Project: Structural Equation Modeling and Its Application to Quality of Life of Visually Impaired
In 2001 the World Health Organization (WHO) established a new classification for the description of health and disability, known as International Classification of Functioning Disability and Health (ICF). The classification has now been accepted by 191 countries as the international standard to describe and measure health and disability.
While traditional health indicators are based on the mortality (i.e. death) rates of populations, the ICF shifts focus to "life", i.e., how people live with their health conditions and how these can be improved to achieve a productive, fulfilling life. In the ICF model, disability (quality of Life) and functioning (functional visual ability) are viewed as outcomes of interaction between health conditions (visual impairment) and external environmental factors such as social attitudes; and internal personal factors, which include age, sex, and education. The ICF therefore provides different perspectives as to how measures can be targeted to a person’s ability to live a full life.
However, ICF has not been verified among people with visual impairment. Studying these relationships will allow health care managers and low vision professionals to gain insight into the development and utilisation of eyecare services, for example low vision services, for the improvement in quality of life of people with impaired vision.
In her PhD Rishita quantified the links proposed in the ICF. She constructed a model of relationships among perceived visual ability, quality of life (QoL) and Visual Acuity (VA) among visually impaired people (presenting VA < 6/18) people aged 40 years or above in India. This was done using the structural equation modeling (SEM) technique, which can be used to estimate the direct and indirect relationships between VA and QoL.
The findings of this project demonstrated that the level of vision impairment was directly associated with Quality of Life and also indirectly through their perceived functional ability. Overall, 62% of the total 18% change in the QoL was mediated through the visual function score.
QoL of visually impaired people can therefore be improved by improving their VA by intervention such as cataract surgery. Among persons whose vision cannot be improved through any treatment, QoL can be improved to some extent (although not 100%) by providing low vision services. Further studies are required to assess the effectiveness of low vision intervention in the enhancement of patients’ QoL.
By providing the treatment / training to improve the daily living skills, mobility and by explaining the natural course of the eye disease and visual prognosis, QoL of the visually impaired can be improved. Further longitudinal studies on the impact of therapy for glaucoma, corneal disease and retinal disease on QoL and functional vision are needed.
Rishita received her Masters degree in Biostatistics from Madras University, India in 1996. She joined the LV Prasad Eye Institute in 1999 and has been involved in various clinical trials, and has published more than 40 articles in peer-reviewed journals. She completed her PhD at the Vision CRC in April 2007. |
