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At least 1,513 records · Page 84Linked to original sources
PubMed1984

A new posterior chamber intraocular lens formula for axial myopes.

The accuracy of prediction of postoperative refractive error was evaluated in 175 patients with extracapsular cataract extraction and a Shearing-style posterior chamber intraocular lens. The Binkhorst, Colenbrander - Hoffer and SRK formulas were all less accurate in patients with an axial length greater than or equal to 24.5 mm. The standard error of the estimates of the Binkhorst formula was 1.2 diopters, the Colenbrander - Hoffer formula 1.18 diopters and the SRK formula 0.90 diopters. A new intraocular-lens formula for axial myopes was derived by polynomial regression analysis with a standard error of the estimate of 0.85 diopters. This new formula was accurate within 1 diopter in 79% of axial myopes compared to 71% for the SRK , 66% for the Colenbrander - Hoffer and 64% for the Binkhorst formulas. Regression analysis of a surgeon's own patient data can further improve the accuracy of prediction of the post-operative refraction.

Cataract Extraction↗
PubMed1986

Photographic detection of amblyogenic factors.

Refractive errors were determined photographically in a group of infants and children and were compared to conventional cycloplegic retinoscopy. The refractor consisted of a mirror telephoto lens and strobe flash designed to mimic the action of a retinoscope. Significant amblyogenic conditions such as anisometropia and high isoametropia were detectable. Strabismus and media opacities were also recordable. The technique provides a potential mass suited for infants.

Amblyopia↗
PubMed1987

Contact lenses in the treatment of patients with overcorrected radial keratotomy.

Thirty-two eyes of 28 patients who underwent radial keratotomy had a hyperopic overcorrection after the surgical procedure. Anisometropia, with associated aniseikonia and depth perception problems were present in many of these patients. The patients were subsequently fit with contact lenses. Conventional methods of fitting contact lenses in these patients were unsuccessful. A trial lens technique is used with the initial lens having a base curve equal to the preoperative keratometry measurements and the power equal to the preoperative spherical equivalent. Superficial neovascularization developed within the radial incisions in 33% of the eyes fitted with soft contact lenses. Gas permeable contact lenses offered patients the best-corrected visual acuity as well as minimal complications. In addition, the anisometropia was minimized, and fluctuating vision was eliminated in cases in which it was a problem.

Contact Lenses↗
PubMed1988

The Williams syndrome. Spectrum and significance of ocular features.

Forty-two subjects with classic features of Williams syndrome were evaluated to ascertain the prevalence and severity of the ophthalmologic features associated with the disorder. Twenty-six (62%) had a stellate pattern of the anterior iris stroma which was observed only in individuals with blue or hazel iris color. Twelve (29%) had strabismus, most commonly esotropia. Hypermetropic discs were noted in 18 of 33 patients (55%), a simplex vertical branching of the central retinal vessels at the disc in 23 (70%), and situs inversus vasorum in 5 (15%). No subject had accentuated vascular tortuosity, which has been reported previously as a hallmark of this syndrome. No ocular manifestation of infantile hypercalcemia was noted in any subject.

Abnormalities, Multiple↗
PubMed1989

Lens rim artifact in automated threshold perimetry.

In central static threshold visual fields (Humphrey 30-2 Program) performed with a corrective lens, lens rim artifact (LRA) was present in 10.4% of 704 fields examined retrospectively and 6.2% of 276 fields evaluated prospectively. Lens rim artifact most commonly presented as a combination of absolute and relative defects involving the temporal quadrant either alone or in combination with another quadrant. Lens rim artifact was related to seven different types of interpretational errors, five of which led to an overdiagnosis and two to an underdiagnosis. Risk factors for the occurrence of LRA include older age, high hyperopic correction, and location specific involvement probably due to a limitation in perimeter design. Field defects involving only the four targets at 27 degrees eccentricity in the temporal quadrant were due only to LRA in this series and may be disregarded when interpreting the Humphrey 30-2 Program. Recommendations are made toward minimizing the occurrence of LRA and avoiding interpretational errors associated with LRA.

Adult↗
PubMed1992

Keratophakia and keratomileusis: safety and effectiveness. American Academy of Ophthalmology.

The purpose of the Committee on Ophthalmic Procedures Assessment is to evaluate on a scientific basis new and existing ophthalmic tests, devices, and procedures for their safety, efficacy, clinical effectiveness and appropriate uses. Evaluations include examination of available literature, epidemiological analyses when appropriate, and compilation of opinions from recognized experts and other interested parties. After appropriate review by all contributors, including legal counsel, assessments are submitted to the Academy's Board of Directors for consideration as official Academy policy.

Aphakia↗
PubMed1996

Refractive changes during 72-hour exposure to high altitude after refractive surgery.

PURPOSE: The authors prospectively analyzed refractive and pachymetric parameters during exposure to high altitude after radial keratotomy (RK) and photorefractive keratectomy (PRK). METHODS: The authors measured manifest and cycloplegic refraction, keratometry, computed video keratography, and central and peripheral pachymetry in six subjects who have undergone RK (11 eyes), six who have undergone PRK (12 eyes), and nine with myopia (17 eyes) at sea level and on three consecutive days at 14,100 feet. All measurements were repeated 1 week after subjects returned to sea level. RESULTS: Subjects who have undergone RK demonstrated a significant and progressive increase in spherical equivalence (+0.30 +/- 0.50 diopters on day 1 and +1.52 +/- 1.01 diopters on day 3; P < 0.001) and a decrease in keratometry values during exposure to altitude when compared with control subjects with myopia. Healthy subjects and those who have had PRK demonstrated no significant change in refractive error. Pachymetry measurements demonstrated significant peripheral corneal thickening in all three groups (RK, P < 0.004; PRK, P < 0.007; control subjects, P = 0.0006) by day 3 at high altitude. Refraction, keratometry, and pachymetry returned to baseline (P = 1.000) after return to sea level. CONCLUSIONS: Seventy-two-hour exposure to high altitude in subjects who have had RK induces a significant, progressive, and reversible hyperopic shift in refraction with corresponding video keratographic and keratometric changes. The authors hypothesize that the high-altitude hypoxic environment causes increased corneal hydration in the area of the RK incisions, which may lead to central corneal flattening and a hyperopic shift in refractive error. Subjects who have had PRK and those with myopia are not susceptible to this refractive shift. The authors' RK data suggest that the time since surgery and the amount of surgery are related to the degree of hyperopic shift during altitude exposure.

Adult↗
PubMed1996

Effects of simulated high altitude on patients who have had radial keratotomy.

BACKGROUND: Previous studies documented diurnal myopic shifts in patients who have had radial keratotomy (RK). Recently, hyperopic shifts in these patients exposed to high altitude have been reported. A direct mechanical effect of reduced barometric pressure on surgically altered corneas has been theorized to cause this hyperopic shift. Another hypothesis implicates the effect of hypobaric hypoxia on the RK incisions. The authors examined the effect of a 6-hour exposure to decreased barometric pressure on 14 normal and 18 RK corneas. METHODS: Cycloplegic refraction, keratometry, corneal pachymetry, and tonometry were performed on seven control subjects and nine patients who have had RK. Measurements were obtained over 8 hours at sea level on day 1 of the study. Measurements were repeated on day 2 which included a 6-hour exposure to 12,000 feet simulated altitude in a hypobaric chamber. Results were compared between subjects and control subjects to determine the effect of a 6-hour exposure to decreased barometric pressure. RESULTS: There was no statistically significant difference in refraction or keratometry readings between control subjects and subjects who have had RK. Central corneal thickness decreased in the afternoon in RK eyes compared with control eyes. There was no clinically significant difference in intraocular pressure between subjects who have had RK and control subjects. CONCLUSIONS: A measurable hyperopic shift in RK corneas exposed to high altitude requires more than 6 hours to develop. A direct effect on corneal shape due to barometric pressure alone should produce a sudden change in refractive error. This study supports the hypothesis that a slow metabolic process is responsible for the previously documented hyperopic shifts induced by altitude. However, a barometric pressure effect requiring more than 6 hours to occur cannot be ruled out with the methodology used in this study.

Adult↗
PubMed1997

Etiology and prognosis of acute, late-onset esotropia.

OBJECTIVE: The purpose of the study is to review etiologies and outcomes of sudden, late-onset esotropia. DESIGN: The authors reviewed charts of patients in whom acute, comitant, constant esotropia developed after 5 years of age. MAIN OUTCOME MEASURES: The authors evaluated final ocular alignment, treatment, fusion, apparent etiologies, and associated neurologic conditions. RESULTS: Ten patients met entry criteria with documentation of previous orthotropia. Ages ranged from 5 to 35 years. Esotropia at near ranged from 16 to 70 prism diopters. In seven patients, the esotropia improved partially or completely with correction of hypermetropia. Eight patients required surgery. In only one patient were neuroimaging studies positive, associated ophthalmic and systemic findings identified, and underlying neurologic disease diagnosed. CONCLUSIONS: Sudden, late-onset esotropia may be caused by an uncorrected refractive error. If no other neurologic signs are present, underlying intracranial disease is unlikely.

Acute Disease↗
PubMed1998

The etiology of refractive changes at high altitude after radial keratotomy. Hypoxia versus hypobaria.

OBJECTIVE: Refractive changes at high altitude that occur after radial keratotomy (RK) may be caused by hypoxia or hypobaria. DESIGN: A prospective study was performed to evaluate the effects of hypoxia on RK and non-RK corneas. PARTICIPANTS: There were 20 RK and 20 control eyes. INTERVENTION: These eyes were subjected to ocular surface hypoxia using an air-tight goggle system at sea level for 2 hours. MAIN OUTCOME MEASURES: Keratometry, cycloplegic refraction, and pachymetry were evaluated using repeated measures analysis of variance. RESULTS: A significant hyperopic shift (P < 0.0001) and corneal flattening (P < 0.0013) occurred in all subjects with RK compared with those of control subjects. Corneal thickening occurred symmetrically in both groups. CONCLUSIONS: These results suggest that refractive changes in subjects with RK occur at high altitude as a direct result of corneal hypoxia.

Adult↗
PubMed1998

Refractive and visual outcome of hyperopic cataract cases operated on before and after implementation of the Holladay II formula.

OBJECTIVE: The primary objective was to evaluate the refractive and visual outcomes in a series of hyperopic cataract cases in which the Holladay II intraocular lens (IOL) power formula was used in conjunction with added eye measurements (measured anterior chamber depth [ACD], lens thickness, and corneal diameter) to improve predictability of refractive outcome. In addition, the impact of use of a double ("piggyback") IOL on refractive outcome was evaluated. DESIGN: Prospective, nonrandomized comparative clinical trial. PARTICIPANTS: A total of 136 consecutive hyperopic primary cataract-IOL cases operated on at in an outpatient eye surgery center were evaluated. The main inclusion criterion was the requirement of at least 30 D of emmetropia power. INTERVENTION: Implantation of a total implanted power calculated using a newly developed (Holladay II) formula, which uses additional eye measurements (measured ACD, lens thickness, corneal diameter) in addition to the axial length and keratometry normally used, was performed. In the first series, IOL powers were chosen using the Lloyd-Gills formula with modifiers; in the second series, powers were chosen using the Holladay II formula option in the Holladay IOL Consultant software. Selection criteria for both series were the same (requiring at least 30 diopters [D] of power for emmetropia). Keratometry and axial length measurements (by immersion) were taken using the same instrumentation and methodology in both series. Predicted postoperative refraction based on the IOL implanted and the method of power calculation used were computed for each case in both groups and compared to the actual achieved refraction. MAIN OUTCOMES MEASUREMENTS: Main clinical outcome parameters evaluated were the postoperative spherical equivalent (compared with the predicted spherical equivalent) and the best-corrected vision. These outcome parameters were evaluated within each surgical series, in the total group of cases (regardless of power calculation method). Further stratification according to the use of single or double implants also was done. RESULTS: In the group using an older formula system, mean preoperative spherical equivalent of 4.79 D was reduced to -0.67 D. Similarly, in the Holladay II group, the preoperative mean of 5.60 D was reduced to -0.58 D. However, there were fewer large deviations between predicted and achieved spherical equivalent in the Holladay II group as indicated by a smaller standard deviation of the absolute deviation (0.47 vs. 0.59), and the range of postoperative refractions was smaller with fewer large overcorrections or undercorrections. However, almost 90% of both groups were within a diopter of the predicted refraction. Visual results were comparable in the two groups. CONCLUSION: Both IOL calculation systems showed good predictability in these extremely short eyes. The Holladay II formula was simpler because it is incorporated into a user-friendly software package (Holladay IOL Consultant) and required only the input of IOL constants and preoperative measurements with no "fudge factor" modifiers. Results within the series using this formula had a tendency toward a smaller standard deviation with fewer outliers.

Cataract Extraction↗
PubMed2000

A comparison of the rate of refractive growth in pediatric aphakic and pseudophakic eyes.

OBJECTIVE: To compare the rate of refractive growth in pseudophakic children's eyes to that of aphakic eyes. DESIGN: Multicenter, retrospective observational case series. PARTICIPANTS: 83 patients with pseudophakic eyes (100 eyes) and 74 patients with aphakic eyes (106 eyes), with an age of surgery between 3 months and 10 years and a minimum follow-up time of 3 years or more, depending on the age at surgery. METHODS: A logarithmic model was used to analyze the rate of refractive growth for each eye. MAIN OUTCOME MEASURES: Age at surgery, intraocular lens power, intraocular lens A-constant, initial postoperative refraction, final refraction, and final age. RESULTS: Overall, pseudophakic eyes showed a lesser rate of refractive growth than aphakic eyes (-4.6 diopter vs. -5.7 diopter, P = 0.03). This trend was also present but less significant when the eyes were grouped into those less than 6 months of age at surgery (-3.3 diopter vs. -4.6 diopter, P = 0.09) and older patients (-5.0 diopter vs. -6.1 diopter, P = 0.07). However, the mean quantity of myopic shift was greater in pseudophakic eyes than in aphakic eyes (-5.26 diopter vs. -4.54 diopter), despite shorter follow-up times in the pseudophakic eyes. This is due to the optical effects of a constant intraocular lens power in a growing eye. CONCLUSIONS: Pediatric pseudophakic eyes have a slightly lesser rate of refractive growth than aphakic eyes. The new rate values should be used for predicting future refractions in these eyes.

Aphakia, Postcataract↗
PubMed1999

Piggybacking intraocular implants to correct pseudophakic refractive error.

OBJECTIVE: To determine the safety and efficacy of implanting a second intraocular lens (IOL) to correct pseudophakic refractive error. DESIGN: Noncomparative, prospective, consecutive case series. PARTICIPANTS: Eight eyes of eight normal pseudophakes and seven eyes of seven postpenetrating keratoplasty (PK) pseudophakes were included in the study. INTERVENTION: A second intraocular lens (IOL) was implanted anterior to the first in each eye in the study. MAIN OUTCOME MEASURES: Efficacy was determined based on the achieved refractive correction and Snellen uncorrected visual acuity measurements. Safety was determined based on loss of best-corrected visual acuity and operative and postoperative complications. RESULTS: Before surgery, spherical equivalents ranged from -5.12 diopters (D) to 7.5 D, with a mean absolute deviation from emmetropia of 3.38 D (1.62). After surgery, spherical equivalents ranged from -2.75 D to 0.5 D, with a mean absolute deviation from emmetropia of 1.21 D (0.90). Before surgery, only 7% of patients had 20/40 or better uncorrected vision, whereas after surgery, 50% had that level of vision. CONCLUSIONS: Implanting a second IOL is a viable option for correcting pseudophakic refractive error.

Humans↗