Cataracts are a leading cause of vision impairment and blindness worldwide. Accurate grading of cataracts is essential for determining the appropriate treatment and monitoring the progression of the condition. This article provides a comprehensive overview of the cataract grading scale, focusing on the World Health Organization (WHO) simplified cataract grading system and other commonly used grading systems.
Here is a comprehensive table of the WHO Simplified Cataract Grading System for the three primary types of cataracts: nuclear sclerotic, cortical, and posterior subcapsular.
| Cataract Type | Grading Category | Description |
|---|---|---|
| Nuclear Sclerotic | NS tr or 1+ | Nucleus clearer than anterior/posterior sections |
| NS 2+ | Nucleus equal to the anterior/posterior sections (same opacity level throughout) | |
| Cortical | Grade 1 | 10% of intrapupillary space obscured |
| Grade 2 | 10%-50% of intrapupillary space obscured | |
| Grade 3 | 50%-90% of intrapupillary space obscured | |
| Grade 4 | >90% of intrapupillary space obscured | |
| Posterior Subcapsular | Grade 1 | 3% of posterior capsule obscured |
| Grade 2 | 30% of posterior capsule obscured | |
| Grade 3 | 50% of posterior capsule obscured | |
| Grade 4 | >50% of posterior capsule obscured |
This table provides an overview of the WHO Simplified Cataract Grading System, which is designed to facilitate the assessment of cataract severity in the field by relatively inexperienced observers[1]. It is important to note that other grading systems, such as the Lens Opacity Classification System (LOCS III) and the NEI/Industry Grading System, may also be used to assess cataract severity.
WHO Simplified Cataract Grading System
In 2002, the WHO published a simplified cataract grading system to facilitate the assessment of cataract severity in the field by relatively inexperienced observers[1]. This system focuses on the most common forms of cataract: nuclear sclerotic (NS), cortical, and posterior subcapsular cataracts.
Nuclear Sclerotic (NS) Grading
Nuclear sclerotic cataracts are graded based on the opacity of the lens nucleus. The grading is best performed with a slit beam at a 30 to 45-degree angle to the cataract. The WHO simplified grading system includes the following categories for NS cataracts:
- NS tr or 1+: Nucleus clearer than anterior/posterior sections
- NS 2+: Nucleus equal to the anterior/posterior sections (same opacity level throughout)
Cortical and Posterior Subcapsular Cataract Grading
Cortical and posterior subcapsular cataracts are graded using retroillumination to evaluate the degree to which the intrapupillary space or posterior capsule are obscured.
Other Grading Systems
Several other grading systems have been used to describe cataract severity, including the Lens Opacity Classification System (LOCS, LOCS II, and LOCS III), the Oxford Clinical Cataract Classification and Grading System, and the Johns Hopkins system. The LOCS III is an improved system for grading slit-lamp and retroillumination images of age-related cataracts, with excellent interobserver agreement[2].
The NEI/Industry Grading System is another method used for cataract grading[3]. Additionally, a Simple Pre-Operative Nuclear Classification Score (SPONCS) has been proposed for grading cataract hardness in clinical studies[4].
Cataract grading is crucial for determining the appropriate treatment and monitoring the progression of the condition. The WHO simplified cataract grading system provides a straightforward method for assessing cataract severity, while other grading systems like LOCS III and NEI/Industry Grading System offer alternative approaches. Accurate cataract grading can help healthcare professionals make informed decisions about patient care and contribute to the prevention of blindness and vision impairment worldwide.
Different Types of Cataracts: How Are They Graded
There are three primary types of cataracts: nuclear sclerotic, cortical, and posterior subcapsular[5]. These cataracts are graded using various systems to determine their severity and inform treatment decisions. Some of the most commonly used grading systems include the World Health Organization (WHO) simplified cataract grading system, the Lens Opacity Classification System (LOCS III), and the NEI/Industry Grading System[6][7][8].
WHO Simplified Cataract Grading System
The WHO simplified cataract grading system was developed to facilitate the assessment of cataract severity in the field by relatively inexperienced observers[6]. This system focuses on the most common forms of cataract: nuclear sclerotic (NS), cortical, and posterior subcapsular cataracts.
Nuclear Sclerotic (NS) Grading
Nuclear sclerotic cataracts are graded based on the opacity of the lens nucleus. The grading is best performed with a slit beam at a 30 to 45-degree angle to the cataract[7]. The WHO simplified grading system includes the following categories for NS cataracts:
- NS tr or 1+: Nucleus clearer than anterior/posterior sections
- NS 2+: Nucleus equal to the anterior/posterior sections (same opacity level throughout)
Cortical and Posterior Subcapsular Cataract Grading
Cortical and posterior subcapsular cataracts are graded using retroillumination to evaluate the degree to which the intrapupillary space or posterior capsule are obscured[7][8].
Lens Opacity Classification System (LOCS III)
The LOCS III is an improved system for grading slit-lamp and retroillumination images of age-related cataracts, with excellent interobserver agreement[9]. It consists of six slit-lamp images for grading nuclear color (NC) and nuclear opalescence (NO), five retroillumination images for grading cortical cataract (C), and five retroillumination images for grading posterior subcapsular (P) cataract[7]. Cataract severity is graded on a decimal scale, and the standards have regularly spaced intervals on a decimal scale[7].
NEI/Industry Grading System
The NEI/Industry Grading System is another method used for cataract grading[6]. Additionally, a Simple Pre-Operative Nuclear Classification Score (SPONCS) has been proposed for grading cataract hardness in clinical studies[11].
Cataract grading is essential for determining the appropriate treatment and monitoring the progression of the condition. Various grading systems, such as the WHO simplified cataract grading system, LOCS III, and NEI/Industry Grading System, are used to assess the severity of different types of cataracts. Accurate cataract grading can help healthcare professionals make informed decisions about patient care and contribute to the prevention of blindness and vision impairment worldwide.
Authority Sources
- WHO: A simplified cataract grading system
- PubMed: A cataract classification and grading system
- American Academy of Ophthalmology: NEI/Industry Grading System
- British Journal of Ophthalmology: Grading nuclear cataract: reproducibility and validity of a new method
- WHO: A simplified cataract grading system (Spanish)
- PubMed: A simplified cataract grading system
- American Academy of Ophthalmology: Pediatric Cataracts: Overview
- British Journal of Ophthalmology: Cataract surgery and subtype in a defined, older population: the SEECAT Project
- NCBI: A Simple Pre-Operative Nuclear Classification Score (SPONCS) for Grading Cataract Hardness in Clinical Studies
- WHO: Blindness and vision impairment
- PubMed: The Lens Opacities Classification System III. The Longitudinal Study of Cataract Study Group
Citations:
[1] https://apps.who.int/iris/handle/10665/67221
[2] https://pubmed.ncbi.nlm.nih.gov/8512486/
[3] https://www.aao.org/education/image/neiindustry-grading-system
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7694099/
[5] https://harvardeye.com/uncategorized/what-are-the-three-types-of-cataracts/
[6] https://pubmed.ncbi.nlm.nih.gov/11821974/
[7] https://pubmed.ncbi.nlm.nih.gov/8512486/
[8] https://www.aao.org/education/image/neiindustry-grading-system
[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7694099/
[10] https://www.mayoclinic.org/diseases-conditions/cataracts/symptoms-causes/syc-20353790
[11] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9493415/