10 a lens is to be made with front surface power 10d

10. A lens is to be made with front surface power +10D, back surface power ‐5D, axial
thickness 9 mm, and refractive index 1.5. Find the ocular refraction K if this is a
correcting lens fitted 12 mm from the eye.
Astigmatism
1. Transpose the following prescriptions to minus cylinder and plus cylindrical forms:
(a) +2.00/+1.00 X 90
(b) 4.00/–2.50 X 180
2. Draw the power crosses for
(a) ‐3 /+5 X180
(b)
+3/-5X90
3. A lens has the following formula: –1.00/–1.00 X 90
(a) Draw a lens cross
(b) Write the prescription in the plus‐cylinder form
4. A prescription reads +11.00/‐2.00X180 at 14mm. What will be the modified power in
12 mm ( suitably rounded off)?

VISN1221 (2018) Set2
(Ans. +11.24/‐2.08 X 180, Rounded off value: +11.25/‐2.00 X 180)).