3Glaucoma =Optic neuropathy The evaluation of the appearance of the optic disc is central to the diagnosis and management of GlaucomaOptic Disc Evaluation:Why..?How..?What to look for..?
4The 4 goals of optic disc evaluation Distinguishing between the healthy and the sick =Diagnosing.Quantifying the amount of damage: Healthy,Mild,Moderate,Advanced DiseaseMonitoring Change,for better or for worseQuantitating the rate of change
7The 7 parameters to look for… Disc: Size and Shape2)Neuroretinal Rim (NRR):Size,Shape,PallorISNT rule3)Cup: Size and Shape in relation to the optic disc size,-Vertical C/ D Ratio, Cup depth / Excavation4) Optic Disc Hemorrhage: Presence & Location
9All these variables can be measured semiquantitavively by ophthalmoscopy without applying sophisticated techniques
101)Optic Disc: Size & Shape Determining the size of the disc =CrucialHelps to differentiate Physiological cupping from Pathological.Large discs have big physiological cups.Small Discs have small cups or no cupsMeasurement of Vertical Disc diameter :Length of the vertical beam of slit lamp lightMultiplied by correction factor of the condensing lensVolk 60 D= X 1Volk 90D= X 1.5
11Cup: Size, Shape, location in relation to the disc size Optic Cup= Excavation in the optic nerve headStereoscopic evaluationIn normal eyes= Areas of optic disc & Optic cup are corelatedLarge optic discs=Large cupSmall optic disc =Small cup or no cupEarly & moderate glaucomatous damage in small disc may be missed because of the erroneously low cup disc ratios
16Vertical Cup Disc Ratio Vertically oval optic discHorizontally oval optic cupIn normal eyes: Horizontal CD ratio > than vertical CD ratioIn Glaucomatous eyes: Vertical CD ratio > than the horizontal CD ratio
18The Neuroretinal Rim Size, Shape, Pallor. The ISNT rule:
19Thinning of the NRR Pallor of NRR Notching: A notch is a localized defect in the Neuroretinal rim on the cup side of the rim
20The Neurretinal rim loss in Glaucoma Usual sequence of NRR loss in Glaucoma:InferotemporalSuperotemporalHorizontal temporalInferonasalSuperonasalIn contrast,in the non glaucomatous optic nerve damage, the NRR is not always affected and hence contour of NRR is maintained.
24Optic Disc Hemorrhage Splinter or Flame shaped hemorrhages At the margin of the discHallmark of Glaucomatous optic nerve damage4 to 7 % of eyes with galucomaFound in early & moderately advanced Glaucoma and rare in very advanced stageLocated usually in the inferotemporal & superotemporal disc marginsAssociated with localized RNFL defect and neuroretinal rim notches .Suggests Progression.More common in NTG
28Retinal Nerve Fibre Layer Defect RNFL contains retinal ganglion cells axons covered by astrocytes and bundled by processes of muller cellsSeen as bright fine striations fanning off from the disc to the periphery.Dilated pupil, green light, clear optical media aids the evaluation of RNFL
29Retinal Nerve Fibre Layer Defect Localized RNFL defects:Can be detected before visual field defect has developedFocal type of NTGEarly to medium advanced Glaucomatous damageDiffuse loss of RNFL:More difficult to detectPeripapillary retinal vessels appear bareUnderlying Choroidal vessels more clearly seen.
33Parapapillary Chorioretinal atrophy 2 zonesCentral Beta zonePeripheral alpha zoneBeta zone occurs more often in glaucomatous eyes than in normal eyes.Helps to differentiate various subtypes of POAGHelps to differentiate from nonglaucomatous optic nerve damage