AK
A.J. Knulst
info
Please Note
<p>This page displays the records of the person named above and is not linked to a unique person identifier. This record may need to be merged to a profile.</p>
10 records found
1
Journal article
(2026)
-
Arjan J. Knulst, Vivian Van Asperen, Nabin Gautam, R. Geerts, Geert Ten Have, Sophia Hou, Alexandra Neumann, Michael Smith, Jenny Dankelman
Objectives
Total ossicular replacement prostheses are commonly used to restore hearing in the conductive hearing impaired. However, total ossicular replacement prostheses are expensive and scarcely available in low- and middle-income countries. Therefore, the aim was to develop and validate an open-source design of a total ossicular replacement prosthesis that can be produced locally for low- and middle-income countries hospitals.
Methods
Based on input from literature and clinicians a design was made and verified. Accuracy, re-bending safety, cadaver ear fitting, sound transmission and production learning curves were tested.
Results
A titanium sheet metal total ossicular replacement prosthesis, costing 9 euro, showed accurate dimensions, surgeons showed short learning curves, and sound transmission was similar to commercial total ossicular replacement prostheses. Re-bending tests demonstrated bending corrections could be safely done. Good cadaver ear fitting could be demonstrated, without conflicts between the titanium sheet metal total ossicular replacement prosthesis and anatomical features.
Conclusion
The titanium sheet metal total ossicular replacement prosthesis design has proved to be feasible for implementation in low- and middle-income countries. ...
Total ossicular replacement prostheses are commonly used to restore hearing in the conductive hearing impaired. However, total ossicular replacement prostheses are expensive and scarcely available in low- and middle-income countries. Therefore, the aim was to develop and validate an open-source design of a total ossicular replacement prosthesis that can be produced locally for low- and middle-income countries hospitals.
Methods
Based on input from literature and clinicians a design was made and verified. Accuracy, re-bending safety, cadaver ear fitting, sound transmission and production learning curves were tested.
Results
A titanium sheet metal total ossicular replacement prosthesis, costing 9 euro, showed accurate dimensions, surgeons showed short learning curves, and sound transmission was similar to commercial total ossicular replacement prostheses. Re-bending tests demonstrated bending corrections could be safely done. Good cadaver ear fitting could be demonstrated, without conflicts between the titanium sheet metal total ossicular replacement prosthesis and anatomical features.
Conclusion
The titanium sheet metal total ossicular replacement prosthesis design has proved to be feasible for implementation in low- and middle-income countries. ...
Objectives
Total ossicular replacement prostheses are commonly used to restore hearing in the conductive hearing impaired. However, total ossicular replacement prostheses are expensive and scarcely available in low- and middle-income countries. Therefore, the aim was to develop and validate an open-source design of a total ossicular replacement prosthesis that can be produced locally for low- and middle-income countries hospitals.
Methods
Based on input from literature and clinicians a design was made and verified. Accuracy, re-bending safety, cadaver ear fitting, sound transmission and production learning curves were tested.
Results
A titanium sheet metal total ossicular replacement prosthesis, costing 9 euro, showed accurate dimensions, surgeons showed short learning curves, and sound transmission was similar to commercial total ossicular replacement prostheses. Re-bending tests demonstrated bending corrections could be safely done. Good cadaver ear fitting could be demonstrated, without conflicts between the titanium sheet metal total ossicular replacement prosthesis and anatomical features.
Conclusion
The titanium sheet metal total ossicular replacement prosthesis design has proved to be feasible for implementation in low- and middle-income countries.
Total ossicular replacement prostheses are commonly used to restore hearing in the conductive hearing impaired. However, total ossicular replacement prostheses are expensive and scarcely available in low- and middle-income countries. Therefore, the aim was to develop and validate an open-source design of a total ossicular replacement prosthesis that can be produced locally for low- and middle-income countries hospitals.
Methods
Based on input from literature and clinicians a design was made and verified. Accuracy, re-bending safety, cadaver ear fitting, sound transmission and production learning curves were tested.
Results
A titanium sheet metal total ossicular replacement prosthesis, costing 9 euro, showed accurate dimensions, surgeons showed short learning curves, and sound transmission was similar to commercial total ossicular replacement prostheses. Re-bending tests demonstrated bending corrections could be safely done. Good cadaver ear fitting could be demonstrated, without conflicts between the titanium sheet metal total ossicular replacement prosthesis and anatomical features.
Conclusion
The titanium sheet metal total ossicular replacement prosthesis design has proved to be feasible for implementation in low- and middle-income countries.
Journal article
(2025)
-
Arjan J. Knulst, Salome Berger, Jan Carel Diehl, Jorijn van den Boom, Inge Bosch, Noa Nicolai, Suraj Maharjan, Eileen Raaijmakers, Chang Lung Tsai, Lisa van de Weerd, Jenny Dankelman
Negative Pressure Wound Therapy (NPWT) is a treatment that promotes healing of chronic wounds. Despite high prevalence of chronic wounds in Low- and Middle-Income Countries (LMICs), NPWT devices are not available nor affordable. This study aims to improve chronic wound care in LMICs by presenting the Wound Care (WOCA) system, designed for building, testing and use in LMICs. Design requirements were formulated using input from literature, ISO standards, and wound care experts. The WOCA design was developed to provide safe, portable, user-friendly and affordable NPWT to patients in LMICs. The design features an adjustable operating pressure ranging from −75 to −125 mmHg, a battery for portability, a 300 ml canister, overflow protection, and system state alarms. An Arduino controls the pressure and monitors the system state. Three prototypes were developed and built in Nepal, and their performance was evaluated. Pressure control was 125 ± 10 % mmHg, internal leakage was 7.5 ± 4.3 mmHg/min, reserve capacity was 189 ± 16.9 ml/min, and overflow protection and alarm systems were effectively working. Prototype cost was approximately 280 USD. The WOCA demonstrates to be a locally producible NPWT device that can safely generate a stable vacuum. Future research will include clinical trials situated in LMICs.
...
Negative Pressure Wound Therapy (NPWT) is a treatment that promotes healing of chronic wounds. Despite high prevalence of chronic wounds in Low- and Middle-Income Countries (LMICs), NPWT devices are not available nor affordable. This study aims to improve chronic wound care in LMICs by presenting the Wound Care (WOCA) system, designed for building, testing and use in LMICs. Design requirements were formulated using input from literature, ISO standards, and wound care experts. The WOCA design was developed to provide safe, portable, user-friendly and affordable NPWT to patients in LMICs. The design features an adjustable operating pressure ranging from −75 to −125 mmHg, a battery for portability, a 300 ml canister, overflow protection, and system state alarms. An Arduino controls the pressure and monitors the system state. Three prototypes were developed and built in Nepal, and their performance was evaluated. Pressure control was 125 ± 10 % mmHg, internal leakage was 7.5 ± 4.3 mmHg/min, reserve capacity was 189 ± 16.9 ml/min, and overflow protection and alarm systems were effectively working. Prototype cost was approximately 280 USD. The WOCA demonstrates to be a locally producible NPWT device that can safely generate a stable vacuum. Future research will include clinical trials situated in LMICs.
Journal article
(2025)
-
A.J. Knulst, F.A. van den Bogaert, A.H. Kuipers, L.J. Roelofs, J. Dankelman, Wim Brandsma, Corine Knulst-Verlaan, Suraj Maharjan
Peripheral autonomic nerve function (ANF) impairment (ANFI) can be one of the first indicators for leprosy or leprosy neuropathy. However, within leprosy, hardly any ANF assessment methods are used in current practice. Skin temperature could be a proxy measure to assess ANF. Therefore, this research aims to explore whether low-cost infrared (IR) video thermography can be used as an ANF assessment tool by measuring the skin temperature response (STR) of human hands before, and after applying a cold pressor test (CPT). A protocol was defined to perform a baseline measurement, apply CPT, and record the resulting STR curve during 15 minutes. An IR video camera connected to a mobile phone was selected as sensor. A setup was developed to immobilize the position of the hands and fingers relative to the camera. A Python script was developed to extract the hand palm skin temperature STR curve from an IR video for 12 ulnar and median innervated regions of interest (ROI) in 1s intervals. A Matlab script was developed to post-process the raw temperature data into filtered data. This data is used to calculate key metrics that describe the STR curve. This approach was evaluated on technical accuracy and precision by comparing IR data for 3 cameras to a reference sensor. The variability caused by the observer analyzing the data was studied by analyzing the same video 5 times by 2 observers. The subject variability was studied by enrolling 7 subjects into a pilot, testing them daily for 5 consecutive days. The results show a high mean Interclass correlation of 0.94 between the 3 IR cameras and the reference sensor. Bland-Altman plots show a mean accuracy of +0.090°C between the cameras and the reference, and a variation between −1.30 and +1.50°C. High agreement was shown between observers analyzing the data. The pilot test showed high variability in STR curve within subjects. Although the general shape of the STR was similar, the location of the steep increase in recovery varied strongly within and between subjects. This study shows that a low-cost, portable IR camera can be used to measure STR of human hands after CPT. A pilot study showed high subject variability for repeated testing of the STR curve. Future research is needed to establish its value in assessing ANF in leprosy patients or other systemic and local neuropathies and traumatic nerve conditions.
...
Peripheral autonomic nerve function (ANF) impairment (ANFI) can be one of the first indicators for leprosy or leprosy neuropathy. However, within leprosy, hardly any ANF assessment methods are used in current practice. Skin temperature could be a proxy measure to assess ANF. Therefore, this research aims to explore whether low-cost infrared (IR) video thermography can be used as an ANF assessment tool by measuring the skin temperature response (STR) of human hands before, and after applying a cold pressor test (CPT). A protocol was defined to perform a baseline measurement, apply CPT, and record the resulting STR curve during 15 minutes. An IR video camera connected to a mobile phone was selected as sensor. A setup was developed to immobilize the position of the hands and fingers relative to the camera. A Python script was developed to extract the hand palm skin temperature STR curve from an IR video for 12 ulnar and median innervated regions of interest (ROI) in 1s intervals. A Matlab script was developed to post-process the raw temperature data into filtered data. This data is used to calculate key metrics that describe the STR curve. This approach was evaluated on technical accuracy and precision by comparing IR data for 3 cameras to a reference sensor. The variability caused by the observer analyzing the data was studied by analyzing the same video 5 times by 2 observers. The subject variability was studied by enrolling 7 subjects into a pilot, testing them daily for 5 consecutive days. The results show a high mean Interclass correlation of 0.94 between the 3 IR cameras and the reference sensor. Bland-Altman plots show a mean accuracy of +0.090°C between the cameras and the reference, and a variation between −1.30 and +1.50°C. High agreement was shown between observers analyzing the data. The pilot test showed high variability in STR curve within subjects. Although the general shape of the STR was similar, the location of the steep increase in recovery varied strongly within and between subjects. This study shows that a low-cost, portable IR camera can be used to measure STR of human hands after CPT. A pilot study showed high subject variability for repeated testing of the STR curve. Future research is needed to establish its value in assessing ANF in leprosy patients or other systemic and local neuropathies and traumatic nerve conditions.
Infrared thermography
A scoping review of its possible role in the diagnosis and follow-up of leprosy neuropathy
Summary Neuropathy is a well-known complication of leprosy. Nerve palpation and assessment of motor and sensory nerves are routinely performed at diagnosis in leprosy, which helps establish the diagnosis and, during treatment, monitor the status of somatic nerve function. Assessment of peripheral autonomic nerve function is not commonly practiced for diagnosing leprosy or for diagnosing and monitoring neuropathy. Early impairments in autonomic function, however, may help to establish or confirm a diagnosis and predict the development of clinical leprosy and neuropathy. Several studies, including infrared thermography and electro-neurophysiological studies, have shown the presence of subclinical nerve impairments that may indicate a diagnosis of leprosy or lead to the development of neuropathy. Sudomotor and vasomotor impairments, in the presence of loss of protective sensation, also increase the risk for ulceration, often requiring chronic care. This article provides a brief discussion of the importance and assessment of peripheral autonomic nerve function in leprosy. Its focus is to review articles that have used infrared thermography to assess this function.
...
Summary Neuropathy is a well-known complication of leprosy. Nerve palpation and assessment of motor and sensory nerves are routinely performed at diagnosis in leprosy, which helps establish the diagnosis and, during treatment, monitor the status of somatic nerve function. Assessment of peripheral autonomic nerve function is not commonly practiced for diagnosing leprosy or for diagnosing and monitoring neuropathy. Early impairments in autonomic function, however, may help to establish or confirm a diagnosis and predict the development of clinical leprosy and neuropathy. Several studies, including infrared thermography and electro-neurophysiological studies, have shown the presence of subclinical nerve impairments that may indicate a diagnosis of leprosy or lead to the development of neuropathy. Sudomotor and vasomotor impairments, in the presence of loss of protective sensation, also increase the risk for ulceration, often requiring chronic care. This article provides a brief discussion of the importance and assessment of peripheral autonomic nerve function in leprosy. Its focus is to review articles that have used infrared thermography to assess this function.
Journal article
(2024)
-
Dipendra Kandel, A.J. Knulst, Joshua Riggsbee, Sarah O. Riggsbee, Suman Tamang, Himal Bikram Bhattarai, Mitesh Karn
Introduction. This article details the development and use of a low-cost, custom RMST device for a patient with long COVID who had received positive airway flow support during ICU treatment. By sharing our successful management of respiratory muscle weakness in a severe COVID-19 patient, we aim to contribute to the broader conversation around effective long COVID management. Case Description. A patient with respiratory muscle weakness used a hospital-made RMST device. The training involved ten short forced exhalations per cycle for five cycles, followed by five long forced exhalations held for five seconds. Additionally, the patient learned lower abdominal and box breathing techniques. The patient showed significant improvement, using the RMST device without supplemental oxygen within 24 hours and completely weaned off by day 5. By discharge, the patient could complete the RMST exercise regime and achieved 290 meters in the 6MWT. After six weeks of outpatient therapy, the patient used the RMST device at 80 cm H2O and increased their 6MWT distance to 390 meters. Device Description. The RMST device was designed for in-house production with a 3D-printed PETG cap, base, and plunger, and a standard pen spring. Its design mimicked a standard PEEP valve with a different geometry. The spring closed the valve until a pressure threshold was reached, allowing airflow. The adjustable pressure threshold ranged from −40 to +40 cm H2O, calibrated in 10 cm H2O increments by measuring displaced water column height. Discussion and Limitation. COVID-19 can cause long-term respiratory issues needing proper management and rehabilitation. Inspiratory muscle training benefits those recovering from severe COVID-19 who were weaned from mechanical ventilation. However, the device’s design and production method are unsuitable for large-scale and commercial production. Rehabilitation centers should prepare for postintensive care syndrome in post-COVID-19 individuals, with interprofessional teams addressing various recovery aspects. Early medical attention and therapy can improve patients’ quality of life.
...
Introduction. This article details the development and use of a low-cost, custom RMST device for a patient with long COVID who had received positive airway flow support during ICU treatment. By sharing our successful management of respiratory muscle weakness in a severe COVID-19 patient, we aim to contribute to the broader conversation around effective long COVID management. Case Description. A patient with respiratory muscle weakness used a hospital-made RMST device. The training involved ten short forced exhalations per cycle for five cycles, followed by five long forced exhalations held for five seconds. Additionally, the patient learned lower abdominal and box breathing techniques. The patient showed significant improvement, using the RMST device without supplemental oxygen within 24 hours and completely weaned off by day 5. By discharge, the patient could complete the RMST exercise regime and achieved 290 meters in the 6MWT. After six weeks of outpatient therapy, the patient used the RMST device at 80 cm H2O and increased their 6MWT distance to 390 meters. Device Description. The RMST device was designed for in-house production with a 3D-printed PETG cap, base, and plunger, and a standard pen spring. Its design mimicked a standard PEEP valve with a different geometry. The spring closed the valve until a pressure threshold was reached, allowing airflow. The adjustable pressure threshold ranged from −40 to +40 cm H2O, calibrated in 10 cm H2O increments by measuring displaced water column height. Discussion and Limitation. COVID-19 can cause long-term respiratory issues needing proper management and rehabilitation. Inspiratory muscle training benefits those recovering from severe COVID-19 who were weaned from mechanical ventilation. However, the device’s design and production method are unsuitable for large-scale and commercial production. Rehabilitation centers should prepare for postintensive care syndrome in post-COVID-19 individuals, with interprofessional teams addressing various recovery aspects. Early medical attention and therapy can improve patients’ quality of life.
Vacuum-Assisted wound care (VAC) is effective for treating complex wounds, but is hardly available in low-resource settings. An affordable, portable and safe VAC device was developed to treat patients with chronic and complex wounds: the Wound Care (WOCA) Pump. The WOCA safely controls the pressure accurately (+/- 10%) between -70 and -125 mmHg for a total component cost of USD 150. In this research important steps were taken to make VAC therapy more accessible, affordable and safe for marginalised patients in low-resource settings. Next research will aim to assess its safe clinical use.
...
Vacuum-Assisted wound care (VAC) is effective for treating complex wounds, but is hardly available in low-resource settings. An affordable, portable and safe VAC device was developed to treat patients with chronic and complex wounds: the Wound Care (WOCA) Pump. The WOCA safely controls the pressure accurately (+/- 10%) between -70 and -125 mmHg for a total component cost of USD 150. In this research important steps were taken to make VAC therapy more accessible, affordable and safe for marginalised patients in low-resource settings. Next research will aim to assess its safe clinical use.
Surgeons have indicated ergonomic problems with the surgical luminaire, which have been observed to occur during repositioning. The possibility of singularity, within the movement space of the translational subsystem of the current double-arm suspension systems, is confirmed to be the cause of these problems. In this study, a redesign of the translational subsystem is compared to the conventional translational subsystem. A user experiment with 14 participants is setup to compare the redesigned and alternative system. The experiment is performed outside the operating room (OR), with one setup that can be altered between two designs; an uncoupled state with the kinematics of the conventional subsystem, and a coupled state with the redesigned kinematics. Work cost, duration, and jerk cost are compared, as well as NASA TLX score. The work cost of a movement in the conventional uncoupled state is confirmed to depend on the spatial orientation of the mechanism, which is not the case in the new coupled state. Due to these different kinetics, the movement patterns with the coupled mechanism are more consistent between participants, the duration of movements is shorter, less problems occur, and participants are able to better control the movements as demonstrated by lower jerk costs. This result validates the redesign and confirms the hypothesis that a translational subsystem without the possibility of singularity within its movement space will improve luminaire repositioning. The conceptual design can now be used as base for a clinically usable design.
...
Surgeons have indicated ergonomic problems with the surgical luminaire, which have been observed to occur during repositioning. The possibility of singularity, within the movement space of the translational subsystem of the current double-arm suspension systems, is confirmed to be the cause of these problems. In this study, a redesign of the translational subsystem is compared to the conventional translational subsystem. A user experiment with 14 participants is setup to compare the redesigned and alternative system. The experiment is performed outside the operating room (OR), with one setup that can be altered between two designs; an uncoupled state with the kinematics of the conventional subsystem, and a coupled state with the redesigned kinematics. Work cost, duration, and jerk cost are compared, as well as NASA TLX score. The work cost of a movement in the conventional uncoupled state is confirmed to depend on the spatial orientation of the mechanism, which is not the case in the new coupled state. Due to these different kinetics, the movement patterns with the coupled mechanism are more consistent between participants, the duration of movements is shorter, less problems occur, and participants are able to better control the movements as demonstrated by lower jerk costs. This result validates the redesign and confirms the hypothesis that a translational subsystem without the possibility of singularity within its movement space will improve luminaire repositioning. The conceptual design can now be used as base for a clinically usable design.
Visual performance and visual comfort are a combined effect of the illumination characteristics and the illuminated objects. Current surgical lighting systems have a fixed shape illumination pattern, whereas the wound and surroundings have a variable shape and characteristics. A lighting system that is able to adapt its shape and light distribution to the characteristics of the wound might improve visual performance. This paper describes the development of a new concept for lighting using bendable strips with LEDs. The basic idea of placing LEDs on a bendable surface is very simple and elegant. To achieve a functional system, the effects of the different design choices, such as shape of the strips, number of LEDs, number of strips, and LED power were investigated. The influence of these choices is evaluated by simulation using a computational model to identify the optimal parameters for the design. The final design is evaluated using the computational model and a physical prototype consisting of one luminaire segment. The system is able to produce light fields that can have fairly complex shapes at a good range of different sizes. Recommendations about aspects like spot size and strip number are given. The physical test model indicates that the calculated system functions close to how it would in a real-life situation. Given the results, it expected that a system, which is able to modify the light field in real time and that requires minimal control effort, could improve lighting in the operating room.
...
Visual performance and visual comfort are a combined effect of the illumination characteristics and the illuminated objects. Current surgical lighting systems have a fixed shape illumination pattern, whereas the wound and surroundings have a variable shape and characteristics. A lighting system that is able to adapt its shape and light distribution to the characteristics of the wound might improve visual performance. This paper describes the development of a new concept for lighting using bendable strips with LEDs. The basic idea of placing LEDs on a bendable surface is very simple and elegant. To achieve a functional system, the effects of the different design choices, such as shape of the strips, number of LEDs, number of strips, and LED power were investigated. The influence of these choices is evaluated by simulation using a computational model to identify the optimal parameters for the design. The final design is evaluated using the computational model and a physical prototype consisting of one luminaire segment. The system is able to produce light fields that can have fairly complex shapes at a good range of different sizes. Recommendations about aspects like spot size and strip number are given. The physical test model indicates that the calculated system functions close to how it would in a real-life situation. Given the results, it expected that a system, which is able to modify the light field in real time and that requires minimal control effort, could improve lighting in the operating room.
Directions for surgical capacity developments in Nepal
A population-based assessment
Journal article
(2019)
-
Arjan J. Knulst, Shailvi Gupta, Reinou S. Groen, Dipak Maharjan, Amatya S. Kapendra, Jenny Dankelman, Adam L. Kushner
Objectives: Lack of access to safe surgery is seen as a major issue that needs to be addressed. The aim of this study was to understand which combinations of factors relate to high occurrences of unmet needs and disability in Nepal, and consequently, how to focus future work to maximise impact in this country. Methods: A large population-based survey was conducted in Nepal in 2014 to evaluate the unmet surgical needs that result in disability. Recorded factors included diseased anatomical areas, disease specifics, disease locations, injury types, reasons for having an unmet need and the types of disability. Results: Included in the study were 2695 individuals. The anatomical areas facing the highest disabling unmet surgical need were Head (3.9% of population), Groin/Genitalia (2.2% of population) and Extremities (3.6% of population). Four focus areas could be defined. Increase affordability, availability and acceptability of surgical care to non-traumatic disabling conditions of (i) the eye, and (ii) extremities, and (iii) to traumatic disabling conditions of extremities and finally (iv) increase acceptability of having surgical care for non-traumatic conditions in the groin and genital area. For the latter, fear/no trust was the main reason for receiving no surgical care despite the resulting shame. Conclusions: This study defined four focus areas that showed the largest unmet needs that resulted in a perceived disability. For those areas, affordability, availability and acceptability of surgical need to be addressed through technical developments, capacity building and raising awareness.
...
Objectives: Lack of access to safe surgery is seen as a major issue that needs to be addressed. The aim of this study was to understand which combinations of factors relate to high occurrences of unmet needs and disability in Nepal, and consequently, how to focus future work to maximise impact in this country. Methods: A large population-based survey was conducted in Nepal in 2014 to evaluate the unmet surgical needs that result in disability. Recorded factors included diseased anatomical areas, disease specifics, disease locations, injury types, reasons for having an unmet need and the types of disability. Results: Included in the study were 2695 individuals. The anatomical areas facing the highest disabling unmet surgical need were Head (3.9% of population), Groin/Genitalia (2.2% of population) and Extremities (3.6% of population). Four focus areas could be defined. Increase affordability, availability and acceptability of surgical care to non-traumatic disabling conditions of (i) the eye, and (ii) extremities, and (iii) to traumatic disabling conditions of extremities and finally (iv) increase acceptability of having surgical care for non-traumatic conditions in the groin and genital area. For the latter, fear/no trust was the main reason for receiving no surgical care despite the resulting shame. Conclusions: This study defined four focus areas that showed the largest unmet needs that resulted in a perceived disability. For those areas, affordability, availability and acceptability of surgical need to be addressed through technical developments, capacity building and raising awareness.
The surgical light is an important tool for surgeons to create and maintain good visibility on the surgical task. Chapter 1 gives background to the field of (surgical) lighting and related terminology. Although the surgical light has been developed strongly since its introduction a long time ago, the last decades only minor developments have been made. This lack of significant development suggests that the current state of surgical lighting is perfectly developed and functions without any flaws. However, literature might give a different perspective. Apparently, despite the lack of significant developments in surgical illumination, the current surgical lighting systems are not good enough yet. This thesis aims to identify problems associated with the use of surgical lights and to improve surgical illumination.
...
The surgical light is an important tool for surgeons to create and maintain good visibility on the surgical task. Chapter 1 gives background to the field of (surgical) lighting and related terminology. Although the surgical light has been developed strongly since its introduction a long time ago, the last decades only minor developments have been made. This lack of significant development suggests that the current state of surgical lighting is perfectly developed and functions without any flaws. However, literature might give a different perspective. Apparently, despite the lack of significant developments in surgical illumination, the current surgical lighting systems are not good enough yet. This thesis aims to identify problems associated with the use of surgical lights and to improve surgical illumination.