Sources of Error in Toric Intraocular Lens Power Calculation.

Purpose: To evaluate the influencing factors on remaining astigmatism after implanting a toric intraocular lens (IOL) during cataract surgery.

Methods: This retrospective study included parameters that were considered to have an influence on toric IOL power calculation. Therefore, data from the literature and the authors' own data were used.

Prediction of the true IOL position.

Purpose: To develop algorithms for preoperative estimation of the true postoperative intraocular lens (IOL) position to be used for IOL power calculation.

Setting: Moorfields Eye Hospital NHS Foundation Trust, London, UK.

Methods: Fifty patients were implanted randomly with a 3-piece IOL model in one eye and a 1-piece model in the other eye.

Using continuous intraoperative optical coherence tomography measurements of the aphakic eye for intraocular lens power calculation.

Background/aims: To include intraoperative measurements of the anterior lens capsule of the aphakic eye into the intraocular lens power calculation (IPC) process and to compare the refractive outcome with conventional IPC formulae.

Methods: In this prospective study, a prototype operating microscope with an integrated continuous optical coherence tomography (OCT) device (Visante attached to OPMI VISU 200, Carl Zeiss Meditec AG, Germany) was used to measure the anterior lens capsule position after implanting a capsular tension ring (CTR). Optical biometry (intraocular lens (IOL) Master 500) and ACMaster measurements (Carl Zeiss Meditec AG, Germany) were performed before surgery.

Fluctuations in corneal curvature limit predictability of intraocular lens power calculations.

Purpose: To analyze fluctuations in corneal curvature over time.

Setting: Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.

Design: Case series.

Sources of error in intraocular lens power calculation.

Purpose: To identify and quantify sources of error in the refractive outcome of cataract surgery.

Setting: AMO Groningen BV, Groningen, The Netherlands.

Methods: Means and standard deviations (SDs) of parameters that influence refractive outcomes were taken or derived from the published literature to the extent available.

Model eyes for evaluation of intraocular lenses.

In accordance with the present international standard for intraocular lenses (IOLs), their imaging performance should be measured in a model eye having an aberration-free cornea. This was an acceptable setup when IOLs had all surfaces spherical and hence the measured result reflected the spherical aberration of the IOL. With newer IOLs designed to compensate for the spherical aberration of the cornea there is a need for a model eye with a physiological level of spherical aberration in the cornea.

Theoretical comparison of aberration-correcting customized and aspheric intraocular lenses.

Purpose: To assess the performance and optical limitations of standard, aspheric, and wavefront-customized intraocular lenses (IOLs) using clinically verified pseudophakic eye models.

Methods: White light pseudophakic eye models were constructed from physical measurements performed on 46 individual cataract patients and subsequently verified using the clinically measured contrast sensitivity function (CSF) and wavefront aberration of pseudophakic patients implanted with two different types of IOLs. These models are then used to design IOLs that correct the astigmatism and higher order aberrations of each individual eye model's cornea and to investigate how this correction would affect visual benefit, subjective tolerance to lens misalignment (tilt, decentration, and rotation), and depth of field.

Development of an accommodating intra-ocular lens--in vitro prevention of re-growth of pig and rabbit lens capsule epithelial cells.

Cataract surgery is routinely performed to replace the clouded lens by a rigid polymeric intra-ocular lens unable to accommodate. By implanting a silicone gel into an intact capsular bag the accommodating properties of the natural lens can be maintained or enhanced. The implantation success of accommodating lenses is hampered by the occurrence of capsular opacification (PCO) due to lens epithelial cell (LEC) growth.

Accommodative lens refilling in rhesus monkeys.

Purpose: Accommodation can be restored to presbyopic human eyes by refilling the capsular bag with a soft polymer. This study was conducted to test whether accommodation, measurable as changes in optical refraction, can be restored with a newly developed refilling polymer in a rhesus monkey model. A specific intra- and postoperative treatment protocol was used to minimize postoperative inflammation and to delay capsular opacification.

Artificial crystalline lens.

If presbyopia is caused by hardening of the crystalline lens, replacing it with a material with mechanical properties similar to the young crystalline lens should restore accommodative ability. Such a silicone material has been developed. Refilling the capsular bag with this material results in 3 to 5 D of accommodation in primates in response to pilocarpine.

Clinical application of the lens haptic plane concept with transformed axial lengths.

Purpose: To clinically evaluate the lens haptic plane (LHP) concept in combination with thick-lens ray tracing for intraocular lens (IOL) power calculation.

Setting: St. Erik's Eye Hospital, Stockholm, Sweden.

The Dubbelman eye model analysed by ray tracing through aspheric surfaces.

Dubbelman and co-workers have determined intraocular spacings and surface shapes in living eyes by means of corrected Scheimpflug images in a large number of subjects of different age at several levels of accommodation. They give relationships for key anterior segment parameters as a function of age and level of accommodation. These are used in this paper to build a schematic eye incorporating aspheric surfaces.

Adaptive optics simulation of intraocular lenses with modified spherical aberration.

Purpose: Adaptive optics systems can be used to investigate the potential visual benefit associated with correcting ocular wave-front aberration. In this study, adaptive optics techniques were used to evaluate the potential advantages and disadvantages associated with intraocular lenses (IOLs) with modified spherical aberration profiles.

Methods: An adaptive optics vision simulator was constructed that allows psychophysical tests to be performed while viewing targets through any desired ocular wave-front profile.

Using the lens haptic plane concept and thick-lens ray tracing to calculate intraocular lens power.

Purpose: To develop a methodology for intraocular lens (IOL) power calculation in which the task of predicting the postoperative position of the IOL is separated from the calculation itself.

Setting: Pharmacia, Groningen, The Netherlands.

Methods: The minimum biometry input needed for IOL power calculation is the mean anterior corneal radius and axial length of the eye.

Effect of methods of myopia correction on visual acuity, contrast sensitivity, and depth of focus.

Purpose: To psychophysically measure spherical and irregular aberrations in patients with various types of myopia correction.

Setting: Laboratory of Experimental Ophthalmology, University of Groningen, Groningen, The Netherlands.

Methods: Three groups of patients with low myopia correction (spectacles, soft contact lens, and Intacs) and 4 groups with high myopia correction (spectacles, rigid contact lens, Artisan claw lens, and laser in situ keratomileusis [LASIK]) had through-focus contrast sensitivity measurements to establish the myopic shift and depth of focus.

Effect of intraocular lens implantation on visual acuity, contrast sensitivity, and depth of focus.

Purpose: To determine the role of spherical and irregular aberrations in the optics of the natural eye and after intraocular lens (IOL) implantation in terms of visual acuity, contrast sensitivity, and depth of focus.

Setting: Laboratory of Experimental Ophthalmology, University of Groningen, Groningen, The Netherlands.

Methods: Visual acuity and defocus-specific contrast sensitivity in 11 pseudophakic patients (IOL group) and 27 age-matched phakic subjects were compared.

Hydrogels for an accommodating intraocular lens. An explorative study.

In this study it was investigated whether hydrogels could be used for an accommodating lens. The requirements of such a hydrogels are a low modulus, high refractive index, transparency, and strength. Since conventional hydrogels do not possess this combination of properties, a novel preparation method and new polymers are introduced.

Reduction of trend errors in power calculation by linear transformation of measured axial lengths.

Purpose: To find a method to improve the refractive outcome in short eyes and long eyes without sacrificing the outcome in normal eyes.

Setting: St. Erik's Eye Hospital, Stockholm, Sweden.