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PubMed2006

Role of the pineal gland in ocular development of the chick in normal and constant light conditions.

PURPOSE: To evaluate the role of the pineal gland in development of the chick eye in normal and constant light (CL) conditions. METHODS: Chicks (Gallus gallus) were raised in either a 12-hour light-dark cycle (12L/12D) or in CL, with or without opaque, removable hoods that covered the top of the head for 12 hours each day. An additional group was raised with opaque eye occluders over the right eye for 12 hours daily. Half of the chicks in each group had their pineal glands surgically removed at 3 to 6 days after hatching. Corneal curvature was measured with keratometry, anterior chamber depth with ultrasound, and refraction with infrared photoretinoscopy. RESULTS: Pinealectomy does not affect the development of the chick eyes either in 12L/12D or CL. Covering the right eyes provided the same amount protection against CL's effects on the corneal curvature of both eyes, with or without pinealectomy. Pinealectomized chicks were not protected from CL's effects by 12L/12D head covers. A similar pattern of responses was obtained for refraction and anterior chamber depth. CONCLUSIONS: Although 12L/12D covering of the pineal gland can protect chick eyes from CL's effects (corneal flattening, shallowing of the anterior chamber, and hyperopia), the pineal gland does not appear to be necessary for normal growth in 12L/12D conditions, and its absence does not affect eye growth in CL conditions, with or without hoods or occluders. Pinealectomy does not influence the protection of an eye exposed to CL that is afforded by covering the other eye in a 12L/12D cycle.

Animals↗
PubMed2006

A population-based assessment of presbyopia in the state of Andhra Pradesh, south India: the Andhra Pradesh Eye Disease Study.

PURPOSE: To determine the prevalence of presbyopia in the state of Andhra Pradesh in south India. METHODS: Comprehensive ocular examinations including logMAR (logarithm of the minimum angle of resolution) distance and near (presenting and best corrected) visual acuity, slit lamp biomicroscopy of the anterior segment, and dilated posterior segment examinations were performed using a standardized protocol for subjects identified through a random cluster-sampling strategy in Andhra Pradesh. Information of difficulty in performing near tasks was collected as part of a visual function questionnaire administered to all subjects. A person was defined as having presbyopia if the person required an addition of at least 1.0 D in either eye for near vision in addition to their best corrected distance correction to improve near vision to at least N8 and if they had graded lens opacities (Lens Opacities Classification System [LOCS III] system). RESULTS: Examined in the study were 5587 subjects 30 years of age or older (mean age 47.5+/-13.0 years). The age-, gender-, and area-adjusted prevalence of presbyopia was 55.3% (95% confidence interval [CI]: 54.0-56.6). One third (n=1173; 30.0%) of the 3907 subjects with presbyopia were currently using spectacles. Of the 2734 subjects with presbyopia and not using spectacles, 528 (19.3%) had moderate to severe difficulty in reading small print, and 2085 (76.3%) had moderate to severe difficulty in recognizing small objects and performing near work, including 1057 (38.6%) subjects who were unable to manage any near work. On multivariate analysis, female sex (OR: 1.4, 95% CI: 1.1-1.8), rural residence (OR: 1.5, 95% CI: 1.2-1.8), alcohol consumption (OR: 0.8, 95% CI: 0.6-0.9), nuclear opacity of the lens greater than grade 2 LOCS III (OR: 4.8, 95% CI: 1.4-16.8), myopia (OR: 1.6, 95% CI: 1.3-2.1), and hyperopia (OR: 3.6, 95% CI: 2.7-5.2) were associated with presbyopia. CONCLUSIONS: The high prevalence of presbyopia and the stated effect on performing activities related to near vision needs to be translated into programs and strategies that specifically target presbyopia.

Activities of Daily Living↗
PubMed2006

Darkness causes myopia in visually experienced tree shrews.

PURPOSE: To examine the effect of a period of continuous darkness on the refractive state and vitreous chamber depth of normal light-reared juvenile tree shrew eyes, and to learn whether eyes that developed myopia in response to monocular minus-lens wear will recover in darkness. METHODS: Starting at 16 days of visual experience (VE), the refractive state of five dark-treatment tree shrews was measured daily to confirm that it was stable and nearly emmetropic. After corneal and ocular component dimension measures, the animals were placed into continuous darkness for 10 days. On removal of the animals from darkness, corneal and ocular component measures were repeated, and daily refractive measures were resumed. The refractive state of the dark-treatment group was compared with that of a normal-lighting group (n = 5) that received standard colony lighting throughout the measurement period. Five dark-recovery animals wore a monocular -5-D lens for 11 days to induce myopia before they were placed into continuous darkness for 10 days. RESULTS: The animals in the normal-lighting group completed the emmetropization process, stabilizing at approximately (mean +/- SEM) 0.7 +/- 0.3 D of hyperopia (noncycloplegic refraction, corrected for the small eye artifact) at 60 days of VE. Dark-treatment group eyes shifted toward myopia (mean +/- SEM, -4.3 +/- 0.5 D) in the dark. The vitreous chamber became elongated by 0.09 +/- 0.02 mm relative to normal eyes. Corneal power showed a small, near-normal decrease (1.4 +/- 0.3 D). Four of five myopic eyes in the dark-recovery group became more myopic (-2.2 +/- 0.9D) in darkness, and all the fellow control eyes shifted toward myopia (-2.8 +/- 0.5 D). CONCLUSIONS: Maintaining emmetropia is an active process. After eyes have achieved emmetropia or have compensated for a minus lens, continued visual guidance is necessary to maintain a match between the axial length and the focal plane or for recovery to occur. Absence of light is myopiagenic in tree shrews that have developed with normal diurnal lighting. This result contrasts with the apparent absence of a darkness effect in tree shrews reared in the dark from before normal eye opening.

Animals↗
PubMedDate not supplied

New findings in the Parry-Romberg syndrome: a case report.

PURPOSE: To describe further findings in the Parry-Romberg syndrome that might contribute towards a better understanding of the disease. DESIGN: Case report. METHODS: The clinical history of a patient with the Parry-Romberg syndrome was studied, and fluorangiography and echography were carried out. RESULTS: Clinical observation revealed classic hemifacial atrophy; fluorescein angiography showed telangiectasis, light staining of the retina, and leakage from the largest telangiectasis and the optic disc vessels; echography showed shrinkage of the eyeball and thinning of the extraocular muscles. CONCLUSIONS: Enophthalmos in this disease is caused not only by progressive fat atrophy but also by shrinkage of the eyeball and thinning of the extraocular muscles; the shrinkage of the eyeball helps explain the presence of choroidal and retinal folding and hyperopia, confirming the primary involvement of connective tissue in this disease.

Child↗
PubMedDate not supplied

Review of experience with retinopathy of prematurity from the Pavia registry (1990-1993).

In this retrospective study we analysed the prevalence of retino-pathy of prematurity (ROP) and its sequelae in a sample of premature infants with birth weight less than 1500 grams. From 1 January 1990 to 31 October 1993, we studied 160 surviving premature infants with very low birth weight (< 1.500 g) referred to the Neonatal Intensive Care Unit of the I.R.C.C.S. Policlinico San Matteo, Pavia, Italy. Thirty percent of these infants suffered from ROP, and 13.7%, with severe ROP, underwent cryotherapy. These latter had very-very low birth weight (< 1.000 g) and low gestational age (< 28 weeks). Follow-up of 69 infants at 12 months for retinal sequelae, refraction defects, bin-ocular vision and ocular motility impairments gave the following results: 1) strabismus 20.3%; 2) > 3D hyperopia 3%; 3) myopia 30.4%; 4) > 5D myopia 3.7%. The incidence of refraction and ocular motility anomalies in patients with acute ROP with spontaneous remission was similar to that of unaffected premature infants. Conversely, in the patients treated with cryotherapy the incidence of strabismus and > 5D myopia was greater than for untreated infants: 30% vs 15.4% (n.s.) and 14.7% vs 0% (p = 0.05), respectively. Cryotherapy was successful in 91.9% of cases and in 37.8% of cases the cicatricial sequelae were limited to peripheral chorioretinal scars.

Cryotherapy↗
PubMed1990

An autosomal dominant inherited syndrome with congenital stapes ankylosis.

A newly recognized autosomal dominant inherited syndrome associated with congenital conductive deafness, hyperopia, broad thumbs, broad first toes, short distal phalanges, and syndactyly is reported. The conductive loss was the result of congenital stapes ankylosis and, in two cases, was associated with ankylosis of the short process of the incus in the fossa incudis. Stapedectomy improved hearing in these patients. Fused cervical vertebrate are also an associated feature.

Adult↗
PubMed1998

Custom photorefractive keratectomy ablations for the correction of spherical and cylindrical refractive error and higher-order aberration.

Photorefractive keratectomy is an evolving refractive procedure for correcting myopia, hyperopia, and astigmatism. Earlier descriptions of the patterns required for this surgery are based on paraxial optics. In this investigation the required pattern is generalized to account for spherical refractive error (defocus), axial astigmatism of arbitrary orientation, and fourth-order aberrations of the eye. The patterns described in this study can be used to customize photorefractive keratectomy and to provide corrections that account for aberration content as well as paraxial values. Furthermore, a description of the pattern along the boundary of the optical zone is given, which may prove useful in designing blending zones. An example of the use of these techniques is given for a schematic eye model.

Astigmatism↗
PubMed1992

[Automatic tracking system for laser surgery of the human cornea].

An automatic, closed loop, real-time tracking device is described. The purpose of this device is, despite movements of the eye, to keep the laser beam correctly on target while performing corneal surgery. This type of laser surgery, is employed specifically to ablate some of the cornea to correct myopia, hyperopia and astigmatism.

Cornea↗
PubMed1986

[An experimental study of work load on VDT performance. Part 1. Effects of polarity of screen and color of display].

Study were made on the effects of polarity of screen and color of display on work load of VDT tasks. The subjects of the present experiment were eight healthy male college students (age: 21-23 yr) having a naked binocular vision of not less than 0.7 and no astigmatism nor hyperopia. The test consisted of an experimental word processing task in which the subjects visually searched e's in given sequences of alphabetical letters displayed on the CRT and converted them to 5's through keyboard operation. As for experimental conditions, four levels of screen image, that is, positive and negative screens and green and white colored displays were adopted and 2 hr were given for each operation time. Critical flicker fusion (CFF), near point distance, accommodation time, subjective fatigue symptoms, heart rate, electromyogram in upper limbs and performance score were measured. The following results were obtained. Decrease in C.F.F. and extension of near point distance were observed in all experimental conditions during the operating time. Increase in complaints of subjective fatigue related to visual function was observed in all experimental conditions after two hour VDT task. Greater extension of near point distance and larger complaints of subjective fatigue were observed in subjects using the green colored display than in those using the white colored display. This suggests that the visual load using the green colored display is larger than that using the white colored display. A larger decreased in C.F.F. and greater complaints of subjective fatigue were demonstrated in subjects using negative screen than those using positive screen. This suggests that the visual load using the negative screen is larger than that using the positive screen.

Adult↗
PubMed1986

[An experimental study of work load on VDT performance. Part 2. Effects of difference in input devices].

Effects of the difference in input device on work load of VDT task were studied. The subjects of the experiment were eight healthy male college students (age: 21-22 yr) having a binocular vision of not less than 0.7 and no astigmatism or hyperopia. The test consisted of an experimental word processing task in which the subjects visually searched e's in given sequences of alphabetical letters displayed on the CRT and converted them to 5's through input device operation. As for experimental conditions, two kinds of input devices, namely, keyboard and lightpen were adopted and 1 h was provided as each operation time. Critical flicker fusion (CFF), near point distance, accommodation time, subjective fatigue symptoms, blinking counts, pupillary reflex, electromyogram in upper limb, neck and shoulder and performance score were measured. The results were as follows. Decrease in C.F.F. was observed in two experimental conditions during the process of operating time. Increments in complaints of subjective fatigue related to visual function were seen in the two experimental conditions after 1 h VDT task. A higher error rate in performance was observed in the subjects using the lightpen compared to the one using the keyboard. The frequency of both blinking and pupil-size changes were lower in the subjects using the lightpen compared to those using the keyboard. This suggests that the gaze time of the VDT screen with lightpen-condition is longer than that in keyboard-condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Accommodation, Ocular↗
PubMed2005

[Age-related macular degeneration: analysis in two ophthalmological centers in Pernambuco-Brazil].

PURPOSE: To evaluate age-related macular degeneration (AMD) prevalence and its risk factors in two different populations, with distinct socioeconomic conditions, at two ophthalmological centers in Pernambuco state, Brazil. METHODS: A cross-sectional study was performed in 200 volunteers aged 55 years or older. One hundred were cared for by the Public Health System (in the Fundação Altino Ventura FAV-SUS) and 100 were cared for at a private hospital (Hospital de Olhos de Pernambuco-HOPE). There were 400 eyes altogether. Age-related macular degeneration was graded using fundoscopic examination using AREDS classification (Age-Related Eye Disease Study). RESULTS: Presence of age-related macular degeneration was observed in 61 eyes (30%) of the patients of the Fundação Altino Ventura and in 46 eyes (23%) of the patients of the Hospital de Olhos de Pernambuco. The age-related macular degeneration frequency difference between these populations, that are not similar regarding their socioeconomic level, was not significant (p=0.113). There was a positive association between aging and the age-related macular degeneration frequency (p<0.0001). This association was also present in the female gender (p=0.0451), the presence of cataract (p=0.0447), cataract surgery (p=0.0432) and obesity (p<0.0001). No age-related macular degeneration association with race (p=0.1367), hypertension (p=0.1985), diabetes (p=0.6712), smoking (p=0.6374), alcohol intake (p=0.7359), ocular sunlight exposure (p=0.9399), light-colored iris (p=0.1691), hyperopia (p=0.5098) and the usage of antioxidants (p=0.8251) was observed. CONCLUSIONS: The age-related macular degeneration frequency in the two studied ophthalmological centers varied from 23 to 30%. Age-related macular degeneration association with age; female gender; cataract; cataract surgery; and obesity was observed. No age-related macular degeneration association with socioeconomic level was found in this study.

Aged↗
PubMed2005

[Refraction study on pseudophakic children].

PURPOSE: To verify the refractive alterations in eyes of children submitted to surgery with implant of intraocular lens (IOL) and to investigate prediction of biometry in these cases. METHODS: Thirty-three eyes were studied with previous measurement of visual acuity with indication for cataract surgery with implant of intraocular lens in the Outpatient Clinic of Congenital Cataract of the Federal of University of São Paulo/Paulista School of Medicine, (UNIFESP-EPM) from January, 1998 to December, 2000. After the surgery, refraction, prescription of glasses with appropriate treatment for visual stimulation of the children, and measurement of the final corrected visual acuity were performed. Final refraction, biometric accuracy and possible error factors were analyzed. RESULTS: Thirty-three surgeries in 29 children were performed. Mean follow-up time was 10.15 months ranging from 2 to 34 +/- 8.18 months. In 43% of the cases a vision equal to or greater than 20/50 was obtained. Forty-six percent of the patients presented a final refraction between +1.00 and -1.00 spherical diopters. CONCLUSION: Treatment of congenital cataract through implant of intraocular lens continues to be controversial, where long-term results are not known. A great number of patients were operated on at a late time and progressed with amblyopia and low visual acuity even after treatment with difficult access to early and adequate treatment. In spite of residual refraction the patients obtained good visual acuity. Twenty-one percent of the cases with refractive alteration with hyperopia will still have increase in their axial diameter and consequently myopia with reduction of their refraction.

Adolescent↗
PubMed2006

Quantitative comparison of different-shaped wavefront sensors and preliminary results for defocus aberrations on a mechanical eye.

PURPOSE: There is a general acceptance among the scientific community of Cartesian symmetry wavefront sensors (such as the Hartmann-Shack (HS) sensor) as a standard in the field of optics and vision science. In this study it is shown that sensors of different symmetries and/or configurations should also be tested and analyzed in order to quantify and compare their effectiveness when applied to visual optics. Three types of wave-aberration sensors were developed and tested here. Each sensor has a very different configuration and/or symmetry (dodecagonal (DOD), cylindrical (CYL) and conventional Hartmann-Shack (HS)). METHODS: All sensors were designed and developed in the Physics Department of the Universidade de São Paulo--São Carlos. Each sensor was mounted on a laboratory optical bench used in a previous study. A commercial mechanical eye was used as control. This mechanical eye has a rotating mechanism that allows the retinal plane to be positioned at different axial distances. Ten different defocus aberrations were generated: 5 cases of myopia from -1D to -5D and 5 cases of hyperopia, from +1D to +5D, in steps of 1D following the scale printed on the mechanical eye. For each wavefront sensor a specific image-processing and fitting algorithm was implemented. For all three cases, the wavefront information was fit using the first 36 VSIA standard Zernike polynomials. Results for the mechanical eye were also compared to the absolute Zernike surface generated from coefficients associated with the theoretical sphere-cylinder aberration value. RESULTS: Precision was analyzed using two different methods: first, a theoretical approach was used by generating synthetic Zernike coefficients from the known sphere-cylinder aberrations, simply by applying sphere-cylinder equations in the backward direction. Then comparisons were made of these coefficients with the ones obtained in practice. Results for DOD, HS and CYL sensors were, respectively, as follows: mean of root mean square (RMSE) for all aberrations, when theoretical Zernike coefficients were used as control, was 0.22, 0.66 and 0.26 microns; RMSE of sphere-cylinder values when compared to autorefractor measurements was 0.18D, 0.22D and 0.35D for sphere, 0.14D, 0.24D and 0.17D for cylinder, 34.36 degrees, 35.16 degrees and 26.36 degrees for axis; RMSE of sphere-cylinder values when theoretical values were used as control was 0.11D, 0.29D and 0.46D for sphere, 0.15D, 0.28D and 0.17D for cylinder, 19.71 degrees, 25.56 degrees and 18.56 degrees for axis. CONCLUSION: The main conclusion is that the symmetry of an optical sensor is not an important consideration when measuring typical eye aberrations such as defocus (myopic and hyperopic), but there are differences. In this sense, the polar symmetry sensors render results that are equivalent to the traditional Cartesian Hartmann-Shack sensor, but furnish an easier method for determining the optical center.

Calibration↗
PubMed2002

Measuring higher order optical aberrations of the human eye: techniques and applications.

In the present paper we discuss the development of "wave-front", an instrument for determining the lower and higher optical aberrations of the human eye. We also discuss the advantages that such instrumentation and techniques might bring to the ophthalmology professional of the 21st century. By shining a small light spot on the retina of subjects and observing the light that is reflected back from within the eye, we are able to quantitatively determine the amount of lower order aberrations (astigmatism, myopia, hyperopia) and higher order aberrations (coma, spherical aberration, etc.). We have measured artificial eyes with calibrated ametropia ranging from +5 to -5 D, with and without 2 D astigmatism with axis at 45 degrees and 90 degrees. We used a device known as the Hartmann-Shack (HS) sensor, originally developed for measuring the optical aberrations of optical instruments and general refracting surfaces in astronomical telescopes. The HS sensor sends information to a computer software for decomposition of wave-front aberrations into a set of Zernike polynomials. These polynomials have special mathematical properties and are more suitable in this case than the traditional Seidel polynomials. We have demonstrated that this technique is more precise than conventional autorefraction, with a root mean square error (RMSE) of less than 0.1 micro m for a 4-mm diameter pupil. In terms of dioptric power this represents an RMSE error of less than 0.04 D and 5 degrees for the axis. This precision is sufficient for customized corneal ablations, among other applications.

Corneal Topography↗
PubMedDate not supplied

LASIK complications and the Internet: is the public being misled?

BACKGROUND: LASIK (Laser in Situ Keratomileusis) is a very popular combined surgical and laser procedure, which is used to correct myopia (shortsightedness) and hyperopia (farsightedness). There is concern that the public is being misled regarding the safety of the procedure. OBJECTIVES: To assess the quality and quantity of the information on complications on LASIK Web sites. METHOD: Serial analysis and evaluation of the authorship, content, and technical quality of the information on the complications of LASIK on 21 Web sites. RESULTS: Of the 21 LASIK Web sites visited, 17 were commercial. Of the 21 Web sites, 5 (24%) had no information on complications. Of the 16 sites that had information on complications the author of the information was clearly identified in 5 (31%), the content was only referenced in 2 (12.5%), and evidence of the information having been updated was only seen in 2 (12.5%). The quantity of information is generally minimal and the information itself is generally difficult to understand and locate. CONCLUSION: The quality and quantity of the information on the Web on the complications of LASIK are poor. More work is required to encourage clear, accurate, up-to-date, clearly authored, and well-referenced, balanced ophthalmic information.

Authorship↗
PubMed1989

Visual postural performance in ametropia and with optical distortion produced by bifocals and multifocals.

Visual stabilization of posture depends strongly on the performance of the visual system and declines with experimentally induced reduction of visual image quality. We studied postural performance in subjects with median and high grade hyperopia or myopia. While body sway of median grade ametropic subjects increased slightly when measured without glasses, high grade ametropia showed no significant differences between postural performance with glasses on and off. We concluded that the increase in visual acuity when wearing glasses is outweighted by concurrent dioptric distortions such as size change and prismatic effects. In addition we could not find any difference between bifocal and multifocal lenses in their effect on sway when investigated in normals with either steady fixation or saccades or foveal pursuit.

Adult↗
PubMed1981

Epikeratophakia: the surgical correction of aphakia. I. Lathing of corneal tissue.

Epikeratophakia is a newly developed form of refractive corneal surgery for the correction of hyperopia. In this procedure, a piece of donor corneal tissue is lathed to a specific dioptric power. The epithelial cells are removed from the recipient cornea, and the donor tissue is sutured to the front of the eye. The resulting change in corneal curvature provides the visual correction, as, for instance, in the correction of aphakia. We describe here the computational analysis used to lathe human donor corneal tissue for use as epikeratophakia grafts. With these equations, the precision of the observed thickness of the lathed lenticule was +/- 0.05 mm and the precision of the observed diameter was +/- 0.25 mm. We found that, in a graft of a given diameter, the smaller the optical zone, the greater the maximal dioptric power of the graft, limited only by the central thickness of the donor cornea and the mechanical limitations of the cryolathe. In our case, the highest theoretical correction obtainable was 37 diopters.

Aphakia, Postcataract↗
PubMed1987

Visual deprivation causes myopia in chicks with optic nerve section.

Deprivation of form vision restricted to a region of the retina produces myopia and axial elongation only in that region. We asked whether this control of eye growth by the presence or absence of visual stimuli might take place entirely within the eye. Chicks with neonatal optic nerve section, wearing an occluder that deprived one half of the retina of form vision, had vitreous chamber elongation and myopia both restricted to the deprived region. Chicks with optic nerve section but without occluders had eyes smaller than normal with severe hyperopia. These results suggest that two different mechanisms may control eye growth, one within the eye and the other in the brain.

Animals↗