DIT: Photography of the anterior and posterior segment

Ocular photohraphy

External ocular photogtraphy

anterior segment photography

- slit lamp

- gonio

- specular micropscopy

fundus photography

Ocular photography leverage the

advantage of time

Eye

1:1

both eyes

1:4

full face

1:10

pay attention to purkinje images!

Purpose of photography

documentation

- simple external

documentation of function

specific ocular lesions

diagnostic/effectiveness of treatment

Anterior Segment - Slit lamp biomicropscope photography/video

diffuse illumination

widest slit w/longest aperture

used to view overall areas

not focused beam

direct illumination

optic section

parallel piped

wide beam (tangential illumination)

Increasing the width we must

decrease illumination

indirect illumination

transparent tissues including the cornea

Specular illumination

smooth surfaces

sclerotic scatter

cornea ONLY

retroillumination

direct or indirect

lens

iris

cornea

external illumination sources

often mounted on SL

Gonioscopy photopgraphy

can use diffuse

can use slit beam to fidn corneal wedge

Fundus photography

a two dimensional image of a three dimensional retina

tissue captured using reflected ligth

Fundus photography tyes

- film-based system or digital

- contrast and non contrast modalities

- colored filters ( with out without contrast) : split image

- fundus cameras are described by the angle of view - the optical angle of acceptance of the lens

the optical angle of acceptance of the lens

15-200 degress

big picture --> increase angle

details --> decrease angle

fundus photography - CONTRAST

Non-contrast

- red/free photography

- Color fundus photography

- confocal scanning laser opthalmoscopy (cSLO)

- Fundus autoflorescence (FAF)

- infrared reflectance

- Hyperspectral retinal imaginf

- Adaptive SLO

Contrast

Flourescein angiography (FFA)

Indocyanine green angiography (ICGA)

Fundus - ANGLE OF VIEW

Traditional cameras/ standard imaging

provide an angle of 30 degrees - 45

30 degrees creates a film image

2.5 times larger than life

Wide angle fundus camera (WF)

captures images between >= 60 to 100 degrees

Ultra-Widefield (UWF)

>= 100 - 14-/220 c montage

less reintal maginfication

Narrow angle fundus camera

20 degrees of less

Photgraphic standards

- Basic field of posterior pole 30 degree camera, fovea centered, ONH at edge

- Diabertic retinopathy study used 7 standard overlapping fields

Monochromatic Fundus photography

using a specific wavelength to image the eye

Monochromatic Fundus photography: 2 basic principles

1. use of contrast filters to alter subject tones in black and white

2. the increased scatter of light and shorter wavelengths

490 nm

blue-green

540-570 nm

yellow green

615 nm

orange

Fluorescein exciter filter

490nm

red, green and blue filters each transmit

1/3 of white light

Wavelengths - Blue light

shorter (more scatter)

- sees transparent more easily

- RNFL

- ILM

- retinal folds

- cysts

- epiretinal membranes

Wavelengths- Green light

Red free

540-570nm

absorbed by blood by reflected more than blue light by retinal pigmentation

less scatter

excellent contrast - best!

baseline prior to FFA

Wavelengths- Green light enhances view of

hemorrhages

drusen

exudates

Wavelengths - red light

Retinal pigmentation appears lighter and more transparaent

choroidal pattern more visible

peak 620-640nm

fundus contrast is reduced

retinal vessels are lighter

ONH light

Wavelengths - red light useful for

pigmentary disturbances

choroidal ruptures

choroidal nevi

choroidal melanomas

see table

splitting/separating out from a colored image results in

some loss of resolution

Fundus Artifcats

- orange crescent: camera misaligned

- blue peripheral haze - camera too far away

- bright blue-white central reflection: camera too close

- pale vertical tan streaks: kashes

- spots or streaks regardless of pt position: clean lens

- orange of red image with not detail : blink

Scanning laser ophthalmoscope

Can be used for several retinal imaging modailities (FA, ICG, FAF)

not capable of full color images of the retina (Psuedocolor)

monochromatic laser illumination combined with confocal optical system produce high contrast finley detailed iamges

nondilated pupil !

Spectralis multicolor mode

uses

blue reflectance

green reflectance

infrared reflectamce

Advantages of cSLO

improved image qualityu

suprresion of scattered light

pt comfort

3-D imaging and video

Effective imaging of patients who do ont dialte well

REVIEW IMAGE QAULITY AND FUNCTINO OF EPICAM

Multimodal imaging

the approach to diagnose a single retinal disease by combining differnt imaging modalities