Small-Aperture Corneal Inlays (Kamra): Pinhole Optics, 1.6 mm Aperture & Monocular Depth of Field Expansion

In paraxial geometric optics, the total linear Depth of Field (DoF in Diopters) for a permissible retinal blur circle diameter $b$ and entrance pupil diameter $D$ is given by:

$$DoF = \frac{2 \cdot b \cdot f'}{D} \implies \text{Halving Pupil Diameter } D \implies \mathbf{\text{Doubles Total Depth of Field}}$$

For a natural $4.0\ \text{mm}$ pupil, human depth of field is $\sim \pm 0.40\ \text{D}$ (Total: $0.80\ \text{D}$). By inserting an opaque mask with a $1.6\ \text{mm}$ central aperture, effective entrance pupil diameter drops to $1.6\ \text{mm}$, expanding total depth of field to over $\mathbf{+2.50\text{ to } +3.00\ \text{Diopters}}$—allowing presbyopes to read at $33\ \text{cm}$ effortlessly.

A solid plastic ring placed inside the cornea would block glucose and oxygen diffusion from aqueous humor to anterior epithelium, causing epithelial ulceration. The Kamra inlay ($3.8\ \text{mm}$ outer diameter, $1.6\ \text{mm}$ inner aperture, $5\ \mu\text{m}$ thickness) incorporates 8,400 randomized laser micro-perforations ($5\text{ to } 11\ \mu\text{m}$ diameter), preserving $100\%$ of natural nutrient flow.

According to the Troland equation, pupil constriction from $4\ \text{mm}$ to $1.6\ \text{mm}$ cuts light throughput to the retina by: $\left(\frac{1.6}{4.0}\right)^2 = \mathbf{16\%\text{ Light Transmission}}$ ($84\%$ reduction!). Consequently, small-aperture inlays are implanted strictly monocularly in the non-dominant eye. The dominant fellow eye maintains full light intake for night driving.