Assessing the corneal power change after refractive surgery using Scheimpflug imaging

Gyldenkerne, Anders; Ivarsen, Anders; Hjortdal, Jesper

doi:10.1111/opo.12202

Cited by 25 publications

(23 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The main outcomes were the radii of the anterior and posterior corneal curvatures for the sagittal 3-mm-diameter zone (sag 3 mm) and the total corneal refractive power (TCRP 4mm, apex, zone ). 31 The average changes in the variables after operation (D ¼ postoperative À preoperative values) and at increased chamber pressure (d ¼ 40 mm Hg À 15 mm Hg values) were compared between groups. The central corneal thickness (CCT) and cap thickness after SMILE were evaluated by optical coherence tomography (OCT; Heidelberg Engineering GmbH, Heidelberg, Germany).…”

Section: Methodsmentioning

confidence: 99%

Refractive Correction and Biomechanical Strength Following SMILE With a 110- or 160-μm Cap Thickness, Evaluated Ex Vivo by Inflation Test

Damgaard

Ivarsen

Hjortdal

2018

Invest. Ophthalmol. Vis. Sci.

Self Cite

View full text Add to dashboard Cite

PURPOSE. To examine the refractive correction and corneal biomechanical strength after small incision lenticule extraction (SMILE) by using a 110-or 160-lm cap thickness.METHODS. Thirty-two human donor corneas were allocated into 4 groups, combining one of two cap thicknesses (110 and 160 lm) with one of two spherical corrections (À4 D and À8 D). Each cornea was mounted on an artificial anterior chamber. The chamber pressure was adjusted by an attached 8% dextran media column.The anterior and posterior sagittal 3-mm-diameter curvature (r sag3mm ) and the total corneal refractive power (TCRP 4mm,apex,zone ) were obtained before and after SMILE at a chamber pressure of 15 or 40 mm Hg. The average changes after surgery (D ¼ postoperative À preoperative) and at increased chamber pressure (d ¼ 40 mm Hg À 15 mm Hg) were compared. RESULTS. A 110-lm cap thickness caused more anterior flattening (Dr 15,À8D , 1.02 6 0.08 mm versus 0.60 6 0.17 mm), less posterior steepening (Dr 15,À8D , À0.19 6 0.11 mm versus À0.45 6 0.20 mm), and more myopic correction (DTCRP 15,À8D , À6.30 6 0.96 D versus À4.55 6 1.66 D) than a 160-lm cap thickness for À8 D SMILE (P < 0.034), but not for À4 D SMILE (DTCRP 15,À4D,110lm , À3.86 6 1.31 D versus DTCRP 15,À4D,160lm , À3.57 6 1.27 D, P ¼ 0.718). After SMILE, increased chamber pressure caused anterior steepening (P < 0.014), which was similar at cap thicknesses of 110 and 160 lm (dr À4D , À0.13 6 0.14 mm versus À0.09 6 0.05mm, P ¼ 0.431).CONCLUSIONS. For high myopic corrections, a 160-lm cap caused less anterior curvature flattening and more posterior steepening than a 110-lm cap, and consequently less myopic correction. The inflation test revealed a reduction in the biomechanical strength after SMILE; this was similar when using a 110-or 160-lm cap thickness.

show abstract

Section: Methodsmentioning

confidence: 99%

Refractive Correction and Biomechanical Strength Following SMILE With a 110- or 160-μm Cap Thickness, Evaluated Ex Vivo by Inflation Test

Damgaard

Ivarsen

Hjortdal

2018

Invest. Ophthalmol. Vis. Sci.

Self Cite

View full text Add to dashboard Cite

show abstract

“…For TCRP4astig, [17] [7] zone, apex, and total corneal refractive power options were selected in the power distribution display of the Pentacam software (version 1.18r04), and the zone diameter was set to 4.0 mm. The magnitude of TCRP4astig was calculated by K2 − K1 diopter in “power calculation in actual zone” and the meridian of K2 was read as the meridian of TCRP4astig.…”

Section: Methodsmentioning

confidence: 99%

“…The total corneal refractive power of 4-mm apex zone by Pentacam (TCRP4) is a possible solution, because it can accurately measure the surgically induced changes in manifest refraction after corneal laser surgery. [17] In contrast to the keratometric power, TCRP4 does not rely on any prior assumptions about the corneal shape but is the most realistic means of determining the corneal power. [17] In addition, the TCRP4 method, combining the equivalent K reading derived from TCPR4 and the Holladay 2 formula, shows good predictive capability of the IOL power calculation for the modified cornea after myopic keratorefractive surgery.…”

Section: Introductionmentioning

confidence: 99%

“…[17] In contrast to the keratometric power, TCRP4 does not rely on any prior assumptions about the corneal shape but is the most realistic means of determining the corneal power. [17] In addition, the TCRP4 method, combining the equivalent K reading derived from TCPR4 and the Holladay 2 formula, shows good predictive capability of the IOL power calculation for the modified cornea after myopic keratorefractive surgery. [18]…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Calculations of actual corneal astigmatism using total corneal refractive power before and after myopic keratorefractive surgery

Seo

Yang²,

Kim

et al. 2017

PLoS ONE

View full text Add to dashboard Cite

PurposeTo calculate actual corneal astigmatism using the total corneal refractive astigmatism for the 4-mm apex zone of the Pentacam (TCRP4astig) and keratometric astigmatism (Kastig) before and after photorefractive keratectomy or laser in situ keratomileusisMethodsUncomplicated 56 eyes after more than 6 months from the surgery were recruited by chart review. Various corneal astigmatisms were measured using the Pentacam and autokeratometer before and after surgery. Three eyes were excluded and 53 eyes of 38 subjects with with-the-rule astigmatism (WTR) were finally included. The astigmatisms were investigated using polar value analysis. When TCRP4astig was set as an actual astigmatism, the efficacy of arithmetic or coefficient adjustment of Kastig was evaluated using bivariate analysis.ResultsThe difference between the simulated keratometer astigmatism of the Pentacam (SimKastig) and Kastig was strongly correlated with the difference between TCRP4astig and Kastig. TCRP4astig was different from Kastig in magnitude rather than meridian before and after surgery; the preoperative difference was due to the posterior cornea only; however, the postoperative difference was observed in both anterior and posterior parts. For arithmetic adjustment, 0.28 D and 0.27 D were subtracted from the preoperative and postoperative magnitudes of Kastig, respectively. For coefficient adjustment, the preoperative and postoperative magnitudes of Kastig were multiplied by 0.80 and 0.66, respectively. By arithmetic or coefficient adjustment, the difference between TCRP4astig and adjusted Kastig would be less than 0.75 D in magnitude for 95% of cases.ConclusionsKastig was successfully adjusted to TCPR4astig before and after myopic keratorefractive surgery in cases of WTR. For use of TCRP4astig directly, SimKastig and Kastig should be matched.

show abstract

“…In canines, the majority of astigmatism research revolves around the lens and streak retinoscopy, with minimal clinical information available regarding the cornea in isolation . The physician assessment of visual acuity is more advanced and involves evaluation of corneal astigmatism as part of a regular examination and workup for patients, especially surgical candidates …”

Section: Introductionmentioning

confidence: 99%

Surgically induced astigmatism in canines following sutured dorsonasal vs dorsotemporal clear corneal incisions

Pederson

Cleymaet

Hess

et al. 2019

Veterinary Ophthalmology

View full text Add to dashboard Cite

Objectives: To investigate use of the Pentacam® HR for evaluation of surgically induced corneal astigmatism (SIA) in canines undergoing bilateral phacoemulsification and determine differences between dorsonasal and dorsotemporal clear corneal incisions. Animals: Client-owned canines undergoing bilateral phacoemulsification. Procedures: Patients received anterior segment imaging pre-operatively, immediately post-operatively, and 2-4 months post-operatively (follow-up). Total corneal refractive power was used to determine SIA. Surgically induced astigmatism was compared between right and left eyes, representing dorsotemporal and dorsonasal incisions, respectively. Repeated measures analyses were used between time points and paired t test compared SIA between eyes. Results: Complete imaging series were obtained for seven patients. Follow-up imaging occurred at a median of 112 days (range 60-132 days) post-operatively. For repeated measures analyses, significant differences were found between pre-and immediate post-operative values (P < 0.01), and between immediate post-operative and follow-up values (P < 0.01). There was no significant difference between preoperative and follow-up values. Surgically induced astigmatism was significantly different between right and left eyes, with values of 2.01 ± 1.24 D and 3.05 ± 1.58 D at 3 mm radius (P < 0.05), and 2.04 ± 1.18 D and 3.06 ± 1.27 D at 4 mm radius (P < 0.05) for dorsotemporal and dorsonasal incisions, respectively. Conclusions: Preliminary investigation revealed improvement of corneal SIA 2-4 months post-operatively, but development of significantly more SIA in dorsonasal vs dorsotemporal incisions. This prompts consideration of patient or microscope rotation to create a more dorsotemporal incision when possible. K E Y W O R D S canine, clear corneal incision, cornea, Pentacam, phacoemulsification, surgically induced astigmatism 800 | PEDERSON Et al.

show abstract

Assessing the corneal power change after refractive surgery using Scheimpflug imaging

Abstract: Ray tracing calculations based on Scheimpflug imaging accurately assessed the change in manifest refraction due to corneal laser surgery.

Cited by 25 publications

References 30 publications

Refractive Correction and Biomechanical Strength Following SMILE With a 110- or 160-μm Cap Thickness, Evaluated Ex Vivo by Inflation Test

Refractive Correction and Biomechanical Strength Following SMILE With a 110- or 160-μm Cap Thickness, Evaluated Ex Vivo by Inflation Test

Calculations of actual corneal astigmatism using total corneal refractive power before and after myopic keratorefractive surgery

Surgically induced astigmatism in canines following sutured dorsonasal vs dorsotemporal clear corneal incisions

Contact Info

Product

Resources

About