DIRECT OPHTHALMOSCOPIC EXAMINATION

Why is it important ?

Hermann von HelmholtzIn 1850, invented the ophthalmoscope . Hermann constructed a crude instrument made of cardboard, glue and glass plates from a microscope.

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The modern ophthalmoscope:

Here light source from the batteries is reflected at 90o using a mirror placed in the head portion at 45o angle. The examiner looks through a hole in the mirror that is through the light.

The modern ophthalmoscope:

The modern ophthalmoscope is compact,efficient as well as durable. It consists of a body and head. The body lodges the batteries and a rheostat for adjusting the intensity of light.

The head of the ophthalmoscope:

The head consists of a window for viewing the retina, and one for viewing the lens numbers and a wheel for changing them. Lens numbers are marked in black (positive) & red (negative)

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The structure of the head piece:

The head portion contains a series of lenses ranging from 1 to 30 diopter which can be selected by turning a side wheel & the red or black coded diopter can be read out through a window

-2 diopter10 diopter 7 diopter14 diopter 0 diopter

Choosing the appropriate lens:The structures closer to the ophthalmoscope are best seen using positive lenses, which are labeled with black letters. The retina comes into focus at

the 0 diopter, the cup at 2 red.

procedureIdeally should be examined in a dark room.Ask the patient to fix stare at an object.Turn on scope and set dial at 0.Right with rightBegin at arms length,should see red reflex.Move close until optic disc is visible.Turn dial until disc is in focus - +/-

Examination- what to observe

Media-opacityOptic disc – size,shape,margins,colour,cup-

disc ratioMacula – haemorrhage.,edema,hard exudatesRetinal blood vessels-

narrowing,tortuosity,sheathing,vascular pulsation

General background- hamorrhage,exudates,pigmentary changes,vascularisation

The Normal Retina:

Fundus examination reveals the optic disc in the center and the physiological cup inside it. The vessels are seen emerging from the cup region and diverging out of the disc peripherally

Schematic view of the retina:The retina as seen by ophthalmoscope can have the optic disc, the macula and the fovea. The retinal vessels are seen emerging from the optic disc, the arteries and the veins.

The optic disc and the optic cup:

These are seen, a little to the temporal side of the center of the visible retina. The disc has clear margins and a pink color which is lighter than the surrounding retina, the cup is paler.

The fovea centralis:

It is the slightly more pink area seen about two disc spaces temporal to the disc margin. This is the area which comes into focus when vision is focused and it contains only the cones.

Why is the normal optic nerve pink?

Axons surrounded by glial columnscarry blood vessels -> red

Nerve fibers are translucentLight rays are carried like fiberoptics

rays that escape assume the pink color of the surrounding columns

Quigley and Anderson , Am J Ophthalmol 83:709-717, 1977a

PAPILLOEDEMA-pathophysiologyRaised ICP pressure on optic nerves

impaired axoplasmic flow axonal edema

impaired venous return from retina

engorged capillary and retinal veins-

splinter and flame shaped h’ge CWS-

elevation of disc.

Other causes of disc edemaOptic neuritisAIONCRVOCompression of optic nerve in the orbitLHONDiabetic papillopathyOptic nerve infiltration.

PseudopapilloedemaDisc colour is normalRetinal blood vessel obscured.Venous pulsations presentDisc has a lumpy app.Blurring of margins irregular.Seen in optic nerve drusen/myelinated nerve

fibre

Psudopapilledema True Papilledema

Disc vessels obscured Disc margin vessels clear

Elevation of peripapillary NFL

Elevation confined to the disc

Small cupless disc Loss of cup late

Anamolous disc vessels (tri-, quadrifurcation)

Normal vessels

No hemorrhage or exudates NFL hemorrhage, cotton wool spots, exudate

Pathology of PallorPink Nerve -> Axonal damage -> Pallor

Axons dieRemaining astrocytes are opaqueRearrange at right angles to entering

lightSurround blood vesselsReflect light

OPTIC ATROPHYPRIMARY

Appears denovo or after toxic,metabolic,nutritional,compressive or glaucomatous insult

Chalky whiteEdges are sharply

outlinedRecession of discRetinal vessels

normal

SECONDARYDestruction of

ganglion cells secondary to deg. Or inflamm. lesions of choroid or retina.

Yellow waxyNot sharpVessels attenuatedChoriortinitis,RP