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Table 3 Definitions of disease incidence and progression

From: The Nakuru eye disease cohort study: methodology & rationale

Disease

Incidence

Progression

Definition

At risk

Cases

At risk

Cases

Blindness and Visual Impairment (VI)

Blind: Persons with VA of ≥3/60 in the better eye at baseline.

Persons who have VA of <3/60 in the better eye at follow up who had ≥3/60 in the better eye at baseline

Categorical changes in visual acuity between: Normal; Mild VI; Moderate VI; Severe VI; Blind, with a minimum of two line Snellen equivalent change in VA.

Cataract

Persons without evidence of cataract at baseline based on WHO simplified cataract grading systems

Persons with evidence of cataract at follow-up based on WHO simplified cataract grading systems [45] who did not have evidence at baseline

Persons with evidence of any grade of cataract at baseline based on WHO simplified cataract grading systems

Persons who increase by two or more severity grades in each sub-type of cataract.

Primary open angle glaucoma

Persons without glaucoma in either eye at baseline based on ISGEO [46] criteria

Persons who develop ISGEO classification 1, 2 or 3 glaucoma by the 6-year follow-up point

Glaucoma or glaucoma suspect case at baseline

Definite, disc or field progression. See below* [47]

Age-related macula degeneration

Persons who did not have any evidence of AMD at baseline in both eyes

Persons with evidence of early, late or specific AMD lesions

AREDS [48] step 9 or less (no AMD or early AMD) at baseline.

2-or-more-step increase in combined AREDS score from baseline in persons with gradable fundus photographs at both time points.

Diabetic retinopathy

Persons with diabetes and free of retinopathy at baseline and persons developing DM by follow up.

Persons with signs of DR (ETDRS) [49]

Persons with diabetes and minimal or moderate DR at baseline

(1) Persons who develop severe DR by the 6-year follow-up

CSME and incidence of proliferative or severe DRϒ

(2) Increase by ≥ 3 steps on the ETDRS Severity Scale or development of proliferative DR necessitating photocoagulation therapy or vitrectomy

  1. *Definite progression will be defined as those with a combination of ≥0.2 VCDR increase in either eye and/or ≥0.2 VCDR asymmetry between the two eyes with a corresponding progression on the visual field test defined as (TBC – either “expert analysis” or an arbitrary objective measure).
  2. Note: More specific definitions will be provided in subsequent papers.