Direct ophtalmoscopy

  • Procedure ulitising a direct ophthalmoscope for visualising the ocular media and the fundus
  • Principle
    • Light is reflected into the eye using the direct ophthalmoscope
    • The emergent rays from the fundus of the patient’s eye exit as parallel rays after passing through the lens
    • These rays are brought to focus on the examiners eye with accomodation at rest
    • If the patient and/ or the examiner is ametropic, a correcting lens (equivalent in power to the combined optical defect of the patient’s and examiner’s eyes) from the ophthalmoscope is utilised
    • The fundus image formed is virtual, erect and magnified (about 15x in an emmetropic eye – less in hypermetropes, more in myopes)
  • Procedure
    • Should be done in a semi dark room
    • The left eye of the examiner should be used to examine the left eye of the patient and vice versa
    • The patient is asked to look at a distant object
    • Light is reflected into the patient’s eye and a red reflex is visualised (distant direct ophthalmoscopy)
    • The examiner now comes as close to the patient’s eye as possible (theoretically, the ophthalmoscope should be placed at the anterior focal point of the patient’s eye – 15.4mm in front of it)
    • The fundus and the ocular media is visualised and any defect is looked for systematically

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