|Year : 1983 | Volume
| Issue : 7 | Page : 1022-1024
Ocular ultrasound in preoperative evaluation of posterior segment of the eye
Taraprasad Das, P Namperumalsamy
Aravind Eye Hospital, Madurai, India
Aravind Eye Hospital, Madurai
|How to cite this article:|
Das T, Namperumalsamy P. Ocular ultrasound in preoperative evaluation of posterior segment of the eye. Indian J Ophthalmol 1983;31:1022-4
|How to cite this URL:|
Das T, Namperumalsamy P. Ocular ultrasound in preoperative evaluation of posterior segment of the eye. Indian J Ophthalmol [serial online] 1983 [cited 2013 May 23];31:1022-4. Available from: http://www.ijo.in/text.asp?1983/31/7/1022/29735
Since the first application of ultraound to ophthalmology by Mundt and Hughes, it has emerged as an important diagnositc tool for various ocular and orbital abnormalities. In this paper we report, the first one hundred consecutive cases of ultrasonography done in Arvind Eye Hospital to evaluate the posterior segment of the eye in presence of opaque media.
| Materials and methods|| |
The patients were in various age groups and all of them had opaque media either in the form of a dense cataract, occlusio pupil or vitreous haemorrhage where directvisualisation of posterior segment of the eye was not possibel by ophthalmoscope. The instrument used (Ocuscan - 400, Sonometrics system) is a combined system of contact A - and B - scan where a hand held transducer of 10 MHz is placed dicectly over the closed eye lids coupled by a water soulble viscousgel (Aquasonic - 100 Parker Lab.). In this system either A - or B - scan can be displayed separately be depressing a foot control. In A - scan high amplitude echoes are seen from each major tissue interface (cornea, anterior and posterior surfaces of lens, and vitreoretinal interface), and a decaying pattern of closely packed echoes is seen from retrobulbar face. (2) B - scan images obtained when the scanner is in direct contact display a wedge of the eye, in 25°sub sector and by moving along various directions other areas of the eye are seen. In the normal eye, vitreous appears as an acoustically clear cavity; on the A - scan no echoes are seen above the baseline between the posterior lens capsule and the retina and on the B - scan the vitreous appears as a uniformly sonolucent area. (2) The retina in the normal eye apperas on B - scan ultrasonogram as a smooth, concave acoustically opaque (white) surface formed by echoes arising from the vitreoretinal surface. (2) Because the transducer is placed in direct contact of the lids, obstruction by a large electronic artifact of the first few millimeters of tissue adjacent to the transducer face does not allow proper visualisation of the anterior segment of the eye. But visualisation of the posterior segment, chiefly abnormalities of retina and vitreous is unhindred.
Vitreous heamorrhages appear as irregular opaque areas on B - scan which also shows its location, extent and density. Vitreous may appear sonolucent in cases of light and diffuse vitreous haemorrhages, but on the A - scan these low amplitude echoes are well recognised as they are smaller than both vitreous membrane and retina. (3) A detached retina, appears on the B - scan ultrasonograms as a thin continuous accustically opaque (white) line of echoes, separate from and anterior to, echoes from the wall of the globe, attached however, at the optic nerve. (4)
The different indications in our series of one hundred cases and their distribution in the operated cases are shown in [Table - 1]. Of the one hundred cases evaluated ultrasonographically fifty cases were taken for surgery and a comparison was made with the fundus findings after vitrectomy or lensectomy to determine the degree of reliability and predictability of contact ultrasonography in our hands.
| Observations|| |
Out of one hundred eyes on which contact ultrasonographic scanning was done, fifty were operated subsequently in our hospital. The fundus findings following the operation when the media were made clear after lensectomy or vitrectomy, and the morbid pathological findings in. two cases of leucocoria who underwent enucleation after diagnosis of retinoblastoma were compared to the ultrasonographic diagnosis. In 43 out of 50 cases we found our ultrasonic diagnosis to be correct and in seven case our diagnosis was proved to be wrong. The details of these incorrect diagnosis are shown in [Table - 2].
Thus in 10% of cases. we have failed to differentiate and diagnose correctly quadratic retinal detachment from vitreous membrane and in 4% of cases retinal detachment was over diagnosed.
| Discussion|| |
For ease of examination and more accrute interpretation of echo patterns a contact ultrasound unit with both A - scan and B - scan capabilities is being advocated by Coleman and Katz. (5) It allows more complete examinations to be conducted in minutes, with no patient discomfort, through the closed lid. Examination of infants and children is easily accomplised without anaesthesia, and cooperation of child is not very essential.
In our series, the overall accuracy of ultrasonic diagnosis was 86%. In five cases we failed to differentiate vitreous membrane from quadrantic retinal detachment in ultrasonogram and two cases were over diagnosed as retinal detachment when none was actually visualised on the table at the end of the operation. Both these patinets had vitreous haemorrhage, one of diabetic and the other of traumatic origin and the vitreous haemorrhage was partially orgainsed in the posterior vitreous cavity close to the retina; they were found to be pre-retinal vitreous membrane rather then tractional retinal detachment. Jack et al (6) have opined that the areas of ultrasonic diagnostic difficulty lies in total retinal detachment versus vitreous membrane, and in posterior pole traction retinal detachment versus preretinal vitreous membrane.
In spite of our failure in 14% of cases, ultrasonography has helped us immensely in diagnosis and proper evaluation of patients and in planning our operation in cases who were operated. Though there are innumerable examples, worth mentioning is one boy of 14 years who came to us with aphaka in one eye, operated a few years back elesewhere and cataract in the other eye. The aphakic eye had poor visual acutiy and fundus examination by binocular indirect ophthalmoscope revealed high myopia with posterior staphyloma.
Now since there was no means to visualise the fundus by any optical method or to determine-the refractive error because of dense cataractus lens, we clinically assumed that it was a case of complicated cataract and in that case postopertative prognosis was not good. But on ultrasonic scanning, we could actually visualise that the antero-postero diameter of the cataractous eve was much smaller than the other myopic eye (showing posterior stapyloma, apart from increases A-P diameter). So we could profess good visual results after operation and indeed, after lensectomy, the corrected visual acuity was 6/9. Had we not done ultrasonic scanning of the cataractous eye, we could have never known before operation this excellent prognosis nor could we have made his parents to accept for the surgery.
| Summary|| |
One hundred consecutive cases of preoperative ultrasonic evaluation of the posterior segment of the eye in presence of opaque ocular media are analysed. In 14% our ultrasonic diagnosis was wrong; the chief area of misdiagnosis was differentiating vitreous membrane from quadrantic retianl detachment. Our diagnosis was found to be accurate in 86% of cases. The importance and necessity of ultrasonographic scanning when direct visualisation of the posterior segment by normal optical means is not possible due to opaque ocular media are stressed.
| References|| |
|1.||Mundt. G.H. & Hughes, W.F., 1956, Amer. J. Ophth a 1 mol. 41:488-498. |
|2.||Coleman.D.J. Lizzi. F.L. and Jack. R.L.. 1977Ultrasonography of the Eye and orbit pp. 158-213, Lea & Febiger Philadelphia. |
|3.||Coleman, D.J. & Franzen, A.L., 1974, Arch. Ophthalmol. 92:375-381. |
|4.||Coleman. D.J. &Jack. R. L., 1973, Arch. Ophthalmol. 90:29-34. |
|5.||Coleman. D.J. & Katz. L., 1977, Trans. Am. Acad. Ophthalniol. Otolaryngol 88:855. |
|6.||Jack. R.L. Hutton. W.L. & Machemer R.. 1974, Am.J. Ophthalmol 78:265-274. |
[Table - 1], [Table - 2]