Disease as setpoint drift: the quadratic basin-collapse law

Disease on this substrate is a defended setpoint, clock, or instrument failing. A loop-gain drop d shrinks the attractor barrier as (g²/4)(1−d)², a quadratic basin collapse, raising the Kramers crossing rate. Glaucoma, AMD, myopia, presbycusis, cataract, diabetic retinopathy, and BPPV each instantiate one failure mode. Shapes are consistency (code) outputs (relative rates depend on the noise scale D); absolute rates are open.

A single derived law governs the major non-rare diseases of the sense organs: residual barrier = (g²/4)(1−d)² under a loop-gain drop d, so the barrier collapses quadratically (1.00 → 0.25 at d=0.5 → 0.01 at d=0.9) while the relative Kramers crossing rate rises monotonically (its values depend on the chosen noise scale D; the code uses D_ref = 0.25·B0). Presbycusis is the special case of the Hopf amplifier pushed off criticality, collapsing the F^(1/3) gain. Shapes are consistency (code); per-disease anchors are cited [L]; absolute incidence is [O] (needs the noise scale).

Disease here is not a separate machinery from health — it is the same R19 substrate failing in one of a few shapes: a defended setpoint drifts, a feedback loop loses gain, an attractor is crossed, or a physical instrument breaks. This is the same substrate as carcinogenesis, viewed through the sense organs.

Why the attractor barrier collapses quadratically

A loop-gain drop d leaves an effective gain g(1−d) and a residual attractor barrier (g²/4)(1−d)²; the escape rate follows Kramers' exp(−B/D). Because the barrier depends on the square of (1−d), a partial loss of feedback shrinks the protective barrier faster than linearly, so risk accelerates as control degrades. The relative crossing-rate column below (2.14×–52.46×) depends on the chosen noise scale D (the code uses D_ref = 0.25·B0, so rate_rel = exp(4·(1−(1−d)²))), not only the absolute rate; only the barrier-fraction column (1−d)² is D-free.

Quadratic basin collapse (PAX6 node, loop-gain drop d)
loop-gain drop d	barrier fraction	relative crossing rate (D_ref = 0.25·B0)
0	1.0000	1.00×
0.1	0.8100	2.14×
0.25	0.5625	5.75×
0.5	0.2500	20.09×
0.75	0.0625	42.52×
0.9	0.0100	52.46×

Seven major diseases, one substrate

Each major non-rare disease of the eye and ear maps to a single failure mode of this law, with its anchor cited and its absolute rate left open:

Major eye/ear diseases as substrate failures
disease	loop / arm	mechanism	grade
glaucoma	IOP homeostasis / outflow	trabecular-meshwork stiffening → IOP setpoint drifts up → retinal ganglion-cell death (attractor crossing)	interpretation/[L]
myopia	emmetropization / defocus	growth-control loop fails → axial elongation → myopia via the classical 2.69 D/mm	interpretation/[L]
presbycusis / NIHL	cochlear amplifier / Hopf µ	hair-cell + prestin loss pushes µ off criticality → the F^(1/3) gain collapses → threshold shift	interpretation/[L]
cataract	lens solubility / chaperone	oxidative damage → crystallins cross the aggregation spinodal → insoluble scatter (near-irreversible)	interpretation/[L]
AMD (geographic atrophy)	complement regulation	lost regulation raises the inflammatory loop gain → chronic activation → RPE/photoreceptor atrophy	interpretation/[L]
diabetic retinopathy	retinal microvasculature	chronic hyperglycemia → ischemia → VEGF-driven neovascular attractor (seam to metabolism)	interpretation/[L]
BPPV / vertigo	instrument fault	otoconia dislodge into a canal → false angular-velocity signal	interpretation/[L]

Shapes reproduced (code), absolute rates open [O]. The law reproduces the shapes (quadratic barrier collapse, monotone crossing-rate rise, amplifier-gain collapse) as consistency (code); the relative-rate values depend on D; the absolute incidence and timing need an external noise scale D and absolute basin depth, stated as the obstacle in IRREPRODUCIBILITY_LEDGER.md. Rare and monogenic forms are owned by the disease whitepaper and enter here only as cited parameters — a deliberate division of labour, not a gap.