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Ametropia Examples The length of an axially hypermetropic eye is 20mm. Find the power of the thin correcting lens placed at 12mm from the cornea. A myopic eye is corrected with a thin –8.00D lens at 10mm from the cornea. Find the position of the far point. Find the power of the correcting thin lens if it were to be dispensed at 15mm. The far point of hypermetropic reduced eye is 15cm from the cornea. What would be the correcting thin lens dispensed at 10mm? An object point is half a metre from an axially myopic eye. If a – 4.00 D contact lens imaged the object point on the retina, find the ocular refraction and the axial length of the reduced eye. A myopic eye is corrected with a -6D thin lens at 10mm. Find the position of the far point. What would be the power of the lens if it were dispensed at 15mm. A myope with an ocular refraction of -9.50D has 2 pairs of spectacles dispensed. The first pair is at 15mm and the second is at 9mm. What is the difference in powers between the two pairs? A reduced eye has an axial length of 20.513mm and a power of Fe=+61.00D. What is the type and nature of ametropia? Calculate the power of the spectacle lens required at 12mm to correct the eye for DV. A patient has an ocular refraction of +11.236D and a spectacle prescription of +10.00D. Find the Back Vertex Distance. The optometrist has issued a prescription of +14.25DS with a back vertex distance of 15mm The patient has chosen a frame with a back vertex distance of 9mm. What should the new spectacle lens power be? Step along through the following lens F1=+2.00DS F2=+2.00DS t=6mm n=1.5 Assume parallel light incident at the first surface Trace a ray through the following spectacle lens in air to determine the BVP r1=+70.0mm r2=+105.0mm tc=5mm n=1.49 A thick lens with parameters F1 +10.50D, F2 -6.00D and t=7mm and refractive index 1.5 corrects an eye for distance vision when fitted at 12mm. Calculate the ocular refraction. A patient with an ocular refraction of -6.00D is prescribed a spectacles with a back vertex distance of 11mm. Calculate the spectacle lens power. The spectacles are made with a front surface radius of +30mm and a centre thickness of 4mm with a refractive index of 1.6. Calculate the radius of the back surface