ISO 18369 Ophthalmological Optics - Contact Lenses

The “ISO 18369 Ophthalmological optics - Contact lenses” standard, developed by the International Organization for Standardization (ISO), consists of the following sub-sections published under the same title:

The standard “ISO 18369-1 Part 1: Glossary, classification system and recommendations for labeling characteristics” describes the applicable terms and definitions relating to the physical, chemical and optical properties, manufacture and use of contact lenses. This standard provides a glossary of terms and, where appropriate, the international symbol and abbreviation associated with a particular term. It also defines terms related to contact lens care products. Furthermore, it includes classifications of contact lens materials and offers recommendations for labeling contact lens properties.

This standard applies to all types of contact lenses that make contact with the front surface of the eye and integrate with the tear film. It does not cover intraocular lenses or other ophthalmic devices.

This basic standard defines fundamental terminology relating to the physical, chemical, and optical properties, manufacturing processes, and uses of contact lenses. It also covers terminology for contact lens care products (e.g., cleaning solutions).

An important feature is the classification system for contact lens materials, which categorizes lenses according to their chemistry and properties. This system ensures compatibility between lenses and care products, preventing issues such as lens damage or reduced comfort. It also provides guidelines for labeling, including what information should be included on the packaging (e.g., base curve, diameter, number, and material type).

The ISO 18369-2 Part 2: Tolerances standard describes the tolerance limits for the basic optical and physical parameters of rigid corneas, rigid sclera, and soft contact lenses at the time of manufacture. These tolerances may not be applicable for other purposes, such as shelf-life studies.

This standard applies to all types of contact lenses that fit onto the front surface of the eye:

Rigid corneal contact lenses
Rigid sclera contact lenses
Soft (hydrophilic) contact lenses

This standard specifies tolerance limits for the essential parameters that must be met when lenses are tested as described. Tolerances are determined at the point of market release (i.e., the finished product ready for distribution or clinical use). This standard does not cover:

Intraocular lenses
Custom-made lenses that go beyond standard parameters (although many tolerances are applied proportionally)
Controls throughout the production process (final product tolerances only)

The acceptable tolerance limit parameters defined by this standard include posterior peak power (prescription power), radius of curvature (base curve), diameter, and center thickness. Lenses must meet these tolerances when tested to ensure they perform as intended. For example, deviations in power or diameter can lead to poor fit, discomfort, or blurred vision.

The standard “ISO 18369-3 Part 3: Measurement methods” includes methods for measuring the physical and optical properties of contact lenses as specified in the ISO 18369-2 standard, namely radius of curvature, peak power on the label, diameter, thickness, examination of edges, residues and surface defects, and determination of spectral transmittance. This standard also specifies the equilibrating solution, i.e., standard saline solution, for testing contact lenses.

This standard provides consistent and comparable results among laboratories, manufacturers, and regulatory testing organizations worldwide by establishing standardized procedures for measuring the parameters listed in ISO 18369-2. This standard applies to:

Rigid contact lenses (corneal and scleral)
Soft (hydrophilic) contact lenses
Toric, multifocal and other custom designs.

The basic properties measured include characteristics critical to fit, visual performance, and safety, such as curvature, diameter, thickness, strength, and more. Unless otherwise specified, the methods are designed for finished lenses (ready for dispensing or clinical use) with specific conditioning requirements (e.g., equilibration in standard saline or packing solution at controlled temperature and humidity).

This standard includes precise, repeatable methods for measuring the properties defined in ISO 18369-2. Tests include:

Radius of curvature
Rear peak power
Diameter and thickness
Edge quality, surface defects and inclusions
Spectral transmittance (including UV protection)

It also ensures consistent results among laboratories by defining standard saline solutions for balancing lenses before testing.

The standard “ISO 18369-4 Part 4: Physicochemical properties of contact lens materials” describes the test methods for the physicochemical properties of contact lens materials. These include extraction, rigid lens bending and fracture, oxygen permeability, refractive index, and water content.

This standard includes standardized test methods for evaluating the fundamental physicochemical properties of both rigid (e.g., silicone acrylate, fluorosilicone acrylate) and soft/hydrophilic (e.g., hydrogel, silicone hydrogel) contact lens materials. This applies to finished lenses or lens material samples through tests performed under controlled conditions, and is done to ensure reproducibility. The main tests covered are:

Removable substances (leaked/removable): To determine the amount of any residual monomers, initiators, or other compounds that may pass from the lens into the eye.
Rigid lens flexibility and fracture: Mechanical strength and resistance to deformation or fracture under applied force.
Oxygen permeability: This is critical for evaluating how well the material allows oxygen to reach the cornea.

This standard focuses on material testing, including the following:

Extraction tests (to check for leached substances)
Flexibility and refraction (for rigid lenses)
Oxygen permeability (this value is very important for eye health)
refractive index
Water content (for hydrogel lenses)

High oxygen permeability reduces risks such as corneal swelling, while ensuring low extraction biocompatibility.

In general, the ISO 18369 standard provides a framework for ensuring the quality, safety, and consistency of contact lenses worldwide. This standard applies to all contact lenses that are fitted to the front surface of the eye and come into contact with the tear film. These standards are recognized globally, including by the U.S. Food and Drug Administration (FDA).

This standard is crucial for manufacturers, eye care professionals, and regulators. It helps ensure that contact lenses, whether soft, hard, daily use, or long-term use, are safe, effective, and correctly labeled.

The ISO 18369 standard facilitates global trade and enhances security by harmonizing requirements. For example,

Compliant with FDA classifications for lens materials.
It supports claims of UV blocking: Lenses that meet specific transmittance criteria can be labeled as Class 1 or Class 2 UV protectors.
It ensures compatibility with the cleaning product and reduces complications caused by improper cleaning.

Studies on UV transmittance in disposable lenses refer to the ISO 18369 standard to verify manufacturer claims and help practitioners recommend reliable options.

Today's advancements in materials like silicone hydrogel are reflected in updated classifications, providing better oxygen flow and longer service lives.

In conclusion, the ISO 18369 standard is not merely a technical document, but a cornerstone of modern contact lens safety and innovation.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services compliant with the ISO 18369 standard.