nutritional disorders
Vitamin A Deficiency
Diagnosis ofVitamin ADeficiency
Serum retinol levels, clinical evaluation, and response tovitamin A Ocular findings suggestvitamin Adeficiency. Dark adaptation can be impaired in other disorders (eg, zinc deficiency, retinitis pigmentosa, severe refractive errors, cataracts, diabetic retinopathy). If dark adaptation is impaired, rod scotometry and electroretinography are done to determine whethervitamin Adeficiency is the cause. Serum levels of retinol are measured. Normal range is 28 to 86 mcg/dL (1 to 3 mcmol/L). However, levels decrease only after the deficiency is advanced because the liver contains large stores ofvitamin A. Also, decreased levels may result from acute infection, which causes retinol-binding protein and transthyretin (also called prealbumin) levels to decrease transiently. A therapeutic trial ofvitamin Amay help confirm the diagnosis. 