Overview
ISO 8980-2:2017 - "Ophthalmic optics - Uncut finished spectacle lenses - Part 2: Specifications for power‑variation lenses" specifies requirements and verification methods for the optical and geometrical properties of uncut finished power‑variation spectacle lenses. The standard sets measurement conditions (reference temperature 23 °C ± 5 °C), test instruments (focimeter conforming to ISO 8598‑1) and reference wavelengths (ISO 7944) to ensure consistent quality and interchangeability of lenses used in eyeglasses.
Key topics and technical requirements
- Scope and classification: Applies to uncut finished lenses classified as single‑vision, multifocal, or power‑variation lenses.
- Optical tolerances: Defined tolerances for back vertex power, cylindrical power, and direction of cylinder axis (axis tolerances vary with cylinder magnitude; e.g., ±14° down to ±2° for higher cylinder values).
- Variation/addition power: Tolerances for variation (including addition) power are specified (for example, ±0.12 D for ≤4.00 D and ±0.18 D for >4.00 D).
- Prismatic power and base setting: Total prism (ordered + thickness reduction) tolerances are given using formulae based on the higher absolute principal power S (e.g., horizontal tolerance examples include ±[0.25 + 0.1×S] Δ).
- Size and thickness: Definitions and limits for nominal, effective, and usable sizes; effective size tolerance typically d_n − 1 mm ≤ d_e ≤ d_n + 2 mm; thickness verified at prism reference point with ±0.3 mm tolerance from specified value.
- Polarizing lenses: Transmission plane alignment requirement for sun‑glare polarizers (90° ± 3° to permanent alignment marking).
- Verification methods and marking: Detailed verification methods (Clauses 6.x) instruct on lens positioning (back surface against focimeter support), centering at reference points, prism component measurement, and both permanent and optional non‑permanent marking requirements.
Practical applications and users
Who uses ISO 8980-2:2017:
- Spectacle lens manufacturers - set production tolerances and quality control criteria for uncut finished power‑variation lenses.
- Optical laboratories and dispensers - acceptance testing and verification before edging and mounting.
- Purchasing/specification teams - incorporate standardized tolerances into orders and contracts.
- Regulators and conformity assessors - evaluate compliance with international ophthalmic optics requirements.
Practical benefits include improved interchangeability, predictable optical performance, and clear criteria for acceptance/rejection of lens batches.
Related standards
Relevant references and complementary standards include:
Keywords: ISO 8980-2:2017, ophthalmic optics, uncut finished spectacle lenses, power‑variation lenses, focimeter, back vertex power, prism tolerance, cylinder axis, addition power.
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