Showing papers on "Refractive error published in 1994"
Journal Article•
TL;DR: Cross-sectional data indicate age-related differences in refractive status in an adult population and suggest that education is associated with myopia independent of age.
Abstract: PURPOSE: To describe the prevalence of refractive errors in a population of adult Americans. METHODS: From 1988 to 1990, 4926 adults who were 43 to 84 years of age and living in Beaver Dam, Wisconsin at the time of the 1987-1988 census were examined. Refractions were performed according to a modification of the Early Treatment Diabetic Retinopathy Study protocol. Included in this study were 4533 people who had not undergone cataract surgery and who had a best corrected visual acuity better than 20/40 in at least one eye. Myopia was defined as a refractive error less than -0.50 diopters; hyperopia was defined as a refractive error greater than +0.50 diopters. RESULTS: Hyperopia was more frequent than myopia in the study group (age-adjusted of 49.0% and 26.2% in right eyes, respectively, P = 0.0001). The prevalence of hyperopia in the right eye increased with increasing age from 22.1% in those 43 to 54 years of age to 68.5% in those 75 years of age or older. The prevalence of myopia in the right eye decreased from 43.0% in those 43 to 54 years of age to 14.4% in those 75 years of age or older. There was significant relationship between education level and refractive error (age adjusted r = -0.32, P = 0.0001). Neither household income nor occupation was associated with refractive error in our data. CONCLUSION: These cross-sectional data indicate age-related differences in refractive status in an adult population and suggest that education is associated with myopia independent of age.
415 citations
TL;DR: LASIK, although more complicated because of the use of a microkeratome, was more effective than photorefractive keratectomy in higher myopes, and LASIK created less corneal haze.
Abstract: Background The purpose of this research was to study the visual outcome of excimer laser photorefractive keratectomy and laser in situ keratomileusis (LASIK) for the correction of moderate and high myopia. Methods Twenty partially-sighted eyes of 20 patients were divided into two groups, LASIK and photorefractive keratectomy. Ten eyes underwent LASIK and the other 10 photorefractive keratectomy. Follow up was at 1, 3, 6, and 12 months. The LASIK technique included a nasally based, 150 microns thick, 8.0 x 9.0 mm diameter, truncated, disc-shaped corneal flap created with a microkeratome; and the ablation of the stroma with a 193-nanometer ArF excimer laser. The flap was returned to its original position and held in place by apposition. The photorefractive keratectomy technique included mechanical removal of the epithelium and ablation of the stroma with a 193-nanometer ArF excimer laser. Results LASIK series: One eye had a ruptured globe during the second postoperative month and was excluded from the study. The preoperative spherical equivalent refraction ranged from -10.62 to -25.87 diopters (D). The attempted correction ranged from -8.00 to -16.00 D. Postoperative refraction and corneal topography stabilized between 4 and 12 weeks. Spectacle-corrected visual acuity was within 1 Snellen line of preoperative in all eyes. The refraction in six eyes (66.6%) was within +/- 1.00 D of the intended correction, and in eight eyes was within +/- 2.00 D (88.8%) at 12 months. The mean attempted correction (11.40 +/- 2.60 D) was close to the mean achieved correction at 12 months (11.96 +/- 3.10 D). The mean postoperative refractive astigmatism (1.50 +/- 0.97; range, 0.25 to 3.50 D) was close to the preoperative astigmatism (1.70 +/- 1.15; range, 0 to 3.75 D). Endothelial cell density at 12 months showed an average 8.67% of cell loss. All eyes showed a clear interface. Photorefractive keratectomy series: The preoperative spherical equivalent refraction ranged from -10.75 to -23.12 D. The attempted correction ranged from -8.80 to -17.60 D. Postoperative refraction showed regression throughout the follow-up period, and corneal topography did not stabilize. Spectacle-corrected visual acuity was within 1 Snellen line in eight eyes. Two eyes lost 2 and 3 Snellen lines. One eye was within +/- 1.00 D, and three eyes (30%) were within +/- 2.00 D of the intended correction at 12 months. The achieved correction mean (7.17 +/- 5.29 D) was 61% of the attempted mean (11.72 +/- 2.81 D) at 12 months. The postoperative refractive astigmatism (1.80 +/- 0.95; range, 0.50 to 4.00 D) was very close to the preoperative (1.90 +/- 1.33; range, 0 to 5.00 D). Endothelial cell density showed an average of 10.56% cell loss at 12 months. The mean haze at 12 months was 1.2 (0 to 4 scale). Conclusion LASIK, although more complicated because of the use of a microkeratome, was more effective than photorefractive keratectomy in higher myopes. LASIK created less corneal haze. The refraction was more stable with LASIK in the correction of high myopia. Its predictability was three times that of PRK.
415 citations
TL;DR: In this article, the long-term effects and stability of refraction following a standardized technique of radial keratotomy for myopia in the nine-center Prospective Evaluation of Radial Keratotomy (PERK) study 10 years after surgery were evaluated.
Abstract: Objective: To determine the long-term effects and stability of refraction following a standardized technique of radial keratotomy for myopia in the nine-center Prospective Evaluation of Radial Keratotomy (PERK) Study 10 years after surgery. Methods: Radial keratotomy using eight centripetal incisions was performed to reduce myopia of -2.00 to -8.75 diopters in 1982 and 1983. A mean of 10 years later, patients underwent a standardized ophthalmic examination similar to previous study examinations. Results: Of 427 patients (793 eyes that underwent radial keratotomy), 374 patients (88%) (693 eyes) returned for the 10-year examination. Of 675 eyes with refractive data, 38% had a refractive error within 0.50 D and 60% within 1.00 D. For 310 first-operated eyes, the mean refractive error was -0.36 D at 6 months and changed in a hyperopic direction to +0.51 D at 10 years. The average rate of change was +0.21 D/y between 6 months and 2 years and +0.06 D/y between 2 and 10 years. Between 6 months and 10 years, the refractive error of 43% of eyes changed in the hyperopic direction by 1.00 D or more. The hyperopic shift was statistically associated with the diameter of the clear zone. Uncorrected visual acuity was 20/20 or better in 53% of 681 eyes and 20/40 or better in 85%. Loss of spectaclecorrected visual acuity of 2 lines or more on a Snellen chart occurred in 3% of all 793 eyes that underwent surgery. Among 310 patients with bilateral radial keratotomy, 70% reported not wearing spectacles or contact lenses for distance vision at 10 years. Conclusion: The PERK technique of radial keratotomy eliminated distance optical correction in 70% of patients, with a reasonable level of safety. A shift of the refractive error in the hyperopic direction continued during the entire 10 years after surgery.
312 citations
TL;DR: The results suggest that the premyopic eye in children with a family history of myopia already resembles the elongated eye present in myopia.
Abstract: Objective. —To evaluate whether eye size and shape are different in children based on their parental history of myopia. Design. —A community-based cohort study of schoolchildren (aged 6 to 14 years), the Orinda (Calif) Longitudinal Study of Myopia. Setting. —Four campuses of the Orinda Union School District, a predominantly white, high socioeconomic status community. Participants. —A cross-sectional volunteer sample of 716 children (662 non-myopic) in the first, third, and sixth grades in 1989,1990, and 1991. All children in those grades were eligible for inclusion in the study. Intervention(s). —None. Main Outcome Measures. —Refractive error (measured by autorefraction), corneal curvature (measured by photokeratoscopy), crystalline lens power (measured by video phakometry), and axial ocular dimensions (measured by ultrasonography). Results. —With prevalent cases of myopia excluded and grade in school and "near work" controlled for, children with two myopic parents had longer eyes and less hyperopic refractive error (analysis of covariance, P ≤.01) than children with only one myopic parent or no myopic parents. A model incorporating parental history is only improved by the addition of near work for the prediction of refractive error. Conclusions. —Even before the onset of juvenile myopia, children of myopic parents have longer eyes. These results suggest that the premyopic eye in children with a family history of myopia already resembles the elongated eye present in myopia. ( JAMA . 1994;271:1323-1327)
298 citations
TL;DR: Except in corrections greater than 6 diopters, complications after PRK are rare and assuming an appropriate patient selection, PRK may be considered a relatively safe procedure compared with other refractive procedures.
294 citations
TL;DR: The overall efficacy and safety of procedures such as radial keratotomy and photorefractive keratectomy likely will be improved once the unpredictable variables of contact lens-induced warpage and occult ectatic disease are eliminated by topographic screening before surgery.
201 citations
TL;DR: Refraction after PRK is slow to stabilize, but appears to reach stability by 18 to 24 months after surgery, and the refractive results are reasonably predictable and compare well with those achieved with radial keratotomy.
170 citations
TL;DR: The recovery data suggests that monkeys have an emmetropization mechanism which is sensitive to optical defocus, but the failure of this mechanism to compensate for the refractive errors simulated during the lens-rearing procedures suggests that this mechanism has a limited operating range.
123 citations
Journal Article•
TL;DR: Although tropicamide, as expected, showed poorer cycloplegia compared to cyclopentolate, the degree of difference appeared to be small, with minimal effect on the measurement of distance refractive error and the ocular optical components.
Abstract: Purpose. The purpose of this study was to examine the effect of cycloplegic agent on the measurement, of refractive error and the ocular components. Methods. We compared two commonly used topical cycloplegic agents, 1 % tropicamide and 1 % cyclopentolatc, for their effect on the measurement of refractive error (by Canon R-l autorefraction), accommodative response (by Canon R-l autorefraction and by the conventional, subjective "pushup" method), crystalline lens power (by video phakometry and by calculation), and axial ocular dimensions (by A-scan ultrasonography) in 20 emmetropic to moderately hyperopic children. Results. Comparison of refractive error at each drug's reported time of maximum cycloplegia (30 minutes for tropicamide and (50 minutes for cyclopentolate) showed that distance autorefraction in the vertical meridian differed by +0.20 ± 0.30 diopters (D) (P = 0.008). The average difference was +0.07 ±0.10 mm for anterior chamber depth (P = 0.004), —0.03 ± 0.05 mm for crystalline lens thickness (P = 0.025), —0.65 ± 0.(39 D for phakometrically measured crystalline lens power (P < 0.001), +0.03 ± 1.55 D for calculated crystalline lens power (P = 0.94), and -0.09 ± 0.19 mm for vitreous chamber depth (P = 0.062, all paired / tests; positive signs denote greater values with cyclopentolate). Residual accommodation was 0.4 7 and 0.67 D greater with tropicamide when measured by autorefraction and the pushup method (/-" = 0.013 and 0.08 respectively, paired / test). All significant differences were consistently in the direction of poorer cycloplegia with tropicamide. Conclusions. Although tropicamide, as expected, showed poorer cycloplegia compared to cyclopentolate, the degree of difference appeared to be small, with minimal effect on the measurement of distance refractive error and the ocular optical components. Invest Ophthalmol VisSci. 1994 ;35:515-527. v^linicians' use of cycloplegic agents to determine the "true" manifest refractive error is widespread, especially in infants and children. Pharmaceutical paralysis of accommodation is often necessary to relax the habitual accommodative posture in young hyperopes. However, the amount of cycloplegia required to accomplish this has been debated in the literature for many years. The belief that more cycloplegia is necessarily better has led to severe and inconvenient procedures,
116 citations
TL;DR: The age of onset of posterior vitreous detachment was studied in 930 eyes with a clearly defined onset time and no vitreoretinal diseases except refractive error or equatorial degeneration and a positive correlation between onset age of PVD andRefractive error was found.
Abstract: The age of onset of posterior vitreous detachment (PVD) was studied in 930 eyes with a clearly defined onset time and no vitreoretinal diseases except refractive error or equatorial degeneration. We found a positive correlation between onset age of PVD and refractive error, with the regression line y = 0.91 x + 60.93 (y onset age, x diopter of refractive error). The higher the degree of myopia, the younger the onset age of PVD. Comparing onset ages for 240 eyes from males and 690 eyes from females, there was a possible tendency toward a lower PVD onset age for females. There was no significant difference in onset age between 112 eyes with and 818 eyes without equatorial degeneration of the retina.
109 citations
TL;DR: In chickens, 6-hydroxy dopamine suppresses deprivation-induced myopia but has no effect on the magnitude of changes in axial eye elongation that are induced by spectacle lenses, suggesting that two pharmacologically different feedback loops may be responsible for deprivation myopia and lens-induced refractive errors.
TL;DR: In this paper, the results of 139 consecutive eyes that had photoastigmatic refractive keratectomy (PARK) for myopic astigmatism (myopia < or = -15.00 D) were compared with 107 consecutive and concurrent eyes that received photorefractive Keratectoma (PRK), and the results showed that PARK achieved a 20/40 or better visual acuity than PRK.
Abstract: The excimer laser allows the controlled ablation of corneal tissue to correct refractive error. By using a combination of spherical and slit apertures, it is possible to correct both myopia and astigmatism. We report the results of 139 consecutive eyes that had photoastigmatic refractive keratectomy (PARK) for myopic astigmatism (myopia < or = -15.00 diopters [D] with astigmatism < or = -6.00 D) and compare these results with 107 consecutive and concurrent eyes that received photorefractive keratectomy (PRK) for myopia (< or = -15.00 D). The same excimer laser was used by 27 different surgeons. All patients were followed for at least three months. In the PARK group, 68% were within +/- 1.00 D at six months and 77% were within +/- 2.00 D. In the PARK group, these figures were 87% and 97%, respectively. Uncorrected visual acuity of 20/40 or better was achieved in 72% of PARK and 90% of PRK patients at six months. Minor adverse reactions occurred in 6% of PARK and 11% of PRK patients. No significant surgeon effect was seen. Photoastigmatic refractive keratectomy provides a realistic approach to the surgical correction of myopic astigmatism and is comparable to PRK in safety and efficacy.
TL;DR: During the 20‐month mean follow-up, no retinal detachment or cystoid macular edema was observed and Posterior capsule opacification was the major complication and it developed faster than reported in other studies.
Abstract: The results of clear lens extraction and posterior chamber intraocular lens implantation in 31 eyes with high myopia and six eyes with high hyperopia were reviewed. In the myopic group, 77% of eyes achieved 20/40 or better uncorrected postoperative visual acuity and 97% achieved 20/40 or better corrected acuity. Sixty-eight percent of eyes were within 1.0 diopter (D) of emmetropia and 90% were within 2.0 D. Astigmatic keratotomy (four eyes) and radial keratotomy (one eye) were performed for postoperative refractive errors. Intraocular lens exchange was necessary to correct power in one case. In the hyperopic group, all six eyes achieved 20/40 or better uncorrected postoperative visual acuity and all were within 1.0 D of emmetropia. During the 20-month mean follow-up, no retinal detachment or cystoid macular edema was observed. Posterior capsule opacification was the major complication and it developed faster than reported in other studies.
TL;DR: Photorefractive keratectomy with the 193-nm excimer laser appears to be a useful treatment modality for the reduction of mild to moderate myopia.
TL;DR: A technique that uses toric ablation to correct astigmatism is developed that reduces the spherical component as well as the overall mean preoperative cylindrical refraction and suggests that this technique is a safe and effective procedure for correcting different types ofAstigmatism.
Abstract: 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.
TL;DR: Visual rehabilitation with decreased postkeratoplasty astigmatism and more regular corneal topography was attained more rapidly and safely with intraoperative suture adjustment.
TL;DR: IOL decentration and/or tilt increase myopia and astigmatism, but could be sources of substantial postoperative refractive errors if the decentration or tile is large.
Abstract: Background Intraocular lens (IOL) decentration and tilt may affect postoperative refractive errors through spherical aberration of the IOL. Methods Through a use of a ray-tracing program and by minimizing algorithm, we calculated theoretical refractive errors for various degrees of IOL decentration and tilt. We compared our results with those obtained by paraxial vergence calculations. Results IOL decentration and/or tilt shifted postoperative refractive errors toward myopia and astigmatism of oblique origin. For example, a 3-millimeter decentration of an IOL resulted in induction of approximately -2.00 diopters (D) sphere and +0.70 D cylinder. IOL tilt affected refractive errors to a lesser degree. The change in refractive error caused by a combination of IOL decentration and tilt depended on the relationship between the geometrical axes of decentration and tilt. In the case of the least favorable combination of 12 degrees of tilt and 3 mm of decentration, it can reach -7.00 D sphere and +4.00 D cylinder. Conclusions IOL decentration and/or tilt increase myopia and astigmatism. They are negligible for small decentrations, but could be sources of substantial postoperative refractive errors if the decentration or tile is large.
TL;DR: A high correlation between preoperative and 12‐month postoperative height and time shift of keratometric values was found, and immediately after surgery there was an axis change; a decrease of with‐the‐rule astigmatism occurred concurrently with an increase toward oblique and against‐the-ruleAstigmatism.
Abstract: We studied postoperative astigmatism in 107 patients who were followed for 12 months after phacoemulsification and posterior chamber lens implantation. A scleral incision of 3.5 mm was used in Group A patients and one of 4.5 mm in Group B patients. In both groups a no-stitch wound closure technique was used. A high correlation between preoperative and 12-month postoperative height and time shift of keratometric values was found. In both groups the mean difference was less than 0.60 diopters (D). The mean postoperative cylinder increase was less than 0.50 D; it was less than 0.25 D after six months. The induced astigmatism was confirmed by three different methods. Immediately after surgery, a negative induced astigmatism was found in both groups. After 12 months, induced astigmatism in Group A was -0.37 D and in Group B, -0.67 D. Immediately after surgery there was an axis change; a decrease of with-the-rule astigmatism occurred concurrently with an increase toward oblique and against-the-rule astigmatism. This axis change was somewhat evident after 12 months.
TL;DR: The hypothesis that age-related changes in lens fiber cytoskeleton and membranes are responsible for the change in elastic properties of lens matter and thus contribute to presbyopia is supported.
Abstract: The elastic properties of lens matter change with age and this contributes to presbyopia. The changes in elasticity of lens matter could be the result of a change in water and soluble proteins (1) or a change in lens fiber cytoskeleton and membranes (2). If it is caused by (1) then the velocity of sound in the lens should change with age. If it is caused by (2) the velocity of sound in the lens will not change. Using the technique of continuous ultrasonographic biometry, the velocity of sound in clear lenses was measured in vivo in a group of 24 healthy subjects aged 15 to 45 years with a visual acuity of 6/6 or better. In this group maximum accommodative amplitude decreased with age. It was found that, despite the occurrence of presbyopia, the velocity of sound did not change with age. Our results support the hypothesis that age-related changes in lens fiber cytoskeleton and membranes are responsible for the change in elastic properties of lens matter and thus contribute to presbyopia.
TL;DR: It is tentatively concluded that the corneal transplant reacts to photorefractive keratectomy in much the same way as a normal cornea, and was unable to prevent the recurrence of granular dystrophy in the transplanted tissue.
Abstract: We present 3 eyes that underwent photorefractive keratectomy (PRK) for residual myopia after penetrating keratoplasty, and 1 eye that was treated for recurrent granular dystrophy and myopia following penetrating keratoplasty. The 3 refractive eyes experienced improvements in visual acuity and refractive error through 3 months postoperative, but exhibited regression of effect after 6 months postoperative. One eye also exhibited substantial corneal haze at three months postoperative that was not responsive to steroid retreatment. The eye with granular dystrophy obtained symptomatic relief as well as improvement in vision. We tentatively conclude that the corneal transplant reacts to photorefractive keratectomy in much the same way as a normal cornea. Eyes with substantial degrees of post-graft myopia exhibit regression of refractive effect, much like high myopes following primary photorefractive keratectomy. Photorefractive was unable to prevent the recurrence of granular dystrophy in the transplanted tissue. The eyes reported here achieved only modest long-term visual and refractive improvements.
TL;DR: Preliminary results suggest that intraocular lens (IOL) implantation may be a safe and effective method of optical correction for children with traumatic cataracts.
Abstract: Purpose: The purpose of this prospective study is to evaluate the postoperative visual acuity, refractive error, intraocular pressure, and status of the posterior capsule in children with traumatic cataracts who undergo extracapsular cataract extraction and insertion of a posterior chamber lens. Methods: Extracapsular cataract extraction and primary endocapsular fixation of a posterior chamber lens implant were performed in eight children (age range, 4–17 years) with unilateral traumatic cataracts. Results: There were no intraoperative complications, and seven of eight eyes achieved 20/40 or greater spectacle visual acuity during an average follow-up interval of 10 months (range, 5–20 months). The average postoperative spherical equivalent refractive error was +0.33 diopter (D) (range, −2.25 to +2.12 D); the average postoperative anisometropia was approximately 1 D (range, 0–2.25 D). In one patient, a coagulase-negative staphylococcal endophthalmitis developed 10 days after surgery. In three eyes that had opacified posterior capsules, YAG laser capsulotomy was performed. Conclusions: These preliminary results suggest that intraocular lens (IOL) implantation may be a safe and effective method of optical correction for children with traumatic cataracts.
TL;DR: The authors measured the effect of direction of eye gaze and head posture on amplitude of accommodation for two age groups, a young group aged 18 to 25 years and an older group aged 35 to 45 years.
Abstract: One of the theories of the mechanism of presbyopia is the Hess-Gullstrand theory. This theory predicts that amplitude of accommodation should increase in downgaze because of movement of the lens under the influence of gravity, and that this should be more marked for older than for younger subjects. We assessed this theory by measuring the effect of direction of eye gaze and head posture on amplitude of accommodation for two age groups. Farpoints, nearpoints, and amplitude of accommodation were determined for two subject groups, a young group aged 18 to 25 years and an older group aged 35 to 45 years. Small but significant shifts of nearpoints toward the eye were observed when head position or eye gaze was shifted from above to below the horizontal, for the younger observers only (the maximum mean difference between conditions was 1.1 D, compared with a mean accommodation level of 9.8 D for this young group). Previous studies by others found changes in the same direction for eye gaze and head position, respectively, but our changes were much smaller. We do not believe that particular care is needed in selection of head position and eye gaze during clinical measurements of the amplitude of accommodation. Because the shift of the nearpoint was noted only for the younger group, this study does not support the Hess-Gullstrand theory of presbyopia.
TL;DR: The ability to function without lenses increased substantially only when patients had an uncorrected visual acuity of 20/20 or better in at least one eye, and a refractive error within +/- 0.50 D were insensitive criteria for evaluating distance spectacle independence.
TL;DR: Overall, astigmatism improved 55.6%.
Abstract: Using a 193 nm excimer laser, we performed elliptical astigmatic and spherical corneal ablation on 168 eyes with compound myopic astigmatism and analyzed the three- and six-month postoperative results. Mean preoperative astigmatism was 1.51 +/- 0.81 diopters (D). Mean three- and six-month postoperative astigmatism was 0.70 +/- 0.58 D and 0.67 +/- 0.60 D, respectively. Six months after surgery, eyes with less than 1.00 D preoperative astigmatism improved 4.8%. The improvement was 53.5% and 59.1% for eyes with a preoperative astigmatism of 1.00 D to 2.00 D and above 3.00 D, respectively. Overall, astigmatism improved 55.6%. There was a wide distribution from overcorrection to undercorrection. Astigmatism six months after surgery was within 10 degrees of the preoperative axis in 46.1% of eyes.
TL;DR: Cyclopentolate 1% requires more time to produce mydriasis and cycloplegia in eyes with heavily pigmented irides; however, its final effect on refractive error is apparently independent of iris pigmentation and depends on the amount of sphericalRefractive error present.
Abstract: Twenty-seven Hong Kong Chinese children, aged 3 to 5½ years, were recruited in this study to evaluate the relation between refractive error as measured retinoscopically before and after cycloplegia using cyclopentolate 1%. The noncycloplegic spherical refractive error of these children ranged from -0.75 to +2.50 D and approximately 98% of the Hong Kong pre-school children have a manifest spherical error within this range. The cycloplegic refractive error can be approximated by multiplying the spherical component of the manifest error by 1.45 and adding +0.39 D to the product, while keeping the astigmatic power and axis unchanged. Cyclopentolate 1% requires more time to produce mydriasis and cycloplegia in eyes with heavily pigmented irides; however, its final effect on refractive error is apparently independent of iris pigmentation and depends on the amount of spherical refractive error present.
TL;DR: It is demonstrated that the excimer laser can be used to treat myopic astigmatism successfully and none of the patients had a clinically significant loss of best corrected acuity.
Abstract: In this paper, we examine the 193 nm excimer laser's efficacy and safety in treating myopic astigmatism. The VISX Twenty/Twenty excimer laser uses aperture elements to effect astigmatic photorefractive keratectomy. In 70 patients with six months follow-up, the average postoperative sphere was -0.14 and the average postoperative cylinder was -0.54. Seventy-one percent of these patients had uncorrected visual acuity of 20/40 or better at six months. In 12 patients with one year follow-up, the average postoperative sphere was -0.05 and the average postoperative cylinder was -0.59. Eighty-three percent of these patients had uncorrected acuities of 20/40 or better; none had a clinically significant loss of best corrected acuity. This investigation demonstrates that the excimer laser can be used to treat myopic astigmatism successfully.
TL;DR: A retrospective study involving 47 lids in 26 patients was conducted to determine changes in refraction and keratometry after surgery for acquired ptosis; the cylindrical axis and the axis of toricity remained relatively stable after surgery.
Abstract: A retrospective study involving 47 lids in 26 patients was conducted to determine changes in refraction and keratometry after surgery for acquired ptosis. Refractive and keratometric data were obtained prior to and 6 months after levator surgery. Data were analyzed for changes in refractive sphere, cylinder, and cylindrical axis, as well as keratometry, toricity, and axis of toricity. Although patients noted subjective change in vision postoperatively and demonstrated changes in their refractive error, the changes were statistically insignificant. Consistency was noted; the cylindrical axis and the axis of toricity remained relatively stable after surgery.
TL;DR: Throughout the experiments videorefraction measurements of astigmatic errors proved less consistent when compared with cycioplegic retinoscopy, and to its internal reliability, and the correlation between findings for spherical error was compatible with a previous study.
TL;DR: The results suggest the efficacy and safety of the piggyback combination of oxygen-permeable hard and soft contact lenses for the correction of astigmatism in patients with keratoconus.