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Ophthalmoscopy: indirect
Introduction
- To examine the eye especially the posterior segment.
Uses
- Examination of the eye, mainly the lens and posterior segment (vitreous, fundus, optic nerve head).
Advantages
- Enables view of fundus through some degree of ocular opacity or cloudy media, which preclude direct ophthalmoscopy.
- Allows fundus examination through small pupil where mydriasis is undesired or not possible.
- Excellent survey technique allowing large field of view and stereopsis.
- Allows easier examination of peripheral fundus.
- Greater working distance → increased safety for examiner and less restraint of patient.
- Facilitates determination of fundus depressions and elevations due to stereopsis.
- Both hands are on patient's head with binocular indirect technique, so fundus examination is faster and comparison between eyes is easier.
- A supplemental mirror can be attached to many binocular indirect models, permitting simultaneous visualization by examiner, student, colleague or client.
Disadvantages
- Low magnification, depending on the condensing lens used.
- Inverted and reversed, virtual image.
- Equipment is expensive with binocular models but condensing lens with pen torch are inexpensive and can be used instead with some limitations.
Technical problems
- Requires time and patience to master technique.
Alternative techniques
- Direct ophthalmoscopy Ophthalmoloscopy: direct where greater magnification is required.
- The monocular indirect ophthalmoscope (PanOptic from Welch Allyn.) combines advantages of both systems: simplicity of use, production of erect image, medium magnification, but is expensive.
- Pen torch (or transilluminator) plus condensing lens can be used as cheap indirect ophthalmoscope, but more difficult to use and examiner cannot restrain patient's head.
Time required
Preparation
- 20 minutes for mydriatics to work if being used.
Procedure
- 10 minutes should be adequate for detailed examination of both eyes.
Requirements
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Preparation
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Technique
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Aftercare
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
Other sources of information
- Heinrich C (2014) The ocular examination. In: Gould D & McLellan G (eds) BSAVA Manual of Canine and Feline Ophthalmology. 3rd edn. British Small Animal Veterinary Association.
- Featherstone H J & Heinrich C (2013) Ophthalmic examination and diagnostics. In: Gelatt K N (ed) Veterinary Ophthalmology. 5th edn. Wiley-Blackwell. pp 533-613.