## CIEConeFundamentalsFieldSizeTest

##### >Psychtoolbox>PsychTests

CIEConeFundamentalsFieldSizeTest

Look at how the quantities in the CIE standard that depend on field size vary with

field size, particularly for field sizes greater than 10-degrees, which

is the outer limit of what the standard sanctions.

My conclusions are

- that since we know macular pigment is declining towards zero with

field size (see refs below) and the CIE expoential formula has this

property, it is resonable to use the CIE formula for macular pigment

density for field sizes greater than 10-degrees. - the CIE formula for pigment optical density asymptotes to a constant

as one extends past 10-degrees. Whether this is true in the retina or

not, I am not sure. But as field size gets larger, using this formula

is going to be no worse than simply using the 10-degree values, since

they are the same. - one needs to take any estimate of the CMFs for large field sizes

with a grain of salt. There is going to be variation across the field,

so any point estimate is likely to be wrong somewhere. The CIE

formulae, extended using the formulae past their bounds, are a good

first guess for the mean field properties, but being aware that there

is variation within the field, as well as individual variation around

the CIE estimates, is important when considering things like the effect

of inadvertant stimulation of cones when one tries to isolate

melanopsin using silent substitution. Note in particular that the CIE

formula is trying to capture large field color matches where subjects

are instructed to ignore the center of the field as best they can. In

a threshold experiment, this might not be how subjects were instructed

and would in any case be rather hard to do. And if you used annular

stimuli, youâ€™d be a bit off and might want to think about how to

estimate the fundamentals from the annulus. Studying the Moreland and

Alexander paper below in detail might help with thinking on that.

Refs:

Mooreland & Alexander (1997). Effect of macular pigment on color

matching with field sizes in the 1 deg to 10 deg range. Doc. Opth.

Proc. Ser., 59, 363-368.

Moreland and Alexander make color matches for annuli and for

circular fields, and develop a formula for the equivalent macular

pigment density for color matches of various field sizes. In

these matches, observers are instructed to to ignore the central

Maxwell?s spot, I am pretty sure. M&A say the data are consistent

with the idea that obsevers look near the edge of the field but

not quite at it. Their data are for field sizes of 10 degrees,

and the estimates are fit with exponentials. M&A used these data

together with measurements of macular pigment density by Moreland

& Bhatt (1884) to develop an equivalent (for uniform fields)

macular pigment density to be used in predicting color matches

out to 10 degrees. The formula is an exponential decay.

Something like this made it into the CIE standard, although it

may have been tweaked to make sure the color matching data are

consistent with the 10-deg and 2-deg CMFs. I have not thought

hard about the underlying calculations.

Moreland, J.D. and Bhatt, P. (1984). Retinal distribution ofmacular

pigment. In: Verriest, G. (ed.), Colour Vision Deficiencies VII. Doc.

Ophthalmol. Proc. Ser. 39: 127-132. W. Junk, The Hague.

Uses color-matching data for field sizes out to 18 deg (I think)

to develop estimates of macular pigment density as a function of

eccentricity. Key feature of the data is that density estimates

decline according to an exponential and reach zero at

eccentricity (radius) of about 7 degrees. This paper also

reviews earlier estimates and they all look like decaying

exponentials.

Putnam and Bland (2014). Macular pigment optical density spatial

distribution measured in a subject with oculocutaneous albinism.

Journal of Optometry, 7, 241-245.

See ComputeCIEConeFundamentals, CIEConeFundamentalsTest.

5/25/16 dhb Wrote it.

6/1/16 dhb Polished it up a bit, and added to PTB distribution.

`Psychtoolbox/PsychTests/CIEConeFundamentalsFieldSizeTest.m`