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At least 271 records · Page 15Linked to original sources
PubMed2003

Anterior corneal optical aberrations induced by laser in situ keratomileusis for hyperopia.

PURPOSE: To evaluate the effects of hyperopic laser in situ keratomileusis (LASIK) on anterior corneal higher-order aberrations (HOAs) (3rd to 6th orders). SETTING: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. METHODS: In a retrospective study, 3rd-order to 6th-order HOAs from preoperative and 3-month postoperative corneal topographic maps of eyes that had hyperopic LASIK using the Visx Star S2 and Visx Star S3 laser systems were calculated. There were 20 eyes of 14 patients in each group; the optical and transition zones were 6.0 mm and 9.0 mm, respectively. The surgically induced changes in anterior corneal HOAs and the differences between the HOA changes in corneas treated with and without active eye tracking were analyzed. RESULTS: In both groups, hyperopic LASIK induced a significant reduction in 4th-order spherical aberration (SA) coefficients (Z4(0)) in the 3.0 mm and the 6.0 mm central zones, and the decrease was significantly correlated with increasing hyperopic correction (except in the Visx S3 group's central 3.0 mm zone). In the 6.0 mm zone in both groups, the root-mean-square (RMS) of the SA (Z4(0) and Z6(0)) decreased significantly, whereas there were no significant changes in the total HOAs. By excluding Z4(0), the mean RMS values for the remaining 21 Zernike terms increased by more than 30% (both P<.016). A simulated increase in pupil size from 3.0 to 6.0 mm caused a significantly smaller increase in SA in postoperative corneas compared to the preoperative values. Differences between the S2 and S3 groups were minimal. CONCLUSIONS: Hyperopic LASIK decreased SAs and reduced the magnitude of the SA increase that occurred with pupil dilation. Higher-order aberrations excluding the 4th-order SA increased significantly.

Corneal Diseases↗
PubMed1994

Photorefractive keratectomy to correct astigmatism with myopia or hyperopia.

Excimer laser photorefractive keratectomy as a means to flatten the central cornea has generated considerable interest. With this technique radial symmetric ablations can be performed to correct myopic refractive errors and excise superficial corneal pathology. We developed a technique that uses toric ablation to correct astigmatism. A new mask was designed for the MEL 60 Aesculap-Meditec excimer laser. The mask can be rotated regularly over 360 degrees. By varying the angular distances, the surgeon can increase ablation depth in any desired meridian. As a result, both cylindrical and spherical errors can be corrected in one procedure. Seventy-three eyes with either simple, myopic, mixed, or irregular astigmatism were treated. In each category of astigmatism, the surgery reduced the spherical component as well as the overall mean preoperative cylindrical refraction. Our findings suggest that this technique is a safe and effective procedure for correcting different types of astigmatism.

Adolescent↗
PubMed1996

Implantation of multiple foldable acrylic posterior chamber lenses in the capsular bag for high hyperopia.

This case series describes the implantation of multiple acrylic intraocular lenses (IOLs) in the capsular bag of six eyes of three highly hyperopic patients (spherical equivalent +5.75 to +8.62) during cataract surgery. Two foldable acrylic lenses were placed in the capsular bag of each eye. Preoperative best corrected visual acuity (BCVA) ranged from 20/50 to 20/300. Postoperative uncorrected visual acuity ranged from 20/25 to 20/60, while BCVA ranged from 20/25 to 20/40. Multiple acrylic lenses were used successfully in cases in which a single IOL would have given inadequate correction.

Acrylates↗
PubMedDate not supplied

Corneal perforation and decompensation after automated lamellar keratoplasty for hyperopia.

We describe a case of corneal perforation and decompensation after automated lamellar keratoplasty (ALK) in a middle-aged hyperopic man who had had unsuccessful holmium laser thermokeratoplasty. The corneal decompensation responded to gluing and application of a bandage contact lens but despite treatment, the corneal flap remained precariously poised with a localized area of thinning that is predisposed to future perforation and decompensation. This case highlights the potential for serious complications and subsequent visual morbidity after ALK.

Automation↗
PubMed1998

Excimer laser treatment of hyperopia.

PURPOSE: The aim of this study was to analyse the clinical results of hyperopic photorefractive keratectomy treatments and to compare the results achieved with the usage of different masks. METHOD: 20 eyes of 16 hyperopic patients were treated, using the Aesculap-Meditec MEL60 193nm ArF excimer laser. The mean duration of follow-up was 9.9+/-3.4 months. Statistical comparison of the results with the two masks was made using the unpaired Student t-test. RESULTS: Preoperative mean spherical equivalent was +4.23+/-1.18D, which changed to +0.20+/-0.78D at one month and regressed to +1.23+/-1.27D at the last control examination. After 6 months 60% (12 eyes) had spherical equivalent within +/-1.0D of the attempted correction. The statistical analysis showed no significant difference between the results with the two masks. CONCLUSION: Good preparation for the treatment is of equal importance for the results of the photorefractive keratectomy as compared to the technical circumstances.

Adult↗
PubMed1996

[Early correction of hyperopia and astigmatism in children leads to better development of visual acuity].

BACKGROUND: From the investigations of Wiesel and Hubel an influence of early spectacle correction of refractive errors on visual development is to be expected. Nevertheless the benefit of early spectacle correction in young children is being discussed controversially. PATIENTS AND METHODS: In a retrospective study the records of 103 strabismic children were analyzed. Myopic children and those with hypermetropia less than 2.0 diopters without astigmatism were excluded from this study. Visual acuity of the dominant eye only was compared between the following subgroups: early spectacle correction (A) not later than at the age of 30 months; "early" spectacle correction (B) between 30 months and 4 years; late spectacle correction (S) after the age of 8 years. In further subgroups we analyzed hypermetropia of more than 3.0 diopters and the combination of hypermetropia and astigmatism of 1.0 diopter or more. Visual acuity was determined using commercially available target projectors 2 times with an interval of at least 3 months. For analysis, the mean of these two examinations was calculated. In all children visual acuity after the age of 8 years was analyzed, the children of group S wore their glasses at least 6 months before the first determination of visual acuity included in this study. The dominant eye was analyzed only. RESULTS: Early corrected eyes developed better visual acuity than late corrected ones: 45% of the early corrected children (A + B) had a visual acuity exceeding 1.0 (20/20) versus 22% in the late corrected (S) subgroup (p = 0.046). 53% of the children corrected within the first 30 months (A) developed a visual acuity exceeding 1.0 (20/20) compared with 22% in the late corrected subgroup (p = 0.019). In hypermetropia exceeding 3.0 diopters (without astigmatism) the difference of early correction (A + B) compared with late correction (S) was even more significant: 72% of early corrected children developed a visual acuity of better than 1.0 (20/20), but no child corrected late did so (p = 0.0015). On the other hand, no child in these 2 subgroups developed a visual acuity of below 1.0 (20/20). Astigmatic eyes had a worse visual acuity: 13% of the early corrected subgroup (A) developed a visual acuity below 1.0 (20/20) versus 55% in the late corrected (S) subgroup (p = 0.024). CONCLUSION: Early correction of hypermetropia (3.0 diopters or more) and of hypermetropic astigmatism (1.0 diopter or more) results in better development of visual acuity as measured at the age of 8 years or later. Since visual acuity of better than 1.0 (20/20) is "normal", late corrected children often did not develop "normal", visual acuity. By early correction of relevant hypermetropia and hypermetropic astigmatism this "refractive amblyopia" at least in part could be avoided.

Astigmatism↗