Term
|
Definition
| -the use of narrow ridges or grooves to deviate light like a conventional prism or lens |
|
|
Term
| What are properties of fresnel lenses? |
|
Definition
-each ridge has a different apical angle, increasing towards edge
-base of prism to axis for plus power
-base to edge for minus power |
|
|
Term
| What are fresnel lenses available in? |
|
Definition
| -high power spheres, cylinder or prisms (all high powered) |
|
|
Term
| When are fresnel lenses used? |
|
Definition
- to let Px try new Rx before making final lens
-if conventional lens is too thick, heavy to wear |
|
|
Term
what are advantages of fresnel lenses? |
|
Definition
-inexpensive
-lets Px try before you buy
-light weight
-removable |
|
|
Term
| What are some disadvantages of fresnel lenses? |
|
Definition
-lots of scattered light, decreased VA, contrast
-cosmetic
-can fall off |
|
|
Term
| List a few sources of optical radiation? |
|
Definition
-sunlight
-lighting
-lamps
-arcs, lasers
|
|
|
Term
| What are some photobiological effects of optical radiation? |
|
Definition
-photosensitivity
-photoallergy
-phototoxicity |
|
|
Term
|
Definition
| -to have an effect on tissue optical radiation must be able to reach it |
|
|
Term
| What kind of optical radiation damage would you expect with mutagenic change in cell nucleus? |
|
Definition
|
|
Term
| What are the effects of UVC? |
|
Definition
-acute only
-photokeratoconjunctivitis
-mutagenic to cell nucleus
-cell death
-sunburn |
|
|
Term
| What type of light damage is might give cortical cataracts and a basal cell carcinoma? |
|
Definition
|
|
Term
| What are acute UVB exposure symptoms? |
|
Definition
-reversible cataract
-photokeratoconjunctivits
-welder's flash
-sunburn |
|
|
Term
| What type of light exposure might give a ptergyium or pinguecula? |
|
Definition
-chronic UVB
-may also give band keratopathy |
|
|
Term
| a nuclear sclerotic (brunescent) cataract is a result of what type of light exposure? |
|
Definition
|
|
Term
| What might cause malignant melanoma? |
|
Definition
-UVA chronic exposure
(rapidly invasive and metastatic, and may occur in eye) |
|
|
Term
| What is the most common type of injury due to visible light exposure? |
|
Definition
| -photochemical (temporary visual loss) |
|
|
Term
| What are acute forms of visible light damage? |
|
Definition
| -retinal burns: photochemical and thermal |
|
|
Term
| What might happen if a person looks at a solar eclipse? |
|
Definition
| -retinal burn (photochemical) |
|
|
Term
what kind of damage would you expect with a thermal retinal burn? |
|
Definition
| -permanent with visual loss |
|
|
Term
| IR radiation have _______ effects only. |
|
Definition
|
|
Term
| Thermal retinopathy can be due to what? |
|
Definition
| -IRA or long visible wavelengths |
|
|
Term
| What is luminous transmittance? |
|
Definition
| -takes into account spectral sensitivity eye of visual system. Applies only to visual system |
|
|
Term
| What are some uses of tinted lenses? |
|
Definition
-cosmetic
-therapeutic
-occupational
-recreational |
|
|
Term
| What is a type of tinted lens? |
|
Definition
| -through and through (solid, metal oxide addition) |
|
|
Term
| What is a surface coating like in tinted glass making? |
|
Definition
-vacuum deposition of dielectric coating on front
-anti reflection coating on back
-can be abraded |
|
|
Term
| What are the ways to make tinted lenses? |
|
Definition
-surface coating
-dye tints
-solid (added to resin before polymerization) |
|
|
Term
| What are the possibilites for using tinted glasses? |
|
Definition
-cosmetic (80% T)
-sunglass (60% - 20% T)
-vision enhancing (polarizing or spectrum limiting) |
|
|
Term
| What is the ideal sunglass tint? |
|
Definition
-UV absorption
- neutral density |
|
|
Term
| What are polarizing lenses good for? |
|
Definition
-driving, and swimming
-reduce glare |
|
|
Term
What is a spectrum limiting tint?
|
|
Definition
-increases contrast, reduces haze
-good for skiing, shooting etc.. |
|
|
Term
| What is anisotropic media? |
|
Definition
| -behaves differently for different planes of vibration and/or different directions of propogration |
|
|
Term
| What are some type of anisotropic media? |
|
Definition
-dichroic crystals
-E-sheet polaroid |
|
|
Term
| True or false. E vector parrallel to grid polarizer is transmitted? |
|
Definition
| -False. Is E vector 90 degrees to grid that is transmitted |
|
|
Term
| Birefringence is a property of what? |
|
Definition
|
|
Term
| What is the brewster angle? |
|
Definition
| -angle of incidence at which reflected beam of light has its maximum degree of plane polarization |
|
|
Term
| What type of polarizing filter should sunglasses have? |
|
Definition
| -vertical to minimize horizontal polarized light |
|
|
Term
| What are photochromic lenses? |
|
Definition
| -lenses that change density on exposure to light or UV |
|
|
Term
| What type of materials are in photochromic lenses? |
|
Definition
-borosilicate or aluminum phosphate glass
-sliver halide additive |
|
|
Term
|
Definition
| -damage by UV (B) radiation |
|
|
Term
| When does spectacle reflection image present a problem? |
|
Definition
-when it near fixated object
-intense enough to see
-can be made clear by accommodation |
|
|
Term
| What is the Fresnel equation? |
|
Definition
| -describes intensity of light of reflected light in two planes of polarization |
|
|
Term
| What are types of reflection you can get? |
|
Definition
| -from sources behind and in front of lens |
|
|
Term
| What are the two types of behind the lens reflections? |
|
Definition
-off the back surface of lens
-through back surface off front surface and through back surface |
|
|
Term
| What are solutions to reflection from sources behind lens? |
|
Definition
-frame with smaller eye size
-fit lens as close to eye as possible
-increase faceform |
|
|
Term
| What are possible reflections from objects in front of lens? |
|
Definition
-refraction at front, two internal reflections
-reflection off eye and back surface of lens
-reflection off the eye and front surface of lens |
|
|
Term
| What are possible solutions to reflection from images in front of lens? |
|
Definition
-change base curve
-change pantoscoptic tilt
-change vertex distance to defocus image
-change faceform
-use prism to shift image |
|
|
Term
| Which types of lenses, glass or plastic get scratched more easily? |
|
Definition
|
|
Term
| Which type of plastic lens is hard enough that a scratch resistant coat is an option only? |
|
Definition
|
|
Term
| List a few scratch restistant coatings available. |
|
Definition
-Lacquer (varnish)
-hard coat
-fused silica
-dip coat*
-spin coat
-spray coat
-in-mould hard coat |
|
|
Term
| What is done to prepare a lens for SRC? |
|
Definition
-lens cleaning
-outgassing |
|
|
Term
| Which coat requires high speed rotation to spread lacquer? |
|
Definition
|
|
Term
| What is the back surface most susceptible to in terms of wear and tear? |
|
Definition
|
|
Term
| What is a possible optical effect of SRC? |
|
Definition
| -if hard coat index does not match lens substrate, then intensity of surface reflections may change |
|
|
Term
|
Definition
| -relative difference in size or shape of image between eyes |
|
|
Term
| What is the ocular image? |
|
Definition
| -final perceptual cortical image of the 'retinal' image |
|
|
Term
| Name factors determining size of ocular image. |
|
Definition
-dioptric system of corrective lenses
-dioptric system of eye
-distance of object from the eyes
-anatomical and neurophysiological properties of retina |
|
|
Term
What is Physiological Aniseikonia?
|
|
Definition
-difference in ocular image size due to image disparities introduced by lateral separation of the eyes
-arises as one looks from side to side |
|
|
Term
| How is Acquired or Optical Aniseikonia induced? |
|
Definition
| -difference SM results in different ocular image sizes |
|
|
Term
| What is inherent optical aniseikonia? |
|
Definition
| -aniseikonia dependant on dioptrics of the eyes |
|
|
Term
What is meridonial astigmatism? |
|
Definition
| -when two eyes have different axis of astigmatism |
|
|
Term
| How can we change the position of nodal points? |
|
Definition
-monocular aphakia
-monocular lens |
|
|
Term
| How may the axial length of the eye change to induce aniseikonia? |
|
Definition
-scleral buckle
-progressive myopia |
|
|
Term
| What is anatomical aniseikonia? |
|
Definition
| -unequal distribution of retinal elements |
|
|
Term
| What are some symptoms of aniseikonia? |
|
Definition
-headaches, asthenopia, photophobia, diplopia, confusion
-fatigues, nausea, nervousness |
|
|
Term
| What are the two factors of spectacle magnification? |
|
Definition
| shape factor and power factor |
|
|
Term
|
Definition
-magnification due to a thin lens of power Fv' placed a distance dv in front of eye
-greatest effect with a high minus lens |
|
|
Term
|
Definition
| -magnification due to an afocal lens of index n, thickness t and front surface power F1 |
|
|
Term
|
Definition
-ratio of image size in corrected ametropia, to image size in emmetropia
-perception of the world through corrected lenses |
|
|
Term
| Describe Axial ametropia and how to correct it. |
|
Definition
-eye is physically too long or short
-correct with spectacles
-induce aniseikonia with contact lens
-RSM = 1 for spectacles |
|
|
Term
| Describe refractive aniseikonia and how to correct it. |
|
Definition
-difference in power between eyes, same length
-contact lens eliminates aniseikonia
-spectacles induces aniseikonia
-RSM = SM |
|
|
Term
| How would you correct +3% aniseikonia OD? |
|
Definition
|
|
Term
| How would you correct -3% aniseikonia OD? |
|
Definition
| -place 1.03x mag in front of left eye |
|
|
Term
| What are Iseikonic lenses? |
|
Definition
| -lenses that correct aniseikonia |
|
|
Term
| What are limits in designing Iseikonic lenses? |
|
Definition
-available base curves
-limits on centre thickness
-limits on edge thickness
-residual dynamic aniseikonia |
|
|
Term
| What are the four methods of constructing multifocals? |
|
Definition
-fused (glass only)
-one piece (glass or plastic)
-cemented (glass of plastic)
-two piece usually glass |
|
|
Term
| Name some terminology of multifocals. |
|
Definition
| -inset, seg inset, total inset, seg drop, MRP, seg width, seg height |
|
|
Term
| Where do you place the seg line in adult bifocals? |
|
Definition
| -lower lid margin or lower limbus |
|
|
Term
| Where would you place the seg line of a trifocal? |
|
Definition
|
|
Term
| What are the four methods of construction of multifocal lenses? |
|
Definition
-fused: glass only
-one-piece: glass or plastic
-cemented: glass or plastic
-two piece: usually glass |
|
|
Term
| What kind of image jump do we see in an add from a bifocal? |
|
Definition
-image jump due to BD prism
-image move slightly up |
|
|
Term
| Who will be more comfortable looking through bifocals due to prismatic effect? |
|
Definition
|
|
Term
| What are some methods of correcting vertical imbalance at near? |
|
Definition
-fresnel press-on prism
-slab off
-dissimilar seg types and or heights |
|
|
Term
| What are some features of the soft design of PALs? |
|
Definition
-long corridor
-shorter adaption time
-very good for early presbyope
-assumes dynamic vision |
|
|
Term
| What are features of hard design PALs? |
|
Definition
-short corridor
-longer adaptation time
-assumes static vision
-favored by advanced presbyope |
|
|
Term
| What is ANSI Z80.1 used for? |
|
Definition
| prescription lenses and dress lenses |
|
|
Term
| What is ANSI Z87.1 used for? |
|
Definition
-safety eyewear (occupational and educational, and non presecription eye and face protection devices
-lenses may not be tinted unless prescribed
-Rx and non Rx |
|
|
Term
|
Definition
| -non Rx sunglasses and fashion eye wear |
|
|
Term
|
Definition
| -canadian standard for industrial eye protection (Rx and non Rx) |
|
|
Term
|
Definition
| -eye and face protectors for hockey |
|
|
Term
|
Definition
|
|
Term
| What american standards would canadians use as technical requirements for dress lenses and frames? |
|
Definition
|
|
Term
| What radiation reaches the anterior eye? |
|
Definition
|
|
Term
| What radiation reaches the posterior pole of eye? |
|
Definition
| UVB, UVA, visible and IRA |
|
|
Term
| What is the difference between spectral transmittance T and Transmitance T? What about luminance transmittance? |
|
Definition
-spectral is incident energy at a given wavelength where transmittance T is incidence or radiant energy within a given waveband
-takes into account spectral sensitivity of eye (applies only to visible spectrum) |
|
|
Term
|
Definition
| -logarithmic form of luminous transmittance |
|
|
