Table 1.

Photoreceptor density (cells/ mm²) in human macula [3, 30]

ETDRS subfields (inner to outer radius in mm and degrees of visual angle)	Mean cells/ mm2 in subfield		Ratio of Rods to Cones
	Cones/ mm2	Rods/ mm2	Rods : Cones
	Ages 27-37 years
Center (0 - 0.5 mm; 0 - 1.7°)	57,001	20,013	0.35
Inner (0.5 - 1.5 mm; 1.7 - 5.2°)	18,774	78,252	4.17
Outer (1.5 - 3.0 mm; 5.2 - 10.4°)	10,138	130,750	12.90
Mean photoreceptor density in ETDRS grid	13,354	116,037	8.69
	Age 61-90 years
Center (0 - 0.5 mm; 0 - 1.7°)	54,897	15,016	0.27
Inner (0.5 - 1.5 mm; 1.7 - 5.2°)	17,673	56,105	3.17
Outer (1.5 - 3.0 mm; 5.2 - 10.4°)	9,512	96,265	10.12
Mean photoreceptor density in ETDRS grid	12,582	85,106	6.76
RMDA test spot locations	Ages 27-37 years
5° superior	15,530	82,357	5.30
12° superior	9,406	145,683	15.49
	Ages 61-82 years
5° superior	15,376	62,043	4.04
12° superior	8,835	116,683	13.21

1 mm = 3.5° visual angle

The ETDRS grid is 28.27 mm² in area and contains 377,530 cones and 3,280,371 rods in retinas of donors aged 27-37 and 355,678 cones and 2,405,952 rods in retinas from donors aged 61-90. Densities at specific locations were determined by finely space resample of the original data

ETDRS Early Treatment of Diabetic Retinopathy Study, RMDA Rod-mediated dark adaptation