Diagnosis & Management of Glaucoma R Ramakrishnan, SR Krishnadas, Mona Khurana, Alan L Robin
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PART 1
1Glaucoma—Basics
  1. Glaucoma in Developing Countries
  2. Epidemiology of Glaucoma and the Role of Glaucoma Screening in Diagnosis
  3. Natural History of Glaucoma
  4. Genetics of Glaucoma and Its Future
  5. Pathogenesis of Optic Nerve Head Changes in Glaucoma
  6. Clinical Trials in Glaucoma
    • Overview of Major Glaucoma Clinical Trials
    • What have We Learnt from the Clinical Trails in Glaucoma?
  7. Prevalence of Glaucoma in India and the World
  8. Vascular Factors in Glaucoma
  9. Aqueous Humor Dynamics
  10. When and How does Glaucoma Produce Visual Disability?
    2

Glaucoma in Developing Countries1

R Ramakrishnan
CHAPTER OUTLINE
  • ❖ Background and Current Situations
  • ❖ Glaucoma in Developing Countries Like India
  • ❖ Monitoring Mechanism and Latest Technology
  • ❖ Research Areas
 
BACKGROUND AND CURRENT SITUATIONS
India was the first country to launch the National Programme for Control of Blindness in 1976 with the goal of reducing the prevalence of blindness. Of the total estimated 45 million blind persons (Va < 3/60) in the world, 7 million are in India. As per information available from various studies, there are an estimated 12 million bilateral blind persons in India with visual acuity < 6/60 in better eye of which nearly 7 million are with visual acuity < 3/60 in better eye. Recent survey (1999–2001) in 15 district of country, indicated that, 2.5 million of 50 plus population is blind (visual acuity < 6/60).1,2 Main causes of blindness in the age group of 50 plus population are as follows:1
  1. Cataract: 62.6%
  2. Refractive errors: 19.7%
  3. Glaucoma: 5.0%
  4. Others: 5%
  5. Postsegment disorders: 4.7%
  6. Surgical complications: 1.2%
  7. Corneal blindness: 0.9%
Among the emerging causes of blindness, Glaucoma needs special attention. Prevalence of glaucoma is estimated to be 4 percent in population aged 30 years and above while childhood blindness due to glaucoma is 3 percent.
Two studies from South India, the Andhra Pradesh Eye Disease Study and Vellore Eye Study (VES) from an urban population of Vellore report the prevalence of primary open angle glaucoma, to be 2.56 percent at Hyderabad and 0.41 percent at Vellore respectively while prevalence of angle closure glaucoma in Andhra Pradesh eye study was 1.1 percent and in VES 4.32 percent.3–5 According to the Aravind Comprehensive Eye Survey (ACES) prevalence of any glaucoma in rural population of South India was 2.6 percent.6
The prevalence percentages in different types of glaucoma according to Aravind Comprehensive Eye Survey are given in the Box.
Also, data from this study, suggests that there is no particular cut off point for IOP, beyond which glaucoma develops, although, increasing IOP is a significant risk factor for glaucoma.
  1. Overall prevalence of primary open angle glaucoma was 1.7%
  2. Prevalence of POAG among aged 40 to 60 years was 0.7%. One fifth of those with POAG had blindness in one or both eyes from glaucoma
  3. PACG—0.5%
  4. Secondary glaucoma (excluding Pseudoexfoliative Glaucoma)—0.3%
The National Programme for Control of Blindness, though, being implemented since last 25 years has not been developed as comprehensive eye care program and this has lead to a delay in the detection and management of patients with glaucoma.7 Major constraints in developing a comprehensive eye care program are:
  1. Lack of political backing
  2. Overemphasis on cataract: Skills required in diagnosing and managing glaucoma need to be acquired during residency. These facilities are available at few tertiary level institutes only. Training of eye 4 surgery in this field has been inadequate. It is imperative to train all ophthalmologists in this field.
  3. Inequitable distribution of eye surgeons: There are 8500 ophthalmologist in India but there is wide disparity between urban and rural areas. Eye surgeon population ratio varies from 1:20,000 in urban area to 1 in 2,50,000 in rural area. This disparity has lead to significant differences in services offered/sought by the public.
  4. Suboptimal utilization of human resources: It is estimated that, 50 percent qualified eye surgeons are nonoperating surgeons.
  5. Inadequate number of paramedical eye care personnel: While, desired eye surgeon—paramedic ratio should be 1:3 to 1:4, this ratio is less.
  6. Suboptimal coverage: Since, advanced ophthalmic services for early diagnosis of glaucoma and its management is mainly restricted to urban/semiurban areas, the geophysically remote and socioeconomically backward population remains underserved.
  7. Lack of public awareness: Prevention is always better than cure and prevention can only be done if the general public is aware of the early symptoms and signs of glaucoma. The fact, that population doubling is expected every 35 years, it is estimated that approximately 19.5 million of our population will have glaucoma in urban India till 20208 (This does not take into account the effect of increasing life expectancy). The magnitude of the problem by year 2020, along with all the present constraints forces us to formulate adequate strategies for early diagnosis and management of glaucoma. Because of the asymptomatic nature and lack of awareness about the disease, many individuals with the problem are not diagnosed earlier leading to a delay in its management.
 
GLAUCOMA IN DEVELOPING COUNTRIES LIKE INDIA
 
Burning Issues
  1. Lack of awareness.
  2. Silent and asymptomatic nature of the disease.
  3. No permanent cure as it can only be controlled.
  4. Life long treatment and follow-up.
  5. Treatment is expensive.
  6. Whatever is lost is permanent and irreversible.
  7. Inadequate infrastructure and manpower.
  8. Unequal distribution of ophthalmologists.
 
Strategies
 
Future Plan of Action
  1. Revamping medical education: Upgrading the undergraduate and postgraduate courses to keep pace with diagnosis and management of glaucoma. Apart from upgrading the medical education, existing ophthalmologists should also be trained in this field.
  2. Ensuring optimal utilization of human resources.
  3. Improving quality of services by adopting and enforcing standard ophthalmic procedures and maintain high quality of preoperative, operative and postoperative services.
  4. Opportunistic screening programmes at eye care institutions for all persons more than 35 years and those with family history of glaucoma.
  5. Community-based referral by multipurpose workers of all persons with symptoms and signs of glaucoma (All individuals with diminution of vision, haloes, frequent change of glasses, night blindness, ocular pain, family history of glaucoma).
  6. Tonometry and fundus examination at eye camps.
  7. Most important of all, increasing public awareness about glaucoma especially periodical ophthalmic examination which includes tonometry, gonioscopy and fundus examination of patient more than 35 years, family history of glaucoma on similar lines as regular blood pressure and blood sugar check-up.
 
Objectives and Targets
  • Early diagnosis and management of glaucoma
  • To screen all patients above 35 years who attend eye clinics
  • Screening eye camps for glaucoma.
 
Areas which Need More Emphasis in Action Plan
  1. Glaucoma should be given due importance in the program.
  2. Eye care services need to be strengthened in difficult, underserved and backward areas.
  3. NPCB should keep pace with latest technological advances within available resources keeping in mind, the cost effectiveness of new interventions.
  4. Equipment and supplies: Frequency doubling perimetry and Nd:YAG laser should be provided at distric hospitals and automated perimetry, Nd:YAG and argon laser at medical colleges.
 
Advocacy and Public Awareness
To strengthen advocacy and generate public awareness, following activities are proposed under vision 2020 initiative.9
 
National and State Level
  1. Political commitment
  2. Putting up blindness control (due to various causes which includes glaucoma) on the agenda of Central5 Council of Health and Family Welfare where Union and State Health Ministers pass resolution on health care.
  3. Constitution of a working group at national level with members from government, NGOs and other funding agencies.
  4. Frequent press releases and articles in leading newspapers of the country.
  5. Increased frequency of broadcast and telecast of messages on eye care to generate public awareness.
  6. Print media: Quarterly newsletters, articles in scientific journals and development of prototype print materials.
  7. Introduction of topics on eye care in school curricula.
  8. Distance education modules for children as well as for paraprofessionals.
  9. Involvement of professional organization like AIOS, IMA, etc.
 
District Level
  1. Strengthen District Society's functioning and representation from NGOs and the community.
  2. Public awareness activities to meet local needs.
  3. Strong interpersonnel communication through village based link workers and community workers.
  4. Motivation and involvement of village level committees, locally elected bodies, grass root NGOs, women groups, formal and nonformal leaders and other active community leaders would be necessary for enhancing coverage in the underserved areas.
  5. Multisectoral approach particularly involving department of education, social welfare and media. Regular CMEs should be organized for Practicing Ophthalmologists, Family Physicians, Voluntary organization like Rotary, Lions club, etc.
 
Development Issues
Unlike most of the other disease states, glaucoma is not one disease entity, but a composite mixture of different pathologies: POAG, angle-closure glaucoma (ACG), secondary glaucoma, as well as congenital glaucoma. Thus, establishing a uniform case definition is not possible. Therefore it becomes necessary to decide which condition needs to be screened.
The next problem relates to actual diagnostic criteria for diagnosis of any of the glaucomas. Though, increased IOP is a major risk factor for development of glaucoma it is seen, that glaucomatous damage occurs even at lower IOP values. On the other hand, increased IOP may not cause any damage in certain individuals. So, taking a single IOP measurement may not be of very helpful in actually labeling an individual to be having glaucoma.
Next, direct ophthalmoscopy can also give rise to high percentage of false positive and negative results.
Mass visual field testing has been shown to be a potentially accurate and efficient means for screening by some authorities, but 40 percent nerve fibers may already be lost by the time, a functional field defect is detected. This means, that, the disease would not be actually detected in the early presymptomatic phase at which damage may be reversible.
All these aspects point towards a pessimistic view of instituting a glaucoma screening program. So, to screen for glaucoma, one should include the above three tests for the screening. However not only, is this a costly venture, it has resource implications. Available personnel to undertake such testing are limited. Moreover, to screen for angle closure glaucoma, Gonioscopy facilities should be available at secondary level at least.
 
Treatment Modalities
Apart from basic diagnostic methods, clear guidelines on treatment policies will have to be established. Compliance and cost of treatment also need to be considered for this purpose. It is seen that medical treatment may not be a feasible alternative for most populations in developing countries like ours, especially for those residing in rural area, keeping in mind, the high possibility of non compliance among them. Certain studies have been done to compare efficacy of different treatment modalities including Medical treatment, Laser Trabeculoplasty and primary Trabeculectomy. These studies, showed, that primary trabeculectomy had the best results. So, it may be best to provide primary trabeculectomy as the treatment of choice especially in developing countries like India.
To summarize, for effective screening, it is necessary to perform tonometry and fundus examination in eye camps. If required, visual fields screening can be done by using the frequency doubling perimetry. Depending on the clinical assessment, either medical or surgical treatment can be considered as the treatment of choice keeping in mind, the high rate of noncompliance.
 
MONITORING MECHANISM AND LATEST TECHNOLOGY
Clinical evaluation of optic disc and visual field are critical in glaucoma diagnosis and both should be monitored to determine whether glaucoma is stable or progressing.
 
Examination of Optic Disc
Following points should be considered while examining optic disc: Optic nerve head examination should include determination of optic disc size. One of the ways it can be done is using 5° aperture of a direct ophthalmoscope.
  1. Vertical and horizontal diameter of optic nerve head and horizontal6 and vertical cup disc ratio should be determined with a slit lamp using 90D lens or 78D lens.
  2. When examining the optic nerve head, physicians should consider the “ISNT” rule, which means that, thickest part of a healthy neuroretinal rim (NRR) is located in inferior quadrant, followed by superior, nasal and temporal quadrants. If NRR thickness does not follow ISNT rule, then, optic nerve head must be damaged by glaucoma. The ISNT rule is independent of optic disc size so it applies to small, normal and large optic disc.
  3. Color and contour of neural rim tissue should be examined.
  4. Pallor of neural rim tissue exceeding the degree of cupping indicates that a nonglaucomatous optic neuropathy must be present.
  5. Presence or absence of an optic disc hemorrhage, should also be assessed, because, presence of disc hemorrhage is a negative prognostic factor for patients with glaucoma.
  6. Finally, reproducible and quantitative assessments of retinal nerve fiber layer (RNFL) and Optic disc could be obtained with the GDx–VCC, OCT or HRT at least in tertiary care centers.
 
Central Corneal Thickness Measurement
Central corneal thickness measurement (CCT) with pachymeter is also important in diagnosis of glaucoma. A high CCT (>580 μ) results in an overestimation of actual IOP, whereas a low CCT (<500 μ) results in underestimation of actual IOP. Patients with thin corneal and high IOPs have a higher risk of developing glaucoma than patients with thicker corneas.
 
Visual Field Testing
Standard automated perimetry (SAP) has been used to evaluate visual field in glaucoma. The Swedish interactive threshold algorithm (SITA) is the most recent advance in SAP. It reduces test duration, which in turn reduces patient's fatigue. This may improve the accuracy of clinical perimetry.
Two newer perimetry techniques include frequency doubling perimetry (FDP) and short wavelength automated perimetry (SWAP). FDP may detect glaucomatous visual field defect earlier than SAP. The Humphrey matrix (Carl Zeiss Meditec) is a new FDP instrument that allows for a more detailed evaluation of visual field. Also, it may be used to monitor for visual field progression. One time SWAP can detect the onset of glaucomatous visual field loss earlier that SAP in patients with ocular hypertension. However, SWAP test duration is long and interpreting test results is difficult due to flaw in normative database. Also, cataracts may affect results of SWAP. SITA-SWAP has a shorter test duration and may be helpful in early glaucoma diagnosis.
 
RESEARCH AREAS
Apart from the various diagnostic methods available, as mentioned earlier, there are certain ongoing advances in the early diagnosis and management of glaucoma.
While IOP lowering remains the only proven strategy for preventing visual loss in glaucoma, scientific advances are anticipated over the next 5 to 10 years that may lead to use of neuroprotective agents in the near future.
The oral NMDA antagonist memantine is the first neuroprotection drug to treat Alzheimer's disease. Various interventions tested in preclinical and clinical studies of glaucoma are yielding some encouraging results.
The development of neuroprotective glaucoma drugs that are able to protect the optic nerve independent of IOP lowering is an important goal because recent national institutes of health sponsored glaucoma clinical trails show that some patients experience disease progression despite seemingly adequate IOP reduction. A series of second generation memantine derivatives called nitromemantines are also currently in development and may prove to have even greater neuroprotective properties than does memantine.
 
 
Low Visual Aids
Provision of low visual aids to individuals who have already suffered severe glaucomatous damage can rehabilitate them socially and to some extent, financially.
 
CONCLUSION
For an effective screening, diagnosis and management of glaucoma, following facts should be considered:
  1. Glaucoma being an important cause of irreversible blindness, can be taken care of, to some extent if, we as a clinician or field worker, are well trained in recognizing early symptoms and signs of glaucoma. For this, certain strict measures have to be taken to train individuals involved in community's health.
  2. Also, in present scenario, it is imperative that our medical curriculum should include intensive training in this field both medical as well as surgical.
  3. A strong political commitment.
  4. Provision of adequate equipment at district hospitals and medical colleges.
  5. Screening of all patients > 35 years, patients with diabetic retinopathy and patients with family history of glaucoma, in eye camps.
  6. Also, mandatory fundus examination and tonometry at eye7 camps and if required, visual field examination.
  7. Strengthening our research division especially in areas of neuroprotection, early diagnosis with better visual field analysis and most importantly, in areas of low visual aids.
  8. Most important of all, creating public awareness about the disease.
The above factors along with a combined effort and strong will power can certainly tackle this problem to a large extent and prevent needless blindness.
REFERENCES
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  1. Dandona L, Dandona R, Srinivas M, et al. OAG in an Urban population in Southern India. Ophthalmology 2000;107:1710–6.
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  1. Quigley HA, Broman AT. The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol 2006;90:262–7.
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