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Biomedical subjects

S R Lambert

Publications and source records attributed to S R Lambert.

78 records · Page 5Linked to original sources
PubMedDate not supplied

Multifocal versus monofocal correction of neonatal monocular aphakia.

We compared the efficacy of monofocal and multifocal intraocular lenses (IOLs) as a means of optically rehabilitating eyes with monocular congenital cataracts using a primate model. A congenital cataract was simulated in the right eye of 20 monkeys from birth to 2 weeks of age with an opalescent contact lens. A lensectomy was then performed and a monofocal IOL was implanted in 11 eyes and a multifocal IOL in 9 eyes. Any residual refractive error was then corrected with an extended-wear contact lens. The fellow eyes were then randomized to no treatment or 70% occlusion therapy. Grating acuity was assessed using forced-choice preferential looking with Teller acuity cards at regular intervals. At 32 weeks of age, the pseudophakic eyes were mildly amblyopic, but the grating acuities were not significantly different between the pseudophakic eyes with multifocal versus monofocal IOLs or between subjects who had received occlusion therapy versus no treatment of the fellow eye. We conclude that at least through 32 weeks of age, multifocal and monofocal IOLs are of similar efficacy and occlusion therapy may be less important to prevent amblyopia from developing in pseudophakic eyes compared to contact-lens corrected aphakic eyes.

Amblyopia↗
PubMedDate not supplied

Reappraisal of occlusion therapy for severe structural abnormalities of the optic disc and macula.

The visual function of some children with structural defects of the macula or optic nerve has previously been shown to improve with occlusion therapy. The charts of five children, ages 4 to 8 years, who had various types of severe structural abnormalities were reviewed. Two patients had optic nerve hypoplasia; there was one case each of foveal hypoplasia, posterior persistent hyperplastic primary vitreous, and retinopathy of prematurity. All the patients had undergone extensive amblyopia therapy prior to referral. In three children, occlusion therapy had been initiated and continued intensively for several months or longer without recognizing the presence of a severe, underlying structural abnormality. In none of the five children was there any clear-cut evidence of visual improvement. In some cases, the long period of enforced iatrogenic vision impairment resulted in significant psychosocial harm and developmental delay. In all five cases, it was structural changes rather than amblyopia that ultimately accounted for visual loss. The authors stress the importance of a meticulous fundus examination directed at finding organic defects prior to patching. Close, periodic monitoring of visual function should then follow. To spare the child unnecessary psychosocial impairment, it is advisable to follow established recommended thresholds for terminating occlusion therapy.

Amblyopia↗
PubMedDate not supplied

Haptic breakage following neonatal IOL implantation in a nonhuman primate model.

To evaluate the long-term safety of implanting intraocular lenses (IOLs) in neonatal eyes using a nonhuman primate model, a one-piece all-polymethylmethacrylate (PMMA) IOL was implanted into the posterior chamber of 21 neonatal Rhesus monkey eyes following a lensectomy and anterior vitrectomy. These monkeys then were monitored for 26 to 40 months for complications. The eyes from seven monkeys were studied histopathologically. One or both haptics broke on 7 of the 21 (33%) IOLs in a mean of 21 months (range 6 to 31 months) after their implantation. Only one of the haptics from these seven eyes was found to be in the capsular bag when these eyes were studied histopathologically. Nine haptics had eroded into the iris leaflets, two into the ciliary body, and one into the anterior chamber. One additional haptic was in the sulcus. The haptics of one-piece all-PMMA IOLs may break if implanted in neonatal eyes. A number of factors likely contributed to haptic breakage in these eyes, including an increased number of reoperations, malpositioning of IOL haptics, rapid circumferential and axial growth, and the formation of large Soemmerring's rings.

Animals↗
PubMedDate not supplied

Electroretinographic findings in infants with the shaken baby syndrome.

PURPOSE: To determine if electroretinography is helpful in the work-up of children with the shaken baby syndrome. METHODS: Six children with retinal hemorrhages and the shaken baby syndrome underwent electroretinography (ERG). The ERGs of these six children were compared with six age-matched controls using the sign-rank test. RESULTS: Neither the implicit time nor the amplitude of the white scotopic ERG response was significantly different between these patients and age-matched controls. Although the amplitude of the blue scotopic and 30 Hz flicker responses were attenuated (p < 0.05), the implicit times were not significantly different from controls. Three of the patients had serial ERGs recorded. The b-wave implicit time and amplitude improved in two of these patients. The ERG was helpful in distinguishing between a CNS and a retinal cause of visual loss in one child. CONCLUSIONS: The ERG can be helpful in assessing retinal function in children with the shaken baby syndrome who have persistent visual impairment. In most cases, the ERG is not helpful in the initial assessment of children with the shaken baby syndrome.

Battered Child Syndrome↗
PubMedDate not supplied

Infantile lensectomy and intraocular lens implantation with long-term follow-up in a monkey model.

PURPOSE: To report the long-term clinical and histopathologic findings in infant monkeys following a lensectomy and intraocular lens (IOL) implantation using two different surgical techniques. METHODS: A lensectomy and IOL implantation was performed on the right eye of 10 infant monkeys. A posterior capsulotomy was performed using a limbal approach in 5 monkeys (Group 1), and a pars plana approach in 5 other monkeys (Group 2). The residual refractive error in the pseudophakic eye was then corrected with a contact lens and the fellow eye was occluded for 70% of the daylight hours. The monkeys were then examined at regular intervals for 2 to 4 years. Visual acuity was assessed using operant testing and sweep visual evoked potentials (VEPs). At the end of the study, the pseudophakic eyes were studied histopathologically. RESULTS: The only complications that required reoperation were diaphanous fibrin membranes on the lens optic (n=10) and lens reproliferation into the pupillary space (n=5). The visual outcome was similar in Groups 1 and 2, with better acuities in the phakic eyes compared with the pseudophakic eyes. A higher percentage of both haptics were found in the capsular bag for the monkeys in Group 2 (n=3) than in Group 1 (n=1). CONCLUSIONS: Although haptic placement was superior using a pars plana approach to perform the primary posterior capsulotomy, no clinically discernable difference was noted in IOL centration between the monkeys undergoing a limbal versus a pars plana posterior capsulotomy and no difference was noted in the visual outcome.

Animals↗