TF-C OPHTHALMIC TRIAL FRAME
Multi-layered slots allow for the insertion of up to 5 trial lenses on each side.
Clear scales on the trial frame facilitate easy observation.
Adjustable length, angle, and shape of the legs.
Adjustable height of the nose pads.
Convenient adjustment of the astigmatism axis.
Made from high-quality materials to prevent deformation.
The ophthalmic trial frame is an essential tool for optometrists and ophthalmologists during eye examinations. The TF-C ophthalmic trial frame is a high-quality and adjustable instrument suitable for a wide range of patients, from children to adults.
Use a low vision chart
Don't use a projector chart. Because low vision patients also have reduced contrast sensitivity, a projector chart doesn't provide enough contrast to properly test these patients' vision. A low vision chart, however, is designed purposely in high contrast for this reason.
Place direct illumination evenly on the chart
Do this to further increase contrast while decreasing the chance of glare. Enable each patient to choose his optimal contrast, glare control and overall testing conditions via a brightness control gooseneck exam light.
Cater the room illumination for each patient
This also optimizes testing conditions. For example, a patient who has albinism may find better testing conditions with dim light, whereas a retinitis pigmentosa patient may prefer brighter room illumination. Many times, however, choice of illumination may not correlate to the characteristics of the ocular disease. Therefore, as is the case with direct illumination selection, allow the patient to assist in choosing the room illumination.
Perform the trial frame refraction at 10 feet
Place the low vision chart at 10 feet instead of at the standard 20 feet used for projection charts. The magnification produced by this closer testing distance increases the likelihood the patient will more easily discern differences in the lenses presented during subjective refraction.
What factors should I pay attention to when using the Ophthalmic Trial Frame?
Use the just-noticeable difference formula
Thankfully, this formula is helpful in determining the most effective increments of lenses to use for each patient's trial frame refraction. To determine the just-noticeable difference (i.e. the smallest diopter of lens change the patient's vision can appreciate), take the denominator of the visual acuity found at 10 feet during low vision acuity testing on a high contrast low vision chart, and divide it by 100. For example, a patient who sees 10/100 has a just-noticeable difference of +/− 1.00. (100 divided by 100 is 1.00) In this example, you would present +/−1.00 lenses when testing for sphere power. The same rationale holds true for choosing which power of hand-held cross cylinder to use when testing for cylinder power.
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Specifications:
1.PD adjustment range:
Binocular pupil distance: 48 - 80 mm
Left or right pupil distance: 24 - 40 mm each
Minimum scale value: 1 mm
2.Axis scale:
Left scale: 120° to 0° to 135°
Right scale: 45° to 180° to 60°
Axis scale increases counterclockwise along the frame's axis, with markings every 5°.
3.Diameter of Lenses: Φ 38mm.
4. Slot: 3 front slots and 2 back slots
5. Axis: 360 °
6. Nose pad:
Adjustable height: 0 to 14 mm
Adjustable angle: 0° to 30°
7. Adjustable length range of the left and right frame leg: 115~150 mm.
8. Weight: approximately 60g
