Year : 1982 | Volume
: 30 | Issue : 4 | Page : 383--386
Static perimetry in glaucoma
Bakulesh M Khamar
M&J Institute of Ophthalmology, Civil Hospital, Ahmedabad, India
Bakulesh M Khamar
M&J Institute of Ophthalmology Civil Hospital, Ahmedabad
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Khamar BM. Static perimetry in glaucoma.Indian J Ophthalmol 1982;30:383-386
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Khamar BM. Static perimetry in glaucoma. Indian J Ophthalmol [serial online] 1982 [cited 2020 Jun 5 ];30:383-386
Available from: http://www.ijo.in/text.asp?1982/30/4/383/29478
Glaucoma is characterised by elevation of intraocular pressure, cup changes at the optic disc and field changes in form of various field defects.
Demonstration of presence of field defects is very useful in diagnosis of glaucoma in border line cases. It is also useful in management of glaucoma to know the progress of disease whether it is under control or not.
Field defects can be demonstrated most precisely with kinetic and/or static perimetry with help of "Goldmann's Perimeter".
This paper is based on experience gained while performing kinetic and static perimetry in cases of glaucoma.
MATERIALS AND METHODS
i.Selection of cases
Patients selected were known cases of glaucoma or glaucoma suspects in whom field were not plotted.
Patients with any change in media or with retinal pathology were excluded from the study.
Other criteria for including them to study were their willingness to spend approximately 3 hours for one eye, awareness regarding diseases and ability to respond.
II. Field Charting
It was done with "Goldmann's Perimeter" under standard conditions.
Kinetic perimetry was first performed then static meridonial perimetry was performed. The meridions were selected from the results of kinetic perimetry as per site of scotomas. When scotomas were not found static perimetry wasperformed on 45°-225° and 135° -315° meridions.
Results obtained are grouped under the headings advantages, pitfalls and disadvantages of static perimetry in comparision to kinetic perimetry and only illustrative examples are given to highlight each of them.
I. Advantages (i) Early diagnosis : - Mr. N. D. M. was a known case of chronic simple glaucoma in right eye. L. E. was found to be normal with kinetic perimetry. On 222° meridion in the static perimetry an absolute scotoma extending from 4° to 8° was seen. There was also irregularity in response suggestive of flattening of curve and partial scotoma on 225° meridion.
Thus static perimetry demonstrated the nerve fiber bundle defect which could not be demonstrated by kinetic perimetry. This defect is shown in a chart of kinetic perimetry for orientation.
(ii) Follow up of field :
Following characteristics defects were seen with static perimetry only.
(a) Increase in width of scotoma [Figure 2] shows field defect with kinetic perimetry, which were same on follow up examination.
Static perimetry shows increase in scotoma on 165°meridion from 13°sub to 17°, to 12° to 20°.
(b) Increase in depth of scotoma : [Figure 3] Kinetic & Static perimetry on 270° meridion performed at the same time. In follow up examination only static perimetry revealed in crease in depth of scotoma from relative to absolute.
(c) Alteration in curve of static perimetry. [Figure 4] shows kinetic perimetry which did not change. Static perimetry performed 2 months later shows the flattening of the curve on 135° and 315° meridion making it platu. This is suggestive of inadequate control as it shows decrease in sensitivity of a particular portion of retina though there is no demonstrable scotoma.
(d) Appearance of fresh scotomas : [Figure 5] Like results of kinetic and static perimetry performed for the first time, when it is performed in follow up, static demonstrates the field defects mixed by kinetic perimetry.
Pit falls of static perimetry are not inherent in its technique but they are rather due to the methods adopted to perform the static perimetry i. e. (1) performing the static perimetry in central 30°. (2) Performing the static perimetry on selected meridions only.
These pit falls are present when it is performed for the first time or in follow up examination, but they become most marked during follow up as it fails to show changes that has taken place.
1. Performing the static perimetry in central 30°.
This makes it impossible to show changes in peripheral field i. e. peripheral constriction field.
Peripheral constriction may be the only field defect in glaucoma and under such circumstances it is likely to be missed if only static perimetry is performed.
In follow up examination also increase in peripheral constriction is missed by static perimetry. [Figure 6]
This can be rectified by performing the static perimetry upto the periphery but this makes it more impracticable by consuming more time.
2. Performing the static perimetry on selected meridions only.
This fails to demonstrate field defect that has been taken place in another meridions which are not plotted. This can be overcome by plotting more meridions. But this is at the cost of more time.
III. Disadvantages :
The main disadvantages of static perimetry in comparision to kinetic perimetry are as follows: -
(i) Time consumption:
Time consumed is far more for static than for kinetic perimetry. When kinetic perimetry alone is performed very precisely it takes about half an hour per eye examination. When static perimetry in 4 meridions is combined with kinetic it takes around three hours per eye examination. Thus it is most extensive in terms of time consumed.
(ii) Tiring of patient
As time consumed by static perimetry is much more than kinetic perimetry and the process performing the static perimetry is repeatative on same lines without any alteration it makes patient feel tired. The bordom is to such a great in extent that examination cannot be completed in a patient. This will be evident fro rn the fact that of the 1st 100 eyes only in 28 eyes the examination could be completed.
(iii) Increased resistance from patient for follow up.
All factors contribute to increase in resistance or decrease in co-operation of patients.
This will be evident by the fact that of the first 26 eyes, only in 8 eyes it could be performed for the second time.