The Fundus Mapping

The major landmarks of the fundus:

1.Optic disc

–the point where the optic nerve enters the retina. This is the the blindspot area of your eyes. In the optic disc is a cup which is usually present. The vertical cup disc ratio in a normal person is around 0.3 while pathological changes are suspected in ratios more than 0.4.

the cup is always on the temporal side of the optic disc, while there are crwoding of vessels on the nasal side of the optic disc. This knowledge is used to identify which side is the eye. In the picture above, it is clearly the fundus of a left eye.

2.Macula

–the pigmented area of the retina which is rich in cone photoreceptors and is responsible for clear detailed vision.

3.Fovea

–a small rodless area of the macula that provideds acute vision.

4.Vessel branches

–There are 4 main branches of vessels from the optic disc. Each branches off into different directions, mainly the superonasally, superotemporally, inferonasally, and inferotemporally.

Fundoscopy Steps

Fundoscopy should be done optimally in a dark or dimmed room. Such preference is essential to keep the pupil as dilated as possible. Alternatively, topical drops can be given to dilate the eyes if there is no contraindications.

1.Fundoscopy should be done on the same side for patient and the examiner. This being said, while examining the right eye, hold the fundoscope with your right hand, and examining with your right eye on the right side of the patient.

2.Setting the illuminated lens disc at positive (Green) usually from 4 10, stand from approximately 1 arm’s length from the patient while illuminating the patient’s both eyes using the large aperture. This enable you to examine the red reflex of the patient.

3.Select “0” on the illuminated lens disc and start with the small aperture as you approach the patient while fixing the “red reflex” pupil as your target. Remember to ask the patient to look straight at a distance to maintain pupil dilation.

4.Tilting slightly at 15 25o lateral to the patient, move forward as you direct the light beam into the pupil. The optic disc should be within view as you are about 1 2 inches from the patient’s eye. remember that the optic disc is slightly towards the nasal aspect of the fundus.

5.The optic disc may not be focused as you see it, as hypermetropic patients require more “plus” (green numbers) lenses for clear focus of the fundus while myopia patients require more “minus” (red numbers).

6.Examine the optic disc for:

•color

•contour (margin, shape, elevation, etc)

•cup disc ratio

•caliber of vessels (normal AV ratio around 2:3.

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7.Follow each vessel as far to the periphery as you can and look for any abnormalities such as venous dilatation, AV nipping, etc.

8.To examine the periphery, ask the patient to:

•Look up for examination of the superior retina

•Look down for inferior retina

•Look temporally for temporal retina

•Look nasally for nasal retina.

9.Lastly, locate the macula which is approximately 2 disc diameters temporally, between the superotemporal and inferotemporal vessels. Or you can ask the patient to look at the light of the ophthalmoscope, which would put the macula in good view. Look for abnormalities. Red filter facilitates the view of macula.

10.For the examination of the left eye, the same procedure can be repeated, but with left hand and left eye on the left side.

1. Optic Disc Abnormalities

Disc Swelling

i.Disc swelling is a sign, not a diagnosis.

ii.It is essential to test the optic nerve function in all cases of disc swelling.

iii.Tests for optic nerve function includes:

1.Visual acuity

2.Pupil responsedirect reflex

consensual reflex

relative afferent pupillary defect (RAPD)

3.Visual field

4.Color vision (Red desaturation)

iv.2 important causes of optic disc swelling(Disc edema) are:

•Optic Neuritis

•Papilloedema

*Papilloedema is reserved for bilateral disc swelling as a result of increased intracranial pressure. Thus, any optic disc swelling cannot be described as papilloedema unless the other eye is checked as well.

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v.Papilloedema vs Optic Neuritis

Causes of disc swelling:

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Optic Atrophy (Figure 1.1)

•Findings:

a.Poor visual acuity

b.Positive RAPD

c.Pale optic disc

•Common Causes

a.Hereditary: Autosomal dominant optic atrophy, autosomal recessive optic atrophy, Leber’s hereditary Optic Atrophy

b.Vascular: Central Retinal Artery Occlusion, Antrior ischemic optic atrophy (acute phase)

c.Retinal dystrophy: Cone dystrophy, Retinitis Pigmentosa

d.Nuttritional/Toxic: Vitamin B deficiency

e.Inflammatory: Sarcoidosis, polyarteritis nodosa

f.Demyelination: Multiple Sclerosis

g.Compresive: Optic nerve glioma or meningioma

Figure 1.1 Optic Atrophy

Glaucomatous optic neuropathy (Figure 1.2)

Findings:

a.Increased Cup/Disc ratio (Normal: 0.1 0.3) (Abnormal > 0.4)

b.Nasalization/Bayonetting of vessels in the optic disc

Bayoneting – double angulation of vessels as it “climbs” from the the cup of the optic disc

Nasalization displacement of the vessels from center to the nasal aspect of the cup in the optic disc.

(multiple gray dots scattered on cup of optic disc)

caused by exposure of lamina cribosa due to loss of neuroretinal tissue (seen in advanced glaucomatous stage)

d.Very deep cup

•not all enlarged cup means glaucoma

Figure 1.2 Glaucoma

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Optic Disc Neovascularization (Figure 1.3)

•Disorganized arcades of vessels seen on optic disc

•Can be shaped as fronds, with thin and fragile vessels

•Neovascularization may involve just the peripheral as well, and may assume the shape of a “seafan”

•Common causes of disc neovascularization:

1.Advanced Diabetic Retinopathy

2.Central Retinal Vein Occlusion

3.Ocular Ischemic Syndrome

Figure 1.3 New vessels formation on optic disc

Notice the disorganized tiny vessels on the nasal side of the optic disc, forming a massive frond like stuctures.