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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