Performance of and Pressure Elevation Formed by Small-diameter Microtubes Used in Constant-flow Sets

PURPOSE: We explored the performance of and pressure elevation caused by small-diameter microtubes used to reduce overfiltration. METHODS: Using a syringe pump-driven constant-flow setting (2 µL/min), pressures were measured for polytetrafluoroethylene (PTFE) microtubes 5 mm in length with inner diameters of 51, 64, and 76 µm and for polyether block amide (PEBAX) microtubes with an inner diameter of 76 µm. Experiments (using microtubes only) were initially performed in air, water, and enucleated pig eyes and were repeated under the same conditions using intraluminal 9/0 nylon stents. RESULTS: The pressures measured in air in 51-, 64-, and 76-µm-diameter PTFE microtubes differed significantly (22.1, 16.9, and 12.2 mmHg, respectively; p < 0.001), and that of the 76-µm-diameter PEBAX microtube was 15.8 mmHg (p < 0.001 compared to the 12.2 mmHg of the 76-µm-diameter PTFE microtube). The pressures measured in water also differed significantly among the three microtubes at 3.9, 3.0, and 1.4 mmHg, respectively, while that in the PEBAX microtube was 2.6 mmHg (all p < 0.001). Using the intraluminal stent, the pressure in water of the three different PTFE microtubes increased to 22.6, 18.0, and 4.1 mmHg, respectively, and that in the PEBAX microtube increased to 10.5 mmHg (all p < 0.001). Similar trends were evident when measurements were performed in pig eyes. CONCLUSIONS: Although microtubes of smaller diameter experienced higher pressure in air, reduction of the inner diameter to 51 µm did not adequately increase the pressure attained in water or pig eyes. Insertion of an intraluminal stent effectively elevated the latter pressures. PEBAX microtubes created higher pressures than did PTFE microtubes.

Influence of Myopia on the Progression of Normal Tension Glaucoma

PURPOSE: To evaluate the influence of myopia on the progression of normal tension glaucoma. METHODS: A retrospective study of 72 patients with normal tension glaucoma who were treated from 1984. Subjects were divided into 4 groups which are myopic group (D-1). The change of MD (Mean deviation) and CPSD (corrected pattern standard deviation) of non-myopic group were compared to other myopic groups. In addition, we corrected each analysis in commensurate with age, basal IOP, post treated IOP, existence of hypertension and diabetes mellitus in order to preclude the possibility which these factors would influence to the progression. RESULTS: There was no statistically significant difference between non-myopic group and each myopic groups in MD and CPSD changes against refraction. Moreover, with the correction of other factors, there was no statistically significant difference (Mixed method, P>0.1). CONCLUSIONS: Myopia did not affect the progression of normal tension glaucoma once treated.

Clinical Manifestations and Molecular Biologic Diagnosis of Herpetic Glaucoma

PURPOSE: We attempted to detect the herpes virus using a polymerase chain reaction (PCR) technique from the aqueous humor of patients who were suspected of having herpetic uveitis. METHODS: We obtained aqueous humor from four patients who suffered from elevated intraocular pressure and uveitis but did not respond to steroid and intraocular pressure depressants. We employed the PCR technique for to detect herpes-virus specific DNA. Patients were treated with oral and topical acyclovir. RESULTS: Uveitis of varying severity and progressive iris atrophy was observed in all patients. Varicella zoster virus (VZV) specific DNA was detected in two of four patients. Two patients showed a favorable course but the other two patients showed an unfavorable course due to advanced peripheral anterior synechia and corneal decompensation. CONCLUSIONS: Diagnosis of herpetic uveitis was difficult because it was not usually accompanied by dendritic corneal lesions. Herpetic uveitis should be considered whenever anterior uveitis and elevated intraocular pressure accompanies the characteristic iris atrophy. PCR was very useful in detecting the virus DNA in the aqueous humor to enable rapid diagnosis and adequate treatment.

The Change of Axial Length after Laser in-Situ Keratomileusis

PURPOSE: We prospectively conducted this study to evaluate the effect of laser in-situ keratomileusis (LASIK) on axial length because axial length is an important varible for IOL power calculation. METHODS: One hundred three eyes of fifty two myopic patients had measurements of axial length, ultrasonic central pachymetric readings and otherwise preoperatively and 3 months after LASIK. RESULTS: The axial length and central corneal thickness were reduced statistically significant 3 months after LASIK by 66+/-0.28 micrometer and 57+/-23 micrometer respectively (P0.05) CONCLUSIONS: But the reduction of axial length after LASIK is so small that very small influence is expected on IOL power calculation for the patient who had previous LASIK. So when preoperative IOL power calculation is done using historical method, post-LASIK axial length can be replaced for pre-LASIK axial length to calculate proper IOL power for cataract surgery.

Astigmatism in Children with Epiblepharon

PURPOSE: To compare the prevalance and the amount of astigmatism between the epiblepharon patients who had been operated epiblepharon and normal school children. METHODS: The noncycloplegic refraction using autorefractor was performed in 120 epiblepharon patients from Jan. 1997 to June 2000. Astigmatism in excess of 0.5 D was studied. We compared the findings of epiblephron patients and 443 normal school children in Seoul. RESULTS: The prevalence of astigmatism was 72.9% in epiblephron group and 41.6% in normal children group, and the difference was statistically significant (P< 0.001). The amount of astigmatism was 1.52 D and 0.73 D in each group, and the difference was statistically significant (P< 0.001).The distribution of astigmatism showed 1.0 D or less in 22.5%, from above 1.0 D to 2.0 D or less in 26.3%, from above 2.0 D to 3.0 D or less in 10.8%, from above 3.0 D to 4.0 D or less in 9.6% and above 4.0 D in 3.8% in epiblepharon group and in normal children group 26.2%, 11.2%, 2.6%, 1.0%, and 0.7% respectively. The difference between both groups was statistically significant (P< 0.001). With-the-rule astigmaism was found in 77.9% and against-the-rule was 22.1% in epiblephron group and 72.8% and 27.2% respectively in normal children group. CONCLUSIONS: The prevalence and the amount of astigmatism were higher in epiblepharon group than in normal children group. It might be caused by the increase of orbicularis muscle tone and the effect of skin fold overriding lid margin in epiblepharon patients.

The Biomicroscopic Variations of Posterior Vitreous Detachments

We performed this study to identify the biomicroscopic variations of posterior vitreous detachment(PVD)and to evaluate the clinical relationship of the vitreoretinal pathology and variations of PVD. Three hundred eyes with PVD were examined with biomicroscope using a 3CCD camera and a personal computer developed by us. The biomicroscopic variations were classifed as complete PVD with collapse, complete PVD without collapse, partial PVD with TPVC(thickened posterior vitreous cortex), or partial PVD without TPVC. In each type, the following pathologies were frequently observed :in complete PVD with collapse(150 eyes), age related changes without vitreoretinal diseases(72 eyes, 48%)and high myopia(41 eyes, 27.3%), in complete PVD without collapse(96 eyes), age related changes without vitreoretinal diseases(33 eyes, 34.3%), nonproliferative diabetic retinopathy(20 eyes, 20.8%), high myopia(15 eyes, 15.6%), branch retinal vein occlusion(14 eyes, 14.5%), in partial PVD with TPVC(36 eyes), proliferative diabetic retinopathy(18 eyes, 50%)and uveitis(10 eyes, 27.7%)and in partial PVD without TPVC(18 eyes), age related changes without vitreoretinal diseases(9 eyes, 50%). The type of PVD was significantly associated with the prevalence of each vitreoretinal disease(P<0.001). Biomicroscopic variations of PVD can be classified into four types, which was useful to evaluate the certain vitreoretinal disorders.