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Table 1 Comprehensibility problems of the Impact of Vision Impairment (IVI) (n = 12) and possible solutions

From: Translation and content validity of the Dutch Impact of Vision Impairment questionnaire assessed by Three-Step Test-Interviewing

Subcategory Problem description Item-formulation Quotations Possible solutions for the Dutch version IVI
Item specific problems– Sentence structure Comprehensibility problems resulting from (complex) sentence structure (Item 12) In general, how much has your eyesight interfered with travelling or using transport? (bus and train) “Only buses and trains were specifically mentioned, so I just thought of these options in my response” Changing and to or (Bus or train) to clarify these are examples and not a ‘checklist’.
Item specific problems– vocabulary and formulation Comprehensibility problems resulting from the use of vocabulary, unclear formulation or lack of specified formulation (Item 3) Shopping? Finding what you want and paying for it? (R5) “Shopping … I don’t go shopping” (Step 1 (TSTI)
(R5) “I did not interpret the question widely, for example including shopping for groceries, I only thought about buying clothes, that is what the word shopping means to me” (Step 2 TSTI)
Adding ‘for example groceries’
(Item 15) Getting information that you need? (R5) “What kind of information is meant here? Information concerning my eyes? I do not understand the meaning of the question”
(R6) “Do they mean reading information about medicines here?”
(R7) “What is meant with information here? Perhaps what I have to read?”
(R9) “Information that I have to read? Ah.. Yes I think it is information that I read”
(R8) “Is that information that I get using my iPad?”
Clarify what kind of information (read).
(item 19) In the past month, how often has your eyesight stopped you from doing the things you want to do? (R7) “How often … does that means I have to fill in a number” Changing the formulation of an item to fit with response category
Item specific problems– influence of conditions or composite items Comprehensibility problems resulting from different conditions while performing a task that can influence the response or any problems resulting from composite items (Item 2) Taking part in recreational activities such as … (R8) “This would only apply to me when it gets dark. I can’t answer this question” Adding conditions in item formulation, for example under normal lighting conditions
(Item 5) Recognizing or meeting people? (R3) “Actually, I have no problems at all meeting people, but recognizing people is very difficult for me”
(R12) “Well … that depends on the lighting conditions”
Split item; recognizing and meeting people
(Item 12) In general, how much has your eyesight interfered with travelling or using transport? (bus and train) (R9) “Well, I never use public transport and we do not travel anymore … I think that is easy to answer … ehm … well … actually, we do travel by car and fortunately, I don’t have any problems driving a car.”
(R10) “Yes.. that is different: I know which bus I have to take and where to get off. I have often travelled by train, but now there are a lot of new stations which makes it more difficult for me to travel. But I still do it.”
(R12) “I have no problems taking the bus, but I have only taken the train once.”
Split item; travelling could be interpreted as driving a car; separate item
Item specific problems– influence of comorbid disorders Comprehensibility problems resulting from items not necessarily targeting vision problems (answers based on interpretation of the question for comorbid disorders) (Item 3) Shopping? (finding what you want and paying for it)   Items 3, 4, 7, 17, 18: include eyesight in item formulation
Items 10, 11, 19 (and 3, 4, 7, 17, 18): clarify ‘n/a’ response category for example don’t do this for other reasons than because of my eyesight (general comprehensibility)
(Item 4) Visiting friends or family?  
(Item 7) Opening packaging? (For example, around food, medicines) (R1) “I find it difficult, but that has to do with my hands, not because of my eyesight.”
(R3) “This is difficult, but has nothing to do with my eyesight, but with how things are packaged sometimes”
(R6) “Actually, this does not apply to my eyes, but I have trouble with it, so I chose the answer ‘not applicable’.”
(Item 10) How much has your eyesight interfered with getting about outdoors? (on the pavement or crossing the street)  
(Item 11) In the past month, how often has your eyesight made you go carefully to avoid falling or tripping?  
(Item 17) Spilling or breaking things? (R12) “Yes, sometimes, which has to do with my [comorbid disorder] and not because of my eyes”
(Item 18) Your general safety when out of your home?  
(item 19) In the past month, how often has your eyesight stopped you doing the things you want to do? (R12) “Yes, sometimes, which has to do with my [comorbid disorder] and not because of my eyes”
Problems response category Responding problems resulting from not understanding when to choose response categories ‘never’ and ‘n/a’ n / a   Include examples in instructions in which the situation ‘never’ and ‘n/a’ response category is suitable.
Clarify ‘n/a’ response category for example I don’t do this for reasons other than my eyesight.
Problems with instructions Responding problems resulting from misinterpreting or forgetting the instructions n / a   Repeatedly include the instructions in the questionnaire, and where possible, included them in item-formulation (shortened version or remark)
Problems with instructions Responding problems resulting from not understanding the layout or structure of the questionnaire regarding the ‘presentence’ n / a “Despite the sentences being longer, the readability and understandability of the questions will improve” Include ‘presentence’ in all item formulations.