New Concepts for Knowledge based Cataract Surgery Assistance
A First Clinical Approach
K. P. Scherer
, C. Rieder
, C. Henninger
, J. Baumeister
and J. Reutelshöfer
Karlsruhe Institute of Technology, Institute for Applied Computer Science,
76344 Eggenstein Leopoldshafen, Hermann von Helmholtz Platz 1, Germany
Denkbares GmbH, Friedrich Bergius-Ring 15, 97076 Würzburg, Germany
Keywords: Knowledge Acquisition, Computer Aided Assistance, Semantic Network, Knowledge Representations,
Knowledge Continuum, Expert System, Decision Support, Surgical Intervention.
Abstract: Concerning optimization of ophthalmosurgical interventions at human eyes, a knowledge based assistance
system is developed to support the decision process of the surgeons before the real operation at the human
eye. This is performed especially for cataract operations, when the real dark lens has to be removed and an
artificial lens system must be implanted. Especially for complicated and complex interventions the
computer-based system will be a helpful tool. The system has to guarantee a fast and efficient access to all
operation relevant information. The result of such a concept should be an enhancement of operational
quality and so an enhancement of the patient contentment. This means a very important factor for the human
life quality.
In the biomechanical system of the human eye, the
intraocular lens is the most important component for
the refraction process with about 30 dioptres to
focus the rays, coming from outside to the retina.
Parallel to the human aging process there is no
possibility to prevent a fix dark cloudy lens and also
there exist no medical treatments. Cataract surgical
interventions at human eyes are the single method,
to replace the old dark cloudy human lens by a new
clear artificial lens (Augustin, 2001). This is
performed about 600.000 per year only in Germany
with increasing number. On the market, a lot of
different lens systems with different haptics, optics,
materials, and power refraction values complicate
the selection of a best system
A special configuration and selection of a patient
related lens system can only guaranteed by a
computer-aided decision support system, which
considers the patient’s need regarding all his earlier
diseases as well as the special clinical measurement
and the fabrication-related intraocular
lens (IOL) features.
Based on computer logical reasoning, the human
surgeon can plan and simulate his intervention by
the software before the action takes place at the real
patient. Figure 1 shows the way from planning the
surgical intervention through regarding the wide
spectrum of lens types to a simulated surgical
process. Dependant on the simulation results, the
operation plan can be changed and optimized.
Figure 1: Planning the special implantation.
dark cloudy
lot of lens
clear artificial
op planning
surgical process
P. Scherer K., Rieder C., Henninger C., Baumeister J. and Reutelshöfer J..
New Concepts for Knowledge based Cataract Surgery Assistance - A First Clinical Approach.
DOI: 10.5220/0004516100640068
In Proceedings of the 8th International Joint Conference on Software Technologies (ICSOFT-EA-2013), pages 64-68
ISBN: 978-989-8565-68-6
2013 SCITEPRESS (Science and Technology Publications, Lda.)
The human expert knowledge is subdivided into four
super classes of knowledge domains:
The patient situation includes all personal data
including his history with all past diseases and his
actual health state. In this situation the patient
related best IOL-implant has to be found. But a lot
of intraocular lenses are available, different in
functionality, form, material, haptics, design, and
refraction power values. To select the best option for
the patient is not trivial.
Additionally, many clinical measurement and
diagnostic methods are available and are applied in
the preoperative situation of the human being. Some
measured values can be wrong when for instance
past diseases are not known.
An additional knowledge domain is the wide
field of the different surgical techniques. The
application of these methods depends also on the
patient situation, the designed IOL, and the
determined diagnostics. This complexity yields a
computer-based structuring of the knowledge to
support the surgeons by logical reasoning including
the explanation of the reasoning process (Figure 2).
These four domains (patient’s situation,
diagnostics, IOL types, and the surgical techniques)
correlate among each other, so the dependencies are
very complex and they are no longer linear. A
formalized description of the different knowledge
domains must be performed. They should be
regarded before the final selection of the IOL and
the implantation at the real patient is done. The
elements of the knowledge domains and the
correlations between them are represented as a
semantic net with predicates, i.e., the ontology. This
structure, especially in combination with an efficient
visualisation is a very important help for the
Figure 2: The different knowledge domains.
A knowledge-based approach is well suited to make
available as well the human expertise as the
background deep knowledge to map the logical
reasoning process to computer software (Studer et
al., 1988). So, the need is to find out formal
structures to manage the different knowledge
domains. The knowledge-based support system is
conceptualized and realized in different semantic
Figure 3: Layer based architecture of the system.
On the basic layer L1, a frame-based information
system is performed with all features of the different
ontologies. The descriptive layer for the interested
information categories is a hierarchical class –
subclass system with a refinement process and
special specification from class to subclass. An
ontology concept consists of the declarative part of
the semantics, the meaning in this knowledge-based
approach, the sources (publications, authors and so
on), and multimedia representations (pictures, tables,
movies) (Benjamin et al., 1998).
On the layer L2, the concept of the semantic
dependencies is subdivided into different types of
relations (predicates), based on natural language.
The knowledge elements of layer L1 can be
correlated by so called weak links, that means
semantic associations between the different items.
They are used to generate a suggestion for the
surgeon, also to consider the semantic neighboured
knowledge domain when regarding a first one. The
surgeon can be guided from one interest of point to
the next in an intelligent manner. An additional type
of relation is performed by a stronger relation like a
rule in a rule-based expert system. If the premises of
the first domain are given, then the second
knowledge items result as conclusion from the
Based on the static description of the concepts in
L1 including their correlations in L2 the reasoning
process in layer L3 depends on the different
OP methods
IOL types
L1: frames of the domains:
IOL types, surgical methods,
diagnostics, patient situation
L2: correlations, dependencies
L3: knowledge processing and reasoning
L4: user interface, explanation, acquisition
correlation types. Weak links can be regarded as a
helpful navigation to neighboured interested
knowledge items in the knowledge base. Strong
links can be used under consistent inference rules in
the predicate calculus 1st order to generate necessary
conclusions in a logical way.
In layer L4 the formulized knowledge is
correlated with the surgeon’s natural language by the
man machine interface. As well the acquisition of
new cataract specific knowledge must be generated
in a user specific efficient manner. Also the
explanation of the performed reasoning process is a
very important tool for controlling the human
decision process.
Concerning an enhancement and optimization of the
decision making process of the ophthalmic surgeons,
there is a need to correlate all information getting
from the patient situation, the latest lens
characteristics, and the instantaneous powerful
methods of the diagnostic equipment.
The assistance system allows for an intelligent
user machine communication (surgeon - assistance
system). The information part of the knowledge
system is combined by an intelligent navigation
through the available knowledge domains of the
cataract surgery net. The semantics is represented by
weak and strong links to associated knowledge
So the intelligent assistance tool for the cataract
surgery has the following advantages when
compared classical software information systems:
- The knowledge base can be extended using a
comfortable graphical knowledge acquisition
component in an easy and consistent manner.
- Furthermore the assistance system supports the
reasoning process of the surgeon and it can
identify the patient-related optimized implantation.
In this sense, a very expensive surgical
intervention can be reduced and the contentment of
the patient will be improved.
- A further available feature is the possibility to use
logical forward and backward chaining
mechanisms in the associated knowledge network
to explain the logical dependencies.
Regarding the above mentioned features, the system
is predestined as a tutorial system for inexperienced
doctors and also a decision support system for
experienced surgeons. In comparison to literature
and books the knowledge-based assistance is a
dynamical system, which can be updated and
extended by the latest cognitions from the experts.
The knowledge base of the applied support
system is considered under two points of view:
Figure 4: The path from the knowledge continuum to
intelligent navigation.
The basic fundament and starting point for
modelling the layer 1 through layer 4 is the
knowledge continuum with the features in the upper
part of Figure 4. In layer 1 to layer 4 the different
knowledge representations are shown.
The frames represent the static multimedia
information (text, pictures, and audio) including the
source information (i.e. http-addresses, literature,
and links). The context and associatives represent
und describe the semantics between the different
information items by weak links, i.e., the
The final aim and the arrived advantage of this
modelled knowledge approach are demonstrated in
the lower part of Figure 4. Based on these features,
this tool is responsible for an intelligent context
sensitive navigation.
multimedia info (texte, mouvie, audio)
representation of semantics
representation of strong relations
visualisation of the semantics
(temporal, causal, free predicates)
knowledge continuum
acquisition of of all surgical relevant
knowledge elements
research and development of wikis
and semantic net structures
formalisation and structuring of the
knowledge elements
intelligent navigation
support of the surgeon by relevant
hiding of non relevant information
easy access to picture, texte audio
access to the semantic correlations
The presented approach is realized by using the
system KnowWE (Baumeister et al., 2011b).
KnowWE is a semantic wiki, i.e., a web-based
knowledge system, extending textual and
multimedia information by ontological annotations
and strong-problem solving methods. Following the
idea of the knowledge formalization continuum
(Baumeister et al., 2011a), all types of knowledge
(formal knowledge but also text and multimedia) are
considered to be part of the knowledge base. In
general, a semantic wiki allows for the collaborative
authoring of the included knowledge base and its
collaborative use.
At the beginning of the project, the ontology was
defined for describing the relevant terms and actions
of the cataract domain. In the next step, the relevant
chapters of an established German textbook for
cataract surgery were transferred to the wiki system
in order to provide suitable information of the
Figure 5: The WISSASS wiki system (original German
Consequently, the textbook corpus was enriched by
ontological annotations populating the initially
defined ontology. In all project phases, different
domain specialists (surgeons) and knowledge
engineers were actively involved. Due to the nature
of the wiki system, the domain specialist is able to
extend the current body of knowledge by further
elements, when necessary.
From the user's view, the wiki distinguishes
restricted knowledge acquisition pages and public
system pages. The restricted knowledge acquisition
pages are only accessible by the knowledge
engineers and the surgeons and include the formal
knowledge definitions. The public pages are
accessible for everyone and they include the
textbook knowledge and the interfaces for browsing
the cataract ontology.
Figure 5 depicts a public page, where the concept
Phakoemulsifikation is described, i.e., a special
method of surgical intervention. The text describes
the requirements and consequences using this
method but also practical advices for implementing
it. From this description, the ontological
neighborhood of the concept can be browsed and the
user can navigate to interesting concepts easily.
Figure 6 shows an excerpt of the visualization for
the concept Phakoemulsifikation with neighboring
ontological concepts having a refining relation.
Figure 6: An excerpt of the ontology visualization (in
German language).
In the future, we are planning to extend the range of
visualization methods to provide more appropriate
navigation structures for the specific browsing
requirements of the users. At the current state of
development, the system includes about 400 pages
providing the textbook knowledge, annotated by
about 360 concepts with about 430 relations. At the
moment, clinical partners evaluate the system for the
last three months.
The most important advantage of the knowledge-
based assistance is the intelligent navigation of the
user (surgeon) through the knowledge continuum.
Based on the visualized network of the semantics
(knowledge elements and their correlations) the
surgeon gets exactly the information that is useful
and necessary for him in the instantaneous situation.
The semantics is of higher order because of
representation of weak and strong links to the
associated knowledge domains. In contrary to
classical information systems the expert system is
easy to extend by graphical knowledge acquisition
features. Also the reasoning process for decisions
can be explained by the visualisation of the logical
path. This assistance yields a better human decision
process and improves the results of the cataract
The research and development of the proposed
cataract surgical assistance system is funded by the
national economical government of Germany. It is
proposed to install a commercial clinical system
based on the results of the presented prototype at
clinical partners. The authors also thank the project
executing organisation AiF in Berlin, which is
responsible for the allocation of the budget to the
research centre and the commercial company.
Augustin, A. J., 2001, Augenheilkunde, Springer Verlag,
Berlin Heidelberg, NewYork, ISBN 3-540-65947-1
Studer, R., Benjamins, R., Fensel, D., 1988, Knowledge
engineering in Principles and methods, Data and
Knowledge engineering Vol 25, p 161-197
Benjamins, V. R., Fensel, D., Gomez Perez, A., 1998,
Knowledge management through ontologies,
Proceedings on the. Int. conf. on Praktical aspects of
Knowledge management (PAKM 98), Basel, Schweiz,
Scherer, K. P., 2009, Hypothesis Generation in the context
of an ophthalmic application, Intern. Conf. on applied
computer science., pp 130, Genua, Italy, Oct. 2009
Baumeister, J., Reutelshoefer, J, Puppe, F., 2011a,
Engineering Intelligent Systems on the Knowledge
Formalization Continuum, International Journal of
Applied Mathematics and Computer Science (AMCS),
Vol. 21
Baumeister, J., Reutelshoefer, J., Puppe, F., 2011b,
KnowWE: A Semantic Wiki for Knowledge
Engineering, Applied Intelligence, Vol. 35, 323-344