Visual impairment, when sufficiently severe, is apparent to persons with glaucoma during all waking moments, and the effects of living with this impairment throughout the day can exert a profound physical and psychological toll on the individual. For those without glaucoma, the impact of the disease can be hard to comprehend, though it is important for several groups to do so, particularly physicians who care for glaucoma patients, but also patient support groups, companies/manufacturers of glaucoma-related technologies, government associations, and policy makers who direct funding toward the care of glaucoma, and rehabilitation specialists who may be called upon to help glaucoma patients.
Physicians caring for glaucoma can benefit most from a detailed understanding the impact of glaucoma on the individual, and this benefit accrues for several reasons. First, understanding the numerous ways that glaucoma damage affects the individual brings us closer to the struggles and difficulties they encounter in their daily lives, allowing us to better relate to the trouble they have from their disease, and ultimately allowing us to adopt a more empathetic attitude and facilitating better communication. Second, the primary goal of glaucoma treatment is to maintain the patient’s visual function and related quality of life (QOL) at a sustainable cost, making it important to understand how QOL is likely to be affected by glaucoma at various stages of disease. Third, understanding when and how glaucoma affects our patients helps remind us of the difficulties they face, and can help us motivate them to seek appropriate services to rehabilitate themselves and/or protect themselves against dangers such as falls or motor vehicle accidents (MVAs). Fourth, for those involved in research, understanding the specifics regarding how to capture disability in glaucoma can help guide the integration of more patient-centric measures into studies of glaucoma treatment, thus informing us whether our treatments are not only successful at meeting clinical endpoints such as intraocular pressure lowering, but also at improving the lives of our patients using measures more tangible to them. Finally, those of us caring for glaucoma patients are the primary ambassadors responsible for securing funds to adequately detect the disease, provide requisite treatments to those with known glaucoma, and develop new strategies for disease detection, treatment, and rehabilitation. Understanding the impact of glaucoma on the person gives us hard data to use as we advocate for these causes with insurers, policy makers, and funding agencies.
METHODS FOR BEST CAPTURING GLAUCOMA-RELATED DISABILITY
The broad and far-reaching consequences of vision loss frequently raise the question about how to best analyze the impact of glaucoma on the person. Ultimately, there is no single “best” method for capturing glaucoma-related disability. To most fully paint a picture of what disability in glaucoma is like, a broad range of techniques must be used.
Table 1 describes the strengths and limitations of the various methods for describing glaucoma-related disability, examples of the specific measures, and instruments within each method. Table 2 and Figure 1 focus on the impact of glaucoma on reading, driving, and mobility as judged by various methods to capture disability. In the sections below, each methodology is discussed in detail, and findings from studies utilizing these methodologies are highlighted.
MEDLINE, EMBASE, and SCOPUS were systematically searched from December 2017 to May 2018 to identify relevant articles. For each database, a search strategy was used using the keywords “glaucoma” combined with: “quality of life,” “reading,” “driving,” “mobility,” “employment,” “facial recognition,” “prehension,” “caregiver,” “utility,” “falls,” “depression,” “cost,” or “economics.” Selected articles were published in English and ranged from studies describing or evaluating qualitative instruments to observational and randomized clinical trials measuring areas of disability in glaucoma patients.
QUALITATIVE DESCRIPTIONS OF HOW GLAUCOMA AFFECTS THE INDIVIDUAL
Qualitative descriptions typically take the form of patient interviews, focus groups, and open-ended questionnaires, and are well suited for providing a compelling description of how persons with glaucoma are affected by their visual loss. For instance, Glen and Crabb, utilizing semistructured interviews presented several compelling descriptions associated with glaucoma, such as “I’m reading less because I find it’s quite hard to concentrate for long periods,” or “if you drop something, you can’t actually see it.”64 In other work aimed to describe what the world looks like with glaucoma, patients selected a digitally modified photograph that most closely represented their perception of visual field (VF) loss and showed that glaucoma patients do not perceive VF loss as a black tunnel effect or as black patches obstructing their vision but more so as blurred patches of vision or missing patches of vision.65
Mixed-method approaches where qualitative and quantitative methods are combined can be used to collate qualitative data to describe the types of complaints most common among glaucoma patients, and/or divide these complaints into domains that represent distinct ways that glaucoma affects the individual from the patient’s perspective, which are themselves instructive. Multiple studies utilizing focus groups have highlighted that difficulty with lighting (glare, adapting to different lighting levels) is perhaps the most common problem among patients with glaucoma, while mobility-related complaints (walking, stair climbing, driving, etc.) are also quite common.1–4 Reading complaints are also surprisingly common despite the perception of glaucoma as a disease of peripheral vision.1,3 In a systematic study integrating focus groups and a literature review of previous patient-reported outcomes in glaucoma, Khadka et al identified 10 distinct domains of importance, several of which are related to the burden of care (visual symptoms, ocular surface symptoms, general symptoms). The remainder reflects task difficulty and the psychological implications of the disease.5 Similarly, Matsuura and colleagues66 generated 7 distinct domains, with approximately half of the domains measuring functional difficulties (reading/writing, walking, going out, eating, and driving) and the remaining domains capturing the psychosocial aspects of disease (worry/anxiety, social participation, and physical symptoms).6 These questionnaires illustrate the wide-ranging consequences of glaucoma, though an argument might be made that most of these consequences start with activity difficulty/limitation as well as fear of what the disease will bring in the future.
The qualitative and mixed-methods approaches above typically are used to produce “quality of life” questionnaires, which in turn capture what the patient is experiencing. Previous work has extensively reviewed existing questionnaires to gauge QOL in glaucoma, and provided extensive guidelines regarding how the quality of questionnaires can be assessed, and which are most appropriate for including in studies. Our review of questionnaires will be more limited here, mostly focusing on the content that these questionnaires cover (or do not cover), and to what extent they do or do not capture the disability resulting from glaucoma.67,68
Of note, while the term “quality of life” is often used, questionnaires often focus on perceived task difficulty which, is as illustrated above, is only 1 aspect of a worthwhile life. When these questionnaires are derived specifically from glaucoma patients, the result is typically a glaucoma-specific questionnaire. Some examples include: (1) Glaucoma-Quality of Life-15 (GQL-15); (2) Glaucoma Activity Limitation (GAL-9); (3) Glaucoma Symptom Scale (GSS) questionnaire; (4) Symptom Impact Glaucoma Score (SIG); and (5) Glaucoma Health Perception Index (GHPI).7,8,69,70 Such questionnaires are designed to closely parallel the level of glaucoma damage, and are most useful in determining the specific types of visual loss associated with disability. The GQL-15, in particular, has been shown to distinguish mild VF loss from moderate-severe VF loss and is significantly correlated with perimetric testing and Estermann VF scores.7 However, the majority of studies utilizing these instruments have simply confirmed that disability is greater with greater levels of VF damage, a finding that is expected given that the questions were derived to reflect the problems encountered by persons with glaucoma.2,8–13
A more clinically meaningful use of these instruments may be to investigate how treatments (medical or rehabilitative) affect glaucoma-related disability. For example, the Collaborative Initial Glaucoma Treatment Study (CIGTS) compared QOL in medically versus surgically treated glaucoma patients with precursor forms of the SIG/GHPI questionnaires.8 However, the use of these questionnaires with regard to treatment has been limited. Another useful application of glaucoma-specific instruments may be to investigate whether the location of VF loss affects the degree of disability experienced by patients. Previous studies utilizing vision-specific questionnaires have indicated that vision loss in the central and inferior fields may have a greater impact on QOL than vision loss in the peripheral and superior fields.71–73 A similar analysis performed with glaucoma-specific questionnaires (GSQ) may provide additional insights on the effects of the location of VF loss on disability.
One limitation of most glaucoma-specific instruments is that they typically do not span the multiple domains discussed in the previous section, that is, issues regarding convenience, economics, etc. Indeed, a detailed examination of the questions asked within such questionnaires suggests that they focus on a specific aspect of glaucoma disability, that is, difficulty with daily activities. Future questionnaires, if they are to be comprehensive, will need to span the multiple domains which explain how glaucoma affects the person, and should have sufficient questions within each domain to accurately determine the level of disability within these domains. Indeed, such an approach has been shown for patients with diabetic retinopathy and is currently also underway for persons with glaucoma.74
Vision-specific questionnaires (not specifically designed for glaucoma) have also been used to gauge the impact of glaucoma in several studies. In particular, the National Eye Institute Visual Function Questionnaires (NEI-VFQs) has been widely used in glaucoma research.4,75 The items of the NEI-VFQ were identified using condition-specific focus groups comprised of individuals with glaucoma, diabetic retinopathy, macular degeneration, cytomegalovirus retinitis, cataract, and low vision.4 One study found that glaucoma patients scored lower than normally sighted control subjects in most of the tested domains of the NEI-VFQ.14 Several randomized clinical trials have used the NEI-VFQ, notably the Early Manifest Glaucoma Trial which showed that NEI-VFQ scores correlated with low visual acuity in the better eye, worse perimetric mean deviation (MD), and nuclear lens opacity. The Early Manifest Glaucoma Trial also showed that the absence or delay of treatment does not influence vision-related QOL, though these findings may reflect that studied patients had early stages of glaucoma and that only 1 eye was randomized as part of the study.76
While the initial papers describing vision-specific questionnaires utilized a Likert scaling to yield a single number representing QOL, subsequent work has showed that not all items reflect the same underlying construct, though Rasch analysis is possible when selecting out those items that primarily focus on task difficulty, and omitting items regarding the psychological/treatment portions of the questionnaire.77,78 One limitation with questionnaires not specifically designed to capture the effects of VF/contrast sensitivity loss (the major visual measures affected by glaucoma), is that it may be less sensitive to changes in these aspects of visual damage as compared with GSQ. In contrast, an advantage over GSQ is that vision-specific questionnaires allow comparison of results to studies assessing other eye diseases. For example, a systematic review of studies measuring vision-related QOL in glaucoma and age-related macular degeneration showed that glaucoma patients generally scored lower in the general health and mental health domains peripheral vision domains, whereas age-related macular degeneration patients scored lower in the near activities and driving domains.79
GENERAL HEALTH QUESTIOINNAIRES
Several groups have used general health questionnaires such as the Medical Outcomes Study Short Form (SF-36)80 and the EuroQOL-5D (EQ-5D)81 to investigate the relationship between glaucoma and glaucoma severity with overall quality of life. Studies utilizing the SF-36 have showed mixed results with some groups showing worse quality of life with glaucoma-related damage and other studies showing no significant association.15,82–84 Of note, the EAGLE study (effectiveness of early lens extraction for the treatment of primary angle-closure glaucoma) used the EQ-5D to compare treatment outcomes in primary angle-closure patients undergoing cataract extraction versus laser iridotomy and, when required, medications.85 Statistically significant group differences in [INCREMENT]EQ-5D scores were noted, despite the fact that degree of VF damage has not consistently been associated with EQ-5D scores in the past.16 Notably, glaucoma patients undergoing clear-lens extraction had higher final EQ-5D scores than glaucoma patients undergoing standard care with laser iridotomy and topical medications, suggesting that some general health measures may be useful in specific studies even when not associated with the degree of VF damage.16 A significant advantage of using a general health questionnaire is that several funding agencies often make decisions based on these questionnaires. In addition, the use of such a questionnaire allows one to benchmark the degree of impairment attributable to glaucoma and/or glaucoma treatment to the impairment attributable to other diseases and disease treatments.
DOMAIN-SPECIFIC QUESTIONNAIRRES (DSQs)
DSQs focus on specific tasks or activities such as driving or reading, and can provide highly detailed information about how a disease process impacts a specific area of disability. Driving habits questionnaires have been used, for example, to show that glaucoma patients have more driving limitations and are more likely to have stopped driving than glaucoma suspects and age-matched controls.17–19 Similarly, several groups have shown that glaucoma patients report greater reading difficulty with a variety of tasks, particularly those involving sustained reading such as reading a book, than glaucoma suspects.1,3,20,21 DSQs can also provide insights into how patients adapt their behavior in response to disability. For instance, studies have showed that glaucoma patients with reported difficulty driving often self-regulate their driving habits to avoid potentially difficult driving situations such as driving at night, on freeways, and in unfamiliar areas.18,19,22–24
DSQs can also be used to benchmark the impact of glaucoma on areas of disability that are shared across other diseases. For example, several groups have showed greater fear of falling with greater levels of VF damage.25,26 Given that fear of falling is common to a broad array of diseases, and to the aging process itself, study results can be compared to assess the relative degree of fear of falling resulting from VF damage as compared with other conditions, thus benchmarking the impact of glaucoma, at least with regard to this specific disease impact.
OBJECTIVE MEASURES OF FUNCTION
Functional tests focus on the objective quantification of ability with regard to daily tasks or surrogate tasks relevant to independent living and/or health outcomes. Functional testing provides objective data which can buttress the subjective information derived from questionnaires. Quantitative data derived through objective testing also provides data which are typically more easily understood than questionnaire results. For example, documenting the degree to which glaucoma patients read slower, make infractions while driving, or walk differently than persons without glaucoma provides numbers which are more easily interpreted than numbers obtained through self-report. Finally, objective testing is generally more capable of illustrating the specific reasons behind disability. For example, eye movement patterns could, potentially, explain why some patients with glaucoma read slower, gait patterns might explain the reasons for falls, and driving patterns may explain the reasons behind higher accident rates. These insights can, in turn, guide potential approaches to addressing disability. In the following examples, we highlight key areas of glaucoma disability for which objective measures of function have been developed.
Difficulty with reading is one of the most frequent complaints among glaucoma patients and is an ideal area for objective testing given the large amount of work done to generate and validate tests of reading in persons with impaired vision.1,21,86 Studies evaluating spoken reading speed in glaucoma have shown associations between greater VF damage and slower reading speeds,27–29 though one study suggested that significant slowing only occurs in persons with severe bilateral VF damage.29 Silent reading speed in glaucoma has also been evaluated in 2 studies, with one finding no association between severity of VF damage and silent reading speed,87 and a second study showing a substantial decrement in silent reading speed with greater VF damage.28 In the latter study, VF damage had a greater impact on silent reading than spoken reading speed.28 Reading difficulty associated with glaucoma may also have implications on reading comprehension as one study showed a trend toward lower reading comprehension in glaucoma patients than controls.28 This difficulty with comprehension may be because glaucoma patients choose to guess the identity of words more frequently in an attempt to maintain their reading speed.88 Guessing may be more difficult for less frequently used words, and indeed such words are read disproportionately slower in patients with more severe VF damage.88
What are the reasons behind reading difficulty in glaucoma? Visual span (the number of letters of text one can read in a single fixation) may play an important role as glaucoma patients have smaller visual spans due to VF loss, and smaller visual span is associated with slower reading speeds.89 Consistent with these findings, patients with glaucoma are particularly slower in reciting longer words where more fixations would be necessary.88 An important aspect of reading is also searching, and glaucoma patients with greater VF damage are slower in finding the next line of text88 and searching for specific content within a large body of text (ie, finding a specific item in phone book).90 They are also slower with text-based searching,90 likely because they have to fixate multiple times to properly identify words due to a reduced visual span.87,89 Glaucoma patients with bilateral VF loss perform more saccades and fixations for a given line of text and spend more time at each fixation point than normal-sighted controls, suggesting that searching, and to some extent reading itself, is slower because of a more imperfect search algorithm as well as greater time required to identify the object of fixation.87,91,92
Persons with glaucoma walk slower, and walking speeds are correlated with VF loss severity.30–32 In addition, glaucoma patients experience more bumps and/or stumbles while walking than controls.30,31 In a large cohort of glaucoma patients evaluated with a gait mat system, greater VF damage was associated with a wider base of support and greater stride-to-stride variability, both of which have been associated with higher rates of falls in older populations.32 Further work is needed to determine to what extent these gait abnormalities account for self-reported mobility difficulty and fall risk associated with glaucoma, and to what extent these abnormalities may be healthy adaptations to lower the risk of falls.
Several studies have shown that glaucoma patients experience greater sway or have worse postural stability under conditions in which proprioceptive input is reduced (ie, standing on foam surface) compared with normal-sighted individuals.33–35 In addition, glaucoma patients also demonstrate greater postural sway on firm surfaces, which may be more representative of conditions encountered in daily life.36,37 Glaucoma patients also had worse balance when presenting peripheral stimuli using virtual reality goggles, a condition which may have particular relevance to falls.38
Glaucoma patients with more advanced VF loss or worse contrast sensitivity have greater difficulty distinguishing faces than patients with early and moderate VF loss and age-matched controls.39 Among glaucoma patients with bilateral central VF loss, better facial recognition performance was associated with larger saccades, suggesting that eye movement patterns may be a method glaucoma patients use adapt to VF loss.93 Impairment of facial recognition may account for decreased social engagement and reduced QOL that have been noted in previous studies.
Glaucoma patients, as compared with normally sighted controls, demonstrate more significant delays in movement onset and overall movement time when performing reach and grab tasks.40
Studies utilizing driving simulators have yielded mixed results regarding the association between glaucoma and accidents in a simulated environment. Three studies found no additional accidents in the simulated environment among patients with glaucoma,63,94,95 though one study did note that glaucoma patients were less likely to detect peripheral stimuli when driving.63 One study showed more accidents among glaucoma patients as compared with controls, or with greater degrees of VF damage.96 Nearly all studies using a driving simulator noted that glaucoma patients demonstrated more compensatory behaviors such as applying greater steering input and performing more head and gaze movements toward eccentric regions.63,94,96,97
In contrast, most studies measuring on-road driving ability showed that glaucoma patients have worse-driving performance.41–43 In these studies, driving was assessed using an in-vehicle driving instructor, and glaucoma patients were rated by instructors to be significantly less safe, made more driving errors, and were 2 to 6 times more likely to experience an intervention from the driving the instructor than controls.41–43 Similar to observations from driving simulators, glaucoma patients tended to alter their driving behaviors with increased head movement and greater visual scanning.41–43 Differences between simulator and on-road driving studies may reflect differences in lighting, required field of view, or other factors not completely captured by simulator environments. However, unlike driving simulators, on-road studies cannot recreate the dangerous situations where accidents are more likely.
Rare events such as falls, fractures, or MVAs can severely threaten the health and well-being of patients, but are unlikely to be recognized as threats by the patient, or to affect their QOL, until they have robbed them of their health. As such, it is important to identify persons at high risk of such events, and to develop strategies to minimize such events (ie, through appropriate driving standards or fall prevention strategies).
Numerous population-based studies have showed that older adults with glaucoma are at increased risk of falling and that this risk increases with greater visual impairment.44–52 Recent studies have more specifically found that a rapid rate of VF loss is a risk factor for more frequent falls, and a prospective study of identified VF loss in the inferior region as a risk factor.50,98 A second study examining falls prospectively found that individuals with glaucoma most commonly fall in or near the home and fall most commonly because of trips, slips, and uneven flooring.53 Although few methods have been proposed to reduce fall risk in glaucoma, recent work has indicated that the home environment is a particularly likely location for falls,53 and home modification may be a viable approach given that persons with glaucoma do not appear to modify their homes for safety.99
Among Medicare beneficiaries, glaucoma patients with VF loss were more likely to experience a femur fracture than glaucoma patients without VF loss.54 In another study, persons with more severe glaucoma experienced a higher percentage of fracture (of any type) after a fall than those with mild and moderate severity.53 Similarly, in a study conducted in a cohort of older women, bilateral VF loss was an independent risk factor for fracture,48 whereas the population-based Beaver Dam study found that the presence of VF loss doubled a participant’s risk of both falls and hip fractures.51
Most, though not all, previous studies have suggested that drivers with glaucoma are at increased risk of MVAs.23,55–58 In one population-based study, drivers with glaucoma had a 65% higher risk of at-fault motor vehicle collision and this risk increased with VF loss severity, with a 111% higher risk noted for individuals with severe VF loss.56 Higher crash rates were also noted in additional studies performed in Alabama, one of the few states that does not require a vision examination for renewal of licensure, such that individuals with glaucoma may be more likely to continue driving.100,101 In contrast, some studies have suggested that drivers with glaucoma do not have an increased risk of MVA, with 1 study even showing a lower risk of MVA than normally sighted individuals, possibly because drivers with glaucoma tend to self-regulate their driving behavior (or are forced off the road by state laws) such that their risk of MVA is reduced to the level of normal-sighted drivers.23,58
The behavior of patients in the real world, either by self-report or objective measurement, also provides compelling data to describe the degree of disability in glaucoma. Examples include self-report to describe driving patterns (if driving) or driving cessation, accelerometers to describe physical activity patterns, and wearable GPS trackers to define real-world travel patterns. Data from these measures are particularly compelling as they describe how patients alter relevant behaviors which in turn can lead to a loss of independence (as with driving), social isolation (as with travel outside the home) or worse health (as with physical activity restriction).
In addition to slower reading, glaucoma patients have been noted to describe more difficulty reading, and also restrict their reading, with one study showing 18% fewer days in which book reading occurred and 10% fewer days in which newspaper reading occurred for each 5 dB decrement in VF MD.20
Persons with glaucoma exhibit lower levels of physical activity at greater levels of VF damage, with advanced glaucoma subjects in one study showing severe restrictions in physical activity (one third as much moderate-vigorous physical activity as normally sighted controls).59 Similarly, in a nationally representative sample of older adults studied within the National Health and Nutrition Examination Survey (NHANES), subjects with bilateral any-cause VF loss took 17% fewer steps per day and engaged in 30% less accelerometer-measured moderate/vigorous physical activity than subjects with normal VFs after accounting for numerous demographic and health variables.60
Leaving the Home
Individuals with glaucoma, particularly those with greater VF loss, are more homebound and travel away from the home less than individuals with normal vision.61 Glaucoma treatment may play a role in this outcome as well, as patients using an alpha agonist were over 4 times as likely to not leave their home on a given day. When glaucoma patients do leave their home, their distance traveled relative to the home location is not restricted, though average excursion size is only 5 miles, suggesting that treatments requiring a long distance of travel place a large burden on the patient, asking them to travel much further than they typically do.60
As a result of perceived difficulty with vision and/or local driving regulations, individuals with glaucoma may regulate or even stop driving. In the Salisbury Eye Evaluation, participants with bilateral glaucoma were almost 3 times as likely to have stopped driving as individuals without glaucoma.17 Unilateral glaucoma was associated with higher rates of incident driving cessation.17 Glaucoma was also more frequently associated with driving cessation in the Blue Mountains Eye Study62 as well as a clinic-based population of patients with either manifest or suspect glaucoma in which each 5 dB decrement in MD doubled the odds of driving cessation.18 In the latter study, patients who continued to drive limited/modified their driving behavior, and were less likely to drive in the rain and at night.18
Depression and Anxiety
Numerous population-based studies have showed an association between glaucoma and symptoms suggesting either depression and/or anxiety.102–107 In an NHANES sample, glaucoma was significantly associated with symptoms of depression after adjustment for demographic factors,106 and in another large study, glaucoma patients were 10.6 times and 12.3 times more likely to have depression and anxiety symptoms, respectively.102
Among glaucoma patients, several studies found that younger age, female sex, and greater economic burden were significant risk factors for symptoms of anxiety,107,108 while older age, unmarried status, greater disease severity, and increased medical comorbidity were significant risk factors for depression symptoms.105,107–109 In addition, longer disease duration and faster VF progression have both been associated with depressive symptoms as well.108,110 Although no clear evidence has linked the severity of glaucoma damage to symptoms of depression or anxiety, greater depressive symptoms have been noted in persons with worse self-reported ability in visual tasks.106,108 Furthermore, one study in a Chinese population found a higher prevalence of depression and anxiety in primary angle closure glaucoma patients as opposed to primary open angle glaucoma (POAG) patients.111 Depressive symptoms may also negatively affect treatment outcomes as they have been associated with decreased medication adherence.112
As severity of VF loss worsens, individuals with glaucoma become increasingly reliant on others for care and activities of daily living, placing a heavy burden on caregivers and family members. Several studies have showed that caregivers of visually impaired patients experience substantial burden of care defined as physical, financial, psychological, and social discomfort/pressures from being the sole caregiver and these caregivers themselves are at higher risk of developing depressive symptoms.113–115 Several articles have showed a substantial caregiver burden for persons with all-cause poor vision, and that burden increases with the degree of impairment.114,115 Fewer studies have specifically assessed caregiver burden in glaucoma patients, though evidence for such burden exists. Of note, one study found that support systems for glaucoma patients have very little understanding of glaucoma and its implications on vision, and are typically minimally involved in a patient’s glaucoma care even though many express an interest in learning about glaucoma and becoming involved in the patients’ care.116 This suggests that disability due to glaucoma may be less recognized by family and friends, such that potential support systems are underutilized.
Glaucoma exerts a large economic burden on individuals and society.117–119 In 2004, the direct medical costs of glaucoma which include medications, clinic visits, and glaucoma-related procedures and surgeries were estimated to be 2.9 billion dollars in the United States.118 This estimate has likely increased in recent years due to newer, more expensive medications and more patients receiving treatment. Similar trends of high economic burden from glaucoma have been observed in Australia, UK, and parts of Europe.117,118 A Markov model populated with data based on US Medicare claims data from 1999 to 2005 estimated that the lifetime cost of care for individuals with POAG was $1688 higher than that individuals without POAG.120 In many studies, the cost of medications is the largest contributor to direct costs of treating glaucoma.117,121,122
Although most studies investigating the financial burden of glaucoma have focused on direct costs, indirect costs such as institutionalization, loss of productivity, and dependence on caregivers/family members comprise a large proportion of the overall cost of glaucoma, particularly in later stages of disease.117 In a European study, the estimated average annual direct cost of glaucoma-related blindness was between €429 and €523 per patient while the estimated total annual costs, including rehabilitation and costs to families, was between €11,758 and €19,111.123 In another European study of glaucoma-related costs among patients with late-stage disease, the largest contributor to total annual costs was assistance in the home, ranging from €633 in Germany to €4878 in France.124 In a Markov model exploring the cost of glaucoma treatment in a French population, the social costs of glaucoma including institutionalization and social allowances were 3 to 4 times higher than medical costs.125 Further work is needed to quantify costs of institutionalization secondary to glaucoma-related blindness and the impact of comorbid conditions, and to compare these costs with the direct costs of treatment.
Several studies have showed that the financial burden of glaucoma increases as disease severity increases. One study found that as glaucoma severity increased from suspect status/early-stage disease to end-stage disease, direct ophthalmology-related costs (clinic visits, medications, and glaucoma surgeries) increased 4-fold from $623 to $2511.121 Similarly, a European study found that annual direct costs of treatment increased by €86 for each incremental increase in glaucoma stage, ranging from €455 for ocular hypertension and €969 for severe glaucoma.122 In a study of Medicare beneficiaries with glaucoma, individuals with any degree of VF loss had 46.7% higher total costs than individuals without vision loss, and total cost increased with VF loss severity.120 In this same study, individuals with VF loss were more likely to be placed in a nursing home, develop depression, sustain a femur fracture, and experience a fall or accident than individuals with no vision loss, providing likely reasons for increased total costs among individuals with greater vision loss.120 It has also been shown that greater costs are associated with higher initial intraocular pressure level and higher baseline glaucoma stage.126,127
Of note, many of the ophthalmic costs associated with treating glaucoma patients may result in costs from other concurrent diseases, making it important to specifically analyze costs due to glaucoma-related treatment.128 Furthermore, no previous work has examined the relationship of glaucoma and employment, though this is an important area of study, and a broad literature has suggested that individuals with visual impairment defined through acuity measures are less likely to be employed and earn less when employed.118,128
A wide variety of research tools have been used to characterize disability resulting from glaucoma. While no single questionnaire or test can fully capture disability resulting from glaucoma, together these tools show that glaucoma affects many abilities which are important for independent living. The strengths and limitations of the various research techniques are discussed so that future studies may use the method(s) most suitable for answering the research question posed.
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