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Biofeedback therapy has been shown to be of value in the treatment of numerous psychological and physiological problems. In this paper, applications of biofeedback for correction of oculomotor abnormalities including strabismus, nystagmus and amblyopia, refractive error correction, reduction of intraocular pressure (IOP), and blepharospasm suppression are reviewed.

Checking our radial keratotomy database, we have been able to conclude that contact lens wear after RK is exceptional (0.6%), possible, easy. It further appears clearly that centripetal way of cutting is by far to be preferred above downhill-centrifugal cutting.

Recent clinical and experimental evidence suggests that a better physiological response to hydrogel lens wear can be obtained with fenestrations. To determine whether those observations could be attributed to increased corneal oxygenation, the equivalent oxygen percentage (EOP) was measured at the cornea of eight subjects wearing hydrogel contact lenses which had multiple fenestrations of 0.8 and 1.8 mm. It was possible to increase the mean EOP by 1.7 +/- 1.3% O2 (p less than 0.002) beneath a standard thickness lens using four 1.8-mm fenestrations. However, such lenses were uncomfortable to wear. Fenestrations that provided comfortable wear (0.8-mm diameter) did not significantly increase the EOP beneath standard thickness lenses (-0.1 +/- 1.0% O2, p greater than 0.1 for four fenestrations, and +0.2 +/- 1.2% O2, p greater than 0.1 for eight fenestrations) or ultrathin lenses (-0.1 +/- 1.3% O2 p greater than 0.1 for four fenestrations). It is concluded that fenestrations do not provide a clinically efficient means of increasing the oxygen tension beneath hydrogel contact lenses.

The indications and the adaptation method of a combined contactoptical system called piggy-back system, are dealt with. This system comprises the adaptation of a soft contact lens on which is applied afterwards, a hard one. The optical and the therapeutic results obtained in 7 groups of patients (56 eyes) with astigmatism, aphakia, keratokonus, keratoplasty, injuries, chronic lesions of the epithelium, and hyposecretion of the tear fluid, are discussed together with the results of the adaptation of the lenses.

The response of a second-order feedback system is used to describe the controlling process that regulates the refraction of the human eye to achieve optimal visual acuity over the years (emmetropization). From data collected in past refractions, the equation of the feedback system has been derived for individual eyes and used to predict changes in their refraction with age with an accuracy of 0.50 diopters for 89.1% of the eyes tested. If the model is applied to other populations, the root mean square error of prediction will be between 0.20 and 0.36 diopters with a 95% degree of confidence. The model indicates that corrective lenses applied to the eyes, especially in the early years of life, will cheat the servo system and defeat the emmetropization process.

A female patient, age 4, presented with the chief complaint of severe headaches. Onset was within the past year. A neurological evaluation was conducted with negative results. Our testing revealed a moderate hyperopic refractive error, a marked lag of accommodation, and reduced stereopsis. The refractive error was corrected and a 6 week follow-up evaluation was performed. Correction of the refractive error resulted in abatement of the headache complaint, improved visual function, and improved preschool performance.

Little has been published to date on orthokeratology which can explain what changes the eye actually goes through. Many professionals are waiting for this evidence before judging this controversial technique. With orthokeratology the corneal curves are changed and present a definite pattern. There are a number of changes which must occur when the cornea is flattened which reduce the power of the eye beyond that amount of flattening. This paper examines one of these unknowns.

Although optometrists can be expected to be responsible for the base curve, which determines the form of the lens they prescribe, they seldom specify the base curve to the optical laboratory. They may ask for a corrected-curve lens without specifying the kind of corrected-curve lens. If optometrists were to specify what they want in terms of a convex spherical base curve and allow the laboratory a leeway of p1.00 D, the laboratory could probably fill the order with an uncut lens from stock. With a series of semifinished lenses with convex spherical base curves spaced 2.00 D apart, the laboratory can supply a finished lens that will meet almost any need. For glasses to be used for distant objects, first consideration is usually given to minimizing the unwanted sphere and cylinder in the periphery of the lenses. For those who want to aim at this objective, I have worked out a series of convex spherical base curves that can be used for various combinations of spheres and cylinders.

To describe the role of an ophthalmic optician in the eye protection activities of occupational health care this paper concerns the basic training of the opticians in Finland, the optoergonomics courses, the importance of eye protection activities, and the role of an optician in the protection of eyes and vision at work. It is concluded that it is important to correct the refraction of the employees, because the workers with poor vision have more industrial accidents than those with normal vision. A programme created to increase the use of eye protectors indicates the role of the optician in eye protection activities.

This paper describes clinical observations of optico-sensori-motor symptomatology prior to and during treatment for strabismus. These findings were compared with theoretical data of the binocular visual function. We consider that binocular function has the structure and the working of a "set" in cybernetic sense. In this psycho-physiological set, the accommodative system constitutes a "sub-set". The classification of accommodative disturbances as "pure or impure" and "typical or atypical" arises from the fact that a rebuilding of the visual function has occurred. Thus in "pure" accommodative strabismus the disturbances of accommodation results from "peripheral" accommodation and is easily reversible. In this situation ocular deviation has been perfectly corrected for and binocular vision normally built up since there is enough compensation of the whole optical correction. In "impure" accommodative strabismus the perturbation of accommodation affects the whole accommodation system and also the sensorial motor system. Thus there is a restructuring of the optico-sensori-motor set that is more or less reversible due to a variety of factors. From these investigations we conclude: every strabismus is accommodative in the sens that in every strabismus there is a disturbance of accommodative mechanism. Furthermore, we oppose believers of "all sensorial" and "all motor" mechanisms. Considering that strabismus is a disturbance of optico-sensori-motor binocularity, nothing can be only "accommodative", only "sensorial" and only "motor". From this it follows that treatment should not be only "motor", only "accommodative" or only "sensorial".

Optical defects of the light-focusing apparatus of the eye are called errors of refraction. They are responsible for 13% of all significant vision loss in Kenya, ranking third of all causes, after cataract and trachoma. As the overall prevalence of such visual impairment in the Country is 3.7%, roughly 0.5% of the population can be said to need spectacles to obtain normal vision. The comparable figure for secondary school children in Nigeria has been found to be 2.4%. In addition, patients require special spectacles after cataract surgery to obtain adequate vision; without such spectacles these patients are still 'blind' by World Health Organization criteria. These glasses can be obtained through mission societies and various charitable organizations for a little as $5 per pair, and can be manufactured locally with available ophthalmic manpower and technology. Alternatives to spectacles such as contact lenses, intra-ocular lenses and Kerato-refractive surgery are not suitable for use in developing Countries.

A mechanism called emmetropization appears to control the ocular focus over the years. Emmetropization could regulate the refractive media (dimensions of cornea, lens, and axial length), detecting the focus or refractive error of the eye at rest and initiating changes to reduce the refractive error; this concept suggests that a feedback loop is operational. A feedback mechanism for ocular refraction implies that correcting ametropia with lenses initiates a change in the refractive state of the eye. The long-term effect of corrective lenses on ocular refraction is investigated with a mathematical feedback model that can predict the extent and direction of this change. The results indicate that lenses worsen existing ametropia conditions. However, the use of appropriate lenses in early life can reduce and correct developing ametropia.

With the Food and Drug Administration approval of the Hydrocurve soft contact lens, previously unsuccessful soft contact lens candidates may now be able to wear a Hydrocurve lens rather than being limited to the new ultrathin "semiflexible" or hard contact lenses as the only viable alternative. The Hydrocurve has proven to be an excellent lens with a potential to greatly increase the percentage of successful soft lens patients for the practitioner. Due to Hydrocurve's extensive flexibility in terms of base curve and diameter it has shown to be quite useful where other lenses have failed due to a lesser variability in parameters.

Assessment of intraocular lens (IOL) power may rely, when biometric measurements of the eye are not available, on refraction previous to cataract development. Such an assessment, however, is generally considered unreliable. To improve the predictability of this method, we correlated refraction measurements with predictions of IOL power. In contrast to previous studies which used retrospective assessment of precataract refraction, this study included only noncataractous eyes and correlated the direct refractive measurements obtained with hypothetical IOL power values. These values were calculated by placing axial length and corneal power measurements of the same eyes in the SRK formula. We conclude that the regression formula obtained may improve the clinical judgment required for predicting lens implant power in cataractous eyes, on the basis of precataract refractive measurements.

Good vision is important in water sports. Some of the vision demands in swimming and diving are discussed. Prescription and non-prescription visual aids are described.

Eye movement patterns and reading performance were evaluated in 38 4th and 5th grade male students who were at least 1 year behind in their reading levels. Half of the subjects (Group I) demonstrated a need for convex lenses at near by a book retinoscopy criterion. The remaining subjects (Group II) showed no need for convex lenses at near by the same criterion. The subject's eye movements during reading were recorded by a commercial device called Eye-Trac. These recordings were made with 2 lens applications, plano and +0.50 D, respectively. The number of fixations, regressions, rate of reading, and relative efficiency for each condition (plano and +0.50 D) were calculated. In Group I, 3 of 5 measures showed significant improvement with plus lenses. These subjects showed fewer regressions, increased reading speed, and higher relative efficiency with plus than without. In Group II, 3 of 5 measures showed decrement with plus lenses, while 1 (comprehension) showed improvement. These subjects showed more fixations and regressions and lower relative efficiency with plus than without. It is therefore concluded that convex lenses of low power can have considerable immediate effect on children's reading skills, sometimes helpful and sometimes detrimental, and that proper pretesting with both retinoscopy will aid in the prediction of this effect.

Some examples will be noted where the strabismus surgeon plans the patient to have more than one operation. Unfortunately most multistage strabismus procedures are unplanned and are a consequence of failure of the initial surgery. The three most common causes of such failure will be discussed. Brief mention will be made of the more important surgical techniques for rectus muscles that have had repeated operations.

A case of oculocutaneous albinism is described in which bilateral Axenfeld's anomaly co-exists. Progressive elevation of intraocular pressure required treatment and this complication has not been reported. Different hypotheses regarding the co-existence of these conditions are reviewed.

A questionnaire was developed to measure changes in certain behaviors at various intervals after correction of refractive errors in a sample of mentally retarded persons. The sample comprised three age groups: 0 to 6 years, 7 to 17, and 18 and above. In each age group, four subgroups were selected--one experimental (new-glasses) group and three control groups. In the group which received new spectacles, changes were recorded in social behaviors, gross and fine motor skills, and reading and writing skills. These changes were most evident in the youngest age group.

Broca's pupillometer offers a simple and effective means of measuring the diameter of the pupil. However, it is often used without proper attention to the limitations of its optics. Errors of measurement may result from uncorrected refractive error, accommodation, spectacle correction, and spherical aberration (SA). A simple means of minimizing these errors is to hold the pinholes (PH's) of the pupillometer as close to the cornea as is feasible.

Two techniques for fitting long-term polymethyl methylcrylate (PMMA) lens wearers with a gas-permeable hard lens are compared. These are: complete cessation of all lens wear for the period necessary to achieve stability in the patient's refraction and corneal curvature, and immediate refitting with a Polycon lens. Eleven patients who had worn hard contact lenses for at least 3 years and had wearing times of at least 8 hr per day were refitted with each technique. Refitting with Polycon lenses slowed but did not otherwise inhibit the recuperative changes taking place in the cornea after PMMA lens removal; vision was better and more stable with this group.

Ten years ago, Dr. Simone Delthil, who was one of the first, in France, to make researches into aniseikonia, departed from this life. This anniversary offers the opportunity to the authors to recall that it is most desirable, before operating, that theoretical modifications of the size of retinian pictures should be considered, according to the selected compensatory method, especially in the case of anisometropia or unilateral aphakia.

The effect of peripheral refractive error correction on the automated perimetric sensitivity profile was investigated on a sample of 10 clinically normal, experienced observers. Peripheral refractive error was determined at eccentricities of 0 degree, 20 degrees and 40 degrees along the temporal meridian of the right eye using the Canon Autoref R-1, an infra-red automated refractor, under the parametric conditions of the Octopus automated perimeter. Perimetric sensitivity was then undertaken at these eccentricities (stimulus sizes 0 and III) with and without the appropriate peripheral refractive correction using the Octopus 201 automated perimeter. Within the measurement limits of the experimental procedures employed, perimetric sensitivity was not influenced by peripheral refractive correction.

The purpose of this paper is to determine the value of overcorrecting minus lenses in treating children with intermittent exotropia. The aim with this therapy is to secure an increase in the quality of fusion and to induce a quantitative decrease in the angle of strabismus. Thirty-five children were treated with 2.00 to 4.00 diopters of overcorrecting minus lenses for a median of 18 months duration. Of these, 46% had an improved quality of fusion during therapy; 26% had an improved quality of fusion and also had a quantitative decrease in their angle of deviation; and 28% had an inadequate improvement in their quality of fusion and decrease in the angle of their deviation with this therapy. Two children went from intermittent exotropia to esotropia while wearing their minus lenses--both had high accommodative-convergence/accommodation ratios (11.5 delta/1D and 10.7 delta/1D). Seventy percent of good responders who were followed for at least 1 year after discontinuing the therapy maintained a qualitative or quantitative improvement in their intermittent exotropia.

This paper describes the basic features of an ongoing double masked, randomized, controlled clinical trial which studies the changes in corneal and visual function that result when contact lenses are fitted in a manner designed to alter myopic refractive error. Subjects are randomly allocated to either a treatment or control group. Corneal and visual changes resulting from wearing lenses of these designs are compared to the effects of wearing contact lenses fitted in a standard clinical manner. Comparative analysis of the treatment and control groups is based on (1) visual acuity, (2) refractive error, (3) corneal thickness, (4) endothelial cell density, (5) external eye health, (6) corneal curvature, (7) duration of effect, and (8) predictive factors such as ocular rigidity and corneal topography. Essential parts of the experimental design and some results from the first phase of the study are reported.

A contact lens made from silicone rubber has been fitted successfully for extended wear in children. The lens has been used primarily with aphakic children, but it has also been tolerated by children with anisometropia, high myopia, and keratoconus. The lens can be handled like a hard contact lens and can be fitted by a variety of methods. The eye shows excellent tolerance of the lens and complications or failures to wear the lens have been due primarily to discomfort. After about a year of wear the lens surface can no longer be cleaned.