Khalid F Tabbara

Blinding eye diseases remain a highly prevalent and serious health problem in many developing countries. The exact number of blind individuals is riot known. It is estimated that there are 38 million people who have visual impairment and are at risk of becoming blind.

The prevalence of blindness in developing countries is 10-40 times higher than in developed countries and close to three quarters of the world's blindness is either curable or preventable. The majority of blind people on earth reside in the developing nations of Africa, Asia, and Latin America.

The World Health Organization (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. In the eastern Mediterranean countries, there are several studies on the prevalence of blindness. Certain studies were community based prevalence surveys while others included reports on blindness from registries of schools for the blind. The prevalence of blindness in Lebanon is 0.6% and 1.5% in Saudi Arabia! The leading causes of blindness have been determined by information retrieved from registries for the blind in a number of countries. In general, data obtained from hospitals, social security records, or institutions for the blind may give us an idea about the causes of blindness but these sources suffer from certain limitations.

Often excluded from consideration are remote populations, those who do not seek medical advice, unilateral blindness, older individuals, and preschool children.

In countries in the eastern Mediterranean eye diseases have long been recognised as a major health problem. Table 2 shows the lead ing causes of blindness in these countries. In Saudi Arabia, a community based blindness survey was conducted to determine the prevalence of blindness and visual impairment and to assess the prevalence of the major causes of blinding eye disease. A nationwide random stratified, multistage cluster sample was included in the survey. This survey revealed that 1.5% of the population are blind and another 7.8% are visually impaired according to the WHO definition of blindness. The most common causes of blindness in Saudi Arabia were cataract, trachoma, non-trachomatous corneal scars, refractive errors, congenital anomalies, failed medical or surgical treatment, and glaucoma. On the other hand, refractive errors, amblyopia, and trauma were causes of unilateral loss of vision. About 7% of all Saudi Arabians and 42% of those older than 40 years developed cataract and over 3.5% of the population had corneal scars; about half were caused by trachoma. The data presented have demonstrated that eye disease and blindness are important health problems in Saudi Arabia. Over 1.5% of the total population and , over 20% of the population older than 60 years of age were blind. The prevalence of blindness reflects the current and previous status of eye diseases. Recent socioeconomic development in Saudi Arabia and other Arab Gulf countries has greatly influenced the causation of blindness in these countries. For example, the prevalence of trachoma has decreased dramatically over the past two decades. Currently, in urban communities there are practically no cases of active trachoma. This socioeconomic development is less pronounced in other eastern Mediterranean countries.

Causes of blindness
CATARACT
Cataract accounts for half of the blindness despite the fact that the condition is generally curable. The rate of surgery in eastern Mediterranean countries remains low. The provision of widespread cataract surgery delivered in a timely fashion before individuals are visually impaired by this condition may prevent major reduction of blindness and visual loss. A
related disturbing issue is the frequency with which ophthalmic surgery results in intraoperative or postoperative complications. In several eastern Mediterranean countries, the rate of complications following Cataract surgery remains high. Approximately 4% of all blindness in Saudi Arabia was found to be iatrogenic that is, caused by failed medical or surgical therapy. Since the survey was a prevalence survey and not an incidence survey, such complications may represent the previous status of ophthalmic care in Saudi Arabia. The recent introduction of new techniques for cataract surgery, including phacoemulsification, has been started by ophthalmologists in eastern Mediterranean countries. Despite these advances, less than 20% of the cataract surgery in eastern Mediterranean countries is phacoemulsification. This is because of lack of resources in certain areas, the presence of corneal scars, and advanced mature cataracts. This highlights the necessity of adequate recruitment, training, and transfer of technology and skills to surgeons working in this region.

TRACHOMA
Trachoma is uncommon in Lebanon, Syria, and Jordan but is still highly prevalent in the rural communities of Iraq, Saudi Arabia, United Arab Emirates, Qatar, and Oman. Trachoma remains an important cause of blindness and the leading preventable cause of visual disability. Data from several surveys have indicated that trachoma is rapidly waning as a highly endemic disease. The complications of trachoma appear during adulthood. The prevention of blindness and visual impairment from the disease remains a critical issue. Conjunctival scarring with lid deformities and trichiasis leads to major ocular surface complications and corneal scarring. Recognition and referral by local health workers of patients with entropion and trichiasis, especially those with lingering inflammatory trachoma, or their exposed family members are priorities in this context for prevention of blindness.


CORNEAL SCARS
Corneal scars from trauma, infection, or failed medical intervention are also preventable and mostly curable causes ofvisualloss. The difference between tile preservation of vision and a poor visual outcome in these conditions is prompt and skilful management. It is unfortunate to realise that eye banks are available in ony small number of cities in the eastern Mediterranean countries making corneal transplantation a rare procedure because of lack of corneal tissue.


REFRACTIVE ERRORS
Refractive errors are among the leading causes of visual loss in the eastern mediterranean countries. The visual impairment due to refractive errors can be improved by wearing spectacles in the vast majority of cases. In eastern Mediterranean countries, however, individuals are reluctant to wear spectacles. The use of contact lenses has contributed to an increase in the incidence of infectious keratitis. Nerv surgical intervention techniques such as photorefractive keratectomy (PRK), radial keratotomy (RK), and laser in situ keratomileusis (l.ASIK) have been adopted in certain cities in the Middle East. The learning curve of ophthalmologists, however, may have caused certain complications. Complications associated with flap production in LASIK have led to serious complications and corneal scars and visual loss. Infectious keratitis following these procedures has been reported. The transfer of skills and technology to developing countries is sometimes poorly organised.' The rapid development of new instrumentation, new techniques, and new pharmaceuticals has led to serious iatrogenic blindness in many eastern Mediterranean countries. The transfer oftechnology and skills has not been properly cultivated. The rapid transfer without proper training of doctors has led to serious ocular complications and visual loss.

"OVER THE COUNTER" TOPICAL MEDICATIONS
The "over the counter" sale of topical medications such as steroids has led to the loss of vision secondary to steroid induced cataracts and glaucoma. Topical anaesthetic cornealcomplications are also seen in many individuals because of the misuse of topical and aneasthetic eye drops. Folk remedies and homemade eye drop preparations have also led to serious ocular surface complicarion leading to blindness. In rural areas of the Middle East, one may still find homemade remedies and folk medicine that may also lead to loss of vision.

OTHER CAUSES OF BLINDNESS
Certain ocular conditions that are seen in western countries, such as macular degeneration, remain less common in the eastern Mediterranean countries. There are many factors that may contribute to the low prevalence of macular degeneration. The life span of individuals living in eastern mediterranean countries is still less than that of those living in the United States and Europe and, therefore, the prevalence of age related macular degeneration may not be as high as in western countries. Early onset of cataract may prevent light related damage of the macula. The retinal pigment epithclium of dark Skinned individuals may protect against macular damage. The incidence of macular degeneration is known to be significantly less in black than in white people.
Other important causes of blindness are diabetic retinopathy and glaucoma. The socioeconomic development in the eastern Mediterranean countries has led to an acute rise in the incidence of diabetes mellitus. Individuals in these countries for many years had limited intake of sugars and carbohydrates, which may have led to the evolution of a thrifty gene. Sudden change in their dietary habits may have led to hyperglycaemia. The complications of diabetes including diabetic retinopathy have increased dramatically in the past two decades.
Glaucoma remains an important cause of blindness in the eastern Mediterranean countries. Delay in the presentation of patients with ocular hypertension and glaucoma has led to blindness in many countries. In Saudi Arabia, glaucoma was responsible for blindness among 3% of the population above the age of 40 years. Glaucoma is one of the leading causes of blindness and produces irreversible visual damage. Open angle glaucoma is called "the little thief" in Saudi Arabia because blindness may occur despite the lack of symptoms. Painless progressive loss of vision may not be noted by the patient until vision is seriously decreased. Screening programmes and public education are highly desirable for the prevention of blindness from glaucoma. Training programmes should be developed for doctors and other health personnel working in primary health care. Measurements of the intraocular pressure should be a part of the routine physical examination. Diagnostic equipment such as tonometers and ophthalmoscopes should be provided to all health centres. Effective and simple tonometers can be made available. Education of the public about glaucoma, particularly with emphasis on its types and symptoms and its relation to age and genetic factors, is imperative. People who are above the age of 35 years, especially those with family history of glaucoma, should have ophthalmic examination and tonometry.

Childhood blindness
Several reports on childhood blindness in eastern Mediterranean countries have appeared in the literature over the past two decades. The major causes of blindness in children are shown in Table 3. In general, genetic causation of childhood blindness is frequent in developed countries, whereas nutritional and infectious factors are more common causes of childhood blindness in developing countries. In many eastern Mediterranean countries, however, the causes of childhood blindness are changing.