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

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

Understanding Prescriptions  

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

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

Myopia (Short-sightedness)

Hyperopia (longsighted)

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

Correcting Astigmatism

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

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.

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

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

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

BVD continued Why do we care? If a +15.00 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

Rx Summary

Any (Easy) Questions?

What Is a Low Vision Assessment Andrew Miller Lead Optometrist

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.

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

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

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

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

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)

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)

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

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

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

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

Accommodation Generally Bigger is Better Simplest Magnifier = hold something closer

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