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   Table of Contents      
Year : 1983  |  Volume : 31  |  Issue : 5  |  Page : 597-602

Role of friedmann's visual field analyser and ophthalmodynamometry in the early diagnosis of chronic simple glaucoma

Instt. of Ophthal., Aligarh Muslim University, Aligarh, India

Correspondence Address:
G P Gupta
Instt. of Ophthal., Aligarh Muslim University, Aligarh
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Source of Support: None, Conflict of Interest: None

PMID: 6671771

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How to cite this article:
Gupta G P, Saiduzzafar H, Gupta S. Role of friedmann's visual field analyser and ophthalmodynamometry in the early diagnosis of chronic simple glaucoma. Indian J Ophthalmol 1983;31:597-602

How to cite this URL:
Gupta G P, Saiduzzafar H, Gupta S. Role of friedmann's visual field analyser and ophthalmodynamometry in the early diagnosis of chronic simple glaucoma. Indian J Ophthalmol [serial online] 1983 [cited 2020 Jan 21];31:597-602. Available from: http://www.ijo.in/text.asp?1983/31/5/597/36601

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  Introduction Top

The glaucoma suspect is a problem when it comes to early diagnosis which is a must because of the irreversible, bilateral and insiduous nature of the visual field defects the disease results in. Only a high index of suspicion together with a detailed history, careful examin­ation and repeated investigation can be of any help.

Recent trends tend to favour the "vascular concept" to explain the genesis of the visual field defects in glaucoma; with this in view, in the present study the complementary role of ophthalmodynamometry and static perimetry in the early diagnosis of chronic simple glaucoma has been assessed.

  Material and Methods Top

In all cases a detailed examination including applanation tonometry and gonioscopy was done. The systolic and diastolic blood pressure was recorded.

Ophthalmodynamometry was carried out with the Bailliart's [1] ophthalmodynamometer employing the standard technique, [Figure - 1] and the systolic and diastolic values of the central retinal artery were recorded.

Central visual fields were quantitatively estimated by static perimetry on the Friedmann's visual field analyser (F.V.A.) [Figure - 2].

Central visual field examination on the Friedrnann's visual field analyser and its analysis

(a) Central visual field examination:-
The sensi­tivity of the retina in terms of filter density is measured by the principle of static perimetry. 2, 3 or 4 stimuli are simultaneously shown to the patient, the intensity (log units) of which is varied by the interposition of neutral density filters of known value between the electronic flash tube (source of stimulus) and the observer. The neutral density filters are mounted on discs controlled by knobs on the back of the instrument, by manipula­tion of which any strength of neutral density filter ranging from 0.0-4.0 (log units) in steps of 0.2 log. units can be interposed. The test is started with a strength of neutral density filter compatible with the age of the patient, e.g. 2.0 log. units 0-40 years, 1.8 log units 41-50 years etc. The test is carried through the 15 positions of the lever labelled A to P (I omitted) and the results are charted on a 15 position chart and subsequently compil­ed onto the composite chart.

(b) Analysis:- The visual fields were analysed as per modified chart shown in [Figure - 3] in which the arrows indicate the points included in a particular ring. The points falling on the different isopters 5°, 10° etc. are considered in the adjacent ring towards the centre for the purposes of calculation.

The filter density value of all the points in each ring were summed up and then divided by the total number of points in that ring. This gave the average filter density (Av.F.D.) for that ring. This value deducted from the value for the filter for age to eliminate age as a variable and this gave the value of the difference in filter density (D.F.D.) for that ring.

Filter for age-Av.F.D. for ring D.F.D. for ring.

This difference in filter density indicates a reduction in retinal sensitivity.

Calculation of the Gradient

Calculation of the various mean pressures

(a) * Mean Humeral (Systemic) blood pressure (PAHm)
using' Wezler and Boger's equation.

PAHm = PAH diast + 0.12 (PAH syst.-PAH diast.)

(Diastolic pr) (Systolic pr Diastolic pr)

(b) Mean central retinal artery pressure (PAm) Practical Value

PAm** = PA diast. + 0.42 (PA syst.-PA diast.)

The systolic/diastolic values obtained in gms. by ophthalmodynamometry are converted into mm. Hg. using the table of Muller Brunning and Sohr and sub­stituted in the above formula.

(c) Theoretical mean central retinal artery pressure (PAOm)***

PAOm = 0.475 (PAH-PO) + PO (Weiglin's Equation)[3] (a)*

PO = Intraocular pressure

(d) Gradient:

PAm* * - PAOm* * * = Gradient (b) (c)

Value of Gradient is positive when (b) is more than (c)

Value of Gradient is negative when (b) is less than (c)

  Observations and Results Top

The eyes included in the study were grouped into non-glaucomatous (N.G.), suspected glaucomatous (S.G.) and glaucomatous (G) categories on the basis of the following parameters.

1. Intraocular pressure (Normal range upto 20 mm. Hg.)

2. Phasing (Normal range 6 mm. Hg.)

3. Cupping of the optic disc, C/D ratio (Normal below 0.3).

4. Water drinking test (Normal range upto 8 mm. Hg.)

5. Central visual fields/Retinal sensitivity. This was assessed in relation to the sensitivity of the unaffected eyes.

When two of the above parameters were in the suspicious range (highest limits of normal) the eye was included in the suspected glaucomatous group.

  Discussion Top

When the visual fields were studied in terms of mean differences in filter density against the different ranges of the mean central retinal artery pressure (PAm), it was observed that the PAm value did not have any significant relationship with the visual field changes in glaucoma.

However, the gradient was found to have a definite relationship. A positive gradient implies the predominance of the intravascular over the intraocular pressure, this situation is favourable for the disc nutrition and it was observed that the nonglaucomatous eyes had a gradient ranging from + 20 to - 5, only one eye had a gradient of between - 6 to - 10. In the suspected glaucomatous group the gradient range was from =, 5 to - 25 showing a sudden shift towards the minus side. This shift is more obvious in the glaucomatous group where all eyes except one have a negative gradient ranging upto - 30. A negative gradient signifies a predominance of the intraocular pressure over the intravascular pressure, a situation adverse for disc nutrition.

Further using the F.V.A. we measure and quantitatively estimate the subtle changes in retinal (sensitivity) which detects a decrease in sensitivity much before the total loss of sensitivity expresses itself as a visual field defect on the Bjerrum's screen. Our observations show that the retinal area corresponding to the 10-15° ring shows the highest mean difference in filter density in all the groups indicating thereby that this area is more susceptible to visual field loss. Furthermore eyes with a difference in filter density between 0.20 and 0.31 (log. units) may be put in the category of suspected glaucoma. If this value is associated with a negative gradient the two together form a sensitivity indicator for an early diagnosis and prognosis of a case of chronic simple glaucoma.

This combination would also prove better in the follow up of a case of chronic simple glaucoma in which the deterioration of the visual fields are not manifest on the Bjerrum's but they may be detected either by an increase in the difference in sensitivity in the 10-15° ring or an increase in the value of the minus gradient or a combination of both. This would also be of help in the proper assessment of the prognosis of a case.

Francois and Neetens [4] conducted a similar study in which the visual fields were done on the Bjerrum's screen.

  Summary Top

The measurement of blood pressure and ophthalmodynamometry for the calculation of the gradient coupled with the central visual field examination on the F.V.A. forms a most sensitive tool in early diagnosis of glaucoma.

  References Top

Bailliart, P., Ann. Oculist. (Paris) 154: 257, 648. From "System of Ophthalmology", by Duke Elder, W.S. Henry Kimpton, London, Vol. VII, 1962, p. 355, 1917.  Back to cited text no. 1
Wezler and Boger, Ergebn. Physiol., 41: 292, 1939.  Back to cited text no. 2
Weiglin. E., Ber. Dtsch. Ophthal. Ges., 54: 50: 1948.  Back to cited text no. 3
Francois, J. and Neetens, A., From "Increased intraocular pressure and optic nerve atrophy", by Francois, J. and Neetens, A.D.W. Junk Publishers, 1966, p. 222-225, 1966.  Back to cited text no. 4


  [Figure - 1], [Figure - 2], [Figure - 3]

  [Table - 1], [Table - 2], [Table - 3]


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