Joji Takenaka

Comparison of the prevalence of plateau iris configurations between angle-closure glaucoma and open-angle glaucoma using ultrasound biomicroscopy.

PurposeTo determine the prevalence of plateau iris configurations in acute primary angle-closure (APAC), chronic angle-closure glaucoma (CACG), and open-angle glaucoma (OAG) eyes using ultrasound biomicroscopy. Materials and MethodsThe study included fellow eyes of 27 APAC patients, 26 OAG patients, and 26 CACG patients with no history of APAC. Patients with a history of earlier intraocular surgery or argon laser peripheral iridoplasty were excluded from the study. Eyes that had not undergone laser peripheral iridotomy were excluded from APAC and CACG groups. Radial scans were carried out using ultrasound biomicroscopy in all 4 quadrants. A plateau iris configuration within a quadrant was defined by the presence of an anteriorly positioned ciliary process, a narrow ciliary sulcus, a steeply rising peripheral iris, followed by a downward angulation from the corneoscleral wall and the presence of a flat iris plane. Eyes with plateau iris configurations were defined as those having at least 2 quadrants fulfilling these criteria. ResultsPlateau iris configurations were found in fellow eyes of 10 of 27 patients with (37.0%) APAC, 9 of 26 (34.6%) patients with CACG, and 5 of 26 (19.2%) patients with OAG. No significant difference in the prevalence of plateau iris configurations was observed among the 3 groups (P=0.314, &khgr;2 test). ConclusionsEyes with OAG had a higher rate of plateau iris configurations than expected. Longitudinal studies to evaluate plateau iris height are required to determine its significance in the pathogenesis of angle-closure glaucoma.

Evaluation of Rebound Tonometer for Measuring Intraocular Pressure at Deviated Angle and Position

Purpose: To investigate the influence of positional deviations on the rebound tonometer measurement. Materials and Methods: Ten white rabbits were used. A bottle of balanced salt solution was connected to the anterior chamber, and the IOP was altered by changing the height of the bottle. A pressure transducer was also connected to the anterior chamber. The IOP was measured by the rebound tonometer (RBT), the Tonopen XL, and the Perkins handheld applanation tonometer at optimal conditions and compared each tonometer. Then, the effect of placing the RBT probe at different distances, different lateral positions, and different angles to the cornea on the IOP was determined. Results: The RBT had the lowest variance in all three tonometers. The IOP measured with the RBT was not significantly altered when the distance from the cornea was 4 to 8 mm, or when the probe was displaced 2 mm to the central cornea, or when the probe was placed at an angle of 20° from the central axis. Conclusions: The low variance of the RBT measurements and the non-significant changes in the IOP when the probe of the RBT was not on the central axis indicate that the RBT is useful for animal models of glaucoma. Further studies examining its use (repeatability and reliability) in human infants whose eyes and head are usually moving are required.

Matrix metalloproteinase and cytokine expression in Tenon fibroblasts during scar formation after glaucoma filtration or implant surgery in rats

Failure of surgery for glaucoma is usually due to post‐surgical scarring (fibrosis), a process in which fibroblasts play a prominent role. We investigated the molecular mechanisms of such scarring by examining the expression of matrix metalloproteinases and cytokines in Tenon fibroblasts isolated from rats after glaucoma surgery. Filtration surgery was performed in one eye and implant surgery in the other; and Tenon fibroblasts were isolated from the tissue surrounding the bleb after surgery. The cells were cultured and examined for the expression of matrix metalloproteinases (MMPs) by reverse transcription‐polymerase chain reaction, immunoblot and gelatin zymographic analyses. Culture supernatants were also assayed for cytokines with a multiplex array. The amounts of MMP‐1 and MMP‐3 mRNAs and proteins were greater in cells isolated after implant surgery than in those isolated after filtration surgery, with the progression of scar formation being more complete after the former surgery. The secretion of interleukin‐6 (IL‐6) by cells isolated after filtration surgery was greater than that for cells isolated after implant surgery. Depletion of IL‐6 by RNA interference in cells isolated after filtration surgery increased the expression of MMP‐1 and MMP‐3 in these cells. These results thus suggest that the expression of MMP‐1 and MMP‐3 in Tenon fibroblasts is regulated by IL‐6 during, and may play an important role in, scar formation after glaucoma surgery. Copyright

Intraocular Pressure Measurement Using Rebound Tonometer for Deviated Angles and Positions in Human Eyes

Purpose: To investigate the influence of positional deviations on rebound tonometer measurement of intraocular pressure in humans. Materials and methods: Intraocular pressure was measured using the Icare rebound tonometer on the right eyes of 53 subjects in various conditions as follows: first, at a distance of 4, 6, or 8 mm from the center of the cornea with the probe perpendicular to the corneal plane; then, at 2 mm from the limbus in the nasal and temporal regions with the probe perpendicular to the corneal plane or along the visual axis; and lastly, with the angled probe touching the central cornea at angles of 10° or 20°. Results: Bland–Altman plots between the Goldmann applanation tonometer and rebound tonometer at various conditions revealed 95% limits of agreement ranging from ±4.5 to ±5.6 mm Hg. Intraocular pressures measured using the rebound tonometer were significantly lower than those measured using the Goldmann applanation tonometer when the rebound tonometer probe was placed 2 mm from the limbus in the temporal or nasal regions with the probe along the visual axis or when the probe was angled to touch the central cornea at an angle of 10° or 20°. In other positions, the intraocular pressures measured using the rebound tonometer were not significantly different. The rebound tonometer, noncontact tonometer, and Tonopen XL showed good agreement with the Goldmann applanation tonometer for intraocular pressure readings under optimal conditions. Conclusions: The intraocular pressures determined using the rebound tonometer were approximately equal to those obtained using the Goldmann applanation tonometer when the rebound tonometer measurements were made with the probe perpendicular to the corneal plane, irrespective of the location, that is, at the central cornea or 2 mm from the limbus.

Evaluation of corneal displacement using high-speed photography at the early and late phases of noncontact tonometry.

PURPOSE We investigated the extent of corneal displacement and factors associated with the measurement of IOP during the early and late phases of noncontact tonometry. METHODS One eye in each of 61 healthy volunteers was studied. In each case, the cornea was photographed in profile using a high-speed camera during noncontact tonometry. The extent of displacement at the corneal center, and at the midperipheral corneal areas at 13.2 and 30.0 ms after the application of an air puff was recorded. For each measurement point, multiple regression analyses were performed against age, sex, axial length, corneal curvature, IOP, and central corneal thickness (CCT) to determine the independent predictors of corneal displacement. Multiple comparison tests were used to determine whether the displacement differences were associated with age or sex. RESULTS Our results showed that the factors most associated with corneal displacement were the IOP (P < 0.001) and CCT (P = 0.02) at the corneal center at 13.2 ms, the CCT (P = 0.041) at the corneal midperiphery at 13.2 ms, age (P < 0.01) at the corneal center at 30.0 ms, and age (P = 0.04) and IOP (P = 0.04) at the corneal midperiphery at 30.0 ms. Young females had the smallest amounts of corneal displacement at all measurement points, and elderly females had largest amounts of displacement at the late phase of tonometry. CONCLUSIONS The amount of corneal displacement is affected by an individuals IOP, age, and CCT. Our findings indicated that the corneas of females may be more susceptible to aging than those of males.

Ocular Surface Displacement with and without Contact Lenses during Non-Contact Tonometry

Purpose To evaluate the displacement of the central ocular surface during non-contact tonometry with and without soft contact lenses and determine the factors associated with the displacement of the central ocular surface and intraocular pressure (IOP) reading changes caused by wearing soft contact lenses (CLs). Methods One eye each in 21 subjects was studied. The cornea was photographed using a high-speed camera at 5,000 frames/sec during non-contact tonometry without contact lenses (NCL), with -5.0 diopters (D), -0.5 D and +5.0 D CL. The displacement of the ocular surface and the factors affecting displacement at the IOP reading and maximum displacement time were investigated. Results The IOP readings while wearing +5 D CL were significantly higher than those obtained while wearing -5 D CL. The ocular surface displacement between +5 D CL and other groups were significantly different. A significant positive correlation was found between the ocular surface displacement of subjects at the IOP reading time and the IOP obtained with the non-contact tonometer. A significant negative correlation was found between the ocular surface curvature and the IOP obtained using the non-contact tonometer. The radius of curvature of the ocular surface affected the displacement during the IOP reading and maximum displacement time. Conclusions Our results indicate that soft contact lens use changes the ocular surface behavior and IOP readings during non-contact tonometry. The radius of curvature of the eye affects the ocular surface displacement and IOP readings in this situation.

Reproducibility of optic disk evaluation in supine subjects with a Heidelberg Retina Tomograph II laser tomographic scanner.

Aim The aim of this study was to determine the reproducibility and reliability of optic disk evaluation in supine subjects with a Heidelberg Retina Tomograph II (HRT II). Methods One eye was randomly selected for evaluation by HRT II in each of eleven healthy subjects. Five images were obtained by each of two experienced operators at two separate visits with the subjects in both sitting and supine positions. A stand was constructed to allow stable, handheld operation of the HRT II head for imaging of the supine subjects. Measurements of optic disk parameters obtained in the supine position were compared with those obtained in the sitting position. The reliability of measurements in the supine position was evaluated by calculating both the coefficients of variation for measurements made by one observer on the first visit and the interobserver and intervisit intraclass correlation coefficients (ICCs); the values obtained were compared with those obtained for the sitting position. Results Measurements of all parameters made in the supine position were highly similar to those made in the sitting position. The coefficients of variation obtained for each parameter in the sitting and supine positions ranged from 5.67% to 14.16% and from 2.18% to 16.08%, respectively. The interobserver ICC values in the sitting and supine positions were ≥0.978 and ≥0.989, respectively. The intervisit ICC values in the sitting and supine positions were ≥0.958 and ≥0.983, respectively. Conclusion Handheld operation of the HRT II in a custom-designed stand is feasible for optic disk evaluation in the supine subjects who were not able to maintain the sitting position.

intraocular pressure readings obtained through soft contact lenses using four types of tonometer

Purpose To compare the reliability and accuracy of intraocular pressure (IOP) measured while wearing soft contact lenses (SCLs) using a non-contact tonometer (NCT), Goldmann applanation tonometer (GAT), iCare rebound tonometer (RBT) and the Tono-Pen XL. Methods Twenty-six healthy subjects were examined. The IOP was measured using NCT, GAT, RBT, and the Tono-Pen XL, while the subjects wore SCLs −5.00 D, −0.50 D and +5.00 D. Bland–Altman plots and a regression analysis were used to compare the IOPs obtained with those instruments and the IOPs of the naked eyes measured using GAT (the standard IOPs in this study). Results The IOPs obtained by the Tono-Pen XL while the subjects were wearing −5.00 D, −0.50 D, and +5.00 D SCLs were significantly higher than those of the naked eyes obtained using GAT. RBT showed that the IOPs were similar to the GAT standard IOPs under all conditions. The IOPs measured with NCT and GAT while the subjects were wearing −5.00 D and −0.50 D SCLs were similar to the GAT standard IOPs. The IOPs obtained with RBT and NCT while the subjects were wearing −5.00 D and −0.50 D SCLs exhibited a good correlation with the standard IOPs. Conclusion The NCT and RBT are best when measuring IOP through hydrogel SCLs.