|Year : 2022 | Volume
| Issue : 2 | Page : 145-151
Determinants of patients' adherence to glaucoma topical therapy among Nigerian adults
Olamide Yetunde John-Sam1, Abdulkabir Ayansiji Ayanniyi2, Rilwan Chiroma Muhammad2
1 Department of Ophthalmology, University of Abuja Teaching Hospital, Abuja, Nigeria
2 Department of Ophthalmology, University of Abuja Teaching Hospital; Department of Ophthalmology, College of Health Sciences, University of Abuja, Abuja, Nigeria
|Date of Submission||28-Mar-2022|
|Date of Acceptance||24-Nov-2022|
|Date of Web Publication||11-Jan-2023|
Abdulkabir Ayansiji Ayanniyi
Department of Ophthalmology, Faculty of Clinical Sciences, College of Health Sciences, University of Abuja, PMB 117, Abuja
Source of Support: None, Conflict of Interest: None
Context: Glaucoma is a leading cause of irreversible blindness globally. Among its risk factors only raised intraocular pressure is modifiable with capacity to reduce the progression of glaucoma. Adherence to intraocular pressure lowering medications is a key factor in the medical management of glaucoma.
Aims: The aim of this study was to determine adherence to glaucoma topical medications and its determinants among patients.
Settings and Design: This was a comparative longitudinal hospital-based study.
Subjects and Methods: Ninety-six primary open-angle glaucoma patients were randomly grouped into A and B and surveyed for topical medication adherence and its determinants. All participants were counseled on medication adherence, and given dosing time schedule. Participants in Group B/reliable household members were reminded through phone calls to use their medications. Adherence level, its determinants, effect of adherence on intraocular pressure (IOP), and central visual field defect progression were assessed at baseline, 90 days, and 180 days.
Statistical Analysis Used: Data normality was tested using Shapiro–Wilk test. Results were presented in frequency tables, figures, and charts. Chi-square test, Fisher's exact test, and odds ratio were used to evaluate the associations between variables where applicable. Multivariate logistic regression was employed to determine factors predicting adherence. The level of statistical significance was set at P < 0.05.
Results: At baseline, 35.4% of the participants were adherent to medications, with intervention at 90 days (81.2%, A, and 79.2%, B) and at 180 days (75.0%, A, and 83.3%, B) of the participants who adhered to medications. Predictors of adherence to medications were age below 40 years (adjusted odd ratio [AOR] = 5.10; 95% confidence interval [CI], 1.18–21.82; P = 0.029) and the presence of comorbidities (AOR = 5.41; 95% CI, 1.64–17.86; P = 0.009). There was no significant difference in the mean IOP between the two groups at baseline, 90 days, and 180 days.
Conclusions: There was an improvement in medication adherence following counseling. Younger age and comorbidities were notable adherence determinants.
Keywords: Adherence, glaucoma, intraocular pressure
|How to cite this article:|
John-Sam OY, Ayanniyi AA, Muhammad RC. Determinants of patients' adherence to glaucoma topical therapy among Nigerian adults. Santosh Univ J Health Sci 2022;8:145-51
|How to cite this URL:|
John-Sam OY, Ayanniyi AA, Muhammad RC. Determinants of patients' adherence to glaucoma topical therapy among Nigerian adults. Santosh Univ J Health Sci [serial online] 2022 [cited 2023 May 30];8:145-51. Available from: http://www.sujhs.org/text.asp?2022/8/2/145/367579
| Introduction|| |
Glaucoma, the second most common cause of blindness and the leading cause of irreversible blindness worldwide, is characterized by progressive cupping and atrophy of the optic nerve head. However, blindness from glaucoma can be avoided by early diagnosis and sustained effective treatment.
The global prevalence of glaucoma for population aged 40–80 years is 3.54% with the highest prevalence of primary open-angle glaucoma (POAG) in Africa and primary angle-closure glaucoma in Asia. In 2013, the number of people aged 40–80 years with glaucoma worldwide was estimated to be 64.3 million which was projected to increase to 76.0 million by the year 2020 and 111.8 million by the year 2040.
In Nigeria, the prevalence of glaucoma and glaucoma blindness was found to be 5.02% and 0.7%, respectively, among Nigerians aged 40 years and above with POAG being more common.
The major modifiable risk factor for glaucomatous progression is intraocular pressure (IOP); lowering it reduces the progression of glaucoma and effective medical treatment reduces the risk of progression by 50%.,
Patients' adherence to treatment regimens significantly delays glaucomatous disease progression., Regrettably, poor adherence remains a significant barrier to effective treatment. This study was conducted to determine patients' adherence to glaucoma medication, the factors associated with adherence, and the effect of adherence on central visual field (CVF) progression and IOP control. The findings would be useful in understanding and managing antiglaucoma medication adherence among glaucoma patients.
| Subjects and Methods|| |
Ethical clearance (UATH/HREC/PR/2019/035) was obtained from the Institutional Health Research Ethics Committee, and the study followed the principles outlined in the Helsinki Declaration.
The study was comparative longitudinal hospital based and conducted between December 2019 and October 2020. However, for COVID-19 lockdown, the study period would have been shorter. Consecutive patients, at least age 18 years, with POAG on antiglaucoma medications for at least 3 months who presented at the outpatient clinic within the study period and gave written informed consent were enrolled and allocated into Groups A and B using a simple random sampling technique.
The patients who were excluded from the study include those who had other types of glaucoma aside primary open angle glaucoma (POAG) and those with mental disabilities or medical conditions that can compromise the participant's cooperation with the study processes. Also excluded from the study were patients with primary open angle glaucoma (POAG) but with the visual acuity (VA) worse than 6/60 or with previous trabeculectomy or with ocular comorbidities obscuring the view of the eye fundus.
The minimum sample size of 96 with 48 participants in each group was calculated for comparative longitudinal study with confidence level set at 95%. Semi-structured pretested interviewer-administered questionnaires were used to obtain information about the age, sex, occupation, educational status, and marital status. Other data collected included determinants of medication adherence such as duration of disease, knowledge on glaucoma and treatment, comorbidities, glaucoma medications used and side effects, and patients' belief on glaucoma.
Assessment of adherence
Participants' level of adherence was assessed at baseline, 90 days, and 180 days using the Visual Analog Scale; adherent (VAS = 10) and nonadherent (VAS = 0), eye drop instillation technique; adherent (score = 5) and nonadherent (score <5), and eight-item Morisky Medication Adherence Scale (MMAS) graded in this study into adherent (MMAS = 8) and nonadherent (MMAS <8). The level of adherence among participants in the two groups was assessed at baseline, 90 days, and 180 days.
Eye drop installation technique
Participants were observed and scored while instilling sterile artificial tears eye drop at baseline, 90 days, and 180 days. Eye drop technique was graded as adherent in participants who scored 5 and nonadherent in those who scored <5. Participants were scored as follows: time required for the first drop from uncapping (1 = <1 min, 0 = more than 1 min), number of drops instilled into the eye (1 = one drop, 0 = more than 1 drop), the tip of the bottle of eye drops touched any part of the face (yes = 0, no = 1), closure of the eyelid with or without the occlusion of the punctum after the instillation of the anti-glaucoma drug to the eye drops instilled into conjunctiva sac (yes = 1, no = 0).
In intervention 1, both groups (A and B) were counseled based on the deficit noted during the participants' interview/information collection. Further, each participant was requested to keep the record of the anti-glaucoma drug administered to the eyes for treatment using a chart and the dosing time scheduled was also agreed upon based on the participant's convenient time at baseline. In intervention 2, group B participants or a reliable household member (for those who did not have mobile cell phones or with language barrier) were also contacted using phone calls throughout the study period as a means of reminder to use their medications. Therefore, group A had intervention 1 only while group B participants had interventions 1 and 2.
Visual acuity and refraction
Aided (pinhole and spectacle) and unaided VA of each participant was assessed using illuminated Snellen acuity chart at 6 m. Pinhole VA test was done for VA worse than 6/9, and participants with improvement of VA on pinhole test were refracted. At the 6th month, a drop in the VA by one line compared to the baseline was considered worsening of vision. Participants with worsening vision at 180 days had refraction and those with poor IOP control had their medications reviewed.
Central visual field
This was assessed using the automated perimeter with threshold strategy testing algorithm of 24-2 or 10-2 and target size III or V for VA of 6/60 at baseline, 3rd month, and 6th month considering accurate reliability indices of false positive <33%, false negative <33%, and fixation loss <20%. The CVF printout was used in grading the severity of glaucoma and also observed for progression using HAP 2 criteria part III. Baseline CVF was selected considering the difference of 2 dB with mean deviation (MD) of ≥6 dB or 1.5 dB in MD <6 dB in two CVF printouts done at a week interval.
Ocular examination was done by a single ophthalmologist who also did the CVF testing, gonioscopy, and IOP measurements. The anterior chamber angle was assessed using gonioscopy or Van Herick method with the aid of slit-lamp bio-microscope; Grades 3 and 4 were considered open angle to confirm the diagnosis of POAG. The IOP was measured using Goldmann applanation tonometer after staining with fluorescein strip under topical anesthetic (amethocaine) cover. The IOP was observed for control using the European Glaucoma Society 2003 recommendation on target IOP for POAG.
The recommended target IOP for POAG; IOP of <18 mmHg for early glaucoma, <15 mmHg for moderate glaucoma, <12 mmHg for advanced glaucoma, and <10 mmHg for end-stage glaucoma.
Optic nerve head and retina were assessed for signs of glaucoma using the slit-lamp indirect ophthalmoscopy using a + 78D hand-held noncontact lens.
Glaucoma severity grading
The severity of POAG was graded based on the level of optic disc appearance and CVF printout using the new glaucoma staging into mild, moderate, and severe stages. The staging of the disease was done considering the worse eye.
New Glaucoma Staging [International Classification of Diseases Tenth Revision (ICD-10)]
Mild or early stage (365.71)-glaucomatous optic nerve abnormalities consistent with glaucoma but no visual field abnormalities on white visual field test. Moderate stage (365.72)–glaucomatous optic nerve abnormalities with visual field abnormalities in one hemifield and not within 5° of fixation. Severe/advanced/end stage (365.73)–glaucomatous optic nerve abnormalities with visual field abnormalities in both hemifields and or loss within 5° of fixation in at least one hemifield.
Participants were said to have POAG when they have glaucomatous optic nerve damage with characteristic visual field loss, open anterior chamber angle of Grade 3 or 4 on gonioscopy, or Grade 4-3 anterior chamber depth using Van Herick method (for patients uncooperative for gonioscopy) who had been on antiglaucoma medications for at least 3 months.
Participants with POAG were said to be adherent when they conform to the recommendations on day-to-day treatment by the provider with respect to the timing, dosage, and frequency (participants who scored 8 on MMAS-8, 10 on VAS, and 5 on eye drop instillation technique). Participants with POAG were said to be nonadherent when they do not conform to the recommendation on day-to-day treatment by the provider with respect to the timing, dosage, and frequency (participants who scored <8 on MMAS-8, 0 on VAS, and <5 on eye drop instillation technique). Poorly controlled IOP is IOP not in keeping with the European Glaucoma Society-recommended target pressure of IOP ≥18 mmHg in early glaucoma, IOP ≥15 mmHg in moderate glaucoma, IOP ≥12 mmHg in advanced glaucoma, and IOP ≥10 mmHg in end-stage glaucoma.
CVF progression was assessed using the (Hodapp-Anderson-Parrish) HAP 2 criteria part III for visual field loss progression with any of the following:
Previously normal area on at least two consecutive fields with:
- A single point that decline by ≥10 dB
- Within the central 10°, 2 or more points each of which declines by ≥5 dB compared to baseline
- Outside central 10°, a cluster of 3 or more points each of which declines by ≥5 dB compared to baseline.
Within a preexisting defect, any of the following on at least two consecutive fields:
- A single point that decline by ≥15 dB
- Within central 10°, any point that declines by ≥10 dB
- Outside central 10°, a cluster of 3 or more points each of which declines by ≥10 dB compared to the baseline or each of which declines ≥5 dB on three consecutive fields.
Data were collected on standardized forms following strict regulations to ensure data confidentiality and analyzed using the Statistical Package for the Social Sciences (SPSS) software (IBM Corp., SPSS statistics for Windows version 25.0; SPSS Inc., Chicago, Illinois USA). Data normality was tested using Shapiro–Wilk test. Presentation of results was done with the use of frequency tables, figures, and charts. Chi-square test, Fisher's exact test, and odds ratio were used to evaluate associations between variables where applicable. Multivariate logistic regression was used to determine factors predicting adherence. The level of statistical significance was set at P < 0.05 across all parameters.
| Results|| |
A total of 96 participants were recruited for the study and all were followed up for a period of 6 months giving a response rate of 100%. There were 48 participants each in Groups A and B.
Participants were aged between 28 and 75 (mean: 53.26 ± 12.7) years [Table 1]. Majority of the participants were 40 years and above, educated, married, and had a monthly income of at least eighteen thousand Naira (₦18,000) (exchange rate: 1 USD to about four hundred Naira at the period of study).
Comparison of medication adherence level of the patients in the two groups at baseline using the self-reported adherence measures (MMAS-8 and VAS) and direct observation of drop instillation technique (Eye Drop Instillation Scale [EIS]) revealed that adherence level of participants measured with eight-item MMAS was lower compared to the adherence level measured using VAS at baseline. The observed difference in adherence at baseline using MMAS-8 and VAS was statistically significant [P = 0.048, [Table 2]].
|Table 2: Comparison of the level of medication adherence of participants at baseline|
Click here to view
Following intervention (counseling, dosing time schedule, and eye drop instillation charting in Group A and in addition mobile phone calls as reminder for medication use in Group B). In Group A, adherence to medications increased from 20 (41.7%) at baseline to 39 (81.25%) participants at 90 days and this decreased slightly to 36 (75%) participants at 180 days using MMAS-8. In Group B, adherence increased from 14 (29.2%) to 38 (81.25%) participants at the 90 days and 40 (83.34%) participants at the 180 days. Technique of eye drop installation also increased across both Groups A and B after intervention [Table 3].
Participants who were within the age group <40 years were 5.1 times more likely to be adherent to medications than those within the age group ≥40 years (adjusted odd ratio [AOR] = 5.10; 95% confidence interval [CI], 1.18–21.82; P = 0.029).
Participants with comorbidities were 5.4 times more likely to be adherent compared to those without comorbidities [AOR = 5.41; 95% CI, 1.64–17.86; P = 0.009, [Table 4]]. Participants with no previous instructions were less likely to be adherent to medications compared to those with previous instructions on instillation of antiglaucoma eye drops [crude odds ratio (COR) = 0.34; 95% CI, 0.17–0.70; P = 0.016, [Table 5]].
|Table 4: Factors predicting adherence to medication among participants at baseline|
Click here to view
|Table 5: Association between previous instructions on eye drop instillation and adherence using Eye Drop Instillation Scale at baseline|
Click here to view
At 90 days, participants in Group A with nonprogression of CVF defect were 4.5 times more likely to be adherent (COR = 4.50; 95% CI, 0.96–21.07; P = 0.049) compared to those with progression of CVF defect. Participants in Group B with nonprogression of CVF defect were 5.8 times more likely to be adherent (COR = 5.80; 95% CI, 1.88–17.71; P = 0.000) compared to those with progression of CVF defect.
At 180 days, participants in Group A with nonprogression of CVF defect were 5.3 times more likely to be adherent (COR = 5.31; 95% CI, 1.22–23.16; P = 0.019) compared to those with progression of CVF defect. Participants in Group B with nonprogression of CVF defect were 67% less likely to be adherent (COR = 1.67; 95% CI, 0.36–7.67; P = 0.509) compared to those with CVF defect progression [Table 6].
|Table 6: The effect of medication adherence on central visual field defect progression among the participants using eight-item Morisky Medication Adherence Scale|
Click here to view
Out of 96 participants, only 25 (26%) of the 96 participants received instructions on how to instill eye medications at baseline [Figure 1]. At baseline, the mean IOP in Group A was 18.75 ± 0.80 mmHg and in Group B it was 21.30 ± 1.01 mmHg. The observed difference was not statistically significant between the two groups (t-test = −0.639, P = 0.524).
|Figure 1: previous instructions on eye drop instillation at baseline among participants|
Click here to view
The mean IOP at 90 days was 15.17 ± 0.77 mmHg in Group A and 15.40 ± 0.78 mmHg in Group B. The observed difference between the two groups was not statistically significant (t-test = −0.418, P = 0.677).
At 180 days, the mean IOP was 14.71 ± 0.77 mmHg in Group A and 13.66 ± 0.69 mmHg in Group B. The observed difference was not statistically significant between the two groups [t-test = −1.107, P = 0.271, [Figure 2]].
|Figure 2: Comparison of the mean intraocular pressures between the study groups over 180 days. Key: Group A – study group with intervention 1, Group B – study group with intervention 2. The observed differences between the two groups at baseline, 90 days, and 180 days were all not statistically significant (t-test = −0.639, P = 0.524, t-test = −0.418, P = 0.677, t-test = −1.107, P = 0.271, respectively)|
Click here to view
| Discussion|| |
This study assessed the determinants of adherence to glaucoma topical therapy among 96 individuals with POAG. All patients were followed up for 6 months given a response rate of 100% which is considered a strength of the study. The predictors of adherence in this study were younger age and the presence of comorbidities. Adherence of participants to glaucoma medication was found to be influenced by the intervention; counseling, dosing time schedule, and telephone mobile calls as means of reminder.
In this study at baseline 34 (35.40%) participants were adherent to antiglaucoma medication similar to previous studies by Abdull et al. and Onakoya et al. Following intervention, improvement in level of adherence to medication was noticed in both groups over the study period and this was similar to a study done by Newman-Casey et al. which noted a decrease in nonadherence with subsequent clinic visits. Proper counseling of glaucoma patients prior to commencement of medications will help improve medication adherence, the lack of counseling on the importance of medication adherence and drug instillation technique as seen in this study where only 26% had been given instruction on drug installation may have accounted for the low medication adherence noted at baseline in this study.
MMAS is a type of self-reported adherence measure validated and used by researchers in chronic illnesses. In this study, adherence to medication was found to be significantly higher in both study groups at baseline, 3, and 6 months using VAS when compared with MMAS-8. This was also noted in a study done by Ung et al. using pharmacy refill data and VAS in assessing level of adherence among participants.
This study found that younger participants and participants with comorbidities were more likely to be adherent to antiglaucoma medication similar to a study done by Tamrat et al. in Ethiopia where older age group was noted for nonadherence to medication. Elderly patients may forget to instill medications or may be dependent on others for drug instillation leading to missed doses in the absence of their dependents.
Predictors of poor medication adherence such as poor knowledge of glaucoma, shorter disease duration, advanced glaucoma stage, male gender, poor patient-provider communication, lower monthly income, lower educational level, depression, and longer interval of follow-up found to be significant in some studies,, were not found to be predictors of adherence in this study similar the study done by Ung et al. using pharmacy refill data and VAS in assessing level of adherence among participants. This may be attributable to the small sample size in this study reducing the effect of these factors on adherence and may be due to the fact that the characteristics of the study location being a public hospital with greater ethnic diversity and demographic difference.
At baseline, 50% of the participants had poor eye drop instillation technique and 74% had never received instruction on how to instill their eye drops. There was a statistically significant association between no previous instruction on eye drop instillation and poor eye drop technique in this study similar to a study done by Tatham et al.
The eye drops instillation technique of participants using the EIS, improved from 50% to over 90% in both groups at 180 days in this study. This improvement could be attributed to the intervention applied in both groups.
In this study, the mean IOP at baseline in Group A was 18.75 ± 0.8 mmHg and 21.30 ± 1.0 mmHg in Group B which decreased in both groups at 90 days with an even further decrease at 180 days in both groups over the study period. This can be attributable to the intervention resulting in majority of the participants' becoming adherent to their medications.
A significant association was noted between nonprogression of CVF defect and adherence to medication at the 90 and 180 days in this study similar to a study by Newman-Casey et al. which reported that poor medication adherence was associated with MD loss over time However among Group B participants, no association was found between nonprogression of CVF defect and adherence to medication after 180 days of follow-up. The small sample size of this study could be responsible for this finding.
The findings of the study should be interpreted with caution due to its small sample size. The results may not be a true reflection of the general population being a Hospital based study. (The small sample size and the hospital-based nature of the study as its limitations).
| Conclusions|| |
In conclusion, the study assessed the determinants of adherence to medications among patients with POAG and found younger participants and those with comorbidities to be more adherent to their medications. Adherence was seen to increase following counseling and reminders through phone calls. Adherence to medication was noted to have a positive effect on CVF defect progression and IOP control. It is thus recommended that phone calls to serve as reminders for eye drop instillation by patients or their relations along with periodic assessment of medication adherence and eye drop instillation technique of glaucoma patients be reviewed during follow-up visits.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Quigley HA, Broman AT. The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol 2006;90:262-7.
Smith JS. Glaucoma. In: Elsevier BV, editor. Eye Diseases in Hot Climates. 4th
ed., Ch. 15. New Delhi: Butterworth Heinemann Medical; 2005. p. 299-305.
Tham YC, Li X, Wong TY, Quigley HA, Aung T. Global prevalence of glaucoma and projection of glaucoma burden through 2040: A systematic review and meta-Analysis. Ophthalmology 2014;121:2081-90.
Kyari F, Entekume G, Rabiu M, Spry P, Wormald R, Nolan W, et al.
A population-based survey of the prevalence and types of glaucoma in Nigeria: Results from the Nigeria national blindness and visual impairment survey. BMC Ophthalmol 2015;15:176.
Leske MC, Heijl A, Hyman L, Bengtsson B. Early manifest glaucoma trial: Design and baseline data. Ophthalmology 1999;106:2144-53.
Heijl A, Leske MC, Bengtsson B, Hyman L, Bengtsson B, Hussein M, et al.
Reduction of intraocular pressure and glaucoma progression: Results from the early manifest glaucoma trial. Arch Ophthalmol 2002;120:1268-79.
Plakas S, Mastrogiannis D, Mantzorou M, Adamakidou T, Fouka G, Bouziou A, et al
. Validation of the 8-item morisky medication adherence scale in chronically ill ambulatory patients in rural Greece. Open J Nurs 2016;6:158-69.
Adio AO, Onua AA. Economic burden of glaucoma in rivers state, Nigeria. Clin Ophthalmol 2012;6:2023-31.
Hodapp E, Parrish RK, Anderson DR. Clinical Decisions in Glaucoma. St Louis: The CV Mosby Co; 1993. p. 52-61.
Fellman RL, Mattox CG, Ross KM. Know the new glaucoma staging codes. EyeNet Mag 2011. p. 65-6. Available from: http://www.aao.org>eyenet>article>K
. [Last accessed on 2018 Oct 20].
Detry-Morel M. Currents on target intraocular pressure and intraocular pressure fluctuations in glaucoma management. Bull Soc Belge Ophtalmol 2008;308:35-43.
Abdull MM, Gilbert CC, Evans J. Primary open angle glaucoma in northern Nigeria: Stage at presentation and acceptance of treatment. BMC Ophthalmol 2015;15:111.
Onakoya AO, Mbadugha CA. Self-reported adherence rates in glaucoma patients in South West Nigeria. J Clin Sci 2016;13:51-7. [Full text]
Newman-Casey PA, Niziol LM, Gillespie BW, Janz NK, Lichter PR, Musch DC. The association between medication adherence and visual field progression in the collaborative initial glaucoma treatment study. Ophthalmology 2020;127:477-83.
Ung C, Zhang E, Alfaro T, Murakimi Y, Zhang M, Seider MI, et al
. Glaucoma severity and medication adherence in a county hospital population. Ophthalmology 2013;120:1150-7.
Tamrat L, Gessesse GW, Gelaw Y. Adherence to topical glaucoma medications in Ethiopian patients. Middle East Afr J Ophthalmol 2015;22:59-63.
] [Full text]
Rajurkar K, Dubey S, Gupta PP, John D, Chauhan L. Compliance to topical anti-glaucoma medications among patients at a tertiary hospital in North India. J Curr Ophthalmol 2018;30:125-9.
Tatham AJ, Sarodia U, Gatrad F, Awan A. Eye drop instillation technique in patients with glaucoma. Eye (Lond) 2013;27:1293-8.
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]