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1 Fundus photography

a. Choosing a Fundus Camera b. Technique of Fundus Photography

c. Field of view in fundus Photography

d. Artifacts in fundus photography

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a. Choosing a Fundus Camera

Ziess FF450 PLUS IR Visupac fundus camera

Choosing a fundus camera Routine fundus photography & angiography: Mydriatic fundus camera. Screening of diseases like Diabetic retinopathy: Nonmydriatic fundus camera. Wide angle fundus photography: Retcam II fundus camera useful in management of diseases like Retinopathy of Prematurity, Retinoblastoma.

Retcam II wide angle fundus camera

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a. Choosing a Fundus Camera

Digital fundus photography Vs Film based photography

• Less expensive, • Acceptable resolution, • Easy image manipulation and image transfer • Faster image processing and duplication.

Heidelberg Retina Angiograph 2

Advantages of Heidelberg Retina Angiograph 2

• Confocal Scanning Laser ophthalmoscope • Digital • High resolution • High sensitive • High contrast • Dynamic, simultaneous fluorescein and indocyanine green angiography system

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b. Technique of Fundus Photography

Getting started

• Check the eyepiece correction at the beginning of photography.

• One should see sharp cross hair–reticule

through eyepiece.

Doughnut effect • Look for doughnut effect of sharp

image of camera light on the patients closed eyelid and on the cornea.

Focusing • It’s important to remember that

focusing is not achieved by movement of joystick, but by adjusting the focus knob.

• After obtaining the focus once, one need not refocus the image for the same patient during the photography.

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b. Technique of Fundus Photography Stereo fundus photography

Manual lateral movement of the camera can be used to obtain the required, non-simultaneous stereo pairs.

Stereoscopic pair of photographs of macula help in assessing the retinal thickening in macular edema due to three dimensional effect

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b. Technique of Fundus Photography Stereo fundus photography

A 5X magnification stereo viewer is required to assess the stereoscopic fundus photos

Allen1 technique of Stereo fundus photography

• An Allen stereo separator or manual lateral movement of the camera can be used.

• First member of the pair photograph is taken as far to one side of the

pupil maintaining good illumination and clear image. Then second member of the pair photograph is taken from the other side of pupil.

• 2mm is the minimum separation between the two photographs of the pair

to achieve the stereoscopic effect.

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b. Technique of Fundus Photography Sequence of Montage fundus photography

Posterior pole of fundus: Primary gaze: Superior field of fundus: Gaze direction (at 12 o clock meridian):

Superiotemporal field of fundus Gaze direction (1.30 oclock meridian)

Temporal field of fundus Gaze direction (3 oclock meridian)

Montage fundus photography

• Montage fundus photography is useful in documentation of a widespread lesion such as a tumor or vascular anomalies.

• 9 photographs of each eye to be taken

• Photo of each field of eye is captured in a clockwise direction

• Fundus camera has an inbuilt software application to create montage at the

end.

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b. Technique of Fundus Photography Sequence of Montage fundus photography

Infero temporal field of fundus Gaze direction (4.30oclock meridian)

Inferior field of fundus Gaze direction (6oclock meridian)

Inferonasal field of fundus Gaze direction (7.30oclock meridian)

Nasal field of fundus (9oclock meridian)

Superonasal field of fundus (11oclock meridian)

Montage fundus photo of the left eye depicting clearly hemorrhages scattered in all quadrants of fundus

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c. Field of view

20º field of view 30º field of view

50º field of view

• The field of view and magnification of image are inversely proportional

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d. Artifacts in retinal imaging

Right fundus shows blue center and white reflection (arrow-left) peripherally

Left fundus shows peripheral white crescent (arrow-left)

• Blue central reflection can occur when camera is close to the eye / in eyes with poor pupillary dilatation.

• White / orange crescent at the periphery of image is due to camera misalignment; hence the camera is moved in the opposite direction.

Right fundus shows blurring of image inferiorly with white streaks (arrow) - caused by eyelashes coming in the way of photography due to continuous blinking

Right fundus shows blooming effect of a lesion due to increased intensity of camera flash. This artifact can result in wrong diagnosis of leakage.

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d. Artifacts in retinal imaging

The above artifact is called double exposure (Combination of present image with preexisting image) due to improper functioning of memory device in the fundus camera.

• When the photographer tries to focus a myopic fundus the central coating of objective lens can result an image of dark spot (arrow) and may some times block the macular defects.

• This artifact should be kept in mind while taking photographs of highly myopic eye.

• Directing the patient to look temporally or superiorly so that the central part of the

macula can be captured, can potentially avoid this problem

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d. Artifacts in retinal imaging

Note typical double image artifact seen in gas filled eyes

Note multiple shiny reflexes (arrows) seen in silicone oil filled eyes

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Suggested Reading

1. Allen L. Ocular fundus photography. Am J Ophthalmol.1964; 57:13-28. 2. C. Delori, C.K. Dorey, G. Staurenghi et al, In vivo fluorescence of the ocular fundus

exhibits retinal pigment epithelium lipofuscin characteristics. Invest Ophthalmol Vis Sci. 1995; 36:718–29.

3. Ferwerda JG: The World of 3-D: A Practical Guide to Stereo Photography. Nederlandse Vereniging voor Stereofotografie. (1982).

4. Lawrence A. Yannuzzi, Michael D. Ober, Jason S.Ophthalmic fundus imaging: today and beyond.American Journal of Ophthalmology.2004; 137(3): 511-24.

5. R.H. Webb, G.W. Hughes and F.C. Delori, Confocal scanning laser ophthalmoscope. Applied Optics. 1987: 26:1492–99.

6. R.B. Rosen, A.G. Podoleanu, S. Dunne and P. Garcia, Optical Coherence Tomography Ophthalmoscopy. In: T.A. Ciulla, C.D. Regillo and A. Harris, Editors, Retina and optic nerve imaging, Williams and Wilkins, Lippincott (2003).

7. S.Shikano and K. Shimuzu, Atlas of fluorescence fundus angiography. B. Saunders Company, Philadelphia (1968).

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Self-test 1. The resolution of digital fundus photography is

a. 1000 lines b. 10,000 lines c. 100,000 lines d. 100 lines

2. The resolution of film based fundus photography is a. 1000 lines b. 10,000 lines c. 100,000 lines d. 100 lines 3. The advantages of digital fundus photography in comparison to film based are all except a. Less expensive b. Faster image processing and duplication time c. Possible Irregular lesion size measurement d. Useful patient educational tool e. Better image resolution and stereo viewing 4. Fundus auto fluorescence is a property of stimulated emission of light from a. Melanin b. Lipofuscin c. Xanthophyll d. Beta carotene

Answers: 1.a, 2.b, 3.e, 4.b