Fundus camera Lecture 12
Fundus camera
The fundus camera or retinal camera is an instrument used for fundus
photography, it is a specialized low-power microscope with an attached camera
designed to photograph the interior surface of the eye, Fundus photography
captures the images of the retina, monitors the progression of retinal diseases
such as diabetic retinopathy and used also in fundus fluorescein angiography
(inject fluorescein dye intravenously and take fundus camera to study the retinal
blood vessels). Fundus photography impacts the detection and screening of
various causes of treatable and preventable blindness, Over the decades, the
quality of fundus images and the ease of photography has improved
significantly.
Part of fundus camera
A fundus camera is a complex system with multiple lenses and a camera. The
parts of a typical fundus camera are shown in the figure below
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Fundus camera Lecture 12
مطلوبات
Optics of Fundus Camera
Light from the viewing lamp is projected onto a round mirror (round mirror-1)
and then through a set of filters (filters) onto another round mirror ( round mirror
-2). The light is reflected from the mirror (round mirror-2) to a series of lenses
(series of lenses).
Due to the presence of a mask in the uppermost lens (uppermost lens), the light
is finally focused as a donut-shaped beam. This donut-shaped light beam falls
on another round mirror with a central aperture (round mirror-3 with a central
aperture), and the reflection exits the camera system through the objective lens
and enters through the cornea into the eye (donut-shaped light through a dilated
pupil), the photo of which is to be taken.
When both the illuminating rays through the pupillary border and the image at
the center of the pupil are correctly aligned, the imaging rays exit through the
center of the pupil, i.e., the central non-illuminated portion of the donut of the
light (donut-shaped light through a dilated pupil)
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External Fixation LED – ضوء التثبيت الخارجي
2. Objective lens – العدسة الشيئية
3. Forehead rest – مسند الجبهة
4. Canthus marker – مؤشر زاوية العني
5. Chin rest – مسند الذقن
6. Chin rest adjuster – أداة ضبط مسند الذقن
7. Handle – املقبض
8. Chin rest base – قاعدة مسند الذقن
9. Camera – الكاميرا
10. Trigger switch – زر التشغيل
11. Joy Stick – عصا التحكم
12. Camera mount – حامل الكاميرا
13. Base Plate – القاعدة األساسية
14. Wheel cap – غطاء العجلة
15. Power adapter – محول الطاقة
16. USB Cable – كابلUSB
Fundus camera Lecture 12
The imaging rays pass through the central aperture of the mirror as mentioned
above (round mirror-3 with a central aperture), through the astigmatic correction
and diopter compensation lenses (diopter compensation lenses), then back to the
single-lens reflex camera system (camera system).
From the above, it is clear that the patient’s pupil is illuminated with a ring
illumination and then this light illuminates the retina, while the reflected light
from the retina passes through the pupil center where the optical imaging quality
of the eye is highest. Because the light path of the two systems is separated,
there is little reflection in the photographed image.
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Fundus camera Lecture 12
Aperture
Which defines the diameter of the exit pupil of the observation beam path and
thus the optical resolution of the fundus image. Once the image is captured, it is
transferred to a PC to visualize the fundus and check the ocular condition.
Applications (modes of examination)
Fundus camera can perform the following modes of examination:
1. Colour photography, where the retina is
illuminated by white light and examined in full
colour.
2. Red-free photography, where red colour is
filtered from the imaging light by using a green
filter to improve contrast of blood vessels and
hemorrhages
3. Angiography, where a special dye is injected intravenously and the retina
is illuminated with an excitation colour which
fluoresces light of another colour where the dye is
present. A very high contrast image of retinal
vessels is produced by filtering (exclusion) of
excitation colour and passage of fluorescent
colour. Blood flow in retinal blood vessels can be observed by taking
several photos at different time intervals.
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