«AIOS, CME SERIES (No. 24) Diagnostic Ultrasonography of the Eye Sushil Kumar Ruchi Goel ALL INDIA OPHTHALMOLOGICAL SOCIETY This CME Material has been ...»
AIOS, CME SERIES (No. 24)
of the Eye
ALL INDIA OPHTHALMOLOGICAL SOCIETY
This CME Material has been supported by the
funds of the AIOS, but the views expressed therein
do not reflect the official opinion of the AIOS.
(As part of the AIOS CME Programme)
Published April 2011
ALL INDIA OPHTHALMOLOGICAL SOCIETY
For any suggestion, please write to:
Dr. Lalit Verma (Director, Vitreo-Retina Services, Centre for Sight) Honorary General Secretary, AIOS Room No. 111 (OPD Block ), 1st Floor Dr. R.P. Centre, A.I.I.M.S., Ansari Nagar, New Delhi – 110029 (India) Tel. : 011-26588327; 011- 26593135 Email : email@example.com; firstname.lastname@example.org Website : www.aios.in Contents Diagnostic Ultrasonography of the Eye Introduction 1 Examination Techniques and 4 Intraocular Diseases Orbital Ultrasonography 24 All India Ophthalmological Society Office Bearers (2008-10) President Dr. Rajvardhan Azad President Elect Dr. A.K. Grover Vice President Dr. N.S.D. Raju Hony. General Secretary Dr. Lalit Verma Joint Secretary Dr. Ajit Babu Majji Hony. Treasurer Dr. Harbansh Lal Joint Treasurer Dr. Yogesh C. Shah Editor IJO Dr. Barun K. Nayak Edior Proceedings Dr. Debasish Bhattacharya Chairman Scientific Committee Dr. D. Ramamurthy Chairman - ARC Dr. S. Natarajan Immediate Past President Dr. Babu Rajendran Office Bearers (2011-13) President Dr. A.K. Grover President Elect Dr. N.S.D. Raju Vice President Dr. Anita Panda Hony. General Secretary Dr. Lalit Verma Joint Secretary Dr. Sambasiva Rao Hony. Treasurer Dr. Harbansh Lal Joint Treasurer Dr. Ruchi Goel Editor IJO Dr. S. Natarajan Edior Proceedings Dr. Samar Kaumar Basak Chairman Scientific Committee Dr. D. Ramamurthy Chairman - ARC Dr. Ajit Babu Majji Immediate Past President Dr. Rajvardhan Azad About CME.....
Dear Colleagues, As I write about this CME, I am reminded of a Court Case against an Ophthalmologist wherein Diagnostic Ultrasound of the Eye, through advised, was not done. Hence the need & usefulness of this CME series No. 24 by AIOS.
Preferably to be done by the examining Ophthalmologist himself - In hazy / opaque media, ultrasound helps us `SEE` what we can't. In clear media, ultrasound helps in tissue characterization.
Although largely surpassed by CT scan (mainly because of lethargy or lack of training on part of Ophthalmologist). Ultrasound offers wealth of useful information, as outlined in this very useful and handy booklet authored by Drs Sushil Kumar & Ruchi Goel.
Hope, our members will find it useful in their day to day practice.
Dr. Yogesh Shukla Dr. Gaurav Luthra (Central Zone) (Central Zone) email@example.com firstname.lastname@example.org (M) 09314614932 (M) 09412059188 Foreword Dear Colleagues, It has been said that ocular ultrasound takes a weekend to learn and a lifetime to master. But I do not agree with this fully as I feel learning is a steep process and hence everyone should learn thoroughly. Significant training goes into learning what various ocular pathologies look like in a 2D cross-sectional view. Clearly, this is a bit more complicated than taking a simple IOP measurement. Nevertheless, B-scan ultrasonography is a particularly important part of an ophthalmologist's armamentarium. But in the same way that our proficiency with the technology has improved with time and experience, so have the diagnostic tools. Innovations in image resolution, acquisition, and subsequent digital image evaluation, provide for a higher level of diagnostic confidence than before.
When direct observation of intraocular anatomy is obscured, the B-scan is the tool of choice for the evaluation of the eye and its orbit.
With understanding of the indications for ultrasonography and proper examination technique, one can gather a vast amount of information not possible with clinical examination alone.
In this issue of AIOS CME series titled “Diagnostic Ultrasonography Of the Eye”, the authors have presented the basics of this diagnostic tool including the principles, indications and techniques in a simplified and illustrated manner. It also gives a clear understanding of echographic characteristics of various ocular pathologies. I am sure this will stimulate every ophthalmologist to know about Ultrasonography and those interested will master the technique all for the benefit of the patients.
I would like to appreciate the efforts of Dr Sushil Kumar and Dr Ruchi Goel in compiling an excellent practical guide on Ophthalmic Ultrasonography.
Prof. (Dr.) S. Natarajan Chairman ARC (2010-11) Chairman and Managing Director Aditya Jyot Eye Hospital Pvt. Ltd.
Prof. of Ophthalmology Maharashtra University of Health Sciences Visiting Prof. The Tamil Nadu MGR Medical University
IntroductionThe emergence of ultrasonography as a diagnostic tool has steadily increased eversince it was first used in the field of Ophthalmology by Mundt and Hughes. Oksala et al reported the sound velocities in the various components of the eye.2 Baum and Greenwood3 came up with two dimensional, immersion scan which was subsequently improved upon by Purnell and 4,5 6 Coleman. Contact Bscan was introduced by Bronson and it being portable, became part of everyday use in ophthalmology. There have been constant improvements in both, the standardized Ascan (Time amplitude scan) and Bscan( Brightness mode, two dimensional scan).
Standardization of Ascan was carried out by Ossoinig He later combined the standardized Ascan instrument with contact Bscan, which ultimately led to the development of Standardized Echography, a diagnostic modality for highly accurate detection and differentiation of oculo-orbital disorders. Lately colour Doppler ultrasound has become a part of the present day's Standardized Echography.
Ultrasonography is used for
•Biometry (Ascan) for axial length and corneal thickness measurement.
•Standardized Ascan (diagnostic) for the echostructure assessment. It is a part of the Bscan in most of the contemporary machines with cross vector facility.
•Diagnostic Bscan (two dimensional) has to be coupled with the standardized Ascan to arrive at a correct diagnosis.
•Doppler ultrasonography is especially important in vascular lesions with different blood flow rates.
During the echoexamination the two scans, A & B are complimentary
AIOS, CME SERIES (No. 24)
to each other. Since ultrasonography is a dynamic procedure, a real time evaluation for diagnosis is possible. This is in contrast to radiological evaluation where still pictures are obtained.
During examination, the following systematic approach is
1. Screening for lesion detection: A + Bscan.
2. Topographic examination for shape, border, location and extension (if possible) of the lesion: Bscan.
3. Quantitative Echography to know the reflectivity, sound attenuation & internal structure of lesion. It helps in determining the texture of the lesion: A scan.
4. Kinetic echography provides information about the mobility, aftermovement and vascularity (Valsalva manoeuvre) on Bscan. It also includes colour Doppler assessment for blood flow.
Indications for Ultrasonography Ophthalmic ultrasonography is a special investigation and it is mandatory that a detailed history, ophthalmic examination, relevant investigations and a provisional diagnosis be provided to the ultrasonologist. To reiterate, all the tests and investigations are complimentary to arrive at the final diagnosis. One must also keep in mind the danger of infection while ordering for ultrasonography in open globe injuries and freshly operated cases! In a nutshell, a comprehensive work up and its judicious use help in optimal use of ultrasonography in interpretation of the various ocular disorders.
Ultrasonography is used for:
1. Evaluation of intraocular details obscured from visualization by the ocular media opacities.
2. Evaluation of retinochoroidal lesions especially tumors even with clear media.
Introduction for Ultrasonography
3. Differentiation of solid from cystic and homogenous from heterogeneous masses.
4. Examination of retrobulbar soft tissue masses and normally present orbital structures (to differentiate proptosis from exophthalmos).
5. Identification, localization and measurement of non radioopaque/radio-opaque foreign bodies. Assessment of collateral damage in trauma cases.
6. Biometry and pachmetry.
7. Follow up evaluations.
1. Mundt GH, Hughes WE. Ultrasonics in ocular diagnosis. Am J Ophthalmol 1956; 41:488Oksala Lehtinen A. Diagnostic value of ultrasonics in ophthalmology. Ophthalmologica 1957; 134:387-395.
3. Baum G, Greenwood I. The application of ultrasonic location, techniques to ophthalmology:
theoretic considerations and acoustic properties of ocular media: Part 1, Reflective properties. Am J Ophthalmol 1958;46:319-329.
4. Purnell E W. B mode orbital ultrasonography. Int Ophthalmol Clin 1969;9:643-665.
5. Coleman D J, Lizzi FL, Jack RL. Ultrasonography of the eye and orbit. Philadelphia: Lea & Febiger,1977.
6. Ossoinig KC. Standardized echography: basic principles, clinical applications and results.
Int Ophthalmol Clin. 1979; 19:127-210.
7. Byrne SF, Green RL. Examination techniques for the globe in Ultrasound of the Eye and Orbit, Mosby year book, 1992, page 42.
AIOS, CME SERIES (No. 24)
Examination Techniques & Intraocular Diseases Probe positions and marker direction Ascan probe is a small, pencil sized probe without a mark and easy to manoeuvre. With this probe the ultrasound beam are parallel and nonfocussed. The probe should be placed at right angle to the area of interest in order to obtain appropriate spike height and thereby maximum information. The probe can be kept directly over the globe after local anaesthesia or on the lid skin for which the overall gain of the machine has to be increased by 3-5db.
Most of the scanners have standardized Ascan that is the probe is of 8MHz emitting parallel sound beam of 5mm width at the highest decibel gain and 0.5mm at the lowest. The sound amplification in these scanners has S-shaped amplifier with flat upper and lower curves and a steep mid segment with a dynamic range of 33-36db. A test tissue block is provided to set the gain in the machine.
Bscan probes on the other hand are thick, with a mark and emit focussed sound beam at a frequency of 10MHz. Pictures obtained with Bscan probe are two dimensional as compared to Ascan probe.
The mark on the Bscan probe indicates beam orientation so that the area towards which the mark is directed appears at the top of the echogram on display screen. Bscan probe can also be put directly on the anaesthetized globe after applying eye speculum; but mostly the Bscanning is done transpalpebrum with slightly increased overall gain.
To obtain high quality Bscan pictures one must ensure that
•Lesions are placed in the center of the scanning beam
• beam is perpendicular to the interfaces at the area of The interest
Exam. Techniques & Intraocular Diseases
• lowest possible decibel gain consistent with the The maintenance of adequate intensity should be used to optimize the resolution of images.
Bscan pictures can be obtained by axial, transverse and longitudinal sections.
During the procedure the probe is moved from limbus to fornix in different clock hour meridians and the picture seen is of diagonally
opposite meridian as follows:
Probe can be moved antero-posteriorly as well as sideways. Patient is instructed to fix the gaze so that the probe is perpendicular to the area being examined. (Figure 1,2)
For macular screening, the four basic Bscan probe positions that allow perpendicular sound beam exposure to the macula are AIOS, CME SERIES (No. 24) horizontal axial, vertical transverse, longitudinal and vertical macula approaches. In axial section the probe is placed over the anaesthetized cornea and the beam is directed towards the posterior pole. In this section there is marked attenuation of the sound beam due to the crystalline lens in the path so the picture may not be suitable for macular thickness measurement. The lens is avoided by placing the probe at the limbus and it is 9.00 P position in the right eye and
3.00 P position in the left eye.
Axial section: The patient fixates in the primary gaze and the probe is placed on the globe and directed axially. Depending on the clock hour location of the marker, axial-horizontal, axial-vertical and axialoblique pictures are obtained. These sections demonstrate lesions at the posterior pole and the optic nerve head.
Transverse section: The mark is kept parallel to the limbus and probe is shifted from limbus to the fornix and also sideways. This scan gives the lateral extent of the lesion.
Longitudinal section: The mark is kept at right angle to the limbus to determine the antero-posterior limit of the lesion. (Figure 3) Figure 3 With contact type of scanning there is a dead zone of about 7.5mm adjacent to the probe, so that the lesions in this region are missed. To visualize this area, one can keep the probe on the opposite side at right angle or use immersion scan technique.
For echoexamination, ultrasound uses high frequency sound waves of 20,000 cycles/sec. These sound waves have different velocities in
different media as given below: