Visionstar JS-232B1

It halves the smallest change the practitioner can offer. At the end of a subjective refraction, during binocular balancing or when setting a near addition, a ±0.12 D lens lets the practitioner test whether a patient prefers a result between two quarter-dioptre steps. Patients with sharp discrimination, such as those with demanding visual tasks, can sometimes express that preference reliably. The final prescription is still usually written in 0.25 D steps, so the 0.12 D lens more often decides which way to round than sets a new value.

Less precise than 0.12 D for most patients. A study by Bullimore and colleagues reported 95% limits of agreement of ±0.75 D for repeated refraction. Reviews by Goss and Grosvenor found roughly 80% agreement within ±0.25 D and 95% within ±0.50 D for sphere and cylinder power. Rosenfield and Chiu reported tighter limits among vision professionals, around ±0.27 D for sphere and ±0.16 D for cylinder. The 0.12 D lenses are most useful with patients at the discriminating end of that range.

A single Maddox rod measures horizontal and vertical heterophoria, and a red rod is often preferred because its streak is easy to distinguish from the fixation light. A red and white pair is the traditional arrangement for the double Maddox rod test of torsion. Published work on patients with superior oblique paresis found that mixed red and white rods can shift the perceived torsion toward the eye behind the red rod, and that same-colour rods avoid the artefact. Practitioners can swap the rods between eyes on a repeat measurement to check for that effect.

In both signs, the spheres omit 4.25, 4.75, 5.25, 5.75, 8.50 and 9.50 D, and above 8.00 D they run in whole-dioptre steps to 16.00 D. The cylinders omit 3.25, 3.75, 4.50 and 5.50 D. There is no 7.00 prism. A missing power can be built by stacking two lenses, which adds surfaces and, at high powers, alters effective power. The gaps sit away from the fine end of the range, where the 0.12 D lenses are.

The datasheet states 232 pieces, and the itemised table totals 234: 140 spheres, 68 cylinders, 12 prisms and 14 accessories. The concave sphere columns also show a quantity of 2 against three rows with no power listed, which looks like a layout artefact. Ask the seller for the packing list and count the tray against it on delivery.

The datasheet does not say. It describes the rings as chromium-plated metal and gives the aperture, and nothing else about construction or marking. Ask the seller how powers are marked on each lens, whether prism bases and cylinder axes are marked on the optic or the ring, and how the optic is held. Check each cylinder on a focimeter at delivery, since a 0.12 D cylinder is only as useful as the accuracy of its axis mark.

None are published on the datasheet. Ask the seller for tray and case dimensions and the shipped weight at quotation.

The 36.5 mm figure is the clear aperture. Ring outer diameter and thickness are not published, and both decide whether a lens seats firmly in a frame cell. Ask for both figures before order and check them against a cell in the frame you use. BS EN ISO 12867 is the trial frame standard applied in the UK and Europe.

BS EN ISO 9801:2009 is the reference standard for full and reduced aperture trial case lenses, confirmed by ISO in 2024, and it sets power tolerances that matter when lenses as weak as 0.12 D are supplied. The datasheet claims no conformity, so ask for test evidence. Under UK MDR 2002 the set is typically Class I, or higher, use-dependent, confirmed against the declaration of conformity at order. The declaration is issued by the manufacturer and provided by the seller. Conformity requirements differ by destination market, and the seller confirms what applies where the unit is going.

In the UK, testing of sight is restricted under the Opticians Act 1989. The General Optical Council reserves refraction within the sight test to registered optometrists and registered medical practitioners, with student optometrists refracting under supervision. Other countries set their own rules, and the buyer's professional regulator is the reference point.

The set has no electrical parts, so it sits outside electrical safety and portable appliance testing, and in a UK workplace PUWER 1998 applies as it does to any work equipment. The practical tasks are focimeter checks, which matter most for the weakest lenses, and replacing lenses that are lost or damaged. Disinfectant compatibility for the optics and chromium plating is not published. Ask the seller for cleaning instructions and single-lens replacement pricing.

A clinic refracting many patients with cylinders between 3.00 and 4.00 D will miss the 3.25 and 3.75 D cylinders. A buyer who needs published dimensions, weight or a stated marking method will find none on the datasheet. A practice that prefers same-colour Maddox rods for torsion testing will find one red and one white rod here.