Knowledge of the prevalence and causes of visual impairment (VI) amongst hospital patients is useful in planning preventive programmes and provision of eye-care services for residents in the surrounding communities.
The aim of this study was to determine the prevalence and causes of VI amongst eye clinic patients at Nkhensani Hospital. The relationship between VI and age was also investigated.
Nkhensani Hospital in the Greater Giyani subdistrict municipality, Mopani district, Limpopo Province, South Africa.
Four hundred participants aged 6–92 years were selected for the study using a convenient sampling method. Presenting and best corrected visual acuities (VA) were measured with a LogMAR E chart. Presenting VA (PVA) in the right and left eyes and in the better eye of the patients was used to determine the prevalence of VI, low vision (LV) and blindness. Ophthalmoscope was used to diagnose the eye conditions causing VI amongst participants.
The prevalence of VI based on the PVA in the right eye was 34.8% and in the left eye, the prevalence was 35.8%. There was a significant association between age of the participants and VI in the right and left eyes (
Findings in this study indicate that a large proportion of VI is preventable. Focusing on refractive error correction and surgical intervention for cataract would significantly reduce the burden of VI amongst patients utilising this hospital.
Une connaissance de la fréquence et des causes de déficience visuelle (VI) chez les patients des hôpitaux est utile pour mettre en œuvre des programmes de prévention et des services de soins oculaires pour les habitants des communautés avoisinantes.
Le but de cette étude était de déterminer la fréquence et les causes de VI chez les patients de la clinique ophtalmologique de l'Hôpital Nkhensani. On a aussi examiné la relation entre la déficience visuelle et l'âge.
L'hôpital Nkhensani dans la municipalité du sous-district du Greater Giyani, district de Mopani, province du Limpopo, Afrique du Sud.
Pour l'étude on a sélectionné quatre cent participants âgés de 6 à 92 ans et utilisé une méthode pratique d'échantillonnage. On a mesuré les acuités visuelles présentes et la meilleure acuité visuelle corrigée (VA) au moyen d'un tableau LogMAR E. On s'est servi de la (PVA) dans l'œil droit et l'œil gauche et dans le meilleur œil des patients pour déterminer la fréquence de VI, la vision basse (LV) et la cécité. On a utilisé un ophtalmoscope pour diagnostiquer les conditions oculaires causant la VI chez les participants.
La fréquence de VI basée sur la PVA dans l'œil droit était de 34.8% et dans l'œil gauche elle était de 35.8%. Il y avait une relation significative entre l'âge des participants et la VI dans l’ œil droit et gauche (
les résultats de cette enquête montrent qu'une grande proportion de VI peut être évitée. En mettant l'accent sur la correction des erreurs de réfraction et les interventions chirurgicales pour la cataracte, on réduirait beaucoup le fardeau de la déficience visuelle chez les patients de cet hôpital.
According to the World Health Organization (WHO),
The prevalence of VI has been reported amongst different populations, with cataracts and refractive errors (RE) being reported as common causes. For example, in a population-based study amongst subjects aged 1–91 years of age in Botucatu, Brazil, Schellini et al.
In Nigeria, amongst adults aged ≥ 40 years, Abdull et al.
In a study of RE and VI amongst school-aged children aged 5–15 years in Durban, South Africa, Naidoo et al.
Age and gender have an influence on visual impairment and it has been reported that, in all age groups, prevalence increases with age and women have a significantly higher risk of developing VI than men in every region of the world.
Visual impairment has significant socioeconomic implications. Resnikoff et al.
In a national guideline for the prevention of blindness in South Africa, the Department of Health
Data on the prevalence and causes of VI in South Africa are few and no studies have been conducted specifically in the Mopani district of Limpopo Province. Hospital data have been used by several authors
Nkhensani Hospital is a level 1 district hospital situated in the Greater Giyani subdistrict municipality, Mopani district, Limpopo Province, South Africa. Most people using Nkhensani Hospital are from the rural areas of the Greater Giyani subdistrict municipality. Eye-care services at the hospital are provided by both optometrists and ophthalmic nurses. Patients who needs specialist care are referred to the ophthalmologist at Elim Hospital or Mankweng Hospital who provides subsequent management and feedback. Where necessary, the diagnosis of the ophthalmologist was used to confirm any ocular diagnosis reported in this study.
The study population was the patients attending the Nkhensani Hospital Eye Clinic in Giyani, Limpopo Province, South Africa between August 2012 and March 2013 – an estimated total population of about 3400 patients. Based on this population size, using the Krejcie and Morgan Table,
A LogMAR (log of the minimal angle of resolution) illiterate E acuity chart was used to measure presenting (habitual), pinhole and best corrected VA. A pinhole disc was used to detect if reduced VA was a result of RE or eye disease or another anomaly. Where reduced VA resulted from REs, subjective refraction (lenses providing the best vision were determined by the choice made by the patient, when difference lenses were placed in front of their eyes) was done and the REs and corrected vision value recorded. Direct ophthalmoscope examination was used to examine the external and internal structures of the eye. A digital hand-held tonometer was used to measure the intraocular pressure. A confrontation test was performed to estimate the extent of visual field. Those with eye diseases were referred to the ophthalmic nurse and/or ophthalmologist for further management. In cases where the researcher had doubts regarding diagnoses – such as differential diagnoses of the retinopathies – the diagnosis of the ophthalmologist was used to confirm diagnosis. Visual impairment was based on presenting VA and the WHO classification,
Visual acuity ranges, categories and classification of visual impairment according to the World Health Organization classification.
Snellen VA | VA (LogMAR) | Category | Classification |
---|---|---|---|
≥ 6/18 | 0.0 – 0.50 | 0 | Mild or no VI |
< 6/18 – 6/60 | 0.52 – 1.0 | 1 | Moderate VI |
< 6/60 – 3/60 (6/120) | 1.02 – 1.30 | 2 | Severe VI |
< 3/60 – 1/60 | 1.32 – 1.80 | 3 | Blindness |
< 1/60 – LP† | 1.82 – 3.0 | 4 | Blindness |
NLP† | 4.0 | 5 | Blindness |
Note: Moderate and severe visual impairment constitute low vision.
VA, visual acuity; LogMAR, logarithm of the minimum angle of resolution, VI, visual impairment; †, LP is light perception and NLP is no light perception.
Data were analysed using the descriptive and inferential statistics of the Statistical Package for Social Sciences (SPSS) version 21 (IBM Corp., Armonk, NY 2012). Descriptive statistics (range, mean and standard deviation) were used to describe the cohort and the visual values. The relationship between VI and age was tested for significance using the Chi-squared test; a
Approval to conduct the study was obtained from the University of Limpopo Ethics Committee (MEDUNSA), approval number MREC/HS/63/2012:PG. Permission was obtained from the Limpopo provincial department of health, Mopani district Health Office and the Chief Executive Officer of Nkhensani Hospital. Informed consent was obtained from the participants and parents of the children included in the study after they had been provided with appropriate information regarding the purpose and method of the study.
A total of 400 participants was included in the study, all attending the Nkhensani Hospital Eye Clinic for eye-care services during the period of the study. Their ages ranged from 6 to 92 years, with a mean of 39.5 ± 23.5 years. They comprised 161 (40.3%) men and 239 (59.7%) women.
The prevalence of VI (combined LV and blindness) based on presenting VA in the right and left eyes (
Ages and percentages of participants with various levels of visual status in the right eye based on presenting visual acuity.
Ages (years) | Mild/NVI | Low vision | Blindness | Total VI (%) | |||
---|---|---|---|---|---|---|---|
0 | 1 | 2 | 3 | 4 | 5 | ||
6–18 | 22.0 | 1.5 | 0.3 | 0.3 | 1.0 | 0.0 | 3.0 |
19–35 | 19.5 | 2.8 | 0.0 | 0.3 | 1.5 | 1.0 | 5.5 |
36–59 | 15.0 | 4.3 | 0.0 | 1.5 | 2.8 | 1.5 | 10.1 |
≥ 60 | 8.8 | 7.3 | 0.3 | 1.5 | 6.8 | 0.5 | 16.3 |
Note: Mild and no visual impairment (NVI) (category 0), moderate and severe visual impairment (VI) (categories 1 and 2) constituting low vision and blindness (categories 3–5) are shown in the Table. The total percentage of VI participants is shown in the last column.
Ages and percentages of participants with various levels of visual status in the left eye based on presenting visual acuity.
Ages (years) | Mild/NVI | Low vision | Blindness | Total VI (%) | |||
---|---|---|---|---|---|---|---|
0 | 1 | 2 | 3 | 4 | 5 | ||
6–18 | 20.8 | 1.8 | 0.3 | 0.8) | 1.5 | 0.0 | 4.3 |
19–35 | 18.8 | 2.5 | 0.0 | 0.8) | 1.3 | 1.8 | 6.3 |
36–59 | 15.5 | 5.0 | 0.0 | 1.0) | 2.5 | 1.0 | 9.5 |
≥ 60 | 9.3 | 7.8 | 0.3 | 1.8) | 4.3 | 1.8 | 15.8 |
Note: Mild and no visual impairment (NVI) (category 0), moderate and severe visual impairment (VI) (categories 1 and 2) constituting low vision and blindness (categories 3–5) are shown in the Table. The total percentage of VI participants is shown in the last column.
Ages of the participants and percentage distribution of low vision, blindness and visual impairment (VI) based on the visual acuity in the better eye.
Age (years) | Low vision | Blindness | Total VI |
---|---|---|---|
6–18 | 1.5 | 1.0 | 2.5 |
19–35 | 2.8 | 1.8 | 4.6 |
36–59 | 4.5 | 2.8 | 7.3 |
≥ 60 | 8.3 | 5.3 | 13.6 |
The main causes of VI were UREs, cataract and glaucoma (
The percentage distributions of causes of visual impairment amongst participants (
Visual impairment is an important public health issue since it impairs the QoL and limits the career choices/job opportunities of those affected, thus constituting a socioeconomic burden on society.
The prevalence of VI, LV and blindness were 28.0%, 17.1% and 10.9%, respectively. The main causes of VI were UREs (38.0%), cataract (25.9%) and glaucoma (17.6%). A comparable hospital-based retrospective study
Although REs can simply be corrected with a pair of spectacles, the majority of people in South Africa remain visually impaired because of URE. This may be because of an absence of eye-care personnel, poor accessibility to the services or inability to afford the service cost, especially amongst those living in rural and remote areas.
The significant association between age and VI (
A major limitation of hospital-based studies, including this study, is that they are biased toward those seeking (in this case) eye-care services, hence findings may be higher than would be seen in the population at large. For this reason, the VI prevalence of 28.0% and causes reported here cannot be generalised to the entire district, province or national population. Also, findings should be compared with those in the literature with caution because VI reports in the literature could vary as a result of differences in the ages, study sites or ethnicity of participants as well as the socioeconomic status of the participants. Findings in this study could not be directly compared to the majority of those of the previous prevalence and VI studies because of various factors such as differences in methodology and ages of participants. Also, reports here are based only on presenting, not corrected, VA. Most previous studies on prevalence and causes of VI were population based.
Although a previous hospital-based study on VI in South Africa could not be found in the literature, findings in this study reflect the views of previous population-based studies in the country which found that cataract
It is recommended that the Department of Health prioritise the elimination of REs and cataract if the prevalence of VI is to be reduced in the country. Sustainable programmes toward correction of REs and cataract surgery are needed in Nkhensani Hospital in order to reduce the burden of VI amongst patients receiving eye-care services in the hospital. As glaucoma is the third most common cause of VI in this study, appropriate programmes should be put in place to detect and manage glaucoma cases before they result in visual impairment. Strengthening awareness programmes and screening campaigns (with appropriate screening equipment) in the Giyani subdistrict where this hospital is located will provide an opportunity for identifying potentially blinding conditions before they cause visual loss.
This study indicates that the overall prevalence of VI in this hospital sample is high (28.0%), as is shown in
This article was adapted from a Master of Public Health project by M.M. Maake, University of Limpopo, supervised by O.A. Oduntan.
The authors declare that they have no financial or personal relationship(s) that may have inappropriately influenced them in writing this article.
M.M.M. (University of Limpopo) was responsible for the project design, data collection and analysis, in addition to contributing to the writing of the article. O.A.O. (University of KwaZulu-Natal) supervised the project and contributed to the writing of the article.