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Biomedical subjects

S Ishiko

Publications and source records attributed to S Ishiko.

At least 37 records · Page 2Linked to original sources
PubMed1998

Diurnal variation of corneal autofluorescence in normal and diabetic eyes.

PURPOSE: To examine the diurnal variations in corneal autofluorescence in normal and diabetic patients. METHODS: We measured corneal autofluorescence using a fluorophotometer fitted with an anterior segment adapter. Corneal autofluorescence was measured 10 times at 3 min intervals to evaluate the reproducibility of this instrument in 4 eyes of 4 normal subjects. The diurnal variation in corneal autofluorescence was determined by measuring the fluctuations in 10 eyes in 10 normal subjects and one unoperated eye each of 10 patients with proliferative diabetic retinopathy (PDR). We performed five consecutive measurements at 1000, 1130, 1400, 1630 and 1900 hours. The mean value of five measurements, the variation range and the coefficient of variation were analysed. RESULTS: The mean coefficient of variation in the measurement using this instrument was 8.6 +/- 1.0%. In the patients with PDR, the mean corneal autofluorescence value was significantly higher (p < 0.001), the variation range was significantly wider (p < 0.001) and the coefficient of variation was significantly greater (p < 0.01) than in the normal subjects. CONCLUSIONS: The results of this study suggest that corneal autofluorescence changes over the course of a day in patients with diabetes. This may be caused by the breakdown of the blood-aqueous barrier that we reported previously.

Adult↗
PubMed1998

Corneal and lens autofluorescence in young insulin-dependent diabetic patients.

To study the early ocular abnormalities in young diabetic patients, corneal and lens autofluorescence was measured by fluorophotometry in 30 eyes of 30 insulin-dependent diabetic patients without retinopathy. The lens [f(l)] and the corneal [f(c)] autofluorescence values in diabetic patients were significantly higher than in controls. In diabetic patients, f(l) was significantly correlated with the duration of diabetes, the f(c) was significantly correlated with the duration of diabetes and the indices of metabolic control, i.e. HbA1c and fructosamine. Our study demonstrated that young diabetic patients clearly had corneal and lens abnormalities before the appearance of overt diabetic retinopathy. The f(c) value might be a good indicator of metabolic control in diabetic patients.

Adolescent↗
PubMed1998

The use of scanning laser ophthalmoscope microperimetry to detect visual impairment caused by macular photocoagulation.

BACKGROUND AND OBJECTIVE: To demonstrate the effectiveness of scanning laser ophthalmoscope (SLO) microperimetry in detecting retinal sensitivity and in describing areas of unstable fixation following photocoagulation therapy. PATIENTS AND METHODS: Two patients with iatrogenic vision loss resulting from photocoagulation therapy underwent a fundus examination, SLO microperimetry, and fluorescein angiography. One patient also underwent indocyanine green angiography. RESULTS: Two types of visual acuity decrease--sudden-onset and late-onset--were demonstrated following macular photocoagulation, the former resulting from incorrect identification of the fixation point, and the latter from enlarging photocoagulation scars placed in close proximity to the fovea. In one case, SLO microperimetry detected dense scotoma corresponding to the patient's symptoms and an unstable fixation point. In the other case, different retinal sensitivities were found in the photocoagulation scars. No differences were found with fluorescein angiography or indocyanine green angiography. CONCLUSION: SLO microperimetry might be effective for quantitative assessment of retinal sensitivity in photocoagulation scars and for detecting fixation points and determining their stability.

Diabetic Retinopathy↗
PubMed1997

Changes in corneal and lens autofluorescence and blood glucose levels in diabetics: parameters of blood glucose control.

PURPOSE: We investigated corneal and lens autofluorescence in patients with proliferative diabetic retinopathy (PDR) to determine a correlation between the two parameters and blood glucose levels and HbA1c. METHODS: Corneal and lens autofluorescence levels in 17 PDR patients and 8 healthy controls were measured with a fluorophotometer fitted with an anterior segment adapter. We measured the lower blood glucose level (BS1), corneal autofluorescence (CA1), and lens autofluorescence (LA1) simultaneously and the higher blood glucose level (BS2), CA2, and LA2 simultaneously on the same day. We defined parameter changes as: delta BS = BS2 - BS1, delta CA = CA2 - CA1, and delta LA = LA2 - LA1. RESULTS: Corneal and lens autofluorescence significantly increased in the patients, compared with the controls (p < 0.001). Lens autofluorescence had a significant positive correlation with HbA1c (r = 0.656, p < 0.01) in the patients. delta CA (ngEq/ml) correlated significantly with delta BS (mg/dl) (r = 0.631, P < 0.01). CONCLUSIONS: Results suggest that lens autofluorescence might represent the long-term control of diabetes, and corneal autofluorescence levels may represent short-term changes in the blood glucose level, because hyperglycemia accelerates with increasing corneal autofluorescence in PDR patients. Corneal and lens autofluorescence may be related to the breakdown of the blood-aqueous barrier.

Adult↗
PubMed1997

Effect of timolol and UF-021 (a prostaglandin-related compound) on pulsatile ocular blood flow in normal volunteers.

The effects of topically applied timolol (a nonselective beta-blocker) and UF-021 (a prostaglandin-related compound) on pulsatile ocular blood flow (POBF) were investigated in 9 healthy volunteers. One drop of either UF-021 or timolol was instilled in one randomly selected eye and the fellow eye received physiologic saline. Before and 90 min after drop instillation, we measured intraocular pressure (IOP), POBF, heart rate (HR) and blood pressure (BP). After a washout interval of at least 1 week, the other drug was instilled in the previously treated eye. IOP, POBF, HR, and PB were measured following the same protocol. After timolol administration, IOP and POBF decreased significantly in the treated eye (26%, p = 0.01, and 13%, p = 0.02, respectively) and in the fellow eye (11%, p = 0.01, and 11%, p = 0.03, respectively). HR also decreased (10%, p = 0.03), but BP did not change significantly. After UF-021 administration, no significant changes were found in IOP, POBF, HR, or BP. Our results suggest that in normal subjects timolol decreases POBF in both the treated and the untreated eyes, whereas UF-021 has no action on either IOP or POBF.

Administration, Topical↗
PubMed1997

Cystoid macular edema as an initial symptom of inflammatory orbital pseudotumor.

We report a patient with pseudotumor with cystoid macular edema (CME). The initial finding in our case was only CME with a bilateral visual acuity decrease to 20/25. Approximately 3 months later, the visual acuity dropped to light perception in the right eye and 20/200 in the left eye. Computed tomography scan revealed a mass in the right orbital apex and band-shaped enhancement in the cavernous sinus and along the upper margin of the petrous bone. However, no mass was found intraoperatively, and a biopsy specimen of the bulging levator muscle showed polymorphonuclear leukocyte infiltration. The CME resolved postoperatively. The tumor also seemed to resolve; however, after 1 year, the tumor recurred and invaded the brain tissue. A temporal lobectomy revealed widespread inflammatory cell infiltration. To ensure early diagnosis, pseudotumor should be considered in patients with CME of which the cause is uncertain.

Adult↗
PubMed1997

[Early ocular changes in a tree shrew model of diabetes].

We developed a tree shrew model of diabetes using streptozotocin (STZ), and studied early ocular changes of diabetes (after one week of diabetes) by fluorophotometry. STZ was injected intraperitoneally at doses of sixty to 400 mg/kg body weight. Animals injected with more than 300 mg/kg of STZ developed diabetes. Corneal autofluorescence was significantly increased one week after STZ injection. These changes may be related to impairment of the ocular homeostatic mechanisms due to the onset of diabetes. Using this model, we might be able to obtain diabetic ocular impairment data closer to human data than in previous models of diabetes, because tree shrews are primates.

Animals↗
PubMed1996

Inward and outward permeability of the blood-retinal barrier in experimental myopia.

BACKGROUND: To investigate the pathophysiology of the retina in myopia, vitreous fluorophotometry was used to evaluate the permeability of the blood-retinal barrier (BRB) in experimentally induced myopia in cynomolgus monkeys. METHODS: Five animals underwent unilateral eyelid suturing. The suture was removed temporarily at 3, 10, 16, 28 and 36 months, and the dioptric power and axial length were measured in both eyes. Vitreous fluorophotometry was performed before and 60 min after intravenous injection of fluorescein-Na. BRB inward permeability (P(in)) was determined by a computer simulation method. At 36 months, fluorescein-Na was injected into the vitreous cavity, and the intraocular fluorescence was measured. BRB outward permeability (P(out)) was determined by the computer simulation method. RESULTS: Significant myopia developed by 10 months after suturing and progressed thereafter. Starting at 10 months, the P(in) of sutured eyes increased significantly compared with control fellow eyes, and the increase continued throughout the observation period. At 36 months, the BRB P(out) was significantly lower (P < 0.05) in the myopic than in the emmetropic fellow eyes, suggesting decreased active transport mechanisms at the BRB in myopia. CONCLUSION: Our study demonstrated, for the first time, abnormal permeability of the BRB in myopic monkey eyes. Such abnormal permeability may play an important role in the development in human myopes of retinal and vitreous changes such as retinal detachment. Thus, simply correcting refractive errors surgically may not represent a cure for myopia. Patients who have had refractive surgery to correct myopia should also be closely followed up by vitreo-retinal specialists to manage vitreo-retinal disorders in originally myopic eyes.

Animals↗
PubMed1996

Imaging of epiretinal membranes in macular holes by scanning laser ophthalmoscopy.

PURPOSE: Because recognition and removal of an epiretinal membrane are important in macular hole surgery, we used the scanning laser ophthalmoscope preoperatively to study epiretinal membranes in patients with idiopathic macular holes. METHODS: We studied 67 eyes (60 consecutive patients) with idiopathic macular holes. We evaluated the thickness and the extent of the epiretinal membrane by using a scanning laser ophthalmoscope. We then compared the fundus images obtained with the scanning laser ophthalmoscope with red-free monochromatic fundus photographs. RESULTS: Confocal imaging of the fundus with either argon blue (488 nm) or argon green (514 nm) laser illumination clearly showed the epiretinal membranes. In all eyes, we observed lesions ranging from a patchy glinting light reflex to a dense epiretinal membrane. A well-demarcated dense epiretinal membrane around the macular hole was observed in seven (44%) of 16 eyes with stage 2 macular holes and in 12 (40%) of 30 eyes with stage 3 holes, but in only two (10%) of 21 eyes with stage 4 holes. The prevalence of the dense epiretinal membrane in stage 2 or 3 holes was significantly higher than in stage 4 holes (P = .025 and .024, respectively). CONCLUSIONS: Fundus imaging using the scanning laser ophthalmoscope with argon laser illumination is useful preoperatively to evaluate epiretinal membranes in eyes with idiopathic macular holes.

Aged↗
PubMed1996

Lenticular autofluorescence in normal tree shrews.

Lenticular autofluorescence was measured in vivo in 25 normal tree shrews using a fluorophotometer with a specially designed small animal adapter to assess the usefulness of this model of lens pathology. The average variability in the lenticular autofluorescence measurements was 8.7%. The average ratio between lenticular autofluorescence of the left eye and that of the right eye was 0.99 +/- 0.13 SD. There was a strong correlation between age and mean lenticular autofluorescence in both eyes (correlation coefficient, 0.988; p < 0.001). The calculated annual increase in lenticular autofluorescence was 23.7 ngEq/ml. This method of measurement is reliable, and lenticular autofluorescence in tree shrews varies little among animals other than a variation caused by aging. Moreover, the tree shrew, which is believed to be a primate, is small and easy to breed. This could be a useful animal model to study various lens pathologies in humans.

Aging↗
PubMed1996

[Fluorophotometry of the animal eye].

We assessed the usefulness of the Fluorotron Master fitted with a small animal adapter. We also discuss the measurement conditions for the tupai, which is a promising experimental mammal. A good concentration for measurements with this instrument ranged from 0.5 x 10(-6) to 1.0 x 10(-6) g/ml. A suitable time for fluorophotometry of the tupai was 30 min. after injection of fluorescein-Na, and a suitable dose of the fluorescein-Na was 2 mg/kg. We could do ultrafiltration for measurement of the protein unbound fluorescein concentration from a minimal sample of the blood using a hematocrit tube, and thus could reduce the deleterious effects of blood sampling on the animal. This instrument is useful for the estimation of the blood-ocular barrier permeability of animal models.

Animals↗
PubMed1996

Differential diagnosis of macular breaks by microperimetry using the scanning laser ophthalmoscope.

To improve the differential diagnosis of macular breaks by microperimetry using the scanning laser ophthalmoscope (SLO), we studied 50 consecutive breaks detected by biomicroscopy and indirect ophthalmoscopy. The full-thickness macular break was easily diagnosed using only biomicroscopy and indirect ophthalmoscopy because the macular break had a cuff in 22 of the eyes. SLO microperimetry also showed an absolute scotoma within the macular break and a relative scotoma on the cuff in these 22 eyes. However, in the other 28 eyes it was impossible to distinguish between the full-thickness macular breaks and pseudo-macular breaks or lamellar macular breaks using only biomicroscopy and indirect ophthalmoscopy because of the absence of a cuff. However, SLO microperimetry differentiated full-thickness macular breaks from pseudomacular breaks or lamellar macular breaks in these 28 eyes. SLO microperimetry is indispensable for determining the prognosis of and the surgical indication requirements for idiopathic macular breaks.

Diagnosis, Differential↗
PubMed1996

Fluorophotometry with a small animal adapter.

The usefulness of the Fluorotron Master fluorophotometer fitted with a small animal adapter was evaluated with tree shrews. We also determined that the optimal measurement parameters for these animals, which are regarded as promising for experimental use in ophthalmic research, are: fluorescein-Na concentration, 0.5 x 10(-9) to 1.0 x 10(-6) g/mL; fluorescein-Na dosage, 2 mg/kg; measurement time, 30 minutes after injection of fluorescein-Na into the ocular compartments. Results indicated that ultrafiltration for the measurement of protein-unbound fluorescein can be done with a hematocrit tube and a minimal blood sample, thereby reducing the impact of the sampling on the animal's general condition. The Fluorotron Master with the small animal adapter can offer advantages in estimating the blood-ocular barrier permeability using disease models in tree shrews.

Animals↗
PubMed1995

[Vitreous videography with a scanning laser ophthalmoscope].

We used a scanning laser ophthalmoscope (SLO) to attempt better visualization of the posterior vitreous than conventional biomicroscopy. We observed the posterior vitreous using the SLO in patients with age- or disease-related vitreous changes. We compared the results using lasers of several wavelengths. The detailed structure of the posterior hyaloid membrane, its collagen mesh structure with premacular defect, and the prepapillary glial ring were clearly visualized by direct laser illumination. Persistent attachment of the vitreous gel to the macula through the oval defect in the posterior hyaloid membrane was seen even with repeated eye rotations. Short wavelength laser was preferable to a long wavelength one for observing the posterior hyaloid membrane. Vitreous opacities were clearly visualized with all lasers as dark spots with fundus monitoring by retro illumination. Thus in vivo visualization of the posterior hyaloid membrane and vitreous gel was achieved using this new technique, which is more advantageous than the conventional biomicroscopy because of its monochromatic laser delivery system with confocal light detection.

Adolescent↗
PubMed1995

[Differential diagnosis of macular breaks by microperimetry with a scanning laser ophthalmoscope].

To improve differential diagnosis of macular breaks, microperimetry with a scanning laser ophthalmoscope (SLO) was performed. Fifty consecutive macular breaks were detected by biomicroscopy and indirect ophthalmoscopy, and SLO microperimetry was performed on each. Of the 50 eyes, 22 eyes were diagnosed with idiopathic macular breaks by biopmicroscopy and indirect ophthalmoscopy because of a cuff. SLO microperimetry also showed dense scotoma within the macular break and relative scotoma on the cuff in the 22 eyes. However, diagnosis was not done only by biomicroscopy and indirect ophthalmoscopy in the other 28 eyes because of the absence of a cuff. SLO microperimetry differentiated the full thickness macular breaks from pseudo-or lamellar breaks in these eyes. SLO microperimetry is useful for differentiating their prognosis, and determining the need for surgical treatment.

Aged↗
PubMed1995

Vitreous videography using the scanning laser ophthalmoscope.

To establish the method of vitreous videography using the scanning laser ophthalmoscope, we observed the vitreous in patients with age- or disease-related vitreous changes. We compared the results using four laser wavelengths. The detailed structures of the posterior vitreous cortex, a premacular defect, and a prepapillary glial ring were clearly shown under direct laser illumination. A short wavelength laser was found to be superior to a long wavelength laser for observing the posterior vitreous cortex. Vitreous opacities were clearly shown as dark spots under retroillumination using any of the four laser wavelengths. In vivo visualization of the vitreous was achieved using this new technique, which is superior to conventional biomicroscopy because of its monochromatic laser delivery system and confocal light detection capacity.

Adolescent↗
PubMed1993

Permeability of the blood-ocular barrier in adolescent and adult diabetic patients.

The permeability of the blood-ocular barrier was examined by fluorophotometry in adolescent and adult diabetic patients before the onset of retinopathy. The adolescent group consisted of 52 eyes of 52 insulin dependent diabetic patients aged 11 to 19 years and a control group of 10 eyes of 10 normal adolescents. The adult group consisted of 74 eyes of 74 non-insulin dependent diabetics and a control group of 30 eyes of 30 normal adults. The increase in lens autofluorescence in the adolescent diabetic patients compared with the controls was striking and showed a significant positive correlation (r = 0.79, p < 0.0001) with the duration of diabetes. Anterior chamber (AQ) values, an index of the permeability of the blood-aqueous barrier (BAB), increased in the adolescent diabetic patients compared with the controls and showed a significant positive correlation with glycosylated haemoglobin levels. No significant differences from the controls were observed regarding the permeability of the blood-retinal barrier (BRB). In the adult group there was no significant difference in either the permeability of the BRB or the AQ values between the diabetic and the control groups. Our results suggest that adolescent diabetic patients differ from adults in that BAB permeability is increased before the onset of retinopathy, suggesting that this is the cause of the striking increase in lens autofluorescence.

Adolescent↗