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Biomedical subjects

K S Morgan

Publications and source records attributed to K S Morgan.

At least 37 records · Page 2Linked to original sources
PubMed1985

Cataract induction in rabbits with the Nd-YAG laser.

The study of occlusion amblyopia and its therapy has involved animal models of stimulus deprivation achieved by various means, none of which closely simulates human congenital cataract. The authors used the Nd-YAG laser as a means of inducing cataracts in rabbit eyes. Twenty rabbit eyes were treated at various frequency and power settings. High energy YAG laser pulses of 10 mJ produced cataracts that at first resembled large bubbles. Over several days, these bubbles coalesced into smaller opacities. With multiple treatments (usually 150-200 pulses), the authors could create a cataract of a specific size and position. Six months later, 100% of these laser-treated rabbit eyes showed persistent cataracts that resembled human congenital cataracts. It appears that the YAG laser can provide a reproducible and reliable method of inducing specific types of cataracts in animal eyes without damaging other ocular structures.

Animals↗
PubMed1984

Epikeratophakia in children.

Epikeratophakia was performed in 61 children for the correction of aphakia after the removal of unilateral congenital or traumatic cataracts; 51 patients (54 grafts) have more than 6 months follow-up. In the first 27 grafts, 8 (30%) failed, but in the last 27 grafts, only 2 (7%) failed, largely due to improved surgical and tissue handling techniques. The average increase in corneal refractive power for the early patients was 12.68 +/- 4.63 D with an average overrefraction of +0.45 +/- 5.60 D. The last half of the patients showed an average increase of 14.83 +/- 4.83 D, with an average overrefraction of -0.00 +/- 5.20 D. Visual acuity results in patients with traumatic cataracts have been the most satisfactory, with the majority of patients obtaining useful vision. It also appears that in patients with congenital cataracts, the younger the patient at the time of surgery, the greater the chance for a good visual result. Some improvement in vision has been seen in all of the children with successful grafts, even those beyond the age when amblyopia therapy would be considered to have some potential for therapeutic effect. By attaching the correction permanently on the eye, epikeratophakia facilitates the vigorous occlusion therapy required after cataract extraction in these children.

Amblyopia↗
PubMed1983

Preliminary visual results of pediatric epikeratophakia.

Although cataract surgery is feasible in children with unilateral cataracts, visual rehabilitation depends on optical correction and conscientiously maintained amblyopia therapy. Epikeratophakia for the correction of aphakia was performed in 47 children (50 grafts). Postoperative keratometry readings showed an average increase of 12.68 diopters in early patients. With new tissue-handling techniques, the last eight patients showed an average increase of +16.80 D, with -0.64-D overrefraction for emmetropia. Visual results indicate that epikeratophakia is an effective primary procedure for patients with unilateral traumatic cataracts and that it is superior to leaving vision uncorrected in children who have had unilateral congenital cataracts removed and are contact-lens intolerant. Further studies with younger patients will be necessary to define its role in neonates; however, individual results demonstrate that good vision is obtainable with epikeratophakia.

Cataract Extraction↗
PubMed1983

Safety and efficacy of timolol in pediatric glaucoma.

We reviewed the effect of timolol in 89 eyes (50 patients) with various types of pediatric glaucoma. Systemic side effects were observed in two patients (4%). Intraocular pressure (IOP) effect of timolol could only be observed in 18 eyes of 11 patients. The average decrease of IOP was 30.7% at the last follow-up.

Adolescent↗
PubMed1983

Surgical and visual results of pediatric epikeratophakia.

We performed epikeratophakia for the correction of aphakia in 31 children, ages 2 months to 7 years, who had unilateral congenital or traumatic cataracts. In 27 patients with more than 4 months of follow-up, 23 of 30 (77%) grafts were successful. In the 15 patients with 6 months or more followup, the average increase in corneal curvature was 12.39 diopters. The average overrefraction needed to achieve emmetropia was + 2.14 diopters spherical equivalent. Two patients operated on within the first year of life have achieved 6/15 (20/50) visual acuities, as measured by visual evoked potentials. One patient operated on in the second year of life achieved 5/30 visual acuity, as measured by Allen cards. Two patients operated on for traumatic cataracts at ages 2 and 4 years achieved 6/9 (20/30) and 8/30 (Allen cards) visual acuities, respectively. Five older patients who had congenital cataracts or persistent hyperplastic vitreous showed some improvement in visual function. Advantages of epikeratophakia include the placement of most of the correction directly on the eye in a permanent attachment and the elimination of contact lens manipulation in uncooperative patients, so that more time and energy can be devoted to the occlusion therapy.

Age Factors↗
PubMed1982

SCE and UDS studies in a family with retinoblastoma: a case study.

The frequencies of both spontaneous and mitomycin C (MMC)-induced sister chromatid exchanges (SCE) were analyzed in mixed lymphocyte cultures from a kindred with retinoblastoma. Both the affected daughter and male proband, as well as two normal controls, were studied. No differences were observed in the spontaneous or in the MMC-induced SCE frequencies obtained from the peripheral lymphocytes of these patients compared to the normal controls. Unscheduled DNA synthesis (UDS) was observed in the lymphocytes treated with varying concentrations of both MMC and M-methyl-N-nitro-N-nitrosoguanidine (MNNG). Whereas no differences were observed in the rate of [3H]thymidine incorporation in the retinoblastoma-derived lymphocytes exposed to MMC when compared to the controls, differences were seen in the response to MNNG. Our data suggest that cells from these retinoblastoma patients respond like normal cells to damage induced by MMC, but that they are unable to repair damage induced by MNNG.

Crossing Over, Genetic↗
PubMed1982

Secondary surgical procedures after epikeratophakia.

Five patients required secondary surgical procedures after receiving epikeratophakia grafts. A neonate underwent epikeratophakia in combination with extracapsular cataract extraction, followed one week later by peripheral iridectomy and nine months later by strabismus surgery. A 53-year-old male had surgery to correct retinal detachment 4-1/2 months after epikeratophakia surgery for the correction of aphakia. A five-year-old male had epikeratophakia after removal of a traumatic cataract; five weeks later, retinal detachment necessitated vitrectomy, 360 degrees buckle, and cyclocryotherapy. A 4-1/2-year-old female had epikeratophakia for aphakia, followed nine months later by strabismus surgery. A 38-year-old female with keratoconus received a plano epikeratophakia graft, in combination with an extracapsular cataract extraction and anterior vitrectomy, followed two weeks later by an Ocutome vitrectomy. In all cases, the epikeratophakia grafts and interfaces remained clear, and in four of the five patients in whom secondary procedures were successful, vision continued to improve with time.

Adult↗
PubMed1982

Stereoscopic vision and psychomotor learning in dental students.

A testing mechanism is needed for reliably predicting students' problems in acquiring dental psychomotor skills. Students and dental educators could then be made aware of potential problems well in advance of required manual course work. Because testing for stereoscopic vision has long been a part of perceptual-motor ability screening for the U.S. Air Force, a similar stereopsis test was used to examine the role of stereopsis in dental psychomotor learning and its potential as a predictor of student performance. The Lameris TNO Test for stereoscopic vision was given as an adjunct to the Perceptual Ability (PAT/3D) portion of the Dental Admission Test. Both test results were then compared to freshman students' performance in preclinical operative dentistry. Multiple regression analyses indicated that a high degree of stereopsis was not a prerequisite for success in acquiring dental psychomotor skills.

Aptitude Tests↗
PubMed1981

Treatment of congenital glaucoma.

We reviewed 37 consecutive patients who had undergone at least one goniotomy, filtering surgery, and patching for amblyopia because of congenital glaucoma between 1969 and 1979. Of 32 eyes treated for uncomplicated congenital glaucoma, 25 (78%) achieved satisfactory control of intraocular pressure. Seven of the 12 eyes (58%) for which Snellen visual acuities could be obtained had visual acuities of 6/15 (20/50) or better. Of eight eyes treated for complicated congenital glaucoma, four (50%) achieved satisfactory control of intraocular pressure, but the visual acuities of these patients could not be tested.

Acetazolamide↗
PubMed1980

Polyvinyl alcohol as a protective coating on intraocular lenses.

Sixty-eight intraocular lenses were implanted in cats to compare the efficacy of a new polyvinyl alcohol coating in protecting the corneal endothelium from lens-cell contact damage. The mean endothelial density after implantation of the coated lens was significantly higher than the cell density in those eyes receiving the uncoated lens. We saw no clinical signs of unusual inflammation; whole-eye histopathologic study disclosed no signs of inflammation or toxicity related to the coating. Ten coated lenses were placed in balanced salt solution or perfused with balanced salt solution at 0.5 mL/min. The coating remained intact for 60 minutes, affording corneal endothelial protection for this period. In a rabbit anterior chamber toxicity study, using balanced salt solution as a control, no differencs in reaction in the anterior chamber or intraocular pressure were noted.

Animals↗
PubMed1980

The Shearing intraocular lens: where does it go and what does it do in the eye?

Seven Shearing lenses were inserted in four dogs that were selected because their ciliary body sulcus diameter was approximately equal to that of humans. These animals were killed at intervals ranging from 4.5 to 11 months and the eyes submitted for histopathology. In all instances, gross examination revealed the lenses to be well tolerated; however in two eyes there was migration of the peripheral loop into the peripheral iris stroma and in one case, ciliary body sulcus necrosis was seen. No vitreous hemorrhage was found in any of the eyes. One intraocular lens was removed before the animal was killed and the eye did not appear to be damaged. This study raises the possibility of ciliary body damage in those eyes in which the lens is slightly displaced so that one loop exerts pressure on the ciliary body. For this reason, we feel that posterior vitreous hemorrhages must be carefully looked for.

Animals↗
PubMed1980

Toxicity and tolerance of 9-(2-hydroxyethoxymethyl)guanine.

Acyclovir [9-(2-hydroxyethoxymethyl)guanine] is a new antiviral agent which has specific activity in virus-infected cells. The drug has a high therapeutic index in animal and laboratory models but had not been tested for toxicity in human eyes at the time of this study. A randomized double-blind study on patients requiring antiviral therapy for treatment or prophylaxis of herpetic ocular infections revealed minimal irritation associated with topical administration. Further controlled studies will be necessary to evaluate this compound's clinical efficacy.

Acyclovir↗
PubMed1979

The Shearing-style intraocular lens and the posterior chamber.

We observed the Shearing-style intraocular lens in human cadaver eyes and in dog eyes. In human cadaver eyes the lens loops rest in the ciliary body sulcus without exerting undue pressure; the only major problem occurred when the posterior capsule was torn and a loop found its way into the pars ciliaris of the ciliary body or into the vitreous base. Seven Shearing-style lenses were implanted in four dogs: six-month preliminary histopathology showed four of these lenses to be well tolerated with abundant synechiae formation around the loops. Two eyes exhibited loop pressure necrosis due to slight lens displacement.

Animals↗