LOCS II Standard

The LOCS II standard transparency contains fewer standard images than that of LOCS III. LOCS II uses an integer scale (e.g. I, II, III, IV, etc.) and intermediate grades (e.g. between I and II) are not possible. LOCS II was widely used in epidemiological studies of risk factors for the three classes of age-related cataract (see LOCS III Bibliography.pdf), but when users expressed interest in assessing the effect of various factors on the rates of cataract progression, a more robust system of grading longitudinal changes (rates) was developed. This led to the introduction of LOCS III.

Each set of the LOCS II standards contains the following:

LOCS II Instructions*


A reprint of the original article describing the development of the LOCS II system


LOCS II color transparency

         The LOCS II standard transparency set contains slit and retro-illumination images. The LOCS II set contains one slit image for grading nuclear color (NC) and four slit images for grading nuclear opalescence (NO), five retroillumination images for grading cortical cataract (C), and four  retroillumination images for grading posterior subcapsular (P) cataract. Cataract severity is graded on an integer scale. The grading intervals are approximately equal within each scale. The simplicity of the system and its ease of use underlies its wide appeal as a simple, sensitive, validated method for assessing cataract type and severity.


  1. *Other Languages?

  2. Written LOCS III Instructions are available in the languages listed below. If they are needed in a language not currently offered, arrangements can be made for a translation with the contractor bearing the related costs of such translation:


  3. Brazilian, Bulgarian, Croatian, Czech Republic, Danish, Dutch, English, Finnish, French, German, Hungarian, Italian, Japanese, Korean, Ukrainian, Polish, Portuguese, Romanian, Russian, Slovakian, Slovenian, Spanish, Swedish, Thai, Turkish.

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