Final answer:
The power of the tear lens is -0.50 D for every 0.05mm difference in curvature between the contact lens and cornea. For a farsighted prescription of 0.750 D, the tear layer contributes to the total power needed for ideal vision, just like for a nearsighted prescription of -4.00 D where the far point is 22.5 cm.
Step-by-step explanation:
The power of the tear lens is approximately -0.50 diopters (D) for every 0.05mm radius-of-curvature difference between the base curve of the contact lens and the central curvature of the cornea (K). If the contact lens prescription for a mildly farsighted person is 0.750 D and the near point is 29.0 cm, the power of the tear layer is considered in the total corrective power needed for ideal vision when a contact lens is fitted. Therefore, if the correction is ideal, which includes the tear layer, it should result in the desired near point of the person's vision without additional correction needed. In the case of a nearsighted person with a prescription of -4.00 D and a far point of 22.5 cm, a similar calculation would be made, considering the power of the tear layer for an ideal correction.