Eschenbach Low Vision Training Program

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Marion Cobb
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1 Eschenbach Low Vision Training Program Module 5: Magnifying Spectacles Edited by: Thomas Porter, OD Asst. Professor & Director Low Vision Service St. Louis University, Dept. of Ophthalmology Eschenbach Optik Optik of America, of Inc. Inc. (Ver. (Ver. 1) 1)

2 The Seven Steps to Dispensing Low Vision Aids 1. Make sure the patient is under the current care of an eye doctor and has a current refraction 2. Identify the patient s visual goals 3. Determine the magnification required 4. Demonstrate the impact of illumination 5. Select the appropriate vision aids for the goals identified 6. Train the patient in the use and care of the chosen vision aid 7. Schedule a follow-up visit

3 Magnifying spectacles are ideal for tasks such as reading allow users to have their hands free work based on the principle of relative distance magnification

4 What they are How they work How to use them What types are available What are they made for

5 What is a magnifying spectacle? Any eyewear that allows wearers to hold objects close

6 How do magnifying spectacles work? y AB CD EF AB CD EF y y = 1/3 y y / y = 3x

7 There are two different design types in magnifying spectacles: Those designed for binocular viewing: - Prismatic reading glasses Diffractive binocular eyewear - Standard reading glasses Those intended for monocular usage: - Microscopic spectacles - Diffractive microscopic spectacles

8 Prismatic Reading Glasses Conventional eyewear - front view Prismatic eyewear - front view Conventional eyewear - top view Prismatic eyewear - top view

9 Prismatic Reading Glasses Base Apex Prismatic lenses help facilitate binocular viewing of objects held inside the near point of convergence Prismatic lenses generate an apparent image that is farther away than the real image

10 Prismatic Reading Glasses Intended for binocular use Angle of object s image Apparent angle of object s image Actual viewing distance Apparent viewing distance Lenses are thicker near the nose than temple = base of prism Each lens is designed with prism to bend light and sphere to help focus Range in power from +4.00D to D

$Diffractive Binocular Eyewear Prismatic eyewear - front view Diffractive$

11 Diffractive Binocular Eyewear Prismatic eyewear - front view Diffractive eyewear - front view Prismatic eyewear - top view Diffractive eyewear - top view

12 Diffraction: Altering the path of light Refraction Reflection Diffraction

13 Diffraction: Simple v. Controlled

14 Diffraction: Turning theory into practice

$refractive power MOD-structure for additional$ $magnifying power Diffractive structure of the$

15 Aspheric front surface for base curve and refractive power MOD-structure for additional magnifying power Diffractive structure of the first order for color correction Center thickness when assembled: <5mm

17 Standard Reading Glasses No prism necessary available from about +1.00D to +5.00D. Available in many different designs and styles

$Refractive v.$ $Diffractive ClearImage$ mono - front view

18 Microscopic Spectacles: Refractive v. Diffractive ClearImage II - front view noves mono - front view ClearImage II - top view noves mono - top view

19 Microscopic Eyewear Mounted in front of user s better eye Occlusion depends on eye dominance and rivalry Available in monocular powers from 12 to 32 diopters

20 Rules for using magnifying spectacles properly: 1. Hold object to be viewed at the focal length of the eyewear 2. Move object/material to be viewed horizontally across field of view. Do not turn head.

21 1. Hold object to be viewed at the focal length of the eyewear f = 1m / d Where: f = focal length of lens m= meters d= lens power in diopters f

22 2. Move the object/material to be viewed horizontally across field of view. Do not turn head. Low Vision Training Module #5

23 User s existing Rx: Can these two people wear off the shelf magnifying spectacles? Distance Rx #1 Sphere Cylinder Axis OD OS Distance Rx #2 Sphere Cylinder Axis OD OS

24 User s existing Rx: Can these two people wear off the shelf magnifying spectacles? Distance Rx #1 wearer can Distance Rx #1 Sphere Cylinder Axis OD OS Distance Rx #2 wearer cannot Distance Rx #2 Sphere Cylinder Axis OD OS

25 Refractive considerations: Spherical error may be compensated for in power of magnifying eyewear Astigmatic error must be corrected if deemed significant Be sure to consult with prescribing eye doctor!

26 If candidate s distance Rx does not allow for removal in favor of magnifying spectacles: Option 1: Prescription correct magnifying spectacles for needed elements Option 2: Use magnifying lenses that attach to candidate s distance eyewear

27 Option 1: Prescription correcting magnifying spectacles: Ex. 1 the candidate has the following Rx Distance Rx Sphere Cylinder Axis OD OS and needs 8 diopters of near magnification to read. What would the low vision Rx be?

28 Example 1: continued Low Vision Training Module #5 Orig. Rx + Needed sphere/ prism = Low Vision Rx Dist. Rx Sphere Cylinder Axis OD OS Sphere Cylinder Axis Prism OD In OS In LV Rx Sphere Cylinder Axis Prism OD In OS In

29 Option 1: Prescription correcting magnifying spectacles: Ex. 2 the candidate has the following Rx Distance Rx Sphere Cylinder Axis OD OS and needs 6 diopters of near magnification to read. What would the low vision Rx be?

30 Example 2: continued Low Vision Training Module #5 Orig. Rx + Needed sphere/ prism = Low Vision Rx Dist. Rx Sphere Cylinder Axis OD OS Sphere Cylinder Axis Prism OD In OS In LV Rx Sphere Cylinder Axis Prism OD In OS In

31 If candidates distance Rx does not allow for removal in favor of magnifying spectacles: Option 2: Use magnifying lenses that attach to candidate s distance eyewear

32 Advantages: Familiar Hands-free Disadvantages: Short working distance Conspicuous Wide field of view Not illuminated Inconspicuous

33 Magnifying spectacles are designed for hands-free extended viewing tasks of near objects Near Spotting Near Extended Spotting Intermediate Intermediate Extended Distance Spotting Distance Extended Hand-Held Stand Spectacles Telescopes Video

34 Extended Viewing tasks of near objects: Reading the mail Reading Newspapers

35 Extended Viewing tasks of near objects: Other reading

36 What they are How they work How to use them What types are available What are they made for

37 Questions?

38 Thank You!

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