The Metabolomic Eye image has been featured in the NIH/NEI Audacious Goals Initiative brochure that is being distributed to researchers as well as public and private funding agencies and advocacy groups for an effort to fund vision research and vision rescues to regenerate portions of the retina that are lost in disease. My friend and colleague Wei Li also had his image of ground squirrel retina featured in this same brochure as seen above.

You can download the full resolution brochure in pdf format here.

Congratulations to you and Wei Li for having your images included in the brochure.

The brochure mentioned a postage stamp as something to use to compare to the size of a human retina. I have been thinking about what would compare to both the size and weight of a ruby-throated hummingbird retina. A common 1/4 inch hole punch has a diameter of about 6mm. A circular piece of paper punched out from 20 pound bond printer paper with that type of hole punch is about 2.2 mg in weight and about 0.1mm thick. If a person were to stack two or three of those pieces of paper punched out with a common hole punch I think they would end up with something that could approximate the size and weight of the retina of a hummingbird with a 4 to 4.5mm diameter eye. I am reasonably convinced the retina of a hummingbird with a 4.5mm diameter eye would not weigh more than three circular pieces of 6mm diameter printer paper or about 6.6mg.

In my opinion, using the paper circles punched out with a hole punch would give students and others a better appreciation for the size and weight of the retina of a hummingbird. To me at least, it amazing to realize such a tiny structure is so effective at processing information and producing excellent vision.

These are just my thoughts. I would be happy to correct any of the above figures if you disagree with them. You are much more knowledgeable in these matters than I am.

That could be. If you calculated the total surface area of a sphere, you’d have something like: total surface area in m^2 = (2πr^2) + (πr^2) = 3πr^2. Weight would be that surface area times the mass of the thickness which is probably close to the water weight.

Thanks again for all your help and for the formula. If we start with a hummingbird eye with a 4.5mm outside diameter and assume a scleral thickness of 0.1mm(x2) it would give an inside diameter of 4.3mm. Using an overall average retinal thickness of 0.15mm and plugging into your formula I come up with a retinal weight of about 6.54mg.

As I mentioned on a prior blog post, math was never my favorite subject so I may be misunderstanding your figures. I may also be over estimating the thickness of the sclera or underestimating the thickness of the retina. I would appreciate it if you would let me know what you think of my estimates and calculations.