|Year : 1979 | Volume
| Issue : 4 | Page : 105-106
The versatile Halberg applanation-tonometer
Keiki R Mehta, SN Sathe, SD Keryaker, V Rao
Seaside, 147, Colaba Road, Mumbai, India
Keiki R Mehta
Seaside, 147, Colaba Road, Mumbai
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Mehta KR, Sathe S N, Keryaker S D, Rao V. The versatile Halberg applanation-tonometer. Indian J Ophthalmol 1979;27:105-6
|How to cite this URL:|
Mehta KR, Sathe S N, Keryaker S D, Rao V. The versatile Halberg applanation-tonometer. Indian J Ophthalmol [serial online] 1979 [cited 2020 Aug 13];27:105-6. Available from: http://www.ijo.in/text.asp?1979/27/4/105/32591
Maklakoff in 1885 devised the applanation tonometer utilising the principle that the force remaining constant, the applanated or flattened corneal area is the measure of ocular pressure. Posner and Inglima in 1965 developed a more sophisticated model of the Maklakoff tonometer. The Halberg applanation tonometer devised in 1968 is an optical modification of the Posner Inglima tonometer. The aim of this study is to evaluate the accuracy of this tonometer by comparison with other popular tonometers.
| Materials and Methods|| |
Four categories of patients were studied:
1) Normal patients, 2) Patients with myopia of more than 5 dioptres, 3) Aphakic patients, 4) Patients with raised intraocular pressure.
Ocular pressure measurements were taken in the following order: Perkins, Halberg and Schiotz tonometry. Three consecutive readings were taken with each of the tonometers and averaged to prevent error. To prevent observer bias, conversion of the Halberg readings by the Posner Inglima tables and the Schiotz by the Freidenwald tables was not done till the series were complete.
Observations and results
Mean tension readings of the Perkins, Halberg and the Scbiotztonometer are displayed as a composite table. The Halberg tonometer utilising the Posner Inglima tables reads consistently higher by a predictable margin of 3.00+0.1 mm. Hg. This factor is important in screening surveys and rapid OPD scanning to prevent unnecessary border line glaucoma interpretation.
In normal eyes we found an excellant correlation between the Halberg, the Peikin and the Schiotz tonometer. In my opic eyes and aphakic eyes where the ocular rigidity factor comes into play, the Perkin and the Halberg are far more accurate while the Schiotz gave widely disparate readings. [Table - 1] demonstrates the stability of the Halberg tonometer compared to the Parkins as a means indicative of the inherent accuracy of the tonometer.
| Discussion|| |
It was clearly evident from the data we analysed that the Halberg tonometer readings are more comparable to the Perkin applanation tonometer than the Schiotz tonometer. Reproducibility of the Halberg and the Perkins was excellent with readings never differing beyond 3.1 mm. knowing that the Halberg has a consistent high reading (actually the Posner tables can be scaled down by 3 mm to give fairly identical readings) of a measurable extent helps in evaluating the correlative frequency. In eyes with abnormal scleral rigidity the Halberg gives, compared to the Sehiotz, accurate reliable readings.
| Advantage of the Halherg over the Perkin tonometer|| |
1. Manually easier to use as it is smaller and lighter. Being less cumbersome it permits easier lid retraction.
2. Has no parts to wear out, Needs no calibration.
3. Far less expensive to purchase.
4. Room lighting unimportant. Amount of fluorescein instilled not critical.
5. Needs no maintainance.
6. Far more rapid as there is no critical end point. Again the built in optical safe guards prevent over or under applanation.
| Disadvantage of the Halberg|| |
1. Can only be used in the supine position.
2. Wider area for applanation required. 3.8 mm to 5.6 mm as compared to 3.06 mm for the Perkins.
| Summary|| |
The Halberg is a fairly accurate, reliable and safe instrument. It is light weight, sturdy and uncomplicated, easy to handle and gives stable reproducible readings. It should be the instrument of choice in hospital out-patient departments and in glaucoma screening surveys for it offers the accuracy of the Perkins with the facility, ease of handling and the economy of the Schiotz.
[Table - 1]