1. To refer or not to refer for EDT’s? Dr Peter Good Consultant Clinical Scientist

2. Why refer for EDT’s? Unexplained visual loss Hereditary retinal dystrophy Nystagmus Visual Function in paediatrics Opaque Media Trauma Drug Toxicity

3. Indications for EDT tests IndicationVEPERGPERGEOGOCT Visual Loss Heredo- macular Nystagmus Opaque Media Trauma Drug Toxicity

4. Unexplained visual loss Is visual loss genuine FVER & PVER Site of LesionVER, ERG, PERG Potential acuityPVEP with threshold spatial frequency

5. Hereditary Retinal Dystrophy Hereditary v AcquiredOCT, ERG, EOG Rod/Cone, Cone/ RodOCT, ERG, EOG Macular DystrophyOCT, ERG, PERG, ?EOG Night BlindnessOCT, ERG, EOG X-Linked HeterozygoteEOG/ERG Please don’t ask for paediatric EDT’s when macular developed

6. Nystagmus AlbinismApkarian VEP Cone, Cone/Rod, Rod/ConeERG, OCT CSNBERG Congenital IdiopathicVEP/ ERG Delayed Visual MaturationVEP FoveoschisisERG OCT Optic Nerve Hypoplasia/ SOD VEP, USG

7. Visual Loss in Childhood Potential AcuityPattern Offset/ onset VEP Cortical BlindnessVEP NystagmusVEP, ERG, USG Metabolic DisordersERG Bulls Eye MaculopathyERG, PERG, OCT, PERG ONHVEP USG DVMVEP, ERG Night blindnessOCT, ERG, EOG

8. Opaque Media Lens/ Corneal/ Vitreous Opacity fVEP, ERG, USG Metal IOFBVEP, ERG, EOG, USG

9. Trauma Retinal or Optic Nerve Trauma? With Opaque MediafVEP, ERG, USG Without Opaque MediaVEP (f&p), ERG, USG

10. Drug Toxicity PheniothiazinesEOG/ERG ChelatorsEOG, VEP, ERG, PERG VigabatrinERG, Visual fields EthambutolVEP QuinineEOG, ERG, VEP, Fields Hydroxycholoroquin e/ Chloroquine Rarely but OCT only TamoxifenVER, ERG, EOG, OCT RoaccutaneERG DA

11. When not to request EDT’s Choroidal, Macular off Retinal Detachments Cataract without RAPD Before MRI/CT Acute Optic Neuritis (VA < 6/36), unless Functional EDT’s in young children where family history of heredo-macular dystrophy If VA > 6/9 in occlusion therapy

12. How to request? By referral letter to –Dr Peter Good –Consultant Clinical Scientist Visual Function request card Clinically urgent EDT’S to be discussed with Dr Good Do not routinely fax letters to us!

13. We don’t have a crystal ball! Please give all patient details Summary of ophthalmic findings Which is the affected eye Inform patient why they are attending