ISO 15253:2000 pdf download

ISO 15253:2000 pdf download.Ophthalmic optics and instruments —Optical devices for enhancing low vision.
7.4.3 Test procedure
7.4.3.1 For magnifiers and telemicroscopes/near-vision telescopes
After exact alignment of the test set-up, determine the field of view attainable with the respective low vision aid. Here, move the optotype to the frame edge of the low vision aid in order to establish to what extent the optotype is visible. Perform this action horizontally and vertically. The observation telescope may need to be swung into a new position during this process. Determine the horizontal and vertical extents of the field of view by reading the respective measured values off the scale.
Two values are obtained:
Ahor = linear extent of field of view in horizontal direction, measured in millimetres;
Ave = linear extent of field of view in vertical direction, measured in millimetres.
Subsequently repeat the procedure, with the optotype only being moved towards the edge of the low vision aid until one of the directions of the Ronchi ruling cannot be identified. Here once again, the measured values are read off the scale, therefore providing the horizontal and vertical extents of the still-resolvable field of view. The observation telescope shall not be re-focused during this procedure.
The following values are obtained:
Ahor* = linear extent of resolvable field of view in horizontal direction (millimetres);
Ave,.t* linear extent of resolvable field of view in vertical direction (millimetres).
Instead of performing the test in the vertical direction, where the difficulties can be experienced when measuring the extent, it is possible to rotate the low vision aid about 900.
7.4.3.2 For telescopes
After exact alignment of the test set-up, determine the field of view attainable with the respective low vision aid. Here, move the optotype to the frame edge of the low vision aid in order to establish to what extent the optotype is visible. Perform this horizontally and vertically. Determine the horizontal and vertical extent of the field of view by reading the respective measured values off the scale.
Two values are obtained:
Ahor = linear extent of field of view in horizontal direction, measured in millimetres;
Ave = linear extent of field of view in vertical direction, measured in millimetres.
Subsequently repeat this procedure, with the optotype only being moved towards the edge of the low vision aid until one of the directions of the Ronchi ruling cannot be identified. Here once again, the measured values are read off the scale, providing the horizontal and vertical extent of the still-resolvable field of view.
The following values are obtained:
Ahor* = linear extent of resolvable field of view in horizontal direction (millimetres);
Ave* = linear extent of resolvable field of view in vertical direction (millimetres).
Instead of performing the test in the vertical direction where the difficulties can be experienced when measuring tne extent, it is possible to turn the low vision aid about 90°.
7.5 Determination of lateral variation of magnification
The determination of lateral variation of magnification shall be performed under the conditions stated in the manufacturer’s instruction for use. Measuring devices for the determination of lateral variation of magnification shall be used which have, at a confidence level of 95 %, relative uncertainties of less than 0,5 %.
NOTE An example of a test method is given in annex A.
8 Marking and instructions for use
8.1 Marking
Each device shall be clearly marked with at least the following:
a) identification of the device or the manufacturer;
b) manufacturer’s declared value for the equivalent power for magnifiers.
Each device, except those that are custom made, shall additionally clearly be marked with at least the following:
c) manufacturer’s declared value for angular magnification for telescopes;
d) manufacturer’s declared value for either nominal magnification or equivalent power for telemicroscopes/nearvision telescopes.
8.2 Information to be provided by the manufacturer
The manufacturer shall supply with each device at least the following information, in addition to repeating the items of information specified in 8.1:
a) manufacturer’s declared value for the exit image vergence, for stand magnifiers;
b) free working distance, for telemicroscopes;
C) the statement “FIRE RISK — DO NOT LEAVE MAGNIFIER IN DIRECT SUNLIGHT” in upper-case letters, using bold typeface;
d) instructions for the care and cleaning of the device;
e) any characteristic claimed under 5.2.
On request, the manufacturer should make available the following information: the mass of the device, identification of the lens material(s), and the optical dimensions of the magnifier, expressed in millimetres.