Mean Cylinder Power Research Articles

Refractive error in unilateral Duane syndrome

To investigate whether chronic co-contraction of the medial and lateral rectus muscles leads to higher against-the-rule astigmatism in affected versus fellow eyes in Duane syndrome. A database of 4,103 patients of Dr. Arthur Jampolsky was queried for diagnosis of Duane syndrome. Inclusion criteria were unilateral Duane syndrome and complete data set. Refractive error was compared between Duane and fellow eyes. A total of 84 patients with unilateral Duane syndrome were identified. The spherical equivalent of Duane eyes and fellow eyes was similar (0.4 vs. 0.2 [P = 0.14]). Mean cylinder power was higher in Duane eyes compared to fellow eyes (0.7 vs 0.4 [P = 0.0003]). There was modest evidence of more against-the-rule astigmatism in Duane eyes compared to fellow eyes (P = 0.04) but no difference for with-the-rule astigmatism (P = 0.83). Duane compared to fellow eyes were, however, significantly more likely to have oblique astigmatism (P = 0.004) or any astigmatism at all (P = 0.0005). Duane eyes compared to fellow eyes had higher astigmatism that was more likely to be oblique. Our study lends support to the hypothesis that extraocular muscles may influence refractive error.

Refractive outcomes of table-mounted and hand-held auto-refractometers in children: an observational cross-sectional study

BackgroundTo compare the refractive results of hand-held and table-mounted autorefractors.MethodsWe designed this study as an observational, cross-sectional study. We compared the mean spheric and cylinder power, spherical equivalent, Jackson cross-cylinder values, determined the limits of agreement (LoA), and evaluated the reliability of two autorefractors.ResultsWe evaluated 256 eyes of 256 pediatric patients (mean age, 9.12 ± 2.26 years; range, 5–16 years). 49% of the patients were female, and 51% were male. The Nidek HandyRef-K autorefractor measured relatively more astigmatism (P < 0.001) and less hyperopia (P = 0.024). The mean differences and 95% LoA were 0.06 D ± 0.47 D (− 0.82 D to 0.98 D) in spherical power, 0.08 D ± 0.28 D (− 0.47 D to 0.64 D) in cylindrical power, 0.11 D ± 0.47 D (− 0.81 D to 1.01 D) in spherical equivalent, 0.02 D ± 0.36 D (− 0.73 D to 0.69 D) in Jackson cross-cylinder power at 0°, 0.005 D ± 0.54 D (− 1.07 D to 1.06 D) in Jackson cross-cylinder power at 45°. We found the difference within 0.50 D in 244 (95%) eyes for spherical power, in 245 (96%) eyes for cylindrical power, 228 (89%) eyes for spherical equivalent, 224 (87%) eyes for Jackson cross-cylinder power at 0°, 213 (83%) eyes for Jackson cross-cylinder power at 45°. When comparing devices, there were strong correlations for spherical power (Spearman’s rho = 0.99, P < 0.001), cylindrical power (Spearman’s rho = 0.88, P < 0.001), and spherical equivalent (Spearman’s rho = 0.98, P < 0.001).ConclusionTwo autorefractors showed clinically applicable agreement limits; excellent reliability for spherical power and spherical equivalent and good reliability for cylindrical power; high positive percent agreement for spherical and cylindrical power, spherical equivalent, Jackson cross-cylinder power at 0°and 45°. These results showed that both devices might be used interchangeably for screening of refractive error in children.

Initial Single-Site Experience Using SMILE for the Treatment of Astigmatism in Myopic Eyes and Comparison of Astigmatic Outcomes with Existing Literature.

PurposeTo assess a single site’s initial experience with SMILE for the treatment of myopic astigmatism and compare outcomes and vector analysis results with the US Food and Drug Administration (FDA) results and published literature.Patients and MethodsForty-eight eyes (29 patients) with mean preoperative sphere of −5.11 ± 1.31 diopters (D) and cylinder of −1.12 ± 0.60 D underwent SMILE. Visual acuity, refractive, and vector analysis outcomes as well as subjective measures were reported at three and twelve months postoperatively and compared with FDA results and the published literature between 2014 and 2020 involving treatment of patients with mean cylinders of >−0.50 to ≤−3.00 D.ResultsAt three and twelve months, 43 and 32 eyes were evaluated, respectively. At twelve months, mean cylinder power was reduced to −0.38 ± 0.38 D with 78.1% achieving ≤±0.50 D. Uncorrected distance visual acuity (UDVA) ≥20/20 was achieved in 77.4% of eyes by twelve months with 100% achieving ≥20/30 UDVA. No loss of corrected distance visual acuity was observed in eyes seen at twelve months. Correction index (CI) at twelve months was 0.90 indicating overall undercorrection of 10%. Twelve-month CI was 0.96, 0.90, and 0.83 in eyes with preoperative cylinders of <−1.00 D, ≥−1.00 to <−2.00 D, and ≥−2.00 D, respectively. Mean angle of error was −1.58 ± 11.61° ranging from −24.22° to 37.75°.ConclusionWe found SMILE to be an effective and safe means of achieving spectacle independence and improving visual acuity in patients with myopic astigmatism. SMILE has the potential for improved clinical outcomes with better nomogram guidance and advancements in technique. However, surgeons must be aware of the potential for undercorrection in with-the-rule astigmatism and at higher preoperative cylinders and as well as the potential for overcorrection in against-the-rule and lower preoperative cylinder astigmatism.

The profile of astigmatism in 6–12-year-old children in Iran

PurposeTo determine the prevalence of astigmatism and its determinants in schoolchildren aged 6–12 years. MethodsThe students selected by stratified cluster random sampling in Shahroud, north of Iran. Optometric examination included uncorrected visual acuity, refraction with autorefractometer, manifest refraction with retinoscopy followed by subjective and cycloplegic refraction (after two drops of cyclopentolate 1% with 5min interval were instilled in each eye).A cylinder power ≥0.75diopter (D) in at least one eye was considered as astigmatism. The prevalence of astigmatism was reported based on a cylinder power higher than 0.50, 1.00, and 2.00D in cycloplegic refraction, followed by power vector analysis. ResultsAfter applying the inclusion criteria, the data of 5528 children were analyzed. The prevalence of astigmatism was 16.7% (95% CI: 15.6–17.7) in total, 16.6% (95% CI: 15.2–18.0) in boys and 16.8% (95% CI: 15.2–18.3) in girls (p=0.920) and decreased from 21.5% in 6-year-old children to 13.7% in 10-year-olds, and then again increased to 18.3% in children aged 12 years. Moreover, 17.2% (95% CI: 16.0–18.3) of urban and 12.1% (95% CI: 10.0–14.1) of rural children had astigmatism (p<0.001). The prevalence of with-the-rule, against-the-rule, and oblique astigmatism was 14.2%, 2.1%, and 0.33%, respectively. The mean cylinder power was −1.31, −0.46, and −0.44D in children with spherical myopia, emmetropia, and hyperopia, respectively (p<0.001). Urban students had a higher J0 and boys had a higher J45. ConclusionThe prevalence of astigmatism in this study was lower than previous studies. Astigmatism prevalence was markedly higher in urban children.

Impact of epithelial basement membrane dystrophy and Salzmann nodular degeneration on biometry measurements

To determine the effects of epithelial basement membrane dystrophy (EBMD) and Salzmann nodular degeneration (SND) on optical biometry measurements. Department of Ophthalmology, Duke University Eye Center, Durham, North Carolina, USA. Retrospective case series. Cataractous eyes with EBMD or SND scheduled for superficial keratectomy (SK) or phototherapeutic keratectomy (PTK) had baseline biometry. Repeat biometry was performed 30days or more postoperatively and compared with baseline. The primary outcome measures were keratometry (K) values, axial length and magnitude, and axis of corneal astigmatism. Secondary outcome measures were the change in intraocular lens (IOL) power, toricity, and axis. In the EBMD group (26 eyes), the mean absolute intersession difference showed an increase in mean K values (P<.001) and a change in IOL spherical power predicting a postoperative spherical equivalent (SE) closest to zero (P<.001) in 21 of 26 eyes (8=0.5 diopter [D]; 9=1.0 D; 4>1.0 D). In toric IOL-eligible eyes, the recommended IOL toricity changed for 16 of 24 eyes, with a mean cylinder power change of 1.2 D. In the SND group (13 eyes), the mean absolute intersession difference showed an increase in mean K values (P=.023) and a change in IOL spherical power predicting a postoperative SE closest to zero (P<.001) in 11 of 13 eyes (3=0.5 D; 3=1.0 D; 5>1.0 D). The recommended IOL toricity changed for 10 of 11 eyes (mean cylinder power change 1.5 D). Both EBMD and SND altered K measurements as evidenced by clinically significant changes in keratometry after SK or PTK. These changes affected the spherical and toric IOL power. Appropriate management of EBMD and SND before cataract surgery can yield more reliable biometric data for surgical planning.

Characteristics of astigmatism in Black South African high school children.

Astigmatism impairs vision at various distances and causes symptoms of asthenopia which negatively impacts reading efficiency. The aim of conducting this study was to determine the prevalence and distribution of astigmatism and its relationship to gender, age, school grade levels and spherical ametropia. Using a multi-stage random cluster sampling, 1589 children who included 635 (40%), males, and 954 (60%), females were selected from 13 out of a sample frame of 60 schools. Their ages ranged between 13 and 18 years with a mean of 15.81±1.56 years. The parameters evaluated included visual acuity using the LogMAR chart and refractive errors measured using an autorefractor and then refined subjectively. Axis of astigmatism was presented in the vector method where positive values of J0 indicated with-the-rule, negative values described against-the-rule and J45 represented oblique astigmatism. The mean cylinder power was -0.09 ± 0.27 and mainly with-the-rule, J0 = 0.01 ± 0.11. The overall prevalence of clinically significant astigmatism (≤ - 0.75 cylinder) in the sample was 3.1% [(95% Confidence interval = 2.1-4.1%)]. Cylinder of at least - 0.25 power was considered to classify astigmatism types. Thus, the estimated distributions of types of astigmatism were: axis- 11.5%, sphero-astigmatism 10.1% and magnitude-astigmatism 11.2% while 67.2% had no cylinder of any magnitude. The prevalence of astigmatism is relatively low in this population studied. Older children and those in high school grade levels were more likely to have with-the-rule or against-the-rule astigmatism. The prevalence of astigmatism were comparable within but not across regions.

Single-step transepithelial versus alcohol-assisted photorefractive keratectomy in the treatment of high myopia: a comparative evaluation over 12 months

Background/aimsTo evaluate refractive outcomes of single-step transepithelial photorefractive keratectomy (TransPRK) versus alcohol-assisted PRK (EtOH-PRK) for the correction of high myopia.MethodsThis was a retrospective non-randomised comparative study conducted at the American...

Safety and Visual Outcome of Visian Toric ICL Implantation after Corneal Collagen Cross-Linking in Keratoconus: Up to 2 Years of Follow-Up.

Purpose. To evaluate the long-term safety and clinical outcome of phakic Visian toric implantable collamer lens (ICL) insertion after corneal collagen cross-linking (CXL) in progressive keratoconus. Methods. This was a retrospective study of 30 eyes (19 patients), with progressive keratoconus, who underwent sequential CXL followed by Visian toric ICL implantation after 6 months. Results. At baseline, 6 eyes had stage I, 14 eyes stage II, and 10 eyes stage III keratoconus graded by Amsler-Krumeich classification. At 6 months after CXL, only K (steep) and K (max) decreased significantly from baseline, with no change in visual acuity or refraction. Flattening in keratometric readings was stable thereafter. There was significant improvement in mean uncorrected distance visual acuity (1.57 ± 0.56 to 0.17 ± 0.06 logMAR, P < 0.001) and mean corrected distance visual acuity (0.17 ± 0.08 to 0.11 ± 0.05 logMAR, P < 0.001) at 12 months after ICL implantation that was maintained at the 2-year follow-up. Mean cylinder power and mean spherical equivalent (SE) also decreased significantly after ICL implantation. A small hyperopic shift in SE (+0.25 D) was observed at 2 years that did not alter visual outcomes. Conclusions. Visian toric ICL implantation following CXL is an effective option for improving visual acuity in patients with keratoconus up to 2 years.

Characteristics of Astigmatism in a Population of Tunisian School-Children.

Purpose:To evaluate the characteristics of astigmatism in a cross-sectional study of schoolchildren in Tunisia.Materials and Methods:A random cluster design was used to recruit children from primary schools across urban and rural settings in Tunisia, from 2008 to 2010. A total of 6192 students aged 6–14-years old were enrolled. All students whose uncorrected visual acuity was worse than 20/20 underwent a complete ophthalmic examination. Astigmatism was defined as the cylinder power of 0.75 diopter (D) or greater.Results:The prevalence of astigmatism was 6.67%. Mean cylinder power was - 1.89 ± 0.79D. The prevalence of astigmatism increased statistically significantly with age (P = 0.032). The prevalence of astigmatism was not significantly related to gender (P = 0.051). Of those with cylinder, 63.6%, 17.8%, and 18.6% schoolchildren had with with-the-rule, against-the-rule, and oblique astigmatism, respectively. ATR astigmatism was significantly higher in males (P = 0.033). There was no significant association between the student's area of residence and astigmatism (P = 0.059).Conclusion:Comparisons with other studies show that the prevalence of astigmatism in Tunisia is higher than in some countries. The prevalence of astigmatism increased with age but not gender. The majority of schoolchildren had with-the-rule astigmatism.

The effect of posterior corneal flat meridian and astigmatism amount on the total corneal astigmatism estimated from anterior corneal measurements.

To evaluate the effects of posterior corneal astigmatism and the absolute flat meridian difference between anterior and posterior corneal surfaces (AMDAnt-Post) on the estimation of total corneal astigmatism using anterior corneal measurements (simulated keratometry [K]). Ninety-nine eyes of 99 healthy participants were enrolled. Anterior, posterior, and total mean corneal power, cylinder power, flat meridian, and vector components J0, and J45 measured by a dual Scheimpflug camera were analyzed. The correlation between the posterior corneal cylinder power, AMDAnt-Post, and the difference in the cylinder power between simulated K and total cornea (cylinder power differenceSimK-Tot) were evaluated. The cylinder power differenceSimK-Tot was positively correlated with the posterior corneal cylinder power (rho = 0.704 and P < 0.001) and negatively correlated with AMDAnt-Post (rho = -0.717 and P < 0.001). In the multivariate linear regression analysis, anterior corneal J0 was strongly associated with the posterior corneal cylinder power and the AMDAnt-Post. When corneal J0 had a positive value, the cylinder power of simulated K tended to be larger than the total corneal cylinder power. In comparison, the opposite trend was presented in eyes with negative anterior corneal J0. When anterior corneal J0 was larger than 1.0 or smaller than -0.9, the errors from estimating the total corneal cylinder power using anterior corneal measurements tended to be larger than 0.25 D. Posterior corneal astigmatism should be considered for more accurate corneal astigmatism predictions, especially in eyes with anterior corneal astigmatism greater than 2.0 D of with-the-rule astigmatism or greater than 1.8 D of against-the-rule astigmatism.

Iris-fixated toric phakic intraocular lens for myopic astigmatism

To evaluate the efficacy, predictability, safety, stability, and complications of the Artiflex toric iris-fixated phakic intraocular lens (pIOL) for myopic astigmatism. Private practice surgery centers, Valencia and Terrassa, Spain. Cohort study. At 12 months, refraction, uncorrected (UDVA) and corrected (CDVA) distance visual acuities, complications, pIOL misalignment, and endothelial cell count (ECC) were evaluated. Indices of success and misalignment were calculated using vector analysis. The study enrolled 42 eyes in 25 patients aged 21 to 39 years. The mean spherical equivalent decreased from -8.85 diopters (D) ± 2.71 (SD) to -0.37 ± 0.46 D, with 66.7% of the eyes within ± 0.50 D. The mean cylinder power decreased from -2.90 D (range -1.50 to -5.00 D) to -0.39 D (range 0.00 to -1.50 D); refraction was highly stable. All eyes achieved a decimal UDVA of 0.5 or better and a CDVA of 0.8 or better. A gain of 1 line or more of CDVA was found in 69.1% of eyes. The mean clinical pIOL misalignment was 2.6 ± 1.8 degrees; 1 eye (2.4%) required surgical repositioning of the pIOL. The mean ECC decrease was 9.3% ± 1.8%; iris pigment precipitates were observed in 16.7% of eyes. Vector analysis showed excellent mean indices of success for overall (0.94 ± 0.04), spherical (0.96 ± 0.05), and astigmatic (0.95 ± 0.16) corrections; the mean angle of error was 1.8 ± 2.7 degrees. Implantation of the toric pIOL was effective, predictable, safe, and stable for the correction of myopic astigmatism. No author has a financial or proprietary interest in any material or method mentioned.

Refractive outcomes of laser-assisted subepithelial keratectomy for myopia, hyperopia, and astigmatism using a 213 nm wavelength solid-state laser

To study the visual and refractive outcomes after laser-assisted subepithelial keratectomy (LASEK) performed with a 213 nm solid-state laser for a broad range of refractive errors. Private practice, Jersey, United Kingdom. Case series. The LASEK was performed using a Pulzar Z1 213 nm solid-state laser. Manifest refraction and uncorrected (UDVA) and corrected (CDVA) distance visual acuities were measured preoperatively and 2 and 6 months postoperatively. Accuracy, safety, efficacy, and stability were assessed at 6 months. The study enrolled 245 eyes (134 patients). The preoperative spherical equivalent (SE) refractive errors ranged from -9.50 to +6.50 diopters (D); 24 eyes had more than 2.50 D of astigmatism. At 6 months, 60.4% of eyes were within ±0.25 D of the intended SE, 89.4% were within ±0.50 D, and 97.9% were within ±1.00 D. No eye lost 2 or more lines of CDVA; 95.5% of eyes were unchanged or gained 1 line. The mean cylinder power decreased from -0.98 ± 1.17 D to -0.14 ± 0.28 DC at 6 months. The mean SE was unchanged over the follow-up period; -0.01 ± 0.57 D and -0.01 ± 0.55 D at 2 months and 6 months, respectively. Laser-assisted subepithelial keratectomy performed using the 213 nm wavelength solid-state laser was safe, accurate, and effective for the treatment of myopia, hyperopia, and astigmatism. No author has a financial or proprietary interest in any material or method mentioned.

Analysis of photoastigmatic keratectomy with the cross-cylinder ablation

Aim:The aim was to evaluate the safety and efficacy of the “cross-cylinder” technique in the correction of astigmatism.Setting and Design:A prospective interventional study from a university eye department was conducted.Material and Methods:The photoastigmatic refractive keratectomy (PARK) using the “cross-cylinder” technique was performed in 102 eyes of 84 patients with at least 0.75 D of astigmatism. The study population was divided into two groups: in the first group the preoperative astigmatic power ranged from –0.75 D to –3.00 D (group 1), in the second group it ranged from –3.25 D to –6.00 D (group 2). Group 1 included 82 eyes of 67 patients (29 males and 38 females) with a mean cylinder power of –1.90 ± 0.63 D, group 2 included 20 eyes of 17 patients (13 males and 4 females) with a mean cylinder power of -4.28 ± 0.76 D. All eyes were targeted for emmetropia. The results were evaluated using Calossi's vector analysis method. Six-month postoperative outcomes are presented.Results:Six months after PARK the mean sphere for the entire cohort was +0.28 ± 0.75 D (range +2.5 to –2 D), the mean cylindrical power was +0.33 ± 0.51 D (range +2.5 to –1.25 D) and the mean spherical equivalent refraction was +0.73 ± 0.81 D (range +1.75 to –2 D).Conclusions:The cross-cylinder technique may be safely used with predictable results for the correction of astigmatism.

Astigmatism in preschool children in Taiwan

To elucidate the prevalence of astigmatism and its corneal component, the association between the amount of astigmatism and its axis, and the association between the axis of astigmatism and body mass index (BMI) in Taiwanese preschool children. In this population-based study we analyzed 2 data sets, one obtained by retrospective review of vision-screening data and another obtained in a prospective observational study. Each study collected data for age, sex, and refraction status. Autokeratometry, height, and weight measurements were obtained only in the observational study. Astigmatism was classified as with-the-rule, against-the-rule, or oblique. The prevalence of astigmatism was unassociated with age or sex in both data sets. The retrospective study (1,094 subjects; mean age, 5 years; range, 2.19-7.32 years) revealed that 13.3% of the subjects had astigmatism > or = 1.00 D, and most of them had with-the-rule astigmatism; 4.0% had high astigmatism (>1.50 D). Children with with-the-rule astigmatism had greater mean cylinder power than those with against-the-rule or oblique astigmatism. In the prospective study (190 subjects; mean age, 5.65 years; range, 3.79-6.68 years) astigmatism correlated with its corneal component. Preschoolers with with-the-rule astigmatism and with-the-rule corneal astigmatism had greater BMI and heavier weight than those with against-the-rule or oblique type. Astigmatism is common in Taiwanese preschool children. The predominant types are with-the-rule and oblique astigmatism. Most patients with high astigmatism and high corneal astigmatism have with-the-rule type. High BMI or weight is associated with with-the-rule astigmatism and with with-the-rule corneal astigmatism.

Longitudinal changes in the cylinder power of children with accommodative esotropia

To assess the longitudinal changes in the cylindrical refractive errors of children with accommodative esotropia according to the age when glasses were prescribed. Refractive errors were followed longitudinally for 120 children with accommodative esotropia for a mean of 4.4 +/- 2.5 years. Cycloplegic refractions were performed using an autorefractor. The refractive data were analyzed for three groups of children based on their age at the time spectacles were prescribed. In all three age groups, the mean cylinder power was initially about 1.0 D. Over time, the mean cylinder power in the two younger age groups gradually increased by about 0.5 D. In the oldest age group, the mean cylinder power remained relatively unchanged with some suggestion of a decrease in the later years. A regression model demonstrated the statistical significance of both the age when spectacles were prescribed (p < 0.0001) and the interaction of age and time after spectacles were prescribed (p = 0.0034). Longitudinal changes in cylinder power for children with accommodative esotropia vary according to their age when spectacle wear is initiated. The greatest increase in cylinder developed in the children who were youngest when initially treated.

Long-term changes in the cylinder power of hypermetropic children with and without accommodative esotropia

Introduction: Lambert and Lynn suggested that cylinder power increases in children with accommodative esotropia treated with spectacles. We analyzed the changes in cylinder power of spectacle-wearing hypermetropic children with and without esotropia. Methods: Refractive errors were followed in 108 children with hypermetropia with and without esotropia for a mean of 3.9 years. Cycloplegic refractions were performed by retinoscopy. The refractive data were analyzed for the entire group and according to age of spectacle prescription, and ocular alignment. Results: The mean cylinder power increased on average by 0.16 D. In the youngest age group (0 < 2 years) the mean increase was 0.3 D; in the second group (2 < 4 years) the mean increase was 0.2 D, and in the third group (>4 years) the mean increase was 0.08 D. There was a tendency toward a larger average increase in astigmatism in the accommodative esotropes. Discussion: Similar to the results reported by others, we found a slight increase in cylinder power, which was more substantial among patients under the age of two. Nevertheless, this change, although statistically significant, is probably of no clinical importance. Conclusions: In children wearing spectacles for hypermetropia with and without esotropia, astigmatism increases minimally. Cylinder power changes were more common in the accommodative esotrope group.

Refractive errors in an older population: The blue mountains eye study

Objective To determine prevalence and associations with refractive errors in a defined older population. Design Cross-sectional study. Participants A total of 3654 residents, aged 49–97, of the Blue Mountains, west of Sydney, Australia. Methods Comprehensive questionnaire and detailed eye examination, including refraction. Main outcome measures Refractive error of phakic eyes, age, gender, and education. Results Prevalence rates were determined for myopia (15%), hyperopia (57%), and emmetropia (28%). Hyperopia prevalence was age-related, increasing from 36% in persons aged <60 years to 71% of persons aged ≥80 ( P < 0.0001), whereas myopia prevalence decreased with age, from 21% in persons aged <60 years to 10% of persons aged ≥80 years ( P < 0.0001). Younger myopic subjects in this population reported first wearing distance correction at a significantly younger age than older subjects, P < 0.0001. After adjustment for age, women were slightly more hyperopic (mean +0.75 diopters [D]) than men (mean +0.59 D, P = 0.0012. The gender-adjusted mean spherical error increased with age from +0.03 D in persons aged <60 years to +1.2 D in persons aged ≥80 years ( P < 0.0001). The gender-adjusted mean cylinder power also increased with age, from −0.6 D in persons aged <60 years to −1.2 D in persons aged ≥80 years ( P < 0.0001). The mean axis of astigmatism was “against the rule” in all age groups. Anisometropia increased with age, from a mean of 0.4 D in persons aged <60 to 0.9 D in persons aged ≥80 years ( P < 0.0001). Higher education was associated with myopia in men ( P = 0.009) but not in women ( P = 0.21) after adjustment for age. Conclusion This report has documented the detailed refractive status of an older population, confirming previously described trends but also finding an apparent higher prevalence of myopia among younger members of this community.

Astigmatism Following Photorefractive Keratectomy for Myopia

Astigmatism following photorefractive keratectomy for myopia has been reported as stable as early as 2 to 3 months. The authors report 36 out of 60 consecutive eyes with variations in the cylindrical component of their refraction at 6 months after laser treatment. A standard photorefractive keratectomy was carried out on 60 consecutive eyes in 52 patients over a 7-month period. The manifest refraction of these eyes was followed for 6 months. Thirty-six eyes demonstrated a change in the cylindrical element of their refraction manifested as a change in cylinder power or axis, or both. The mean pretreatment cylinder power in the group that underwent a change in the cylindrical element was significantly higher than the mean of the group where this did not take place. The mean cylinder power change was 0.75 diopters (D) and in 9 eyes this change was 1.00 D or more. The corrected and uncorrected postoperative visual acuities were the same in the two groups. This observation implies meridional variability in the healing process of the anterior cornea following photorefractive keratectomy.