Jackson’s Crossed Cylinder
Jackson’s crossed cylinder is one of the most enduring instruments in the history of optometric refraction. Eye doctors have used it to refine the axis and power of astigmatism for well over a century. This example dates from the last half of the 1900s and remains a beautiful and functional piece of clinical history.
Origins of the Crossed Cylinder
Stokes appears to have first described the cross cylinder concept in 1849. Edward Jackson later popularized and refined its clinical use. His name became permanently attached to the instrument as a result. The Jackson crossed cylinder became a standard tool in every refraction kit worldwide.
How It Works
The Jackson crossed cylinder consists of two cylinders of opposite power set at 90 degrees to each other. One cylinder has plus power and the other has minus power of equal magnitude. The examiner flips the lens rapidly between two positions while the patient compares the clarity of vision. This tells the examiner whether to adjust the cylinder axis or power of the prescription.
This model is ±0.25/−0.25 diopters — the most commonly used strength for fine tuning astigmatic corrections.
Construction and Design
The lens is mounted on a knurled handle for easy rotation during the flipping maneuver. The frame is stainless steel. The powers and axes are etched directly into the glass and colored red and white for instant identification in the exam room. Red indicates the minus cylinder axis. White indicates the plus cylinder axis.
This example is unsigned and has no maker’s mark. It represents the standard clinical crossed cylinder of the late 20th century — simple, precise, and purpose-built.
Collectibility
Jackson’s crossed cylinder appeals to collectors of antique optometric instruments and anyone with an interest in the history of refraction. This is a clean, well-preserved example of a tool that shaped how millions of prescriptions were written.
