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Results for “refractive error”

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At least 703 records · Page 39Linked to original sources
PubMed1996

Videokeratoscopy of recipient peripheral corneas in combined penetrating keratoplasty, cataract extraction, and lens implantation.

PURPOSE: We performed a prospective clinical trial to evaluate computerized videokeratoscopic analysis of the peripheral recipient cornea in intraocular lens power calculations for triple procedures: penetrating keratoplasty, cataract extraction, and intraocular lens insertion. METHODS: Patients with Fuchs' dystrophy underwent consecutive triple procedures. Surgery was performed in 16 eyes by a single surgeon (O.N.S.) using a single technique. If videokeratoscopic analysis disclosed dioptric powers greater than 40 diopters in the circumference of the corneal map, the surgeon's average postoperative central corneal power of 46 diopters was used with the regression formula. If dioptric powers less than 40 diopters were detected in the circumference of the corneal map, 45 diopters was used to avoid postoperative hyperopic shifts and to decrease deviation from intended refractive error. Refraction and videokeratoscopic analysis were performed six months after suture removal (18 to 24 months postoperatively). RESULTS: Analysis of covariance demonstrated that preoperative peripheral videokeratoscopic data of the recipient cornea correlated (P = .0001) with postoperative central corneal power, whereas preoperative central corneal power of the recipient cornea did not correlate (P = .35). Deviation from intended refraction (range, -2.54 to +1.22 diopters) was within 2 diopters in 14 eyes (88%) and within 3 diopters in all eyes. No patients had anisometropia greater than 3 diopters. CONCLUSION: Preoperative data from computerized videokeratoscopic analysis of the recipient peripheral cornea correlated with postoperative central corneal power, and improved postoperative refractive outcomes compared with previously reported results of triple procedures.

Cataract Extraction↗
PubMed1993

Dark focus of accommodation and uncorrected visual acuity.

We compared the dark focus of accommodation in 33 healthy children, 19 eyes with good uncorrected visual acuity (1.0 or more) vs. 14 with poor uncorrected visual acuity (below 1.0). The two groups were matched for age and cycloplegic refractive error. Cycloplegic refractive error ranged from +0.15 to +1.75 D in the good visual acuity group and from +0.25 to +1.87 D in the poor visual acuity group. The dark focus was defined as the difference between the refractive error in the dark and the refractive error under cycloplegia. Initially, visual acuity was measured subjectively. Next, refractive error in the dark was measured using the Nidek Autorefractometer AR1600 with its optical target light off. Refractive error under cycloplegia was measured 40 min after the instillation of cyclopentolate hydrochloride using the same autorefractometer. There was a significant correlation between the dark focus and the cycloplegic refractive error (r = -0.53, p < 0.01). Despite an equal refractive error under cycloplegia the dark focus was significantly larger in the eyes with good uncorrected visual acuity than in those with poor uncorrected visual acuity (p < 0.01). Tonic accommodation may influence uncorrected visual acuity.

Accommodation, Ocular↗
PubMedDate not supplied

Prospective study of photorefractive keratectomy for myopia using the VISX StarS2 excimer laser system.

PURPOSE: To evaluate the safety, efficacy, and predictability of excimer laser photorefractive keratectomy (PRK) for compound myopic astigmatism using the VISX StarS2 excimer laser system with international version 3.1 software. METHODS: We report a prospective consecutive study of myopic excimer laser PRK, performed in a multi-surgeon environment with 200 eyes of 117 patients, to correct naturally occurring compound myopic astigmatism of between -0.50 to -5.90 D manifest refractive sphere and up to -3.50 D manifest refractive astigmatism. Patients were assessed prior to surgery and at 1, 3, 6, and 12 months after treatment. RESULTS: One hundred and ninety-eight of 200 treatments (99%) were reviewed 1 year after surgery; 193 of 198 eyes (97%) achieved 20/40 or better uncorrected visual acuity and 163 of 198 eyes (82%) achieved 20/20 or better. One eye lost two lines of Snellen visual acuity assessed at 12 months but recovered acuity when assessed at 18 months. Mean spherical equivalent corneal plane power was reduced from -3.50 to +0.90 D 1 month after treatment and 0 D at 12 months (SD 0.67 D). Three eyes of three patients underwent further treatment, two with LASIK and one with PRK for residual refractive error. Refractive astigmatism of >1.00 D was reduced from a mean -1.70 to -0.70 D at 1 year after treatment. Vector magnitude was 79% of that intended and mean vector axis error (absolute) was 8.5 degrees. No eye had a severe haze response. Pelli-Robson contrast acuity was significantly reduced after treatment from a mean 1.72 D preoperatively to 1.63 D at 12 months (P<.01). CONCLUSIONS: PRK for myopia using the VISX StarS2 excimer laser system was effective in the treatment of low myopic astigmatism, although there was a significant reduction in Pelli-Robson contrast sensitivity.

Adult↗
PubMed2005

Clinical outcomes of phakic refractive lens in myopic and hyperopic eyes: 1-year results.

PURPOSE: To confirm the safety, efficacy, and predictability of the surgical correction of myopia and hyperopia with the phakic refractive lens (PRL) (Medennium Inc.). SETTING: St. Eriks Eye Hospital, Stockholm, Sweden. METHODS: This was a prospective clinical study of 20 eyes, 14 myopic and 6 hyperopic, that had PRL implantation at St. Eriks Eye Hospital from April to November 2002. Examinations were performed preoperatively and 1 day, 1 week, 3 months, and 1 year postoperatively. Follow-up included evaluation of the PRL rotation with retroillumination photography, evaluation of the distance between the PRL and the crystalline lens with Scheimpflug image, laser flare, endothelial cell count, uncorrected (UCVA) and best corrected (BCVA) visual acuity, residual refractive error, refractive stability, intraocular pressure, and induced cataract. RESULTS: Postoperatively, 11 eyes (55%) gained 1 or more lines, 5 eyes (25%) had no change, and 4 eyes (20%) lost 1 line of BCVA. No eye lost 2 or more lines. Mean UCVA was 0.87+/- 0.29 postoperatively. Laser flare values were highest 1 day after operation with normalization at 3 months and without changes at 1 year (P<.05). A rotation of 10 degrees or more was found in 15 eyes (75%) during the first year. The distance between the PRL and crystalline lens was considerably less at 1 year than at baseline (P<.05). There was no statistically significant endothelial cell loss induced by the PRL (P<.05). No induced cataract, glaucoma, or inflammation was observed. In 1 hyperopic eye, horizontal iris transillumination defects were noticed at 1 year. CONCLUSION: Safety and efficacy indexes were high at 1-year follow-up. The PRL rotated slightly in the posterior chamber. The distance between the PRL and the crystalline lens was considerably less at 1 year than at baseline.

Adult↗
PubMed2003

Asymmetric refraction in an older population: the Blue Mountains Eye Study.

PURPOSE: To describe prevalence and associations of asymmetric refraction in an older population. METHODS: All participants in the Blue Mountains Eye Study had comprehensive eye examinations, including refraction. Spherical equivalent (SEq = sum sphere +.5 cylinder), in diopters, defined refractive error. Refractive asymmetry was assessed in phakic participants; anisometropia was defined as > or =1.0 diopters SEq difference between eyes. RESULTS: Anisometropia was present in 14.7% of participants. Mean refractive asymmetry (in diopters) in persons aged <60 years was 0.43; 60 to 69 years, 0.51; 70 to 79 years, 0.72; and 80+ years, 0.88. Prevalence and severity of anisometropia increased with age (P <.001), increasing ametropia or astigmatism. Associations included older age, cataract, and increasing ametropia. Myopic participants >-3.0 diopters had the highest anisometropia prevalence. CONCLUSIONS: Refractive asymmetry was associated with age, increasing ametropia, and cataract.

Aged↗
PubMed1991

Reappraisal of the ratio of disc to macula/disc diameter in optic nerve hypoplasia.

The ratio of disc to macula/disc diameter is characteristically increased in eyes with optic nerve hypoplasia. We present the largest reported series of patients with a definitive diagnosis of optic nerve hypoplasia for whom this ratio has been determined. All measurements were made by an independent masked observer. Our results are in accordance with previous reports. A ratio of 2.94 provides a one-tailed upper population limit of 95%. An attempt has been made to correlate optic disc size and visual acuity. In 75% of bilateral cases the eye with the relatively smaller optic disc was found to have a better Snellen visual acuity than the fellow eye. This suggests that additional pathogenic mechanism(s) may have determined the eventual visual outcome in such eyes. Such mechanisms include macular hypoplasia, high refractive error, refractive amblyopia, central scotoma, and optic atrophy.

Adolescent↗
PubMedDate not supplied

Excimer laser in situ keratomileusis for myopia.

PURPOSE: To evaluate the efficacy, safety, and predictability of excimer laser in situ keratomileusis (LASIK) for the correction of myopia. METHODS: Forty-six consecutive eyes that had LASIK with the VISX 20/20B laser and Chiron corneal shaper were evaluated. Mean spherical equivalent of the preoperative manifest refraction was -9.40 +/- 3.78 diopters (D) (range, -3.50 to -19.75 D). The refractive effect (postoperative refraction minus baseline refraction), residual refractive error (refractive effect minus planned correction) and uncorrected and spectacle-corrected visual acuity were examined. RESULTS: Mean follow-up was 6.1 months (range, 3 to 9 mo). Spectacle-corrected visual acuity was unchanged in 39 eyes (84.78%), significantly improved in five eyes (10.86%), and worse in two eyes (4.34%). Uncorrected visual acuity was 20/20 or better in 15 eyes (32.6%) and 20/40 or better in 39 eyes (84.78%). Thirteen eyes (28.26%) had a postoperative spherical equivalent refraction within +/- 0.50 D and 36 eyes (78.26%) within +/- 1.00 D of attempted correction. No intraoperative complication occurred. Postoperative complications were few and not severe: three eyes (6.52%) developed regular astigmatism, two eyes (4.34%) had interface deposits, and three eyes (6.52%) had small epithelial cysts in the interface. CONCLUSION: LASIK with the VISX 20/20B laser is safe, moderately effective, and relatively predictable for correcting myopia from -3.50 to -19.50 D. Predictability decreases with increasing myopia.

Adult↗
PubMed2003

The expandability of the eye in childhood myopia.

PURPOSE: While intraocular pressure has been shown to have some influence on eye growth, the stress exerted on the outer wall of the eye and the rigidity of the outer coats of the eye may be of greater importance. No studies have assessed the significance of both of these variables in terms of childhood myopia and its progression. METHODS: Twenty myopic and twenty non-myopic children aged 8 to 12 years participated in the study. Refractive error (including refractive error shift over the past year), ocular dimensions (anterior chamber, lens thickness, vitreous chamber, axial length), intraocular pressure, equatorial scleral rigidity, and outer wall thickness were measured for right eyes. Outer wall stress was calculated using the approximation, p = IOP*r/2t. RESULTS: The myopic group was 3.43 D more myopic and had 1.43 mm longer eyes on average than the non-myopic group. The myopic children had experienced a mean refractive shift of -0.30 D/yr over the past year. Equatorial wall thickness was significantly less in myopes than non-myopes (difference of 0.09 mm, p = 0.02) and in the combined sample was correlated to refractive error (r = 0.312, p = 0.05), but not refractive error shift. Ocular rigidity and eye wall stress values were similar in the two groups. The refractive shift increased as wall stress increased both in the combined sample (r = -0.386, n = 35, p = 0.022) and the myopic group (r = -0.600, n = 16, p = 0.014). CONCLUSION: We did not find large differences in wall thickness, ocular rigidity, or wall stress in myopic and non-myopic children. While reduced ocular rigidity, increased wall stress and scleral thinning may have a role in myopia progression in childhood we were not able to clearly show this in our study of 40 children.

Child↗