visual fields in glaucoma

8/6/2019 Visual Fields in Glaucoma

1/17

1

VISUAL FIELDS IN GLAUCOMA

Perimetry is d clinical assessment of the

VF

It serves in [a] Identifying abnormal fieldsie. Making diagnosis. [b] Quantitative

assessment of normal or abnormal fields

during follow-ups

Some methods may be better in diagnosis

than follow-up and vice-versa


2/17

2

Automated Static Perimetry

Standard in d last 2 decades

Newer ones are:

Short-wavelength automated perimetry[SWAP],

High-pass resolution perimetry,

and frequency-doubling technology[FDT]perimetry


3/17

3

PATTERNS OF NERVE LOSS

The hallmark is the nerve fiber bundledefect. Possible defects are:

Generalized depression

Paracentral scotoma

Arcuate or Bjerrum scotoma

Nasal step

Altitudinal defect

Temporal wedge


4/17

4

Patterns Contd

The superior and inferior poles of the opticnerve appear to be most susceptible toglaucomatous damage.

Double arcuate scotoma, may occur,resulting in profound peripheral vision loss

Typically, the central island of vision and

inferior temporal VF are retained until late The pt and the perimetrist can bring

variables into the result it is subjective


5/17

5

[L]Normal view, [R] Glaucomatous

view


6/17

6

Normal view vs Tubular vision


7/17

7


8/17

8

INTERPRETATION

First assess quality.

Percentage of fixation losses, the false

+ves & false ves Damaged areas demonstrate more

variability than normal areas.

Glaucomatous damage may cause anincrease in false-negative responses

All this will be used to assess pts reliability


9/17

9

ABNORMALITY

Normal VF show greatest sensitivity

centrally, falling steadily toward the

periphery

Study the Humphrey or Octopus field

machine generated numerical data.

An abnormal pattern deviation has greater

diagnostic specificity than a generalised

loss.


10/17

10

INTERPRETATION OF A SERIES

OF FIELDS Should meet 2 goals:

[a] Separating real change from ordinary

variation [b] To determine the likelihood that a

change is related to glaucomatous progression.

This is made easier with a good baseline, this is

why a reliable field is obtained early

Progression of existing defects or suspectednew ones should be reproducible on subsequent

examinations to establish their validity.


11/17

11

CORRELATION WITH OPTIC

DISC If no correlation other causes of visual lossshould be considered eg. ION, pituitary tumor,demyelinating or other neurologic disease,

especially in d following situations -Disc less cupped than indicated by field

-Disc pallor is more than cupping

-Progression of field loss seems excessive

-Pattern of VF is uncharacteristic -Field defect does not correlate with disc

abnormality


12/17

12

STAGING

After determining the presence of the

disease visual field examination is used to

stage the disease.

Shallow / isolated field defects are

characteristic of early glaucoma,

whereas extensive deep deficits,

encroaching fixation are characteristic of

late or end stage glaucoma


13/17

13

INTERPRETATION Contd

In patients with mild / moderate glaucoma

visual field examination is usually to

determine if disease progression has been

halted.

This would also hold true for patients with

advanced glaucoma.

In advanced glaucoma, assessing fixation

characteristics is important to plan ahead.


14/17

14

How often should the fields be

done ? Though there is no consensus guidelinesdo exist.

(1) If the results of the field test aresufficient to confirm the diagnosticconclusion, fields may be repeated at leastonce more (36).

A change in therapy on the basis of asingle abnormal visual field test is onlyrarely appropriate.


15/17

15

FOLLOW-UPS

Ocular hypertension : Establish abaseline and perform followup fields

on the basis of degree of risk fordeveloping glaucoma.

Patients with low IOP, negative familyhistory, or optic nerves that appear

healthy, test every one or two years. Patients with unstable high IOP or other

risk factors, every 3-6 months.


16/17

16

FOLLOW-UPS Contd

Stable glaucoma : Initially every 6-12months.

Patient compliance needs to be kept inmind.

Visual fields by measuring the cumulativedamage are sensitive to detect

progression especially when IOP appears to be well

controlled (assessment of compliance).


17/17

17

FOLLOW-UPS Contd

Unstable glaucoma : One can ask for

several fields within a span of few months.

This would hold good people who have arelative contraindication to surgery.

visual fields in glaucoma

Documents