Does the World Health Organization criterion adequately define glaucoma blindness?

Figures & data

Figure 1 The variability in the scores of the type of visual field between assessor A and B for upper and lower hemifield.

Notes: The x-axis represents the scores that are given for upper and lower hemifield; 1) overall sensitivity loss, 2) nasal step, 3) para-central scotoma, 4) arcuate scotoma, 5) altitudinal defect, 6) central island of vision, 7) temporal crescent, 8) hemianopia, and 9) no visual field defect present. The y-axis represents the amount of times each score has been given. The colors blue and green represent assessors A and B, respectively.

Table 1 Frequency of blindness according to the WHO criterion (N=423 visual fields)

	Assessor A, N (%)	Assessor B, N (%)	Kappa	Percentage agreement
WHO criterion score
Blinda	61 (14.4)	48 (11.3)	0.78	95.0
Not blind	362 (85.6)	375 (88.7)

Note:

a Blind = visual field <10° in a radius around central fixation.

Abbreviation: WHO, World Health Organization.

Table 2 Frequency of blindness according to the 5-point ordinal scale, dichotomized (N=423 visual fields)

	Assessor A, N (%)	Assessor B, N (%)	Kappa	Percentage agreement
5-Point ordinal scale, dichotomized
Blinda	92 (21.7)	83 (19.6)	0.71	90.3
Not blindb	331 (78.3)	340 (80.4)

Notes:

a Blind = the score “blind”, “most probably blind”, and “probably blind” according to the 5-point ordinal scale;

b Not blind = “probably not blind” and “not blind” according to the 5-point ordinal scale.

Table 3 Frequency of blindness according to the WHO criterion and 5-point ordinal scale, when visual field type was rated similarly (N=224 visual fields)

	Assessor A, N (%)	Assessor B, N (%)	Kappa	Percentage agreement
WHO criterion score
Blinda	41 (18.3)	35 (15.6)	0.91	97.3
Not blind	183 (81.7)	189 (84.4)
5-Point ordinal scale, dichotomized
Blindb	64 (28.6)	59 (26.3)	0.72	97.5
Not blindc	160 (71.4)	165 (73.7)

Notes:

a Blind = visual field <10° in a radius around central fixation;

b Blind = the score “blind”, “most probably blind”, and “probably blind” according to the five-point ordinal scale;

c Not blind = “probably not blind” and “not blind” according to the five-point ordinal scale.

Abbreviation: WHO, World Health Organization.

Table 4 Assessment of type of visual field (defect) with the 5-point ordinal scale

Type of visual field (defect)	5-Point ordinal scale
	Assessor A Upper hemifield	Assessor B Upper hemifield	Assessor A Lower hemifield	Assessor B Lower hemifield
Overall sensitivity loss	Not blind	Not blind	Not blind	Not blind
Nasal step	Not blind	Not blind	Not blind	Not blind
Para-central scotoma	Probably not blind	Probably not blind	Probably not blind	Probably not blind
Arcuate scotoma	Probably not blind	Probably not blind	Probably not blind	Probably not blind
Altitudinal defect	Probably not blind	Probably not blind	Probably blind	Probably blind
Central island of vision	Most probably blind	Most probably blind	Most probably blind	Most probably blind
Temporal crescent	Blind	Blind	Blind	Blind
Hemianopia	Probably blind	Not blind	Probably blind	Not blind
No visual field defect present	Not blind	Not blind	Not blind	Not blind