Absolute natural lens power (modified Bennett)
Hernandez et al. modification of Bennett’s method — crystalline lens power from cycloplegic refraction, ACD, LT, AL, and mean keratometry. Remaining buffer is judged with an age-adjusted minimum, not a single +16 D cutoff.
Right eye (OD)
Left eye (OS)
Formula: Hernandez VM, et al. Calculation of crystalline lens power using a modification of the Bennett method. Biomed Opt Express. 2015;6(11):4501–4515. Uses thin-lens position b·LT with conjugate-ratio–dependent b (Eqs. 16–18). Posterior corneal radius estimated as 0.81 × anterior if not measured. CCT defaults to 0.55 mm.
Enter ACD from epithelium to anterior lens (usual biometer ACD). Prefer cycloplegic SE. Educational estimate only — theoretical accuracy ≈ ±0.5 D for relaxed eyes (−10 to +10 D).
Age-adjusted buffer minimums: remaining lens reserve is judged against the child’s developmental stage, not a single +16.0 D cutoff.
- Ages 6–9: depleted if ≤ +18.5 D (typical ~+21 to +23 D). A 7-year-old already at +18 D has used reserve early.
- Ages 10–13: depleted if ≤ +17.0 D — buffer nearing exhaustion as the eye matures.
- Ages 14–18: depleted if ≤ +15.5 D — usual biological floor; the lens is not expected to flatten further.