Direct ophthalmoscope with large diameter beam and a magazine of interchangeable lenses.
Ideal equipment
A range of beam types including a small diameter beam, a slit-beam, a graticule for mapping retinal lesions, red-free light for retinal blood vessels and cobalt blue light for fluorescein.
With the room darkened, set ophthalmoscope to 0 and look into eye from arm's length.
Visualise tapetal reflex, any opacity in path of reflex appears black or casts shadows.
Mydriatics are not usually required for this step.
Compare pupil size between eyes (before mydriatics).
As examiner moves opacity moves, direction of movement helps to localize lesion:
Opacities anterior to plane of pupil appear to move in opposite direction.
Opacities in plane of pupil appear to remain stationary.
Opacities behind plane of pupil appear to move in same direction as examiner.
Core Procedure
Step 1 - Close direct ophthalmoscopy
Mydriatics should now be employed and 20 min allowed for their effect.
Use your right eye to evaluate dog's right eye, start at level of end of nose and obtain a tapetal reflex, keeping this in view, move closer to see fundus.
Closer to the eye, larger the field of view.
Ophthalmoscope setting is +2 to -2 for most dogs.
Examine optic disk .
Systematically examine fundus, angle of view will need to be changed to see periphery, always keep light beam through pupil .
This can be difficult as patient's eye will move during examination. Normality is variable and considerable practice needed to distinguish abnormalities.
Focus back through eye using progressively more positive dioptre settings.
+8 posterior lens.
+10 lens nucleus.
+12 anterior lens.
Increasing positive for structures anterior to lens.
Repeat the procedure using your left eye to examine dog's left eye.
Gelatt K N (1999) Ocular Examination and Diagnostic Techniques. In: Veterinary Ophthalmology.3rd edn. Lippincott, Williams & Wilkins, Philadelphia.
Severin G A (1996) Examination of the Eye. In: Severin's Veterinary Ophthalmology Notes.3rd edn.
Mould J R B (1993) Approach to an Ophthalmic Examination. In: Petersen-Jones and Crispin (eds) Manual of Small Animal Ophthalmology. Cheltenham: BSAVA. pp 17-18.
Bistner S I (1971) Examination of the eye.Vet Clin North AmVolume 1 (Jan 1971). pp 29-52.
Gelatt K N (1970) Examination of the eye.Scientific Presentations and Seminar Synopses37th AAHA meeting. pp 326-333.
Vetstream contributor(s)
Dr Ralph Hamor DVM MS DipACVO , College of Veterinary Medicine, Department of Veterinary Clinical Sciences, 1008 West Hazelwood Drive, Urbana, IL 61801, USA.
Normality is variable and considerable practice needed to distinguish abnormalities.