青少年屈光不正眼在不同调节状态下晶状体的变化特点

目的:观察青少年远视眼与近视眼在不同调节状态下晶状体参数的动态变化,分析其差异并探讨晶状体变化的特点。方法:随机选取2019-01/10于我院门诊就诊的7～15岁青少年屈光不正患者50例86眼,分为近视组(29例46眼,平均等效球镜度-2.17±1.41D)和远视组(21例40眼,平均等效球镜度1.92±1.49D)。通过光学生物测量仪(IOL Master)测量眼轴长度(AL),通过眼前节光学相干断层扫描分析仪(SS-OCT)观察不同调节状态下(0、-3、-6D)晶状体厚度(LT)、晶状体前表面曲率半径(ALRC)、晶状体后表面曲率半径(PLRC)的动态变化。结果:调节放松状态下(0D),近视组LT显著小于远视组,ALRC与PLRC大于远视组(均P<0.01),且远视组眼轴短于近视组(22.49±1.12mm vs 24.48±0.82mm,P<0.01)。随着调节刺激的增大(-3、-6D),两组LT均显著增厚,ALRC与PLRC均显著减小(均P<0.01)。-3、-6D调节状态下,两组ALRC变化率均高于PLRC变化率(P<0.01),但两组间LT变化率及P...     

The effect of refractive error on perimetric thresholds using the Humphrey Field Analyser

Five normal young (20 ± 5 years) subjects had the central and peripheral fields of their right eyes measured using the Humphrey Field Analyser under emmetropic conditions and fitted with 38 per cent water content Hema spherical contact lenses to simulate distance refractive errors of 4 D, 6 D, 8 D, and 10 D of both myopia and hyperopia. The results for each induced refractive state were merged and averaged so that comparisons could be made with the averaged normal results. There was a mean decrease in sensitivity of 0.89 decibels (dB) per dioptre of uncorrected distance myopic refractive error or an estimated 1.27 dB per dioptre of myopic defocus (induced refractive error less 3 D due to the testing distance) for each of the 144 points for which thresholds were measured. For induced hyperopia, the mean decrease in sensitivity was 0.63 dB per dioptre of uncorrected distance refractive error or 1.01 dB per dioptre of estimated defocus (induced refractive error plus 3 D for the testing distance, less two-thirds of the accommodation). These reductions in sensitivity were significant centrally for 6 D or more of induced myopia (3 D or more of defocus) or 4 D or more of induced hyperopia (0.2 D or more of estimated defocus). Peripherally, the losses were significant in the temporal (and particularly inferior temporal) field for 6 D or more of induced myopia (3 D of defocus) and 4 D or more of induced hyperopia (0.2 D of estimated defocus). These results give ophthalmic practitioners a reference for use when assessing the peripheral fields of patients with high refractive errors.     

Prevalence and Associated Factors of Refractive Errors Among Type 2 Diabetics in Kinmen,Taiwan

Purpose: A community-based study was conducted to identify the extent of prevalence of refractive errors and their associated factors from among the Chinese type 2 diabetic population in Kinmen. Methods: A total of 547 patients (> 40 years old) with type 2 diabetes were examined with a complete eye screening tests including objective autorefraction. Spherical equivalent refractions of right eyes were reported. Data collected include age, gender, general medical information and serum biochemistry. Results: The mean refraction was ?0.83 ± 2.49 D. Prevalence rates were determined for myopia (44.1%), hyperopia (24.1%), high myopia (13.0%), and astigmatism (87.8%). Age is an important factor for all of the refractive errors. After adjustment for age, male gender and > 3 grade nuclear opacity appeared to be statistically significant factors for myopia. For hyperopia, ≥7% HbA1c was a significant associated factor, and for astigmatism, ≥200 mg/dl total cholesterol was the risk factor. Multiple linear regression showed that every increase of one year of age and one percent of HbA1c is associated with 0.04 D (p = 0.003) and 0.13D (p = 0.04) shift in hyperopia, respectively. Nuclear opacity with grade 3-4 and grade 5-6 will shift toward myopia of ?0.72D (p = 0.02) and ?5.34D (p < 0.0001) after adjustment for other risk factors. Conclusions: This study provides epidemiological data on refractive errors in a Chinese diabetic population in Kinmen, Taiwan. The myopia prevalence is higher than the reported rates in the general population. This survey further confirmed that myopia is more prevalent than hyperopia in the diabetic population. Age and blood sugar shift the refraction toward hyperopia while nuclear cataract reverses it. Correction of refractive errors in the diabetics remained a challenge as not only spectacles but medical intervention is mandatory.     

Factors Affecting Myopic Regression after Laser in Situ Keratomileusis and Laser-Assisted Subepithelial Keratectomy for High Myopia

To evaluate the factors affecting the amount of myopic regression after laser refractive surgery for high myopia, we retrospectively reviewed medical records of 1591 eyes with high myopia treated by laser in situ keratomileusis or laser-assisted subepithelial keratectomy at Shandong Eye Hospital between January 2008 and December 2012. Thirty-five eyes suffering a postoperative myopic shift of manifest spherical equivalent (MSE) of 0.25 diopter (D) or greater were included in this study. The mean refractive error was ?9.34 ± 1.89 D before surgery, and the mean regression was ?1.22 ± 0.70 D. Correlation analysis and multiple regression analysis were performed to assess the factors that were associated with the refractive regression. The age displayed a negative correlation with the diopter of regression (R = ?0.404, P = .016), while the optical zone diameter had a positive correlation with it (R = 0.406, P = .016). Explanatory variables relevant to the diopter of regression were age (partial regression coefficient B = ?0.045, P = .016) and optical zone diameter (partial regression coefficient B = 0.979, P = .014). Advanced-age patients with small optical zones were more predisposed to a larger amplitude of regression after laser refractive surgery for high myopia.     

Refractive plasticity of the developing chick eye

We have developed a lightweight plastic goggle with rigid contact lens inserts that can be applied to the eyes of newly hatched chicks to explore the range and accuracy of the developmental mechanism that responds to retinal defocus. Convex and concave lenses of 5, 10, 15, 20 and +30 D were applied to one eye on the day of hatching. The chick eye responds accurately to defocus between -10 and +15 D, although hyperopia develops more rapidly than myopia. Beyond this range there is first a levelling off of the response and then a decrease. The resulting refractive errors are caused mainly by increases and decreases in axial length, although high levels of hyperopia are associated with corneal flattening. If +/- 10 D defocusing lenses are applied nine days after hatching the resulting myopia and hyperopia are equal to about 80% of the inducing power. After one week of inducing myopia and hyperopia with +/- 10 D lenses, the inducing lenses were reversed. In this case, the refractive error did not reach the power of the second lens after another week of wear. Instead, astigmatism in varying amounts (0-12 D) was produced, being greater when reversal was from plus to minus. Finally, astigmatism can also be produced by applying 9 D toric inducing lenses on the day of hatching. The astigmatism produced varies from 2 to 6 D, and the most myopic meridian coincides with the power meridian of the inducing lens. This astigmatism appears to be primarily due to corneal toricity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Laser in situ keratomileus using the LaserSight 200 laser: results of 950 consecutive cases.

PURPOSE: To examine the refractive outcome in 950 consecutive eyes having laser in situ keratomileusis (LASIK) by 1 surgeon with experience in keratomileusis. SETTING: Outpatient excimer laser surgical facility. METHODS: This study comprised 950 consecutive eyes of 475 patients having LASIK as a primary procedure with a LaserSight 200 excimer laser (8.51 software). A nasal hinged flap and a Chiron microkeratome were used. Preoperative cycloplegic refraction was done only in patients younger than 25 years and in all hyperopic cases. Subjective preoperative and postoperative manifest refractions were done after autorefractometry in all cases. In cases of hyperopia, the software was modified by adding 30% to the refractive error. Enhancement results are not included. RESULTS: Of the 950 eyes, 893 (94.00%) were myopic and 57 (6.00%), hyperopic. In the low myopia group (1.00 to 3.99 D) of 223 eyes (24.97%), mean spherical equivalents (SEs) were -2.90 D +/- 0.56 (SD) preoperatively, -0.46 +/- 0.6 D 3 months postoperatively, and -0.41 +/- 0.5 D 6 months postoperatively. In the moderate myopia group (4.00 to 5.99 D) of 205 eyes (22.96%), respective mean SEs were -4.90 +/- 0.7 D, -0.90 D +/- 0.9 D, and -0.67 +/- 0.7 D. In the high myopia group (6.00 to 9.99) of 266 eyes (25.30%), the respective means were -7.70 +/- 1.3 D, -0.76 +/- 0.99 D, and -0.60 +/- 0.8 D. In the extreme myopia group (10.21 to 30.00) of 199 eyes (22.28%), the respective means were -13.30 +/- 2.9 D, -1.30 +/- 1.4 D, and -1.13 +/- 1.3 D. For the entire myopic group, the mean astigmatism was +1.55 +/- 1.38 D, +1.09 +/- 0.92 D, and +0.87 +/- 0.77 D, respectively. The low hyperopia group (1.00 to 2.99 D) of 39 eyes (68.42%) had a mean preoperative SE of +1.80 +/- 0.59 D and mean postoperative SEs of +1.00 +/- 0.76 D at 3 months and +1.16 +/- 0.52 D at 6 months. The respective means in the moderate hyperopia group (3.00 to 6.00) of 18 eyes (31.57%) were +4.62 +/- 1.19 D, +3.71 +/- 1.12 D, and +4.00 +/- 1.07 D. CONCLUSIONS: Laser in situ keratomileus for myopia using the LaserSight 200 excimer laser was stable with time and safe for the correction of different degrees of myopia. In the hyperopic group, marked regression occurred in a large percentage of patients. Thus, we will not perform LASIK for hyperopia until the software improves.     

Prevalence and predictors of refractive error and spectacle coverage in Nakuru, Kenya: a cross-sectional, population-based study

A cross-sectional study was undertaken in Nakuru, Kenya to assess the prevalence of refractive error and the spectacle coverage in a population aged ≥50 years. Of the 5,010 subjects who were eligible, 4,414 underwent examination (response rate 88.1 %). LogMAR visual acuity was assessed in all participants and refractive error was measured in both eyes using a Topcon auto refractor RM8800. Detailed interviews were undertaken and ownership of spectacles was assessed. Refractive error was responsible for 51.7 % of overall visual impairment (VI), 85.3 % (n = 191) of subjects with mild VI, 42.7 % (n = 152) of subjects with moderate VI, 16.7 % (n = 3) of subjects with severe VI and no cases of blindness. Myopia was more common than hyperopia affecting 59.5 % of those with refractive error compared to 27.4 % for hyperopia. High myopia (<?5.0 DS) was also more common than extreme hyperopia (>+5.0 DS). Of those who needed distance spectacles (spectacle coverage), 25.5 % owned spectacles. In conclusion, the oldest, most poor and least educated are most likely to have no spectacles and they should be specifically targeted when refractive services are put in place.     

Refractive errors in an elderly Chinese population in Taiwan: the Shihpai Eye Study

PURPOSE: Few epidemiologic data are available on refractive status in elderly Asians. The purpose of the study was to determine prevalence and risk factors associated with refractive errors in a metropolitan elderly Chinese population in Taiwan. METHODS: A population-based survey was conducted in the Shihpai district of Taipei, Taiwan. A total of 2045 residents aged 65 years or more were randomly selected and invited to complete a comprehensive questionnaire and undertake a detailed ocular examination, including best corrected visual acuity and measurements of refractive error, using autorefraction. Of the subjects, 1361 (66.6%) participated in the ocular examination. Spherical equivalent (SE) was calculated in diopters (D), and data from right eyes were reported. RESULTS: The age- and sex-adjusted prevalence rates were determined for myopia (SE<-0.5 D, 19.4%; SE<-1.0 D, 14.5%), high myopia (SE<-6.0 D, 2.4%), hyperopia (SE>+0.5 D, 59.0%; SE>+1.0 D, 44.2%), astigmatism (cylinder<-0.5 D, 74.0%; cylinder<-1.0 D, 45.3%), and anisometropia (SE difference between right and left eyes>0.5 D, 45.2%; SE difference>1.0 D, 21.8%). The prevalence of myopia, astigmatism, and anisometropia significantly increased with age (all P<0.01). The prevalence of hyperopia tended to decrease with age. There was no gender difference in prevalence rates in any type of refractive error, except that women had a higher rate of hyperopia (SE>+1.0 D) than men (P=0.004). Multivariate regression analysis showed that myopia was weakly associated with higher educational level. The severity of lens nuclear opacity was positively associated with the rates of myopia and negatively associated with the rates of hyperopia. CONCLUSIONS: The prevalence of myopia in this elderly Chinese population is not much higher than in similarly aged elderly white populations, compared with a much greater difference in prevalence among younger Chinese versus white people. This suggests that changing environmental factors may account for the increased prevalence of myopia in younger cohorts of Chinese.     

眼内屈光手术研究进展

屈光性手术是当前眼科界发展最快的前沿领域之一。其种类繁多,更新较快,而高度近视的屈光性手术对眼科医师来说一直是个挑战。由于准分子激光角膜原位磨镶术（LASIK）等角膜屈光手术在高度近视上的应用受限,加之近年来有晶状体眼人工晶状体技术和屈光性晶状体置换术的进步,使得眼内屈光手术在矫治高度近视、远视及老视等方面已逐步体现出其独特的优越性。就目前其最新研究进展,包括有晶状体眼人工晶状体的种类、手术并发症及其处理,屈光性晶状体置换术手术技术等进行综述。     

Laser in situ keratomileusis for myopia and hyperopia using the Lasersight 200 laser in 300 consecutive eyes

PURPOSE: To evaluate effectiveness, safety, predictability, and short-term stability of laser in situ keratomileusis (LASIK) using the LaserSight Compac-200 Mini excimer laser with software version 9.0, for all refractive errors. METHODS: One hundred fifty consecutive patients (300 eyes) that received bilateral LASIK for myopia, hyperopia, and astigmatism were studied prospectively. A new 9.0 software version applying a modified nomogram that takes advantage of bilateral surgery was used. Follow-up at 6 months was available for 267 eyes (89%). RESULTS: Six months postoperatively, 131 eyes (96.32%) in the low to moderate myopia group (-1.00 to -5.99 D; n=136) had a spherical equivalent refraction within +/-1.00 D, and 123 eyes (90.44%) were within +/-0.50 D of emmetropia. In the high to extreme myopia group (-6.00 to -25.00 D; n=114), 97 eyes (87.08%) had a spherical equivalent refraction within +/-1.00 D and 78 eyes (68.42%) were within +/-0.50 D of emmetropia. In the hyperopia group (+1.00 to +6.00 D; n=50), 44 eyes (88%) had a postoperative spherical equivalent refraction within +/-1.00 D, and 31 eyes (62%) were within +/-0.50 D of emmetropia. Mean change in spherical equivalent refraction at 6 months was less than -0.50 D in the low to high myopia groups and -1.16 +/- 0.55 D in the extreme myopia group. At 6 months follow-up, uncorrected visual acuity was 20/20 or better in 73 eyes (54%) in the low to moderate myopia groups and 21 eyes (18%) in the high to extreme myopia groups. In the hyperopia group at 6 months follow-up, uncorrected visual acuity was 20/20 or better in 31 eyes (62%) and 20/40 or better in 41 eyes (82%). Only two eyes had a temporary loss of two or more lines of spectacle-corrected visual acuity due to corneal folds that were surgically treated. Six months after LASIK, no eye had lost any lines of best spectacle-corrected visual acuity in this series. CONCLUSIONS: Our modified LASIK nomogram with the 9.0 software of the LaserSight 200 excimer laser (with a larger and smoother ablation pattern) resulted in safe and effective outcomes for the treatment of low to high myopia, astigmatism, and hyperopia.     

Analysis of Refractive Outcome and Related Factors in PACG Patients after Phacotrabeculectomy

Objective: To study the refractive outcome and related factors in primary angle closure glaucoma (PACG) patients 3 months after phacotrabeculectomy. Methods: This was a prospective clinical study. Fifty-one eyes of 51 patients with PACG and co-existing cataract who underwent phacotrabeculectomy at the EyeCenter of the Second Hospital of Jilin University from December 2018 to September 2019 were enrolled. Patients with intraocular pressure (IOP) ≤21 mmHg (1 mmHg=0.133 kPa) were classified as the normal IOP group and patients with IOP >21 mmHg were classified as the high IOP group. Anterior chamber depth (ACD), axial length (AL) and keratometry were measured by AL-scan, and the SRK-T formula of AL-scan software was used to calculate the intraocular lense power and predict the refractive outcome. Subjective refraction was performed at 3 months. According to postoperative refractive error (RE), the patients were divided into a myopia group (RE <-0.5 D), hyperopia group (RE >0.5 D) and no refractive error group (-0.5 D≤RE≤0.5 D). A Chi-square test was used to compare the distribution of refractive errors between the normal and high IOP groups. The preoperative biological parameters of the myopia group and hyperopia group were compared by an independent t-test, and a paired sample t-test was used to compare the biological parameters before and after surgery. Results: In the normal IOP group, there were 4 patients with myopia (17%), 3 patients with hyperopia (12%), and 17 patients without refractive error (71%); in the high IOP group, there were 7 patients with myopia (26%), 16 patients with hyperopia (59%), and 4 patients without refractive error (15%). The reduction of AL in patients with high IOP was greater than that in patients with normal IOP, and the difference was statistically significant (t=-4.308, P<0.001). The preoperative ACD of the hyperopia group was shallower than that of the myopia group, and the preoperative AL was shorter than that of myopia group. The difference was statistically significant (t=3.226, P=0.03; t=4.993, P<0.001). With keratometry, there was no significant difference between the two groups (t=-1.143, P=0.263). There was a negative correlation between postoperative RE and preoperative ACD and AL (r=-0.32, P=0.023; r=-0.52, P<0.001); there was no significant correlation between postoperative RE and keratometry (r=0.15, P=0.101). Conclusions: Compared with normal IOP, PACG patients with high IOP have more RE, and most of them are hyperopic RE. In addition, the shallower the ACD and the shorter the AL were, the refractive outcome of PACG patients after phacotrabeculectomy more likely tends to be hyperopia.     

PACG患者青白联合手术后的屈光状态及影响因素

目的：探讨原发性闭角型青光眼（PACG）患者行青光眼白内障联合手术后3个月的屈光状态以及相 关影响因素。方法：前瞻性临床研究。选择2018年12月至2019年9月于吉林大学第二医院眼科中 心行小梁切除联合白内障超声乳化摘除及人工晶状体植入术（简称青白联合术）的PACG合并白内障 患者51例（51眼）。术前用药后眼压≤21 mmHg（1 mmHg=0.133 kPa）患者作为正常眼压组（24例）, >21 mmHg作为高眼压组（27例）。所有患者术前使用AL-scan测量前房深度（ACD）、眼轴长度（AL）、 角膜曲率,并通过该仪器内置的SRK-T公式预测术后屈光度。随访至术后3个月行综合验光。根据 术后屈光误差（RE）将患者分为近视误差组（RE<-0.5 D）、远视误差组（RE>0.5 D）、无屈光误差组 （-0.5 D≤RE≤0.5 D）。正常眼压组与高眼压组患者术后屈光误差分布比较采用卡方检验,近视误 差组与远视误差组患者术前生物参数比较采用独立样本t检验,手术前后生物参数比较采用配对样 本t检验。结果：正常眼压组患者术后近视误差4例（17%）,远视误差3例（12%）,无屈光误差17例（71%）; 高眼压组患者近视误差7例（26%）,远视误差16例（59%）,无屈光误差4例（15%）。高眼压组患者 术后AL缩短程度大于正常眼压组患者,组间差异有统计学意义（t=-4.308,P<0.001）。远视误差组 患者术前ACD浅于近视误差组患者,术前AL短于近视误差组患者,组间差异比较均有统计学意 义（t=3.226,P=0.03;t=4.993,P<0.001）;近视误差组与远视误差组间的角膜曲率差异无统计学意义 （t=-1.143,P=0.263）。术后RE与术前ACD、AL均呈负相关（r=-0.32,P=0.023;r=-0.52,P<0.001）, 与术前角膜曲率无相关性（r=0.15,P=0.101）。结论：相对于术前眼压正常的PACG患者,术前高眼 压患者青白联合术后屈光误差发生的比例更高,且大多是远视屈光误差。另外,PACG患者青白联 合术后总体上存在术前ACD越浅,AL越短,术后屈光状态越倾向于远视的趋势。     

Results of laser in situ keratomileusis for myopia of -10 to -19 diopters with a Technolas 217 laser

PURPOSE: To evaluate the effectiveness, predictability, and safety of laser in situ keratomileusis (LASIK) for correcting myopia greater than -10.00 D. METHODS: Sixty-five eyes of 37 patients with myopia greater than -10.00 D underwent LASIK. Patients were evaluated on day 1, 1 week, 1, 3, and 6 months after surgery. Parameters evaluated were uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA), residual refractive error, regression of correction, and presence of any complication. RESULTS: Mean preoperative BSCVA was 0.745 +/- 0.234, which improved to 0.8070 +/- 0.237 postoperatively. The average preoperative UCVA was 0.022 +/- 0.02; postoperative UCVA at 6 months was 0.536 +/- 0.255. UCVA of 20/40 or better was achieved in 58% (38 eyes) and 20/20 or better in 26% (17 eyes). The average refractive error before LASIK was -12.64 +/- 2.16 D (range -10.00 to -19.00 D). Mean residual refractive error 1 week following LASIK was -0.63 +/- 1.36 D, which regressed to a mean -1.78 +/- 2.08 D at the end of 6 months. Nineteen eyes (29%) were within +/-0.50 D of intended refractive correction. CONCLUSION: LASIK was partially effective in the correction of high myopia. An initial overcorrection may be programmed to offset the effect of refractive regression.     

Femtosecond lenticule extraction (ReLEx®) for correction of hyperopia — first results

Background

This prospective study focused on the results of a novel method for refractive correction, femtosecond lenticule extraction (ReLEx®) in hyperopia, and reports the first 47 eyes.

Methods

In 47 hyperopic eyes (26 patients), both a flap and a lenticule of intrastromal corneal tissue were simultaneously cut utilizing the Carl Zeiss Meditec AG (CZM) 200 kHz VisuMax® femtosecond laser system. Thereafter, the lenticule was manually removed and the flap repositioned. Forty two out of 47 hyperopic eyes of the treatment group completed the final 9-month follow-up. The patients mean age was 42.3 (±9.0)?years. Their mean preoperative spherical equivalent (SE) was +2.8 (±1.3) D. UCVA and BSCVA after 9 months, objective and manifest refraction, as well as slit-lamp examination and side-effects were evaluated.

Results

Nine months postoperatively, 64 % of eyes treated were within ±1.0 D, and 38 % of eyes within ±0.5 D of intended correction. One of 47 eyes (2.1 %) lost more than 2 Snellen lines; none of the eyes had a UCVA less than 0.5. However, stability was less impressive when compared to ReLEx® for the correction of myopia.

Conclusions

First data suggest that ReLEx® is a feasible and effective procedure for treatment of hyperopia. Further research is needed to improve predictability and effectiveness of the procedure for the correction of hyperopia.     

First clinical results with the femtosecond neodynium-glass laser in refractive surgery

PURPOSE: We evaluated four femtosecond laser intrastromal cutting procedures: creation of a corneal flap for laser in situ keratomileusis (LASIK), tunnel and entry cut for intracorneal ring, corneal flap and removable lens for keratomileusis, and intrastromal ablation for myopia and hyperopia. METHODS: A clinical trial using a femtosecond surgical laser (IntraLase Corporation) was performed in partially sighted eyes. Femto-LASIK treatment was performed on 46 eyes up to -14.00 D; 16 patients received intracorneal ring segments (Femto-ICRS); 5 patients each with one highly myopic eye had femtosecond laser keratomileusis (FLK), and 13 patients each with one myopic or hyperopic eye had intrastromal ablation (ISPRK). In Femto-LASIK, excimer laser ablation was done under the flap. In Femto-ICRS, ring segments were introduced into the laser-created channels. In femtosecond laser keratomileusis, a lens-shaped block of stroma was removed manually from under the flap. RESULTS: No difference was found between the results obtained with Femto-LASIK and a standard microkeratome. No refractive effects occurred when the created flap was not elevated. In cases of Femto-ICRS and conventional ICRS produced the same refractive results. With Femto-ICRS, no intraoperative complications occurred and visual acuity improved immediately after surgery. In femtosecond laser keratomileusis, high myopia was corrected without using excimer laser ablation; centralization of the treatment area was excellent. In intrastromal ablation, 1 to 2 hours after surgery the corneas were highly transparent; refractive results were stable. CONCLUSIONS: Femtosecond lasers can produce precise intrastromal cutting, offering significant safety and other advantages (no razor blades, corneal trauma, partial resections, or sterilization issues) over current techniques.     

Topographic and biomechanical differences between hyperopic and myopic laser in situ keratomileusis

PURPOSE: To evaluate the size, shape, and uniformity of the videokeratographic functional optical zone (FOZ) after laser in situ keratomileusis (LASIK) in 2 cohorts of patients with equivalent amounts of preoperative myopic or hyperopic astigmatism. SETTING: Pepose Vision Institute, St. Louis, Missouri, USA. METHODS: Eyes with myopic or hyperopic astigmatism (n=27 in each group) that had LASIK with the Visx Star S3 laser were retrospectively selected to match for level of preoperative refractive error. Slit-scanning videokeratography was performed preoperatively and 6 months postoperatively and analyzed using custom software. The FOZ was calculated by analyzing refractive power maps using a region-growing algorithm. Difference maps were generated from slit images and compared for interval change in corneal elevation, tangential curvature, and refractive power. The difference maps were also averaged (mean difference maps) for each target population. A Zernike decomposition of corneal first-surface elevation was performed to compare postoperative values with baseline parameters. RESULTS: The mean postoperative refractive sphere at 6 months was -0.17 diopter (D) +/- 0.66 (SD) and +0.25 +/- 0.85 D in the myopia group and hyperopia group, respectively, and the mean postoperative astigmatism, -0.49 +/- 0.32 D and -0.65 +/- 0.52 D, respectively (P=.11). Based on the refractive power maps, the mean preoperative and postoperative myopic FOZ was 33.09 +/- 7.30 mm(2) and 30.94 +/- 5.43 mm(2), respectively, and the mean hyperopic FOZ, 33.19 +/- 7.96 mm(2) and 37.99 +/- 6.88 mm(2), respectively. After LASIK, there was an increase in magnitude of negative anterior corneal surface spherical-like Zernike values in the myopia group (P<.0001) and an increase in magnitude of positive spherical-like Zernike values in the hyperopia group. Postoperatively, significant induction of corneal surface horizontal coma was noted in hyperopic eyes (P<.0001). Hyperopic eyes, on average, had larger topographic FOZs after LASIK, but with less uniformity of curvature and power change than myopic eyes. CONCLUSIONS: Hyperopic LASIK, which involves more transition points along the ablation diameter, produced a less uniform topographic FOZ than typical myopic treatments. Less predictable biomechanical changes from the circumferential release of tension on collagen bundles after midperipheral hyperopic ablation and greater variation in beam centration and the angle of incidence may contribute to the greater variability in corneal curvature and power in hyperopic LASIK than in myopic LASIK.     

Einfluss der kornealen Biomechanik auf die Myopieregression nach Laser-in-situ-Keratomileusis

Background

Laser in situ keratomileusis is a safe and accepted method for correcting myopia. The operational results in terms of accuracy as well as the subjective acceptance of patients for corrections to – 8 D are now considered to be promising (Seiler, Refraktive Chirurgie der Hornhaut, 2000); however, postoperative results show individual patient problems in long-term stability. It is believed that the preoperative condition of the cornea (e.g. thickness, biomechanical properties) could have an influence on postoperative problems such as myopic regression.

Method

This study included a total of 46 eyes from 25 patients. At 3 months postoperatively, 15 patients (19 eyes) showed a SEQ of ??0.50 D or more. Within this group, 11 patients (15 eyes) developed a regression (regression group) within the first 3 postoperative months. The remainder of the total group did not show any regression (stability group). The subjects of this study were on average 33?±?8 years (stability group) and 31?±?7 years old (regression group). The corneal thickness was tested and refractive error, visual acuity (BCVA/UCVA) and intraocular pressure was measured. In addition, the corneal hysteresis (CH) and corneal resistance factor (CRF) were determined.

Results

The mean preoperative spherical equivalent refraction was ??3.14 D?±?1.41 D (SE) in the stability group and ? 6.47 D?±?1.40 D (p?=?0.001)in the regression group. Also, the postoperative spherical equivalents were statistically significant different (p?<?0.05). In contrast, the mean preoperative corneal thickness showed no differences in both groups (p?=?0.96) (stability group 563?±?36 µm and regression group 563?±?28 µm).

Conclusions

The aim of the study to detect a possible causal relationship between myopia regression after LASIK and the biomechanical properties of the cornea and corneal thickness could not be clearly identified.     

Conductive keratoplasty: an approach for the correction of residual hyperopia in post-lasik pseudophakia

Although there are many formulae for the calculation of intraocular lens power in the eyes with previous kerato-refractive surgeries, unexpected refractive bias still exists. Hyperopic bias is particularly disliked because it affects both uncorrected distance and near visual acuity. Surgical treatment of the residual hyperopia for the eyes with both laser in situ keratomileusis and cataract surgery remains to be a big problem. Conductive keratoplasty has been shown to be an effective, safe and predictable method for low and moderate hyperopia in the pseudophakic eyes or in the eyes with kerato-refractive surgeries. However, the efficacy and safety of conductive keratoplasty in the correction of residual hyperopia after both corneal and lens refractive surgeries has not been reported. Herein, we reported the surgical correction with conductive keratoplasty for cases of residual hyperopia with/without astigmatism after previous laser in situ keratomileusis for high myopia and following phacoemulsification combined with posterior intraocular lens implantation for complicated cataract.     

Indications, results, and complications of LASIK.

The technique of laser in situ keratomileusis (LASIK) has been used with very encouraging results in the treatment of all degrees of myopia and also shows considerable promise in the treatment of hyperopia. Compared with photorefractive keratectomy, LASIK is advantageous in causing minimal postoperative discomfort, in its rapid recovery of clear vision and stabilization of refractive change, in the infrequent occurrence of haze, and in its greater facility in correcting high degrees of myopia. However, LASIK is the more surgically demanding technique. We discuss our own experience with LASIK as well as published data from other centers. We anticipate that LASIK will continue to increase in importance in the surgical correction of refractive error.     

Neue torische diffraktive Multifokallinse in der refraktiven Chirurgie

Background

Up to now only a combination of lens and corneal surgery in the sense of bioptics could be used in refractive surgery for correcting high myopia, hyperopia or presbyopia in combination with astigmatisms. Since the summer of 2007 the first model of a toric diffractive bifocal intraocular lens is available for correcting combined refractive errors. The first results on 10 eyes from 6 patients are presented in this article.

Method

Refractive lens exchange with implantation of a toric diffractive multifocal lens (Acri.LISA toric, Zeiss/^*Acritec) was performed on 10 eyes from 6 patients (age 25-57 years old). Preoperatively best corrected visual acuity varied between 0.5 and 1.0 in patients with astigmatisms between 1.5 and 5.75 dpt in combination with hyperopia (one patient) or myopia.

Results

Postoperatively uncorrected visual acuity varied between 0.5 and 1.25 and best corrected visual acuity between 0.8 and 1.25. Postoperative refraction as spherical equivalent was 0 to +1.0 dpt with postoperative astigmatisms between 0 and 1.0 dpt. Rotational stability was found in all eyes, early postoperatively and also after 1 year. Patient satisfaction was very high.

Conclusions

The new toric multifocal lens is a new option in refractive surgery. The first results are very promising but further results and a comparison to the bioptics procedure have to be awaited.