Maximization of a patient’s health related quality of life (HRQOL) is one of the main goals of any clinical intervention. It is assumed that chronic diseases such as glaucoma may have a substantial negative impact on the quality of life. Glaucoma induced reductions on quality of life (QOL) are reported to be similar to those reported with other chronic non-ocular diseases. QOL is strictly defined as a subjective, individual assessment of life quality. There are no reports of quality of life in subjects who have undiagnosed glaucoma. Thus, it is not known whether the disease itself, or the knowledge of a potentially blinding state – even ocular hypertension – will reduce the quality of life.
The quality of life has also been found to decrease in patients with glaucoma as in patients with other ocular pathologies i.e. diabetic retinopathy, cataract and age related macular degeneration. Glaucoma exerts more of a mental burden of disease and limits visual functions requiring good peripheral vision (i.e. driving) while visual tasks requiring good central visual acuity are retained. When one considers cataract, diabetic retinopathy (especially maculopathy) and age related macular degeneration, tasks requiring good central visual acuity are more impaired.
As disease severity increases, QOL is anticipated to deteriorate. QOL measures are increasingly recognized as important outcomes in understanding the impact of a disease and evaluating the effectiveness of healthcare interventions. Measurement of utilities is essential for an economic evaluation of interventions.
Interest in the measurement of health-related quality of life (HRQOL) has increased markedly in recent years. Information regarding the impact of glaucoma on the ability to function and the patients’ QOL is useful in various ways. It can assist in therapeutic choices and suggest alterations to the patient’s home environment to minimize problems with obstacles, lighting, or performance of common everyday tasks. These adaptations might allow more years of unassisted living for elderly patients. There is no general consensus on the concept of HRQOL.
A wide variety of different quality of life measurement tools or questionnaires have been reported in the scientific literature to assess a patient’s subjective quality of life. Some of the scoring systems can also be quite non-user-friendly and require application of rather complicated mathematics.
Disease-specific and generic (non-disease-specific) measures are being increasingly developed and applied in different studies. Although generic QOL instruments capture a broad range of health status aspects and thus they allow comparisons among different diseases. They do not, necessarily, capture the patient’s perception of the specific aspects of a disease, such as glaucoma. None of the non-disease-specific measures can claim to have established a position as the golden standard of HRQOL measure.
Disease-specific instruments have been suggested to be more sensitive at detecting small changes in the condition-specific health status compared to a generic QOL instrument. It is also possible that they are more acceptable for the patient than generic instruments, as they are of better relevance to the patient’s condition.
There are a number of well-documented tools that have been used to quantify the subjective status of glaucoma patients. The generic instruments include e.g. the Medical Outcomes Study Short Form-36 (SF-36) and the Sickness Impact Profile (SIP).
Vision specific instruments such as the VF-14 and the National Eye Institute Visual Function Questionnaire (NEI-VFQ) have been designed with ophthalmological considerations in mind but they are not glaucoma specific. The VF-14 was originally developed to measure the functional degradation of cataract patients. The NEI-VFQ is currently a widely used and published scoring system in glaucoma research. The NEI-VFQ has been translated into various languages and been validated in different clinical populations including glaucoma patients. VF-14 and the NEI-VFQ have, however, not been officially translated and validated in Finland. Glaucoma specific instruments have also been developed but none of them has yet to achieve an established position in the scientific literature.
At the time the patient learns that he/she is suffering from glaucoma more than 80% experience negative emotions. A significant number of patients experience fear of going blind due to glaucoma. Only 14% of patients rated their vision as poor or very poor at the time of the diagnosis and half of the patients did not experience any visual symptoms. It has also been reported that bilateral glaucoma affects the quality of life more than the unilateral disease.
Patients with glaucoma require life-long outpatient care and regular ocular antihypertensive medication, which may be difficult to administer, especially for an elderly person. Further problems are caused by the practical inconvenience of constant and regular follow-up visits and examinations. In addition, the unpleasant adverse effects associated with some topical glaucoma treatments can limit compliance and further reduce QOL.
Central visual acuity is not as good a predictor of the quality of life in glaucoma as assessment of visual field damage. Serious consequences of reduced vision may include personal injuries from falling especially among elderly patients. Degradation of visual ability associated with glaucoma can impair a patients’ ability to perform many common activities.
Glaucoma usually produces certain characteristic visual field defects in the peripheral vision. Glaucomatous visual field damage may lower the quality of life of a glaucoma patient. The degree of QOL deterioration correlates with the severity of the visual field damage.
In the two independent studies, central vision and out-door mobility were the main priorities of the patients. These concerns remained the same in all demographic, clinical, and visual states of participants. In the latter study, there was an interesting trend that as a measure of binocular field loss increased, the relative importance of central vision also increased, whereas when the visual field deteriorated, the relative importance of outdoor mobility decreased.
The 15D is a generic, comprehensive (15-dimensional), self-administered instrument for measuring HRQOL among adults (age over 16 years). It has the advantages of providing a profile combined with a preference-based, single index measure. The 15D has been standardized in the Finnish population and used widely in different research settings, also in ophthalmology. The 15D is not a disease specific test but it is one of the few standardized tests that have a question regarding vision. The question about seeing has been shown to be sensitive when visual acuity is altered. This instrument has been used previously in a Markov model regarding glaucoma screening.
Two glaucoma populations (Oulu and Turku) were compared in terms of resource consumption and quality of life. This seems to be the first study to report 15D results in a glaucoma population.
Apart from the statistically significant difference in the early glaucoma groups, patients residing in Oulu seemed to have an equally good quality of life as patients in Turku even though there were more glaucomatous patients and their disease was more often more advanced than in Turku. From the patients’ perspective, it is of course reassuring to be able to live a good life in spite of a chronic eye disease. From the taxpayer’s viewpoint, it is worthwhile to ask whether the money was spent well. It might be disturbing that the higher use of financial resources as well as the more vigorous treatment pattern in Oulu did not appear to have any effect in the 15D vision or total scores.
One would expect that patients with the same disease severity level receiving more care would have better outcomes and better quality of life. However, the significant difference in the early glaucoma groups points in the opposite direction, i.e. the patient group using more resources actually reported worse quality of life. Moreover, it seems that the higher resource allocation in Oulu in every glaucoma stage, does not appear to make any difference in the quality of life of the patients compared to those in Turku. With regard to the stage of glaucoma, the results were also controversial as patients in Oulu had more glaucoma at the severe stages. This finding may be confounded by an unintentional selection bias. It seems that higher resource consumption provides equal results.