ISO 8598-1:2014

Overview

ISO 8598-1:2014 - "Optics and optical instruments - Focimeters - Part 1: General purpose instruments" - defines requirements and test methods for general-purpose focimeters used in the ophthalmic field. It covers instruments that measure vertex power, cylinder axis, prismatic power and prism base setting within a defined area of a lens (excluding instruments that only measure an entire lens at once). The standard supports conformity assessment of spectacle and contact lens products against international ophthalmic requirements.

Key topics and technical requirements

• Measurement scope
  • Vertex power range: at least −20 D to +20 D
  • Prismatic power: 0 Δ to at least 5 Δ
  • Cylinder axis: 0° to 180°; prism base setting: 0° to 360°
• Instrument types & definitions
  • Manual focusing focimeters (eyepiece or projection screen)
  • Automated focimeters (single-measurement capability)
  • Continuously indicating and digitally rounding focimeters
• Display and resolution
  • Manual (non-digital): dioptric scale interval ≤ 0.25 D with interpolation to ≈0.12 D; axis scale interval ≤ 5° with interpolation to 1°; prism interval ≤ 1 Δ with interpolation to 0.5 Δ
  • Digital: minimum step ≤ 0.06 D (two decimal digits); axis increment 1°; prism step ≤ 0.06 Δ
• Mechanical & optical requirements
  • Lens diameter support: at least 80 mm; thickness: at least 20 mm
  • Translational movement of lens/adjusting rail: ≥ 30 mm; initial offset within 10 mm
  • Lens-support geometry and contact-lens support dimensions specified (manufacturer to state internal diameter)
  • Axis-marker pin-mark recommended diameter: ~0.7 mm
  • Stable operation in normal environment: 23 °C ± 5 °C, relative humidity < 85%
• Metrology & test procedures
  • Clause 6 lists tests: indication error checks, axis-marker alignment, adjusting rail, non‑symmetric errors, repeatability, centration error, tinted-lens capability, and specific procedures for eyepiece focimeters
  • Annexes include guidance on correction values, uncertainty evaluation (Annex B), reference lenses (Annex C) and user information (Annex D)

Practical applications and users

• Intended for the ophthalmic community: spectacle laboratories, optometrists, ophthalmic manufacturers, quality and conformity assessment laboratories, and calibration services.
• Ensures reliable measurement for: spectacle lens verification, frame mounting checks, orientation and marking of uncut lenses, and contact-lens power testing.
• Helps manufacturers and labs demonstrate compliance with international lens specifications and provides standardized test methods for calibration and quality control.

Related standards

• ISO 9342-1 - Test lenses for focimeter calibration (spectacle lenses)
• ISO 8429 - Graduated dial scale (axis direction)
• ISO 7944 - Reference wavelengths
• ISO 18369-3 - Contact lens parameters (support dimensions)

Keywords: ISO 8598-1, focimeters, general purpose focimeters, spectacle lens measurement, vertex power, cylinder axis, prismatic power, ophthalmic optics, focimeter standards.