Optoref Contact lens & ophthalmic drop reference

Contact lens specs

Filter on the left, or search a base curve, diameter, brand, polymer or problem. Free, no account.

 
 

Vertex distance

Power at the corneal plane. Matters from about ±4.00 D.

Cylinder transposition

Plus-cyl to minus-cyl and back. Spherical equivalent shown too.

Toric axis (LARS)

Left Add, Right Subtract. Enter which way the lens marking has rotated, as you look at the patient.

GP lens power (SAM / FAP)

Steeper Add Minus, Flatter Add Plus. Enter the diagnostic lens, its over-refraction, and the base curve you want to order (all in dioptres; use the K converter for mm).

Keratometry (mm ⇄ D)

Keratometric index 1.3375 (D = 337.5 ÷ mm). Enter two K readings for corneal astigmatism.

Reading add estimate

Accommodative demand minus half the (Hofstetter) amplitude held in reserve. A starting point. Refine with NRA/PRA balance.

Prentice's rule

Prism (Δ) = decentration (cm) × power (D). Fill any two fields; the third is calculated.

Vertical imbalance at near

Differential vertical prism in down-gaze. Enter the power in the vertical (90°) meridian of each eye; minus for myopes.

Visual acuity converter

Enter Snellen (foot) or logMAR; the rest are derived.

AC/A ratio

Eso phorias positive, exo negative. Calculated method needs distance & near phoria; gradient method needs a lens.

Predicted residual astigmatism (GP)

Refractive cylinder minus corneal (keratometric) cylinder, both in minus-cyl form with roughly aligned axes.

Eye-drop days of supply

Rough estimate for prior authorisations. Assumes ~20 drops/mL and no waste.

These calculators are provided to speed routine work and may contain errors. Confirm every result clinically before acting on it.

The options

Effect sizes are trial results over 2-3 years, not individual guarantees, and vary with age, baseline progression and compliance. Axial length is the outcome that matters for long-term ocular health.

Low-dose atropine

~30-70% ↓ progression

Antimuscarinic drop at night. Slows axial elongation by a receptor-mediated scleral/retinal effect, largely independent of accommodation.

Concentrations
0.01%, 0.025%, 0.05% (compounded in the US)
Best candidate
Age ~4-12 at onset, documented progression; usable alongside optical methods
Evidence
LAMP: dose-dependent, 0.05% best efficacy-to-tolerability. US CHAMP trial did not show a benefit for 0.01% on its primary endpoint.
Watch-outs
Dose-dependent photophobia and near blur; rebound spurt on abrupt cessation (worse at higher strengths); confirm concentration and beyond-use date each refill

Orthokeratology

~30-50% ↓ axial

Reverse-geometry rigid lens worn overnight; reshapes the central cornea for spectacle-free daytime vision and creates peripheral myopic defocus.

Range
~ −1.00 to −4.00 D, up to −1.50 D cyl (more with toric designs)
Best candidate
Motivated child/family, good hygiene, wants daytime spectacle independence; regular cornea
Evidence
Multiple RCTs / meta-analyses; ~0.25-0.30 mm less elongation over 2 years. CooperVision Abiliti Overnight carries an FDA myopia indication.
Watch-outs
Microbial keratitis risk (hygiene, no tap water, peroxide care); regression if wear stops; morning topography needed to confirm centration

Soft multifocal / dual-focus CL

~50% ↓ (MiSight)

Daily-disposable soft lens with concentric treatment zones (dual-focus) or a centre-distance multifocal profile imposing peripheral myopic defocus.

Options
MiSight 1 day (FDA-approved), Abiliti 1 day, NaturalVue MF; off-label centre-distance MF with a +2.00/+2.50 add
Best candidate
Age ~8-12 at fit, wants daytime CL wear, adequate for daily handling and hygiene
Evidence
MiSight 3-yr: 59% less refractive / 52% less axial progression. BLINK (NEI): +2.50 add ≈ 0.23 mm less elongation over 3 yrs; +1.50 add ineffective.
Watch-outs
Some haze/ghosting at distance with higher adds; standard soft-lens infection risk; benefit may wane if discontinued

Myopia-control spectacles

~50-60% ↓ axial

Lenses with peripheral defocus segments (DIMS) or aspheric lenslets (HALT), or diffusion optics (DOT) that lower peripheral contrast.

Products
Hoya MiYOSMART (DIMS), Essilor Stellest (HALT), SightGlass DOT
Best candidate
Younger children, contact-lens-averse families, or as an adjunct; needs consistent full-time wear (≥ 12 h/day)
Evidence
DIMS ~52% and HALT ~55% less axial elongation over 2 years with full-time wear; DOT ~0.4 D over 3 yrs (CYPRESS)
Watch-outs
Not FDA-approved in the US as of 2026, available in Canada, the EU and Asia. Efficacy drops sharply with part-time wear.

Combination therapy

Additive in RCTs

Optical treatment plus low-dose atropine for children who keep progressing on monotherapy, or who start young / progress fast.

Common pairings
Ortho-K + 0.01-0.025% atropine; soft multifocal + atropine
Best candidate
Fast progressor (> 0.75 D/yr or > 0.3 mm/yr), very young onset, or inadequate response after 6-12 months of monotherapy
Evidence
Several RCTs show an additive effect, most pronounced in younger and faster-progressing children
Watch-outs
Combined side-effect and cost burden; escalate deliberately, one change at a time

Lifestyle & what to avoid

Adjunct

Environmental measures support any active treatment and are the first advice for pre-myopes.

Encourage
≥ 90-120 min/day outdoors; working distance > 30 cm; regular near-work breaks (20-20-20)
Evidence
Outdoor time strongly reduces incidence; effect on progression in already-myopic children is modest
Avoid
Under-correction / deliberate blur, it accelerates progression. Fully correct myopic children. Single-vision lenses are not myopia control.

Clinical framework

Who to treat

  • Active management, progressing myopia in a child, typically onset age 6-12, with ≥ 0.50 D/yr or ≥ 0.2 mm/yr axial growth.
  • Higher urgency, younger age at onset, faster progression, high myopia in a parent, East-Asian ancestry.
  • Pre-myopia, cycloplegic SER between +0.75 and −0.50 D with risk factors: start outdoor-time counselling; 0.05% atropine is used prophylactically in some guidelines.

Baseline workup

  • Cycloplegic autorefraction (cyclopentolate 1%).
  • Axial length by optical biometry, the primary tracking metric.
  • Corneal topography (candidacy for ortho-K / soft CL) and horizontal visible iris diameter.
  • Binocular vision assessment (near phoria, AC/A, accommodative function).
  • Dilated fundus exam + baseline imaging; family and lifestyle history.

Monitoring & targets

  • Review every 6 months: cycloplegic refraction + axial length, plotted against normative growth percentiles.
  • Goal: bring the axial-growth rate toward the age-expected (emmetrope) rate.
  • Re-check lens fit / ocular surface at every visit; repeat topography for CL wearers.

Escalating & stopping

  • Escalate, continued progression after 6-12 months → add a second modality (usually atropine to an optical treatment).
  • Continue, until stabilisation, commonly mid-to-late teens (~age 15-16).
  • Stop, two stable visits with < 0.25 D/yr and minimal axial change; taper atropine rather than stopping abruptly to limit rebound.

Axial length reference

Axial lengthInterpretation
~23.5-24.5 mmTypical adult emmetrope
> 26 mmHigh myopia, elevated lifetime risk of myopic maculopathy, retinal detachment, glaucoma, early cataract
> 28 mmPathologic-myopia range, markedly higher risk of vision-threatening complications

≈ 0.35-0.40 mm of axial length per dioptre of myopia. There is no known "safe" amount of myopia, risk rises continuously with axial length, which is why slowing elongation, not just correcting blur, is the goal.

A teaching and planning aid compiled from published trials and consensus guidance (IMI, WSPOS). Figures are approximate and evolving, verify against current literature and product labelling, and individualise every plan.

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