MACULAR PIGMENT OPTICAL DENSITY IS LOWER IN TYPE 2 DIABETES, COMPARED WITH TYPE 1 DIABETES AND NORMAL CONTROLS.
OBJECTIVE
This study was designed to investigate the optical density of macular pigment in Type 1 and Type 2 diabetes subjects relative to normal controls.


METHODS
One hundred and fifty subjects were recruited to the study and divided into one of the three study groups on the basis of their health status, as follows: Group 1: Healthy controls; Group 2: Type 1 diabetes; Group 3: Type 2 diabetes. Macular Pigment Optical Density, at 0.5° of retinal eccentricity, was measured using customized heterochromatic flicker photometry. Dietary intake of macular carotenoids was quantified using a lutein and zeaxanthin food frequency questionnaire. Diabetes type, duration, medication, smoking habits, glycosylated hemoglobin (HbA1C), and serum lipid levels were recorded, whereas visual acuity, body mass index, and diabetic retinopathy grade were measured for each participant.


RESULTS
One-way analysis of variance revealed a statistically significant difference in body mass index, age, high-density lipoprotein cholesterol and HbA1C between the three groups (P < 0.01 for all). Chi-square analysis revealed a statistically significant difference in diabetic retinopathy distribution (P < 0.01). None of these variables exhibited a statistically significant correlation with macular pigment optical density for any study group (P > 0.05 for all). There was no difference in dietary carotenoid intake between groups. Macular pigment optical density was lower among Type 2 diabetes subjects (0.33 ± 0.21) compared with Type 1 diabetes (0.49 ± 0.23) and controls (0.48 ± 0.35). General linear model analysis, including age, body mass index, diabetes duration, diabetic retinopathy status, high-density lipoprotein cholesterol, and HbA1C as covariates, revealed a statistically significant effect of diabetes type on macular pigment optical density (F = 2.62; P = 0.04).


CONCLUSIONS
Macular pigment optical density was statistically significantly lower in Type 2 diabetes compared with Type 1 diabetes and normal controls. Although body mass index was higher in the Type 2 diabetes group, the lower macular pigment optical density levels observed among Type 2 diabetes seem not to be attributable to differences in dietary carotenoid intake or to the specific presence of diabetes, diabetic control, duration, or diabetic retinopathy.
*Department of Optometry, School of Physics, College of Sciences and Health, Dublin Institute of Technology, Dublin, Ireland; †Department of Ophthalmology, Mater Misericordiae University Hospital, Dublin, Ireland; ‡School of Medicine and Medical Science, University College Dublin, Dublin, Ireland; §School of Biological Sciences, College of Sciences and Health, Dublin Institute of Technology, Dublin, Ireland; and ¶African Vision Research Institute, Faculty of Health Sciences, University of KwaZulu Nalal, Durban, South Africa.
Grainne
G
Scanlon
Paul
P
Connell
Matthew
M
Ratzlaff
Brittany
B
Foerg
Daniel
D
McCartney
Audrey
A
Murphy
Karen
K
OʼConnor
James
J
Loughman
D000328:Adult; D000368:Aged; D015992:Body Mass Index; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D004032:Diet; D005247:Feeding Behavior; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D064368:Healthy Volunteers; D006801:Humans; D008055:Lipids / Q000097:blood; D014975:Lutein / Q000008:administration & dosage / Q000378:metabolism*; D065348:Macular Pigment / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010783:Photometry; D014792:Visual Acuity / Q000502:physiology; D065146:Zeaxanthins / Q000008:administration & dosage / Q000378:metabolism*
D006442:Glycated Hemoglobin; D008055:Lipids; D014975:Lutein; D065348:Macular Pigment; D065146:Zeaxanthins; C517652:hemoglobin A1c protein, human