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Fundus Photography

Essay by   •  February 19, 2016  •  Course Note  •  1,512 Words (7 Pages)  •  1,144 Views

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Ch.5 Fundus Photography

Purpose

- Fundus (bottom, back, or base of the hollow organ)

- “Ocular fundus”- describes the inside of the eye

- Eye specialist uses ophthalmoscope/slit lamp biomicroscope (with funduscopic lens) to examine the ocular fundus; special camera used when high quality pictures are expected

- Fundus camera is recommended

- Fundus photography: taking pictures with a fundus camera; most basic form of inner eye photography; purely documentary in nature, provides the physician with an objective record of how things look inside the eye the moment the picture is taken

- Fundus photography with color film is preferred when the exact size, shape, or appearance of an intraocular lesion is recorded

- Some inner ocular structures/conditions show enhanced contrast and are better appreciated when photographed with black & white film, using color light, called “monochromatic” illumination

- “Monochromatic” illumination: achieved when a filter of a single (mono) color (chrom) is used to change the light (illumination) shining into the patient’s eye by altering its wavelength.

- Blue and green: colors use commonly selected for monochromatic photography; standard accessories on fundus cameras used for fluorescein angiography.

- Green light: demonstrates retinal vascular changes

- Blue light: provides optimal visualization of vitreoretinal interface abnormalities

- If red filter, choroidal disturbances may occur

Indications

- High quality fundus photographs used for scientific accuracy; generally more superior

Patient Education and Orientation

- Fundus photography: more interesting for the person taking the picture than the patient; photographer can view living tissue in vivo

- Directions for the patient: dilate patient, instruct patient that the right eye will be examined first, take glasses off, put head in face rest, and follow the direction of the light. Colors may appear as well after flash goes off.

- Since the room is dark, lights are bright, and patient is dilated, instruct the patient before touching him/her to hold an eyelid or move head forward

Physician’s Order

- Requisition form: recommended for all types of clinical photography; filled out by the ordering physician

- A form designed just for posterior segment work includes space for diagnosis and description of area of interest, as well as an area to draw any pertinent or unusual findings

Photographic Fields of View

- When looking directly into the patient’s eye through the ocular of a fundus camera, macula will be seen; if patient looks toward their nose, the disc will be seen

- Minimal camera movement when focusing on just the macular and optic nerve

- Seven Standard Photographic Fields

[pic 1]

- Protocol for landmark study on diabetic retinopathy specified 7 overlapping fields to be photographically mapped out for review, evaluation, and classification; incorporated as part of many studies of retinal disease

- The seven standard fields are designed for use with a fundus camera that image 30 degrees of the retina.

- If peripheral fundus photography is of importance, one should know that it’s not always possible to get clear pictures when the camera is positioned at an extreme angle. (this is due to astigmatism, introduced by the angle of the fundus camera in relation to the patient’s crystalline lens)

- Some cameras have a device, astigmatism corrector, to reduce obliquely induced astigmatism, which often improves the view

- Astigmatism corrector also used on patients with refractive astigmatism.

Equipment

- Fundus camera modeled after an indirect ophthalmoscope, although resembles a cannon

- Useful weapon in the fight against visual loss by providing valuable info for the dx/treatment of retinal disease

- Parts of fundus camera: main camera unit, base assembly, and power supply

- Main unit: composted of an optical head, which houses an aspheric front lens and rear objective lens system, a flash bulb and viewing lamp, filters, mirrors, and on some cameras, an eyepiece assembly.

- 35-mm SLR camera body is attached. Its body functions primarily to hold and transport the film since it is used without a lens; does not play a role in image formation

- Main camera: attached to a base that provides for patient positioning and camera movement

- Power supply: incorporated into the camera’s base or stand alone

- Controls for viewing light, fixation light, flash intensity, timer for flurescein angiography located on face of power source

Film

- Daylight color positive transparency (slide) film used in fundus photography (white light of the flash tube is balanced for use with this film)

- Medium speed film (ISO 64-100) is used, but slower film may be used if the flash unit is powerful enough

- B&W fundus photography effective in imaging the choroid, retina, and nerve fiber layer when used with monochromatic illumination

- Use high speed B&W film (ISO 400) if fluorescein angiography is to be performed along with monochromatic fundus photography

- Use slow speed film (ISO 100) if angiography is not being performed

Getting Ready

- Photographer should verify that the fundus camera is in working order before patient enters room (do it behind the scenes, especially if the photographer is not adept at camera maintenance)

- Patient confidence in the photographer’s ability to take a picture my lessen if the photographer fumbles in trying to change a fuse/plug

- If B&W monochromatic photography is being performed instead of color, make sure that the correct filter is in place

- Make sure the mounted camera’s shutter speed is in synch with the flash of the fundus camera, and set the flash intensity to correspond with the speed of the film selected

- Dilated pupils are required; inadequately dilated pupils are a major cause of poor quality fundus photography

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