Underestimation of intraocular lens power for cataract surgery after myopic photorefractive keratectomy

Seitz, Berthold; Langenbucher, Achim; Nguyen, Nhung X.; Kus, Murat M.; Küchle, Michael

doi:10.1016/s0161-6420(99)90153-7

Cited by 234 publications

(151 citation statements)

References 47 publications

Supporting

Mentioning

131

Contrasting

Unclassified

Order By: Relevance

“…Não sabemos ainda se nas cór-neas submetidas às cirurgias refrativas existe alguma correlação. Sabemos sim que estas cirurgias modificam a superfície anterior e a espessura e que poderiam também alterar indiretamente a superfície posterior da córnea (11)(12)16) , e tornar, portanto, o uso do IRC impróprio nesses casos (1)(2)7,(17)(18) . …”

Section: Discussionunclassified

O cálculo do poder das lentes intra-oculares e o Orbscan-II. Parte 1: O poder óptico da córnea normal

Oliveira¹,

Arce²,

Campos³

et al. 2003

Arq. Bras. Oftalmol.

View full text Add to dashboard Cite

0,8361) nas quatro áreas centrais analisadas (0,04, 1, 3 e 5 mm de diâmetro). O poder médio posterior diminuiu de -6,62 D até -6,35 D (p=0,0030). A espessura média aumentou de 524 µm até 554 µm (p=0,0231), representando 0,13 D do poder total da córnea. Os poderes óptico (p<0,0167), axial (p<0,0099) e médio (p<0,0030) ceratométricos foram aproximadamente 1,50 D mais positivos que os respectivos poderes totais. O poder médio total foi igual ao poder equivalente (p>0,4907) e à soma do poder de ambas superfícies (p>0,3868). O poder médio anterior foi ao redor de 7,5 vezes maior que o poder médio posterior. CONCLUSÕES: O poder real da córnea calculado usando ambas superfícies, sua espessura e os índices de refração fisiológicos é menor que o poder convencionalmente aceito e determinado pela medição da curvatura da superfície anterior e o índice de refração ceratométrico da córnea (F

show abstract

Section: Discussionunclassified

O cálculo do poder das lentes intra-oculares e o Orbscan-II. Parte 1: O poder óptico da córnea normal

Oliveira¹,

Arce²,

Campos³

et al. 2003

Arq. Bras. Oftalmol.

View full text Add to dashboard Cite

show abstract

“…3,4,[19][20][21][22][23] The spherical equivalent change is subtracted from the original corneal refractive power. However, accurate pre-refractive data as well as a stable postoperative refraction are necessary.…”

Section: -13mentioning

confidence: 99%

“…However, there are reports indicating that refractive outcome using corneal topography has not been satisfying. 3,22 Unfortunately, corneal topography and keratometry systems calculate the refractive corneal power using a standardized refractive index (eg 1.3375) to convert corneal radii into dioptres. As the relationship between anterior and posterior surface of the cornea is changed by the excimer laser treatment, topography or keratomety values should be modified.…”

Section: -13mentioning

confidence: 99%

“…1,2 Corneal power is overestimated followed by an underestimation of IOL power resulting in hyperopia postoperatively. 3,4 Moreover, this overestimation of K-readings is increased by a reduced refractive corneal index, which is determined by the two refractive surfaces of the cornea. Removing tissue using an excimer laser alters the relationship between anterior and posterior surface.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Intraocular lens power calculation using ray tracing following excimer laser surgery

Rabsilber

Reuland

Holzer

et al. 2006

Eye

View full text Add to dashboard Cite

Purpose To evaluate intraocular lens (IOL) power calculation using ray tracing in patients presenting with cataract after excimer laser surgery. Methods Ten eyes of seven consecutive patients who presented for cataract surgery following excimer laser treatment without any pre-refractive biometry data were enrolled in this prospective clinical study. Preoperatively, IOL power calculation was performed using a ray tracing software called OKULIX. Keratometry data (C-Scan) were imported and axial length (IOLMaster) was entered manually. Accuracy of IOL power calculation was investigated by subtracting attempted and achieved spherical equivalent. Conclusions IOL power calculation after excimer laser surgery can be difficult, especially when pre-refractive keratometry values are not available. In these cases, ray tracing combined with corneal topography measurements provides reliable and satisfactory postoperative results. However, it is advisable to be careful when calculating IOL power for eyes with corneal radii exceeding 10 mm because of slightly higher prediction errors.

show abstract

“…The net effect of this is to underestimate the IOL power required, resulting in relative postoperative hyperopic refraction. 2 The Orbscan II (Orbtek, Salt-Lake City, UT, USA) is a scanning slit-beam topographer that measures posterior corneal elevation and thereby curvature. If this measurement were to be validated, then determination of corneal power after refractive surgery would be greatly simplified.…”

Section: Introductionmentioning

confidence: 99%

Validation of Orbscan II posterior corneal curvature measurement for intraocular lens power calculation

Leyland

2004

Eye

View full text Add to dashboard Cite

Aims To validate the use of Orbscan II slitscanning topography for measuring posterior corneal curvature, by comparing corneal power calculations using this value with the standard keratometric method of corneal power calculation. Method Corneal measurements were taken from both eyes of 15 normal subjects using the Javal-Schiotz keratometer and the Orbscan II topographer. Corneal power was calculated using standard keratometric indices of 1.337.5 or 1.331.5 and Javal-Schiotz keratometry. Corneal power was then recalculated using the thick-lens formula, with anterior corneal curvature from the Javal-Schiotz or Orbscan II and posterior measurements from the Orbscan II; in addition, the 3.0 mm 'Mean Power' value from the Orbscan II software was noted. Six comparisons were then made using meandifference plots. Results The smallest difference and therefore the most predictable agreement was between Javal-Schiotz keratometry using a refractive index of 1.331.5 and the thick-lens formula using Javal-Schiotz anterior curvature and Orbscan II posterior curvature. The mean difference was 0.27 D with a confidence interval of 0.02-0.52 D. Conclusions In normal eyes, data on posterior corneal curvature from the Orbscan II can be used to calculate corneal power in close agreement with the standard keratometric method. This suggests the use of the Orbscan II in eyes that have previously undergone refractive surgery, for calculation of intraocular lens power prior to cataract surgery.

show abstract

Underestimation of intraocular lens power for cataract surgery after myopic photorefractive keratectomy

Cited by 234 publications

References 47 publications

O cálculo do poder das lentes intra-oculares e o Orbscan-II. Parte 1: O poder óptico da córnea normal

O cálculo do poder das lentes intra-oculares e o Orbscan-II. Parte 1: O poder óptico da córnea normal

Intraocular lens power calculation using ray tracing following excimer laser surgery

Validation of Orbscan II posterior corneal curvature measurement for intraocular lens power calculation

Contact Info

Product

Resources

About