PR-48 Loose prism set, 48 prisms
A set of 48 loose trial prisms from 0.25 to 10 prism diopters, in white plastic rims with the power on each tab, on a wooden tray in an aluminum case. For measuring and trying prism corrections in a trial frame.
Delivery, packing and documents
What the PR-48 offers
48 prisms
Two rows of prisms either side of the power strip: 0.25 to 4.00 Δ in 0.25 Δ steps, then 4.50, 5.00, 5.50, 6.00, 7.00, 8.00, 9.00 and 10 Δ.
Marked tabs
The power is marked on each white plastic rim tab.
Wooden tray, aluminum case
A labeled wooden tray in an aluminum case.
A closer look at the PR-48
0.25 to 10 Δ
Two rows of prisms either side of a labeled power strip, from 0.25 to 10 prism diopters.
PR-48 in figures
Published specifications. Anything not listed here is confirmed in writing on your quotation, never estimated.
The power list follows the tray label; the lens-by-lens list is confirmed in writing on your quotation.
PR-48
- Prisms
- 48
- Range
- 0.25 Δ to 10 Δ
- Powers on the tray
- 0.25 to 4.00 Δ in 0.25 Δ steps; 4.50, 5.00, 5.50, 6.00, 7.00, 8.00, 9.00, 10 Δ
- Rims
- White plastic
- Tray
- Wood
- Case
- Aluminum
Working with loose prisms
How it works
One prism diopter deviates light by 1 cm at a distance of 1 m. Light bends toward the base of the prism, and the image the patient sees moves toward the apex.
Loose prisms go into a trial frame, or are held before the eye, to measure a deviation or to let the patient try a prism correction before it is prescribed. Hold them consistently: the Prentice position, perpendicular to the visual axis, is used for glass prisms.
Stacking two prisms in the same direction does not simply add their powers. Split the prism between the two eyes instead, or use a single stronger prism.
Check before you order
- The range against the corrections you prescribe: up to 10 Δ here.
- Small steps at the low end: 0.25 Δ steps to 4.00 Δ.
- That the prisms fit your trial frame.
Good practice
- Mark the base direction you intend before placing the prism.
- Hold or mount the prism in a consistent position.
- Split larger corrections between the two eyes.
- Return each prism to its slot after use.
Care and maintenance
- Handle prisms by the rim tab, and clean them with a soft lens cloth.
- Keep the case closed and dry.
Background sources: Prisms (StatPearls, NCBI Bookshelf) · Trial frame refraction: more than just “1 or 2?” (Cybersight, Orbis)
Often ordered with the PR-48
PR-48 questions
What is in the PR-48?
48 loose prisms from 0.25 to 10 Δ, in white plastic rims on a labeled wooden tray, in an aluminum case.
How is a prism set different from a prism bar?
A prism bar is a row of prisms in one block, used mainly to measure a deviation. Loose prisms go into a trial frame one at a time, so the patient can try a correction.
Can I stack prisms?
Stacking prisms in the same direction does not simply add their powers. Split the prism between the eyes, or use one stronger prism.
Do the 266-lens trial sets include prisms?
Yes, from 0.5 to 8 Δ. The PR-48 adds finer steps and prisms up to 10 Δ.