Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Hyperopia”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,099 records · Page 61Linked to original sources
PubMed1996

ERG of form deprivation myopia and drug induced ametropia in chicks.

Chick eyes occluded for various periods or treated with various concentrations of kainic acid (KA) or 2-amino-4-phosphonobutylate (APB) during development showed characteristic changes of electroretinography and of refraction. In occluded eyes, oscillatory potential amplitudes (OP-A) were reduced, even with high-intensity stimulation, in proportion to duration of occlusion, but b wave amplitude was unchanged, implying functional changes in inner layers of the deprived retina. OP-A reduction after only 1 week of occlusion and reversibility of this change might reflect retinal changes preceding axial elongation. KA was confirmed to induce myopia with axial elongation and APB to induce hyperopia with axial shortening. KA and APB both suppressed OP-A. KA reduced ON and OFF responses, but low-dose APB suppressed only ON responses. Study results suggest that myopia could be induced by changes of inner retina mediating OP attenuation and degradation of ON and OFF responses. This manuscript reports unpublished work that is not currently under consideration for publication elsewhere.

Aminobutyrates↗
PubMed1988

A pedigree of Leber's congenital amaurosis.

A pedigree of Leber's congenital amaurosis compatible with autosomal recessive trait is reported. Two male infants from consanguineous parents had remarkable visual loss within the first year of life, with sluggish pupillary responses, poor fixations, minimal eyeground changes and absent electroretinograms on presentations at the ages of four or 14 months. Follow-up studies revealed definite progressions of eyeground abnormalities consisting of attenuated retinal arterioles, pepper- and salt-like appearance with numerous yellowish-white punctate lesions in the midperiphery, and pale optic nerves. Fluorescein angiographic study performed on one case showed multiple hyperfluorescent spots over the posterior and midperipheral eyegrounds suggesting alterations of the retinal pigment epithelium. These functional and morphological abnormalities of the retina were similar in the two siblings. Cycloplegic refractions revealed slight myopic or mixed astigmatism, but no marked hyperopia. The patients had normal physical and mental developments with no obvious systemic complications.

Blindness↗
PubMedDate not supplied

Development of the eyeball during fetal life.

Two hundred fifty-two undamaged human fetuses without external malformations were supplied by the human embryo and fetus collection of the Department of Anatomy, Kyoto University. The sagittal, vertical and horizontal diameters of the eyeball were measured by micrometer, and the transverse, vertical and horizontal circumferences of the eyeball were measured by mapmeter from photographs of the side views of the eye. All the diameters of the eyeball showed a parallel linear increase from the 12th to the 40th week of menstrual age. The increase of circumferences of the eyeball paralleled each other throughout the 12th to the 40th week. It is significant that the sagittal diameter of the eyeball is shorter than the vertical and transverse diameters during fetal life. The vertical meridian circumference of the eyeball is also shorter than the transverse and horizontal meridian circumferences during fetal life. These findings suggest that many infants are apt to have hyperopia at birth.

Eye↗
PubMedDate not supplied

Polaroid photorefractive screening of infants.

We modified a Polaroid SE camera for use as a photoretinoscope. A total of 187 infants between 2 and 18 months of age were photographed using this device. About half of these infants (97) participated in a double blind study in which the results of photorefraction were compared with those of standard cycloplegic retinoscopy. Eighty-three infants were photographed without cycloplegia. Thirty-four infants were photographed while cyclopleged. Photographs were evaluated for significant refractive errors and other ocular abnormalities. The effectiveness of the camera system to screen for significant refractive errors without the use of cycloplegia was assessed. Infants were identified to be at risk by photorefraction if, in any photograph, a hyperopic bright crescent calculated to be greater than or equal to +1.25 D was present in the pupil. Clinically significant refractive errors were defined by the results of cycloplegic retinoscopy: "at-risk" infants had either 3.5 D or more hyperopia in either eye, or astigmatism in either eye greater than or equal to 2.5 D, or anisometropia greater than or equal to 1.5 D. With these clinical criteria and the above photographic screening criterion, the camera's sensitivity and specificity were 83% and 69%, respectively. The present system compares favorably with earlier, more sophisticated units in alerting practitioners to potentially significant refractive errors in infants. Additionally, as a screening tool, this device offers the benefits of being inexpensive and easy to use, and of providing immediate feedback.

Calibration↗
PubMedDate not supplied

Long-term results of bifocal therapy for accommodative esotropia.

We studied the long-term course of 65 accommodative esotropes who required bifocals to maintain alignment at near. Average follow-up was 10.5 years. Forty patients (61.5%, group DC [bifocals discontinued]) were able to discontinue bifocal use after an average of 5.5 years wear. Twenty-five (38.5%) continued to wear bifocals (or a suitable alternative such as reading glasses), after an average 9.7 years of follow-up. Surgical correction of deteriorated accommodative esotropia was performed for 20 patients (50%) in group DC, and nine (36%) of those in group C[bifocals continued]. Surgery produced an average reduction in the accommodative convergence relationship (near esodeviation in prism diopters [pd] minus corrected distance measurement, AC/A) of approximately 10 pd in both groups. Surgical patients unable to discontinue bifocal wear began with a clinically higher AC/A than those in group DC. Non-surgical patients in group DC experienced spontaneous improvement of the AC/A over time (average, 6.2 pd). On average, this did not occur in those of group C. Average age of bifocal discontinuation was 9.7 years in surgical patients and 9.3 years in the non-surgical. Surgical patients had significantly lower hyperopia (+2.4 diopters [D]), than non-surgical (+3.5 D), and an earlier age of onset of bifocal wear (3.29 versus 4.64 years). Although bifocals may be successfully discontinued in a majority of patients at an average age of 9.5 years, a significant percentage require long-term wear, some, despite surgery. The only factor that predicted long-term bifocal wear was a relatively high AC/A.

Accommodation, Ocular↗
PubMedDate not supplied

Clinical characteristics and surgical treatment of intermittent esotropia.

This study describes the age of onset, symptomatology, and clinical characteristics of 25 patients with intermittent esotropia. This subgroup of esotropic patients typically has onset prior to 10 years of age and shows excellent bifoveal fixation ability, reflected by a high degree of stereopsis. In contrast to patients with other forms of esotropia, there is minimal to no hyperopia, an average esodeviation of approximately 20 prism diopters, and a low incidence of amblyopia, DVD, and oblique overaction. Symptomatic diplopia or cosmetic concern necessitated surgical intervention in 17 (68%) patients. Fifteen (88%) patients had good or excellent surgical results of either orthophoria, esophoria, or residual esotropia of 10 delta or less. One patient (6%) had residual esophoria greater than 10 delta. One patient had 4 delta of exophoria postoperatively. Intermittent esotropia should be differentiated from the various entities of microtropia, fixation disparity, and monofixation syndrome.

Adolescent↗
PubMedDate not supplied

19th annual Frank Costenbader Lecture--the origins of congenital esotropia.

Congenital esotropia develops in the first 4 months of life in an infant who lacks the inborn mechanism for motor fusion. It manifests as an esotropia which is not eliminated by correction of hyperopia and occurs in an otherwise neurologically normal infant. The earliest practical time for surgery is 4 months of age. The eye is anatomically suited for surgery at this age and also, this is the earliest age that congenital esotropia can be diagnosed with confidence. The best attainable result of treatment of congenital esotropia is subnormal binocular vision. This result is more likely to be attained if infants are aligned by 18 months of age. Satisfactory alignment is produced in 80% to 85% of infants in one procedure with an appropriate bimedial rectus recession. An array of motor defects including DVD, latent nystagmus, oblique dysfunction, and A- and V-pattern appear at varying times after successful alignment. These associated findings are commonly found with, but are not unique to, congenital esotropia. The onset and clinical picture of congenital esotropia is satisfactorily explained by a theory first suggested by Worth that the strabismus is caused by an inborn defect in the motor fusion mechanism and aggravated by esotropital factors as suggested by Chavasse. In contrast to congenital esotropia, all other strabismus can be thought of as occurring on a secondary basis in a person with the inborn capacity for motor fusion, but who failed to maintain it because of conatal insurmountable strabismus (congenital third nerve palsy), who lost it because of acquired (postnatal) strabismus, who uses a strategy such as head posture alteration to retain fusion under favorable circumstances (Duane syndrome), who has intermittent strabismus with part-time suppression (X(T)), or who is maintaining alignment with nonsurgical means (refractive esotropia). For the future, I believe that advances in the management of congenital esotropia will depend on a better understanding of etiology leading to design and use of innovative nonsurgical techniques to discourage convergence and stimulate bifoveal fusion.

Awards and Prizes↗
PubMedDate not supplied

Accommodative esotropia in adults.

The accommodative convergence/accommodation (AC/A) ratio is thought to be fixed throughout life. We present 11 patients who, in adulthood, show a situational increase in their AC/A ratio. Since all patients had a history of accommodative esotropia with and without a nonaccommodative component, we feel the situational increase in the AC/A ratio is in response to the additional effort needed to correct the patients' facultative hyperopia. These patients demonstrate the importance that all adults with acute onset of commitant esotropia and a history of accommodative esotropia should wear full correction before a prism is incorporated into their glasses or surgical intervention is considered.

Accommodation, Ocular↗
PubMedDate not supplied

The effects of experimentally induced anisometropia on stereopsis.

PURPOSE: To determine the effects of experimentally induced anisometropia on stereopsis in healthy adults to assess the potentially detrimental effects of uncorrected anisometropia on the development of stereoacuity during childhood. METHODS: Twenty-one healthy adult volunteers ranging in age from 22-34 years (mean: 27 years) and free of ocular disease participated in the study. Four different types of anisometropia (unilateral myopia, unilateral hyperopia, or unilateral astigmatism [90 degrees or 45 degrees]) were induced in random order by placing trial lenses over the right eye in 1 diopter (D) increments ranging from 1-3 D. Stereoacuity was measured using the Titmus stereotest with patients placing the cross-polarizing stereoacuity glasses over their lenses or trial frames. RESULTS: Stereoacuity levels were reduced in proportion to the degree of anisometropia in all patients. One diopter of spherical anisometropia reduced stereoacuity to an average 57-59 arc seconds; 1 D of cylindrical anisometropia reduced stereoacuity to an average 51-56 arc seconds. Three diopters of anisometropia, regardless of type, produced a marked reduction of stereoacuity in all patients. CONCLUSIONS: Low levels of anisometropia, both spherical and astigmatic, can have potentially significant adverse effects on high-grade binocular interaction in adults. Foveal suppression, which is directly related to the degree of anisometropia, may be responsible for the loss of stereopsis. The data suggest the effects of anisometropia on stereopsis should be considered in the empiric correction of anisometropic refractive errors in children.

Adult↗
PubMedDate not supplied

Distribution and determinants of intraocular pressure in a normal pediatric population.

PURPOSE: To examine the intraocular pressure (IOP) of a normal pediatric population under topical anesthesia without sedation and its correlation with other ocular parameters. SUBJECTS AND METHODS: The IOP of 810 eyes of 405 patients with ages ranging from 0 to 12 years was measured using the Perkins applanation tonometer. Cooperative patients also underwent pachymetry, refraction, and biometry measurements. RESULTS: The mean (+/- standard deviation) age was 6.68 (+/- 3.28) years, with a mean (+/- standard deviation) IOP of 12.02 (+/- 3.74) mm Hg. IOP showed an increasing trend with age (correlation coefficieit [r] = 0.49) and tended to approach adult levels by 12 years of age. The IOP correlated directly with refraction (r = 0.69) and pachymetry (r = 0.39) and inversely with axial length (r = -0.1). CONCLUSIONS: The IOP in children is much lower than that in adults. It was noted to increase with age, hyperopia, and corneal thickness and was inversely proportional to axial length.

Age Factors↗
PubMedDate not supplied

Comparison of 5-mm and 6-mm ablation zones in photorefractive keratectomy for myopia.

BACKGROUND: Variation in ablation zone diameter may alter visual acuity and/or refractive effect in photorefractive keratectomy. Despite theoretical benefits of using a smaller diameter ablation zone, clinical studies suggest that a larger ablation zone may decrease problems associated with photorefractive keratectomy. METHODS: The results of our initial 34 consecutive eyes treated with a 5-mm diameter ablation zone using a Summit Technology ExciMed UV200LA excimer laser were compared retrospectively to our initial 34 consecutive eyes treated with a 6-mm diameter ablation zone using a Summit OmniMed excimer laser. Eyes had a spherical equivalent refraction between -1.00 and -6.00 diopters (D) and astigmatism less than 1.00 D. Patients were followed for a minimum of 6 months. RESULTS: Eyes treated with a 6-mm ablation zone had less hyperopia and a spherical equivalent refraction closer to emmetropia at 1, 2, and 3 months (P = 0.001). Eyes treated with a 6-mm ablation zone had better uncorrected visual acuity at 1 and 2 months (P = 0.001). Less subepithelial haze was noted at 2 months (P = 0.01) and 3 months (P = 0.002) in the 6-mm group. At 6 months postoperatively, 30 of 32 eyes (94%) treated with a 6-mm ablation zone had a spherical equivalent refraction within 0.50 D of emmetropia, and all 32 eyes (100%) were within 1.00 D of emmetropia; in the 5-mm ablation zone group, 28 of 34 eyes (80%) were within 0.50 D and 29 (85%) were within 1.00 D of emmetropia. Patients treated with a 6-mm ablation zone complained less of night halos and had fewer differences between night and day vision. CONCLUSIONS: In this study of myopia of -1.00 D to -6.00 D, eyes treated with a 6-mm ablation zone achieve a more rapid visual recovery with less variation in refractive outcome and less adverse effects than those treated with a 5-mm ablation zone.

Adult↗
PubMedDate not supplied

Holmium:YAG laser thermokeratoplasty for astigmatism in rabbits.

BACKGROUND: Holmium:YAG laser thermokeratoplasty has generated considerable interest as a technique for correcting hyperopia. In this study, the effect of holmium:YAG laser on inducing astigmatism according to application patterns was evaluated. METHODS: An experimental study based on the results of astigmatic holmium:YAG laser thermokeratoplasty using the Summit OmniMed laser system (Summit Technology Inc, Waltham, Mass) in 36 rabbit eyes is presented. We divided the rabbits into four groups: arcuate, reverse arcuate, linear, and control group according to application patterns. All rabbits were followed for 3 months and cycloplegic refractive measurements were carried out. RESULTS: The average surgically induced astigmatism was 1.86 diopters (D) for the arcuate group, 2.93 D for the reverse arcuate group, and 1.31 D for the linear group. No significant complications related to the operation were noted. CONCLUSION: The reverse arcuate pattern of holmium:YAG laser thermokeratoplasty is most effective in inducing astigmatism in rabbits.

Animals↗
PubMedDate not supplied

Corneal asphericity and its implications for photorefractive keratectomy: a mathematical model.

BACKGROUND: Several clinical trials investigating myopic excimer laser photorefractive keratectomy (PRK) report an initial change in refraction from myopia to hyperopia, followed by a gradual regression toward emmetropia and occasionally to recurrent myopia. We examined the effect of corneal shape on refraction following PRK for myopia using a mathematical model. METHODS: We calculated the volume of corneal tissue removed by PRK for -3.00-diopter (D) and -6.00-D corrections with ablation diameters of 5 mm and 6 mm. For all the operating algorithms, the central region of the cornea was considered spherical. Mathematical models were developed based on calculations of the apical radius of the ablated cornea and the final refraction for a range of corneal asphericities. Baker's equation was used to model corneal asphericity. RESULTS: The smaller both the ablation size and desired correction, the smaller the effect of corneal asphericity on the refractive outcome. While corneal asphericity can influence the immediate refraction after PRK, the maximum effect is unlikely to be greater than +0.75 D. CONCLUSIONS: Corneal asphericity marginally affects the initial outcome of PRK. The effect will probably be offset by the healing response of the cornea.

Cornea↗
PubMedDate not supplied

Histologic changes and wound healing response following 10-pulse noncontact holmium:YAG laser thermal keratoplasty.

BACKGROUND: Noncontact holmium:YAG laser thermal keratoplasty (Ho:YAG LTK) is a promising new technology for correction of hyperopia and astigmatism. We studied the acute histologic changes and wound healing response following Ho:YAG LTK performed with treatment parameters encompassing those used in clinical studies. METHODS: We performed 10-pulse noncontact Ho:YAG LTK on three human corneas 1 day before their removal at penetrating keratoplasty and on six New Zealand white rabbit corneas followed for up to 3 months. Tissues were studied with light and transmission electron microscopy and immunohistochemistry. RESULTS: The amount of acute tissue injury increased according to the pulse radiant energy. In human corneas, changes in the irradiated zones included epithelial cell injury and death, loss of fine filamentous structure in Bowman's layer, disruption of stromal lamellae, and keratocyte injury and death. In the rabbit corneas, similar acute changes were noted. By 3 weeks, epithelial hyperplasia and stromal contraction were present. Wound healing in the rabbits included repair of the epithelial attachment complex, keratocyte activation, synthesis of type I collagen, partial restoration of stromal keratan sulfate and type VI collagen, and retrocorneal membrane formation. CONCLUSIONS: Noncontact Ho:YAG LTK produces acute epithelial and stromal tissue changes and in rabbit corneas stimulates a brisk wound healing response.

Animals↗
PubMedDate not supplied

Microbiological examination of bandage soft contact lenses used in laser refractive surgery.

BACKGROUND: Disposable soft contact lenses are known to be colonized by bacteria and play a key role in bacterial keratitis pathogenesis. Such lenses, commonly used after laser refractive surgery procedures in which postoperative corneal infiltrations are sometimes observed, are potentially a substrate for bacterial inoculation. This study evaluates the extent of such a contamination. METHODS: Sixty disposable lenses collected from 60 eyes of patients who underwent photorefractive keratectomy (PRK), photoastigmatic refractive keratectomy (PARK), or laser in situ keratomileusis (LASIK) for the treatment of myopia or hyperopia were collected under sterile conditions over 4 months and cultured in various media. Results were statistically analyzed and the correlation with clinical and epidemiological data was examined. RESULTS: Eleven (18.3%) of the examined lenses were contaminated with Staphylococcus epidermidis. No other bacteria or fungi were found. Contamination was significantly more common among female patients (P = .036). Correlation with the other clinical or operative parameters examined was statistically insignificant. CONCLUSIONS: Contamination was independent of the surgical procedure and females who were frequent users of eyelid cosmetics displayed higher contamination frequencies, suggesting that bacteria possibly originate from eyelid flora. The isolation of Staphylococcus epidermidis requires close postoperative surveillance, since it is a known cause of keratitis. Prophylactic postoperative treatment with tobramycin, gentamycin, or sulphonamides could be indicated.

Adolescent↗
PubMedDate not supplied

Experience with the Nidek MK-2000 microkeratome in 1,220 cases.

PURPOSE: To evaluate the performance of the Nidek MK-2000 microkeratome. METHODS: The Nidek MK-2000 microkeratome was used in 1,220 cases of LASIK with the Nidek EC-5000 excimer laser. Patients had a wide range of myopia (-0.75 to -25.00 D), hyperopia (+0.75 to +9.00 D) and/or astigmatism (-7.00 to +6.50 D). The flap was created with the 130-microm microkeratome plate for 859 eyes, and the 160-microm plate for 361 eyes. In 632 eyes, the 8.5-mm ring was used, and the 9.5-mm ring was used in 588 eyes. The flap hinge was placed nasally, superiorly, or inferiorly depending on the needs of the case. An easy external modification allowed us to gently increase and decrease the vacuum level and to perform the procedure using a low vacuum regimen, if necessary. RESULTS: The edges of the flaps and the corneal surface were of good quality in all eyes. No free flaps were noted. One case was aborted because of inappropriate flap formation in a patient with a large difference (6.50 D) in corneal curvature in two main meridians. This patient successfully underwent LASIK 1 month later, placing the flap hinge in the opposite direction. Small epithelial shrinkage was noted in 38 eyes. No other flap complications were noted. In all patients the flap diameter and thickness were close to that estimated by the manufacturer. The vacuum level was adequate and stable in all cases. CONCLUSION: The Nidek MK-2000 microkeratome was easy to use, predictable, and safe. However, we suggest a modification, adding an adjustable head movement to create wider hinge-to-center-of-pupil distance and an additional 9.0-mm suction ring.

Anthropometry↗
PubMedDate not supplied

Wavefront customized ablations with the WASCA Asclepion workstation.

PURPOSE: WASCA (Wavefront Aberration Supported Cornea Ablation) is a method for wavefront-guided ablation. This new method records all existing eye aberrations with the Asclepion Wavefront Aberrometer and calculates the customized pattern for laser correction. We measured the low and high order aberrations of eyes before and after PRK and LASIK, as well as before and after flap creation. METHODS: The Asclepion Shack-Hartmann aberrometer was used to measure wavefront aberrations. Preoperative and postoperative measurements were made following both PRK and LASIK performed with conventional software, modified Aberration-free Profile (AFA) software, and specially designed WASCA software. Surgery was performed with the Meditec MEL-70 G-scan excimer laser. Additionally, measurements were made before and after flap creation only (10 eyes). RESULTS: There was a significant difference between preoperative and 1-month postoperative high order aberrations, with notable increases following conventional PRK and LASIK and less increase following modified AFA PRK and LASIK. Flap creation only changed the higher order aberrations slightly, and caused a shift toward hyperopia. In the eyes that received WASCA correction with PRK or LASIK, at 3 months postoperative the high order aberrations averaged an increase of 1.3 times for PRK and 1.8 times for LASIK. Both the AFA and WASCA treatments demonstrated improved outcomes in comparison to conventional PRK and LASIK. CONCLUSION: Wavefront mapping of the eye and wavefront-guided ablation with the Asclepion Aberrometer can be used for optimizing the results and fine-tuning visual performance after laser vision correction. WASCA PRK appeared to result in better outcomes than WASCA LASIK.

Astigmatism↗
PubMedDate not supplied

U.S. trends in refractive surgery: 2001 International Society of Refractive Surgery Survey.

PURPOSE: To determine the trends in refractive surgery in the United States in 2001. METHODS: The 980 U.S. members of the International Society of Refractive Surgery were mailed the 2001 refractive surgery survey dealing with volumes, types, and preferences of refractive surgery performed. Questions regarding radial keratotomy, astigmatic keratotomy, photorefractive keratectomy, laser in situ keratomileusis (LASIK), laser subepithelial keratomileusis, intracorneal rings (Intacs), laser thermal keratoplasty, conductive keratoplasty, clear lens extraction, phakic intraocular lenses, and scleral expansion procedures for presbyopia were examined in the survey. Procedure preferences for low, moderate, and high myopia and hyperopia were compared with the results from the surveys of the previous 4 years. Preference for unilateral versus bilateral same-day surgery, laser type, and microkeratome choice were also compared with the survey data from previous years. Incidence and frequency of comanagement of refractive surgery patients were compared with 2000 data. RESULTS AND CONCLUSION: LASIK remains the dominant refractive surgery for refractive errors from -12.00 to +3.00 D; the VISX excimer laser and the Hansatome microkeratome are the most frequently used instruments for LASIK.

Health Care Surveys↗