Simple method of measuring ocular rotation in supine position during small incision lenticule extraction

INTRODUCTION

Static cyclotorsion has been a major concern in surgery since the infancy of refractive surgery, and it has been emphasized that rotation of the eyeball during refractive surgery is an important cause of refractive errors left after surgery.Swami

suggested that an average misalignment of 4°could result in 14% of astigmatism not being treated properly,and a 6° difference visible in more than 25% of the eye would result in a 20% undercorrection, and a misalignment of 16° would lead to undercorrection in more than 50% of astigmatism. Previously, static cyclotorsion was measured using various methods, such as using a double Maddox rod

and video-oculography

, and the position change did not have a significant effect on ocular torsion. After the introduction of the eye-tracking system in refractive surgery,research on cyclotorsion has been active. Chernyak

measured the difference in cyclotorsion before and during surgery.The average cyclotorsion of both eyes was approximately 2.0°, and 19 out of 24 patients had binocular excyclotorsion.Subsequent studies generally showed a pattern of binocular excyclotorsion

.

Compared to conventional laser-assisted

keratomileusis,small incision lenticule extraction (SMILE), which has no flap-related complications, provides rapid patient recovery,and has low incidence of dryness, is gaining worldwide popularity and taking over conventional refractive surgery

.However, since its surgical procedure is different from the existing surgery, there is absence of an eye-tracking system in SMILE. Therefore, errors may occur in centering and in the accurate setting of the astigmatism axis during surgery. There are several studies on how to correct these errors; however, all these techniques are manual methods

.

There have been several studies in measuring static cyclotorsion,and among them, Jackson cross cylinder

, Maddox double-rod test

, videokeratography

, and intraoperative measurement were used

. No methods associated to SMILE were reported.In this study, we investigated a method to simply measure the amount of cyclotorsion without the need for extra hardware through anterior slit photography and surgical parameter comparison. In addition, the effect of the amount of cyclotorsion on the surgical results was investigated.

SUBJECTS AND METHODS

Statistical analysis was performed using SPSS software (version 22, SPSS, Inc., USA). Excyclotorsion was indicated by positive values and incyclotorsion by negative values. The mean cyclotorsion indicates the average of these positive or negative values. The absolute value of cyclotorsion indicates the amount of rotation of the eye,regardless of the direction of the cyclotorsion. Chi-square test, Mann-Whitney

test, Wilcoxon signed-rank test,Friedman test, and Pearson’s correlation analysis were used for preoperative and postoperative comparisons. Differences were considered statistically significant at

values less than 0.05.

总之，综上所述，水肥一体化在我国有着良好的发展前景，虽然目前在操作中遇到一些问题。但随着该项技术的发展和国内环境的支持，这些问题终将得到解决。本文正是基于对这方面的认识，对葡萄种植中水肥一体化推广和应用进行较为详细的分析，并以此阐述该项技术在应用中的各种优势。

In this study, we measured intraocular rotation through anterior slit photographs after surgery. The absolute value of the torsional angle was 3.141°±2.256°, and the range of torsion was 0.5°-11.4°. The right eyes tended to be excyclotorted,and the left eyes tended to be incyclotorted. This result is consistent with the results of Park

, Zhao

, and Terauchi

. Zhao

suggested that this result may be due to eye laterality; that is, since the right eye is predominant in many cases, the strength of the oblique muscles of the right eye is stronger and there will be a difference between the two eyes. In correlation analysis, preoperative values such as gender, preoperative corneal thickness, and preoperative intraocular pressure were not correlated with the amount of cyclotosion and the direction of cyclotorsion, and these results are consistent with previous studies.

Anterior slit photographs were taken 1d, 1, 3, and 6mo after surgery. Photographs were taken using a Haag-Street BQ 900 illumination system with the EyeSuite IM 600 imaging module (Haag-Streit International, Koeniz,Switzerland). Photographs were taken by an experienced photographer under indoor lighting. When this picture was taken, the patient kept their eyes straight, the slit beam width was 1 mm, the light source intensity was 60%, and the slit beam angle was 30°. This procedure is represented schematically in Figure 1. Photographs in which the flap was torn during surgery or the incision margins were difficult to distinguish were excluded.

After obtaining the pictures, we calculated the cyclotorsion from the margin of the corneal incision. These calculations were performed using the Image J software (version 1.53i, NIH, USA). First,we checked the upper end of the corneal incision line and drew an imaginary circle along the incision line. A straight line was drawn connecting the upper end of the incision line to the center of the imaginary circle. This straight line was moved counterclockwise to the center of the corneal incision line. The length of incision was 2.5 mm, so it actually moved at a 1.25-mm distance along the contour of the circle. Because the diameter of the circle was 7.5 mm, the counterclockwise shift was calculated to be 19.1°. Theoretically, if there was no cyclotorsion during the surgery, the angle between this straight line and the horizontalline would be 135°. Therefore,by measuring the actual degree of this angle, we could measure the degree of torsion. The method of calculating the cyclotorsion is represented in a schematic diagram in Figure 2.We evaluated the cyclotorsion using photographs taken at 1mo.

To investigate the effect of preoperative parameters on the cyclotorsion, eyes were divided into a group with the amount of cyclotorsion 4 degrees or more and a group with the amount of cyclotorsion less than 4 degrees and analyzed (Table 2).There was no correlation between gender, preoperative corneal thickness, preoperative intraocular pressure, amount of rotation, and direction of rotation. It was found that the smaller the preoperative sphere, the higher the amount of cyclotorsion (

=0.11,

=0.016; Figure 8). There was no significant association between the amount of cyclotorsion and preoperative astigmatism (

=0.758; Figure 9).

To investigate the reproducibility of this measurement method, we measured the cyclotorsion at 1d, 1, 3, and 6mo postoperatively in one patient, and these consecutive data were compared.

本组患者中，累及1个椎体324例，2个椎体96例，3个及以上椎体54例；胸椎384个，腰椎330个。骨密度为（-3.43±0.36）SD。其中OVCF 489个椎体、OVBF 140个椎体、Kummell病85个椎体。具体手术部位分布详见表1。

This study was performed in accordance with the tenets of the Declaration of Helsinki and was approved by the Institutional Review Board/Ethics Committee of Chungbuk National University Hospital, Cheongju, Korea.This retrospective study included 484 eyes from 242 patients who underwent SMILE procedures between November 2018 and December 2020 at the Seoul Daabom Eye Center,Cheongju, Korea. The inclusion criteria for this study were corrected distance visual acuity of 20/20 or better, myopia of-1.00 diopters (D) to -9.00 D with astigmatism of 0 to -4.00 D,and stable refraction for more than 1y. The exclusion criteria were the suspicion of keratoconus on corneal topography,severe dry eye, progressive corneal degeneration, the presence of systemic diseases and severe ocular diseases, and a history of intraocular or corneal surgery.

RESULTS

Of the 242 patients, 124 (51.2%)were men and 118 (48.8%) were women, and all patients underwent SMILE surgery in both eyes. The mean age was 28.47±6.44y, and the mean intraocular pressure was 17.55±2.19 mm Hg. The preoperative mean spherical equivalent (SE) was -4.10±1.64 D, the preoperative mean spherical power was -3.70±2.18 D, and the mean astigmatism was -0.82±0.74 D. The mean corneal thickness measured before surgery was 552.64±30.01 μm (Table 1).

UCVA and SE improved significantly after the surgery. The postoperative logarithm of the minimum angle of resolution (logMAR) UCVA was-0.04±0.08 at 1wk, -0.07±0.07 at 1mo, -0.08±0.07 at 3mo, and-0.09±0.07 at 6mo (Figure 3). The mean postoperative SE was 0.03±0.29 at 1wk, 0.01±0.29 at 1mo, -0.04±0.24 at 3mo and-0.03±0.17 at 6mo (Figure 4).

In 484 eyes, 219 (45.2%) eyes had excyclotorsion,235 (48.6%) eyes had incyclotorsion, and 30 (6.2%) eyes had no torsion. In the right eyes, excyclotorsion was 55.0%,incyclotorsion was 38.0%, and no torsion was observed in 7.0% of eyes. In the left eyes, excyclotorsion was 35.5%,incyclotorsion was 59.1%, and there was no torsion in 5.4% of the eyes. Figure 5 is a series of photographs of a representative case. The right eyes tended to be excyclotorted, and the left eyes tended to be incyclotorted and statistically significant(

<0.01, Chi-square test; Figure 6). The mean cyclotorsion was 1.18°±3.69°, and the absolute value of the torsional angle was 3.14°±2.26°. The range of cyclotorsion was 0.5°-11.4°.The distribution of the cyclotorsional angle is shown in Figure 7.In a single patient, the direction and amount of cyclotorsion in the right and left eyes were not correlated with each other(

=0.15,

=0.14, respectively).

Preoperative data such as age, sex,uncorrected distance visual acuity (UCVA), best corrected distance visual acuity (BCVA), manifest refraction, corneal thickness, and intraocular pressure were collected. Patients were examined at 1d, 1, 3, and 6mo postoperatively. When patients visited the clinic, objective and subjective refraction tests were performed, and UCVA and BCVA were recorded.

我国早在2000年就开始实施了国库管理制度。这一项制度的实施就实现了国库资金的统一管理，同时，还实现了将财政资金进行直接的划拨。例如税收和非税收的缴费都统一纳入财政专户之中，国库管理制度的实施，规范了财政资金的收支，提高了财政资金的管理效率。与此同时，对于预算的执行也建立了动态的监控机制，从而对其进行全面的监督，这能够有效地对预算的执行起到警示的作用。

There was no significant association between the amount of cyclotorsion and postoperative UCVA, refractive outcomes(Table 3). In 98 eyes with astigmatism greater than -1.50 D,correlations between the amount of cyclotorsion, residualastigmatism, and BCVA after surgery were investigated, but there was no statistical correlation.

The ratio of right eye excyclotorsion and left eye incyclotorsion on 1d was higher than that at 1, 3, and 6mo, and this was statistically significant (all

<0.01; Table 4).There was no difference between the 1, 3, and 6mo results in the right and left eyes (

=0.15,

=0.16, respectively).

DISCUSSION

Since SMILE was first announced, it has opened a new horizon of refractive surgery

. It is known that the visual acuity results are comparable to those of conventional surgery, but there have been studies showing that astigmatism and highorder aberration results are inferior

. This result is thought to be influenced by the fact that the contact between the eyeball and the patient interface of the surgical device is required for suction during surgery, which is a deep-seated problemof SMILE, and undesirable decentration may occur during this process. Likewise, due to the absence of an eye-tracking system, errors in the astigmatism axis may occur, which may lead to errors in astigmatism correction

.

In refractive surgery, it is important to precisely cut or ablate the corneal tissue according to the target surgical parameters. Axial misalignment is known to affect the surgery outcomes, and it can induce from the undercorrection of the astigmatism to the formation of a new cylinder axis in severe cases

. Astigmatism axis measurements are performed in an upright position; however, the surgery is performed in a supine position. Therefore, if an eyeball rotation occurs attributed to a change from an upright position to a supine position, axial misalignment can be induced, and the postoperative visual acuity might be affected as a result of axial misalignment.Eyeball rotation through a change in posture is called static cyclotorsion, and numerous studies have been conducted on how it affects the surgical outcome of refractive surgery

.Static cyclotorsion is a major concern in the field of refractive surgery, and various eye-tracking systems have been developed to correct astigmatism axis error

.

All SMILE procedures aimed to obtain emmetropia. All patients received topical anesthesia, standard sterile draping, and speculum insertion. SMILE surgery was performed using a Visumax femtosecond laser (Carl Zeiss Meditec AG, Jena, Germany) with a repetition rate of 500 kHz and pulse energy of 110-140 nJ and followed a previously published surgical procedure. The cap diameter was 7.5 mm,the lenticule diameter was 6.5 mm, and the cap thickness was 120 μm. A single 2.5-mm side cut was made at 135° position.No manual corneal marking or manual compensation of the cyclotorsion was performed. The lenticule was then dissected,separated through the side cut, and manually removed.

数学全息定义和非全息定义的教学目标是不同的．按照布鲁姆的认知水平的层次(“记忆”、“理解”、“运用”、“分析”、“评价”、“创造”)来分类.数学定义的教学目标可分为三个层次，即初级目标、中级目标、高级目标．本文将“运用”分为三个层次，即“很简单的运用”(相当于直接运用或直接套公式)、“简单运用”(包括逆用、变用等)、“灵活运用”．全息定义教学的初级目标是达到“记忆”、“理解”、“很简单的运用”等层次的要求，中级目标是在达到初级目标的基础上还应达到“简单运用”、“分析”层次的要求，高级目标是在达到初级目标和中级目标的基础上还应达到“灵活运用”、“评价”、“创造”层次的要求．

Recently, studies on the results of manual compensation in SMILE have been published

. Chen

reported that 84 patients were treated with standard SMILE for 30 patients and SMILE with manual cyclotorsion compensation for 54 patients. The SE of the two groups was the same, but better results were obtained in the vector analysis of astigmatism.Xu

compared the surgical results of the group with and without manual compensation in SMILE and found no difference between the two groups in terms of visual acuity and refractive outcomes, even in high astigmatism. According to this result, Xu

reported that manual compensation could reduce alignment error, but the average amount of cyclotorsion was too small to affect astigmatism, so it was not compulsory. Köse

proposed a method of compensating cyclotorsion by overlapping an image taken in an upright state on a surgical screen using an image-guided system and rotating the patient’s head. Standard SMILE for 62 eyes and SMILE with cyclotorsion compensation were performed for 62 eyes, and better results were obtained in UCVA and residual astigmatism. The mean astigmatism error was -0.19±0.17 D in the cyclotorsion compensation group and -0.45±0.38 D in the standard group. As described above, there are various opinions about the results of manual compensation. In our study, surgery was performed without cyclotorsion correction;however, satisfactory results were obtained after surgery. There was no difference in the amount of astigmatism according to the degree and direction of cyclotorsion. There was no difference in final residual astigmatism and UCVA, and even in the analysis of cases with astigmatism greater than-1.50 D, cyclotorsion did not affect the residual astigmatism and UCVA. Therefore, our results support the suggestion that manual compensation is not obligatory. However, there are studies that the results of manual compensation were favorable, so additional research is needed. The methods of manual compensation during surgery in the above studies were to correct the patient interface by rotating the suction cone directly after applying the suction after limbal marking, and rotating the head according to upright images. Rotating the suction cone, limbal marking processes and rotating the head have limitations due to the possibility of human error, and there is a risk of suction loss when rotating the cone; therefore,caution is required for manipulation. Further research is needed to see if it’s worth taking the risk.

One of the merits of this study is that it does not require any additional equipment to measure the cyclotorsions.Although most recent studies measured cyclotorsions through eye tracking systems, our study has clinical advantages for analyzing cyclotorsions that can be easily measured in clinical settings without additional devices. Another advantage of this study is that this method has sufficient reproducibility, even though it is a very simple method. In this study, there was no significant difference in the results of our surgery at an average of 1, 3, and 6mo. Although it was found that, on average,the right eye excyclotorsion and left eye incyclotorsion were more evident on the 1

day, these results are attributed to the unclear wound margins in the immediate postoperative period,or delayed adaptation to the refractive changes immediately after surgery. There is a study result that the accommodative response increases after refractive surgery for myopia

, also there is a paper that cyclotorsion occurs when accommodative response occurs

. In our study, the increased accommodative response may have caused cyclotorsion in the very early stage of surgery, and it is possible to hypothesize that the gradual change of accommodative state affects the degree of cyclotorsion. Further research is needed in this point.

This study has some limitations. First, this method can only measure cyclotorsions but cannot measure decentrations, so the effect of decentration cannot be confirmed. However, studies have shown that the effect of decentration is not thought to be significantly related to surgical outcomes. Huang

divided their subjects into two groups with an astigmatism of 2.5 D or more and less than 2.5 D and investigated the amount of decentration and the surgical outcome. They showed that coma and spherical aberration were more frequently induced in the high astigmatism group. However, according to the results of this study, the effect of decentration was considered insignificant. Second, one examiner directly set the endpoint of the incision manually without using an automated program, hence subjective errors may occur. There is room for improvement when using an automated method using an image-tracking program, and further studies are needed. Third,our study investigates reproducibility with photos taken over a long period of time and we used only one photo each day.So long-term reproducibility can be investigated, but shortterm reproducibility cannot be determined. This should be supplemented through additional research.

In conclusion, the newly devised ocular cyclotorsion measurement method used in this study is a suitable test method for evaluating ocular cyclotorsion after SMILE. In addition, this new technique is easy to perform and does not require additional equipment; therefore, so we believe it can be widely used. Because this method is based on actual surgical results, it is more realistic than the previous measurement method. With this method, we were able to measure ocular cyclotorsion according to the operating posture and showed that ocular cyclotorsion did not significantly affect visual acuity and refraction after surgery.

1.2 临床诊治及保肢方案 所有患者首先判断生命体征是否平稳，有无重大合并伤。予纠正失血性休克、补充血容量，在维持基本生命体征、全身情况稳定后，评估肢体损伤程度，进行保肢手术。一期彻底清创，清除坏死组织，尤其是失活的肌肉组织不能姑息，清创时注意保护血管和神经。先恢复骨组织的连续性和稳定性，采用外固定支架和钢板内固定。血管修复是保肢的关键，需要时移植血管。骨骼、神经、血管修复后，予以皮肤软组织覆盖，如皮肤软组织缺损较多，行邻近皮肤肌肉转位，优先覆盖血管神经骨骼，残余较大创面予创面封闭负压引流(vaccum sealing drainage,VSD)治疗；二期行植皮或皮瓣修复。

None;

None;

自2003年8月正式投入发电运行以来，沙集泵站积极利用徐洪河行洪弃水开发水力发电，创造了可观的经济效益，对2003—2011年发电运行数据统计，年平均发电340.4万kWh，机组年平均运行14 183.3台时（按照单台机组平均出力240 kW）。经测试进行降低转速后，每台机发电功率增加约100 kW，全站共增加发电功率500 kW。考虑变频机组等相关设备消耗电量约40 kW，改造后泵站年均发电量可增至470.9万kWh，相当于火电厂燃烧578.7 t标准煤产生的电量，无论是经济效益还是社会效益均比较显著。

None;

None.

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