Simple method for accurate alignment in toric phakic and aphakic intraocular lens implantation

J.K., Joseph; Tseng, Santos Shan-Yu

doi:10.1016/j.jcrs.2008.04.041

Cited by 108 publications

(93 citation statements)

References 19 publications

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“…1 Vetter et al measured the changes in intraocular pressure (IOP) during lamellar fl ap creation using four different femtosecond lasers. We also analyzed IOP changes that occur during both external eye compression and fl ap creation in an animal model, [2][3][4] and we would like to address the method used by Vetter et al in their study.…”

Section: Measurement Of Intraocular Pressure During Corneal Flap Prepmentioning

confidence: 99%

A Simple, Reproducible, and Cost Effective Axis Marking System for Toric Lens Implantation

Roumeliotis¹,

Hutnik²

2012

J Refract Surg

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issue of Journal of Refractive Surgery.1 Vetter et al measured the changes in intraocular pressure (IOP) during lamellar fl ap creation using four different femtosecond lasers. We also analyzed IOP changes that occur during both external eye compression and fl ap creation in an animal model, 2-4 and we would like to address the method used by Vetter et al in their study.Vetter et al measured IOP in the vitreous cavity using a needle inserted through the optic nerve. However, as found in previous studies of our own, we believe the vitreous cavity may not be the most appropriate place to measure IOP when a cannulation method is used. In our fi rst study, 2 a signifi cant difference was found in IOP measured in the anterior chamber versus the vitreous cavity. Furthermore, we found that IOP measured within the vitreous cavity during the external IOP-increase induction was close to the IOP measured in the anterior chamber during the fi rst seconds of the procedure. Afterwards, IOP in the vitreous cavity reached a "plateau," while IOP in the anterior chamber continued to rise. As the cannulation method of measuring IOP depends on the liquid fl ow through the cannula and tubes, the high viscous nature of the vitreous gel may occlude or decrease the fl ow within the lumen of the cannula placed in the vitreous cavity. This fi nding may be one reason for these differences in IOP measured between the anterior chamber and vitreous cavity.We believe we have provided evidence to suggest that the anterior chamber is a better place to monitor the changes in IOP due to surgical maneuvers. Intraocular pressure recorded in the vitreous cavity (with a cannula) is lower, and thus less sensitive to changes in IOP. Therefore, we do not believe that using the vitreous cavity for cannulation is the best way to detect differences in intraoperative IOP changes among several surgical devices. Reply:We thank Drs Hernández-Verdejo and Teus for their comments and agree that the vitreous body can occlude cannulas of 20 or 21 gauge size. This leads to false pressure recordings if the pressure is measured by an external pressure transducer via the cannula. As a consequence, the obtained pressure curve shows a "plateau-like" shape with no sudden changes. This happened frequently during our measurements of intraocular pressure (IOP) in porcine eyes.1,2 However, only measurements with a continuously unblocked cannula were included in the studies. This was assured by two control mechanisms.First, prior to each measurement, the cannula was inserted through the optic nerve and a discrete indentation was applied to the globe. A sharp peak in the pressure curve could be observed if the cannula was unblocked. In cases of blockage, the needle was extracted, fl ushed with saline, reinserted through the same entrance, and the insertion site was sealed with histoacrylic glue. If this happened twice, a new porcine globe was used.Second, during each measurement, the pressure curve was continuously evaluated for plateaus and for "missing" sudden pressure chang...

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Section: Measurement Of Intraocular Pressure During Corneal Flap Prepmentioning

confidence: 99%

A Simple, Reproducible, and Cost Effective Axis Marking System for Toric Lens Implantation

Roumeliotis¹,

Hutnik²

2012

J Refract Surg

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“…[5][6][7] The surgical procedure of astigmatism correction often begins with alignment and axis marking of eyes while sitting at the slit lamp. Various preoperative marking and surgical techniques [8][9][10] have been introduced for precise positioning of toric IOLs, and a new intra-operative technology placing an angular scale display within the surgical microscope has recently been introduced to the market (SMI Surgery Guidance, SensorMotoric Instruments, Teltow, Germany). Manual keratometry, automated keratometry, and partial coherence interferometry are the most common instruments being used to measure keratometric values before cataract surgery.…”

Section: Introductionmentioning

confidence: 99%

The effect of head tilt on keratometric measurement using the IOLMaster

Park

Kim

et al. 2013

Eye

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Purpose To investigate the effect of head tilt on keratometric measurement using the IOLMaster. Methods Twenty-seven right eyes of 27 volunteers were examined using a manual keratometer (MK), automated keratometer (AK), and an IOLMaster. MK and AK measurements were performed in the upright head position, whereas IOLMaster measurements were performed in five different head positions (upright, 51 or 151 clockwise head tilt, and 51 or 151 counter-clockwise head tilt). The repeatability of IOLMaster was compared with MK and AK. The keratometric measurements (mean keratometric power, magnitude of astigmatism, and steep meridian) in different head positions were compared. Results The IOLMaster showed good repeatability of keratometric measurement comparable to MK or AK. 151 and 51 clockwise head tilt resulted in 12.09 ± 9.51 (mean ± SD) (Po0.001 vs upright) and 5.51 ± 5.97 (mean ± SD) degrees (Po0.001) of clockwise rotation of steep meridian, respectively. 151 and 51 counter-clockwise head tilt resulted in 12.49±7.07 (mean±SD) (Po0.001) and 6.08±5.09 (mean±SD) degrees (Po0.001) of counter-clockwise rotation of steep meridian, respectively. Conclusions The patient's head tilt (51 or 151, clockwise or counter-clockwise) significantly changed the steep meridian of astigmatism measured using IOLMaster and the steep meridian generally shifted to the direction of head tilt. The importance of maintaining the upright head posture during IOLMaster measurement is demonstrated.

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“…They promise a predictable method of astigmatic correction with minimal impact to the cornea, 17 however, the effectiveness of a toric IOL is dependent on its orientation. The relationship between misalignment and resultant residual astigmatism is sinusoidal and small misalignments have a relatively large effect on correction than large misalignments 18 ( Figure 1). If the axis of a toric IOL is misaligned by 30°, no correction of the magnitude of astigmatism occurs, however, there is a shift in the resultant astigmatic axis.…”

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confidence: 99%

Surgical correction of astigmatism during cataract surgery

Buckhurst

Wolffsohn

Davies

et al. 2010

Clinical and Experimental Optometry

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High levels of corneal astigmatism are prevalent in a significant proportion of the population. During cataract surgery pre-existing astigmatism can be corrected using single or paired incisions on the steep axis of the cornea, using relaxing incisions or with the use of a toric intraocular lens. This review provides an overview of the conventional methods of astigmatic correction during cataract surgery and in particular, discusses the various types of toric lenses presently available and the techniques used in determining the correct axis for the placement of such lenses. Furthermore, the potential causes of rotation in toric lenses are identified, along with techniques for assessing and quantifying the amount of rotation and subsequent management options for addressing postoperative rotation. Correcting corneal astigmatism during cataract surgery can increase spectacle independence. For the patient, this has economic benefits 4 as well as desirable cosmetic and practical advantages. Spectacle correction of astigmatism creates meridional magnification, which when coupled with the associated back vertex distance produces retinal images that are asymmetrically magnified and distorted. Such images have been reported to reduce spatial perception 5 and adaptation to them is particularly challenging for elderly individuals, 6 in whom cataracts are more prevalent. Contrary to this, if corneal astigmatism is corrected at the corneal or intraocular lens (IOL) plane, then no significant meridional magnification is induced due to a negligible vertex distance. 7The effect of clear corneal incisions (CCIs) on surgically-induced astigmatism has been extensively examined. If placed along the steep corneal axis, the clear corneal incisions flatten the cornea, reducing the residual astigmatism. The larger the clear corneal incision, the greater the flattening effect. 8 Studies have shown that the average surgically induced astigmatism using a 3.0 to 3.2 mm clear corneal incision is~0.50 D.9,10 The temporal cornea allows easy access for incisions and is the preferred site of most surgeons, 11 however, incisions performed on the steepest axis result in superior postoperative uncorrected vision.12 Opposite clear corneal incisions require a second clear corneal incision to be placed along the steep axis of the cornea on the opposing side of the pupil. This has a larger effect than a single clear corneal incision and can correct more than one dioptre of corneal astigmatism.13,14 Limbal relaxing incisions, otherwise known as peripheral corneal relaxing incisions, can also be used to correct astigmatism C L I N I C A L A N D E X P E R I M E N T A LOPTOMETRY

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Simple method for accurate alignment in toric phakic and aphakic intraocular lens implantation

Cited by 108 publications

References 19 publications

A Simple, Reproducible, and Cost Effective Axis Marking System for Toric Lens Implantation

A Simple, Reproducible, and Cost Effective Axis Marking System for Toric Lens Implantation

The effect of head tilt on keratometric measurement using the IOLMaster

Surgical correction of astigmatism during cataract surgery

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