Face Form Angle - Simple Chart

Face Form Angle is the same as the Bow Angle of a spectacle frame front. herewith I wish to share to basic methods.

Improvise with a simple chart.

Frame Front Reference

1. Place the frame with the top rim of the frame on the chart as shown in the picture.  
2. Ensure the left bridge/rim joint is position on the little black dot somewhere in the middle of the chart.
3. Whilst keeping the left bridge/rim joint in that position, move the right rim so that the nasal and temporal ends of the rim are position on any of the same broken lines.
4. Simply check out the line that meets the temporal end of the left rim for FFA values

Face Form Angle - Standard Tool

Face Form Angle is the same as the Bow Angle of a spectacle frame front. herewith I wish to share to basic methods.

Suggested method by ophthalmic lens manufacturers, using standard tools.

Frame Front Reference

1. Place the frame with the top rim of the frame touching the tool's table, as that shown in the picture.
2. Ensure the left bridge/rim joint is position on the little black dot somewhere in the middle of the tool.
3. Whilst keeping the left bridge/rim joint in that position, adjust the right rim so that the nasal and temporal end of the rim are position on any and the same broken lines.
4. Now move the lever on your right side so that the line in the middle of the lever meets the temporal end of the left rim.
5. The number indicated by that line on the tool is the Face Form Angle.

Pupil Position - PD

Correct eye point position is of utmost importance in progressive lenses fitting.

PD measurement - what can go wrong.

Due to various reasons wearers head position can be in wrong positions, these incorrect lateral head position can lead to substantial PD measurement errors. The diagrams below are clear illustrations of these.

• Diagram on your left indicate the normal and correct position.
• Diagram in the middle indicate the user's head panned to his left, this will result in induced monocular PD values, which may be not required.
• Diagram on your right indicate the user moving towards his left, this position also suggested unwanted monocular PD values. *Possibly to the right too.

I will conclude with basic guidelines to follow when performing PD measurement:

• Assure that the patient's nose and yours are in line and aligned perpendicularly to your face plane.
• Assure that your's and the patient's face plane are the same.
• Record monocular PD values.
• Last but not least, correct use of a PD measurement tool, popularly known as "Pupillometer" can help eliminate unnecessary errors, and possibly quicken the PD measuring process.
  

Pupil Position - Fitting Height

Correct eye point position is of utmost importance in progressive lenses fitting.

Fitting Height measurement - what can go wrong.

Wearer's vertical head position can lead to substantial variance too. The diagrams below are clear illustrations of these wrong positions.

Face Form Angle - Help

If your still lost in all the tutorials, just take a picture of the spectacle frame showing the curvature of the frame front - as indicated in the picture below. Submit this picture to your buying representatives, assistance to measure the FFA is readily available.

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Pantoscopic Tilt - Help

If your are still lost after all the tutorials, simply take a picture of the wearer's side profile - as that indicated in the sample picture below. Please remember to frame a vertical items in the background of your picture. Examples of verticals are door frames, display panels, wall corners and more. Submit this picture to your purchase representative, to receive assistance to measure pantoscopic tilt.

Pantoscopic Tilt - Standard Tools

Rodenstock Impression Measuring Kit

1. Align the gauge so that reference line runs parallel to the vertical frame front
2. Assure that the the space between the upper rim and the ref line, and that at the lower rim and the ref line are the same.
3. Keep the wearer's head in a normal gazing position - not tilt too much backwards or tipped too much forward.
4. The center of the metal ball indicates the PT value in degrees