Walid Qubain M.D,
Ophthalmologist, Jordanian Royal medical services

Mohammad Al-Droos M.D,
Ophthalmologist, Jordanian Royal medical services

Correspondence:
Al-Droos, MD.
Ophthalmology Department, Royal medical services,
Tafila, Jordan;
droos75@hotmail.com
Tel: 00962-777265101

Introduction

The World Health Organization's (WHO) definition of blindness is a visual acuity of less than 3/60 (20/200, 0.05), and low vision is less than 6/18 (20/50, 0.3) in the better eye with the best-correction giving that. An estimated 45 million people are blind, and an additional 135 million have severe visual impairment^{[1] [2]}. Most blind people live in the developing countries, and in whom blindness is either curable or preventable^[3]. So visual impairment and disability is a worldwide health problem. The causes of visual impairment are complicated and controlling the problem needs to be region specific, which will depend on the data provided by that community. Thus, providing this data is one of the first steps in these communities. There are few published studies about the status of the problem in the Jordanian population, so the study was conducted in a sample of south Jordanian patients to determine the possible causes of vision impairment in this population of the country.

Materials and Methods

All 900 patients with a mean age of 64 years attending the clinic received thorough eye examinations. The examination included measuring uncorrected, and best-corrected visual acuity; subjective (manifest) and cycloplegic refraction; colour vision test; intraocular pressure; examination of the external eye, anterior segment, media, and fundus examination, in addition to an interview about past history of eye diseases, eye trauma, diabetes mellitus, hypertension, previous ophthalmic surgeries and the degree of literacy.

Visual acuity was determined by using a Topcon chart projector (visiontester VT-SE; Topcon Co, Japan) with E letters at a distance of 6 meters. Patient's visual acuity without correction was measured separately for each eye. Then visual acuity was tested with best spectacle correction. Visual acuity was recorded as the smallest line in which the patient could read three letters correctly. If the patient was unable to read the largest E letters in the chart (20/400 E letters) at 4 meters, then finger counting was done at 1 meter. The examiner stood 1 meter away in front of the patient and asked if the patient could see his hand. The examiner slowly waved his hand and asked the participant if he/she could see what the hand was doing. If the patient was able to see the examiner's hand moving, "hand motion" was recorded on the examination form. If the patient could not see the examiner's hand, a penlight was held in front of the patient's eye and he/she was asked if he/she could tell when the light was on or off. If the patient could correctly identify when the light was on, "light perception" was recorded. If the patient was unable to see the light, "no light perception" was recorded.

The International Classification of Diseases 10th edition (ICD10) defines visual impairment as a visual acuity of less than 6/18 (20/60, 0.3) in the better eye with the best correction^[4]. Visual impairment has been divided into blindness and low vision. A visual acuity of less than 3/60 (20/400, 0.05) in the better eye with the best correction has been considered blindness. While low vision has been defined as the best corrected visual acuity of less than 6/18 (20/60, 0.3) but not less than 3/60 (20/400, 0.05) in the better eye.

We determined the cause of visual impairment. Using best judgment, we determined one cause for each eye as the principal cause in either eye. When multiple disorders were present, we attempted to identify the disorder causing the greatest decrease in vision. When two causes appeared to have an equal contribution to visual impairment the primary cause was assigned to the one that was amenable to treatment to restore vision. Cataract was regarded as the main cause of severe low vision if the fundus was obscured by lens changes or if no evident fundus abnormalities were observed in eyes with significant cataract. We analyzed the causes of visual impairment as percentages of the total patients participating in the study.

Of the 900 participants, 540 females end 360 males who were involved in the ophthalmic examination the principle causes of both best corrected and presenting visual impairment are shown in [table 1] and [graph 1] . While the main causes of visual impairment according to the presenting vision were uncorrected refractive errors and cataract, according to the best corrected vision cataract, macular degeneration, and amblyopia were the most frequent primary causes of visual impairment in our patients. In visually impaired people, as a result of uncorrected refractive errors, 48.9% had myopia, 42.2% had hyperopia, and 8.9% had astigmatism.

Table 1. Causes of visual impairment

*Trauma, absent globe, diabetic retinopathy, optic nerve hypoplasia.

Discussion

The burden of visual impairment especially for refractive errors and cataract, in terms of visually impaired person years, is even more significant than we can think, and refractive error visual impairment mostly starts at a young age and probably causes significant economic and social burden to society^[5].

Consistent with other studies, cataract was the leading cause of visual impairment based on best-corrected visual acuity^[6][7][8]. However, refractive errors were the principal cause of visual impairment using presenting visual acuity. Refractive errors are also one of the leading causes of visual impairment in different parts of the world^[9][10][11]. On the basis of presenting vision, as much as 68% of visual impairment in the study patients, is due to cataract and refractive errors that are easily curable. And we have to notice that our study was carried out on a sample of South of Jordan patients with special socioeconomic characteristics so that we cannot extrapolate the results to the whole population of the country. More research in other regions including rural areas is indicated.

This study reports less glaucoma than some other surveys in other countries^[12]. This could be because the visual field examination was not performed, which may result in a potential underestimation.

A higher rate of visual impairment in illiterate people was detected in this study, which could indicate strong association between visual impairment and education. The observed associations show us that we have to find interventional programmes against the treatable visual impairments in this part of the community, stressing those with little or no education as a high-risk groups.

A planned, systematic, educational intervention programme needs to be designed and implemented to reduce the avoidable and treatable causes of visual impairment in the country. The aim must be to improve community awareness on the consequences of undiagnosed and untreated eye disease and how to access primary and secondary eye health care. This would also provide a more effective use of the eye healthcare system.

References