Wong's shit Flashcards
5 criteria for desinging specs?
Functionality aesthetics safety comfort precision
what does ansi stand for
american national standards institute
what is Z80.1
what is Z87
Z80.1 is the code for dress eyewear
Z87 is the code for occupational sfetey
where is the greatest power meridian
solve all tolerance questions using the greatest power as the “sphere” power
what is inadvertent prism power for horizontal and vertical
hori: 0.33, 033, 0.66 total or 2.5mm
vert: 0.33, 0.33, 0.33 total or 1mm
what is the 3 part definition for a base curve
- beginning curve
- always the front curve
- if there are more than 2 curves on the front then it is the flattest
what are the definitons that define the boxing system for measuring frames?
A, B, DBL, ED, GC, GCD, DBC, FPD, datum
what does A+DBL=?
A-longest horizontal B-longest vertical DBL-least distance btwn lenses ED-twice the longest radius GC-geometric centers GCD-geometric center distance DBC-dist btwn center FPD-frame PD datum-half of B A+DBL=GCD GCD=DBC=FPD
what is prism by deviation
vertical imbalance
image jump
- prism by deviation: deviation in relation to power of prism at distance of 1m
- vertical imbalance: human tolerance to prism, esp with vertical aniso
1. when pts eye above datum line and OC on datum line
2. when pt becomes presby and eyes travel vertically towards the near add area of lens and get double vision - image jump: specific to segment itself, same formula F(add)*c(dist seg line to near OC) /10
what is the CPSREI and their primary objective
CPSREI: coalition to prevent sports related eye injuries
- to warn and eliminate the use of street eye wear when engaged in sports related activites.
- most common sports related injury is “finger to the eye”
what is ASTM rep and what do they oversee?
american society for testing matierals
-testing of sport protective eyewear (F803)
what percentage of sports related injuries could have been prevented by wearing sports protective eyewar?
90%
define photochromic
photochromic lenses change from clear indoors to an increasingly darker color as it is exposed to more and more UV radiation
what are polarized lens
polarized lenses eliminate blinding glare from a horizontal refelctive surface
-not designed to eliminate reflection on lens surface itself but BLINDING GLARE pass through lens
what is tint
how is a gray 80 diff from a gray 20
the numeric value associated w/ a tint represents the amount of light that is absorbed.
a gray of 80% absorbs 80% of light and transmits 20% (and is a very dark color lens)
what is an antireflective coating
coating applied to lens surfaces to decrease reflection and allow more light to pass through the elsn and eye
-increases vision, esp at night
what is the range of abbey values
which material are the purest
20-60
- greatest number is purest
- CR-39 and crown glass are purest
what is the advantage to an aspheric lens
produce some power all around but use less weight
- doesnt follow typical definition of base curve (3rd def of being flattest curve)
- the flattest part of lens is towards the PERIPHERY, esp on a plus lens
what is the index to CR39, polycarbonate, and crown class
cr39: 1. 498
crown glass: 1.523
poly: 1.586
what is the index that lens is calibrated
1.530
what is an Abbe value
the lens’ potential to cause chromatic aberration, as the # gets closer to 60, the lens is considered to be more optically pure and has lesser of a chance for the pt to experience the effects of CA
what is specific gravity
sp graveity of a lens is its comparative weight in grams/cubic centimeter
what is the sagitta of an ophthalmic lens
the perpendicular distance for the vertex of a surface to the plane of its knife-edge thickness
