<prompt> The normal value of Arden index is15-JanLess than 18.5More than 1.85  <response>: Arden ratio Maximum height of light peakMinimum height of dark trough x 100 Normal curve values are 185 or above. Subnormal curve values are less than 150. Flat curve values are less than 125. Reference : AK KHURANA COMPREHENSIVE OPHTHALMOLOGY, Edition4 , Page-490 