Biomedical subjects

A Calossi

Publications and source records attributed to A Calossi.

5 recordsLinked to original sources

PubMed1996

Corneal warpage resolution after refitting an RGP contact lens wearer into hydrophilic high water content material.

PURPOSE: We describe a case of corneal warpage caused by 14 years of rigid gas permeable (RGP) contact lens wear. METHODS: The patient was refit with daily wear high water content soft contact lenses. RESULTS: After 6 months there were significant changes in both refraction and keratometry; computerized videokeratography showed that the corneal contour of both eyes had normalized. CONCLUSIONS: Knowledge of contact lens induced corneal warpage is limited; it is therefore nor possible to follow a standard protocol for managing patients with this corneal deformation. In the case described, it was possible to reestablish a normal cornea without completely suspending contact lens wear by changing from RGP to hydrophilic material.

Adult↗

PubMed1994

Increase of ocular axial length in infantile traumatic cataract.

INTRODUCTION: Emmetropization of the eye may be affected by visual experience. In many kinds of animal species it is possible to alter the refractive state of the eyes by manipulating the visual input during early periods of development. It is however doubtful whether the results obtained in experimental animals will help us explain the genesis of human myopia. MATERIALS AND METHODS: We selected a group of patients who suffered from unilateral visual deprivation in their early life. We examined 13 adult patients who had a unilateral traumatic infantile cataract. Seven of these patients were aphakic. RESULTS: In all of these patients we found a greater axial length in the affected eye as compared to the uninjured eye. The difference ranged from 0.1 to 11.5 mm (mean 2.48) and was statistically significant (p = 0.0015). CONCLUSIONS: Our data support the view that in humans as well as in animals a severe visual deprivation in early life induces an axial elongation of the eyeball and that the refractive errors experimentally induced in animals by visual deprivation have a clinical counterpart in the human population. These data suggest that the model of the system's loss of control on the elongation of the eye may provide valuable information and a precise direction for research on etiology and control of myopia.

Adolescent↗

PubMed1993

A BASIC program to resolve obliquely crossed spherocylinders.

It is often necessary to know the solution of two spherocylinders having oblique axes. Resolving obliquely crossed cylinders involves tedious trigonometric calculation; for this reason we are presenting a simple BASIC program for the rapid and accurate calculation with the help of a personal computer or a programmable calculator.

Eyeglasses↗

PubMedDate not supplied

Computer program to calculate vectorial change of refraction induced by refractive surgery.

BACKGROUND: After refractive surgery, there may be changes in the spherical and the cylindrical components of the ametropia. In astigmatism, there may be variations in both the power and the axis. The best way to describe change in astigmatism caused by surgery is by vectorial analysis, which indicates the changes in power and the axis. However, in clinical practice, this procedure is limited by the tedious calculations required to establish the oblique cylinder combinations. METHODS: We propose a computer program for the calculation, by vectorial analysis, of the refractive changes induced by surgery. The program allows for reference to refractive data or keratometric readings. When the refractive data are considered, it is also possible to obtain the transposition of the correction values from the spectacle plane to that of the cornea. Finally, the program enables the user to calculate the coupling ratio. RESULTS: Some selected surgical cases are discussed by way of example. CONCLUSIONS: We think that this program will be a simple and accurate means of evaluating the results of refractive and corneal surgery.

Algorithms↗

PubMedDate not supplied

Multifocal effect of against-the-rule myopic astigmatism in pseudophakic eyes.

BACKGROUND: In monofocal intraocular lens (IOL) implants we can sometimes obtain a certain degree of pseudoaccommodation. The use of a slight myopic astigmatism is proposed for postoperative refraction to achieve a significant increase in the depth of field and to reestablish a certain degree of pseudoaccommodation in pseudophakic eyes. METHODS: Eighty-one eyes with against-the-rule myopic astigmatism were evaluated in 50 patients who underwent IOL implant surgery. We selected patients with corrected monocular visual acuity greater than or equal to 20/30 and with a refraction ranging from +0.50 to -1.25 diopters sph, from -0.50 to -2.75 D cyl, ax from 55 degrees to 140 degrees. RESULTS: Monocular uncorrected distance visual acuity in 68% of eyes was 20/40 or better, while binocular uncorrected distance visual acuity in 84% of eyes was 20/40 or better and in 66% of eyes was 20/30 or better. Monocular uncorrected near visual acuity in 67% of eyes was J3 or better, while binocular uncorrected near visual acuity in 82% of eyes was J3 or better and in 68% was J2 or better. Sixty-four percent of patients never wear glasses for distance, while 34% use them occasionally and only 2% always wear them. Fifty-four percent of patients never wear glasses for near, 32% use them occasionally, while 14% always wear them. CONCLUSION: These data show that with a low against-the-rule simple myopic astigmatism (about -1.50 D cyl x 90) we can often offer pseudophakic patients a rewarding independence from glasses both for distant and near vision.

Accommodation, Ocular↗