Delivery Devices and Accessories 107
Novus Spectra
0642-543-01, Rev A, 12/02
•
Because this condensing lens is the last optical element that the
laser beam passes through, the power and position of this lens will
have an effect on the laser beam in terms of spot size and the focus
of the image of the laser beam on the retina.
•
For most eyes, the image of the retina formed by the hand-held
lens is real, inverted, and located a few centimeters above the hand-
held lens.
The magnification, M, of the two-lens system created by the hand-held lens
and the eye is
where 60 diopter is the refractive power of a “standard” eye. The
magnification of an indirect ophthalmoscoe using a 20-diopter hand-held lens
is 3X, and the magnification of the system when using a 30-diopter lens is 2X.
•
Because the laser beam is a converging beam, the size of the laser
beam in the retinal image plane can be varied by moving the point
of focus of the laser beam out of the laser beam's object plane
(retinal image plane). Figure 2 shows how altering working
distance affects retinal spot size. Note that because the laser beam
divergence angle of small spot sizes is greater than the laser beam
divergence angle of large spot sizes, working distance has a greater
effect on the small spot sizes.
References–Indirect ophthalmoscope
1. Friberg T. Clinical Experience with a Binocular Indirect Retina 7:28-31,
1987.
2. Friberg T. Principles of Photocoagulation Using Binocular Indirect Oph-
thalmoscope Laser Delivery Systems International Ophthalmology Clinics
30(2):89-94, 1990.
3. Friberg T, Eller A. Pneumatic Repair of Primary and Secondary Retinal
Detachments Using a Binocular Indirect Ophthalmoscope Laser Delivery
System Ophthalmology 95:187-193, 1988.
4. Campochario P, Gaskin H, Vinores S. Retinal cryopexy Stimulates Trac-
tion Retinal Detachments in the Presence of an Ocular Wound Archives
of Ophthalmology 105:1567-1570, 1987.
M
60 diopter
power of hand-held lens
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Содержание Novus Spectra
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Страница 6: ...6 Contents Novus Spectra 0642 543 01 Rev A 12 02...
Страница 8: ...Novus Spectra 0642 543 01 Rev A 12 02 8 General Operation...
Страница 40: ...Novus Spectra 0642 543 01 Rev A 12 02 40 General Operation...
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Страница 56: ...Novus Spectra 0642 543 01 Rev A 12 02 56 Safety and Regulatory...
Страница 72: ...Novus Spectra 0642 543 01 Rev A 12 02 72 Indications for Use...
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