Posterior Segment and Fundus Evaluation
Techniques
Dilate when the clinical question requires it, such as diabetes, flashes and floaters, or suspected detachment. Tropicamide 1% with phenylephrine 2.5% is standard; check the angle first if the patient is at risk for closure. Direct ophthalmoscopy gives an upright, highly magnified view but a narrow field. Binocular indirect ophthalmoscopy with a 20 D condensing lens gives a wide field with an inverted and reversed image at roughly 3x magnification; have the patient fixate with the other eye while you sweep the quadrants. Slit-lamp lenses (78 D, 90 D) provide a stereoscopic view of the posterior pole through a small pupil.
What to document
Optic disc margins and color, vertical and horizontal cup-to-disc ratio, neuroretinal rim following the ISNT rule (inferior greater than superior, greater than nasal, greater than temporal), peripapillary atrophy, disc hemorrhages, vessel caliber and arteriovenous crossing changes, macular reflex and foveal center, and the peripheral retina with scleral depression when indicated. Record laterality and whether the examination was dilated.
Worked example
A vertical cup-to-disc ratio of 0.75 with inferior rim thinning and a splinter hemorrhage is a glaucoma-suspicious disc. Document it, correlate with intraocular pressure, pachymetry, and a 24-2 field, and note whether the cupping could be explained by optic atrophy.
Traps
Failing to dilate when indicated, or dilating without warning about 4 to 6 hours of blur and photophobia. Not documenting disc margins. Examining only the posterior pole and missing a peripheral tear. Not checking for a relative afferent pupillary defect before dilation.