1. Sheila McGilvray Senior Charge Nurse
Ophthalmology Ward 25 Ninewells Hospital NHS Tayside
23rd Aug 2007
Retinopathy Screeners Training Course

2. Dilating the eyes for photography
Testing Visual Acuity
&
Dilating the eyes for photography

3. Testing Visual Acuity (VA)
Initial part of any ophthalmic examination/photography/treatment
A National grading protocol
Visual performance is dependent on
Integrity of retina, visual pathway
Quality of retinal image
Ambient light level
The measurement of visual acuity provides one measurement of a patients ability to see
Integrity – processing of the retinal image
The quality of the retinal image is affected by any refractive error, size of the pupil and clarity and shape of the cornea
Ambient light level – adequate for test
In diabetic retinopathy visual acuity is important because if the patients visual acuity drops this may be a sign of vitreous haemorrhage or maculopathy

4. Methods of Testing VA Most common - Snellen Test Chart
Gold Standard – EDTRS chart LogMAR
Kay Picture Test or Sheridan Gardiner
E Chart
Most common is the Snellen and this is an example of a 3m chart and I apologise that I will describe the 6m which is the more common size
EDTRS – early treatment of diabetic retinopathy study
LogMAR – logarithm of the minimum angle of resolution
Developed by ‘Bailey and Lovie’
Kay Picture Test similar to Sheridan Gardiner
Sheridan Gardiner uses cards with 7 letters (age 3-4) Kay picture replaces letters with pictures (age 2-3) on it examiner points to a letter or picture and patient points to corresponding letter or picture on card
E chart if patient is unable to read or speak English, patient holds a the letter E corresponding to the position on the chart but only 4 positions can be used

5. Snellen Test Type
Standard method – in Tayside the software converts Snellen to LogMAR
Not very sensitive for poorer visual acuities
The progress of letter sizes is unequal
Get a crowding effect
Not mathematically sound
Snellen chart used in Tayside

6. Snellen Test Type
Rows designated by ratio - test distance to distance normal person reading that sized letter
Mobile screening vans allow for 3m test type
For example – if a patient reads only 3/60
the 3/= distance from chart
the /60 = seen by person with standard acuity at 60 m
Starts with one large letter and then numbers of letters increase on each line but they decrease in size, the decrease in size is not represent equal steps in terms of difficulty
The smallest row read accurately indicates patient’s visual acuity in that eye

7. EDTRS chart LogMAR Recommended Gold Standard Better chart design
High contrast lettering
Letters set at equal linear steps, equal spacing
Contains a near equal score of difficulty on each line
More effective analysis and comparison of results

8. LogMAR Patient seated at 2m Separate chart for each eye
More consistent level of illumination

9. Preparation for Snellen Test Type
Patient comfort and privacy improves compliance
Sit back in chair not leaning forward
Chart illuminated appropriately at 3m
Occluder with pinhole
Hand washing facilities

10. Preparation and procedure
Explain procedure to patient
Check if patient uses contact lenses, distance glasses
Check each eye separately, right first
Use ocluder to ensure other eye covered
Advise wiping ocluder between patients with an alcohol wipe
Ensure patient’s glasses are up to date to obtain the best visual acuity
Distance, bifocal or varifocal glasses should be worn

11. Recording VA
Record if vision tested unaided or with corrective glasses or contact lenses
- unaided (UA)
- glasses worn (GL)
- contact lenses (C.L.)
Example result - RVA LVA
3/ glasses /12-2
PH /9-1
If VA is 6/12 or worse a pinhole should be used and this patient got 6/12-2 in the left eye so they got 2 letters wrong and I then checked using the pin hole

12. Recording VA If only half of line read e.g. 3/9 Record as either
3/9 minus no. of letters missed
or 3/12 + number of letters seen on 3/9 line

13. Or examiner holds up hand at 1m, patient asked to count fingers (CF)
If unable to see any letters and if practical move chart nearer to patient
Or examiner holds up hand at 1m, patient asked to count fingers (CF)
If unable to CF then examiners hand is moved in front of patients eye (HM)
Failure to see examiners hand move
Check with pen torch perception of light (POL)
If no light seen by patient (NPL)
Read 1st 3 points
Generally you would stop at this point
Just for information in the clinical setting the examiner would go on to check for perception of light

14. Using Pin-hole If reading less than 3/6 then use pin-hole
Allows only central light rays into eye along the visual axis
Eliminates blurring of vision if refractive error present
Using patient’s hand - risk of error, may not fully occlude their eye

15. Pin-hole
If acuity improves it usually indicates refractive error e.g. cataract
If VA worse through pin-hole over best correction macular disease must be considered
If a patient forgot their glasses or they are out-of-date a pin-hole should be used because refractive errors are significantly reduced

16. Preparation for pupil dilation
National Procedure
Try photos on undilated eye
If photography fails then dilate
Effects exposure image
Ability to capture multiple fields
Small pupil can create a shadow over retina causing the image to be un-gradable
Dilation allows optimal illumination allowing more successfully exposed images and ability to capture multiple fields

17. Checks prior to instillation of mydriatic drops
Patient name DOB CHI
Known allergies
Explain procedure and effect of drops-transient stinging, blurred vision
Check correct drop & dose, record batch no. & expiry date on softwear
Wash hands
Drop expiry date and batch no. should be recorded on softwear
No need to remove contact lenses

18. Tropicamide 1% preferred mydriatic
Tropicamide is an anticholinergic. Causes - mydriasis & cycloplegia
Rapid action mins.
Duration hours
Parasympatholytic drug
1% paralyses accommodation
2 muscles control the size of the pupil
Sympathetic system responsible for
Radial muscles of the dilator pupillae - pull open the pupil
Parasympathetic system responsible for
Circular muscle fibres of the sphincter muscle - pulls it shut
Tropicamide blocks the transmitter agent acetylcholine so the sphincter pupillae is prevented from working

19. Inform patient of effects of Tropicamide
Patient Information
Inform patient of effects of Tropicamide
Transient stinging
Blurred vision
Photophobia - sensitivity to light
Warn not to drive or use machinery until vision is clear
If brow or eye pain occurs, red eye, nausea, vomiting contact nearest eye department
In Tayside patients are provided with written information and contact no

20. Contraindications
Eyes predisposed to acute glaucoma (shallow-angle and shallow anterior chamber)
Hypersensitivity
Systemic effects not expected due to short duration.
Reduced by compressing lacrimal sac at medial canthus
Acute angle closure glaucoma can be precipitated but the risk is minimal
Hypersensitivity to Tropicamide or any other ingredient is very rare

21. Adverse event following mydriasis
Patient knows how to access advice
Tayside have a 24 hour point of contact at Ophthalmology ward 25, Ninewells
Availability of on call Ophthalmologist if patient symptoms necessitate review

22. Conclusion Recording VA important part of ophthalmic examination
Preparation, check patients details & history before procedure & instilling mydriatic drops
Inform patient of effects of mydriatic drops, given Ophthalmology dept. phone no. if advice required
And next is the role play session