Important daily visual tasks such as reading rely on good optics and a densely packed cone mosaic in the foveal center, as well as signals from cones and associated neural circuitry in the parafoveal region [1
]. Curcio and associates [2
] were the first to publish histological data on between- and within-individual variability in cone density from the foveal center to the midperiphery of the human retina. Cone density peaked in an area as large as 0.032 deg2
with a large between-individual variability ranging from 98,200 to 324,100 cones/mm2
. The large variability near the foveal center disappeared at about 1° in their seven individuals. Curcio and Sloan [3
] followed up with an analysis of cone mosaic regularity in one individual, revealing greater variation in the regularity of the cone mosaic in the foveal center than in the parafovea. Several laboratories where the cone mosaic has been imaged in vivo
with different adaptive optics (AO) retinal imaging systems have reported cone density measures [1
] and cone mosaic regularity calculations [8
] near the foveal center that are mostly in keeping with Curcio and associates. Cone density or photoreceptor mosaic regularity has been shown to be reduced in some genetic disorders that cause red-green [9
] and tritan color-vision deficiencies [13
], but this reduction is not always significant because parafoveal cone density may vary more in a larger population than what is evident from Curcio’s data.
To be able to make appropriate inference at a cellular level of the retina with regards to changes that may be pathological it is necessary to increase the knowledge about variation in the normal population. Here we report the first set of cone density measures from a Scandinavian population of ten normal trichromats imaged in vivo with the Kongsberg adaptive optics ophthalmoscope (KAO). The results reveal statistically significant between-individual variation in parafoveal cone density and cone mosaic regularity.