Reading Material for the Prevention of Blindness Workshop


Infrastructure and Appropriate Technology



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Infrastructure and Appropriate Technology

Infrastructure and appropriate technology development is the third essential component of the Global Initiative. Standards for the availability of eye beds, refraction facilities, basic eye medicines, etc. will be applied to make sure that the availability, access, utilisation and coverage of basic eye care will be at least 90% to all populations in the year 2020.

With regard to appropriate technology development, emphasis will be put on the sustainable use of modern technology, making use of local production in developing countries whenever appropriate. The particular fields of interest concern instruments and consumables for cataract surgery, basic eye examinations, trichiasis surgery, glasses and other optical devices, as well as computers and other communications systems for effective management and co-ordination of work.

The Global Initiative is still in its early planning phase, but there is a clearly recognised need for a global awareness campaign, to sensitise decision-makers and health care providers as to the rationale and great benefits of blindness prevention. The future scenario of a doubling of world blindness by the year 2020, unless more preventive action is taken, is unacceptable from a humanitarian point of view, and would have far-reaching socio-economic and developmental consequences. This is why a strengthened partnership between all those working for blindness prevention is essential for optimal utilisation of resources available today and in the future.



CATARACT SURGICAL COVERAGE: An Indicator to Measure the Impact of Cataract Intervention Programmes

http://www.jceh.co.uk/journal/25_3.asp

Hans Limburg MD DCEH
Chief Adviser DANPCB
A1/148 Safdarjung Enclave
New Delhi 110029
India

Allen Foster FRCS FRCOphth
Senior Lecturer

International Centre for Eye Health

11-43 Bath Street
London EC1V 9EL, UK

Aim
To describe Cataract Surgical Coverage (CSC) as an indicator to measure the impact of cataract intervention programmes.
Methods and Materials
Cataract Surgical Coverage, both for ‘eyes’ as well as ‘persons’, was calculated from community based surveys conducted in 19 rural districts in the south-west and one urban district in the north-west of India.
Results
Cataract Surgical Coverage (VA<3/60) ranged from 42% to 68% (for persons)

and from 22% to 45% (for eyes) in 19 districts of Karnataka State. The coverage for males was higher than for females. In Ahmedabad the coverage was high with 93% for persons and 83% for eyes.


Discussion
Together with prevalence data, Cataract Surgical Coverage can provide important information on the impact of cataract intervention programmes. Regular assessment of prevalence and coverage indicators through focused community surveys will reveal trends. Coverage indicators are also important as input data for mathematical models to predict future trends in cataract blindness.
Introduction
Cataract is a public health problem in many developing countries, including India. Traditionally, the cataract intervention programme is evaluated by the number of cataract operations performed per year. In India this has increased from 1.2 million in 1989 to 2.7 million operations in 1996.1 However impressive this increase may be, the figure does not indicate the extent to which the problem of cataract blindness has been reduced.

Two indicators are used to measure impact. First, it can be measured by a change in prevalence of cataract blindness, obtained through community based surveys. Since blindness surveys are costly and lengthy exercises, these are not conducted regularly. In India, a national study was done in the period 1971-74 and a National Survey on Blindness in 1986-89. The variation in prevalence of blindness and visual impairment due to cataract over this period indicates the impact surgical services have had on the magnitude of the problem.

The second indicator to measure impact is Cataract Surgical Coverage (CSC).2,3 This community based parameter compares the proportion who have received surgery (aphakic) to the total, who still need or have had surgery (aphakic + operable cataract) in a certain area. It indicates to what extent the services have covered the needs. It measures the effectiveness of the cataract intervention programme in providing surgical services and, as such, it is an output indicator and does not measure the quality of cataract intervention.
This article presents Cataract Surgical Coverage data obtained through specially designed rapid assessments from two areas in India.
Methods and Materials
We have conducted a simple community based rapid assessment at district level in India, using a systematic random cluster sampling technique. These assessments focused on persons of 50 years and older only. The National Survey on Blindness, India, indicated that of all age-related cataract blindness, 95% occurs in the age group of 50 years and older. Using data obtained from persons of 50 years and older only may slightly underestimate the actual coverage.

The survey methodology and detailed results of the first study have been reported elsewhere.4,5 In 1995, these rapid assessments were conducted in 19 districts of Karnataka State in the south west of India, covering a total of 21,950 persons, and in 1997 in the predominantly urban district of Ahmedabad in Gujarat, covering 1962 persons.6 The main indicators collected through these rapid assessments are the prevalence of bilateral and unilateral blindness or (severe) visual impairment due to cataract and the prevalence of bilateral and unilateral aphakia. From these two statistics the Cataract Surgical Coverage (CSC) can be calculated.

Eligibility for cataract surgery also depends upon visual acuity and varies between institutions and surgeons. It may be better to use the term ‘operable cataract’ and define the level of visual acuity as follows:

- VA<3/60: cataract blind eye or patient

- VA<6/60: severely visually impaired operable cataract eye or patient

- VA<6/18: visually impaired operable cataract eye or patient


The Cataract Surgical Coverage can be measured in two ways, as shown in Figs. 1 and 2:


Fig. 1

Cataract Surgical Coverage (persons) (VA) = (x + y/x + y + z) x 100

in which:

x =

persons with unilateral (pseudo)aphakia and operable cataract in the other eye

y =

persons with bilateral (pseudo)aphakia

z =

persons with bilateral operable cataract




Table 1: Cataract Surgical Coverage from Sample Data on Operable Cataract and Aphakia in 19 Districts in Karnataka (1995)

Category

Condition

VA<3/60

VA<6/60


VA<6/18

z

No. persons with bilateral operable cataract

1,157

2,143

4,345

y

No. persons bilaterally (pseudo)aphakic

558

588

588

x

No. persons one eye aphakic + one eye operable cataract

755

877

988

b*

No. operable cataract eyes*

4,481

6,844

11,511

a**

No. (pseudo)aphakic eyes**

2,401

2,401

2,401

%

first eyes: 76.8% (a-y)/a








%

second eyes: 23.2% y/a













Cataract Surgical Coverage (eyes) a/(a+b)

34.9%

26.0%

17.3%




Cataract Surgical Coverage (persons) (x+y)/(x+y+z)

53.2%

40.1%

26.2%

*b is defined as all eyes with cataract causing an acuity of less than 3/60, 6/60 or 6/18.

**a is defined as all eyes which are aphakic or (pseudo)aphakic, regardless of acuity.



In the equation in Fig. 1, we include bilateral operable cataract which can be defined as either VA<3/60, VA<6/60 or VA<6/18, bilateral aphakia and unilateral aphakia with an operable cataract in the other eye. (Persons with unilateral aphakia, in whom the other eye does not have an operable cataract, are excluded from the equation. Such persons do not have bilateral blindness or (severe) visual impairment due to cataract and are therefore not included in the denominator.)


I

Table 2: Prevalence of Bilateral Cataract Blindness and Cataract Surgical Coverage (VA<3/60) in Eyes and Persons of 50 Years and Older


District

Prevalence bilateral cataract blindness in persons 50+

Cataract surgical coverage in eyes of persons 50+

Cataract surgical coverage in persons 50+




males

females

persons

males

females

persons

males

females

persons

Bangalore-R

3.22%

5.59%

4.33%

36%

28%

32%

55%

43%

47%

Belgaum

2.61%

5.00%

3.79%

42%

39%

40%

65%

57%

60%

Bellary


4.77%

7.19%

6.00%

27%

27%

27%

42%

43%

43%

Bidar

2.69%

5.73%

4.17%

36%

28%

31%

65%

47%

52%

Bijapur

4.14%

8.85%

6.56%

39%

27%

31%

57%

47%

50%

Chickmagalur

1.48%

5.40%

3.37%

51%

35%

42%

81%

55%

67%

Chitradurga

3.94%


8.24%

5.97%

34%

26%

29%

54%

41%

46%































Dak. Kannad

1.27%

7.65%

4.59%

50%

27%

34%

80%

34%

47%

Dharwad

3.77%

6.53%

5.15%

42%

38%

40%

64%

55%

58%

Gulbarga

3.71%

6.99%


5.37%

48%

26%

33%

64%

44%

50%

Hassan

2.10%

3.40%

2.74%

51%

40%

44%

66%

64%

64%

Kodagu

1.88%

1.25%

1.58%

40%

47%

45%

57%

75%

68%

Kolar

5.10%

6.36%

5.70%

24%

20%

22%

47%

38%

42%

Mandya

3.40%

6.00%

4.65%


47%

44%

45%

66%

58%

61%

Mysore

2.00%

6.35%

4.05%

46%

31%

36%

70%

47%

55%

Raichur

4.35%

6.72%

5.58%

24%

29%

28%

46%

50%

49%

Shimoga

3.12%

5.24%

4.12%

44%

35%

39%

66%

56%

60%

Tumkur

5.70%

9.01%

7.24%

44%

33%


37%

56%

49%

51%

Uttar Kannad

3.42%

4.60%

4.00%

41%

44%

43%

50%

60%

57%

Karnataka

3.39%

6.51%

4.93%

40%

32%

35%

60%

49%

53%



n most cases, it is not possible to assess in retrospect whether patients with (pseudo)aphakia were actually blind (VA<3/60), severely visually impaired (VA<6/60) or visually impaired at the time of surgery. For that reason it is important to calculate the cataract surgical coverage for all three levels of visual acuity.

The equation in Fig. 2 gives an indication of the proportion of eyes with operable cataract that have had surgery in the community at a given point in time.




Fig. 2

Cataract Surgical Coverage (eyes) (VA) = (a/a+b) x 100


in which:

a =

(pseudo)aphakic eyes

b =

eyes with operable cataract




The Cataract Surgical Coverage can be calculated directly from the sample data, or from the projected district data, after adjusting the sample data for age and sex. Software has been developed for these rapid assessments. It gives CSC(persons) and CSC(eyes) for VA<3/60, VA<6/60 or VA<6/18, for total population and males/females separately.




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