This card is scientifically designed using the Bailey-Lovie format. It uses Sloane letters and is a geometric or logarithmic progression of sizes. The lines change size in 0.1 log-unit steps so the line above a given line is 1.26 times larger than the line below. What this means is that you can use this card at any distance using M notation. The letters are roughly equal in legibility. The rows are marked in M notation and in 20 ft equivalent acuities. They are 20 ft equivalent acuities if the card is held at 40 cm (16 in). There is a number chart for use with very young children or illiterates. There is also a reading chart for assessment of reading ability. The font used is Times New Roman, a typical font used in newspapers & books. You need to remember that reading acuity is not necessarily the same as single –letter chart acuity. The stroke widths are not 1/5 of the height of the letter like they are in the single-letter chart. Patients with macular lesions (e.g., AMD) may have a reading acuity that is significantly worse than their single-letter acuity. Thus this is used in evaluating visual impairment or functional acuity rather than visual acuity. The reading card is designed using principles similar to those used for the Minnesota Low-vision Reading test (MN-READ) . Thus this card can be used to obtain a quick & accurate assessment of a low-vision patient’s reading speed. There is a Tumbling E chart for use with children & illiterates. At one end of the card there are these half-moon shaped objects used to assess pupil size. Using this method is better than trying to measure the pupil diameter with a millimeter rule. There is also a millimeter rule on the other side of the card for measuring inter pupillary distances (PDs), inter palpebral fissure distances, & corneal diameters.
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