Ординатура / Офтальмология / Английские материалы / A Visual Field Evaluation with Automated Devices 2nd edition_Reddy_2006

122 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

VISUAL FIELD DEFECTS IN COMBINED CASES

OF CATARACT AND GLAUCOMA

When the patient is having both cataract and glaucoma, the visual field testing is very important. It gives the following information -

1.How much field is affected

2.How much field is retained around the fixation point

3.This information helps us to explain the prognosis to the patients about the visual outcome after surgery. Usually cases of glaucoma associated with cataract will produce irregular generalized field defect.

Here I am presenting 4 cases of the visual field defects due to cataract associated with glaucoma. In the combined cases of cataract and glaucoma, the single field analysis printout will show the following features. The total deviation probability plot shows generalized depression and the pattern deviation probability plot shows localized scotomas in arcuate area and the extent of scotoma depends on the damage of the optic nerve. The mean deviation index and PSD will be very high.

124 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

Interpretation: This visual field is the best example of a combined case of cataract and glaucoma. If the patient is having both cataract and glaucoma the total deviation probability plot shows diffuse scotomas and the pattern deviation probability plot shows localized scotomas usually in the arcuate area. The most important point we must notice regarding the black square (the symbol that is given to the ‘P’ value less than 0.5%) is that it usually represents the decibel deviation of total deviation numerical plot >-6dB. So the point of the retina represented by black square lost its sensitivity minimum by -6dB. So it can also be -10 dB, -15dB, -20dB or -30dB. But all these decibel deviations are represented by black squares. So the depth of scotoma is not known. Only the depth of the scotoma (the exact degree of the decibel deviation of the black square at that point) is known from total deviation numerical plot.

In this field printout

1.The total deviation probability plot contains 28 black squares.

2.The black squares according to their decibel deviations of total deviation numerical plot are divided into two groups

Group-1: The black squares with decibel deviations equal to or < -11dB=14 in number

Group-2: The black squares with decibel deviations equal to or > -12dB=14 in number

All the 28 black squares shown in total deviation probability plot include the decibel deviations from - 6dB onwards. But only the decibel deviations >-12dB are shown in pattern deviation probability plot. To get a scotoma in pattern deviation probability plot there should be irregular depth of field defects in the total deviation probability plot. If there is uniform degree of field loss we do not see any scotoma in the pattern deviation probability plot. If there is a irregular depth of field loss the superficial and moderate degree of scotomas are eliminated and the defect depth of deep scotomas are adjusted and the resultant new localized scotomas are highlighted in the pattern deviation probability plot. This is the basic concept behind the two probability plots in the single field analysis. In this example the decibel deviations equal to or < -11dB are eliminated and only the decibel deviations equal to or greater than - 12dB are highlighted in the pattern deviation probability plot.

Global indices

MD : –9.4dB P value < 0.5%

PSD :7.67dB P value< 0.5%

Comment : Generalized depression with deep localized scotoma (generalized depression is indicated by MD value and the localized scotoma is represented by PSD)

G.H.T : Outside normal limits.

Final interpretation report: Generalized depression due to cataract shown in the total deviation probability plot and dense lower temporal arcuate scotoma due to glaucoma is shown in pattern deviation probability plot.

126 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

SINGLE FIELD ANALYSIS PRINTOUT IN A CASE OF

CATARACT AND GLAUCOMA—CASE II

T. Sri Ramulu Right eye field

Selection of the test : 24-2 SITA Standard Reliability : Good

A case of irregular generalized field defect

1. Generalized depression in the total deviation probability plot and localized field defect in the pattern deviation probability plot.

2. PSD : 6.73 dB P < 0.5%

3. MD : -15.33 dB P < 0.5%

128 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

SINGLE FIELD ANALYSIS PRINTOUT IN A CASE OF

CATARACT AND GLAUCOMA—CASE IV

G. Nirmalamma Left eye field Selection of the test : 24-2 SITA Standard Reliability : Good

A case of irregular generalized field defect 1. Generalized depres-

sion in the total deviation probability plot and localized field defect in the pattern deviation probability plot.

2. PSD : 7.76 dB P < 0.5%

3. MD : -26.85 dB P < 0.5%

130 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

SINGLE FIELD ANALYSIS PRINTOUT IN A CASE OF

CATARACT—CASE I

P. Venkata Rao Left eye field

Selection of the test : 30-2 SITA Standard Reliability : Good

A case of uniform generalized field defect

1. Generalized depression in the total deviation probability plot and

almost normal pattern deviation probability plot.

2. PSD : 1.61 dB

3. MD : -8.52 dB P < 0.5%