Ex Vivo Accommodation Simulator (EVAS)
 This invaluable instrument is able to replicate the same accommodative mechanical system in the live human eye, but in a controlled ex vivo setting. In addition to being able to impart radial stretching forces to simulate accommodation in the crystalline lens, the EVAS is capable of measuring amount of stretch, forces involved in stretching, and most importantly, the associated change in optical power during stretching.
The instrument was developed to support the research activities in the Dynamic Vision project. It enables the prediction of in-eye performance of our prototype polymer gel in an ex-vivo setting without incurring the costs and protracted studies involved with in-vivo testing. This knowledge is fed back into the product development activities. Data on changes in optical power, stretching load and geometrical shape are all recorded for comparisons with measurements taken after the natural lens contents has been removed and replaced with a soft polymer gel.
The technology has also been transferred to collaborators LV Prasad Eye Institute in India and the Bascom Palmer Eye Institute at the University in Miami.
Contact Lens Profilometer
The surface quality and edge shape of a contact lens has a great impact on the fit and comfort of the lens. Measurement of the lens profile allows manufacturing quality to be assessed as well as correlations between lens and edge profiles versus on-eye fitting, comfort and vision. The KE Profilometer was developed to scan the back and front surfaces and edge of a rigid gas permeable contact lens in a continuous sequence, providing a highly accurate view of the lens for the first time.
The KE Profilometer system is based on the technology of reading heads of compact disc players. To read the data stored on the compact disc, the reading head extracts signals from a laser beam reflected from the surface. In the KE Profilometer, the reflected laser provides a detailed ‘map’ of the surface it passes over, with an accuracy of ± 2 μm. (Plastic foodwrap, for example, is between 5 and 10 μm thick).
The original KE Profilometer was developed by Dr Klaus Ehrmann as part of his PhD project and soft contact lens profilometers have subsequently been developed at the Brien Holden Vision Institute. The profilometer has been used in numerous contact lens studies.
Eye Tracker
The Eye Tracker has been utilised in the Bifocal Contact Lens project. Previously unknown biometric data of ocular parameters has been revealed with a custom-built eye tracker instrument. Population-based data was obtained with the image capturing instrument, which leads the eye-ball into different gaze directions, while taking measurements of cornea, pupil and lid positions. This information is of great assistance in evaluating contact lens fitting and on-eye performance.
Micro-Tensometer
The Micro-Tensometer was designed and built to measure the tensile strength of materials in the Corneal Onlay project. Other applications include the toughness assessment of contact lens materials, the characterisation of mechanical properties of intraocular lenses and the compression modulus of the gel in the Dynamic Vision project.
Lid Tensometer
The Lid Tensometer was developed for the high precision measurement of eyelid tension. Eyelid tension, although critical to understanding dry eyes and optimisation of applications such as contact lens designs and plastic surgery, has not previously been measured to any useful level of accuracy. The Tensometer determines lid tension by gripping the eyelashes and pulling the lid while measuring the force exerted by the eyelid. Tensometer data is helping researchers to determine the range of normal lid tension, and how this relates to issues such as contact lens comfort, or pathological or age related changes.
Dr Klaus Ehrmann was awarded the 2000 Da Vinci Award from the British Contact Lens Association for his invention of the lid tensiometer.
Computerised Visual Acuity Charts
The Technology team designed and installed computerised visual acuity charts that are now being used in the International Clinical Trials Centre. A pilot investigation of the traditional letter charts for testing visual acuity confirmed that the computer generated visual targets eliminate the problem of patients memorising letters on the traditional chart and errors caused by manual data entry. It has also enabled the implementation of more sophisticated vision testing techniques.
Optical Quality Analyser (OQA)
The OQA enables researchers to see a wide variety of optical defects of contact lenses, which are not detectable using conventional instrumentation. The OQA was originally developed as a ‘zonometer’, capable of identifying and measuring optic zones on contact lenses, such as the different zones used for reading on bifocal lenses. However researchers quickly realised that they could see a lot more than this.
The instrument passes white light through the lens and through selected obstruction of the refracted light and the associated ‘chromatic aberration’, shows up the refractive power and quality of the lens. The surface may be smooth, but manufacturing problems may have caused variations in the local power of the lens, so that it no longer provides even power over the entire zone. This causes problems to patients, which until the OQA were extremely difficult for practitioners to detect. The OQA is used in BHVI contact lens research and clinical trials.
Oxygen Uptake Rate Measurement Equipment
The cornea is an avascular tissue which absorbs oxygen from the surrounding air to maintain a healthy metabolism. Oxygen uptake is compromised during contact lens wear and can reach dangerously low levels for some lens types or during extended lens wear. Methods and equipment have been developed to measure the uptake rate in vivo under various conditions.
Flow Rate Measurement Equipment
Flow rate measurement equipment to measure the liquid flow rate through materials has been developed and used in associated projects. The instrument provides temperature and humidity control as well as adjustable liquid pressure to simulate a range of intraocular pressures.
CRCERT-Belmonte Aesthesiometer
The Aesthesiometer allows the measurement of corneal and conjunctival sensitivity to various types of stimuli and was developed for use in contact lens research. Using the Aesthesiometer, the Institute's researchers have characterised and mapped threshold responses for the normal ocular surface.
It was found that humans have the ability to successfully distinguish between mechanical, chemical and thermal stimuli applied to both the cornea and conjunctiva, and are carrying out a range of further studies such as characterising changes in nociceptor response that occur during contact lens wear.
Replicas of the instrument were installed at several research collaborators, including the Centre for Contact Lens Research at the University of Waterloo, University Eye Hospital in Finland, Baylor University College of Medicine (Houston) and Centre for Neurosciences at the University of Miguel Hernendez (Alicante). |
Research 
