IT Standards in Ophthalmology Print

. . . user-friendly explanations for HL7, SNOMED, DICOM, XML, BDT


HL 7 (Health Level 7)
The quality of modern software can be measured by its ability to integrate with other systems. For this reason, an EMR (electronic medical record) system must include import and export interfaces to practice management programs and possibly other external departmental programs. The most widely used standard for this type of demographic and billing data exchange is HL7, an intelligent and thorough protocol and format description.

The HL 7 standards were established to create industry-wide plug-and-play operability in healthcare data, in other words, to facilitate the electronic interchange of clinical, financial and administrative information among independent healthcare oriented computer systems; e.g., hospital information systems (HIS), clinical laboratory systems, enterprise systems and pharmacy systems.

SNOMED (Systemized Nomenclature for Medicine)

SNOMED is one of the key EMR-based medicine-wide standards groups. SNOMED was introduced in September 1993 and is traceable to its roots in the early 1960s as SNOP - the Systematized Nomenclature for Pathology.  Conceived from the beginning as a system for representing clinical information; it is unlike ICD-9 and CPT4, and not used for billing purposes.

The American Academy of Ophthalmology (AAO) and the American College of Ophthalmology contributed to the SNOMED database, which was developed and maintained by SNOMED International, a not-for-profit division of the College of American Pathologists.  SNOMED, considered the most comprehensive collection of terminology in medical informatics, was created for indexing the entire medical record, including signs and symptoms, diagnoses, and procedure. Its unique multi-axial design allows for full integration of all medical information in the electronic medical record into a single data structure.  A number of separate codes, one per axis, might constitute a diagnosis; for example, lung (topographical axis) plus granuloma (morphological axis) plus fever (functional axis) plus mycobaterium tuberculosis (etiology axis) might add up to a diagnosis of tuberculosis (disease axis).

The SNOMED International classification system contains 11 separate modules with more than 144,000 terms and term codes and has been partially or completely translated into ten dialogue languages.


DICOM (Digital Imaging and Communications in Medicine)

DICOM was initiated by the American College of Radiology and the National Electrical Manufacturers' Association. Since 1996, DICOM has expanded its scope from radiology and cardiology imaging to include visible light imaging (e.g., pathology, endoscopy, ophthalmology), imaging-related therapy (radiation therapy), reporting about findings, and information exchange at the boundary between imaging systems and information systems. DICOM has become the de facto imaging standard for medicine.
It is a detailed specification that describes a way to format and exchange images (as in sending images, printing, query/retrieval, and media storage) and associated information, such as the text describing the image.  The DICOM standard applies to the operation of the interface that transfers data in and out of an imaging device (media devices and computer network connections that address the communication and storage of images). Dissimilar imaging modalities such as computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), nuclear medicine, ultrasound, x-ray, digitized film, video capture (eg. slit lamp imaging, ultrasound, color fundus imaging, fluorescein & ICG retinal angiography) and other camera systems require a DICOM interface to communicate with each other.  Obviously, imaging falls squarely in the path of the EMR and how it is defined affects how vendors develop systems to store images.  The DICOM standard has been implemented for a number of medical products already, and it is supported by industry and professional societies in the United States, as well as internationally.
It is important to understand that one of the major goals of DICOM is to enable interoperability. Interfacing, in the sense of the mechanical and electronic connection of equipment, is difficult, but even this is not sufficient for operation to be transparent to the user.  As an example, consider one person making a telephone call to a stranger to ask about fixing an automobile engine. At a low level, communication involves dialing the correct phone number. This establishes a link between the two people.  But, if the two people do not speak the same language, they will not be able to communicate. Even if both speak the same language, if their understanding of car engines is vastly different, they will not be able to communicate about the task at hand (fixing the engine).  Successful communication requires not only that the individuals have the correct telephone number (network address) and establish a telephone connection, but that they agree on the language to speak and that they negotiate the level at which they have a common understanding (the presentation context).  In this telephone example, the task of interfacing could be thought of as the making of the telephone connection and establishing that the connection is to the right destination.  For interoperation to occur, that is, for the two telephone parties to communicate and comprehend their tasks, an understanding of the data and its context is necessary.  DICOM provides the tools for this in the form of the negotiation capability and the object-oriented design.  The former allows understanding of capabilities, and the latter of context.  Using DICOM does not guarantee interoperability, but it does make it easier for users and manufacturers to achieve.

DICOM.VL (Visible Light)
DICOM.VL is the correct descriptor of the standard created for exchanging complex image data (e.g. fundus camera, slit lamp video cameras, etc.).

DICOM.SR (Structured Report)
DICOM.SR plays an important role in the exchange of clinical reports and doctors letters with or without attached images. In DICOM.SR, the standardization of terminology is an important element that has gained recognition by the AAO (American Academy of Ophthalmology) and the SNOMED editorial board alike Microsoft's ActiveX technology requires the implementation of object linking and embedding (OLE) technology to easily merge data with such products as Microsoft Word, Excel, and Microsoft Access, as well as Web Pages and WordPerfect.

Internet Technologies and Standards

The Internet completely changed the IT world during the last 3 years. Operating systems and data protocols make local LAN Internet compatible and part of a giant global network. Protocols like TCP/IP are dominating old NetWare standards today. HTML is now the standard for user interfaces. The main trend is now on our doorstep: XML (extensible markup language).  This new data language will allow independent platforms to exchange structured data in all areas of business, science and healthcare. XML will become the melting pot for the major trends (Internet technologies, structure data processing, component orientation).


XML for Healthcare
XML will be the standard of the future for all areas of information technology and is ideally suited as a global form of communication in the eyecare field.  The XML standard is also strongly supported by HL7, so much so, that a separate workgroup was established for the development of "XML for Healthcare".
Structured data processing is replacing text orientation and data objects and data models are becoming more and more complex.  Since common text documents can be stored and only viewed, they are rather useless for further data processing. Structured data objects, however, open up a complete new world of retrieval, research, and combination within information technology. The markup language area is an excellent example for this trend.  HTML as a display concept will disappear and will be replaced by the intelligent XML structured language.  This trend is extremely important for medical informatics, only structured data can give more complex overviews and can support sophisticated data models.


In the area of medical data exchange, the BDT standard (data transfer of findings) was developed in Germany in the early 1990's by the KBV (Kassenärztliche Bundesvereinigung) and the ZI (Zentralinstitut). Based on this original platform, BDT-A was then developed solely for ophthalmology and is supported by software vendors in the field.