For more than three decades, the endowed laboratory led by apl. Prof. Dr. rer. nat. Thomas Bende pursued a single guiding idea: translating physical and engineering principles into ophthalmic practice. Founded in 1991 as the Section for Experimental Ophthalmic Surgery and Refractive Surgery by Professor Benedikt Jean and Dr. Thomas Bende, the group first set out to make laser technology safe for use in the eye, and went on to develop a broad portfolio of instruments and diagnostic methods, many of them in partnership with industry. This page documents the laboratory's principal projects, grouped by research area. (For the wider history of the laboratory and its merger into the Endowed Applied Vision Research Laboratory, see the History page.)

In its founding phase the laboratory focused on characterising ablation processes in corneal tissue. Systematic studies of thermal effects and biomechanical changes provided the physical basis for safe refractive procedures with the excimer laser, and led to methods for preserving postoperative image quality through videokeratometric corneal and wavefront analysis.

Optimized Refractive Keratectomy (ORK-CAM)

Developed in an R&D collaboration with SCHWIND eye-tech-solutions (Kleinostheim), ORK-CAM is a software platform that overcomes the limitations of classical Munnerlyn-based ablation profiles in excimer-laser myopia correction, which tended to flatten the corneal periphery and induce higher-order aberrations. It implements aspheric ablation profiles that preserve the eye's physiological corneal asphericity, and — by coupling topography and wavefront data through Zernike analysis — enables correction of individual higher-order aberrations. The model also compensates for the efficiency loss of peripheral laser delivery and controls pulse geometry. ORK-CAM is an integral component of the SCHWIND laser systems (from ESIRIS to AMARIS).

Laser thermal keratoplasty (LTK)

Laser thermal keratoplasty is a minimally invasive refractive procedure that reshapes the cornea with heat delivered by laser pulses arranged in a peripheral ring, primarily to correct hyperopia and presbyopia. Whereas the procedure was traditionally performed with a pulsed Ho:YAG laser at 2.07 µm, the laboratory developed the LTK 1.9 system together with Rodenstock, using a continuous-wave source at 1.885 µm. Its key advantage is controlled heating of corneal tissue to 65–90 °C without the damaging temperature peaks of pulsed systems. In studies, the macroscopic and microscopic effects of the LTK 1.9 were comparable to the Ho:YAG laser, while its optimised laser–collagen interaction offered potentially more stable results and a higher refractive effect.

A continuous thread through the laboratory's work was the design of innovative instruments for surgery and diagnostics.

Video keratometry combined with optical biometry

The measurement and analysis of corneal topography was a core competence from the laboratory's earliest days. The work is based on the Placido principle, in which concentric rings are projected onto the corneal surface and the reflected image is captured on video and analysed to reconstruct the corneal surface profile. The first Placido topometer developed in Tübingen, the C-Scan, was commercialised by TechnoMed (Germany); after the company closed, a redesigned "Tübinger Placido Topometer" — OphthaSTAR, also marketed as IOLAdvisor — was introduced with a new partner, Hummel AG. Its defining feature was individualised intraocular-lens calculation based on real ray tracing (RRT). This required the instrument to capture, simultaneously and along the optical axis, both corneal topography and ocular biometry (axial length, lens position, anterior chamber depth, and corneal thickness) using partial-coherence interferometry (PCI, begun in cooperation with the Institute of Medical Physics, University of Vienna). Unlike conventional ultrasound biometry, PCI is contact-free, and capturing all relevant anatomical parameters at once allows precise IOL calculation both with standard formulas and via RRT. The clinical validity of this combined approach was demonstrated in several studies.

Stereo pupillometry

Developed in cooperation with Albomed GmbH (Unna), the stereo pupillometer enables the simultaneous, objective measurement of pupil size and light reflexes in the left and right eye at once. By analysing parameters such as light-reflex duration and responses to changes in light intensity, it detects variations in the pupillary response. Its applications range from the assessment of neurological disorders — including under pharmacodynamic conditions — to psychological research on attention and working memory, contributing objective physiological data to neurology and behavioural research.

Hand-held rebound tonometer (IOPen)

Based on research at the University of Tübingen, the hand-held rebound tonometer IOPen was developed in a joint R&D project with Medicel (Switzerland), which also handled its commercialisation and distribution. The goal was a mobile device that measures intraocular pressure (IOP) precisely without anaesthetising the cornea. A dedicated positioning system ensures that each measurement is taken at the correct angle and distance from the cornea — a critical factor for accuracy in hand-held devices. The instrument's agreement with the Goldmann standard was demonstrated in clinical studies.

Förster binocular ophthalmoscope

The Förster spectacle ophthalmoscope is an indirect binocular ophthalmoscope for the detailed examination of the fundus, first developed in close collaboration with Prof. Michael Förster at the University Eye Hospital Tübingen in 1978. At the clinic's suggestion, the laboratory modernised the instrument, replacing the earlier halogen model with an LED version that offers daylight-white illumination and constant colour temperature when dimmed. The long-lived LED source makes the device virtually maintenance-free, generates no perceptible heat at the examiner's head, and runs for long periods on a small lithium-ion battery. Together with the manufacturer Kocher Feinmechanik (Mössingen), the modernised ophthalmoscope received CE certification in 2020.

The laboratory repeatedly introduced new physical measurement principles into ophthalmology, and validated optical coherence tomography (OCT) as a non-invasive, contact-free imaging method for the eye.

Non-contact photoacoustic spectroscopy (NCPAS)

NCPAS uses acoustic signals to identify tissues in real time during laser ablation — for example with excimer lasers — and to monitor the process, with the aim of automating and intelligently controlling corneal laser treatment.

Dielectric spectroscopy (DES)

In cooperation with the Technical University of Berlin, the laboratory studied the electrical properties of biological tissue — particularly the cornea — to measure hydration, temperature, and biomechanical properties. In cooperation with the Tübingen Department of Dermatology, the dielectric properties of skin layers (epidermis and dermis) were characterised to establish reference values for healthy tissue against pathological changes.

Further measurement studies

• High-frequency ultrasound. Complementing NCPAS and DES, high-frequency ultrasound (≥ 50 MHz) was evaluated in cooperation with the Technical University of Berlin to characterise the biomechanical properties of the cornea.
• Non-invasive blood-glucose diagnostics. A study of non-invasive blood-glucose analysis using infrared spectroscopy (2.04–2.4 µm), carried out in the joint project "Innovative Blutzuckerdiagnostik" with the Fraunhofer Institute for Applied Solid State Physics (Freiburg) and the companies Festo and Biocomfort Diagnostics.
• SL 100 lateral-flow analysis system. An all-in-one system for reading and documenting slow lateral-flow tests, developed for the US company Advanced Tear Diagnostics (ATD) for tear-film analysis; a dedicated algorithm predicts the test result before the reaction on the strip is complete.

The laboratory's more recent work concentrated on digitising clinical measurement procedures and on computer-assisted surgery.

Digitised strabismus diagnostics (Harms tangent screen)

This mobile system digitises the measurement of the squint angle, transforming the classical motility analysis on the Harms tangent screen — carried out in at least nine directions of gaze — into a location-independent procedure. Instead of a fixed wall-mounted screen, a flexible projection unit projects the examination scales onto any suitable surface. Because the projected colour can be adjusted digitally, the coloured filter glasses normally used for fusion separation no longer need to be swapped, which considerably simplifies the examination. A compact sensor module fixed to the spectacles uses a 9-axis inertial measurement unit (IMU) to capture head rotation in all three degrees of freedom during fixation, transmitting the data wirelessly via Bluetooth; an integrated distance sensor continuously records the exact distance to the projection surface, so the squint-angle calculation adapts in real time to varying examination distances and keeps data quality consistent regardless of room size. The digital approach also allows other standardised layouts, such as the Hess screen, to be displayed.

Robot-assisted cataract surgery

This project develops a compact robotic assistance system that improves the precision of cataract surgery through robotics and intelligent image processing, executing critical steps such as capsulotomy with micrometre accuracy. Rather than rigidly fixating the eye, a stereo-camera tracking system follows both the eye and the surgical instrument simultaneously and in real time, allowing precise positioning of the robot arm even during small compensatory movements of the patient. Image data define an Active Boundary Control safety zone in which the arm mechanically prevents instruments from entering predefined no-go regions — for example to protect the posterior capsule — while motion scaling filters physiological tremor at the user interface to achieve micrometre positioning. Motors integrated into the user interface provide haptic feedback to the surgeon and an automated limit when manipulating intraocular structures.

Automated slit-lamp diagnostics

A system for the rapid acquisition of standardised, high-quality slit-lamp images for use in patient documentation, telemedicine, and AI training. A patient study is currently ongoing.

The projects on this page reflect research carried out within the Section for Experimental Ophthalmic Surgery and Refractive Surgery and its endowed laboratory. Several of the more recent projects are being continued and further developed within the Endowed Applied Vision Research Laboratory.