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Biomedical subjects

K Tsubota

Publications and source records attributed to K Tsubota.

At least 199 records · Page 11Linked to original sources
PubMed1994

A piggyback contact lens for the correction of irregular astigmatism in keratoconus.

PURPOSE: Although the combination of a hard contact lens "piggybacked" on a soft lens base for the correction of severe astigmatism in keratoconus has existed for two decades, little is known about its effect on the corneal epithelium and endothelium. This study involves two parts: the measure of oxygen pressure in rabbits, and the long-term effects on patients with keratoconus wearing these hybrid lenses. METHODS: A polarographic sensor was used to measure the oxygen pressure on rabbit corneas under two types of piggyback lenses: oxygen-permeable hard lenses on high water-content soft lenses, and polymethylmethacrylate (PMMA) lenses on low water-content soft lenses. In the clinical evaluation, 11 patients with keratoconus (8 men, 3 women; 25.1 +/- 4.9 years of age) who could not wear hard contact lenses due to constant pain or inadequate lens fitting were given oxygen-permeable piggyback contact lenses and were observed for at least 9 months. RESULTS: In the animal study, the oxygen pressure under piggybacked oxygen-permeable hard contact lenses was 95 +/- 14 mmHg after 5 minutes wear, but it was only 34 +/- 14 mmHg when PMMA and low water-content lenses were used. Ten of 11 patients were successfully treated using this technique, whereas one patient had persistent contact lens loss, requiring penetrating keratoplasty. Specular microscopic observation of the corneal epithelium and endothelium did not show any changes during the follow-up period. CONCLUSIONS: These results suggest the efficacy and safety of the piggyback combination of oxygen-permeable hard and soft contact lenses for the correction of astigmatism in patients with keratoconus.

Adolescent↗
PubMed1994

Quantitative evaluation of postsurgical inflammation by infrared radiation thermometer and laser flare-cell meter.

Using an infrared radiation thermometer and a laser flare-cell meter, we evaluated intraocular inflammation in 40 patients who had cataract surgery by measuring central corneal temperature, number of cells, and amount of flare in the anterior chamber. Patients were divided into two groups based on duration of surgery: Group A, more than 40 minutes; Group B, less than 40 minutes. In Group A (n = 32), corneal temperature (degrees Celsius) increased by 1.10 +/- 0.57, 0.75 +/- 0.69, 0.41 +/- 0.56, and 0.24 +/- 0.45 on days 1, 2, 14, and 30, respectively. Group B (n = 8) had no significant rise in corneal temperature, but cell count (mean +/- 1 SD) increased to 39.3 +/- 13.6, 36.4 +/- 18.1, 15.5 +/- 16.5, and 4.4 +/- 3.1 on days 1, 2, 7, and 14, respectively. Flare increased to 88.9 +/- 88.9, 45.8 +/- 30.1, 38.3 +/- 25.4, and 18.5 +/- 9.4 on days 2, 7, 14, and 30, respectively. These observations show that the longer the cataract surgery, the greater the inflammation. Although inflammation was evaluated quantitatively by both infrared radiation thermometer and laser flare-cell meter, the latter appears to be more sensitive. Thermometry will only detect the results of very traumatic surgery, with a corresponding breakdown of the blood-aqueous barrier.

Anterior Chamber↗
PubMed1994

Spectacle side panels and moist inserts for the treatment of dry-eye patients.

To increase the moisture level around the eyes, small, wet, acute, triangular sponges, from which water steadily evaporates, were attached to special side panels of modified eyeglasses. The moisture level in the region between the cornea and the spectacle lens was measured in 10 patients with moderately severe dry eyes and in 10 normal controls, by a miniature moisture sensor under ambient conditions of 22.3 degrees C and 29.8% humidity. The humidity was 32.0 +/- 4.2% with spectacles, frame only (no lenses); 32.3 +/- 6.0% with spectacles; 37.9 +/- 5.1% with spectacles equipped with side panels, and 42.7 +/- 5.7% with side panel moist inserts attached for dry eye patients. Humidity was the highest with moist inserts added to the spectacles of the control group, with or without moderate wind. All dry eye patients noticed symptomatic relief with the inserts, and the rose bengal score and fluorescein staining improved after 2 weeks of their use. Our findings indicate that the combination of side panels and periodically moistened sponge inserts offer a simple and noninvasive approach to increasing the humidity surrounding the eyes, thus decreasing the tear evaporation from the ocular surface and providing amelioration of frequently debilitating symptoms of dry eye.

Dry Eye Syndromes↗
PubMed1994

Three different types of dry eye syndrome.

We analyzed patients with dry eye syndrome with regard to autoimmune conditions. A total of 116 patients with dry eye syndrome were divided into three groups: simple dry eye (SDE), i.e., dry eye with no circulating autoantibodies; autoimmune positive dry eye (ADE), dry eye with circulating autoantibodies; and Sjogren's syndrome (SS), dry eye associated with Sjogren's syndrome. Schirmer test showed values of 3.0 +/- 2.2 mm in SDE, 3.1 +/- 2.0 mm in ADE, and 2.4 +/- 2.3 mm in SS reflecting the inadequacy of this test in differentiating among the groups. However, Schirmer test with nasal stimulation showed values of 19.1 +/- 12.4 mm in SDE and 16.4 +/- 10.9 mm in ADE, which were significantly higher than the 7.0 +/- 6.6 mm found in SS (p < 0.01). Moreover, ocular surface alterations evaluated by vital staining and brush cytology were significantly milder in SDE and ADE than in SS. SDE and ADE have less ocular surface abnormalities with good reflex tearing, whereas SS has less reflex tearing and more squamous metaplasia.

Adult↗
PubMed1994

Histamine and tryptase levels in allergic conjunctivitis and vernal keratoconjunctivitis.

Tryptase is useful as a specific and accurate indicator of mast cell activation, whereas histamine, a mast cell's major mediator, also exists in basophils. The aim of this study is to investigate histamine and tryptase levels in allergic conjunctiva. We measured histamine and tryptase levels in conjunctival epithelial cell suspension of children with allergic conjunctivitis (AC) and vernal kerato-conjunctivitis (VKC), and controls, and we evaluated correlations with clinical observations. Both the histamine and tryptase levels in VKC were significantly higher than controls (p < 0.05, p < 0.01), and histamine levels in VKC was also greater than AC (p < 0.05). The histamine/tryptase (H/T) ratios were 0.03 +/- 0.04 in AC, 0.08 +/- 0.09 in VKC and 0.006 +/- 0.006 in controls. The H/T ratios in VKC were significantly higher than controls (p < 0.05) and AC (p < 0.05), and were also found to correlate with the superficial punctate keratopathy (SPK) score (r2 = 0.89). Analyzing the histamine and tryptase levels in conjunctival epithelium may be useful in evaluating the allergic ocular surface, especially in the cases with SPK, where the increase in the histamine levels is not accompanied by an increase in tryptase levels. This suggests an important role for inflammatory cells such as basophils infiltrating into the conjunctival epithelium in allergic reactions.

Child↗
PubMed1994

Inhibition of feline immunodeficiency virus gene expression and replication by alphaherpesvirus ICP4 homologues.

We investigated the effects of pseudorabies virus (PRV), herpes simplex virus type 1 (HSV-1), and equine herpesvirus type 1 (EHV-1) ICP4 homologues on feline immunodeficiency virus (FIV) long terminal repeat (LTR)-directed gene expression. This was done by using the transient expression chloramphenicol acetyltransferase (CAT) assay in Crandell feline kidney (CRFK) and Felis catus whole fetus 4 cells transfected with a chimeric FIV LTR-CAT reporter construct in combination with effector plasmids expressing the PRV, HSV-1 or EHV-1 ICP4 homologue. The experiments demonstrated that the ICP4 homologues could significantly inhibit FIV LTR-directed gene expression. Moreover, the ICP4 homologues also exhibited a marked inhibitory effect on FIV replication in CRFK cells cotransfected with an infectious molecular clone of FIV.

Animals↗
PubMed1994

Detection of human immunodeficiency virus, hepatitis B virus, and hepatitis C virus in donor eyes using polymerase chain reaction.

Detection of human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) in donor eyes was performed. DNAs were extracted from the uvea, and they were amplified using the polymerase chain reaction (PCR). Amplified viral DNAs were detected with liquid hybridisation and chemiluminescent assay in which no radioactive materials were used. This method was shown to have a sensitivity limit of fewer than 10 copies of HIV, making it much more sensitive than the current techniques employed in eye banks. The method was applied to 120 donor eyes, including four from donors seropositive for HBV. The HBV gene was detected in one case in which the donor's blood had not been tested for HBV. HIV and HCV genes were not detected in any of the samples. The assay could be an effective screening test for the detection of these viruses in eye bank eyes.

Adolescent↗
PubMed1994

Extended wear soft contact lenses induce corneal epithelial changes.

The purpose of this study was to determine the corneal epithelial alterations induced by various types of contact lenses. By employing the specular microscope, the corneal epithelia of 60 patients who had worn contact lenses for more than 1 year were re-examined along with 15 myopic controls. The morphological changes in aphakic patients who changed from extended wear soft to extended wear rigid gas permeable lenses were also studied. The mean cell area of the corneal epithelium was 621.5 (SD 92.5) microns 2 for daily wear rigid gas permeable lenses (n = 15), 645.8 (98.1) microns 2 for daily wear soft lenses (n = 15), and 634.7 (88.6) microns 2 for extended wear rigid gas permeable lenses (n = 15), none of which differed significantly from the control value of 610.5 (98.1) microns 2. Only the extended wear soft lens group (n = 15) showed significantly enlarged epithelia (806.1 (50.1) microns 2, p < 0.01 versus the other groups). The epithelium partially returned to normal after changing from extended wear soft lenses to extended wear rigid gas permeable ones. The corneal epithelium showed increased cell area only with extended wear soft contact lenses which are known to pose a risk for corneal infection.

Adult↗
PubMed1994

Treatment of amblyopia by extended-wear occlusion soft contact lenses.

Although occlusion eye patches are effective for the treatment of amblyopia, many physical difficulties arise such as allergic reactions of the skin and unattractiveness. Thus, in dealing with these problems we developed the occlusion extended-wear soft contact lens (OCL) to be used as a substitute for the eye patches. With these OCL, patients benefited from the 24-hour occlusion instead of the 6- or 8-hourly eye patch. Although there was a slight possibility that corneal problems might arise due to the lens, the amblyopia patients who gave up the eye patch treatment responded positively to the OCL treatment.

Amblyopia↗
PubMed1993

Corneal epithelial changes after excimer laser photorefractive keratectomy.

We used the specular microscope to investigate corneal epithelial changes after excimer laser photorefractive keratectomy. Thirteen patients underwent photorefractive keratectomy on one eye to correct myopia. We observed the central corneal epithelium of each eye at postoperative periods from one to 15 months after photorefractive keratectomy. The fellow eye served as a control. In 11 eyes (85%) the central cornea showed normal epithelial patterns. Two eyes had an abnormal epithelial pattern that included elongated epithelial cells. There were no difference in the mean cell area or coefficient of variation of mean cell area between the treated eyes and the control eyes. These results suggest that permanent destruction of Bowman's membrane caused by photorefractive keratectomy does not affect the morphologic characteristics of the most superficial layer of the corneal epithelium in most eyes. However, the presence of abnormal epithelial cell patterns in two patients should be considered a risk factor for this procedure.

Adult↗
PubMed1993

Expression of cell adhesion molecules in the salivary and lacrimal glands of Sjogren's syndrome.

We attempted to determine whether cell adhesion molecules, including vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and E-selectin (endothelial-leukocyte adhesion molecule-1; ELAM-1), are involved in the lymphoid cell infiltration of the salivary and lacrimal glands in Sjogren's syndrome (SS) patients. Both immunohistochemical analysis and the reverse-transcripts polymerase chain reaction (RT-PCR) were used to analyze the expression of VCAM-1, ICAM-1, ELAM-1, very late antigen 4 (VLA-4 [alpha 4,beta 1]), lymphocyte function-associated antigen-1 (LFA-1), interferon-gamma (IFN-gamma), tumor necrosis factor (TNF), and interleukin-1 beta (IL-1 beta). Immunohistochemical analysis of salivary gland biopsies from SS patients showed a marked expression of VCAM-1 and ICAM-1 in the venules surrounded by infiltrated CD4+ CD45RO+ T cells. E-selectin was expressed on vascular endothelium with weak intensity. Increased levels of VCAM-1, ICAM-1, IFN-gamma, and IL-1 beta mRNA were demonstrated by RT-PCR, whereas E-selectin mRNA were weakly expressed in SS lacrimal and salivary gland tissues. This is in contrast with strong expression of ELAM-1 in IL-1 beta-stimulated human umbilical vascular endothelial cells (HUVEC) in vitro. Cytokine-mediated up-regulation of VCAM-1 and ICAM-1 that facilitates the recruitment of VLA-4 and LFA-1 expressing T cells might contribute to lymphoid cell infiltration in the salivary and lacrimal glands in SS.

Base Sequence↗
PubMed1993

Corneal endothelial cell loss induced by air bags.

BACKGROUND: Although the automobile air bag is a safety device used to protect drivers from death and moderate-to-severe injury, recently it also has been reported to be associated with some ophthalmic injuries. The authors have encountered a case in which a normal air bag may have caused a driver's corneal endothelial cell loss. In this study, the authors evaluate corneal endothelial cell loss caused by several types of air bags in the hope that air bag technology may be improved. METHODS: The authors performed impact tests with whole pig eyes fixed in a crash test dummy, using five different types of air bags. The area of damaged corneal endothelial cell was analyzed quantitatively. RESULTS: The authors found that corneal endothelial cell loss was correlated with the inflator power of the air bag but not with its weight. CONCLUSION: Although greater inflator power is needed for rapid air bag expansion, the effect on the eye should be considered in further refining this device. There may be greater latitude in the selection of air bag material. The authors believe their technique is applicable to the assessment of many air bag or passenger variables.

Accidents, Traffic↗