ABSTRACT Causes of bilateral low vision (BLLV) and bilateral blindness (BLB) were investigated among 720 outpatients aged >45 years in Irbid, Jordan, between July 1999 and October 2000. All received full ophthalmic examinations. BLLV was defined as visual acuity < 6/18 but > 3/60 in the better eye; BLB as acuity < 3/60 in the better eye. The leading cause of BLB and BLLV was cataract. Refractive error was the second major cause of BLLV. Other common causes were diabetic retinopathy and glaucoma. Age-related macular degeneration was the single cause of BLB and BLLV for only 1.6% and 2.8% respectively. A population-based survey of BLB and BLLV in the elderly, yearly vision examinations and an ophthalmic education programme are recommended.

Low vision is a major problem for society that will grow as individuals live longer and survive trauma, illness and other complications. In addition to visual impairment, elderly people are likely to suffer from an increasing number of other disabilities and frailties [1] including loss of employment, retirement, loss of hearing, loss of memory and reduced mobility [2]. After arthritis, chronic visual impairment is the most common complaint among the elderly [3].

The increasing awareness of low-vision problems is evident in the International classification of diseases, 10th revision, which has codes for both blindness and low vision [4]. In this classification, bilateral blindness (BLB) is defined as visual acuity of less than 3/60 (0.05) or corresponding visual field loss in the better eye with best possible correction (visual impairment categories 3,4 and 5 in ICD-10) (USA criteria for blindness is acuity less than 6/60). Low vision is defined as visual acuity of less than 6/18 (0.3) but equal to or better than 3/60 (0.05) in the better eye with the best possible correction (visual impairment categories 1 and 2 in ICD-10) (USA criteria for visual impairment is best acuity of less than 6/12 and better than 6/60) [5].

Many studies around the world, including in both developing and industrialized countries, have collected data on blindness and visual impairment in the elderly. In our study, we investigated the causes of irreversible blindness and low vision not associated with other morbidity in middle-aged and elderly patients in northern Jordan.

Our data were collected among middle-aged and elderly patients (> 45 years of age) complaining of bilateral low vision (BLLV) who attended the ophthalmic clinic at Prince Rashed Bin Al-Hasan Hospital. This hospital is a military referral hospital that covers all of northern Jordan and serves approximately 1.3 million people. Military hospitals in general cover the health needs of 45% of the population in Jordan.

All patients received an ophthalmic examination that included a visual acuity examination using the Snellen E chart and a full eye examination to determine the main causes of visual impairment. In the case of visual acuity of less than 6/18, a pinhole visual acuity test was performed; if there was an improvement of at least one Snellen, line refraction was performed. The full eye examination included slit lamp examination, Goldman applanation tonometry, pupillary reaction to light, mydriatics and funduscopy by direct and indirect ophthalmoscopy and by 78 diopter lens and fluorescein angiogram. BLLV was defined as a visual acuity of less than 6/18 but greater than or equal to 3/60 in the better eye and BLB was defined as visual acuity of less than 3/60 in the better eye. Visual field was not taken into account.

A total of 720 patients > 45 years with BLB or BLLV according to our criteria were selected between July 1999 and October 2000; 348 (48.3%) women and 372 (51.7%) men. Their ages were between 45 and 95 years with a mean of 62.6 years. Of the 720 patients, 532 (73.9%) had BLLV and 188 (26.1%) had BLB.

Table 1 Leading causes of BLLV and BLB in patients

Cataract was the leading cause of both BLLV (39.1%) and BLB (60.1%). The second most common cause of BLLV was uncorrected refractive error (17.1%), followed by diabetic retinopathy (14.5%) and glaucoma (11.3%) (Table 1). Diabetic retinopathy (13.3%) and glaucoma (8.5%) were the other main causes of BLB (Table 1).

Table 2 Comparison of the leading causes of blindness in selected countries

Age-related maculopathy caused BLLV in only 15 patients (2.8%), all of whom were aged 70 years or older. Three patients (1.6%) had age-related macular degeneration (ARMD) as a cause of BLB; all of these were over the age of 75 years.

Ocular disorders in the elderly have become more important because of increased longevity and demand for good vision [6]. Data on blindness and visual impairment in Jordan are limited compared with some other countries where large-scale studies have been conducted.

Cataract is the most prevalent eye disease in the world and is a major cause of visual loss in developing as well in industrialized countries [7]. Other major eye diseases in the elderly include ARMD, glaucoma and diabetic retinopathy [5–10]. In our study the major cause of BLLV and BLB was cataract, which is a treatable condition simply by cataract extraction and intraocular lens insertion. In Africa and Asia, cataract has been reported to be the main cause of blindness and low vision [11].

Uncorrected refractive error was the second most common cause of BLLV in our study group (91 of 532 patients, 17.1%). This too can easily be corrected with the provision of appropriate optical services.

Diabetic retinopathy was the second most common cause of BLB and the third most common cause of BLLV in our study group. Diabetic retinopathy is considered to be a preventable cause of blindness with early diagnosis [6] and laser treatment is remarkably effective for diabetic maculopathy.

Glaucoma is also a largely preventable cause of blindness. It accounted for 11.3% of our patients with BLLV and for 8.5% of our patients with BLB. In a study in the Republic of Ireland, glaucoma was the most common cause of blindness for the age group 65–79 years [12].

A similar study to ours was conducted at the King Hussein Medical Centre in Jordan by Tahat et al. who found that the leading three causes of blindness in Jordan, independent of age, were cataract (30%), advanced diabetic retinopathy (21%) and all forms of glaucoma [16].

A national survey should be conducted in Jordan for the proper and detailed study of causes of visual impairment for prevention of blindness and improvement of quality of life. The prevalence of blindness and low vision in our study due to ARMD is lower than most other studies conducted in other countries. In most of the patients in our study, both blindness and low vision were treatable (cataract or refractive error) or preventable (glaucoma or diabetic retinopathy). We therefore emphasize the need for establishing a national blindness prevention programme and for routine annual ophthalmic examinations for all patients over the age of 45 years for the early diagnosis and possible prevention of age-specific ocular diseases.