Ophthalmoscopy (from Ancient Greek ὀφθαλμός (ophthalmós), meaning "eye", and σκοπέω (skopéō), meaning "to look"), also called funduscopy<!-- Do not change spelling before reading section #Etymology and pronunciation -->, is a test that allows a health professional to see inside the fundus of the eye and other structures using an ophthalmoscope (or funduscope). It is done as part of an eye examination and may be done as part of a routine physical examination. It is crucial in determining the health of the retina, optic disc, and vitreous humor.

The pupil is a hole through which the eye's interior can be viewed. For better viewing, the pupil can be opened wider (dilated; mydriasis) before ophthalmoscopy using medicated eye drops (dilated fundus examination). However, undilated examination is more convenient (albeit not as comprehensive), and is the most common type in primary care.

An alternative or complement to ophthalmoscopy is to perform a fundus photography, where the image can be analysed later by a professional.

Types

thumb|Ophthalmoscope (left) and [[otoscope combination by Welch Allyn]]

There are two major types of ophthalmoscopy:

  • direct ophthalmoscopy, which produces an upright (unreversed) image of approximately 15× magnification
  • indirect ophthalmoscopy, which produces an inverted (reversed) image of 2–5× magnification

{| class="wikitable" border="1"

! Features

! Direct ophthalmoscopy

! Indirect ophthalmoscopy

|-

| Condensing lens

| Not required

| Required

|-

| Examination distance

| As close to patient's eye as possible

| At an arm's length

|-

| Image

| Virtual, erect

| Real, inverted

|-

| Illumination

| Not as bright; not useful in hazy media

| Bright; useful for hazy media

|-

| Area of field in focus

| About 2–8 disc diameters

| About 8 disc diameters

|-

| Stereopsis

| Absent

| Present

|-

| Accessible fundus view

| Slightly beyond equator

| Up to ora serrata, i.e. peripheral retina

|-

| Examination through hazy media

| Difficult to impossible

| Possible

|}

<!-- * Slit-lamp ophthalmoscopy -->

Each type of ophthalmoscopy has a special type of ophthalmoscope:

  • Direct ophthalmoscopy uses the direct ophthalmoscope, an instrument the size of a small flashlight with several lenses that can magnify up to about 15 times. This type of ophthalmoscope is most commonly used during a routine physical examination. The pan-ophthalmoscope has a larger primary lens with a variable focusing, allowing for a wider field-of-view.
  • Indirect ophthalmoscopy uses the indirect ophthalmoscope, an instrument that has a light attached to a headband, in addition to a small handheld lens. It provides a wider view of the inside of the eye. Furthermore, it allows a better view of the fundus of the eye, even if the lens is clouded by cataracts.

Observing the eye's interior required alignment of the observer's vision and the light source. This was discovered by William Cumming, a young ophthalmologist at the Royal London Ophthalmic Hospital, who wrote that "every eye could be made luminous if the axis from a source of illumination directed towards a person's eye and the line of vision of the observer were coincident". To eliminate this variable, some (including Lionel Beale) created ophthalmoscopes with an attached light source.

While training in France, Greek ophthalmologist Andreas Anagnostakis came up with the idea of making the instrument hand-held by adding a concave mirror. Austin Barnett created a model for Anagnostakis, which he used in his practice and subsequently presented at the first Ophthalmological Conference in Brussels in 1857, which made the instrument very popular among ophthalmologists.

The invention of the incandescent light bulb further enabled the ophthalmoscope to be self-luminous instead of relying on an external and remote source of illumination. The first ophthalmoscope to have an installed light bulb was created by William Dennet, who presented his invention to the American Ophthalmological Society in 1885, though it was unreliable as the light bulb's life was short and unpredictable. In the 2000s, the company developed a new design of ophthalmoscope called the "Panoptic". The instrument produced an image with a field-of-view five times larger than conventional direct ophthalmoscopes.

Etymology and pronunciation

The word ophthalmoscopy () uses combining forms of ophthalmo- + -scopy, yielding "viewing the eye". The word funduscopy () derives from fundus + -scopy, yielding "viewing the far inside". The idea that fundus can and should correspond to a combining form fundo- drives the formation of an alternate form, fundoscopy (fundo- + -scopy), which is the subject of a descriptive-versus-prescriptive difference in acceptance. Some dictionaries enter the fundo- form as a second-listed variant, but others do not enter it at all, and one prescribes its avoidance with a usage note.

See also

  • Charles Schepens
  • Retinoscope
  • Scanning laser ophthalmoscopy

References

  • Ophthalmoscopy on Medlineplus
  • Ophthalmoscopy on WebMD
  • Overview at bmjjournals.com
  • Medlineplus about different types of ophthalmoscopy