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Biomedical subjects

J A Gammon

Publications and source records attributed to J A Gammon.

At least 19 recordsLinked to original sources
PubMed1992

Pink hypopyon: a sign of Serratia marcescens endophthalmitis.

Endogenous bacterial endophthalmitis in infants is uncommon. We recently examined and treated an infant who presented with pink hypopyon which followed a Serratia marcescens septicaemia. Culture of the aspirate from the anterior chamber showed no red blood cells, and grew Serratia marcescens, which was also isolated from the tip of the child's umbilical artery catheter. The presence of a pink hypopyon in the absence of hyphaema may suggest the diagnosis of Serratia marcescens endophthalmitis.

Anterior Chamber↗
PubMed1991

Effects of aphakia on the geniculostriate system of infant rhesus monkeys.

The effects on the visual system of rearing rhesus monkeys with monocular aphakia, corrected with extended-wear contact lenses, were assessed with anatomical, electrophysiological and behavioral methods. The major finding was that the effects of the various treatments on the aphakic eye varied in degree depending upon the amount of focused pattern input received by the aphakic eye compared to its fellow eye. The behavioral, electrophysiological and anatomical assessments of the treatment effects on the aphakic eyes correlated closely with each other. Because this experimental paradigm is similar to current clinical procedures for treating human infantile monocular cataracts, it provides a nonhuman primate model for studying aphakia.

Animals↗
PubMed1990

Postnatal axial eye elongation in normal and visually deprived rhesus monkeys.

The influence of anomalous visual experience on the postnatal regulation of axial eye elongation was explored by raising newborn rhesus monkeys under different types of monocular and binocular deprivation and comparing their eye growth pattern with that of age-matched normal monkeys. Monocular manipulations included eyelid suture to eliminate pattern vision; continuous occlusion with an opaque lens to prevent visual experience; surgical removal of the natural lens to induce continuous blur; and correction of surgically induced aphakia with extended-wear contact lenses (EWCLs) to provide a focused image of near objects. Binocular manipulations involved correction of aphakia with an EWCL in one eye and continuous or partial occlusion of the phakic fellow eye. After monocular eyelid suture or occlusion, the deprived eyes were longer than the unmanipulated fellow eyes. Aphakic eyes, however, were shorter than their unmanipulated fellow eyes. The unmanipulated eyes followed the eye elongation pattern of age-matched normal monkeys. Binocular manipulations also resulted in differences in axial length between the two eyes. Aphakic eyes were shorter, and continuously occluded eyes were longer, than eyes of age-matched controls. After partial occlusion, however, the axial length of occluded eyes was similar to that of normal eyes. The finding that lid-sutured and occluded eyes become longer while aphakic eyes remain shorter than normal eyes suggests that additional factors besides retinal image quality control postnatal eye growth.

Animals↗
PubMed1989

Early abnormal visual experience induces strabismus in infant monkeys.

We measured ocular alignment in the horizontal direction for 17 monkeys reared under deprivation paradigms that involved monocular defocus, monocular occlusion and optically corrected aphakia coupled with continuous or partial occlusion of the fellow eye. Alignment was measured at 3 and 7 months with a photographic corneal light reflex method. Results showed that a majority of the monkeys in each paradigm developed strabismus following deprivation rearing, the common factor being early abnormal visual experience. Results also indicated a trend in which many of the deviations seen at 3 months of age were exotropic while all of the animals with deviations at 7 months of age were esotropic. These results on deprivation-induced strabismus, which are the first reported in monkeys, are consistent with previous findings in cats and humans, providing further evidence that deprivation affects not only sensory, but motor systems as well. These findings provide evidence that infant monkeys are a good model for studies of the possible relationships between amblyopia and strabismus that are often noted in children with early visual deprivation. Furthermore, it raises the prospect that some of the findings in previous animal studies that have been attributed to the direct effects of deprivation may actually be secondary to the induced misalignment.

Animals↗
PubMed1989

Development of acuity in a primate model of human infantile unilateral aphakia.

We are studying infant rhesus monkeys that have been reared under various conditions of deprivation to model infantile unilateral aphakia. Grating acuity was assessed in these monkeys from birth to approximately 1 year of age using the quick acuity card procedure. We found that an uncorrected aphakic eye develops little or no pattern vision. Undercorrection or near point optical correction of an aphakic eye with an extended-wear contact lens coupled with continuous occlusion of the opposite eye sometimes results in normal development of acuity in the aphakic eye but does so only at the cost of loss of vision in the occluded eye. Fifty percent partial occlusion coupled with near-point correction of the aphakic eye results in similar development of acuity for both eyes during the time tested. Monkeys wearing near-point correction in the aphakic eye and without any occlusion of the other eye show surprisingly good residual acuities in their aphakic eyes. Based on these results we conclude that aphakic eyes should be treated by providing them with an optical correction, and that occlusion of the opposite eye should be used cautiously.

Animals↗
PubMed1988

The correction of aphakia in infants with hydrogel extended-wear contact lenses. Corneal studies.

Although hydrogel extended-wear contact lenses (EWCLs) have been used extensively in the correction of aphakia in neonates, little is known about the effects of these lenses on infant corneas. Recent studies have demonstrated that long-term contact lenses can induce endothelial morphometric changes, including an increased coefficient of variation (CV) of mean endothelial cell area. Using wide-field specular microscopy, the authors studied 11 eyes of 10 patients, 1 to 3 years of age who, after lensectomy for congenital cataracts, wore EWCLs for the correction of aphakia. Except for two corneas in which increased pachometric readings and CV developed after repeated episodes of lens loss and inflammation, the EWCL were well tolerated and associated with few complications in this study.

Aphakia, Postcataract↗
PubMed1987

Abnormal development of the axial length of aphakic monkey eyes.

Neonatal cataract surgery is becoming more common because irreversible amblyopia occurs if an eye receives inadequate inputs during an early sensitive period of visual development. To model conditions for treating congenital monocular cataracts in humans, we have reared rhesus monkeys which underwent unilateral lensectomy as neonates. Post-surgical A-scan ultrasonography at 8-26 months revealed that the axial length of the aphakic eye in these monkeys was shorter when compared to that of the unoperated eye. This finding has important implications for the long-term clinical management of lensectomized infants in order to achieve good vision in the aphakic eye.

Animals↗
PubMed1986

Ptosis associated with botulinum toxin treatment of strabismus and blepharospasm.

The incidence, severity, and duration of ptosis after botulinum neurotoxin type A (BAT) injections into extraocular or orbicularis muscles were reviewed retrospectively. Even though lid droop frequently complicated botulinum toxin treatment in this series, no loss of vision or permanent ptosis was encountered. Sixty-seven injections were completed in 44 patients between September 1982 and December 1983. The records were reviewed to determine the incidence of ptosis after these 67 injections. Information was not adequate to ascertain the presence or absence of ptosis after 10 injections. Some degree of ptosis developed after 30 (53%) of the 57 injections with adequate follow-up history. Marked ptosis occurred after 12 (21%) of the 57 injections. The posttreatment lid droop in these 12 cases was potentially visually significant. All cases of ptosis, which impinged on the visual axis, resolved to a level permitting undisturbed vision by eight weeks after toxin injection. The incidence of ptosis was similar in patients who received injections into their medial rectus muscles and in patients who received injections into their lateral rectus muscles. However, an increased incidence of marked ptosis may be associated with the injection of previously operated muscles. Toxin dosage, patient age, and quality of the electromyogram used to monitor the injection showed no statistically significant relationship to the ptosis.

Adult↗
PubMed1986

Extended-wear contact lens correction of aphakia in infant primates. Corneal studies.

Extended-wear contact lenses (EWCL) are being used increasingly for the correction of aphakia in infants, but there is a lack of data documenting their effects on the corneas of young children. Therefore, corneal studies were performed on infant monkeys wearing EWCL for the correction of surgical aphakia. Nine newborn monkeys underwent unilateral lensectomy and anterior vitrectomy. Seven eyes were fitted with aphakic EWCL postoperatively and two wore no lenses. After at least six months, corneas were studied with slit-lamp and specular microscopy, and with light microscopy (LM) and electron microscopy (EM). Small central corneal opacities developed in two aphakic eyes corrected with EWCL after episodes of keratoconjunctivitis. One of these corneas was found to have a mildly increased coefficient of variation (CV) of endothelial cell size (polymegathism). Although EWCL are well tolerated by the corneas of aphakic infant primates, their association with endothelial polymegathism, which may indicate physiologic compromise, mandates careful long-term follow-up.

Animals↗
PubMed1985

Extended-wear soft contact lenses for vision studies in monkeys.

The authors have designed and produced extended-wear contact lenses for rhesus monkeys. High-plus lenses to correct neonatal aphakia as well as lenses dyed black for use as occluders to treat amblyopia have been evaluated. Four infant monkeys fitted with soft lenses have successfully worn these extended-wear lenses almost continuously throughout their first year of life. These experiments demonstrate that rhesus monkeys tolerate extended-wear contact lenses well when these lenses are correctly designed, comfortably fitted, and their wear carefully monitored. Furthermore, the results demonstrate that usable levels of vision can be maintained in monocularly aphakic infant monkeys. Since similar methods are now used to treat children with monocular cataracts, our animal model using extended-wear contact lenses on young monkeys should facilitate new and clinically relevant amblyopia experiments.

Amblyopia↗
PubMed1984

Ocular involvement in primary hyperoxaluria.

Ocular involvement from primary hyperoxaluria developed in one infant and one teenaged patient. Autopsy procedures in the first case used special histopathologic staining techniques to demonstrate a wider deposition of calcium oxalate crystals within the eye than was previously suspected. Clinical photographs and fluorescein angiograms in the older patient demonstrated a widespread retinal distribution of crystals with a periarterial predilection. This patient also demonstrated a unique acquired black macular lesion.

Adolescent↗
PubMed1984

Penetrating keratoplasty in children.

Retrospectively studied were 91 patients, 14 years of age or less, who had 152 penetrating keratoplasties in 107 eyes, with an average follow-up of 30.1 months. Survival analysis showed the probability of obtaining a clear graft at one year to be 60 +/- 8% in 45 eyes with congenital opacities, 70 +/- 8% in 31 eyes with opacities from trauma and 73 +/- 8% in 31 eyes with acquired nontraumatic opacities. Most failures occurred during the first postoperative year and were characterized by the gradual loss of graft clarity from undetermined cause. Twenty-nine percent (10) of the 34 eyes with congenital corneal opacities in which vision could be measured had a most recent visual acuity better than 6/120 (20/400). Irreversible amblyopia, glaucoma, other structural abnormalities of the anterior segment and mental retardation complicated visual rehabilitation in the congenital group. In the post-traumatic group, vision was better than 6/120 (20/400) in 45% (13) of 29 eyes, being limited by vitreoretinal pathology, fibrous ingrowth, and optic nerve damage from glaucoma. Visual acuity in the acquired, nontraumatic group was better than 6/120 (20/400) in 67% (20) of 30 eyes. The percentage of patients achieving 6/12 (20/40) or better in the congenital, post-traumatic, and nontraumatic groups were 3% (1/34), 17% (5/29), and 47% (14/30), respectively. In the congenital group, only patients with posterior polymorphous dystrophy obtained a visual acuity of 6/30 (20/100) or better. Preoperative vascularization of the cornea, persistent epithelial defects, and performance of lensectomy-vitrectomy were factors most highly correlated with poor graft survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1980

Gentamicin-resistant Serratia marcescens endophthalmitis.

In a case of metastatic Gram-negative endophthalmitis caused by Serratia marcescens, the bacterial isolate was resistant to gentamicin sulfate and tobramycin but sensitive to amikacin sulfate, a new semisynthetic aminoglycoside approved for systemic use. The importance of antibiotic-resistant S marcescens as a systemic and ocular pathogen is reviewed.

Amikacin↗
PubMedDate not supplied

Anterior segment anomalies associated with the fetal alcohol syndrome.

Anterior segment anomalies were noted in eight children diagnosed as having the fetal alcohol syndrome. Peters' and Axenfeld's anomalies were among the specific defects noted. Four children have maintained clear corneal grafts. A teratogenic action of alcohol during a critical period of development of anterior chamber structures is suggested as an etiologic factor. It is proposed that the varied types and severity of abnormalities noted might result from differences in blood alcohol levels, timing of the insult, and genetic background of the fetus. The observation of various types of malformations thought to share a similar pathogenesis lends additional support to the assumption that there is an interrelationship among these types of congenital segment pathology.

Anterior Chamber↗