Presenting visual impairment and associated factors among patients with glaucoma in Hawassa, Ethiopia 2022
Article information
Abstract
Visual impairment due to glaucoma is irreversible; therefore, understanding its burden is important for implementing appropriate preventive measures. This study aimed to estimate the prevalence of visual impairment in patients with glaucoma. A hospital-based cross-sectional study was conducted on patients with glaucoma attending Hawassa University Comprehensive Specialized Hospital from May 1, 2022 to November 30, 2022. Visual acuity of 383 glaucomatous eyes from 275 patients was assessed using the Snellen illiterate acuity chart. Visual acuity at presentation and previous diagnoses were reviewed from the patient’s medical charts during the current checkup. Objective and subjective refractive measurements were performed for patients with a visual acuity of 6/18 or worse. Data collected using a validated structured questionnaire were cleaned, imported into Epinfo, and then exported to SPSS ver. 22. Descriptive and binary logistic regression analyses were conducted. Cofactors with a P<0.05 were considered statistically significant. Of the 383 eyes of 275 patients with glaucoma, approximately 38.12% (146/383) were visually impaired. Additionally, 35.28% (97/275) had visual impairment in at least one eye due to glaucoma, whereas 7.64% (21/275) were blind at initial presentation due to glaucoma. In the multivariable binary logistic regression analysis, age, duration of treatment, treatment adherence, distance from the hospital, laterality, and intraocular pressure at presentation were identified as factors significantly associated with visual impairment in patients with glaucoma. The burden of visual impairment in patients with glaucoma is high. Therefore, creating awareness, conducting glaucoma screening, and counseling patients about the importance of treatment adherence are important for reducing the burden of visual impairment due to glaucoma.
INTRODUCTION
In 2010, approximately 4.2 million people were visually impaired and 2.1 million people were blind due to glaucoma [1]. A significant number of patients with glaucoma experience end-of-life visual impairment [2]; this issue is more prevalent in developing nations such as Ethiopia, where eye care service centers are limited and often inaccessible to the majority of the population. This burden is compounded by low eye-care-seeking behaviors and poor awareness of glaucoma in developing sub-Saharan countries. Delayed diagnosis and poor adherence are major problems for patients with glaucoma of low socioeconomic status, increasing the risk of visual impairment. Few studies conducted in Ethiopia have indicated low glaucoma medication adherence, ranging from 32.5% to 61.4% [3-6].
Visual impairment caused by glaucoma imposes a significant socioeconomic burden on individuals, families, and nations. It reduces normal functioning in daily activities, social interactions, self-care, and leisure activities [7,8]. It also affects postural sway on both firm and foam surfaces [9], increasing the risk of falling injuries in patients with glaucoma.
Although glaucoma medications have been proven to halt disease progression, factors such as adherence to medication, drug efficacy, socio-demographic factors, duration of follow-up, type of glaucoma, stage of glaucoma, and pretreatment intra-ocular pressure (IOP) are presumed to affect disease progression, thereby increasing the occurrence of blindness.
The prevalence of blindness in patients with glaucoma ranges from 4.4% to 44.0% [10-13]. Similarly, the prevalence of visual impairment in patients with glaucoma ranges from 26.0% to 56.7% [11-17]. Knowledge of the prevalence of visual impairment among patients with glaucoma is important for evaluating the effectiveness of treatment approaches and identifying factors contributing to blindness and visual impairment (low vision). However, the proportion of people who are visually impaired due to glaucoma and associated factors in the study area remain unknown. Therefore, this study is important as it provides baseline information for further studies and the planning of interventions to reduce visual impairment due to glaucoma. Evidence-based interventions are essential for maintaining psychological and social well-being and productivity.
MATERIALS AND METHODS
1. Study design, study area, and period
This hospital-based cross-sectional study was conducted at Hawassa University Comprehensive Specialized Hospital (HUCSH) located in Hawassa, the capital of the Sidama Regional State of Ethiopia, 275 km south of Addis Ababa. It is the only tertiary eye care and training center for ophthalmology residents and optometry students in the region. This study was conducted from May 1 to November 30, 2022. All patients with glaucoma who attended the HUCSH Ophthalmic Outpatient Department (OPD) during the data collection period.
The research was conducted according to the declaration of Helsinki. All findings reported were obtained by analyzing interview data and medical chart review; no experiments or invasive physical examinations were performed for the study participants. The study was approved by the Hawassa University Institutional Review Board with approval number HUCMHS 104/23 and ethical clearance was obtained.
The objectives and purpose of this study were explained to each participant, and written informed consent was obtained from each participant before beginning the interview. Informed consent for those who could not read and write was obtained from their parents or legal guardians. Only those who provided consent and were willing to participate were interviewed. To ensure confidentiality, the respondents were not asked to write their names at the time of interview. The consent declared that participant’s participation is voluntary. They were also informed there was no risk associated with refusal to participate and had the right to draw at any time they wished. They also have a full right to contact and ask authors what they want
2. Inclusion and exclusion criteria
All patients with glaucoma who attended the HUSCH ophthalmic OPD during the data collection period were included in the study. Patients with visually significant corneal opacities, cataracts, posterior capsular opacity after cataract surgery, age-related macular degeneration, or pathological myopia, or those who were mentally incompetent and unable to communicate were excluded from the study.
3. Sample size determination
The prevalence of blindness in a previous study in Addis Ababa was 44% [18]. Using P=0.44 with a marginal error of 5%, the total sample size was calculated as follows:
Since the estimated number of patients with glaucoma attending the hospital was 972 (i.e., less than 10,000), the final sample size was adjusted using the following correction formula:
Considering a 10% non-response rate of 27, the final sample size was adjusted to nf=272+27=298.
4. Sampling technique
The estimated number of patients with glaucoma attending the hospital during the study period was 973, with most being recurrent patients. All patients with glaucoma who presented to the glaucoma clinic during the data collection period and met the inclusion criteria were interviewed, and their visual status was assessed. Visual acuity and IOP of patients were reviewed from their medical charts.
5. Operational definitions
A patient is considered blind due to glaucoma if the best-corrected visual acuity (BCVA) in the glaucomatous eye is ≤3/60 [14].
Monocular blindness is defined as a BCVA ≤3/60 in the worst eye with glaucoma. A patient with glaucoma in one eye is considered to have monocular blindness if BCVA ≤3/60 in the glaucomatous eye, regardless of the fellow eye.
Visual impairment is defined as a BCVA of 6/18-3/60 in the glaucomatous eye [14].
Mild visual impairment is defined as a BCVA <6/6 or >6/18.
Moderate visual impairment is defined as a BCVA ≤6/18 or ≥6/60.
Severe visual impairment is defined as a BCVA <6/60 or >3/60.
Monocular visual impairment is defined as a BCVA 6/60 to 3/60 in the worse eye with glaucoma. A patient is considered to have monocular visual impairment if BCVA is 6/60 to 3/60 in the glaucomatous eye, regardless of the fellow eye [14].
The medication adherence rate was calculated using the following formula:
Adherence means patients with a medication adherence rate ≥80% were considered adherent, and those with <80% were considered non-adherent [15].
6. Quality control in the data collection procedure
A structured questionnaire was pre-tested for reliability and validity in 5% of the total sample size of patients with glaucoma attending Yirgalem Hospital. The questionnaire containing socio-demographic data and questions related to drug adherence, such as “Have you ever missed your glaucoma medication doses in the last week?”, “How many doses you missed in the last week?”, and “How many doses you were applying or taking daily?” was assessed for clarity, completeness, and reliability. Necessary amendments were made, and the revised questionnaire was translated into a local language for data collection and then retranslated into English after data collection by a language expert. Data collectors and supervisors received 2 days of training regarding using data collection tools, the study’s purpose, data collection skills, and ethical procedures. Participants were interviewed using a structured questionnaire, and their medical charts were reviewed. Data were cleaned to assess completeness, consistency, outliers, and missing values.
7. Data processing and analysis
The collected data were checked for completeness, imported into Epinfo, and then exported to SPSS ver. 22 (IBM, Armonk, NY, USA). Descriptive analysis and binary logistic regression were performed, and the findings were presented in tables and pie charts. Covariates with a P-value of less than 0.05 in the multivariable logistic regression were considered statistically significant. The variance inflation factor and tolerance tests were used to check for multicollinearity, with values ≥0.1 and <10, respectively, to control for confounders. The Hosmer-Lemeshow goodness-of-fit test was performed to assess model fit.
RESULTS
Approximately 275 patients participated in this study, with a response rate of 92.3%. Of these respondents, approximately 55.63% were male. The mean age of the participants was 58.34±2.97 years; the majority (54.19%) were from rural areas. More than half of the patients (62.71%) traveled 2 hours or more to reach the hospital (Table 1).
Socio-demographic data of the study participants (n=275)
Of the 275 patients with glaucoma, 148 had bilateral glaucoma, and 127 had glaucoma in only one eye. Out of the 383 eyes of these 275 study participants, 146 eyes of 97 patients had visual impairment due to glaucoma at presentation. The prevalence of visual impairment due to glaucoma in this study was 35.28% (97/275). Of the 146 visually impaired eyes, 75.34% (110/146) presented with severe visual impairment. Approximately 17.82% (49/275) of patients with glaucoma had bilateral visual impairment. Additionally, 7.64% (21/275) of patients were blind (BCVA, <3/60) in at least one eye due to glaucoma at the initial presentation to the hospital (Fig. 1).
Best corrected visual acuity of eyes with glaucoma at initial presentation among patients with glaucoma attending HUCSH. BCV: best-corrected visual, HUCSH: Hawassa University Comprehensive Specialized Hospital.
1. Factors associated with visual impairment
Multivariate binary logistic regression analysis identified the following factors significantly associated with visual impairment in patients with glaucoma (Table 2): age 51-65 years (adjusted odds ratio [AOR], 2.11; 95% confidence interval [CI], 1.61-6.35), age >65 years (AOR, 2.60; 95% CI, 1.41-5.08), duration of treatment (AOR, 1.94; 95% CI, 1.73-3.81), treatment adherence (AOR, 2.22; 95% CI, 1.50-5.13), distance from hospital: 2-3 hours travel time (AOR, 2.23; 95% CI, 1.94-6.73) and >3 hours travel time (AOR, 4.21; 95% CI, 2.57-10.15), having bilateral glaucoma (AOR, 2.03; 95% CI, 1.59-6.22), and IOP at presentation: 30.5-39.5 mmHg (AOR, 2.91; 95% CI, 1.99-5.38), and ≥40 mmHg (AOR, 4.44; 95% CI, 2.84-6.92).
Factors associated with visual impairment in patients with glaucoma in Hawassa (n=275)
DISCUSSION
The prevalence of visual impairment and blindness at presentation due to glaucoma in this study was 35.27% (97/275) and 7.63% (21/275), respectively.
1. Factors associated with visual impairment
Individuals in the age groups 51-60 years and ≥60 years were 2.11 times and nearly 2.6 times more likely to be visually impaired, respectively, compared with individuals aged <40 years (Table 2). Because glaucoma is a disease of the optic nerve, physiological reduction in aqueous outflow and retinal nerve ganglion loss with increasing age increases the susceptibility of the eyes to vision loss.
Patients with glaucoma who were recently enrolled, with a shorter follow-up of 2 years, were nearly twice as likely to have visual impairment compared to those with a longer follow-up of >6 years (Table 2). This is because most patients who were followed up for a longer period presented with better vision, which had been functional up to that time.
One issue with many patients with glaucoma is that they visit multiple health facilities seeking vision restoration for vision loss due to glaucoma. They often do not strictly adhere to their treatment until they receive a diagnosis from multiple physicians with the same opinion. During this period, they may discontinue their medication if they do not notice any visual changes and start searching for another eye care center or clinic. In the meantime, glaucoma continues to progress. By the time they decide to give up and adhere strictly to their treatment, some of their vision may have already been lost. In addition, those who were followed up for a longer period were more aware of the nature of the disease and had better adherence. Good treatment compliance is the key to preventing visual impairment due to glaucoma. In the present study, treatment adherence was also significantly associated with glaucoma-induced visual impairment. Non-adherent individuals were 2.22 times (Table 2) more likely to be visually impaired compared with adherent individuals.
The distance traveled to reach the hospital was another factor associated with visual impairment. The likelihood of visual impairment increases with distance. Individuals who traveled 2-3 hours and >3 hours to reach the hospital were 2.23 times and 4.21 times more likely to be visually impaired, respectively, compared with those who traveled <1 hour (Table 2).
Glaucoma laterality also affects the development of visual impairment. Individuals with bilateral glaucoma were 2.03 times more likely to have visual impairment due to glaucoma in at least one eye compared to those with monocular glaucoma.
The IOP is a determinant of visual impairment in patients with glaucoma. Individuals with IOP between 30.5-39.5 mmHg and ≥40 mmHg were 2.19 times and 4.44 times more likely to be visually impaired, respectively, compared to those with IOP ≤30.0 mmHg (Table 2). Higher IOP causes significant damage to the optic nerve in a shorter period if not treated properly.
The prevalence of visual impairment in this study was higher than that in studies from India (26.0%) [11]. However, it was lower than findings from studies in Cairo (56.7%) [16], Egypt (43.0%) [12], and Nigeria (51.1%) [15]. This discrepancy is because the present study identified only patients with visual impairment at initial presentation to the hospital. In contrast, previous studies reported all visually impaired individuals at the time of the study, regardless of when they became visually impaired.
Glaucoma blindness in Africa ranges from 10% to 30% [17]; however, it was reported to be 44% in Addis Ababa, Ethiopia [19]. In the present study, only 7.63% of patients were blind, although approximately 75.34% of visually impaired eyes presented with severe visual impairment (BCVA, <6/60 or >3/60) and were more likely to become blind within a short period. This prevalence was higher than that of a pooled analysis from studies in different parts of the world (4.4%) [10], a study in Cairo (5.9%) [16], and another study in Egypt (5.0%) [12]. However, it was lower than the results of studies in India (15.0%) [11], Nigeria (23.1%) [18], Addis Ababa (44.0%) [19], and Sweden (20.0%) [13]. Socio-demographic differences between Ethiopia and Egypt account for the reported higher prevalence of visual impairment. The difference in sample size may explain the reason for the discrepancy between the studies conducted in Nigeria and the present study. The Swedish study only included patients with low vision, whereas the present study included all patients with glaucoma.
In the present study, a significant number of patients with glaucoma were visually impaired and blind at initial presentation to the hospital due to various factors. Late presentation, due to distance from the hospital and the asymptomatic nature of the disease, contributed to visual impairment due to glaucoma. The likelihood of becoming blind increases with distance from the hospital. Approximately 64.73% of the study participants traveled more than 2 hours to reach the hospital, which was the main cause of late presentation for most participants. The majority of study participants were patients with bilateral glaucoma. Bilateral patients were more likely to be visually impaired because most of them noticed the disease after it damaged one eye and began to affect the other eye due to the asymptomatic nature of the disease. Therefore, late presentation, delayed diagnosis, and poor compliance with glaucoma medication, among other factors, increased the burden of visual impairment due to glaucoma. To decrease this burden, creating awareness and establishment of easily accessible eye care services at primary health facilities, such as health centers and primary hospitals, are crucial to strengthening proper, timely referrals and conducting glaucoma screening.
The present study aimed to identify the factors associated with visual impairment. A limitation of this study was that a visual field test was not included for all participants because the visual field test results were not available in their medical charts. Because visual impairment in this study was defined using only visual acuity, regardless of the visual field, the burden may have been underestimated. As glaucoma primarily affects the visual field, further studies should incorporate the visual field status in defining visual impairment, and performing visual field tests for each patient is important.