Serum retinol below which level is considered to be an indicator for xerophthalmia?

The following are the prevalence criteria for determining xerophthalmia problem: Criteria Prevalence in 6 month to 6 years population Night blindness >1% Bitot's spots >0.5% Corneal xerosis/ulceration >0.01% Corneal ulcer >0.05% Serum retinol <10 mcg/dl >5% Ref: Park 22nd edition, page 571