Phakic Group Research Articles

Human Lens Effect on In Vivo Scanning Laser Polarimetric Measurements of Retinal Nerve Fiber Layer Thickness

To determine the effect of the human lens on retinal nerve fiber layer measurements by scanning laser polarimetry. This technique uses the form birefringence of the retinal nerve fiber layer to estimate its thickness. The GDx Nerve Fiber Analyzer contains an optical retarder element to compensate for the birefringence of the human cornea. Fourteen nonglaucomatous pseudophakic or aphakic eyes were matched by age and race to 14 nonglaucomatous phakic eyes. Intraocular pressure, optic nerve head evaluation by slit lamp biomicroscopy and visual fields were performed to establish the absence of glaucoma. The nerve fiber layer thickness measurements by the GDx Nerve Fiber Analyzer were compared between the two groups. The average nerve fiber layer thickness in the phakic group was 67.2+/-11.9 ,m and in the nonphakic group was 66.1 +/- 11.8 microm (P=0.80). The human lens has negligible influence on in vivo nerve fiber layer thickness measured by the GDx Nerve Fiber Analyzer.

Visual function with monofocal versus multifocal IOLs

Purpose: To assess visual outcome in four groups: one multifocal intraocular lens (IOL), one monofocal IOL, and two phakic, one older and one younger.Setting: Department of Ophthalmology, National Health Service, Puerta de Hierro University Clinic, Madrid, Spain.Methods: This prospective study comprised 70 aphakic eyes, 42 with a multifocal and 28 with a monofocal IOL, and 42 phakic eyes, 21 older than 60 years and 21 younger than 60 years. The phakic groups served as a double control. Main outcome measures were corrected and uncorrected distance and near visual acuities, contrast and glare sensitivity, and clinical and subjective complications.Results: There were no significant differences between the monofocal and multifocal IOL groups in uncorrected or corrected distance visual acuity. Near visual acuity in the multifocal group, with and without distance correction, was significantly better than in the monofocal group. Near vision with addition was similar between the two IOL groups. There were no significant differences between the monofocal and multifocal IOL groups in contrast sensitivity at the 96 and 50% thresholds. Between-group differences of less than one Regan line were found at the 25 and 11 thresholds. The phakic groups had better contrast sensitivity. The older phakic group's results were closer to those of the IOL groups. There were no significant complications.Conclusion: Distance acuity and contrast sensitivity were similar in the monofocal and multifocal IOL groups; however, the multifocal group had significantly better near acuity. The younger phakic group had significantly better contrast sensitivity than the other groups.

QUALITY OF CORNEAL DONOR TISSUE IN THE GREATER THAN 75 YEAR AGE GROUP

To evaluate the quality of the corneal donor tissue in the greater than 75 year age group with regard to the suitability for transplantation. Fifty consecutive donor corneas from the > 75-year age group were assessed at the Minnesota Lions Eye Bank with slit-lamp examination and specular microscopy. Thirty-five of the donor corneas were from phakic eyes and 15 were from pseudophakic eyes. There was a highly significant difference (p < 0.05) in the endothelial counts found in the donor corneas from the phakic corneas (average, 2,253.4 +/- 428.9) compared to the pseudophakic eyes (average, 1,701.7 +/- 548.2). There was a highly significant difference (p < 0.05) between the corneal ratings in the phakic and pseudophakic groups, with the phakic group receiving much better (lower) ratings. None of the 15 pseudophakic donor corneas was found to be suitable for transplantation based on a corneal rating of < or = 2, whereas 17 of the 35 phakic eye (48.6%) were found to be suitable for transplantation. From the phakic eyes, 10 of 20 corneas (50.0%) were acceptable in the 76-80-year age group, four of 10 corneas (40.0%) were acceptable in the 81-85-year age group, two of three corneas (66.7%) were acceptable in the 86-90-year age group, and one of two corneas (50.0%) was acceptable in the 91-95-year age group. The results of this laboratory study suggest that many older donor corneas from phakic eyes may be suitable for corneal transplantation.

Vancomycin Levels in the Vitreous Cavity After Intravenous Administration

We studied the effects of inflammation, repeated antibiotic doses, and the surgical status of the eye on penetration of vancomycin hydrochloride into the rabbit vitreous cavity after intravenous administration. We studied three anatomic states (phakic, aphakic, and aphakic, vitrectomy-treated eyes) subdividing each into inflamed and noninflamed groups. Intravenous vancomycin hydrochloride (15 mg/kg of body weight) was administered every 12 hours for 48 hours. Eyes were harvested for the assay of vitreous cavity antibiotic levels at various intervals from one to 49 hours. We determined concentrations and calculated mean values and S.E.M. Therapeutic levels were not established in the vitreous cavity at any time period in the two phakic groups. At 25 hours, the inflamed aphakic eyes had concentrations of 5.05 +/- 1.9 micrograms/ml and the control noninflamed aphakic eyes 4.5 +/- 1.23 micrograms/ml; slight increases were found by 49 hours. Concentrations tested in the aphakic, vitrectomy-treated eyes at two, 13, 25, and 49 hours demonstrated progressive increases both in the inflamed eyes (5.4 +/- 2.4 micrograms/ml, 9.64 +/- 4.25 micrograms/ml, 9.2 +/- 3.96 micrograms/ml, 10.34 +/- 4.49 micrograms/ml) and noninflamed eyes (3.52 +/- 2.1 micrograms/ml, 5.4 +/- 1.96 micrograms/ml, 6.8 +/- 2.53 micrograms/ml, 8.7 +/- 5.44 micrograms/ml). Vitreous vancomycin concentrations in aphakic and aphakic, vitrectomy-treated eyes after intravenous administration exceed the minimal inhibitory concentrations for the usual gram-positive pathogens that create endophthalmitis, suggesting a role for intravenous vancomycin in the treatment of bacterial endophthalmitis.

Electrophysiological Contrast Sensitivity with Bifocal Intraocular Lenses

OBJECTIVE: To verify if a loss in electrophysiological contrast sensitivity in a group of patients with bifocal posterior chamber intraocular lenses (PC IOLs) can be demonstrated, with respect to monofocal PC IOL-patients and healthy phakic ones. STUDY DESIGN: Prospective study of electrophysiological contrast sensitivity in randomly selected clear lens or pseudophakic patients, over 3 months after surgery. SETTING: Ophthalmic out-patient Palermo University Eye Clinic. PATIENTS: 40 adults divided into four groups of ten eyes each, matched for age, sex, far and near visual acuity, respectively with a two-zone bifocal IOL, a multizone bifocal IOL, a Sinskey-Kratz monofocal IOL, or a natural clear lens. MAIN OUTCOME MEASURES: Mean electrophysiological contrast sensitivity function of each group, obtained from the components CI-CII of the pattern ON-OFF VEPs responses with various spatial frequencies. RESULTS: The two-zone and multizone bifocal IOL-groups exhibit a lower contrast sensitivity when compared with the phakic clear lens group, with all the spatial frequencies tested (P < 0.05). Moreover, they show a lower contrast sensitivity with respect to the monofocal IOL-group with the majority of frequencies (P < 0.05). On the contrary, the latter group shows a lower contrast sensitivity with low-medium spatial= frequencies, but not with higher spatial frequencies, if compared with the phakic group. CONCLUSIONS: Data analysis indicates that while the monofocal IOLs decrease only the low-frequency contrast sensitivity, the bifocal implants depress the whole contrast sensitivity curve to a much lower level. It seems reasonable to hypothesize that, in some particular environmental requirements, this could impair the visual function.

Mesopic Visual Acuity and Glare Sensitivity in Phakic and Pseudophakic Eyes

Twenty eyes with a PMMA-IOL, 14 with a HEMA-IOL and 8 with a silicone-IOL were examined and compared to a phakic eye group and a cataract group. The visual acuity for daylight was measured under clinical conditions and under glare using the brightness acuity tester. Mesopic vision was tested with and without glare at the Ocutrast. No statistically significant difference was found between the different IOL materials except between PMMA and silicone at the Ocutrast under glare. The compared materials can be regarded as equal concerning mesopic vision and glare sensitivity. The mean daylight visual acuity was almost equal in the phakic and pseudophakic groups. Some differences, but without statistical significance, were seen with the brightness acuity tester. A statistically significant difference was found between phakic and pseudophakic eyes with the Ocutrast measurements. The reduced mesopic vision and the increased glare sensitivity in the IOL groups seem to be evoked by scattering of light from the posterior capsule. In conclusion the Ocutrast can be used to quantify reductions of visual functions even if visual acuity is not reduced.

In vivo lens density measurements using the IntraOptics opacity lensmeter

We evaluated 589 eyes using the IntraOptics opacity lensmeter 701. Twenty-one eyes contained poly(methyl methacrylate) intraocular lenses. The patients in the phakic group (578 eyes), who had no ocular pathology other than refractive error or cataracts, averaged 60.3 years of age, had an average visual acuity of 20/30, and displayed an average lens density as measured with the opacity lensmeter of 22.09. The data were analyzed for the effect of age upon density using various regression models. The best fit was obtained with an exponential model: Density = 6.2 x e(0.02 x Age), with a correlation coefficient of 0.759. The average density for the pseudophakic group (mean age = 68.5) was 9.23. Neither cortical nor posterior suhcapsular cataracts were well recorded. Our results indicate that the IntraOptics opacity lensmeter is a rapid and accurate instrument for documenting nuclear cataract changes. The opacity lensmeter may prove useful not only as a clinical tool for monitoring cataract progression but also as an “electronic” second opinion.

Characteristics of rhegmatogenous retinal detachment

Characteristics of rhegmatogenous retinal detachment and its predisposing factors were studied in a consecutive series of 342 patients operated on for retinal detachment (RD) at the University Eye Hospital in Helsinki in 1978-1981. On these, 234 were pre-operatively examined and operated on by the senior author. The mean age of the patients was 52.8 +/- 1.0 (range 5.7 to 83.0) years, 49.1% were males, 50.9% females. Bilateral RD occurred in 9.9%, and another 4.7% had been treated for retinal breaks in the fellow eye. Of the main predisposing factors, myopia (greater than or equal to -1.0 D) was found in 50.6% of the phakic eyes, 23.0% of the eyes were aphakic, and lattice degeneration was found in 15.1% and trauma in 11.9% of the whole series. In the nontraumatic phakic group, lattice degeneration was present in 31.3%. In the aphakic group, 25.9% had underlying myopia and 8.1% showed lattice degeneration. The relative importance of these factors varied with age. Total RD was found in 60 eyes (17.0%), most commonly in aphakic eyes (32.1%). Macula was detached in 56.5%. Two or more retinal breaks were found in 40.9%. The type of breaks varied with age and refraction. Oral dialysis was common before the age of 20 in non-myopic phakic eyes. Between 20 and 39 years, tears and holes were equally common, and after 40 years of age tears predominated. Tears outnumbered holes both in nonmyopic and myopic eyes, most round holes were found in myopic eyes. In 11.6% of the eyes no sure retinal breaks were detected. Relation of retinal breaks to peripheral retinal degenerations was studied.

Incidence of Cystoid Macular Edema Following Scleral Buckling Procedure

Sixty eyes of 58 patients who underwent scleral buckling procedures were prospectively evaluated with postoperative fluorescein angiograms. Forty-three percent of these eyes showed angiographic cystoid macular edema (CME). Aphakic patients showed a 64% incidence of cystect the final visual acuity of aphakic patients but significantly reduced the visual recovery in the phakic group. The incidence of CME was not related to preoperative foveal detachment, duration of aphakia, duration of detachment, surgical approach, or refraction.