Opterio

Estimate a spectacle lens base curve (the front surface power) with Vogel's formula, as taught for the ABO exam: spherical equivalent + 6.00 D for a plus lens, spherical equivalent / 2 + 6.00 D for a minus lens, with the nearest half diopter and the steps. An estimate for study; a lab uses the manufacturer's chart. Its card shows the learner the answer and every step, so after calling it don't restate them. Reply with one short sentence that suggests a next step instead, such as a related calculation to try or asking why a step works, unless the learner asks for more.

base_curve

Work out a frame's effective diameter (ED): twice the longest radius from the lens's boxing center to the farthest point of its edge. Give that radius for the exact ED, or the box (eye size A and height B) and how rounded the corners are for an estimate, which always falls between the longer box side and the box diagonal. Decentration is not part of ED; it's added in minimum blank size. Its card shows the learner the answer and every step, so after calling it don't restate them. Reply with one short sentence that suggests a next step instead, such as a related calculation to try or asking why a step works, unless the learner asks for more.

effective_diameter

Work out a spectacle lens power from its front (base) and back surface curves: nominal power F1 + F2, and, given the center thickness and material, the back vertex power F1 / (1 - t/n x F1) + F2. Converts lens clock readings with (n - 1) / (calibration - 1) when the curves came from a lens clock. For optician exam study, with the steps. Its card shows the learner the answer and every step, so after calling it don't restate them. Reply with one short sentence that suggests a next step instead, such as a related calculation to try or asking why a step works, unless the learner asks for more.

lens_power

Estimate the edge thickness of a minus lens or the center thickness of a plus lens from power, material index and diameter with the sag formula (lens treated as flat on one side, the usual exam simplification), and compare lens materials. Its card shows the learner the answer and every step, so after calling it don't restate them. Reply with one short sentence that suggests a next step instead, such as a related calculation to try or asking why a step works, unless the learner asks for more.

lens_thickness

Work out the minimum lens blank size for a frame: MBS = ED + (frame PD - patient PD) + 2 mm, where frame PD = A + DBL. Shows each lens’s decentration and the steps. Its card shows the learner the answer and every step, so after calling it don't restate them. Reply with one short sentence that suggests a next step instead, such as a related calculation to try or asking why a step works, unless the learner asks for more.

minimum_blank_size

Estimate a near (reading) PD from the distance PD and the reading distance with Gerstman's three-quarter rule: each lens insets 0.75 mm per diopter of dioptric demand (1 / reading distance in m), near PD = distance PD - 2 x inset. Also gives the inset table's figure. For reading glasses and bifocal segment inset, as taught for the ABO. Its card shows the learner the answer and every step, so after calling it don't restate them. Reply with one short sentence that suggests a next step instead, such as a related calculation to try or asking why a step works, unless the learner asks for more.

near_pd

Work out induced prism and base direction with Prentice's rule (prism = decentration in cm x power in that meridian) when the eye looks away from the optical center. Handles plus, minus and sphero-cylinder lenses, with steps. Its card shows the learner the answer and every step, so after calling it don't restate them. Reply with one short sentence that suggests a next step instead, such as a related calculation to try or asking why a step works, unless the learner asks for more.

prentices_rule

Combine a horizontal and a vertical prism on one lens into the single resultant prism (R = sqrt(H^2 + V^2), base at arctan(V/H)) in 360-degree notation, or resolve a prism at a base angle back into horizontal and vertical parts. Degrees are read facing the wearer: base in is 0 on a right lens and 180 on a left one. Give horizontal/vertical prisms to combine, or prism and base_angle to resolve. Its card shows the learner the answer and every step, so after calling it don't restate them. Reply with one short sentence that suggests a next step instead, such as a related calculation to try or asking why a step works, unless the learner asks for more.

prism_resolver

Work out a spherical GP (RGP) contact lens power for the NCLE from the K readings, the spectacle Rx and the base curve: tear lens = base curve (D) - flat K, lens power = Rx sphere (minus cylinder, moved to the cornea when over 4.00 D) - tear lens (SAM-FAP), plus the residual astigmatism left over. Base curves convert with 337.5 / r. For study and checking working: it doesn't fit or prescribe contact lenses, which needs an eye care professional, so if someone asks about their own lenses, use your one-sentence reply to say that. Its card shows the learner the answer and every step, so after calling it don't restate them. Reply with one short sentence that suggests a next step instead, such as a related calculation to try or asking why a step works, unless the learner asks for more.

rgp_fitting

Work out the spherical equivalent of a sphero-cylinder prescription (sphere plus half the cylinder), with the steps and the nearest quarter-diopter powers. For optician and contact lens exam study. Its card shows the learner the answer and every step, so after calling it don't restate them. Reply with one short sentence that suggests a next step instead, such as a related calculation to try or asking why a step works, unless the learner asks for more.

spherical_equivalent