Optic Disc Evaluation in Glaucoma

DR.BHARTI AHUJA

GLAUCOMA –a chronic progressive optic neuropathy caused by a group of ocular conditions which lead to damage of optic nerve with loss of visual function.

Optic nerve head changes associated with glaucoma are thought to be seen prior to the development of visual field loss.

The aim of this communication is to describe the morphological changes of the optic nerve head in glaucoma, discuss the differential diagnosis and

highlight the techniques of clinical evaluation of the optic disc.

• Optic disc-Colour,shape,size• Optic cup• Cup disc ratio• Neuroretinal rim (NRR)• Peripapillary chorioretinal atrophy• Retinal vessels• Retinal nerve fiber layer(RNFL)

SMALL DISC WITH GLAUCOMA

LARGE DISC WITH GLAUCOMA

• Direct ophthalmoscopy• Slit lamp-high power concave lens

(Goldmann,hruby)

- high power convex lens (60,78,90D)

• Fundus photography -Stereoscopic photographs

• Recent laser imaging techniques

Cup- disk ratio(assymetry) Neuroretinal rim(NRR)Evaluation Vascular changes Configuration of vessels Peripapillary atrophy Retinal nerve fiber layer

abnormalities(RNFL)

C/D=0.2

C/D=0.7C/D=0.9

Zone alphao Outero Irregular hypo/hyperpigmented region of RPE ,parapapillary choroid.o Corresponds to choroidal

crescant.o Normal area=0.4sq mmo In glaucoma=0.65 sq mmo Contribute to relative

scotoma.o Commonly seen in normal

eyes.o Pigmentary irregularities in

RPE.

Zone betao Innero A marked atrophy of RPE,Choriocapillaries.

o Scleral crescant

o 0.13 sq mmo 0.79 sq mmo Absolute scotoma

o 15-20% normals.o Complete loss of RPE cells

& a marked loss of photoreceptors

Hemorrhages over the disc margin

This sign occurs This sign occurs from loss of rim from loss of rim tissue that tissue that previously supported previously supported the disc vesselthe disc vessel..

Note sharp edge of the Note sharp edge of the two disc vessels at 12 two disc vessels at 12 o’clock in a patient o’clock in a patient with bean potting of with bean potting of the optic nerve from the optic nerve from end-stage glaucoma.end-stage glaucoma.

RNFL Defect

LASER SCANNING IMAGING TECHNIQUES

SLO(1979)

CSLO/SLT(1987) RTA

SLP/RNFL analyser

GDx

•HRT

•TOPss

HRA

GDxFCC

GDxVCC

StereophotogrammetryCSLO

RasterstereographyOCT(zeiss Stratus)

Rodenstock (ONHA)

TOPCON IMAGENET

HUMPHREY RETINAL ANALYSER(HRA)

CSLT

HRT(scanning laser ophthalmoscopy)

GDx(scanning laser polarimetry)

SLP

Objective,quantitative assessment of Objective,quantitative assessment of peripapillary RNFL.peripapillary RNFL.

Measures the Measures the retardation retardation of a polarized laser of a polarized laser light passing through tissues having the light passing through tissues having the physical property of physical property of form birefringenceform birefringence..

Near infrared laser(780 nm)Near infrared laser(780 nm) Commercially available models-Commercially available models-

(GDxFCC,GDxVCC)(GDxFCC,GDxVCC) Undilated pupil(2 mm)Undilated pupil(2 mm) 0.7 seconds0.7 seconds

Representation printout of GDx VCC RNFL ANALYSER

ADVANTAGESADVANTAGES LIMITATIONSLIMITATIONS Easy to operate.Easy to operate. Doesn’t require pupillary Doesn’t require pupillary

dilatation.dilatation. Reproducibility.Reproducibility. Doesn’t require a reference plane.Doesn’t require a reference plane. Can detect glaucoma on first Can detect glaucoma on first

examinationexamination Early detection before std visual Early detection before std visual

field.field. Comparison with age matched Comparison with age matched

normative data.normative data.

Doesn’t measure actual Doesn’t measure actual RNFL thickness.RNFL thickness.

Low sensitivity,specificity Low sensitivity,specificity for detection of pre for detection of pre perimetric glaucoma in perimetric glaucoma in clinical studies.clinical studies.

Limited use in moderate Limited use in moderate and advanced glaucoma.and advanced glaucoma.

No database from indian No database from indian populationpopulation

Affected by anterior and Affected by anterior and posterior segment lesions.posterior segment lesions.

Real time, 3D Imaging Helium neon DIODE LASER(670 nm) Transverse resolution-10 microns Axial resolution-300 microns

ADVANTAGES LIMITATIONS

•EASY TO PERFORM •Data interpretation

•Reduced need for pupillary dilatation ,clear media

•No precise mst of NFLT

•REPRODUCIBLE •expensive

HRT I HRT II C

NOV 1991 32 scans Field of view can be

set to 3 levels(10×10,15;20 deg)

256×256px resolution Both ONH and

macular images

APRIL 1999 16-64scans Only 15×15 degrees

384×384 pixels

ONH only

Non invasive,real time ,high resolution technology provides optical cross sections of a scanned region.

Diode laser(820 nm);laser interferometry. To assess the retinal nerve fiber layer and

identify potential structural changes indicative of early glaucoma.

Physiological cuppingPhysiological cuppingOptic nerve colobomaOptic nerve colobomaCongenital optic disk pitCongenital optic disk pitAnterior ischemic optic neuropathy(AION)Anterior ischemic optic neuropathy(AION)Neurological causesNeurological causes

Optic disc coloboma

AION

Morning glory syndrome

• Examination and documentation of the optic Examination and documentation of the optic disc and retinal nerve fiber layer (RNFL) is disc and retinal nerve fiber layer (RNFL) is essential for diagnosis and monitoring of essential for diagnosis and monitoring of glaucoma.glaucoma.

• Stereoscopic fundoscopic examination Stereoscopic fundoscopic examination combined with photography remains still combined with photography remains still the the goldgold standardstandard forfor early perimetric early perimetric glaucoma. The combination of StratusOCT glaucoma. The combination of StratusOCT average RNFL thickness(GDxVCC) and HRT average RNFL thickness(GDxVCC) and HRT III cup-to-disk area ratio will provide a high III cup-to-disk area ratio will provide a high diagnostic precision. diagnostic precision.

Thank you!!!!