[Optical performance of multifocal intraocular lenses. Investigation of the Array SA40N vs. Acri. Twin at the "physical eye" according to Reiner and Jacobi]. / Abbildungseigenschaften multifokaler Intraokularlinsen. Untersuchung der Array SA40N vs. Acri.Twin am "physikalischen Auge" nach Reiner und Jacobi.

BACKGROUND: Reduced contrast sensitivity, glare disability and insufficient bifocality are the main drawbacks of multifocal intraocular lenses (IOL). The bilateral implantation of diffractive IOL with an asymmetrical light distribution for distance and near focus is an alternative concept that aims to improve the contrast sensitivity and bifocality of conventional multifocal IOL. PATIENTS AND METHODS: The optical performance of monofocal (PhacoFlexII SI40) and multifocal IOL (Array SA40N; Acri. Twin 737D/733D) was quantitatively assessed in 18 healthy probands and qualitatively determined by digital photographic recording using an optical apparatus, the "physical eye", according to Reiner and Jacobi. Vision examination included standard tests of distance and near visual acuity, contrast sensitivity and low contrast visual acuity testing under varying pupil size using a video acuity tester. RESULTS: Distance visual acuity was significantly superior with the SI40 and distant-dominant 737D compared to the SA40N and near-dominant 733D. At near, the 733D had the best performance. Contrast sensitivity was better with the 737D than the SA40N when both were compared with the SI40. No normal contrast sensitivity could be determined with the 733D because of the optical phenomenon of 'spurious resolution'. Variation in pupil size had less impact on contrast acuity with the Acri. Twin IOL compared to the SI40 and SA40N. Photographic testing revealed better edge contrast with the Acri. Twin than the SA40N. CONCLUSIONS: The optical performance of multifocal IOL correlates with the properties of physical light distribution. Differences in edge contrast may be discerned using photographic recording.

A genetic perspective on myopia.

Myopia is a refractive error of the eye that has a significant socioeconomic impact due to its increasing prevalence and the fact that it causes visual impairment. Its aetiology is complex and is likely to involve the interaction of environmental and genetic influences. Tight environmental influence is exemplified by defocus-induced myopia produced in animal models, while genetic factors predominate in familial occurrence of myopia with a Mendelian inheritance pattern. The involvement of numerous mediators, such as cytokines, neurotransmitters and transcription factors, in myopia development has been indicated through various lines of investigation, particular interest focussing on scleral extracellular matrix proteins and developmental genes of the eye. As high-throughput technology for large-scale genotyping and RNA expression analysis enters the field of myopia research, a productive avenue will open up for deciphering the aetiological heterogeneity of myopia and the biological pathways underlying its development.

A novel mutation of the RP1 gene (Lys778ter) associated with autosomal dominant retinitis pigmentosa.

BACKGROUND: Besides the three known genes (RHO, RDS/Peripherin, NRL) involved in autosomal dominant retinitis pigmentosa (adRP), a fourth gene, RP1, has been recently identified. Initial reports suggest that mutations in the RP1 gene are the second most frequent cause of adRP. The clinical findings were described in a family with adRP and a novel mutation in the RP1 gene. METHOD: Index patients from 15 independent families with adRP in which RHO mutations had been excluded in previous examinations were screened for mutations in the RP1 gene by means of direct DNA sequencing. Evaluation of the RP1 phenotype in patients included funduscopy, kinetic perimetry, dark adapted final threshold test, standard electroretinography and, in one case, multifocal electroretinography. RESULTS: One novel nonsense mutation (Lys778ter) in one of these 15 patients was detected. Cosegregation of the mutation with the disease phenotype could be established in the index patient's family. The phenotype comprises variable expression of clinical disease probably including one case of incomplete penetrance, a onset of symptoms beginning in adulthood, and evidence of regionally varying retinal function loss. CONCLUSION: The Lys778ter mutation localises inside the critical region harbouring all mutations described so far. The ophthalmic findings support previous observations that variation of disease expression appears as a typical feature of the RP1 phenotype.

Cataract surgery under topical anesthesia in patients with coexisting glaucoma.

PURPOSE: To evaluate and compare levels of patient discomfort and complications during phacoemulsification with implantation of a foldable intraocular lens (IOL) under topical lidocaine hydrochloride in patients with and without various forms of chronic open-angle and chronic angle-closure glaucoma. SETTING: Two university eye centers in Germany. METHODS: This prospective nonrandomized comparative study comprised 176 eyes of 176 patients with various forms of chronic open-angle glaucoma and chronic angle-closure glaucoma. Eyes with cataract and without a glaucoma diagnosis or history of intraocular surgery served as a control group (n = 212). All patients received a minimum of 5 doses (2 drops per dose) of topical lidocaine hydrochloride 2% before standard temporal clear corneal phacoemulsification and foldable IOL implantation. No intracameral anesthetic injection was given, and no systemic sedatives were used. The main outcome measures were the number of complications and adverse events. RESULTS: The intraoperative complication rate in all patients (n = 388) was capsule tear, 1.3%; zonule tear, 1.8%; vitreous loss, 1.0%; iris prolapse, 0.8%. No statistically significant differences in intraoperative or early postoperative complications were found between the glaucoma and control groups. The mean pain scores of patients were 0.38 +/- 1.1 (SD) in the glaucoma group and 0.36 +/- 0.8 in the control group (P =.21) Patient preference for cataract surgery under topical anesthesia was similar in both groups. CONCLUSIONS: Surgery-related complications and patient discomfort were similar in patients with and without glaucoma who had phacoemulsification and IOL implantation under topical anesthesia. These results indicate that topical anesthesia is safe for routine phacoemulsification with foldable IOL implantation in patients with glaucoma and does not compromise patient comfort.

Case populations must match the respective disease model: Genotype diversity causes linkage disequilibrium mapping failure in monogenic disorders.

Traditional linkage analysis in large families is the most promising approach for mapping disease genes of monogenic heritable disorders when the number of informative meioses is sufficient. With rare diseases, however, the low availability of informative pedigrees poses a significant limitation. As an adjunct to family linkage methods, association studies based on the investigation of individual haplotypes from a number of unrelated patients (i.e. linkage disequilibrium analysis) have recently been employed in mapping hereditary disease loci. However, such haplotype analysis is hampered by a number of effects that influence statistical evaluation, e.g. i) population history and size, ii) allele and haplotype frequencies in the respective population(s), iii) heterogeneous mutation and natural selection processes, and iv) small sample sizes of patient groups. The purpose of the present study was to determine the utility and limitations of haplotype-based genetic mapping in estimating the location of the NYX gene, which has recently been identified as the causative gene for a rare inherited retinal disorder known as the complete type of X-linked congenital stationary night blindness (CSNB1). For this purpose we recapitulated haplotypes and tested for linkage disequilibrium in 20 unrelated male CSNB1 patients from three European populations and 44 healthy individuals. All subjects were genotyped for 17 polymorphic microsatellite loci covering the Xp11.4 region with an average marker density of approximately 0.29 cM. We found that a precise model to describe mutations at loci that erroneously break up linkage is highly required, and that the case population must match the respective disease model.

Quantitation of heteroplasmy in mitochondrial DNA mutations by primer extension using Vent(R)(exo-) DNA polymerase and RFLP analysis.

In this report we describe a simple and rapid protocol for reliable quantitation of mitochondrial DNA (mtDNA) mutations, which is basically a modification of the traditional polymerase chain reaction (PCR)/restriction fragment length polymorphism (RFLP) analysis technique. Up to now, the PCR/RFLP method has been of limited use for the accurate determination of ratios of mutant and wild type molecules, largely owing to the formation of heteroduplex molecules by PCR and incompleteness of restriction digestion. In order to overcome this problem, we have introduced a single-step primer extension reaction using Vent(R)(exo-) DNA polymerase and a fluorescence-labeled primer to the standard assay. The labeled homoduplex molecules are then digested with a restriction endonuclease, and the nucleic acids fractionated on an automated DNA sequencer equipped with GENESCAN analysis software. The amount of mutant mtDNA is readily estimated from fluorescence intensities of the wild-type and mutant mtDNA fragments corrected for incomplete digestion as monitored by a homologous control fragment. The accuracy of the improved protocol was determined by constructing standard curves obtained from defined mixtures of genomic DNA containing homoplasmic wild-type and mutant mtDNA. The expected values were obtained, with an observed correlation coefficient of 0.997 and a typical variability of +/-5% between repeated measurements. Further validation of the protocol is provided by the screening of five patients and unaffected subjects carrying the guanine to adenine transition at the nucleotide 3460 of the mitochondrial genome responsible for the mitochondrial disorder of Leber's hereditary optic neuropathy.

Segregation patterns and heteroplasmy prevalence in Leber's hereditary optic neuropathy.

PURPOSE: To investigate the segregation pattern of the mitochondrial DNA mutation at nucleotide position 3460 responsible for Leber's hereditary optic neuropathy (LHON) and to determine the prevalence of heteroplasmy for the three primary LHON mutations at positions 11778, 3460, and 14484. METHODS: Segregation analysis was performed in a cross-sectional study by determining the level of heteroplasmy in blood leukocytes of 23 LHON patients and unaffected carriers from four unrelated families. One family comprising two affected and three unaffected carriers was followed over 5.5 years for a longitudinal segregation analysis of heteroplasmy. The percentage of mutant mtDNA was determined using a novel procedure of fluorescence-based primer extension and restriction fragment length polymorphism analysis. The prevalence of heteroplasmy was assessed by determining the number of genealogically unrelated LHON pedigrees with heteroplasmic maternal family members from the LHON patient records of the Department of Ophthalmology, University of Tübingen, Germany. RESULTS: The authors observed a marked variability in the degree of heteroplasmy levels within each pedigree and a tendency toward a higher mutant allele frequency in offspring generations. Disease expression was correlated with higher levels of mutant mtDNA molecules. Longitudinal analysis revealed no statistically significant decrease in the heteroplasmy level in the family studied but a reduction of 11% and 12% in one affected and one unaffected individual, respectively. In 167 genealogically unrelated LHON families the prevalence of heteroplasmy was 5.6%, 40%, and 36.4% for the 11778, 3460, and 14484 LHON mutations, respectively. CONCLUSIONS: Cross-sectional studies of heteroplasmy for the 3460 LHON mutation suggest that the genotype shifts toward a higher mutational load in offspring generations. Long-term decrease in the blood mutant load in single cases indicates negative selection of the mutant allele in the hematopoietic cell system. The prevalence of heteroplasmy varies significantly between the different primary LHON mutations, suggesting genotypical differences in disease expression.

Complete form of X-linked congenital stationary night blindness: refined mapping and evidence of genetic homogeneity.

A number of distinct, partly non-overlapping genetic loci have been reported for the complete type of X-linked congenital stationary night blindness (CSNB1), suggesting genetic heterogeneity. In order to refine the localization of the CSNB1 gene and to demonstrate genetic homogeneity, linkage analysis was performed in two large CSNB1 families. Clinical features consistent with the diagnosis of CSNB1 were documented in five patients from a German seven-generation kindred by full ophthalmological examination including psychophysical and electroretinographical testing. Haplotype analysis in 30 members of the large German family was performed with 38 polymorphic markers predominantly covering the critical region. Linkage analyses defined a locus for CSNB1 with flanking markers DXS8042 and DXS228, refining the interval to 2.5 cM in Xp11.4. In addition, two-point linkage analysis was carried out using the MLINK computer program. In agreement with meiotic breakpoints, lod scores of 3.0 and greater were obtained for markers located to the proximal site of the former 5 cM CSNB consensus interval. A large Dutch CSNB1 family was re-evaluated with markers from the Xp11.4 region, and supports the CSNB1 minimal interval found in the German family. Together with previous results from three unrelated families from Sweden, Sardinia and Great Britain, our results provide evidence of genetic homogeneity in the disorder. Subsequent mutation analyses in CSNB1 patients revealed no pathogenic sequence alterations in DFFRX and CASK genes, but retain candidates for other diseases mapping to that region.

The complete form of X-linked congenital stationary night blindness is caused by mutations in a gene encoding a leucine-rich repeat protein.

X-linked congenital stationary night blindness (XLCSNB) is characterized by impaired scotopic vision with associated ocular symptoms such as myopia, hyperopia, nystagmus and reduced visual acuity. Genetic mapping in families with XLCSNB revealed two different loci on the proximal short arm of the X chromosome. These two genetic subtypes can be distinguished on the basis of electroretinogram (ERG) responses and psychophysical testing as a complete (CSNB1) and an incomplete (CSNB2) form. The CSNB1 locus has been mapped to a 5-cM linkage interval in Xp11.4 (refs 2,5-7). Here we construct and analyse a contig between the markers DXS993 and DXS228, leading to the identification of a new gene mutated in CSNB1 patients. It is partially deleted in 3 families and mutation analysis in a further 21 families detected another 13 different mutations. This gene, designated NYX, encodes a protein of 481 amino acids (nyctalopin) and is expressed at low levels in tissues including retina, brain, testis and muscle. The predicted polypeptide is a glycosylphosphatidylinositol (GPI)-anchored extracellular protein with 11 typical and 2 cysteine-rich, leucine-rich repeats (LRRs). This motif is important for protein-protein interactions and members of the LRR superfamily are involved in cell adhesion and axon guidance. Future functional analysis of nyctalopin might therefore give insight into the fine-regulation of cell-cell contacts in the retina.

Physical mapping and exclusion of GPR34 as the causative gene for congenital stationary night blindness type 1.

X-linked congenital stationary night blindness (CSNB) is a nonprogressive retinal disorder characterized by impaired night vision, variably involving high myopia, nystagmus, decreased visual acuity, and strabismus. Linkage studies have identified two distinct loci for X-linked CSNB1 and CSNB2 on the short arm of chromosome X. The gene mutated in families displaying the "incomplete phenotype" of CSNB (i.e., CSNB2) has recently been identified. To identify novel candidate genes for the "complete form" of CSNB (i.e., CSNB1) we screened the physically vast region Xp11.3-Xp11.4 for cDNA sequences. This led us to identify and map the G protein coupled receptor (GPCR) gene GPR34 to Xp11.4 within 650 kb of the marker DXS993. Deletion screening via Southern blotting and direct sequencing of GPR34 revealed no mutations in 19 unrelated men with CSNB1, excluding a causal role in the disease. However, because of its expression in retinal and neural tissue and the involvement of GPCRs in transmembrane signal transduction, GPR34 remains a putative candidate gene for a number of ocular diseases which also map to the Xp11.4 region.

A comparative study of topical vs retrobulbar anesthesia in complicated cataract surgery.

OBJECTIVES: To evaluate and compare levels of patient discomfort and perioperative complications during phacoemulsification and implantation of a foldable intraocular lens under topical lidocaine hydrochloride and retrobulbar anesthesia in patients with cataract who also had exfoliation syndrome, uveitis, posterior synechia, phacodonesis, or previous intraocular surgery. DESIGN: A prospective, randomized, controlled trial was carried out at 2 institutions. PARTICIPANTS: A total of 476 eyes of 476 patients with various well-established risk factors fulfilled the inclusion criteria. In 238 eyes, phacoemulsification was performed under retrobulbar anesthesia, while the other 238 eyes received topical anesthesia. INTERVENTIONS: All patients underwent temporal clear corneal phacoemulsification and implantation of a foldable intraocular lens. Patients under retrobulbar anesthesia received a single injection (3. 5-5.5 mL) of a combination of 0.75% bupivacaine hydrochloride, 2% lidocaine, and hyaluronidase into the retrobulbar space. Patients in the topical anesthesia group received a minimum of 5 doses (approximately 40 microL per dose) of 2% topical lidocaine. No intracameral injection of any anesthetic was given. MAIN OUTCOME MEASURES: The number of complications and adverse events. The intraoperative conditions were judged by the surgeon (P.C.J. or F.K. J.), and a 10-point visual analog scale was used immediately after surgery to assess each patient's overall severity of intraoperative pain. RESULTS: The overall intraoperative complication rate was 1.9% for capsular tear, 3.8% for zonular tear, 1.5% for vitreous loss, and 1.0% for iris prolapse. Apart from the incidence of vitreous loss, which was significantly (P =.041) lower in the topical anesthesia group, no statistically significant differences in intraoperative and early postoperative complications were found between the groups. A supplemental posterior sub-Tenon space injection was required in 1.3% of the topical anesthesia group and in 0.8% of the retrobulbar anesthesia group. Chemosis (2.5%), subconjunctival hemorrhage (1.7%), and periorbital hematoma (0.8%) were seen only in the retrobulbar anesthesia group. The mean + SE pain scores estimated by the patients were 0.84 + 1.30 in the topical anesthesia group and 0.73 + 1.50 in the retrobulbar anesthesia group (P =.41). Patient preference for topical anesthesia (91%) appeared to be significantly (P =.01) higher than for retrobulbar anesthesia (62%). The surgeons found anesthesia-related intraoperative difficulty to be slightly lower in the retrobulbar anesthesia group (8%) than in the topical anesthesia group (14%). CONCLUSIONS: Surgery-related complications and patient discomfort were similar for the 2 methods of anesthesia. Topical anesthesia is justified as a means of improving safety without causing discomfort to the patient even in complicated cases of cataract surgery. Arch Ophthalmol. 2000;118:1037-1043

Silicone intraocular lens implantation in children: preliminary results.

PURPOSE: To evaluate the safety and outcome of foldable silicone intraocular lens (IOL) implantation in children. SETTING: Department of Ophthalmology, University of Giessen, Giessen, Germany. METHODS: The results of cataract extraction and silicone IOL implantation in children having surgery between 1992 and 1997 were retrospectively analyzed in 8 eyes (7 patients). All IOLs were implanted in the capsular bag through a 3.5 mm clear corneal incision. In 4 eyes, primary posterior capsulectomy and anterior vitrectomy were performed. RESULTS: Mean patient age at the time of surgery was 5.1 years (range 8 months to 15 years). The surgeries were uneventful. All IOLs remained anatomically stable and well centered during the mean follow-up of 29.6 months (range 18 to 46 months). Postoperative inflammatory reaction was minimal. Neither fibrinoid exudation nor posterior synechias occurred postoperatively. Postoperative best spectacle-corrected visual acuity ranged from 20/800 to 20/20. All eyes with an intact posterior capsule developed posterior capsule opacification. In the 4 eyes that had primary posterior capsulectomy and anterior vitrectomy, the visual axis remained clear. CONCLUSIONS: These preliminary results suggest that silicone IOL implantation in children is a safe procedure with good and stable short-term anatomic results. Longer follow-up is necessary to answer questions about the long-term safety of silicone lens implantation in a child's eye.

Combined temporal phacoemulsification and pars plana vitrectomy for the treatment of cataract and giant retinal tear in a buphthalmic eye.

The standard approach to a three-port to pars plana vitrectomy is by placing the sclerotomies in the superotemporal and superonasal quadrant and the infusion port in the inferotemporal quadrant. This approach may be adjusted in selected cases that exhibit structural abnormalities of the globe at the superior site by placement of the sclerotomies in the temporal quadrants. We describe a case of a buphthalmic eye with a huge filtering bleb from previous glaucoma surgery that successfully underwent combined cataract and vitreoretinal surgery from a temporal approach for the repair of a giant retinal tear with cataract.

Bilateral implantation of asymmetrical diffractive multifocal intraocular lenses.

OBJECTIVE: To evaluate visual results after bilateral implantation of multifocal intraocular lenses (IOLs) with asymmetrical light distribution for the far and near focus. METHODS: Twenty-nine patients underwent bilateral implantation of silicone-optic, foldable, diffractive IOLs in a prospective, 2-center, noncontrolled interventional study. Each patient had a distant-dominant multifocal IOL implanted in 1 eye and a near-dominant multifocal IOL implanted in the fellow eye. Refractive and visual results, including contrast acuity and binocular visual function, were determined. Patients were questioned for postoperative spectacle usage. RESULTS: Visual and contrast acuity in the dominant focus of either lens was superior to that in the nondominant focus at 3.5 to 12 months postoperatively, i.e., performance was best at distance for the distant-dominant and at near for the near-dominant lens. In binocular viewing, the monocular maximal results added up to an improved binocular visual performance. Binocular visual function was within normal limits. Eighty percent of patients reported no use of spectacles at any time postoperatively. CONCLUSIONS: Bilateral implantation of asymmetrical diffractive IOLs is an effective alternative for restoring simultaneous distance and near vision with a potential for improved contrast sensitivity compared with conventional multifocal IOLs.

[Twilight vision and glare sensitivity in monofocal and multifocal pseudophakia]. / Dämmerungssehvermögen und Blendempfindlichkeit bei monofokaler und multifokaler Pseudophakie.

UNLABELLED: Reduced contrast sensitivity and an increase in glare sensitivity may be observed in patients with cataract and in pseudophakic persons. By means of Mesoptometer II we examined night driving ability according to the recommendations of the German Ophthalmological Society (DOG) in patients with cataract, monofocal or multifocal pseudophakia. METHODS: A total of 176 patients were included in the study: 85 patients (68.8 years) with a monofocal standard IOL, 50 patients (66.1 years) with a multifocal IOL type AMO Array SSM-26NB/SA-40NB and 41 patients with beginning cataract (66.4 years). The corrected visual acuity of all patients was at least 0.7. Contrast acuity was examined at a luminance setting of 0.32 cd/m2; glare sensitivity was measured at a luminance of 0.1 cd/m2 with additional glare source. RESULTS: Night driving ability (both criteria accomplished) was found in 41% of patients with binocular monofocal IOL and in 38% of patients with binocular multifocal IOL. CONCLUSION: Elderly pseudophakic patients and patients with beginning cataract cannot sufficiently fulfill the criteria for night driving ability because of contrast and glare sensitivity. It seems to be indispensable, for the parameters mentioned to be carefully examined and for patients to be informed that night driving ability may be impaired, even if visual acuity is sufficient.

Histological and ultrastructural study of corneal tunnel incisions using diamond and steel keratomes.

PURPOSE: To study the morphology of corneal tunnel incisions using diamond and steel keratomes. SETTING: Department of Ophthalmology, University of Giessen, Germany. METHODS: Corneal tunnel incisions were performed in six human cadaver eyes using three types of diamond keratomes and a steel keratome. The incision profile and morphology were evaluated and compared using light and scanning electron microscopy. RESULTS: The steel keratome caused more disruption of corneal stromal tissue, while the diamond keratomes produced a more regular, smoother incision. The dissecting incision resulted in a smoother surface of cut stromal tissue than the stab incision. CONCLUSIONS: The high quality of corneal tunnel incisions produced with diamond keratomes is the result of their exceptional sharpness, which may have a beneficial effect on wound healing.

Pseudophakic retinal detachment in high axial myopia.

PURPOSE: To investigate the effect of extracapsular cataract surgery with intraocular lens (IOL) implantation and neodymium:YAG (Nd:YAG) laser posterior capsulotomy on the rate of retinal detachment (RD) in myopic eyes with an axial length of 27 mm or more. SETTING: Department of Ophthalmology, University of Giessen, Germany. METHODS: This retrospective, nonrandomized study comprised the records of 386 consecutive surgical procedures in 275 patients performed between December 1985 and December 1993. In May 1994, all patients were asked by a mailed questionnaire whether they had had an RD in either eye or laser treatment for posterior capsule opacification. Responses from 190 patients concerning 253 surgical procedures were evaluated. RESULTS: The pseudophakic RD rate was 0.8% (two cases). One patient developed aphakic RD after IOL explanation. One expulsive choroidal hemorrhage occurred during secondary IOL implantation. Four eyes (1.6%) had vitreous loss, and 74 eyes (29.2%) had an Nd:YAG capsulotomy. Mean axial length was 29.2 mm +/- 1.71 (SD), mean follow-up was 3.8 +/- 2 years, and mean age at surgery was 69.8 +/- 12 years. CONCLUSION: Pseudophakia with no other risk factor posed little additional risk for RD in eyes with high axial myopia; however, Nd:YAG laser posterior capsulotomy was a risk factor for pseudophakic RD. Complicated surgery, such as a secondary procedure or vitreous loss, and young age were major causative factors.

[Contrast vision and contrast sensitivity after binocular implantation of multifocal or monofocal intraocular lenses]. / Kontrastvisus und Kontrastempfindlichkeit nach binokularer Implantation multifokaler oder monofokaler Intraokularlinsen.

BACKGROUND: Multifocal intraocular lenses show a reduction of contrast due to the simultaneous projection of different images to the retina. In this study we examined if there is also a loss of contrast in bilateral implantation of multifocal lenses. MATERIAL AND METHODS: We examined 22 patients with bilateral AMO ARRAY multifocal intraocular lens and compared these to 20 patients with bilateral monofocal intraocular lens. We performed a monocular and binocular examination of contrast acuify by means of Regan's contrast charts and contrast sensitivity by means of B-VAT-II-SG-Video-acuity-tester. RESULTS: Monocular examination of contrast acuity showed significant superiority of the monofocal intraocular lens at the lowest contrast. Bilateral examination of contrast acuity did not show any significant difference. Monocular contrast sensitivity of the monofocal intraocular lens was significantly superior to the multifocal intraocular lens at two spatial frequencies, but under the bilateral condition there was only a significant difference between the two lenses at the highest spatial frequency. CONCLUSIONS: Bilateral implantation of multifocal intraocular lenses enables contrast acuity and contrast sensitivity that comes very close to the performance of the monofocal intraocular lenses.

Effect of head position on refraction in aphakic and phakic silicone-filled eyes.

BACKGROUND: The refraction of the eye is altered significantly after the instillation of silicone oil into the vitreous cavity because of the silicone oil's high refractive index. The degree of the refractive change shows diurnal variation and depends on the patient's head position. PATIENTS AND METHODS: To analyze the degree and time course of refractive changes with respect to head position, the authors performed objective refraction in five aphakic and five phakic silicone oil-instilled eyes with attached maculae using an automatic hand-held refractometer. In each patient, 25 measurements were taken at short intervals using a hand-held autorefractometer with the patient in different positions (supine, head tilted down, and primary eye position). RESULTS: The highest shift of refraction was +5.95 +/- 2.63 diopters spherical equivalent in aphakic eyes and +2.45 +/- 0.71 diopters in the phakic eyes after the patient's position was changed from supine to head tilted down. Three minutes after the position change the refractive shift was stable in almost all eyes. Only slight changes in cylinder and the respective corresponding axis with a mean cylinder shift of 10.1 +/- 5.1 degrees were noted. CONCLUSIONS: Immediately after the head position was changed, aphakic eyes demonstrated more pronounced refractive shifts than phakic eyes. The results of this study explain patients' reports of diurnal changes in visual acuity after intraocular silicone oil instillation. Refractive changes caused by silicone oil stabilized a few minutes after a change in head position.