Light can pass through it, if I read the article correctly. What they are doing is creating a new way of customizing the geometry of a lens. Historically:

1. A lens can be concave or convex.

2. Lenses can be made of different transparent materials, which have different densities and therefore different refractive indices.

3. Multiple lenses can be stacked to produce a nearly infinite variety of optical effects, such as magnification, fish-eye, achromatism.

4. Light travels as waves, and when a wave travels from a 'less dense' medium to a 'more dense' medium, part of the wave is transmitted and part is reflected. This is Fresnel reflection. Thin coatings can be applied to lenses reduce to Fresnel reflection. As light travels from air to the coating, some is reflected. As light continues to travel from the coating to the lens, again some is reflected. The two reflected rays interfere destructively and cancel each other out. This is an anti-reflective coating. The same principle can be used to enhance reflectiveness by applying thin coatings with alternating high and low density.

5. Most of the bulk of a lens can be eliminated as long as one surface is etched with ridges having the same focal point. This is a Fresnel Lens. Very large lightweight lenses can be made using this geometry.

All these lenses rely on refraction to focus light though lenses with different materials and geometries. I may be wrong here, but I think the article is describing a new way to engineer the lens, without using traditional methods of changing materials or overall lens geometry. That is, they are incorporating a nanoscale geometry into the material itself, to change its density (and therefore its effective refractive index) without changing any other natural property. By doing so, they have come up with a way of creating an anti-reflective coating with EXACTLY the right refractive index, where before they could only find an approximate match of anti-reflective coating material for a particular lens material.

I think that's what they are doing. But if anti-reflective coatings are already outpriced for amateurs, I doubt this will ever be cheap enough either. We'll have to wait and see.