|Year : 1990 | Volume
| Issue : 4 | Page : 164-165
Ultrasonic measurements of extraocular muscle thickness in normal Indian population
Ritu Arora, Lalit Verma, Atul Kumar
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, Ansari Nagar, New Delhi-110 029, India
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, Ansari Nagar, New Delhi-110 029
Source of Support: None, Conflict of Interest: None
Standardized 'A' mode of Kretztechnik--7200 mA was used in 40 eyes of 20 patients for the measurement of extraocular muscle thickness. The mean thickness value of medial, lateral, superior and inferior rectus in the normal Indian population was found to be as 4.015 +/- 0.762 mm, 3.548 +/- 0.369 mm, 3.757 +/- 0.654 mm and 3.177 +/- 0.662 mm respectively.
Keywords: Ultrasound, Extraocular Muscle Thickness
|How to cite this article:|
Arora R, Verma L, Kumar A. Ultrasonic measurements of extraocular muscle thickness in normal Indian population. Indian J Ophthalmol 1990;38:164-5
|How to cite this URL:|
Arora R, Verma L, Kumar A. Ultrasonic measurements of extraocular muscle thickness in normal Indian population. Indian J Ophthalmol [serial online] 1990 [cited 2020 Jul 2];38:164-5. Available from: http://www.ijo.in/text.asp?1990/38/4/164/25509
| Introduction|| |
Extraocular muscle(EOM) enlargement can result from a wide variety of disease processes. However, there are available only a few reports of the measurement of thickness of the extraocular muscles. ,, As highly significant muscle thickness variation among different races of normal population has been reported,  there is a need for the knowledge of normal values for EOM thickness among the Indian population for the comparison against pathologic eyes. No study is available regarding the normal values of extraocular muscle thickness from this part of the subcontinent. We used ultrasonic biometry to measure the thickness of the extraocular muscles in 40 eyes of 20 non-diabetic cases to compute the standard average thickness in the normal Indian population.
| MATERIAL & METHODS|| |
40 eyes of 20 non-diabetic cases referred to our echography laboratory for the vitreo-retinal work up, prior to vitrectomy, were taken in the study. Muscle thickness of all the four recti was recorded in both the eyes. Standardized 'A' mode of Kretztechnik - 7200 mA was used for the measurement. After instillation of 4% Xylocaine drops, the extraocular muscle thickness was measured on the orbital scan in microseconds at tissue sensitivity according to the technique of Ossoining ,.The ultrasonic probe was allowed to contact the sclera on the contralateral meridian of the extraocular rectus muscle, that was to be examined. The angle of the probe was changed in order to orient the probe towards the more posterior direction, until the defect of the A - mode echo spikes showed the largest amplitude. The defect represented the exact thickness of the extraocular rectus muscle when the negative defect of the echospikes showed largest amplitude with the sharpest surface signals on both sides with upright leading edges. The probe used had the transducer of 8 MHz. The muscle thickness so obtained was converted into millimeters using an average sound velocity in tissues as 1550 m/s 2. Each eye also underwent axial length measurement by the standardized 'A' Scan of Kretztechnik - 7200 m A.
| Results|| |
The mean and maximal thickness of the medial, lateral, superior and inferior rectus muscles of 40 eyes of 20 patients is depicted in [Table - 1]. The distribution of the thickness values for each muscle is shown in [Figure - 1]. The age range of our otherwise normal patients was 10 - 40 years. There were 10 male and 10 female patients. The mean values of the measurements of the medial, lateral, superior and inferior rectus muscles were 4.015 0.762 mm, 3.548± 0.369 mm, 3.757 ± 0.654 mm, 3.177 ±0.662 mm respectively. The maximum thickness of the medial, lateral, superior and inferior rectus muscles at the 95th percentile were 4.656 mm, 3.880 mm and 3.880 mm respectively. No correlation was found between the axial length of the eyeball and extraocular muscle thickness.
| Discussion|| |
The usefulness of A-scan standardized echography in the diagnosis of endocrine myopathy and various other
muscle disorders is well established ,,,] Various authors have given values only for medial rectus and the enlargement of this muscle has been taken into acccount while doing the echography in thyroid patients. ,
However, few reports are available which give normal values for all four recti ,,.
In our study, thickness of medial, lateral, superior and inferior rectus was found to be 4.015 + 0.742 mm, 3.548 + 0.369 mm, 3.757 + 0.654 mm,3.177 + 0.662 mm respectively. Value for medial rectus thickness is in agreement with the value reported amon Asians 4. Lateral rectus value is significantly different. ,[2 ] Superior and inferior rectus mean thickness is also different from corresponding values reported. , This justifies the need for the study in normal population from our country for comparative evaluation against pathologic eyes in Indian population.
There was no statistically significant difference in thickness between the left and right eyes in any of the muscles. There was no significant correlation between the thickness of four rectus muscles and the age, sex, weight and stature in healthy persons. These findings are in agreement with earlier reports. , Inferior rectus was found to have the minimum mean thickness of 3.177 ± 0.662 mm when compared with other muscles,
Thus we conclude that the mean values for medial, lateral, superior and inferior recti in our study were 4.015 + 0.762 mm, 3.548 ± 0.369 mm, 3.757 ± 0.654 mm, 0.1775 ± 0.6622 mm respectively. The 95th percentile thickness value was found to be 4.656 mm for the medial rectus and 3.880. mm for the lateral, superior and inferior recti. Any muscle thickness when equal to or more than 95th percentile level of a corresponding muscle thickness in the normal population should be considered abnormal.
| References|| |
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Measurement of Extraocular Muscle and the Optic Nerve. In Atlas of Ophthalmic Ultrasonography and Biometry - Shammas. St. Louis, C.V. Mosby Co. 1984 pg 212 - 215.
McNutt L.C. Kaefring S L, Ossoining K C. Echographic measurement of extraocular muscles. In : White D. Brown R E eds. Ultrasound in Medicine. Vol 3A : Clinical Aspects, New York : Plenum Press. 1977 pp 927 - 932.
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[Figure - 1], [Figure - 2]
[Table - 1]