|Year : 1970 | Volume
| Issue : 4 | Page : 167-169
Scleral rigidity in emmetropes
YP Singh, SK Goel, RN Misra
Department of Ophthalmology, Sarojini Naidu Medical College, Agra, India
Y P Singh
Department of Ophthalmology, Sarojini Naidu Medical College, Agra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Singh Y P, Goel S K, Misra R N. Scleral rigidity in emmetropes. Indian J Ophthalmol 1970;18:167-9
The problem of estimating intraocular pressure in an undisturbed eye has been engaging the attention of the ophthalmological world. Many a tonometer was devised but all of them suffer from one defect, i.e. they disturb the equilibrium of the eye, when applied. This problem be-comes more accentuated when indentation tonometers are applied as they distort the eye-ball, strech their coats and expel the fluid out of the eye. Goldman's applanation tonometer can be said to be near perfect as it is little affected by the rigidity of ocular coats. But when tonography is done the electronic tonometer produces the changes comparable to indentation ronometer and hence the rigidity of ocular coats. But when tonography is done the electronic tonometer produces the changes comparable to indentation tonometer and hence the rigidity of ocular coats play a significant part. This is a variable entity and is affected by the contents of the eye-ball, the stress and strain of the varying tension and the structure of the sclera.
| Material and Methods|| |
The study was conducted on normal patients who attended the out-patient department of S. N. Hospital, Agra, for various eye diseases like immature cataract, dacryocystitis, chalazion, stye and pteiygeum, etc. They had no intraocular pathology. There was no history of glaucoma. The manifest error was not more than o.5 D.
The patient was asked to lie in a supine position and to fix the eye at a point on the ceiling. The eye was anaesthetised kith 1 % anaethaine drops. A certified Schiotz tonometer was brought in front of the visual axis and kept there for 3-4 seconds, to avoid oculocardiac reflex. The tonometer was then lowered on the cornea and rested for 2-3 seconds. Oscillation of the indicator on the scale were carefully observed and the whole or half scale unit close to the average position of pointer during the application was regarded as the reading. The reading was repeated with a 10 gm. weight. The right eye was always examined first and the lighter weight preceded the heavier. The scleral rigidity was calculated by using the table of Becker and Schaffer. The case was again examined the next day and if any discrepancy was found the case was excluded.
| Observation|| |
A total number of 395 eyes of 216 normal individuals of which 211 male and 184 eyes of 104 females were examined. Both the eyes were examined except in one-eyed patients. The cases were divided into four age groups between 20-30 years, 30-40 years, 40-50 years and above 50 years [Table - 1]
[Table - 2] shows the distribution of scleral rigidity in each of the four groups.
[Figure - 1]. Graph : Showing average scleral rigidity in different age groups.
[Figure - 2]. Scatterogram : Showing distribution of scleral rigidity in various age groups.
| Discussion|| |
More than a century ago, Von Gaefe designed the first indentation tonometer, to be followed by the applanation tonometer developed by Weber (1888), the pendulum has been going back and forth. Schiotz developed the tonometer which bears his name and realising its shortcomings calibrated it thrice in a span of 10 years.
Friedenwald postulated coefficient of scleral rigidity to be a constant characteristic of the eye of an individual. This has been questioned by Perkins and Glocter, Grant and Trotter.
The Schiotz tonometer is calibrated for a rigidity of .0215 and any variation in the value of scleral rigidity will give erroneous readings.
In our cases the average rigidity was found to be .0227 in the patients between 20-40 years of age but statistically insignificant. There was no difference statistically between the two sexes and the two eyes of an individual. However, there was a definite increase of rigidity in patients over 5o years of age where the average rigidity was .0267, and this is statistically significant. This increase in rigidity can be attributed to the decrease in the elasticity of sclera as compared to that of the cornea after the age of 40 years. This could also be due to the loss of water and in increase of calcium in the tissue with age. This study brings out the necessity of estimating the scleral rigidity after 5o years of age as higher than normal rigidity will give higher values of intraocular pressure and the patient subjected to unnecessary medication and psychological trauma for the rest of his life.
| Summary and Conclusion|| |
1. The normal scleral rigidity was found to be .0227.
2. There was an increase in scleral rigidity after the age of 40 years, but it was not statistically significant.
3. There was statistically significant increase in scleral rigidity after the age of 50 years.
| References|| |
Von Graefe: Tonometry & Tonography, Jhon. Gloster Page 2.
Friedenwald (1937): Am. J. Ophth. 30, 985.
Marc, F. J. (1957): Outflow pattern of Cat's eye. Amer. J. Ophth. 47: 547.
Perkins, E. S., Gloster, J. (1957): Further studies on the distensibility of the eye Brit J. Ophth..41: 475.
Schiotz, H. (1905): Arch Augnheilk 10: 1.
Weber, A. (1877): V. Graefes Arch. Ophth. 23: 1.
[Figure - 1], [Figure - 2]
[Table - 1], [Table - 2]