«Provisioning Ophthalmic Care for Remote Rural Indian Populations Zeena Johar* November 2010 * President IKP Centre for Technologies in Public Health ...»
for Remote Rural
IKP Centre for Technologies in Public Health
The estimated prevalence of blindness (also refer Annexure-1) in 1990 ranged from 0.08% of children
to 4.4% of persons aged over 60 years, with an overall global prevalence of 0.7%. As shown in Fig. 1
of the estimated 45 million cases of blindness by 1996, approximately 60% were due to either cataract (16 million people) or refractive errors. A further 15% were due to trachoma, vitamin A deficiency or onchocerciasis, with another 15% due to diabetic retinopathy or glaucoma. The remaining 10% of cases were attributable to age-related macular degeneration and other diseases. In view of the proportion of treatable eye diseases or treatable causes of blindness, such as cataract, trachoma, onchocerciasis and some eye conditions in children, it was estimated that 75% of all blindness in the world could have been avoided. (VISION - 2020 Global Initiative for the Elimination of Avoidable Blindness Action Plan 2006 - 2011, 2007) (Blindness in the Elderly, Editorial, 2008) Figure 1: Global causes of blindness due to eye diseases and uncorrected refractive errors (VISION Global Initiative for the Elimination of Avoidable Blindness Action Plan 2006 - 2011, 2007) The risk factors for loss of vision are age, gender, poverty, and poor access to health care. It is estimated that more than 82.2% of all blind individuals are 50 or older. The burden for visual impairment accounts for approximately 3% of the total global burden of disease and 9% of total years lived with disability in 2001 (Loss of Vision and Hearing, Disease Control Priorities in Developing Countries, Second Edition, 2006). A comprehensive national assessment of the economic cost of visual impairment conducted in Australia, with five principal eye conditions – cataract, agerelated macular degeneration, glaucoma, diabetic retinopathy and refractive error accounted for about 75% of all visual impairment (VISION - 2020 Global Initiative for the Elimination of Avoidable Blindness Action Plan 2006 - 2011, 2007). Multiple community based screening (Quigley, Park, ICTPH Vision Strategy Johar (2010) 2|Page Tracey, & Pollack, 2002), eye injury prevention (Luque, et al., 2007), and community based provisioning (American Optometric Association Community Health Centre Committee, Michelle Proser, Peter Shin, 2008) (Vision Centres, 2010) experiences guide towards adopting a comprehensive outlook catering to community ophthalmic needs.
The ICTPH Health Systems (Johar, 2010) strategy aims to facilitate a comprehensive healthcare delivery model for remote rural Indian population. With a unique community based health worker – ICTPH Guide provisioning screeningand preventive healthcare services and a village based nursemanaged Rural Micro Health Centre (RMHC) provides a unique opportunity to explore a multidimensional approach. With individual health at the crux, establishing various preventive, diagnostic and curative interventions aims to achieve better health outcomes. This paper attempts to outline ICTPH’s strategy to integrate primary ophthalmic healthcare services in its unique healthcare delivery model.
Anatomy, Physiology and Pathophysiology of the Eye:
Light waves from an object enter through the cornea, progressing through the pupil, to the crystalline lens eventually converging onto the retina. The small central area of the retina is the macula, which provides the best vision of any location in the retina. Within the layers of the retina, light impulses are changed into electrical signals. Then they are sent through the optic nerve, along the visual pathway, to the occipital cortex at the posterior (back) of the brain. Here, the electrical signals are interpreted or “seen” by the brain as a visual image (Anatomy, Physiology & Pathology of the Human Eye, 1998-2010). Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth.
1. Refractive Errors (also refer Annexure-2) - Myopia, Hypermetropia, Astigmatism and Presbyopia result in an unfocussed image falling on the retina. Uncorrected refractive errors, which affect persons of all ages and ethnic groups, are the main cause of visual impairment. There are estimated to be 153 million people with visual impairment due to uncorrected refractive errors, i.e. presenting visual acuity 6/18 in the better eye, excluding presbyopia. The most frequently ICTPH Vision Strategy Johar (2010) 3|Page used options for correcting refractive errors are: spectacles, the simplest, cheapest and most widely used method; contact lenses, which are not suitable for all patients or environments; and corneal refractive surgery, which entails reshaping the cornea by laser. (VISION - 2020 Global Initiative for the Elimination of Avoidable Blindness Action Plan 2006 - 2011, 2007) The steps in the provision of refraction services are (VISION - 2020 Global Initiative for the Elimination
of Avoidable Blindness Action Plan 2006 - 2011, 2007):
Case Detection: Identification of individuals with poor vision that can be improved by correction;
Eye Examination: Identify coexisting eye conditions needing care;
Refraction: Evaluation of the patient to determine the correction required;
Dispensing: Provision of the correction, ensuring a good fit of the correct prescription; and Follow-up: ensuring compliance with prescription and good care of the correction, repair or replacement of spectacles if needed.
A. Spherical Refractive Errors Myopia (nearsightedness) is a refractive defect of the eye in which collimated light produces image focus in front of the retina when accommodation is relaxed. For those with myopia, far away objects appear blurred and near objects appear clearly. Eye care professionals most commonly correct myopia through the use of corrective lenses, such as glasses or contact lenses. It may also be corrected by refractive surgery, but this does have many risks and side effects. The corrective lenses have a negative optical power (i.e. are concave) which compensates for the excessive positive diopters of the myopic eye. A diagnosis of myopia is typically confirmed during an eye examination by an ophthalmologist, optometrist or orthoptist. Frequently an autorefractor or retinoscope is used to give an initial objective assessment of the refractive status of each eye, then a phoropter is used to subjectively refine the patient's eyeglass prescription.
Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short or the lens cannot become round enough), causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance. People with hyperopia can experience blurred vision, asthenopia, accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus.
Presbyopia is a condition where the eye exhibits a progressively diminished ability to focus on near objects with age. Presbyopia's exact mechanisms are not known with certainty; the research evidence most strongly supports a loss of elasticity of the crystalline lens, although changes in the lens's curvature from continual growth and loss of power of the ciliary muscles (the muscles that bend and straighten the lens) have also been postulated as its cause. Like gray hair and wrinkles, presbyopia is a symptom caused by the natural course of aging. The
B. Cylindrical Refractive Errors:
Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to
an irregular or toric curvature of the cornea or lens. There are two types of astigmatism:
regular and irregular. Irregular astigmatism is often caused by a corneal scar or scattering in the crystalline lens and cannot be corrected by standard spectacle lenses, but can be corrected by contact lenses. Regular astigmatism arising from either the cornea or crystalline lens can be corrected by a toric lens. The astigmatic optics of the human eye can often be corrected by spectacles, hard contact lenses or contact lenses that have a compensating optic, cylindrical lens (i.e. a lens that has different radii of curvature in different planes), or refractive surgery.
2. Cataract is a cloudy area in the lens of the eye. Adult cataracts usually develop very gradually with advancing age and may run in families. (Cataract: MedlinePlus Medical Encyclopedia, 2010) The main non-modifiable risk factor is ageing. Other frequently associated risk factors are injury, certain eye diseases (e.g. uveitis), diabetes, ultraviolet irradiation and smoking. Cataract in children is mainly due to genetic disorders. Adult cataracts are classified as immature cataract -lens has some remaining clear areas; mature cataract -- completely cloudy or opaque lens;
hypermature cataract -- lens tissues are breaking down and leaking through the surface covering, damaging other structures in the eye. Most people develop some mild clouding of the lens after age 60. About 50% of people ages 65-74, and about 70% of those 75 and older have cataracts that affect their vision (also refer Annexure-7). Cataract interventions, primarily surgery has been cited as cost effective as immunization and can significantly and rapidly reduce avoidable blindness. Surgery to remove the opacified lens is the only effective treatment for cataracts.
Neither diet nor medications have been shown to stop cataract formation (Loss of Vision and Hearing, Disease Control Priorities in Developing Countries, Second Edition, 2006).
3. Diabetic Retinopathy: Retinopathy (damage to the retina) caused by complications of diabetes mellitus, can eventually lead to blindness. Small blood vessels – such as those in the eye – are vulnerable to poor blood sugar (blood glucose) control. An over accumulation of glucose and/or fructose damages the tiny blood vessels in the retina. During the initial non-proliferative stage diabetic retinopathy (NPDR), most people do not notice any change in their vision. Some people develop a condition called macular edema – when damaged blood vessels leak fluid and lipids onto the macula. The fluid makes the macula swell, blurring vision. As the disease progresses, severe non-proliferative diabetic retinopathy enters an advanced, or proliferative, stage when blood vessels proliferate (i.e. grow). The lack of oxygen in the retina causes fragile, new, blood vessels to grow along the retina and in the vitreous humour that fills the inside of the eye.
Without timely treatment, these new blood vessels can bleed, cloud vision, and destroy the retina. Regular dilated eye examinations are effective for detection and monitoring of asymptomatic vision-threatening diabetic retinopathy (Cheung, Mitchell, & Wong, 2010).
ICTPH Vision Strategy Johar (2010) 5|Page
4. Glaucoma is a disease in which the optic nerve is damaged, leading to progressive, irreversible loss of vision. It is often, but not always, associated with increased pressure of the fluid in the eye. Ocular hypertension† (increased pressure within the eye – above 21 mmHg or 2.8kPa) is the largest risk factor. Those at risk are advised to have a dilated eye examination at least once a year. WHO estimates about 60.5 million will have glaucoma by the year 2010 (also refer Annexure-3)
5. Age related macular degeneration is a medical condition which usually affects older adults resulting in loss of vision in the center of the visual field (the macula) because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of visual impairment in older adults (50 years) (also refer Annexure-8). Macular degeneration can make it difficult or impossible to read or recognize faces, although enough peripheral vision remains to allow other activities of daily life.
6. Onchocerciasis, also known as river blindness and Robles' Disease (also refer Annexure-5), is a parasitic disease and the world's second-leading infectious cause of blindness. Onchocerciasis is endemic in 28 countries in tropical Africa, where 99% of infected people live. (Loss of Vision and Hearing, Disease Control Priorities in Developing Countries, Second Edition, 2006)
7. Trachoma (rough eye) is an infectious eye disease, and the leading cause of the world's infectious blindness. Globally, 41 million people suffer from active infection and nearly 8 million people are visually impaired as a result of this disease (also refer Annexure-4). Globally this disease results in considerable disability. Trachoma is caused by Chlamydia trachomatis and it is spread by direct contact with eye, nose, and throat secretions from affected individuals, or contact with inanimate objects, such as towels and/or washcloths, that have had similar contact with these secretions.
Flies can also be a route of mechanical transmission. Untreated, repeated trachoma infections result in entropin - a painful form of permanent blindness when the eyelids turn inward, causing the eyelashes to scratch the cornea. Children are the most susceptible to infection due to their tendency to easily get dirty, but the blinding effects or more severe symptoms are often not felt until adulthood. Most commonly children with active trachoma will not present with any symptoms as the low grade irritation and ocular discharge is just accepted as normal. However, further symptoms may include - eye discharge, swollen eyelids, trichiasis (turned-in eyelashes), swelling of lymph nodes in front of the ears, seeing bright lights, increased heart rate, further ear, nose and throat complications. WHO recommends an integrative approach to trachoma control through its SAFE strategy (surgery, antibiotics to control the infection, facial cleanliness and environmental improvements). (Loss of Vision and Hearing, Disease Control Priorities in Developing Countries, Second Edition, 2006)