Opthalmoscopy (PDF DOCUMENT)

What are the two main types of ophthalmoscopy?

Direct ophthalmoscopy and indirect ophthalmoscopy

What does a direct ophthalmoscope consist of?

An illumination path (light projection onto the fundus) and a viewing path (for reflected light).

What is the main use of direct ophthalmoscopy?

To examine all ocular structures—especially the fundus—by changing the focus

What is the corneal reflex and how can it affect the exam?

It’s a reflection from the corneal surface that can obscure the view of the fundus.

How can you reduce corneal reflex?

Lower illumination, use smaller apertures, or tilt the ophthalmoscope slightly

What are the common apertures on a direct ophthalmoscope and their uses?

• Large (~7 mm): For dilated pupils

• Medium (~4 mm): For undilated pupils

  • Small (1–2 mm): For macular viewing

What are the main filters used in direct ophthalmoscopy?

• Red-free filter: Enhances contrast of blood vessels

• Slit aperture: Evaluates lesion elevation

• Graticule: Estimates lesion size and fixation

• Crossed polarizers: Reduce glare/reflection

How is magnification in direct ophthalmoscopy calculated?

m=4K′​, where K′K'K′ is the vergence of light exiting the eye (about 15× for an emmetropic eye).

How does refractive error affect magnification?

• Myopia: Increases magnification, smaller field of view

• Hyperopia: Decreases magnification, larger field of view

What are the main advantages of direct ophthalmoscopy?

• High magnification

• Upright, real image

• Portable and handheld

• No mydriasis required

What are the main disadvantages?

• Restricted field of view

• Corneal reflex interference

• Difficult in high myopia

What determines the field of view in BIO?

The diameter of the condensing lens and the patient’s pupil size (≥5 mm).

What type of image is produced in BIO?

A real, inverted, and laterally reversed image.

What happens to field of view when magnification decreases?

Field of view increases

What are the main advantages of BIO?

• Large field of view (~50°)

• Eliminates corneal reflex

• Stereoscopic (3D) image

• Good peripheral fundus view

What are the main disadvantages of BIO?

• Lower magnification

• Image inversion

• Requires mydriasis

• Requires more practice

What are the main components of a traditional fundus camera?

• Illumination system (alignment + flash bulbs)

• Fenestrated mirror for beam separation

• Ophthalmoscope lens and imaging lens

What two major innovations led to modern non-mydriatic fundus cameras?

1. Infrared alignment light (doesn’t constrict pupils)

2. CCD sensors for high-resolution digital imaging

What are the advantages of modern fundus photography?

• Non-mydriatic operation possible

• Digital storage and review

• Improved resolution

• Easier documentation