|Year : 1990 | Volume
| Issue : 4 | Page : 162-163
Ultrasonic errors in analysis of vitreous haemmorhage
Atul Kumar, Lalit Verma, SN Jha, HK Tewari, PK Khosla
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
Pre-vitrectomy errors in diagnostic A & B mode ultrasound may result in affection of the surgical outcome. We have done a retrospective analysis of fifty patients who were screened by both A & B mode echography and analyzed the data which revealed that real-time kinetic echography is required for accurate interpretation of the vitreoretinal status. Besides, quantitative A scan examination also has fallacies due to the echo beam not striking the scierochoroid complex at right angles, and a modification of this technique is suggested. Lastly old retinal detachments may not produce echo-patterns diagnostic of retinal detachments resulting in fallacious interpretation. We recommend that combined A mode and real time B-mode and often repeat echography is essential for accuracy in diagnosis.
Keywords: Vitrectomy, Vitreous haemorrhage, Quantitative Echography, Errors
|How to cite this article:|
Kumar A, Verma L, Jha S N, Tewari H K, Khosla P K. Ultrasonic errors in analysis of vitreous haemmorhage. Indian J Ophthalmol 1990;38:162-3
| Introduction|| |
Pre-operative echographic evaluation of vitreoretinal status in cases of vitreous haemorrhage has become mandatory. This helps the surgeon plan the required strategy during surgery. We analysed fifty consecutive cases of vitreous haemorrhage of varied aetiology ultrasonically, which were then subjected for vitrectomy. Findings were correlated with the observations made on the operating table.
| MATERIAL & METHODS|| |
Fifty consecutive cases of vitreous haemorrhage of at least months duration were evaluated ultrasonogidphically as preoperative assessment to vitreous surgery. The main cause of vitreous haemorrhage was either Eales' disease or proliferative diabetic retinopathy. Cases were selected from the medical ophthalmology clinics of our Ophthalmic Centre.
Both A & B scanning was carried out in all cases. For A scan Kretztechnic 7200 MA (8 Mhz transducer) was used at tissue sensitivity. Quantitative echography I & I I were carried out wherever indicated. Immersion B scan was done, using the Sonometrics Inc. Ophthalmoscan 200 (10Mhz transducer).
| Results|| |
In forty-two cases, prediction based on ultrasonography was found to be correct. In three cases where we anticipated dense membranes, only diffuse haemorrhage was found. In another three cases of proliferative diabetic retinopathy where localised tractional retinal detachment was revealed on ultrasound, the retina was found attached during vitrectomy. In two cases, retina was found detached during surgery though pre-operative ultrasonic screening had revealed only evidence of posterior vitreous detachment (PVD) and organised haemorrhage.
| Discussion|| |
A scan ultrasonographic findings in vitreous haemorrhage were first described by Oksala & Lehtinen in 1957 whereas B Scan findings were highlighted by Baum  Purnell  and Coleman . A and B scan in a case of vitreous haemorrhage while being independently useful, supplement each other to help the surgeon form a mental impression of the vitreo-retinal status. Whereas A scan gives an idea of density and nature of structures encountered based on reflectivity and sound attenuation, B-scan provides exact topographical distribution of vitreoretinal lesions, i.e, a two dimensonal image.
Ultrasound is, and will remain for quite sometime an important source of information for vitreoretinal surgery but careful, patient and often repeat echography, is of paramount importance for accurate interpretation, A scan and real-time B-scanning should be used complementary to each other and not interpreted independently. The important information which a surgeon seeks in diagnostic echography, for cases of vitreous haemorrhage includes, distribution of haemorrhage, presence or absence of posterior vitreous detachment, presence, location and consistency of vitreous membranes, and associated retinal detachment.
Of these, presence of retinal detachment is most impor tant, because this profoundly changes the management of the case. The greatest reflection of ultrasound is obtained when the beam strikes the interface perpendicularly. Beams interfacing tangentially with the in volved tissue result in little reflection. sub It is therefore important to differentiate dense vitreous membranes from retinal detachment. Quantitative echograpny I & II is carried out to achieve this accuracy. Quantitative echography I consists of differentiating various structures depending upon reflectivity. In structures showing reflectivity less than 80% of that of scleral spike, retinal detachment is ruled out. Once reflectivity ofthe structure is 80% or greater as compared' to the scleral spike, quantitative echography II is carried out to know about the nature of tissue in question. , Additional findings of optic nerve attachment of the involved structure is looked for in B-scanning.
In three of our cases, on routine A & B scanning there was suggestion of dense membranes in the posterior vitreous (pre-retinal zone) resulting in a moderately high reflectivity spike (60%) on A scan and linear bright echoes on B scan, suggesting that a thick preretinal membrane formation had resulted which would require membrane peeling and delamination during vitrectomy. But on surgery, only diffuse vitreous haemorrhage was found. It is suggested that this could have resulted from settling of blood on the posterior hyaloid face, [Figure - 1], producing a fallacy in both A & B scanning. This we believe can be avoided employing real-time kinetic echography and repeated scanning, which will result in shifting of the blood and thus avoiding any misinterpretation.
In the Second group of cases, retinal detachment was concluded on quantitative A-scan echography study, but retina was found attached during surgery. Quantitative echography was given more importance that B-scan which had ruled out a retinal detachment. This might have resulted due to a fallacy in classical quantitative echography, when we attempted to obtain the maximum reflectivity from the tissue in question, which was then achieved by hitting the structure by ultrasound beam at right angles. It is quite likely that the probe position may not have been incident to the sclerochoroid complex at a right angle, resulting in a false-negative low reflectivity spike from the sclero-choroid and a fallacious interpretation of retinal detachment thus resulted[Figure - 2]. To overcome this problem, we propose a modification in the conventional proceure. When quantifying the maximum tissue spikes within the vitreous cavity to determine whether they are vitreal membranes, or a retinal detachment, we recommend that the echo-spike from the sclero-choroid complex be also quantified separately and averaged to determine the exact height of this complex. This is done by placing the probe in different quandrants or in the same quadrant. We feel this is necessary because firstly, by the time it strikes the sclero-choroid complex, the sound beam is attenuated, and secondly the sound beam may not strike this complex at a right angle. Hence an averaged and quantified sclero-complex echo sensitivity is read off in decibel values and this is then compared to the sensitivity obtained from that of the pathologic vitreal membrane spike. The difference between the two sensitivity recordings increases the accuracy of quantitative ultrasongoraphy. In our subsequent cases we have used this technique and avoided further mistakes. These cases also call for due attention to be given to B-scan findings. In none of the cases optic nerve attachment was shown. These observations further indicate the useful complementary role of A & B scan in diagnosing retinal detachment.
| References|| |
Oksala A., and Lehtinen A : Diagnostic of detachment of the retina by means of ultrasound. Acta Ophthalmol. 35 : 461 - 67, 1957.
Baum, G.: Problernsin ultrasonographic diagnosis of retinal disease. Am.J. Ophthalmol. 71:723-39, 1971.
Purnell E.W. : Ultrasound in Ophthalmogical diagnosis in : Diagnostic ultrasound. Edited by C. Grossman et al, New York. Plenum Press, 95-109:1966.
Coleman D.J. and Jack B.L. : B-scan ultrasonography in diagnosis and management of retinal detachments. Arch . Ophthalmol.. 90:29-34, 1973.
Shammas H. Jhon : Atlas of Ophthal. Ophthalmic Ultrasonography & Biometry : The C.V. Mosby Company, 112-114,1982.
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[Figure - 1], [Figure - 2]