20. Single Surface Reduced Eyes Distance from the anterior corneal surface 5.00mm 5.73mm 5.55mm Radius of equivalent surface 4/3 4/3 Refractive index +22.0mm +22.9mm +22.22mm Second focal point F’ -13.0mm -15.7mm - 16.67mm First focal point F +7.0mm +7.2mm +5.55mm Nodal Point N +2.0mm +1.5mm +0.0mm Principal point P Donder’s Listing’s Emsley’s