Purpose
To ascertain the health-related quality of life associated with symptomatic degenerative vitreous floaters.
Design
Cross-sectional questionnaire survey.
Methods
In this institution-based study, 311 outpatients aged 21 years and older who presented with symptoms of floaters were enrolled. Data from 266 patients (85.5%) who completed the questionnaire were analyzed. Utility values were assessed using a standardized utility value questionnaire. The time trade-off (TTO) and standard gamble (SG) for death and blindness techniques were used to calculate the utility values. Descriptive, univariate, and multivariate analyses were performed using Stata Release 6.0.
Results
The mean age of the study population was 52.9 ± 12.02 years (range, 21–97). The mean utility values were 0.89, 0.89, and 0.93 for TTO, SG (death), and SG (blindness), respectively. Patients aged ≤55 years reported significantly lower SG (blindness) utility values when compared with patients above 55 years of age (age ≤55 = 0.92, age >55 = 0.94, P = .007). Utility measurements did not demonstrate significant relationship with any of the other socio-demographic variables examined in this study. The utility values did not demonstrate any significant relationship with other ocular characteristics such as duration of symptoms, presence of a posterior vitreous detachment, and presence or severity of myopia.
Conclusions
Symptomatic degenerative vitreous floaters have a negative impact on health-related quality of life. Younger symptomatic patients are more likely to take a risk of blindness to get rid of the floaters than older patients.
Floaters are entoptic images of opacities in the vitreous cavity that usually occur as a result of degenerative changes in the vitreous gel such as vitreous syneresis, condensation of vitreous fibers, and posterior vitreous detachment (PVD). Degenerative vitreous floaters may become asymptomatic with passage of time. However, in some patients, symptomatic degenerative vitreous floaters persist for many years and can potentially affect health-related quality of life in several ways. Floaters can result in intermittent blurred vision, glare and haze attributable to migration of vitreous opacities into the visual axis, and interference with important activities of daily living such as reading, driving, and near work.
Individuals with symptomatic degenerative floaters constitute a fair proportion of patients seen in ophthalmology clinics in Singapore. Myopia, which is often associated with degenerative floaters, is a growing public health problem with high prevalence rates in Singapore. The health-related quality of life associated with floaters is not well understood. Of note, Snellen acuity, the standard test of visual function in a clinical setting, is unable to quantify visual disability associated with vitreous floaters on day-to-day functioning and overall quality of life. Although surgical interventions such as Nd:YAG laser vitreolysis, deep anterior vitrectomy combined with cataract surgery, and pars plana vitrectomy are available, they have been offered to patients with symptomatic floaters only rarely.
Health-related quality of life is playing a vital role in every specialty of medicine because of the increasing importance of patient preferences and escalating healthcare costs. Utility values, originally described by Von Neumann and Morganstern in 1940, allow an objective quantification of the functional quality of life associated with a specific disease state. By convention, a utility value of 1.0 implies a perfect health state whereas a value of 0.0 indicates the worst possible health state or death. The closer the value is to 1.0, the better is the perceived health-related quality of life. Currently, utility values modified by Brown and associates are used for measuring health-related quality of life in patients with eye diseases. Utility values are measured using a number of techniques. The time trade-off (TTO) and standard gamble (SG) methods represent 2 common techniques of eliciting preferences under the utility theory. The TTO utility measures the numbers of years of remaining life that an individual is willing to trade off for a hypothetical technology that restores perfect vision, whereas the SG utility assesses the risks associated with a hypothetical technology that the patient is willing to take to return to the perfect health state.
Utility values have been measured for a variety of eye diseases that affect health-related quality of life such as diabetic retinopathy, age-related macular degeneration, glaucoma, and myopia. Understanding the impact of floaters on the overall health-related quality of life can be invaluable in deciding possible treatment options in specific subgroups of patients. In this study, we assess the utility values in patients presenting primarily with a history of floaters.
Methods
In this questionnaire-based study, we enrolled consecutive patients presenting primarily with a history of floaters to the Department of Ophthalmology and Visual Sciences in Alexandra Hospital, Singapore, from April 1, 2006 to December 31, 2007.
Patients were eligible to participate in the study if they satisfied the following criteria: age 21 years and above, history of floaters in 1 or both eyes, best-corrected visual acuity (BCVA) better than 20/30 in the better-seeing eye, no significant coexisting retinal pathology, and willingness to give an informed consent. Patients with acute-onset floaters (defined as floaters of less than 4 weeks’ duration), and high myopia (spherical equivalent equal to or greater than −6.0 diopters [D]) were also included in the study. Patients with floaters secondary to other eye conditions such as vitreous hemorrhage, vitreous inflammation, and ocular trauma were excluded from the study. Similarly, patients with dense corneal or lenticular opacities that hindered optimal visualization of the fundus or those with concomitant ocular diseases resulting in loss of vision were not eligible to participate in the study. Lastly, patients were not enrolled if they were unwilling to answer and/or unable to understand utility value questionnaires because of psychiatric problems or dementia.
A comprehensive eye examination including Snellen BCVA, slit-lamp biomicroscopy, and a dilated fundus examination using indirect ophthalmoscopy was performed for each patient. Additionally, in all participants, demographic and socioeconomic data, such as age, gender, ethnicity, educational status, occupation, housing, personal and family income, and total number of family members, were recorded.
A single trained research assistant interviewed the patients using a standardized utility value questionnaire. Where necessary, the questionnaire was interpreted by the interviewer in the patients’ preferred language. During the face-to-face interviews, the research assistant encouraged the patients to ask questions if they were unable to comprehend the utility questionnaire.
Utility values were calculated using the commonly used techniques of TTO and SG for death and blindness. TTO utility value was calculated based on the time traded in years over the expected number of years of the respondent’s remaining life that he/she is willing to give up for a hypothetical technology to restore perfect health (TTO utility = 1 – [time traded in years/estimated number of years of remaining life]). Standard gamble utility was calculated as the amount of risk (in percentage) of death or blindness that a respondent is willing to take for a hypothetical technology that may restore perfect vision respectively (SG utility = 1 – [amount of risk of death or blindness in percentage that the respondent is willing to take/100]).
Data Analysis
Descriptive, univariate, and multivariate analyses were performed using Stata Release 6.0 (Stata Corporation, College Station, Texas, USA). The mean and median TTO, SG (death), and SG (blindness) utilities were calculated for all patients with floaters. Utility values were compared across different age groups, socio-demographic groups, and patients’ presentation characteristics using the Wilcoxon rank sum test and Kruskal-Wallis test. These nonparametric tests were used for statistical analysis because the normality assumption needed for parametric tests was not satisfied by our sample. All P values quoted are 2-sided and considered statistically significant when the values are below .05. Multiple linear regression analysis was performed after adjusting for the effect of confounding factors.
Results
In this cross-sectional study, 311 consecutive patients presenting primarily with a history of floaters were enrolled. Of these, data from 266 patients (85.5%) who completed the questionnaire were analyzed. The details of demographic and socioeconomic characteristics are presented in Table 1 .
| Demographic Characteristics | Number (%) |
|---|---|
| Mean age (range), years | 52.9 ± 12.02 (21–97) |
| Sex ratio (male:female) | 0.78:1 |
| Ethnicity | |
| Chinese (%) | 239 (89.9%) |
| Non-Chinese (%) | 37 (10.1%) |
| Housing type | |
| Public housing estates | 215 (81.4%) |
| Private housing | 49 (18.6%) |
| Education status | |
| No formal education/primary education | 51 (19.3%) |
| Secondary education | 119 (44.9%) |
| Tertiary education | 95 (35.8%) |
| Average number of family members (range) | 3.48 (1-7) |
| Employment status (%) | |
| Employed | 174 (65.9%) |
| Unemployed/retired | 90 (34.1%) |
| Average monthly income (USD) | |
| Personal | 1665 |
| Family | 2371 |
Utility Values
The mean utility values for our study population were 0.89, 0.89, and 0.93 for TTO, SG (death), and SG (blindness), respectively.
Utility Values and Demographics
The details of utility values associated with various demographic factors are shown in Table 2 . Time trade-off and SG (death) utility values did not differ significantly with age in patients with floaters (TTO: age ≤55 = 0.89, age >55 = 0.89, P = .16; SG [death]: age ≤55 = 0.88, age >55 = 0.90, P = .07). However, patients aged ≤55 years reported lower SG (blindness) utility values when compared with patients >55 years of age (age ≤55 = 0.92, age >55 = 0.94, P = .007).
| Characteristic | n | TTO Mean (Median) | P Value | n | SG (Death) Mean (Median) | P Value | n | SG (Blindness) Mean (Median) | P Value |
|---|---|---|---|---|---|---|---|---|---|
| All | 266 | 0.89 (1.00) | 266 | 0.89 (1.00) | 266 | 0.93 (1.00) | |||
| Age | .16 | .07 | .007 a | ||||||
| ≤55 years | 146 | 0.89 (0.96) | 146 | 0.88 (1) | 146 | 0.92 (1) | |||
| >55 years | 120 | 0.89 (1) | 120 | 0.90 (1) | 120 | 0.94 (1) | |||
| Gender | .52 | .20 | .39 | ||||||
| Male | 117 | 0.89 (1) | 117 | 0.88 (1) | 117 | 0.92 (1) | |||
| Female | 149 | 0.90 (1) | 149 | 0.89 (1) | 149 | 0.94 (1) | |||
| Race | .57 | .26 | .54 | ||||||
| Chinese | 239 | 0.89 (1) | 239 | 0.88 (1) | 239 | 0.93 (1) | |||
| Non-Chinese | 27 | 0.92 (1) | 27 | 0.92 (1) | 27 | 0.92 (1) | |||
| Personal income | .26 | .29 | .65 | ||||||
| No income | 121 | 0.90 (1) | 121 | 0.89 (1) | 121 | 0.93 (1) | |||
| US$ 1–1333.3 | 62 | 0.87 (0.9) | 62 | 0.86 (1) | 62 | 0.94 (1) | |||
| US$ >1333.3 | 83 | 0.90 (1) | 83 | 0.90 (1) | 83 | 0.91 (1) | |||
| Household income | .57 | .77 | .46 | ||||||
| No income | 113 | 0.89 (1) | 113 | 0.88 (1) | 113 | 0.93 (1) | |||
| US$ 1–1333.3 | 78 | 0.89 (0.953) | 78 | 0.90 (1) | 78 | 0.94 (1) | |||
| US$ >1333.3 | 75 | 0.90 (1) | 75 | 0.89 (1) | 75 | 0.92 (1) | |||
| Education | .13 | .93 | .59 | ||||||
| No formal education/primary education | 51 | 0.92 (1) | 51 | 0.87 (1) | 51 | 0.91 (1) | |||
| Secondary education | 119 | 0.87 (1) | 119 | 0.88 (1) | 119 | 0.93 (1) | |||
| Diploma/degree | 95 | 0.90 (1) | 95 | 0.91 (1) | 95 | 0.95 (1) | |||
| Housing type | .44 | .46 | .57 | ||||||
| Public (1–4 room flats) | 120 | 0.88 (1) | 120 | 0.90 (1) | 120 | 0.92 (1) | |||
| Public (>5 room flats) | 95 | 0.89 (1) | 95 | 0.87 (1) | 95 | 0.93 (1) | |||
| Private | 49 | 0.91 (1) | 49 | 0.90 (1) | 49 | 0.96 (1) | |||
| Occupation | .13 | .19 | .48 | ||||||
| Employed/student | 174 | 0.89 (1) | 174 | 0.88 (1) | 174 | 0.93 (1) | |||
| Housewife/retired/non-employed | 90 | 0.90 (1) | 90 | 0.90 (1) | 90 | 0.93 (1) |
The TTO, SG (death), and SG (blindness) utility values did not differ significantly between male and female patients (TTO: male = 0.89, female = 0.90, P = 0.52; SG [death]: male = 0.88, female = 0.89, P = .20; SG [blindness]: male = 0.92, female = 0.94, P = .39).
No significant difference was observed in the utility values between Chinese and non-Chinese patients (TTO: Chinese = 0.89, non-Chinese = 0.92, P = .57; SG [death]: Chinese = 0.88, non-Chinese = 0.92, P = .26; SG [blindness]: Chinese = 0.93, non-Chinese = 0.92, P = .54).
Utility Values and Socioeconomic Variables
A brief summary of the relationship between utility values and socioeconomic variables is shown in Table 2 . Utility values did not demonstrate a significant relationship with any of the socioeconomic variables examined in this study.
Utility Values and Ocular Characteristics
The utility values associated with various ocular characteristics are shown in Table 3 .
| Characteristic | N | TTO Mean (Median) | P Value | N | SG (Death) Mean (Median) | P Value | N | SG (Blindness) Mean (Median) | P Value |
|---|---|---|---|---|---|---|---|---|---|
| Duration of floaters | .34 | .90 | .81 | ||||||
| ≤1 month | 142 | 0.88 (1) | 142 | 0.89 (1) | 142 | 0.93 (1) | |||
| >1 month | 124 | 0.90 (1) | 124 | 0.89 (1) | 124 | 0.93 (1) | |||
| Laterality of presentation | .89 | .36 | .75 | ||||||
| Unilateral | 113 | 0.89 (1) | 113 | 0.89 (1) | 113 | 0.93 (1) | |||
| Bilateral | 153 | 0.90 (1) | 153 | 0.89 (1) | 153 | 0.93 91) | |||
| Myopia | .55 | .26 | .92 | ||||||
| No myopia | 107 | 0.90 (1) | 107 | 0.86 (1) | 107 | 0.91 (1) | |||
| Myopia in at least 1 eye | 159 | 0.89 (1) | 159 | 0.90 (1) | 159 | 0.95 (1) | |||
| Severity of myopia | .41 | .35 | .58 | ||||||
| SE less than −6.0 D | 100 | 0.92 (1.00) | 115 | 0.92 (1.00) | 116 | 0.94 (1.00) | |||
| SE greater than or equal to −6.0 D | 59 | 0.88 (0.96) | 64 | 0.88 (1.00) | 67 | 0.95 (1.00) | |||
| PVD | .79 | .57 | .42 | ||||||
| Absent | 131 | 0.90 (1) | 131 | 0.90 (1) | 131 | 0.93 (1) | |||
| Present | 135 | 0.88 (1) | 135 | 0.88 (1) | 135 | 0.93 (1) |
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