Screening Community Optometry

1. Screening

2. Screening
Definition:
• Search for unrecognized disease by means of
rapidly applied test in healthy people.
• Screening includes methods , techniques,
procedures, examinations, tests for early and
rapid detection of unrecognized disease or
defect in apparently healthy persons.

3. Objectives
• Early diagnosis of disease( by periodic
examination)
• Prevention and control of diseases.
• Research ( by screening we know the
incidence rate prevalence rate and
distribution of various diseases).

4. Differences
Screening test
Done on apparently
healthy
Applied to groups
Based on one or cut off
criteria
Less accurate
Not a basis for treatment
Initiative comes from the
health agency
Diagnostic test
Done on those with sick or
indications
Applied to single patient
Based on evaluation of
number of symptoms,
signs or lab tests
More accurate
Basis for treatment
Initiative comes from
patient with complaint

5. • Lead time is the advantage gained by screening
between diagnosis and early detection
• Benefits of program B-A

6. Flow chart
Periodic screening

8. Screening
• Acceptablity
• Validity
• Reproducibility- reliability
• Yield
• Types of screening
• Variations in screening

9. Acceptability
• Since it is for apparently health population it
should be acceptable if not people will not
come forward
• Painful - invasive
• Uncomfortable
• Embarrassing
Not suitable for screening

10. Screening
• Validity measure the accuracy of the
screening.
• Indicators for validity include
– Sensitivity
– Specificity
– Positive predictive value
– Negative predictive value

11. Validity
• Sensitivity is the ability of the test to detect disease
in those who actually have it
• Specificity is ability of the test to detect the absence
of disease in those who actually do not have it.
• +ve predictive value is the probability of the persons
have disease if test result is positive( true +ve)
• -ve predictive value it the probability if the persons
will not have disease if the test is negative.( true –ve)

12. Validity
• False negative: having the disease but the
screening does not detect it.
• False positive: Disease not present but
screening shows presence of the disease.

13. The 2x2 table - validating the screening test

14. Reproducibility
• Reliability is the precision or repeatability of
the test i.e the ability of the test to give same
results.
– To avoid : Intra observer variation, inter observer
variation.
• Technical error – Calibration of devices
• Biological variation – e.g. diurnal variation of
IOP etc.

15. Yield
• It is the amount of unrecognized disease
detected by screening test or the number of
previously unrecognized cases identified by
the test
• Yield is affected by sensitivity and specificity
of the test.

16. Types of screening
•Mass screening
– Less Efficient
•Select screening
– High risk screening – infectious disease
– More efficient and good yield
•Multiphase screening
•Multipurpose screening

17. Variations in screening
• Biological Variation: Seen as part a of
reproducibility
• Mechanical Variation: Technical Errors etc.
• Observer Variations
– Intra-Observer variation: Same observer at
different occasions/ subjects there is variation
– Inter-Observer: Between observers there is
variation
• Validity of test ( seen under validity)

18. Uses of Screening
• Case Detection
– Prescriptive screening where people are screened for their
own benefit. Looking for unrecognized disease
• Control of Disease
– Prospective screening, where people are screened for
benefit of others to prevent spread
• Research purposes
– Understand natural history of disease etc.
• Educational Opportunities
– Creating public awareness
– Educating health professionals

19. Criteria for screening
• It should be a health problem
• Lots of people should be involved
• There should be a latent disease with early
asymptomatic stage
• Natural history of the disease must be
understood .
• There must be a test to detect the disease

20. Criteria for screening
• There must be facilities for confirmation by
correct method of test
• There should be an effective treatment
• The program should show early treatment
reduces mortality
• Advantage the people are going to get by the
expenditure- cost effectiveness
• High yield

21. Iceberg Phenomenon
• Is equivalent of the screening test.

22. The pyramid and iceberg of disease
1. Diseased, diagnosed & controlled
2 Diagnosed, uncontrolled
3 Undiagnosed or wrongly
diagnosed disease
4. Risk factors for disease
Diagnosed
disease
Undiagnosed or
wrongly diagnosed disease
5. Free of risk factors

23. Screening in Community
Optometry

24. Fundus Photo
56/F, BCVA is 6/6, N6 in
both eye
AS: Early lens changes
PS: RE: LE is is normal

25. Screening for Leading causes of VI
• Vulnerable population
– Children
– Adults above the age of 40 years

26. Screening
Invasive / Non-Invasive
•OSDI questionnaire / McMonnies for Dry eye
•Diabetic Risk Score
•Glaucoma Risk Score

30. Quiz Time again
45/M, BCVA 6/6, N6, AS: WNLs

33. Leading causes of Blindness
• Cataract
• Uncorrected Refractive errors
• Childhood blindness
• Glaucoma
• Diabetic Retinopathy

34. Common Terms
• RAAB
– Rapid assessment of avoidable blindness
• RAVI
– Rapid assessment of vision impairment
• RACSS
– Rapid assessment of cataract surgical services
• RARE
– Rapid assessment of refractive error services

35. URE/ Childhood Blindness
• Age group for screening: 3-5 years
• VA – pin hole
• Stereo Acuity
• CTs
• Hirschberg Reflex
• Some times autorefractometers
• Yield and validity will depend on the
prevalence rates

36. Glaucoma Screening
• IOP
• Direct ophthalmoscopy for CDR
• Chamber Angle
Refer for diagnostics
✔ IOP above 21mm/Hg
✔ CDR more than 0.4
✔ Asymmetrical cupping more than 0.2
✔ Thinning of neuroretinal rim
✔ Blood vessels on disc

37. Cupping

39. Hemorrhage

41. Diabetic Retinopathy
• VA
• Non Mydriatic Fundus photography
• Tools like CARA and other software available
• Grading scales
• ETDRS

42. DR