The study was conducted at the Archbishop Ackon Memorial Christian Eye Centre which is a specialist eye care facility and a glaucoma referral centre in the Central Region of Ghana. The eye care workforce at this specialist eye centre consisted of ophthalmologists, optometrists, ophthalmic nurses and opticians. The daily ophthalmic patient attendance to the facility averages one hundred, of which close to 30% are glaucoma patients .
Study design and sampling
A cross sectional survey of patients with POAG was conducted between February and May, 2019. The sample for this study was 400 patients with POAG who were systematically sampled when they reported for routine reviews at this specialist eye facility. The sample size was determined using the formula N = Z2 (1–p) (p)/b2, where N = minimum sample size, z = the standard normal deviation, set at 1.96 which corresponds to the 95% confidence interval, p = estimated prevalence of 30% , b = degree of accuracy desired, usually set at 5%. Per this equation, the sample size was determined to be 323 which was adjusted to 400 participants to account for attrition rate and inefficiencies associated with the small sample size.
Inclusion and exclusion criteria
Eligibility for participation in the study was all patients who had been diagnosed of POAG and were receiving treatment at the specialist eye care facility for at least three months . Diagnosis of glaucoma that met the inclusion criteria was based on a typical glaucomatous optic nerve head abnormalities on dilated fundoscopy (including notching, pallor, disc hemorrhages, vertical cup-to-disc ratio equal to or greater than 0.5 or difference in cup disc ratio of more than 0.2 in the two eyes); abnormal glaucoma hemifield test or a pattern deviation consistent with glaucoma (including temporal wedge, nasal step, altitudinal defect, partial arcuate defect etc.); gonioscopically confirmed open anterior chamber angles [18, 23]. Further, patients were included if they had no history of psychotic illness, were not alcoholic or on drugs, and did not have dementia as indicated on their medical folders or through verbal responses. Participants were excluded if they were less than 18 years old, had other kinds of glaucoma (closed-angle, congenital or other secondary glaucomas), had a history of cognitive contra-indications like traumatic brain injury, seizure disorders, unstable ocular conditions (uveitis, cataract, recent trauma, diabetic retinopathy) and chronic medical conditions (diabetes, sickle cell, hypertension) [8, 19].
Research tools and measures
The Big Five Inventory Questionnaire
The Big Five Inventory questionnaire is made up of 44 items measuring five trait dimensions of personality . These are extraversion (8 items), agreeableness (9 items), conscientiousness (9 items), neuroticism (8 items) and openness to experience (10 items). The items were measured on a five point Likert scale ranging from 1 = disagree strongly to 5 = agree strongly. Examples of items on the questionnaire include – I see myself as someone who: “tends to find fault with others”, “does a thorough job”, “is reserved”, “can be cold and aloof”. After the respondents answer the inventory, the options they choose on the Likert scale for the various items are summed for each trait dimension. Scores equal to or above the fiftieth percentile in a trait was graded high in that particular trait and scores below the fiftieth percentile were considered low. This classification was made to show where personality strengths and weaknesses of the participants placed. The dimension with the highest score is considered as the dominant personality trait of the respondent .
Medication Adherence Report Scale 5
The Medication Adherence Report Scale 5 (MARS-5) was used to measure participants’ self-reported adherence to their glaucoma medication regimens . Each of the five items on the questionnaire was rated on a five point Likert scale from 1= very often to 5 = never. Some items on the questionnaire include “I take less than instructed” and I stop taking it for a while”. Lower scores indicate lower levels of adherence and vice versa. Adherence was measured by computing the five individual items into a composite one with a total score range between 5 and 25; a score of 18.75 ((i.e., 75% of total score)) or less was categorised as non-adherence and a score above 18.75 as adherence .
The outcome variable in this study was glaucoma medication adherence scores and the predictive variables were personality trait dimension scores, demographic characteristics (age, gender, educational level), and duration of glaucoma drug use.
Before the commencement of the data collection, a pilot study was carried out to ascertain the reliability and validity of the research questionnaires with a total of 40 conveniently sampled POAG patients. The outcome of the pilot study indicated that most of the participants found the questionnaire suitable, not stressful and easy to comprehend. After the responses were reviewed, some modifications were made to the items the respondents saw as confusing or difficult to comprehend. The Cronbach’s alpha (internal consistency) for all the personality subscales and MARS-5 ranged between 0.86 and 0.96. For participants who could read and write in the English language, the questionnaires were self-administered but for those who could not read and write in English, it was interviewer-administered.
The research was approved by the University of Cape Coast Institutional Review Board (UCCIRB/CHAS/2018/47) and the study procedures adhered to the prescribed guidelines in the Declaration of Helsinki for research involving human subjects. Consent forms including local language versions were issued or read out to each participant to sign or thumb-print before enrolling them onto the study. Prior to issuance of consent forms, the rationale and purpose of the study were explained to each participant in the language they understood best. Also, permission was obtained from the management of the eye care facility before the commencement of the study. The patients were assured of confidentiality and anonymity as no names were included in the data recording.
All data were analysed using IBM SPSS version 23.0. The data were summarised as counts and percentages for categorical variables. Means adherence scores across demographic variables were initially explored using a one-way Analysis of Variance (ANOVA). Pearson’s correlations were used to ascertain the direction and strength of relationship between the various personality trait dimensions and medication adherence scores. Subsequently, a forced entry multiple linear regression model was run to assess how the various personality trait dimensions and other independent variables could predict adherence to glaucoma treatment. The level of significance was set at p ≤ 0.05.