ANSI Z80.35 pdf free download
ANSI Z80.35 pdf free download.Ophthalmics一 Extended Depth of Focus Intraocular Lenses.
Use ofan optornctcr lens with a 100-millimeter focal length is suggested because then a movement of the target with respect to the optometer of 1 millimeter will change the vergence of light from the target in the focal plane ofthe optometer lens by 0. 1 D. This makes measurements ofvergence entering the model very easy.
The 0 D vergence position ofthe target on the measuring scale is found by viewing the target as light exits the optorncter lens using a telescope set to image objects at an infinite distance. With the focus of the telescope properly set and while viewing the target through it, the target slide is moved until the target is seen at best focus. This slide location on optical rail is then the 0 D position from which all other vergence values are measured.
In a similar way, the axial position ofthe model eye can be adjusted until the front focal plane of the optometer lens is coincident with the corneal vertex ofthe model eye. Using a mirror so that the model eye can be viewed with the telescope through optometer lens, the model eye is moved until dust placed near the cornea! vertex of the model eye is seen in best focus. The corneal vertex then lies in the front focal plane of the optometer lens.
In a Badal optometer system with an optorneter lens having alOO millimeter focal length, the 10-micron pinhole subtends an angle of 0.34 arc minutes. If the effective focal length of a human eye is assumed to 17 mm, a 2-micron diameter macular cone subtends 0.40 arc minutes. Thus, such a 10-micron pinhole can be effectively used to examine the point spread function of the target created by the model eye/IOL optical system.
To select the group and element of the 1951 USAF Resolution Target to use for measurement of EDF IOL and comparison monofocal IOL depth of focus values, in accordance with A.3.4, it is necessary to first convert the published line pair per millimeter values for the various elements of the target to the width of the bars and then to convert these values to subtended angles in the Badal optomctcr system. The width of a bar is equal to one half the period of the bar grating, which in turn, is equal to the reciprocal of the line pairs per millimeter value. The subtended angle of a bar created by the Badal system, given in minutes of arc, equals the arc tangent of the width, divided by the optometer focal length, times 180, divided by pi.
Using these formulas, Element 4 of Group 3 of the 1951 USAF Resolution Target, which has 11.3 line pairs per millimeter, is found to subtend an angle of 1.521 1 arc minutes. Therefore, it represents an acuity value of 20/30.4. This is sufficiently close to 20/32 to use as the test target for depth of focus measurements.
C.4 Microscope/camera system
The task of the microscope/camera system is to capture a digital image formed by the model cye/IOL/target system in the retinal plane of the model eye so that it may be analyzed and thus the image characteristics of the IOL evaluated. The resolution of the microscope/camera system must be such that details that can be perceived by the human visual system can be fully examined. The finest resolution of the human eye is set by the size of its finest receptors — the macular cones. The macular cones are on average 2 microns wide. There are available CCD and CMOS cameras with pixels 5.2 microns wide. For such a detector to resolve details that are several microns in width, those details must be magnified by the system. Choosing a magnification of 10 means that in the retinal image plane the effective size of these camera pixels is 0.52 microns and hence 4 would fit onto a macular cone that is 2 microns in width. This sampling density is sufficient to fully assess resolution issues for a given IOL tested in the model eye.
The following components can be used to create the microscope/camera system fulfilling the above requirements.
1) lOX DIN achromatic microscope objective (Edmund Optics J36-132):
2) DIN objective to camera tube assembly (Edmund Optics J54-868);
3) CCD or CMOS camera (Edmund Optics has an interesting new offering in a compact CMOS camera that is designed to send its bit map images via a USB connection directly to a PC or laptop without the need to have a frame grabber. It is available in either B&W or color. Their EO1312 would be adequate as the pixel size is 5.2 x 5.2 microns).ANSI Z80.35 pdf download.
