Validation of Farsi Translation of the Ocular Surface Disease Index.

PURPOSE: To develop and validate a Farsi version of Ocular Surface Disease Index (OSDI) for the Iranian population.
METHODS: This study was a translation and cross-cultural adaptation and validation of Farsi version of OSDI. Four bilingual (English-Persian) individual including three physicians and one native English teacher were asked to translate the original English OSDI questionnaire in Farsi. Following back and forth translation, integration and pilot check, the translation team came to consensus on translation. Consecutive patients visited in ophthalmology clinic, underwent comprehensive general ophthalmology exam and specific assessments for dry eye including non-anesthetic Schirmer's test, fluorescein tear break-up time, Fluorescein and Rose Bengal staining and Farsi OSDI (F-OSDI). F-OSDI was again rechecked within 2-7 days after the examination.
RESULTS: Forty-four participants were enrolled into study. Thirty-two (72.7%) were male and 12 (27.3%) female. Mean age of participants was 45.5 (SD = ±15.97, range = 18-80) years. Twenty five percent were less than 31 years old and 10% percent older than 65. The cronbach's alpha for the questionnaire was 0.807. Questions number 7, 8 showed excellent, and question12 showed good internal consistency, respectively. There was a significant correlation between all pre measures and post assessments.
CONCLUSION: The obtained F-OSDI showed acceptable internal consistency and test-retest reliability. This F-OSDI could be used for assessment of dry eye, ocular surface discomfort and quality of life in Iranian and Farsi speaking populations.

INTRODUCTION

The Ocular Surface Disease Index (OSDI) questionnaire is a valid instrument[1] to assess how often patients experience symptoms of ocular surface disturbances, including the symptoms of dysfunctional tear syndrome (DTS). Currently, the OSDI is widely used to evaluate symptoms of DTS. It is one of the major criteria for diagnosis of DTS.[2] Furthermore, the OSDI is used to evaluate the severity of disease and effect of treatment targeting the ocular surface. The OSDI is a patient reported measure that generates numerical data. This measure is widely used in diagnosis, assessment of severity, and impact on quality of life of patients with DTS and other ocular surface diseases.[23] It has been suggested by International Dry Eye Workshop (DWEDS) as a valuable instrument in ocular surface disease studies.[3]

The OSDI has undergone transcultural adaptation and validation process into the Spanish,[4] Chinese,[5] Portuguese[6] and Turkish[7] languages. We aimed to translate the OSDI into Farsi and validate it to utilize this essential tool for therapeutic and research purposes.

MATERIALS AND METHODS

The OSDI questionnaire included 12 questions in three domains: ocular symptoms, vision related functioning, and environmental triggers. Each patient rated symptoms on a 5-point scale from always (score 4) to never (score 0) for each question concerning different eye issues.

The sum score of the questions in each domain is the score of that domain. The total OSDI score was defined on scale of 0 to 100 translation process as:

According to the OSDI score, patients were classified as normal or with mild, moderate, or severe dry eye disease. The overall OSDI score defines the ocular surface as normal (0-12 points), or as having mild (13-22 points), moderate (23-32 points), or severe (33-100 points) disease.

Translation

A forward–backward procedure was applied to translate the OSDI from English into Persian. The translation and transcultural adaptation process included translation of the original English version (Outcomes Research Group, Allergan, Inc., Irvine, CA, USA) of the OSDI into Farsi by one English teacher and two bilingual ophthalmologists working individually. Then the translations were unified by consensus. The cultural adaptation was done to ensure the translated questionnaire is easy and understandable for patients who are able to communicate in Persian. The translation was distributed to 15 patients and their understanding was determined. Necessary changes were incorporated to make the questionnaire understandable. The Farsi version was then translated into English and one native English teacher was asked to assess the comprehension.

The final questionnaire was administered to adult participants in an ophthalmology clinic who had been referred for dry eye. All patients underwent a comprehensive general ophthalmology examinations and specific assessments for dry eye, including non-anesthetic Schirmer's test, fluorescein tear break-up time (TBUT) fluorescein and rose bengal staining, and reporting using the Oxford scale and Farsi OSDI (F-OSDI). The F-OSDI was rechecked within 2 to 7 days after the examination.

Patient Population

The study enrolled patients who were referred to our clinic for dry eye between March and August 2013. Patients who were unable to fully communicate in Persian or who did not consent to participate were excluded. Patients with conjunctivitis, a history of contact lens use, previous intraocular or ocular surface surgeries, allergies, or eyelid malpositions were also excluded from the study.

The study was reviewed and approved by the IRB of the eye research center. Consent was obtained from the participants.

Reliability and Validity

Test–retest reliability was examined using weighted kappa between two OSDI evaluations performed 1 week apart. As the responses to OSDI questions are ordinal, the weighted kappa reflects the agreement between the two evaluations more accurately than other measurements, such as Pearson's correlation. As the status of patients can change within days, a short interval was employed between the test and retest times to have results comparable. Internal consistency of the questionnaire was assessed by cronbach's alpha coefficient; an alpha >0.7 was considered acceptable.

RESULTS

Forty-four participants were enrolled in the study; 32 (72.7%) were male and 12 (27.3%) were female. The mean participant age was 45.5 ± 15.97 (range, 18–80) years; the age of 25% of the participants was <31 years and that of 10% of the participants was >65 years. The most frequently listed symptoms were discomfort upon exposure to wind (76.7%) and discomfort in dry weather (76.1%).

The Cronbach's alpha coefficient for the questionnaire was 0.807. Questions number 7, 8 showed excellent, and question12 showed good internal consistency, respectively. There was a significant correlation between all test- and re-test assessments [Table 1]. There was a minor change in the inter-rater coefficient among age groups [Table 2]. Kappa analysis for intra-observer agreement for each question showed that questions 1 (sensitivity to light), 3 (painful eyes), 7 (driving at night), 8 (working with computers or monitors), and 9 (watching TV) had almost perfect agreement, and questions 2 (gritty sensation), 6 (reading), 10 (windy conditions), 11 (dry places) and 12 (areas with air conditions) had substantial agreement. Questions 4 (blurred vision) and 5 (poor vision) had moderate agreement. Responders aged 45 and older showed higher agreement on questions 1, 2, 3, 7, 8, and 9. According to OSDI values, the frequency of dry eye severity scores among the participants included 11.9% normal, 19.0% mild, 16.7% moderate, and 52.4% severe.

Table 1

Evaluation of the repeatability of different facets and domains of the Persian version of the OSDI (n=44)

Table 2

Inter-rater agreement between patients in two age groups

We found few significant correlations between each of the questions and specific dry eye test parameters. TBUT showed a significant correlation with question 10 (windy conditions), fluorescein staining with question 4 (blurry vision), the Schirmer test with question 11 (dry places), and rose Bengal staining with question 1 (sensitivity to light).

DISCUSSION

The OSDI was developed and introduced in 1997 by the Outcomes Research Group (Allergan, Inc.).[8] It includes 12 questions that assess three aspects of DTS consisting of symptoms, severity, and changes of function of the individual. It has been shown that this instrument is valid and reliable for measuring the severity of DTS.[1] The OSDI has been suggested as a measurement tool for DTS in both clinical and research fields by the International Dry Eye Workshop.[23]

This study demonstrated that F-OSDI had high test-retest reliability and high internal consistency in a Farsi speaking Persian population.

The OSDI questionnaire is currently used extensively for clinical and research purposes to assess ocular surface disorders such as DTS, blepharitis, and allergic and inflammatory conditions. The OSDI was developed to evaluate the symptoms and impact of dry eye.[18] It consists of 12 items that assesses symptoms, functional limitations, and environmental factors related to dry eye. Each item has the same five-category Likert-type response option, and each of the three subscales has its own question type. Among other patient reported instruments including McMonnies,[91011] NEI-VFQ-25,[1213] and Bandeen-Roche's questionnaire,[14] the OSDI has shown high reliability and validity for DTS.[1]

DTS is a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface.[2] OSDI is one essential instrument for evaluation of symptoms as part of diagnostic criteria proposed by the DEWS workshop, 2007.[2]

In this study, participants aged 45 and older generally showed higher kappa in questions regarding eye discomfort and visual function compared to younger participants. This may be explained partly by higher severity of dry eye and more consistent dry eye symptoms in this age group. In addition, the higher prevalence of other vision threatening morbidities could elicit more consistent responses to questions regarding vision problems compared to younger age groups. The content validity of the translated F-OSDI could be examined by parallel administration of the OSDI and diagnosis of DTS based on the criteria proposed by the DEWS workshop, 2007.

The main strengths of this study include the recruitment of dry eye Persian patients, systematic evaluations for dry eye and applying current criteria for diagnosis of dry eye. There are limitations in this study. The heterogeneous population of patients in terms of different educational and socioeconomic status and different cognitive abilities might have affected the responses.

In conclusion, the F-OSDI demonstrated satisfactory test-retest, and internal consistency, reliability, and validity for evaluation of dry eye symptoms and quality of life in the patients in this study.

Financial Support and Sponsorship

Nil.

Conflicts of Interest

There are no conflicts of interest.