Posterior Eye

1. light is focused by series of condenser lenses onto prism system

2. light illuminates retina and returns reflected light

3. examiner oberves reflected light from ret thru sight hole

• direct view of REAL and ERECT image

• excellent mag (x15)

• allows for gross examinationof external eye

• no set px posture required

• portable

• no power supply required so ideal for domiciliary

• need to be able to use both eyes and both hands

• requires very close WD= px/examiner unconfortable/ anxious

• FOV limited = 8’

  • high mopics have reduced FOV so ask px to keep Rx = increased WD and reflections ( consider indirect)

• instrument mag not variable

  • hyperope= minified image= may miss suble ret changes

• Mono view only = no stereopsis= cant determine disc cupping or ret odemema

• Poor view if media opacities present

• young children - cant sit still

• px with mobility issues/ domiciliary

• high mag helpful to view:

  • subtle changes in ret vasculature

  • calibre of arterial light reflex

  • diabetic ret ( fine dot haemorrhages)

bino:

• slit lamp binocular indirect opthalmoscopy (VOLK)

• head mounted binocular indirect

mono:

• Welch- Allyn Panoptic

• Keeler wide angle twin mag

• uses high +VE condensing lens - makes the yey highly myopic

• emergent rays produce REAL& AERIAL & INVERTED & LATERATALLY INVERSED image

• binocular stereoscopic view - see OD margin, macula oedema, rasied ret lesions

• increased FOV

• less WD = less intrusive

• SL mag can vary

• use in conjuction with SL filters (red free)

• incorporate into SL routine

• view is independent of px Rx

• incorporate SL photography

• image is upside down and lateraly inverted so flip record/mentally invert

• not portable (dom)

• challenging with samll pupils

• young pxs limitations- chin cant it on chinrest/not tall enough

• px comfort - bright light/neck issues/ wheelchair px

• mono indirect, but image is erect

• suitable for amblyopic examiners bz mono + longer WD

• can examine R&L with same eye

• 25’ FOV

• greater WD

• “glare extinguishment system” prevents unwanted glare and reflections

• portable

• high 2D imaging

• allows for permanent didgital record of retina

• quick and easy to perform

• FOV is good ( 40 - 50’)

• automated func eg. autofocus, autoalighment, autocapture. allows for delegation

  ***DISAD- limited by patient pupil size

200 degree panoramic image of ret

2 diff wavelengths of light:

• green layer = anterior retina

• red layer= posterior/ choroidal

increases in glaucoma

decreases in papilloedema

Head-mounted Binocular Indirect Opthalmoscopy

• light from internal light source is directed into px eye

• +ve lens held near to px eye

• biconvex, aspheric condensing lens

• light reflected off retina= real + laterally inverted image

• Gullsrand reflex free system i.e illumination and emerging light paths are seperate (slit lamp and opthalmoscope)

Ads:

• wide FOV

• high quality stereoscopic image

• portable

• comfotable distance for px

• better fundus view through media opacities

Disads:

• requires mydriasis

• image is inverted = complicates recording of abnormalities

• high level of illuminance= uncomfortable for px

• px should ideally be supine ( can be done with wheelchair px sitting)