Dry Eye Scale Focuses on Symptoms and Quality of Life

Damian McNamara

August 20, 2013

Dry eye symptoms adversely affect quality of life for many patients independent of the clinical signs of the disease, leaving clinicians who want to assess the full effect of the condition with a challenge.

Currently available dry eye disease (DED) rating scales either do not take all factors into account, including psychological or social effects, or are too long and time-consuming to be practical for everyday use, according to a new study published online August 15 in JAMA Ophthalmology.

Enter the Dry Eye–Related Quality-of-Life Score Questionnaire (DEQS), a potential solution in the form of a 15-item measure designed and validated by researchers in Japan. "We developed the DEQS as a questionnaire that can be easily used in routine clinical practice to assess symptoms and their effect on quality of life of [DED]," Yuri Sakane, MD, from the Department of Ophthalmology at Ehime University School of Medicine in Shitsukawa, Japan, told Medscape Medical News. The DEQS questionnaire also can gauge response to therapy, Dr. Sakane added.

This dual utility makes the DEQS useful for both ophthalmologists and general physicians diagnosing and treating patients seeking relief from their DED symptoms, Dr. Sakane said.

The DEQS aims to detect the multiple potential effects of DED on patients with the inclusion of 2 subscales: Impact on Daily Life and Bothersome Ocular Symptoms. Clinicians can calculate a summary score for the 15 items to quickly assess the effect of the disease. Dr. Sakane and colleagues demonstrated high internal consistency and good to excellent test–retest reliability.

After the investigators pared down a potential 45 DED items to 35, they tested the initial instrument in 20 patients. On the basis of participant feedback about any confusing or overlapping questions, the DEQS emerged as a 24-item questionnaire that took an average of 9 minutes, 19 seconds to complete.

Next, the investigators conducted a preliminary validation study with 142 adults aged 20 years or older. Participants included 112 people with abnormal tear function and symptoms associated with DED and 30 unaffected control patients. Participants rated the frequency of symptoms from 0 (none) to 4 (highest frequency) on a 5-point Likert scale and the severity of symptoms from 1 to 4 (with a larger number indicating a higher burden) on a 4-point Likert scale.

The results spurred the removal of 9 more items from the questionnaire, yielding the final 15-item DEQS assessed further in a full validation study with 203 DED patients and 21 control patients. The mean ages were significantly different for the 2 groups at 71.0 years for patients and 63.9 for control participants (71.0 years for patients). Women made up the majority of the participants.

The investigators validated the DEQS through health assessments of study participants with the Short Form–8 Health Survey (SF-8) and a Japanese version of the 25-item National Eye Institute Visual Function Questionnaire (VFQ-25).

"The mental component score of the SF-8 and 4 subscales of the VFQ-25 (Ocular Pain, Distance Vision, Mental Health, and Dependency) were significantly lower in the DED group than in the control group [P < .001]," Dr. Sakane said. "Low subscale scores related to the mental health of DED patients in both the SF-8 and the VFQ-25 shows the bothersome symptoms and visual disturbance of DED may have affected...the patient's mental health more than we expected."

The investigators also found that the summary score and each subscale score were significantly higher in the DED group compared with the control group (P < .001). In addition, both SF-8 components and all the VFQ-25 subscales except Social Function and Color Vision showed significant differences between the DED and control groups.

When asked by Medscape Medical News to comment on the new tool, Konrad Pesudovs, PhD, foundation chair of optometry and vision science at Flinders University School of Medicine in Bedford Park, South Australia, said, "The instrument does not have interval scaling properties; therefore, it is not valid." Dr. Pesudovs published a comparison study of 16 different patient-reported outcome instruments suitable for cataract assessment ( Invest Ophthalmol Vis Sci. 2012;53:4042-4054).

In response, Dr. Sakane said, "A Likert scale is a psychometric scale commonly used in questionnaires and is the most widely used scale in survey research. Whether individual Likert items can be considered as interval-level data is the subject of considerable disagreement in the literature." Dr. Sakane added, "Likert-type scales are ordinal data but [are] very commonly used with interval procedures, provided the scale item has at least 5, and preferably 7, categories."

A limitation of the study is that DEQS was only validated in Japan and will require translation and cross-cultural adaptation before more widespread clinical use.

Future plans include the development of a tablet-based version of the DEQS. An electronic version would be more convenient for patients, reduce the likelihood they will miss a question, and make calculation of the summary score easier for clinicians, Dr. Sakane said.

The study was supported by Santen Pharmaceutical Co, Ltd. The authors and Dr. Pesudovs have disclosed no relevant financial relationships.

JAMA Ophthalmol. Published online August 15, 2013. Abstract

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