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L. Ahmadian, R. W. Massof; Visually Impaired Patients May Experience Depression Differently. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3755.
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To determine the prevalence, pattern, and the severity of depressive symptoms and to asses the impact of medical conditions on measurement of depression in low vision patients.
Participants were recruited from a low vision rehabilitation center. Depressive symptoms were assessed with the 15-item version of the Geriatric Depression Scale (GDS) for fit to the Rasch model that constructed a hierarchy of the patients, ordered by the depression level. We also used an interviewer administered comorbidity questionnaire to measure the morbidity caused by a wide range of medical conditions. Differential item functioning (DIF) was performed to examine the confounding effects of age, education, gender, and medical conditions on measurement of depressive symptoms. Cognitive impairment was defined as a mental status examination score of 7 or below, as measured by the Short Portable Mental Status Questionnaire (SPMSQ).
The study included 164 low vision patients of whom 90 (55%) were women with mean age of 69.2 + 17.2. The mean GDS raw score was 2.2+ 2.9(SD). Seven patients (4%) had score above 10 and twenty five patients (15%) had scores between 5 and 10, indicating severe and mild depression levels respectively. The SPMSQ score of the whole sample ranged from 6 to 10, an average of 8.9 + 0.83. Only 6 (3 %) patients had mild cognitive impairment. The mean depression measure (logits) of the sample (- 2.82 + 1.71) and the items (0.00 + 1.21) were not adjacent to each other, indicating that the difficulties of the items and the sample’s severity of depression were not quite well matched. Person and item separation measures were 1.24 and 3.43, respectively. No item had a significant DIF for age, education, race, and comorbidity index. Patients with more severe depression were more likely to endorse items # 5 (being in good spirits) and #11(wonderful to be alive) that had extreme difficulty. Items #2, #4, #8, and #9, asking about dropping activities and interests, feeling bored, helpless, and staying at home had the lowest difficulty.
Comparing to the general population, our Rasch analysis on the GDS showed a unique item distortion. This may indicate that low vision patient responses to some items describing generic symptoms of depression such as anhedonia, pessimism, and lack of energy could be a consequence of the visual impairment per se instead of depression. In low vision patients, depression appears to present with more severe symptoms such as thoughts about death or suicide and poor concentration, memory or attention.Confounding factors of age, education, race, and severity of medical conditions may have no impact on measurement of depression in low vision patients.
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