1. Low Vision Assessments (and understanding prescriptions)
Andrew Miller MCOptom
Focus Birmingham Low Vision Centre

2. What Am I Going To Tell You?
Spectacle Prescriptions
What do the numbers mean
What Is Low Vision
Likely Problems
Low Vision Assessment
Aids Supplied
Other Measurements
Fields
Contrast Sensitivity Function

3. Understanding Prescriptions

4. Components To A Prescription
Sphere (Sph)
Cylinder (Cyl)
Axis
Add
But Don’t Forget
Prism
BVD PD

5. Sphere This tells Us How Long or Short Sighted You Are
Measured in dioptres (D)
Often recorded as DS (+2.00DS)
- means short-sighted
+ means long-sighted
0-4 low
4-10 moderate
10+ severe

6. Myopia (Short-sightedness)

7. Hyperopia (longsighted)

8. Cylinder and Axis Corrects Astigmatism Natural Distortion
Typically to the cornea (can be the lens)

9. Correcting Astigmatism

10. Components To A Prescription
Sphere (Sph)
Cylinder (Cyl)
Axis
Add
But Don’t Forget
Prism
BVD PD

11. Add Corrects Presbyopia Reading Spectacles Adds will blur the Distance
Getting Old (usually age 45+)
Lens Hardens
Reading Spectacles
Adds will blur the Distance
1/Add = working distance (m)
High Adds for Younger low vision potentially increase magnification.

12. Prism Change Position of Object Don’t affect focus
Used to Correct Binocular Problems
Prism Have a Power and Direction Up
Down In
Out

13. PD and BVD Pupillary Distance. Inaccurate PD causes induced prism
How far apart your eyes are
Inaccurate PD causes induced prism

14. BVD Back Vertex Distance Measured in mm.
Usually only important with bigger prescriptions

15. BVD continued Why do we care?
If a lens was prescribed to sit at 10mm slips down the nose to 15mm this changes the prescription by 0.75DS
CAUTION changing BVD can help people read

16. Rx Summary

17. Any (Easy) Questions?

18. What Is a Low Vision Assessment
Andrew Miller
Lead Optometrist

19. What Start with a definition..........
"A person with low vision is one who has an impairment of visual function for whom full remediation is not possible by conventional spectacles, contact lenses or medical intervention and which causes restriction in that person's everyday life". Low Vision Services Consensus Group (1999)
best-corrected visual acuity of worse than 6/18, but equal to or better than 3/60, or visual field of less than 20 degrees.” WHO
Or…
People who still can’t see, even when they have their spectacles on.

20. What Is A Low Vision Assessment
Aim
To improve the quality of life of the patient by enabling them to use their residual vision to its maximum potential
The use of residual vision may be increased by the use of:
Aids
Training
Advice
HARD WORK
Relies on the capacity for the individual to change and accept change

21. What Are the Barriers? Compromise Acceptance Denial Depression
Physical Limitations
Low Vision NOT NO VISION
EXPECTATIONS

22. What a low vision assessment is not.
“Magic”
“Cure”
Patients get out what they put in
As professional I need to
Communicate
Gain trust
Manage expectation
NO ONE DIED FROM A LOW VISION ASSESSMENT

23. What Is Involved in a Low Vision Assessment
Full Assessment of Need...LISTEN+++++
Needs vary tremendously Important we address real need not the perceived need
No point giving a magnifier to someone who wants to bake a cake
Too often services can be tailored to what can be provided rather than what SU needs

24. What Is Involved in a Low Vision Assessment
Set realistic goals that the SU would like to achieve (discuss realism (flying a plane??)
Patient’s Knowledge of eye condition
Full eye examination
Check spectacles
Check for treatable disease
Assess the habitual position (lighting, aids, adaptations)

25. What Is Involved in a Low Vision Assessment
Estimate magnification needs
Trial magnifying Aids and adaptations
Advice & Training
Referral onto others
Rehab/
mobility/
Emotional Support and Counselling (depression and isolation very common)

26. What Things Do We Recommend
Core with central eye disease is the three Bs
BIGGER, BOLDER , BRIGHTER
Too much concentration on bigger
Lighting (most common advice/ most often ignored)
Contrast
Magnifiers are most common
Range of types
Hand
Stand
Electronic
Telescopes

27. Aids Used Frequently: Less Used Brightfield Binoculars Monoculars
Hand Mags
Hyperoculars
Electronic
Less Used
Spectacle Mounted
Stand

28. What Is Different With Children
Cons
Variety of causes
of sight loss
Don’t want to look
different
Lack of compliance
with aids

29. What Is Different With Children
Pros
Often less co-morbidity
Adaptable
ACCOMMODATION
Ability to flex lens inside the eye to bring near objects into focus

30. Accommodation Generally Bigger is Better Simplest Magnifier
= hold something closer

31. Conclusion
Low vision assessment should be a comprehensive assessment of your needs.
No magic cures
All avenues should be explored to help the problems identified
NOT just giving out a magnifier