Optometry is a branch of science whose roots are in optics development as well as in physiology development. Among Polish scholars, whose names are firmly engraved in the history of optometry, two names should be mentioned first, they are Witelo (1237 - 1290) and Majer (1808 - 1899). Contemporary optometry began around the turn of the 19th and 20th century in the United States of America where some states erected legal regulations for those opticians who were performing refractions. Since 1993 optometry has been defined by the World Council of Optometry as a health care profession which is autonomous, educated and regulated (licensed/registered). Nevertheless, the question arises: Is optometry a separate part of science or is it only a set of practical procedures useful in vision care? In other words: does optometry have a system of definitions, laws and hypothesis with such logical interrelations that all less general statements may be derived from the most general? Even at this moment the system is not fully developed, yet we can say that optometry is a set of statements important and enough proved to be taught at the university level, being a category by itself and being sufficiently rich to be a subject for teaching as separate discipline.
There are a number of good examples of how optometry has made a unique contribution to science. Contributions which have since been accepted by all of science. I will spend a great deal of time on Friday, describing the contributions of Dr AM. Skeffington. I will not dwell further on him other than to say that I tmst you will be here to see how the thoughtsof Dr Skeffington, 50 years ago, have, in light of new technology, been shown to be correct. Let us however digress and speak of the contributions of Glen Fry and Henry Hofsteuer. These two men are given credit for developing a method of mathematically describing the interaction of convergence and accommodation, first described by Maddox at the turn of this century. They were able to reduce the measurements of accommodation and convergence into a graphical representation and from there to develop mathematical models to describe the interaction of these two different aspects of vision. From this graphical analysis the understanding of the Accommodative Convergence to Accommodation relationship was described. This concept is used, I think, by all persons directly or indirectly who measure vision today. One should not also forget the work of Schor and Ciuffreda, clearly delineated in their landmark text book, VERGENCE EYE MOVEMENTS. These two men, while working at the college of optometry at the University of California in Berkeley have done much work in describing, further developing and then experimentally verifying interactions of convergence and accommodation in terms of mathematical models. These models predict more accurately the interactions of the different aspects of both convergence and accommodation. Can one forget the recently published work by Hung and Smith on the development of refractive errors in the young? Models which were developed years ago, by Harmon and Skeffington among others, which predicted that when an individual was placed in a stressful situation, the person would adapt to grow along the lines of stress to reduce that stress. Now, years after these optometric leaders proposed this model, Hung, Smith and others working at the University of Houston College of Optometry have published in the prestigious journal ,,Nature" the results of their treatment of young primates with spectacle lenses to change the actual growth ofthe eye. Or, can one forget the work of Drs. Held, Gwiazda, Cruz and Thorn at the New England College of Optometry where they have been systematically following the visual and refractive status of infants into adulthood. Dr Held told me in Atlanta last October, that they now have the children of the first subjects in their study. Their results are verifying to a great extent, the visual development profiles first projected by Gesell, Getman, Streff and Apell. I could continue for hours and will on Friday, describe partially the model of A.M. Skeffington, who proposed his dynamic model of the interaction of the body with the eyes and brain in the 1930's, yet, in light of improved technology, this model has been shown to be essentially true. I believe that a unique theory and theories of optometry does exist. Optometry is unique in that it is a neighbor to, but not part of psychology, medicine, education, etc. It is a different discipline, one not confined to the concept that something must be diseased, but rather that a normal visual system can be modified and improved to function more effectively. As a gymnast can benefit from better equipment, so can the visual system, depending upon the task it is asked to do, improve its behavior through specially designed lenses and prisms. Just as an Olympic gymnast requires a coach (why should they require a coach, they are already the best their nation has to offer-they are well past normal) then the visual system can be improved with proper coaching, an optometric discipline known as visual training. Not only, to make vision normal but to also stretch the envelope of human potential. The use of lenses and prisms for the task facing the individual and the coaching of the visual system to strive for perfection of performance is a much different model from other disciplines which generally considers restoring some one to a position of normalcy. Optometry's unique model is that we do not work with the ill, per se, but with the healthy; to make the healthy, all they can be.
Life of Dr. A. M. Skeffington, his model of vision, and his contributions to optometry are reviewed. In particular, vision as s spatial information processing system and dual sensing ocular system are discussed to answer the questions: `where is the object in space?' and `what is the object in space?'.
Human visual system is considered an imperfect communication channel, and there is investigated its ability to recognize quickly and correctly the various charts which are presented suddenly and randomly to an observer. Such ability is represented by the so-called informational efficiency of human vision. The fundamental equation of that quantity in the probability and binary form is derived, and also a suitable incoherent projection method for its measurement is described. Also some averaged and smoothed results of measurement of the informational efficiency in dependence on the time of chart presentation are shown for two sets of different 2D charts. Moreover, the method and the obtained results are evaluated.
This paper presents an overview of our understanding of the optics of the lens and the changes to lenticular function with age. It deals specifically with (1) presbyopia, describing the latest theory which suggests that presbyopia is a product of age-related change and continued growth, and (2) the lens paradox, a hypothesis for resolving it and the experimental findings in support of the latter.
The paper presents the results of subjective studies of the influence of the transverse observer displacement with respect to a visual instrument based on the experiment with ten examined persons. The diameter of the exit pupil of the instrument was chosen to be 2.4 mm, white and sodium illuminations were chosen of nearly 10 nt.
In many research and technical situations it is important or at least interesting to know the visual spatial resolution (acuity) of variable-color line patterns. Here the line patterns with sinusoidal distribution of intensity or brightness are taken into consideration, and the emphasis is placed on the microscopic visual acuity. The patterns of variable spatial frequency were produced by using a double- refracting interference system, prismatic glass plates, and monochromatic light of variable wavelength.
The correct placing of the lenses plays an important role in the ophthalmological practice. Centering errors cause disadvantageous prismatic effects and worsen image quality. The optical axes of the spectacles should pass by rotation centers of the eyes. An often met error consists in a faulty center distance, in a wrong positioning of the lenses axis or their placing too high, too low, or in the inclining without lowering. The errors reach some millimeters and some degrees of arc. In technical optics acceptable errors are fractions or hundredths of millimeters and minutes or seconds of arc. Therefore only first powers of decentration are taken into account. In the spectacle optics one cannot omit the second powers of decentration vector. An astigmatism proportional to the square of decentration arises in the center of the field. The off axis aberrations are a quadratic function of the decentration with linear term. The aberrations are calculated by admitting a virtual diaphragm in the point of intersection of the lens axis with the eye's view axis. This method can be applied also to the lenses with aspheric surface and to astigmatic lenses, if the decentration vector lies in one of the principal sections of toroidal surface.
Some forms of the equation of the toric surfaces are presented. The equation in the sagitta form facilitates the choice of the correct solution for the incidence point of the light rays. There are given also the formulae for the radii of curvature and the components of the normal to the surface. Aberrations of toric spectacle lens are shown.
The subject of modern, save and stylish eyewear is entertaining not only to people with unwell eyesight. Many people use glasses with anti-UV or blue-block coatings, glasses for driving or working with a computer. There were investigated the blue-block eyewear. There were analyzed reflected radiation at 300 - 400 nm wavelengths with cross- incidence. The traditional eyewear with classical or stylish frame may not protect sight against the UV radiation.
In numerous optical systems from spectacles to optical instrumentation, one of the essential components is the reflection reducing coatings on the lens. If appropriate thin films coating is deposited on spectacle lenses, reflection can be effectively reduced with corresponding improvement of acuity of vision. Multilayer coating system has to be employed in order to obtain really convincing effect on ophthalmic lenses.
In the past, UV-blue-absorbing intraocular lenses (IOLs) were developed and then have been implanted to more than 200,000 patients. Recently, new UV absorbing IOLs, named `IOL-Photochrom' were invented. The latter have photochromic properties, mainly in the blue part of visible spectrum. Under low illumination their spectral transmission is similar to that of natural human lens of young individuals. On the other hand, in bright light of sunny days the transmission is the same as that of the natural lens of oldmen.
Background: Accommodative facility testing is a common test performed by optometrist to investigate an individuals skill at focusing objects at near and at far. The traditional test however harbors possible confounding variables including individual variance in reaction time, visual acuity, verbal skills and oculomotor function. We have designed a test procedure to control these variables. Methods: Children were evaluated with a traditional accommodative facility test, a test which evaluated reaction time and language skill but without accommodative (plano lenses) and a test which evaluated reaction time, language skill and accommodative facility (+/- 2.00 D lenses). Results: Speed of reaction time was 2.9 sec/cycle for the plano lenses (for dominant eye). Speed of reaction with +/- 2.00 D lenses was 6.6 sec/cycle for dominant eye and the monocular speed of accommodations was calculated to average 3.7 sec/cycle. Normative data reported in the literature was calculated to be 5.5 sec/cycle. Discussion: We found that both our method which controls for confounding variables the traditional method reveal similar findings but that individual subjects would pass one method and fail the other. This is attributed to variation in the reaction time and digit naming skill. Conclusions: Although both methods reap similar results, both methods should be employed to discover, in those who score below the expected finding, to tease out whether or not the fault falls within the reaction time/language area or whether it is a true accommodative facility dysfunction.
The optical system of eye is composed of cornea, lens, anterior chamber, and vitreous body. In the standard schematic eye there are 6 refracting surfaces. The changes of the curvature radii, of the distances between them, of the refractive indices influence the ametropia, refractive power of the eye and retinal image size. The influence of these changes can be appreciated by ray tracing or by an analytical method. There are presented simplified formulae for the differentials of ametropia and refractive power of the eye with respect to the surfaces curvatures, refracting power of cornea and lens, refractive indices. The relations are valid too for bigger changes if ametropia is measured in the cornea vertex. The formulae for the differentials with respect to distances, lens translation, eye axis length are valid if ametropia is measured in the object focus of the eye.
The numerical model of refractive properties of the eye lens is given. Crystalline lens is presented in a form of hundreds ellipsoidal shells with rotational symmetry, having the constant refractive index inside every shell. The refractive index between the surfaces increases from the cortical shell to the inner one, according to the exponential dependency. To complete the model of the optical system of the eye, the cornea approximated by two ellipsoidal surfaces is added in front of the crystalline lens. Ray tracing procedure is applied to study the refraction of rays through such a system. By changing the refractive index profile, optical properties of given model are analyzed. Results of calculations are compared with experimental data.
The first part of the paper presents the analytical curves used to approximate the corneal profile. Next, some definition of 3D surfaces curvature, like main normal sections, main radii of curvature and their orientations are given. The examples of four nonrotational 3D surfaces such as: ellipsoidal, surface based on hyperbolic cosine function, sphero-cylindrical and toroidal, approximating the corneal topography are proposed. The 3D surface and the contour plots of main radii of curvature and their orientation for four nonrotational approximation of the cornea are shown. Results of calculations are discussed from the point of view of videokeratometric images.
Phase shifting imaging polarimetry was applied to measure birefringence of the human cornea in vitro and in vivo. Using computerized polarimeter, two maps representing distribution of the azimuth angle and the retardation are calculated and presented. Investigation of the corneal birefringence could be useful for examining the inner corneal structure and in diagnosis of some corneal pathologies.
The purpose of this study was to quantify noninvasively, with the use of laser-flare meter the alterations of the blood-aqueous barrier following penetrating keratoplasty. This could diagnose objectively disruption of this barrier in eyes with early allograft rejection, possible even before manifestation of the clinical signs and would help to monitor the efficacy of the treatment. We used the laser flare-meter (Kowa FM-500) to investigate alteration of the blood-aqueous barrier following uncomplicated penetrating keratoplasty (PK) and in corneal allograft rejection. Examination was performed in 50 eyes of 48 patients after uncomplicated PK (7 days to 12 months after PK), in 20 normal control eyes and in 8 patients with acute allograft rejection. Flare values after uncomplicated keratoplasty slowly decreased in time reaching nearly control values 6 - 12 months postoperatively. They were considerably higher for acute allograft rejection compared to eyes following uncomplicated PK and normal control group. Actually, they tended to diminish gradually after systemic and topical administration of steroids and/or immunosuppressants. Application of laser tyndalometry has been proven to be highly useful in the follow up of patients after perforating keratoplasty-especially high risk grafts, it helps to detect objectively early allograft rejection and is beneficial in monitoring the effectiveness of the treatment.
Analysis of the optic nerve head topography and static perimetry, are important in glaucoma diagnostics. Topography of the optic nerve head by Topographic Scanning Systems, carries a lot of planimetric and volumetric values. In this paper, results of optic nerve head topography and static perimetry of 116 primary open angle glaucoma cases, are discussed. Estimating correlation between topographic and perimetric data, the most valuable parameter of the topographic method is carried out. Its values in different stages of glaucoma are given.
Scanning laser polarimetry is the method of evaluating the thickness of the retinal nerve fiber layer. Different pathologies damage retinal fibers, but in glaucoma the damage is present very often before other symptoms reveal. As the earliest possible diagnosis of glaucoma is essential for treatment results, scanning laser polarimetry offers a very useful diagnostic tool for ophthalmology. This paper describes the principles of the method and discusses the results obtained in 50 glaucomatous eyes in conjunction with 2- and 3-D topographical parameters of the optic disc.
The shearing interferometry is presented as an in vivo method for testing the stability of the tear film covering the contact lens. The material and quality of a contact lens and its correct fitting to the surface of cornea influence the stability of the tear film. By observation of the tear film distribution, the precise assessment of the quality of the contact lens surface can be performed. Moreover, the overused or damaged contact lens can be detected by the analysis of interferograms. In this study the following types of soft contact lenses were used: Dura Soft D3 (r equals 8,7 mm, r equals 8,4 mm), Medalist (r equals 8,7 mm) and Johnson and Johnson (r equals 8,8 mm). The contact lenses were placed on the patients' cornea. The 3 mW HeNe laser was used as the light source in shearing interferometer and the CCD camera for recording the interference images. The coherent light reflected from the surface of the contact lens covered with the tear film formed the interference pattern. The sequence of the obtained interferograms were recorded and then analyzed. The accuracy of the contact lens fitting can be estimated by the interferogram analysis. The examples of correct and incorrect fitting of the overused or damaged contact lenses are presented. The proposed method is noncontact, nondestructive and of the high accuracy.
The paper presents a modified method of the Shearing interferogram analysis by the use of the Fast Fourier Transform. The interference fringes are obtained in Shearing interferometer and are related to a wavefront reflected from the tear film over the cornea. The method is based on the measurement of interference fringes disturbances by calculation of the 2nd momentum of Fourier spectra of the interferogram. The less smooth tear film covering the cornea the more disturbed interference fringes and higher value of the 2nd momentum calculated from its Fourier spectra. The interferograms obtained from the proposed setup can differ also in the shape of fringes and in its density. This is caused by the differences in distance between the interferometer objective and the eye. Since the living eye is a continuously moving object, the fixation of this distance is difficult to achieve in practice. Obviously the fringes variations affect the Fourier spectra distribution and results of the numerical analysis based on FFT. The proposed method compensates the variations by applying the correcting factor determined from spectra distance from the origin of Fourier domain.
The homogenate of the nuclear part of the bovine lens was investigated. The angular dependence of the light scattered intensities was measured as a function of temperature. The random density fluctuation theory and the Debye theory for a spherical scatterer were adopted to evaluate size of scattering units. The analysis of the experimental data demonstrates the presence of four kinds of scattering units: aggregates, separation between aggregates, scatterers responsible to the phase separation and large elements. The temperature dependence of the light scattered intensity was used to estimation of the spinodal temperature for the sample.
The purpose of this study was to quantify noninvasively, with the use of laser-flare meter, the alterations of the blood-aqueous barrier following phacoemulsification, extracapsular cataract extraction (ECCE), trabeculectomy and phacotrabeculectomy. Aqueous flare measurements were performed using laser-flare meter (Kowa FM-500). The device allows noninvasive, quantitative determination of aqueous protein concentration by recording the scatter of a helium- neon laser light scanned into the anterior chamber. Anterior chamber flare expressed as photon counts per millisecond was also estimated preoperatively, one and three days postoperatively, in two groups of cataractous eyes: 75 eyes after `divide and conquer' phacoemulsification with continuous curvilinear capsulorhexis, 43 eyes after extracapsular cataract extraction with `can opener' capsulotomy. Moreover, two groups of eyes following trabeculectomy (12 eyes) and phacotrabeculectomy (12 eyes) were also examined one, three and seven days postoperatively. We observed significantly lower anterior chamber flare measurements following phacoemulsification (32.0 - 1 day, 16.4 - 3 days postop) than after ECCE (64.6 and 40.2, respectively; P < 0.001 vs phaco group). Relatively high values were obtained after phacotrabeculectomy (58.0 one day, 39.3 - three days and 24.4 - 7 days postop). Intermediate values were noted after trabeculectomy alone (46.3, 25.6 and 23.9, respectively). Phacoemulsification with curvilinear capsulorhexis induced less severe blood-aqueous breakdown than ECCE with `can opener' capsulotomy. Eventually, it can be suggested that phacoemulsification, as a less traumatizing technique might be preferable in high risk eyes (with diabetes, glaucoma, uveitis) that are more susceptible to postoperative inflammation and consecutive complications.
The radial distribution of Gaussian beams radiation intensity on the focal plain of the ocular optical system has been calculated using the human eye Modulation Transfer Function. The dependencies of the distribution on the distance to the beam's constriction have been analyzed for the visible spectral range at a given eye accommodation. More consideration has been given to the conditions of the most `sharp' focusing of laser beams onto the retina (the most dangerous cases) and to the typical errors arising in the process retinal irradiance distribution measurement through the pupil. The analogous model has been created for the eyes of some animals. The results of calculations are in a good agreement with direct measurements data at the back pole of enucleated rabbit eyes.
Purpose: The aim of this study was to observe human corneas after Photorefractive keratectomy, in vivo, using the Scanning Slit Confocal Microscope `Confoscan P4' (Tomey). Material and method: The material consists of 80 corneas of 45 patients where in vivo, non-invasive evaluation of the corneal structures was performed with a confocal microscope. The confocal microscopic examination was performed in cases after excimer laser refractive surgery and analyzed together with the type of the procedure (myopia, hyperopia and astigmatism correction), and with the patients' age and sex. The results obtained in the right and left eye of each patient after bilateral procedures were compared. The state of the cornea was analyzed in relation to follow-up time. Results: The observations consist of the structure of corneal epithelium, stromal keratocytes, topography of nerve fibers, appearance of Bowman's and Descemet's membranes and condition of endothelial cells. Conclusion: The confocal microscope allows non-invasive in vivo observations of the corneal structures and is capable of the evaluation of corneal healing after excimer laser refractive procedures.
Purpose: The aim of this study was to investigate the saveness of the PRK procedures. Material and method: 151 eyes after PRK for correction of myopia and 112 after PRK for correction of myopic astigmatism were examined. All PRK procedures have been performed with an excimer laser manufactured by Aesculap Meditec. Results: Haze, regression, decentration infection and overcorrection were found. Conclusions: The most often complication is regression. Corneal inflammation in the early postoperative period may cause the regression or haze. The greater corrected refractive error the greater haze degree. Haze decreases with time.