Using Ophthalmoscopes in Eye Examinations

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The Eye

A- Macula
B- Vitreous Humor
C- Sclera
D- Choroid
E - Retina
F - Ora Serrata
G- Canal of Schlemm
H- Anterior Chamber
I - Iris
J - Cornea
K - Ciliary Body
L - Zonule (Suspensory Ligament)
M- Conjuctiva
N - Lens
O - Hyaloid Canal
P - Central Retinal Vein
Q - Optic Nerve
R - Central Retinal Artery

Transparency of the cornea, lens and vitreous humor permits the practitioner to directly view arteries, veins, the optic nerve and the retina.

Direct observation of the structures of the fundus through an effective ophthalmoscope may show disease of the eye itself or may reveal abnormalities indicative of disease elsewhere in the body. Among the most important of these are vascular changes due to diabetes or hypertension and swelling of the optic nerve head due to papilledema or optic neuritis. In this sense, the eye serves as a window through which many valuable clinical evaluations may be made.

When a preliminary diagnosis of an imminently dangerous eye condition, such as acute glaucoma or retinal detachment, is made by the examiner, prompt referral to an ophthalmologist may prevent irreversible damage. Or, when distressing but less urgent conditions, such as visual impairment due to cataract or vitreous floaters are recognized, the patient can be reassured and referred.

Ophthalmoscopes, with their bright, white illumination coupled with patented optical systems, allow the examiner to clearly see these important structures of the eye to aid in making the correct diagnosis.

Little has been written giving the practitioner detailed instructions on the use of the ophthalmoscope. Because the examination can give so much information about a patient’s well being, correct use of the ophthalmoscope makes it one of the most valuable tools available for diagnostic use. The following contains information on ophthalmoscopes, how to conduct an ophthalmic exam, and what to look for while examining the eye.

How to Conduct an Ophthalmic Examination

In order to conduct a successful examination of the fundus, the examining room should be either semidarkened or completely darkened. It is preferable to dilate the pupil when there is no pathologic contraindication, but much information can be obtained through the undilated pupil.

The following steps will help the practitioner obtain satisfactory results:

1. For examination of the right eye, sit or stand at the patient’s right side.

2. Start with the smallest aperture

3. Take the ophthalmoscope in the right hand and hold it vertically in front of your own right eye with the light beam directed toward the patient and place your right index finger on the edge of the lens dial so that you will be able to change lenses easily if necessary

4. Dim room lights. Instruct the patient to look straight ahead at a distant object.

5. Position the ophthalmoscope about 6 inches (15 cm) in front and slightly to the right (25º) of the patient and direct the light beam into the pupil. A red “reflex” should appear as you look through the pupil.

6. Rest your left hand on the patient’s forehead and hold the upper lid of the eye near the eyelashes with the thumb. While the patient is fixating on the specified object, keep the “reflex” in view and slowly move toward the patient. The optic disc should come into view when you are about 1 to 2 inches (3-5 cm) from the patient. If it is not focused clearly, rotate lenses with your index finger until the optic disc is as clearly visible as possible. The hyperopic, or far-sighted, eye requires more “plus” (green numbers) lenses for clear focus of the fundus; the myopic, or nearsighted, eye requires “minus” (red numbers) lenses for clear focus.

7. Now examine the disc for clarity of outline, color, elevation and condition of the vessels. Follow each vessel as far to the periphery as you can. To locate the macula, focus on the disc, then move the light approximately 2 disc diameters temporally. You may also have the patient look at the light of the ophthalmoscope, which will automatically place the macula in full view. Look for abnormalities in the macula area. A red-free filter facilitates viewing of the center of the macula.

8. To examine the extreme periphery, instruct the patient to:

Look up for examination of the superior retina
Look down for examination of the inferior retina
Look temporally for examination of the temporal retina
Look nasally for examination of the nasal retina.

This routine will reveal almost any abnormality that occurs in the fundus.

9. To examine the left eye, repeat the procedure outlined above but hold the ophthalmoscope in your left hand, stand at the patient’s left side and use your left eye.

Overcoming Corneal Reflection

One of the most troublesome barriers to a good view of the retina is the light reflected back into the examiner’s eye from the patient’s cornea—a condition known as corneal reflection. There are three ways to minimize this nuisance:

The Coaxial ophthalmoscope features a crossed linear polarizing filter that may be used. The filter reduces corneal reflection by 99%. It is recommended that the polarizing filter be used when corneal reflection is present.
Use the small aperture. However, this reduces the area of the retina illuminated.
Direct the light beam toward the edge of the pupil rather than directly through its center. This technique can be perfected with practice.

Use of Fixation Target

Direct the patient to focus on the center of the fixation target projected within the light beam. Simultaneously check the location of the pattern on the fundus. If the center of the pattern does not coincide with the macula, eccentric fixation is indicated. In this procedure, the crossed linear polarizing filter is especially useful since it dramatically reduces reflections caused by the direct corneal light path.

Apertures & Filters

Micro - allows quick entry into small, undilated pupils.
Small - provides excellent view of fundus through an undilated pupil.
Large - general examination of the eye through dilated pupil.
Fixation - graduated cross-hairs for measuring eccentric fixation or locating lesions.
Slit - used to determine levels of lesions and tumors.
Cobalt blue - used with flourescein dye to view small lesions, abrasions and foreign objects on the cornea.
Red-Free filter - filters out red light for easy identification of veins, arteries and nerve fibers.
Polarising filter - virtually eliminates corneal reflection.

Common Pathologies of the Eye

Normal Fundus

Disc: Outline clear; central physiological cup is pale
Retina: Normal red/orange color, macula is dark; avascular area temporally
Vessels: Arterial/venous ratio 2 to 3; the arteries appear a bright red, the veins a slightly purplish colour

Central Retinal Vein Occlusion

Disc: Virtually obscured by edema and hemorrhages
Retina: Extensive blot retinal hemorrhages in all quadrants to periphery
Vessels: Dilated tortuous veins; vessels partially obscured by hemorrhages

Hypertensive Retinopathy

Disc: Outline clear
Retina: Exudates and flame hemorrhages
Vessels: Attenuated arterial reflex

Inferior Branch Retinal Artery Occlusion Due to Embolus

Disc: Prominent embolus at retinal artery bifurcation
Retina: Inferior retina shows pale, milky edema; superior retina is normal
Vessels: Inferior arteriole tree greatly attenuated and irregular; superior vessel is normal

Hypertensive Retinopathy (Advanced Malignant)

Disc: Elevated, edematous disc; blurred disc margins
Retina: Prominent flame hemorrhages surrounding vessels near disc border
Vessels: Attenuated retinal arterioles

Nonproliferative Diabetic Retinopathy

Disc: Normal
Retina: Numerous scattered exudates and hemorrhages
Vessels: Mild dilation of retinal veins

Proliferative Diabetic Retinopathy

Disc: Net of new vessels growing on disc surface
Retina: Numerous hemorrhages, new vessels at superior disc margin
Vessels: Dilated retinal veins

Macular Drusen (Colloid Bodies)

Disc: Normal
Retina: Extensive white drusen of the retina
Vessels: Normal

End Stage Diabetic Retinopathy

Disc: Partially obscured by fibrovascular proliferatione
Retina: Obscured by proliferating tissue; small area of retina with hemorrhage seen through “window” of fibrovascular membrane
Vessels: Abnormal new vessels in fibrous tissue
Vitreous: Prominent fibrovascular tissue

Inactive Chorioretinitis (Toxoplasmas)

Disc: Normal
Retina: Well-circumscribed lesion with areas of hyperpigmentation and atrophy of retina, white sclera showing through
Vessels: Normal

Advanced Hemorrhagic Macular Degeneration

Disc: Normal
Retina: Large macular scar with drusen; prominent macular hemorrhage
Vessels: Normal

Advanced Retinitis Pigmentosa

Disc: Normal
Retina: Scattered retinal pigmentation in classic bone spicule pattern
Vessels: Greatly attenuated

Retinal Detachment

Disc: Normal
Retina: Gray elevation in temporal area with folds in detached section
Vessels: Tortuous and elevated over detached retina

Optic Neuritis

Disc: Elevated with blurred margins
Retina: Mild peripapillary edema
Vessels: Mild dilation of vessels on disc

Benign Choroidal Nevus

Disc: Normal
Retina: Slate gray, flat lesion under retina; several drusen overlying nevus
Vessels: Normal

Optic Atrophy

Disc: Margins sharp and clear; pale white colour
Retina: Normal
Vessels: Arteries attenuated; veins normal

Papilledema

Disc: Elevated, edematous disc; blurred disc margins; vessels engorged
Retina: Flame retinal hemorrhage close to disc
Vessels: Engorged tortuous veins