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biomedical engineering

Eye operation with the topograph

Small company develops equipment to help with ophthalmological surgery

After nine years in the market developing equipment for use in ophthalmology, the Eyetec company, of São Carlos, is getting ready to launch an intra-surgical topograph. The innovation is that it will guarantee greater accuracy and eliminate most of the risks inherent in cataract operations and cornea transplants. The equipment measures the curvature of this membrane of the eye during the operations and detects very small variations, helping the surgeon’s task and avoiding post-operative problems. FAPESP financed the new medical tool under a project begun three years ago within Small Business Innovation Research (PIPE).

Conventional topographs have already been available in the market for almost 20 years. “A good topograph is essential right from the planning stage of surgery”, says the ophthalmologist Gustavo Paro, a consultant of Eyetec’s. The equipment is useful in avoiding astigmatism (distortions in capturing images), a problem deriving from tiny alterations to the surface of the cornea when suturing the surgical incision. “In examining the eye of a patient suffering from a cataract (opacity of the eye’s crystal), for example, we examine the curvature of the cornea and, if necessary, we already define correction of the astigmatism”, he adds.

“Surgery has become more accurate in the last ten years”, explains Paro. Such as, for example, eliminating the cataract by a process called phacoemulsification, a technique reducing the incision from 12 millimeters to 3 millimeters at most. The search for accuracy is stimulated by the race to produce high performance technical equipment.

Academic partnership
For the advances that Eyetec had to make on the conventional topograph, the interaction between the company and the Ophthalmic Optical Laboratory of the Physics Institute (IF) of the University of São Paulo (USP), at São Carlos, and with the Ophthalmology departments of USP’s Medical School at Ribeirão Preto, and the Federal University of São Paulo (Unifesp) was essential. As Luís Alberto Vieira de Carvalho, a researcher at the IF of São Carlos and one of Eyetec’s partners tells, in these conversations it was observed that the way of monitoring alterations to the eyewas indirect and always tardy in relation to the medical care required. “For this reason, before applying for funding from FAPESP, we had built a very basic prototype when we were still students”, emphasizes the electronics engineer Sílvio Tonissi Júnior, also a partner in the company and the project coordinator.

In seeking technological solutions to the problem, Eyetec’s group of researchers sought inspiration in the story of the human eye monitoring devices. As Carvalho explains: “In 1820, the French ophthalmologist Ferdinand Cuignet proposed the first method of studying the images reflected by the frontal surface of the cornea, calling the new technique keratoscopy, and the concept is still valid today”, reports the researcher. “A light was projected on a plate placed in front of the patient’s eye, on which studies and comparisons were carried out and conclusions were drawn. But there were various problems with this system. The alignment process depended a great deal on the observer’s skill and there was no optical magnifying system, making it difficult to analyze the reflected images”.

It was thanks to a stroke of genius by the Portuguese researcher Antônio Plácido, in 1880, that the researchers managed to overcome the limitations of the period. He prepared some sort of cardboard on which he had painted a succession of black circles, with a hole in the center. Based on an analysis of the pattern reflected by the patient’s eye, the professional could deduce the shape of the surface and hence capture the degree of existing anomaly. This technique became known as the “Placido disks”, due to their shape”. “The intra-surgical topograph refines this technique to its utmost degree, and is applied in surgery that may lead to the highest degree of post-operative astigmatism, because of the absence of efficient methods for detecting irregularities on the surface of the cornea”, says Carvalho.

Visual tests
In the first stage of the project, mechanical and optical parts were produced, while at the same time software for capturing and processing the images was developed. The measurements of volunteer patients’ corneas were stored. The next step was to develop a prototype that, in practice, would give the same characteristics as a commercially operational product. New tests were carried out, in “various real surgical situations”, according to Carvalho. In addition, the system’s software was further developed, intending to strengthen the degree of reliability of the system.

The apparatus was improved so that its use would not conflict with the specific needs of the surgery, such as the angle of the incidence of light on the patient’s eyes and its manipulation capability. To achieve this, the topograph was fitted with a sort of mechanical arm, easily handled by the doctor. “The patient is placed in a position where the optical axis of the microscope is established on the same axis as the patient’s eye. The virtual image created by the reflections of the rings of the projector are formed in two places; in the eye and in the camera coupled to the microscope’s ray divider”, points out Tonissi Júnior. The degree of correction of the ocular problems is shown on a computer screen.

Bands of color indicating the situation of the cornea appear on the screen. Hot colors, like orange, red, and yellow, indicate high curvature or localized distortions. Blue and violet represent less curvature and indicate regions with fewer distortions. The averages are green and represent normality. “All this is seen in a way that can be easily interpreted by the doctor”, says Luís Alberto Carvalho.

Promising market
One of the most urgent tasks facing the Eyetec team is to lower the cost of the product. “Today, it would cost around R$ 30,000”, says Carvalho. The camera is Japanese, the optical system is Brazilian, the image acquiring plate is Canadian, and Eyetec is responsible for developing the routine for controlling the software. “The new tests show that is possible to cheapen the intra-surgical topograph substantially”, says Tonissi. The price should fall to around US$ 10,000 by the end of the year, at its market launching. Eyetec has plans to produce two systems for the topograph, one managed by a stationary computer and another to be connected to a notebook.

The market for the new product, in spite of the price, is quite promising, says Tonissi. In the competition on price, ophthalmologists have a good idea of what imported conventional models cost, namely from US$ 14,000 to US$ 18,000, without import duties. The new Brazilian model from Eyetec, coupled to a PC, should, therefore, be 60% cheaper. According to the company’s calculations, today, there are around 9,000 ophthalmologists of whom 3,600 are surgeons, the product’s specific market. As well as the domestic market, the company is already looking at foreign export market.

The Project
Development of an Intra-surgical Topograph (nº 97/13359-2); Type Small Company Technological Innovation Program (PIPE); Coordinator Sílvio Antônio Tonissi Júnior – Eyetec; Investment R$ 195,720 and US$ 42,688