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

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

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

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

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

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

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

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

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

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

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 3/6 glasses 3/12-2 PH 3/9-1 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

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

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

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

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

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

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

Tropicamide 1% preferred mydriatic Tropicamide is an anticholinergic. Causes - mydriasis & cycloplegia Rapid action 15-20 mins. Duration - 4 - 6 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

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

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

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

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