Comparison of refractive and visual outcomes with centration points 80% and 100% from pupil center toward the coaxially sighted corneal light reflex

Chang, Jinn-Ming; Law, Antony; Ng, J. C.; Chan, Vincent K.C.

doi:10.1016/j.jcrs.2015.09.030

Cited by 20 publications

(20 citation statements)

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“…The coaxially sighted corneal light re ex piont is the corneal entry point of the visual axis [5] .Studies have shown that coaxially sighted corneal light re ex piont is the ideal ablation centration point, because coaxially sighted corneal light re ex piont is the closest point to the visual axis and is not affected by changes of pupil size and center position, with an average of 0.02 mm [6] .Therefore, the angle kappa can be understood as P-Dist [7] .However, the angle kappa is not a xed value, and changes with the dynamic change of the pupil center position [8,9] .That is why it is necessary to further explore the dynamic changes of the pupil size and center position suitable for excimer laser surgery, P-Dist and its correlation with other biomechanics.The related research at home and abroad hasn't been reported.…”

Section: Introductionmentioning

confidence: 99%

Dynamic distribution of angle kappa and its biomechanical relationships in population who are suitable for excimer laser refractive surgery

W¹,

Cui²,

Li³

et al. 2020

Preprint

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Background To explore the dynamic distribution of pupil size and center,the eccentricity distribution of angle kappa, and its correlation with other biomechanics about suitable for excimer laser refractive surgery. Methods Randomly selected 225 patients (407 eyes) who underwent femtosecond laser combined with excimer laser in situkeratomileusis,preoperative use of Wavelight Allegro Topolyzer Corneal Topography ( Wavelight Laser Technologies AG, Erlangen, Germany ) to measure the pupil size and center position, the German Wavelight EX500 excimer Laser (500Hz) records the deviation between the pupil center and the coaxially sighted corneal light reflex when the patient is supine. Results The average displacement distribution of P-Dist (the eccentricity between the pupil center and the coaxially sighted corneal light reflex point) is 0.225 ± 0.102 mm, and 80% of the eyes are ≤ 0.30 mm.The coaxially sighted corneal light reflex point is mainly deviated to the superior temporal side of the corneal center (34%).Under the dark light condition, the x-axis of the left eye was: -0.046 ± 0.091 mm, the x-axis of the right eye was: -0.152 ± 0.084 mm, with statistical difference ( P = 0.015) (the right eye shifted to the temporal side), the y-axis direction had no statistical change ( P = 0.062). The WTW was positively correlated with changes of pupil diameter (dark pupil diameter-bright pupil diameter) ( r = 0.270, P <0.001).The SE and measured centroid shift was negative correlated ( r = - 0.214, P = 0.002). Conclusion The pupil of the left eye becomes smaller, the anterior chamber becomes shallower, and the angle kappa increases relative to the right eye.In patients with large WTW, a darker light environment is maintained during the operation to improve the efficiency of pupil matching.The dynamic change of angle kappa in high myopia population is small.

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Section: Introductionmentioning

confidence: 99%

Dynamic distribution of angle kappa and its biomechanical relationships in population who are suitable for excimer laser refractive surgery

W¹,

Cui²,

Li³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…Only Zhang et al used the femtosecond laser to create the corneal flap, while others used the microkeratome [17]. A study by Chang et al which compared the difference in locating the centration point between 80 and 100% from the pupil center toward the CSCLR did not meet the inclusion criteria and was thus excluded from this meta-analysis [20]. Another study reported by Okamoto et al in 2009 was also excluded because the subjects may have also been involved in the one published in 2011 for the same observation period and short follow-ups [15,21].…”

Section: Resultsmentioning

confidence: 99%

Clinical outcomes of corneal refractive surgery comparing centration on the corneal vertex with the pupil center: a meta-analysis

et al. 2020

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Purpose To compare the visual and refractive outcomes between centration on the corneal vertex and the pupil center in corneal refractive surgery. Methods A comprehensive literature search was conducted using PubMed, MEDLINE, EMBASE, and the Cochrane Library to identify relevant studies. The primary outcomes were the postoperative spherical equivalent (SE), effectiveness [uncorrected distance visual acuity (UDVA) C 20/20, eyes within ± 0.50 diopter (D) of target refraction], and safety [loss C 2 lines of corrected distance visual acuity (CDVA)]. Higher-order aberrations were considered secondary outcomes. Results Seven studies describing a total of 1964 eyes were included in this meta-analysis. A statistical significance in postoperative SE was found between the two centration methods for the correction of myopia that favor the CV-centered method (p \ 0.001). No significant differences were observed in the proportion of eyes with UDVA C 20/20 or loss C 2 lines of CDVA postoperatively. However, the proportion of eyes within ± 0.50 D was slightly higher (p = 0.02) and the coma aberration was much lower in the corneal vertex-centered method (p \ 0.001). Conclusion Preferable visual and refractive outcomes could be achieved with either centering on the corneal vertex or pupil center in corneal refractive surgery; however, the corneal vertex-centered method has shown partial benefits in some clinical indices. In order to obtain higher quality of clinical evidences, more randomized controlled trials (RCTs) are required in further investigations.

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“…Especially with premium lenses such as toric, enhanced depth of focus (EDOF) or multifocal lenses [ 2 ] or with enhanced excimer or femtosecond laser refractive surgery procedures [ 3 – 15 ] large angles Alpha or Kappa were identified as potential risk factors for an unsatisfactory outcome. In corneal refractive surgery, centration of the corneal ablation pattern can be directly performed based on the corneal centre (limbus centre [ 16 ]), pupil centre [ 17 ], or the Purkinje reflex PI originated from a coaxial light source in the surgical microscope [ 5 , 12 ], and the benefits and drawbacks of the different centring strategies has been discussed controversially in many scientific papers. In contrast, in cataract surgery intraoperative centration of the lens implant could be performed with some restrictions [ 18 ], but the final lens position is mostly determined by wound healing effects and capsular shrinkage in the postoperative interval [ 8 ].…”

Section: Introductionmentioning

confidence: 99%

Translation model for CW chord to angle Alpha derived from a Monte-Carlo simulation based on raytracing

et al. 2022

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Background The Chang-Waring chord is provided by many ophthalmic instruments, but proper interpretation of this chord for use in centring refractive procedures at the cornea is not fully understood. The purpose of this study is to develop a strategy for translating the Chang-Waring chord (position of pupil centre relative to the Purkinje reflex PI) into angle Alpha using raytracing techniques. Methods The retrospective analysis was based on a large dataset of 8959 measurements of 8959 eyes from 1 clinical centre, using the Casia2 anterior segment tomographer. An optical model based on: corneal front and back surface radius Ra and Rp, asphericities Qa and Qp, corneal thickness CCT, anterior chamber depth ACD, and pupil centre position (X-Y position: PupX and PupY), was defined for each measurement. Using raytracing rays with an incident angle IX and IY the CW chord (CWX and CWY) was calculated. Using these data, a multivariable linear model was built up in terms of a Monte-Carlo simulation for a simple translation of incident ray angle to CW chord. Results Raytracing allows for calculation of the CW chord CWX/CWY from biometric measures and the incident ray angle IX/IY. In our dataset mean values of CWX = 0.32±0.30 mm and CWY = -0.10±0.26 mm were derived for a mean incident ray angle (angle Alpha) of IX = -5.02±1.77° and IY = 0.01±1.47°. The raytracing results could be modelled with a linear multivariable model, and the effect sizes for the prediction model for CWX are identified as Ra, Qa, Rp, CCT, ACD, PupX, PupY, IX, and for CWY they are Ra, Rp, PupY, and IY. Conclusion Today the CW chord can be directly measured with any biometer, topographer or tomographer. If biometric measures of Ra, Qa, Rp, CCT, ACD, PupX, PupY are available in addition to the CW chord components CWX and CWY, a prediction of angle Alpha is possible using a simple matrix operation.

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Comparison of refractive and visual outcomes with centration points 80% and 100% from pupil center toward the coaxially sighted corneal light reflex

Abstract: Both 80% centration and 100% centration were safe and effective. Compared with the 100% group, the 80% group had less astigmatism and less undercorrection.

Cited by 20 publications

References 19 publications

Dynamic distribution of angle kappa and its biomechanical relationships in population who are suitable for excimer laser refractive surgery

Dynamic distribution of angle kappa and its biomechanical relationships in population who are suitable for excimer laser refractive surgery

Clinical outcomes of corneal refractive surgery comparing centration on the corneal vertex with the pupil center: a meta-analysis

Translation model for CW chord to angle Alpha derived from a Monte-Carlo simulation based on raytracing

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