The impact of visual symptoms on the quality of life of patients with early to moderate glaucoma
Young Shin Kim1, Myeong Yeon Yi1, Young Jae Hong2, Ka Hee Park3
1 Department of Ophthalmology, Soonchunhyang University Seoul Hospital, Soonchunhyang University College of Medicine, Seoul, Korea
2 The Glaucoma & Cataract Center of Nune Eye Hospital, Seoul, Korea
3 Department of Ophthalmology, Soonchunhyang University Bucheon Hospital, Soonchunhyang University College of Medicine, Bucheon, Korea
Correspondence to Dr Ka Hee Park
Department of Ophthalmology, Soonchunhyang University Bucheon Hospital, Soonchunhyang University College of Medicine, 170 Jomaru-ro, Wonmi-gu, 420-767, Bucheon, Korea.
Phone: 82-32-621-5428, Fax: 82-32-621-5018, E-mail: ophkh@schmc.ac.kr
Abstract
Purpose: To investigate the visual symptoms and to determine the impact of visual symptoms on vision-related quality of life (QoL) in patients with early to moderate glaucoma.
Methods: A retrospective, hospital-based, cross-sectional study was conducted from July 1 to August 31, 2014, at a university referral center. A total of 176 patients with early to moderate glaucoma underwent a comprehensive ocular examination, including Humphrey visual field testing. The patients were divided into six groups based on visual symptoms that could be verified by forced-choice questions. Vision-related QoL was assessed by the Korean version of the National Eye Institute Visual Function Questionnaire 25 (K-NEI-VFQ-25). We compared the mean deviation (MD) and questionnaire scores among the groups.
Results: Of 352 eyes, 107 (30.4%) were symptomatic. The most common visual symptoms were partial blurring (15.91%), followed by a missing part (7.67%) and a black part (5.97%) of the image. The symptomatic groups (blurred part and missing part) had a significantly worse MD than the asymptomatic group. The symptomatic groups tended to have more visual field defects than the asymptomatic group. The overall NEI VFQ-25 score in the symptomatic group (black part) was significantly lower than that in the asymptomatic group. Similar effects were observed for other subscale scores, including social functioning, mental health, role difficulties, dependency, and peripheral vision.
Conclusions: Vision-related QoL may be severely compromised in glaucoma patients with visual symptoms. Patients with visual disorders should be evaluated for glaucoma and QoL.
Keywords: Glaucoma; Quality of life; Visual symptoms; Visual field
Introduction
Glaucoma usually causes no symptoms until the disease is advanced, with substantial amounts of neural damage [1]. However, patients with glaucoma often complain of vision-related problems, even though they do not have advanced glaucoma or poor visual acuity. Several recent studies examined the visual symptoms of patients with glaucoma and the perception of their visual acuity [2-4]. Crabb et al. [2] reported that 74% of glaucoma patients, excluding those with very advanced disease, were aware of their vision loss.
Patients with subtle vision-related problems should be evaluated for glaucoma because the early or middle stages of glaucoma may cause these symptoms. Moreover, these symptoms can affect the vision-related quality of life (QoL) of patients. Although visual field loss is related to vision-related QoL [5-8], the impact of visual symptoms on the vision-related QoL of glaucoma patients has not been fully elucidated.
This study investigated the subjective visual symptoms of patients with early to moderate glaucoma and evaluated the impact of visual symptoms on the vision-related QoL of these patients.
Materials and methods
Patients
Patients with glaucoma were consecutively recruited at the glaucoma clinic of the Department of Ophthalmology (Nune Eye Hospital, Seoul, South Korea) from July 1 to August 31, 2014. All patients were diagnosed with early or moderate open-angle glaucoma in one or both eyes based on the mean deviation (MD). The eligibility criteria included patients aged 20–50 years, with no cognitive or hearing impairments, and with no other ocular disease that affected their vision (cataract > LOCII grade 2, corneal disease, or retinal disease). Patients with secondary glaucoma or patients who had undergone previous ocular surgery were excluded. Patients > 50 years of age were excluded to avoid the influence of age-related visual and ocular symptoms such as presbyopia, dry eye, and lens opacification.
Patients were examined and questioned during regularly scheduled visits. All patients had a complete review of their medical history and an ocular examination that included a slit lamp examination, gonioscopy, Goldmann applanation tonometry, fundus examination, optical coherence tomography using a Cirrus HD-OCT apparatus (Carl Zeiss Meditec, Dublin, CA, USA), and automated perimetry using a Humphrey Field Analyzer II (Humphrey Instruments, Dublin, CA, USA). The following clinical variables were obtained from the medical records at the same visit: age, sex, type of glaucoma, history of ocular surgery, family history of glaucoma, and MD using a Humphrey Field Analyzer II. This study adhered to the principles of the Declaration of Helsinki and was approved by the Institutional Review Board of the Nune Eye Hospital.
Visual field examination
A Humphrey Field Analyzer II (automated static perimetry) was used to plot visual fields for all patients. Field loss was defined as glaucoma if the glaucoma hemifield test result was outside normal limits and three contiguous points on the pattern deviation plot were < the 5% level in a hemifield of the Humphrey Field Analyzer according to the Swedish Interactive Threshold Algorithm standard 30-2 program. Poor tests with high fixation losses exceeding 20% or false-positive/-negative values exceeding 33% were excluded from the analyses. To analyze the relationship between the reported symptoms and the severity of glaucoma field defects, the MDs of the Humphrey Field Analyzer were compared and the patients were divided into four groups based on the visual field defect from the central fixation point to the peripheral side based on the degree of deviation: < 6°, 6–18°, 18–30°, and no defect.
Symptom awareness questionnaire
One-on-one interviews were conducted by a single investigator (K.H.P.). The questionnaire asked open-ended questions about the visual symptoms that patients experienced in daily life and forced-choice questions that required subjects to select the image that most closely represented their perception of their visual field loss (Appendix 1). The patients were divided into six groups based on visual symptoms that could be verified by a forced-choice question: blurred part, missing part, black part, blurred tunnel vision, black tunnel vision, and other (Appendix 2).2 One additional question was asked concerning the fixing eye.
The National Eye Institute (NEI) Visual Function Questionnaire 25
The Korean version of the NEI Visual Function Questionnaire 25 (K-NEI-VFQ-25) was used to evaluate vision-related QoL. The Korean version has been reported to significantly correlate with the original NEI-VFQ-25, a vision-related QoL questionnaire for patients [9-10]. It is comprised of 25 questions with additional questions grouped into 12 subscales: general health, general vision, ocular pain, near activities, distance activities, social functioning, mental health, role difficulties, dependency, driving, color vision, and peripheral vision. NEI guidelines were followed in calculating the scale conversions and subscale scores. Higher K-NEI-VFQ-25 scores indicate a better QoL and less vision-related impairment.
Statistical analysis
Statistical analyses were performed using SPSS statistical software for Windows, version 21.0 (SPSS, Chicago, IL, USA). Responses to the forced-choice questions were counted and compared using statistics for proportions. Summary statistics for the MD and scores on the K-NEI-VFQ-25 were calculated and compared for patient groups choosing a particular image. Tests involving each group were conducted, except for the black and blurred tunnel groups, which had a small sample size. Demographic variables among the groups were analyzed using a one-way ANOVA, the Kruskal-Wallis test for continuous variables, and the chi-square test or Fisher’s exact test for categorical variables. The MDs and scores among groups were analyzed using a one-way ANOVA or the Kruskal-Wallis test with Bonferroni’s post hoc comparison. The chi-square test was used to compare field defect points among groups. A value of P < 0.05 was considered statistically significant.
Results
Of 176 patients included in the study (67 females), 102 were diagnosed with normal-tension glaucoma, 61 were diagnosed with primary open-angle glaucoma, and 13 patients were diagnosed with low-tension glaucoma. The mean age ± standard deviation was 39.85 ± 8.27 years. The best-corrected visual acuities of the better and worse eyes were 0.96 ± 0.10 and 0.95 ± 0.13, respectively. The refractive errors of the better and worse eyes were -4.00 ± 3.03 diopters (D) and -4.26 ± 3.17 D, respectively. The common descriptors of subjective visual symptoms reported in the open-end questionnaire were blurred vision (14 patients), missing vision (10 patients), foggy vision (8 patients), unfocused vision (8 patients), dark and dim vision (7 patients), and unclear vision (5 patients). No patient complained of tunnel vision.
The results of the forced-choice questions were as follows. Of 352 eyes, 245 (69.6%) were asymptomatic. The most common visual symptom was a blurred part (56 eyes, 15.91%), followed by a missing part (27 eyes, 7.67%), and a black part (21 eyes, 5.97%). Only two eyes and one eye selected the images with a black tunnel (0.57%) and a blurred tunnel (0.28%), respectively. The black and blurred tunnel groups were excluded from the statistical analyses because of their small sample size. The patients’ characteristics are summarized in Table 1.
Comparison of the MDs and visual field defects among the groups
The average MDs of the fixing, non-fixing, better, and worse eyes were significantly different among the groups. A post hoc comparison showed significant differences between the asymptomatic and symptomatic groups (blurred part and missing part, respectively) in the fixing eye and better eye. The symptomatic groups had a significant worse MD than the asymptomatic group. Table 2 shows comparisons using the Humphrey Visual Field Analyzer to determine the MD of different groups.
A comparison of the visual field defects showed significant differences among the groups in the fixing eye, non-fixing eye, better eye, and worse eye. A post hoc comparison showed significant differences between the asymptomatic and symptomatic groups (Table 3). The symptomatic groups tended to have greater visual field defects than the asymptomatic group.
Comparison of the K-NEI-VFQ-25 composite scores among groups
General health and general vision were relatively low in all patients with early or moderate glaucoma. A post hoc comparison showed significant differences between the asymptomatic and symptomatic groups (black part) in the overall K-NEI-VFQ-25 score. Similar effects were observed for other subscale scores, including social functioning, mental health, role difficulties, dependency, and peripheral vision (Table 4).
Discussion
We identified subjective visual symptoms of patients with early to moderate glaucoma. Approximately 30% of the patients were aware of subjective visual symptoms; the most common visual symptoms were blurring of the visual field, followed by a missing part and a black part. When investigating the impact of visual symptoms on the vision-related QoL in patients with early to moderate glaucoma, the overall K-NEI-VFQ-25 score in the symptomatic groups was significantly lower than that in the asymptomatic groups. Moreover, visual symptoms negatively affected important activities such as social functioning, mental health, role difficulties, dependency, and peripheral vision.
The subjective perception of vision loss in patients with glaucoma has been previously reported [2-4]. Crabb et al. [2] reported that 74% of glaucoma patients excluding those with very advanced disease were aware of their vision loss, with the most frequently used descriptors of a visual field defect being missing vision and blurred vision. Hu et al. [3] reported that the most common symptom of all patients, including patients with early or moderate glaucoma, was the need for more light and blurred vision. The present study shows similar findings, with differing patient percentages, perhaps reflecting the exclusivity of subjects with early or moderate glaucoma.
Comparison of the MDs and visual field defects among the groups
Hu et al. [3] reported that the visual symptoms of patients with early to moderate glaucoma were not associated with any specific area of visual field defects. However, several studies reported that a central visual field defect affects visual acuity and visual field sensitivity [11], and that retinal sensitivity of the better eye in the lower hemifield within 5° of fixation was the most important parameter in vision-related QoL [5,6,12]. In the present study, the MD of the symptomatic group was significantly lower than that of the asymptomatic group. Moreover, the central visual function correlated more closely with subjective visual symptoms, implying that the chance of experiencing symptoms was higher as the functional field of view became narrower. Identifying the locations of visual field defects with the more clustered classification may provide a better understanding of the relationship between visual symptoms and visual field loss.
Comparison of K-NEI-VFQ-25 composite scores among the groups
Recent studies have reported that the QoL of glaucoma patients decreases with the severity of the disease [12-14]. The current study emphasizes the clinical significance of visual symptoms in vision-related QoL. The overall K-NEI-VFQ-25 score and other subscale scores were significantly lower in the symptomatic group (black part) than in the asymptomatic group. This result is similar to a previous study reporting that the concerns of glaucoma patients were primarily associated with an increased awareness of the vulnerability of central vision as the disease progressed, and not with the consequences of the visual field loss that characterized the disease [11].
Even mild or moderate glaucomatous vision loss is associated with significant visual disability and reduced ability to perform visually related tasks such as reading or driving [15,16]. Takahashi et al. [17] reported that the NEI VFQ-25 subscales were correlated with subjective symptoms perceived by patients while driving. In this study, visual symptoms negatively affected activities such as social functioning, mental health, role difficulties, dependency, and peripheral vision.
A limitation of our study was the difficulty in including all aspects of visual function that were important from a patient’s perspective. Second, we studied the visual field in the better eye and worse eye separately, but not binocularly. Previous studies reported that monocular visual fields overestimate vision loss compared with binocular integrated visual fields [18,19]. In a recent study, binocular visual field tests results correlated better with scores from the relevant subscales of the NEI VFQ-25 than binocular approximations based on monocular measures [20]. Thus, more conclusive results might be obtained if binocular visual field test could be included in future studies. However, considering that visual field tests are performed unilaterally in a clinical setting, our results highlight the importance of understanding the relation between visual field tests and binocular symptoms. Third, most of the participants were literate and from urban areas, so our findings may not be representative of the overall population. Lastly, other potential factors that have been reported to be compromised in glaucoma were not evaluated, including stereopsis, dark adaptation, and color vision.
However, a strength of our study is the inclusion of participants of a relatively young age who could clearly communicate their symptoms and express their complaints. In this manner, visual symptoms irrelevant to glaucoma or potentially caused by other factors such as age could be excluded. The use of images to express the patients’ symptoms and clarify whether a complaint was related to glaucoma is another strength of this study.
This study identified subjective symptoms of glaucoma that usually go unnoticed in clinical practice, and it shows that patients with glaucoma experience various visual symptoms rather than black tunnel vision. Physicians should be reminded that patients with subtle visual discomfort should be evaluated for glaucoma because the early or middle stages of glaucoma may cause these symptoms. Furthermore, physicians should consider whether these symptoms are a sign of disease progression. Such changes in recognition may help strengthen doctor-patient relationships in the context of chronic diseases such as glaucoma.