Table 1.

Methods used for foveal localization illustrating criteria for foveal localization and advantages and disadvantages of each method.

Method for foveal localization	Criteria used to localize fovea	Advantages	Disadvantages
Ophthalmoscopy/fundus photography	Retinal vasculature	High availability	Flood illumination (low contrast)
	Macular pigment and melanin		High intensity visible light(requiring pupil dilation)
	Relative position to optic disc		Affected by structural variability in normal and retinal disease
	Foveal light reflex		Often requires localization relative to other features
			Low accuracy
Scanning laser ophthalmoscopy	Retinal vasculature	High contrast of retinal features(vasculature and optic disc)	Affected by structural variability in normal and retinal disease
	Macular pigment and melanin	Ability to acquire high-resolution images	Pigment variability in normals and diseased retinas
	Relative position to optic disc	Ability to use specific light sources	Often requires localization relative to other features
	Foveal light reflex easily visible	Stronger foveal light reflex
	Topography measurements (HRT)
	Cone diameter or unresolvable cones (AOSLO)
Fundus reflectometry	Macular pigment reflectance	Uses inherent foveal properties(macular pigment, cone photopigment)	Indicates general region, not fovea per se
	Cone foveal photopigment(unbleached)	Quantifiable criteria	Pigment variability in normals and diseased retinas
	Stiles Crawford effect
	Subject fixation
	Foveal light reflex
	Focal decrease in autofluorescence
Optical coherence tomography	Foveal depression(retinal thickness)	Uses inherent foveal properties(foveal depression)	Foveal depression absent in many retinal diseases/hypoplasia
	Fixation	High accuracy in normal populations	Affected by eccentric or inconsistent fixation for long sampling periods
		High availability
		Quantitative
Fluorescein angiography	Retinal vasculature	High availability	Invasive, potential systemic side effects to dye
	Foveal avascular zone	High contrast of retinal vasculature	Indicates general region based on foveal avascular zone, not fovea per se
	Choroidal fluorescence		Large variability in vascular structures, particularly in diabetes
			Fovea not always centered on foveal avascular zone
			Dark fundi and media opacities reduce contrast
Entoptic methods	Retinal vasculature	Inexpensive	Subjective
	Foveal avascular zone	Non-invasive	Indicates general region based on foveal avascular zone, not fovea per se
			Large variability in foveal avascular zone (larger/altered in retinal disease)
			Fovea not always located at the center of the foveal avascular zone
Fixation stability with fundus imaging	Scanning laser ophthalmoscope and optic disc as landmark	Match structure to subjective function	Subjective
		Estimates variability of fixation	Expensive equipment
		Non-invasive	Limited availability
			Requires patient cooperation
Scanning laser polarimetry	Birefringence	Uses inherent foveal properties(birefringence)	Birefringence disrupted with cone axon atrophy
	Retinal vasculature	Non-invasive	Not widespread availability for analysis of macular data
	Foveal light reflex	Robust