|ORIGINAL RESEARCH ARTICLE
|Year : 2016 | Volume
| Issue : 2 | Page : 51-57
Self-reported adherence rates in glaucoma patients in Southwest Nigeria
Adeola Olukorede Onakoya1, Chigozie Anuli Mbadugha2
1 Department of Ophthalmology, College of Medicine, University of Lagos/Lagos University Teaching Hospital, Idi-Araba, Nigeria
2 Department of Ophthalmology, Lions' Eye Centre, General Hospital, Isolo, Lagos, Nigeria
|Date of Web Publication||4-Apr-2016|
Chigozie Anuli Mbadugha
Department of Ophthalmology, Lions' Eye Centre, General Hospital, Isolo, Lagos
Source of Support: None, Conflict of Interest: None
Context: Nigerian glaucoma patients have an aversion to surgery and often rely on medical therapy to prevent disease progression. For medical therapy to be effective, the drugs have to be used as prescribed. Compliance has been reported to be low in the previous Nigerian studies. Aims: To evaluate the adherence rates of primary open angle glaucoma (POAG) patients on medical therapy using patient self-report. Settings and Design: A hospital-based cross-sectional design was used to assess consecutive POAG patients attending a glaucoma clinic in a Tertiary Hospital in Lagos, Nigeria. Subjects and Methods: Self-reported adherence was evaluated by trained interviewers. Comprehensive clinical assessment including intraocular pressure, gonioscopy, visual field assessment, and dilated binocular funduscopy using the slit lamp and + 78D fundus lens was done. Statistical Analysis Used: Data analysis was done using MedCalc Statistical Software. Results: One hundred and fourteen patients reported adherence rates ranging from 10% to 100% with a mean adherence rate of 82.33% ± 19.25%. Only 31 respondents (27.2%) reported 100% adherence. Duration of the disease was the only significant factor on multiple regression analysis. Conclusions: The development of strategies to improve compliance and persistence in glaucoma patients is crucial for the reduction of disease progression and blindness.
Keywords: Adherence rates, glaucoma, self-report
|How to cite this article:|
Onakoya AO, Mbadugha CA. Self-reported adherence rates in glaucoma patients in Southwest Nigeria. J Clin Sci 2016;13:51-7
| Introduction|| |
Glaucoma is the second leading cause of blindness in Nigeria  and the leading cause of irreversible blindness globally.  Reduction of intraocular pressure (IOP) using medications is the mainstay of glaucoma management in Nigeria as patients are often unwilling to accept the option of filtration surgery.  The consistent use of glaucoma medications as prescribed by physicians is crucial for the achievement of target IOPs and prevention of disease progression and visual loss in patients.  Adherence is defined as the degree to which a patient follows the instructions to take a prescribed treatment during a defined period of time  while persistence describes the time from initiation of therapy to its discontinuance by the patient. Adherence and persistence have largely replaced the term compliance although adherence and compliance are sometimes used interchangeably. Low rates of adherence or compliance to glaucoma medications have been reported in Nigeria , and other countries. ,
White coat adherence refers to more frequent and accurate use of eye drops close to clinic appointments and may explain disease progression despite apparent achievement of target IOPs. Some Nigerian glaucoma patients, on the contrary, exhibit "a reverse white coat adherence syndrome." They have a tendency not to use their eye drops prior to attending clinic visits as they "do not want the drugs to interfere with the results of tests done during the visit." The morning dose of eye drops due for application on the appointment day is often omitted. Nigerian glaucoma patients who exhaust their medication within a fortnight of their scheduled clinic appointment often do not refill their prescriptions because they are unsure if the doctor would recommend a different medication at that visit. This has also been reported by a Jamaican study. 
Adherence and persistence may be assessed using electronic monitors,  pharmacy refills and administrative claims data,  and self-reports.  We assessed the self-reported adherence rate of patients attending a glaucoma clinic in Southwest Nigeria with a view to elucidating factors that affect adherence and suggesting interventions to improve adherence.
| Subjects and methods|| |
A hospital-based, cross-sectional study design was used to evaluate self-reported adherence rates in patients attending a glaucoma clinic. Consecutive patients aged 40 years and above on topical medications for primary open angle glaucoma were recruited as participants. Patients with secondary glaucoma or other eye pathologies which could account for visual field defects simulating glaucoma were excluded from the study. The tenets of the declaration of Helsinki (October 2008 revision) were adhered to. Written informed consent was obtained from all participants, and ethical permission was given by the Institution's Research and Ethical Committee.
All patients were interviewed using a short questionnaire designed for the study in which biodata and relevant clinical information were noted. They all underwent a comprehensive ocular examination which included visual acuity assessment, Goldmann applanation tonometry; gonioscopy using a 2-mirror gonioscopy lens (Ocular instruments, Bellevue WA, USA); slit lamp examination (Haag-Streit Slit lamp); dilated stereoscopic optic nerve head assessment using a +78D contact lens (Volk instruments, USA); and standard automated perimetry (Optifield Sinemed Inc., Benicia, CA, USA). Reliable visual field tests were defined as: false-positive and false-negative errors <30% and fixation losses <20%. A modified Hodapp-Parrish-Anderson classification  was used to stage the disease. A mean deviation of ≤−6 decibels (dB) was defined as mild visual field loss, >−6 dB but <−12 dB as moderate visual field loss and >−12 dB as severe visual field loss. Cases were classified based on the more severely affected eye.
Self-reported adherence was evaluated by trained interviewers who were also the 2 nd year ophthalmology residents. They maintained an empathic stance and admitted to the participants that chronic use of medications on a daily basis could be bothersome and difficult to abide by. The adherence interview took place at the beginning of the clinic visit before the patients' consultation with the ophthalmologist carrying out the comprehensive clinical assessment. The participants were then asked to display their medications if available and give details of how they had been instructed to instill them and how they had been using their drugs. The interviewers were trained on the correct regimen for each medication. After ascertaining the correct prescribed regimen, the patients were asked to assess as a percentage, how exact their use of their medication in the past 30 days was in comparison to the correct prescribed regimen, taking the recommended frequency and timing into consideration. Patients who had adherence rates <100% were asked to give reasons for their failure to adhere to the prescribed regimen if any. Adherence rates were defined as good or adequate if they ranged from 95% to 100% and as poor or inadequate if they were <95%. 
The data obtained were analyzed using MedCalc Statistical Software Version 12.7.5 (MedCalc Software Buba, Ostend, Belgium). The influence of sociodemographic variables such as age, sex, religion, occupation, educational, and marital status on adherence rates was assessed using odds ratio (OR), Chi-square, and Fisher exact tests as appropriate. Multiple regression analysis was done to examine the influence of confounding variables. All tests were two-tailed, and a P < 0.05 was defined as statistically significant.
| Results|| |
The study population comprised 44 males (38.6%) and 70 females (61.4%) with a mean age of 58.58 ± 10.5 years. Twelve of them (10.5%) had a prior history of glaucoma surgery but were on topical ocular hypotensives at the time of the study. Self-reported adherence rates ranged from 10% to 100% with a mean adherence rate of 82.33% ± 19.25%. [Table 1] shows the mean adherence rates across varied patient characteristics. Only 31 respondents (27.2%) reported 100% adherence. Fourteen of them (45.2%) were male, whereas the rest (54.8%) were female. Fifty-nine respondents (51.75%) had adherence rates ranging from 80% to 95% while 24 (21.1%) reported adherence rates <80%. Half of the respondents with adherence rates <80% (n = 12) reported adherence rates ≤50%.
[Table 2] compares the patient characteristics of patients who had 100% adherence rates to those who did not. Patients who had been managed for glaucoma for <6 years were 12 times more likely to report 100% adherence than patients who had been managed for glaucoma for 6 years or more (OR: 12.93; 95% confidence interval [CI]: 1.67-100). There was no statistically significant difference in the adherence rates of patients with a positive family history of glaucoma compared to those without a family history (P = 0.81) or those who were aware of the disease for which they were being managed compared to those who were unaware (P = 0.22).
|Table 2: A comparison of patient characteristics of totally adherent patients to other patients|
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Majority of the respondents (n = 74, 64.9%) were on monotherapy. Thirty-four (29.8%) were on two topical medications while 6 (5.3%) were on three topical medications. Patients on monotherapy were not more likely to report 100% adherence than those on two or three medications (OR: 0.81; 95% CI: 0.34-1.89). [Table 3] shows the frequency and the mean self-reported adherence rates for the various drug classes and combinations the respondents were on.
[Table 4] shows the results of multiple regression analysis. Duration of disease was the only factor that remained statistically significant after regression analysis. The reasons given for failure to adhere to the treatment regimen are listed in [Table 5] in order of frequency.
| Discussion|| |
Adherence to glaucoma medications reduces the likelihood of progressive visual loss and blindness.  Poor adherence may result in repeated modification of drug regimens and performance of filtration surgeries. Poorly adherent patients are unlikely to use postoperative drugs adequately resulting in poor outcome, progression of disease, and visual loss. Poor compliance has been identified as a risk factor for glaucoma-related blindness. , Glaucoma patients benefit maximally from medical treatment if they adhere strictly to prescribed drug regimens, and physicians can only accurately assess the effectiveness of medical therapy in adherent patients.
More than two-thirds (72.8%) of the participants, in this study, reported <100% adherence. This is much higher than the 5-45% of participants not totally adherent in studies done in other countries. ,,,, It is even higher than the 60-66.1% noncompliance rates previously reported by earlier studies in Nigeria. ,, Patient, prescriber, or dispenser based reasons for noncompliance of Nigerian glaucoma patients have been reported previously. 
Surprisingly, an awareness of their diagnosis did not correspond to statistically significant higher adherence rates and suggested that other factors that influence adherence, such as cost of treatment, may play major roles in determining patient adherence. Several studies have reported that adequate patient knowledge and understanding of the disease is associated with better adherence to medical treatment. ,,,,,,, Although patients with a positive family history of glaucoma were more likely to report total adherence than those without, this finding was not statistically significant [Table 2]. Omoti and Waziri-Erameh  reported that a family history of glaucoma was not associated with better compliance.
Duration of disease
Patients who had been managed for glaucoma for 6 years and more had the lowest adherence rates [Table 1] and were 12 times less likely to report 100% adherence though the extremely wide CI (1.67-100) suggests that a study with a larger sample size will give a more precise estimate of this effect. Over time, patients' fear of blindness and faith in drop efficacy, which have been identified as motivating factors for adherence , may reduce and result in less adherence. This is contrary to the finding in other studies ,, that patients with a longer duration of disease adhered better to medications. Duration of disease was the only factor affecting adherence that remained statistically significant after multiple logistic regression analysis [Table 4]. Periodic eye health messages to improve adherence should therefore be designed to include even patients who have been managed for glaucoma for a long time.
The complexity of the drug regimen as evidenced by the number of eye drops did not influence self-reported adherence rates in this study [Table 1] and [Table 2]. Patients on monotherapy did not report higher adherence rates [Table 4]. Intensive patient counseling about higher baseline IOPs or failure to achieve target IOPs necessitating the use of two classes of antiglaucoma medications may have resulted in greater patient motivation for adherence to treatment in this group of patients. Some other studies ,,, also did not find higher adherence rates in patients with simpler drug regimen. On the contrary, other studies have reported better compliance rates in patients on single daily drug doses or combination treatment. ,,
Severity of disease
Adherence rates increased with increasing severity of the disease [Table 1], although this trend was not statistically significant (P = 0.62). Patients with a history of previous glaucoma surgery in this study also reported better adherence rates than those who had been on medical therapy only [Table 1]. This difference between patients who had undergone surgery for glaucoma and those who had not was also reported in the study by Castro et al. 
Barriers to adherence
The most common reasons proffered by patients for nonadherence [Table 5] were the inconvenience of using eye drops which disrupt daily routines, forgetfulness, and cost and lack of availability of drugs. Tsai et al  systematically classified factors affecting compliance into patient, provider, environmental and regimen factors. In this study, environmental factors (competing interests), regimen factors (cost, availability, side effects) and patient factors (cost, knowledge, forgetfulness, motivation/health beliefs) were largely implicated.
Inconvenience and forgetfulness which were the leading reasons for nonadherence in this study were less common in a previous study in Southwest Nigeria.  This may be due to the fact that the cosmopolitan city of Lagos in which the present study was conducted is characteristically busier and more hectic than in Benin City, the study town of the earlier study. Cost and unavailability were major reasons for default in the two studies. This is not surprising as some antiglaucoma drugs are expensive and most Nigerian patients make out of the pocket payments for their drugs. Most of these medications are imported into the country, and any logistic difficulty in this process results in a sudden scarcity of the drugs with severe consequences on the patients. There is therefore need to explore the possibility of local manufacture of antiglaucoma drugs and encourage better subscription to the evolving National Health Insurance Scheme to reduce these barriers. Side effects were not a leading cause of nonadherence, unlike in the earlier study.  This may have been due to the fact that the drug regimen used by participants in the two studies varied. Some of these reasons given for nonadherence have been reported previously: Forgetfulness, ,,,,,, cost, ,,, unavailability, , and side effects. ,,
The relationship between adherence and sociodemographic factors such as age, gender, race, ethnicity and education is complex  but can assist in identifying patient characteristics that suggest a higher likelihood of nonadherence. In this study, age, gender, ethnicity, religion, occupation, marital, and educational status did not significantly influence adherence [Table 2]. This is similar to the findings in earlier studies in Nigeria. , Similarly, Mowatt et al.  in Jamaica reported that age, gender, and education had no effect on adherence. Kosoko et al.  reported that males were less adherent than females while Lunnela et al.  found no gender difference in their study. Both studies, , however, report that older patients were more adherent than younger patients.
There was an unusually low male to female ratio (0.63:1) in this study compared to other hospital-based studies previously reported in Nigeria. Some studies done in Nigeria , reported male preponderance with a male:female ratio of about 1.3:1. Onyekwe et al.  in Onitsha, Southeast Nigeria, however, reported a slight female preponderance in their study with a male:female ratio of 1:1.1. The reason for the female preponderance in this study is unclear. It could suggest that females in the study location were more enlightened and had better health seeking behaviors, or perhaps found it easier to take time off work for hospital visits than their male counterparts, or it may have been an incidental finding as participants were recruited consecutively into the study.
We recommend periodic patient education by trained office staff or counselors using patient-centered communication techniques. Tailoring drug regimens to daily routines may enhance memory, reduce forgetfulness, and make drug instillation appear less disruptive to busy daily schedules. Written instructions or medication reminders in diaries or phones and involvement of a committed caregiver or assistant may also improve adherence. There is also a need for advocacy to reduce the cost of antiglaucoma drugs and improve year-round availability.
Strengths and limitations of this study
The results of this study though not generalizable to the community, provide valuable insight into the factors influencing adherence in this population. Adherence was measured using self-report method which was the most feasible method in our environment. Self-report has been associated with overestimation, recall, and pleasing bias.  Recall bias may have been reduced by limiting the period of assessment of adherence to the preceding 4 weeks, but this could not be totally eliminated. Pleasing bias was reduced by using trained interviewers who were empathic and nonjudgmental in their enquiry. With 72.8% of participants admitting <100% adherence, it is unlikely that overestimation occurred significantly in this study.
| Conclusions|| |
The high proportion of patients reporting less than total adherence to glaucoma medications in this study is worrisome. It highlights the need for focused and aggressive interventional strategies to improve adherence to medical treatment among Nigerian glaucoma patients. This is crucial for the reduction of glaucoma-related blindness in Nigeria.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]