Subsequently all other measurements from that data set were compared to this reference measurement. Theory of edge detection. Dynamic changes in the tear film in dry eyes. The change of precorneal tear film by the application of contact lenses. Cont Lens Anterior Eye Supplement. Prog Retin Eye Res. The intensity of the polar image of subject with smaller pupil b is less uniform than for subject with larger pupil size a. The measurements were carried out in a laboratory where the temperature ranged between

Influence of fetal calf serum, fibroblast growth factors, and hepatocyte growth factor on three-dimensional cultures of human keratocytes in collagen gel matrix. A set of images captured during contact lens wear is shown in figure 1. Controlled study of the use of autologous serum in dry eye patients. All subjects gave informed consent and the study was approved by the university research ethics committee. Chiron Vision Fibronectin Study Group. Autologous serum application in the treatment of neurotrophic lzgrimal.

The number of rings is then counted for each lagriimal of the matrix I p that corresponds to a semi-meridian in the original HSV image to find out the discontinuities in the ring pattern. Lysozyme and lipid deposition on silicone hydrogel contact lens materials.

precorneal film

We can speculate on the potential mechanisms leading to changes in the tear surface quality that we measured with the high-speed videokeratoscopy technique. Furthermore, all lsgrimal methods suffer from a decrease in accuracy due to natural micro-movements of eye position.

For all statistical tests a p -value of less than 0. All patients completed the follow-up to obtain samples of tears, and three months to evaluate clinical results. Subjects had measurements taken at three different times each day; in the morning between amat lunchtime pm and in the afternoon pm. Double lateral shearing interferometer for the quantitative measurement of tear film topography. Eleven subjects six male and five female aged 20 to 31 years mean age 23 years were recruited for the study.

A typical example of estimating tear film surface quality is shown in figure 4 in which one can clearly see the blink, the tear film build-up phase up to 1 st second20 and the phase in which the tear film is relatively stable. Neurobiology of ocular pain. After estimating the average intensity radial profile and fitting a parametric function to it Figure 3centrewe are able to subtract the average background intensity and perform edge detection on a residual radial image Figure 3top-right which results in a noisier but fiom more complete edges Figure 3bottom-right.


Tear Film Surface Quality with Soft Contact Lenses Using Dynamic Videokeratoscopy

Laggimal original radial image Figure 3precornwal has a significantly uneven intensity distribution, which causes the edge detection routine to miss significant portion of the rings in the iris area Figure 3bottom-left. We found in this study that the high speed videokeratoscope technique can be used to discriminate the effects of soft contact lens wear on the surface quality of the tears compared to the bare eye condition, in subjects selected to have good tear quality.

Conclusions The measurement of TSQ using dynamic videokeratoscopy differentiates between bare eye and lens wearing conditions. However, when the pupil is smaller than the analysis area Figure 2bthe resulting radial image shows significant variations in the intensity that cannot be simply removed with standard histogram equalisation techniques.

A more likely explanation for the changes in tear surface quality would seem to be the variation of surface smoothness of the tears and, therefore, the lipid layer. The measurements were carried out in a laboratory where the temperature ranged between Several research groups have reported their work on non-invasive tear film characterization using time-based videokeratoscopy measurements.

Tear Film Surface Quality with Soft Contact Lenses Using Dynamic Videokeratoscopy

The effect of local background subtraction on the performance gilm edge detection algorithm for radial profile images that contain significant part of lighter iris. This was done on two baseline days bare eye and on the first and seventh days of lens wear for a conventional hydrogel lens and following a week of no lens wear, for a further week of silicone hydrogel lens wear.


Various studies have shown that contact lens wear destabilizes the tear film. J Cataract Refract Surg. Subjects used a range of common multipurpose solutions to care for the lenses. Shawand Benjamin Straker.

Associated Data Supplementary Materials Video file. Afterwards, the foot lagriaml is pressed, oscillating block runs parallel to the horizontal cornea plane, separating the epithelial flap, after the PMMA block runs on reverse movement, when it reaches final position the suction is released and the device is removed from the eye. Methods adopting interferometry, 67 Shack-Hartmann wavefront sensing, curvature sensing, 12 and methods based on direct video recording, 13 have also been used to estimate the tear film quality.

Dynamic rilm was taken three times per day; in the morning, at lunchtime, and in the afternoon. Concentrations of IL- 8 were the only interleukin detected in all samples of both surgical procedures, before and after the surgery. Pearson’s correlation coefficient for TSQ Norm and a range of other tear tests. A new method for tear film stability analysis using videokeratography.

The preassembled microkeratome is applied to the operative eye, its central circular opening around the limbus.

Plenum Press; New York: Because the tear film surface instability results in blurring and discontinuities in the ring patterns, we use the variance of the above ring number estimator.

Tear film surface quality TSQ was assessed during the interblink period using dynamic videokeratoscopy at 25 Hz. Such normalization allows the study of tear film behaviour in its build-up phase.

In some cases, the filtering procedure outlined above eliminated a number of the measurements from a particular measurement session.