35  d. keratometry:                  44.00/44.25@10      cycloplegic refraction:    -1.75/-1.75 X 100  e. keratometry:                   42.00/45.00@100      cycloplegic refraction:     +3.00/-0.50X 90  answera.T   b.T   c.F   d.F   e.T Astigmatic keratotomy can be used to reduce post-operative astigmatism. Before performing the procedure, it is important to know if the astigmatism is contributed by the cornea or the lens. Therefore, it is essential to perform keratometry and refraction preferably  with cycloplegia. a, b and e have significant corneal astigmatism on the keratometry. In both a and b, the refraction shows that the lens contribute little to the astigmatism. In e, the refraction is almost spherical despite the  keratometry, suggesting that the corneal astigmatism is compensated by the lenticular astigmatism. The astigmatism is likely to be manifested following cataract surgery. In c and d, the keratometries are nearly spherical. The refraction suggests that the astigmatisms are  contributed by the lens. Following cataract surgery,  the astigmatisms are likely to be significantly reduced.      4. The following will give rise to with the rule astigmatism following      cataract surgery:  a. a tight corneal suture at 900 b. preoperative keratometry result of 42.00/44.75@80 and      a preoperative refraction of -1.00/-2.00X170.  c. tilting of the implant along its horizontal axis  d. tilting of the implant along its vertical axis.  e. loose suture following temporal extract capsular cataract      extraction  answera.T   b.T   c.T   d.F   e.T Tilting of the implant along the vertical axis produces against-the-rule astigmatism.   5. The following visual fields does not meet driving criteria in the UK:  a. a dense right scotoma  b. bitemporal hemianopia  c. bilateral altitudinal field defect  d. homonymous hemianopia  e. peripheral ring scotoma  answera.F   b.T   c.T   d.T   e.F The minimal criteria for driving in the UK is a visual field  of 120 degrees horizontally and 20 degrees above and below the centre point. It is not essential to have two good eyes.    Return to the main page