Log 3 - Frame Measurements Flashcards
What is MRP and definition
Major Reference Point - ensures that the lens is fit properly decentered. Boxing center of the lens.
What is the formula for Frame difference
Frame difference = A - B
- the greater the frame difference the more rectangular the surrounding box looks
What is the formula for calculating the GCD (Geometric Center Distance)
GCD= eyesize + DBL
What is the formula for binocular decentration of a lens
Decentration = DBC - PD
_______
2
DBC will be nasally or inward if DBC is greater than the PD, if it was smaller the optical center would move out or temporally
What is the formula for monocular decentration of a lens
(OD)(OS) Decentration = DBC
——- - PD
2
Metal Frames with Gold are classified how (karat system)
- Fine Gold - 100% pure gold, often too soft for durability - marked 24
- Solid Gold - 50% gold, 50% metal, θ indicates 10 K Gold and □ indicates 12 K
- Gold Filled - a base metal inside a gold alloy - likely marked 1/10 12 K gold
- Gold Plated - a base material thinly plated with gold
- Gold Flashing - like gold plating but done more quickly using cyanide bath
How should you determine proper frame width?
Width should be approx. equal to the widest bony part of the face.
Patients with oblong faces need frames with greater ____________.
Vertical Depth
The lower the temple “line”, the __________ the face appears.
Shorter
Frames with a dark upper rim and nylon cord bottom help ____________ wide faces.
Lengthen
Recommendations for patients with base-down triangular faces?
Glasses should be approx. same width as lower facial area
Frame color should be dark
Recommendations for patients with base-up triangular faces?
Frame should be minimal, unobtrusive, and light-colored.
To “lengthen” the nose of a frame selection
Choose frame that exposes as much of the nose as possible, or consider a keyhole bridge + dark frame.
To “shorten” the nose of a frame selection
Consider a saddle bridge. Solid color frame with the top of the bridge coming down as far as possible
The angle made by the two sides of the nose when looking at the face straight on is called:
Frontal Angle
The angle made by the widening of the nose from front-to-back when looking at the face from above is called:
Splay Angle
The angle made from the frontal plane of the face to the front of the nose crest when looking at the face from the side is called:
Crest Angle
4 Recommendations for frame size for high-minus wearers?
- Avoid frames with large lenses
- Rounded corners on frames are good
- Avoid frames that are wider than the pt’s face at the temple area
- Avoid excessive decentration
- Aspheric or atoric lenses whenever possible
- Always use anti glare coating
3 recommendations for frame size for high-plus wearers?
- Avoid large lenses
- Avoid frames with effective diameter more than 2mm greater than eyesize
- Avoid frame difference >9mm
- High index lenses
- Aspheric or atoric lenses whenever possible
- Always use anti glare coating
What are the 3 requirements for selecting a frame for a progressive add?
- Minimal vertex distance
- Adequate pantoscopic tilt
- Vertical depth in nasal portion of frame shape
