Histopathological Changes by Low-Power-Long-Duration and High-Power-Short-Duration Subthreshold Laser Treatment in the Rabbit Retina

PURPOSE: To compare histopathological and apoptotic changes of ophthalmoscopically similar subthreshold laser burns made by a low power-long duration (LD) and a high power-short duration (SD) subthreshold laser treatment. METHODS: Ophthalmoscopically invisible subthreshold laser burns with a 3.0 mm spot size were made using an 810 nm diode laser on the rabbit retina. Lasers were applied for 60 seconds in the LD group, and 1 second in the SD group. Laser power was adjusted to achieve ophthalmoscopically invisible burns just below the threshold. The rabbits were sacrificed at 6, 12, 24, and 72 hours, 1, 2, and 4 weeks after laser treatment. The eyes were processed for light microscopic examination using hematoxylin and eosin (H&E), toluidine blue, and TdT-dUTP terminal nick-end labeling (TUNEL) staining. Eyes were also processed for electron microscopic examination. RESULTS: The changes in the retina were different between the two groups. The LD group showed abundant TUNEL positive cells in all the retinal layers at 6 hours after laser treatment, and distinct histological changes in the outer nuclear layer. Conversely, in the SD group, apoptosis did not occur and histological alteration in the outer nuclear layer was minimal. CONCLUSIONS: Subthreshold laser treatment for 1 second reduced damage of the inner retinal layer and did not result in apoptosis in the neurosensory retina while maintaining a similar effect on the RPE and its adjacent region.

Analysis of Localized Retinal Nerve Fiber Layer Defects not Detected by Optical Coherence Tomography

PURPOSE: To analyze localized RNFL defect cases that were identified in retinal nerve fiber layer (RNFL) fundus photographs but not in optical coherence tomography (OCT). METHODS: Analysis of OCT scans and images was performed for 14 eyes (17 locations) that showed localized RNFL defects in RNFL fundus photographs but not in RNFL thickness average analysis. RESULTS: With respect to the range of RNFL defects, 41.2% were less than 10degrees, 47.0% were 11 to 20degrees, and 11.8% were 21 to 30degrees. In 71.4% of the RNFL cases the defects were less than 10degrees and the decrease of RNFL thickness was not readily observable on the OCT scan images. In all cases of RNFL defects in the 11 to 30degrees range the decrease in RNFL thickness could be assessed on the OCT scan images. Nonetheless, the decrease of RNFL thickness could not be seen on the OCT analysis images in which the results of the RNFL thickness made through an automated computer algorithm were displayed. CONCLUSIONS: The range of localized RNFL defects that were difficult to detect with OCT consisted of those cases that were almost less than 20degrees. The limitations of the OCT scan itself in patients with RNFL with an angular width defect less than 10degrees and the problems of RNFL thickness analysis processing in patients with an angular width of 11 to 30degrees may decrease the sensitivity of OCT in diagnosing RNFL defects.

Reorganization of Photoreceptor Layer on Optical Coherence Tomography Concurrent with Visual Improvement after Macular Hole Surgery

To report three cases in which reorganization of the photoreceptor layer on optical coherence tomography (OCT) was concurrent with long-term visual recovery after macular hole surgery. Serial OCT scans of three eyes in which visual acuity continued to improve for 1 or more years after successful macular hole surgery were reviewed. Case 1. At postoperative four weeks, visual acuity was 20/100 with disorganized photoreceptor layer on OCT. The photoreceptor layer had been reorganized and visual acuity had improved to 20/25 by 1 year. Case 2. Two weeks after the operation, visual acuity was 20/125 and disorganization of the photoreceptor layer was noted. Visual acuity improved to 20/50 by four months. The photoreceptor layer had been partly reorganized and had appearance of a broken line. Visual acuity had improved to 20/40 and the photoreceptor layer had been reorganized further with a residual defect on OCT by 15 months. Case 3. Visual acuity at two weeks was 20/100. OCT revealed disorganization of the photoreceptor layer. Six months after the operation, the partly reorganized photoreceptor layer appeared as a broken line and visual acuity had reached 20/80. Visual acuity had improved further to 20/40 by 1 year, concurrent with improved organization of the photoreceptor layer. The reorganization of the photoreceptor layer plays a part in long-term improvement of visual acuity after macular hole surgery.

Triamcinolone-Induced Intraocular Pressure Elevation: Intravitreal Injection for Macular Edema and Posterior Subtenon Injection for Uveitis

PURPOSE: To assess the effect of intravitreal and posterior subtenon injections of triamcinolone acetonide (TA) on intraocular pressure (IOP). METHODS: we reviewed 42 consecutive eyes after intravitreal TA injection (IVTA) and 43 eyes following posterior subtenon TA injection (PSTA). All cases had a minimum follow-up time of three months. After injection, the value and time of the maximal IOP, the amount of IOP elevation and the needs of the medication were assessed. RESULTS: The IOP increased significantly (p<0.001) from 16.3+/-2.5 mmHg preoperatively to a mean maximum of 21.7+/-5.3 mmHg in the IVTA group, and from 15.3+/-4.5 mmHg to 20.6+/-3.0 mmHg in the PSTA group. An elevation in the IOP of more than 5 mmHg from the baseline IOP was seen in 52.4% of the IVTA group at a mean time of 3.1 weeks postoperatively, and 44.2% of the PSTA group displayed an IOP elevation at 5.9 weeks. CONCLUSIONS: Both developed significant elevations of IOP, but this appeared at a later date in the PSTA group. Careful follow-up after local injection of steroids is necessary.

Experimental Model for Research on the Blood-Ocular Barrier

PURPOSE: The eyeball has 2 blood-ocular barriers, i.e., the blood-retinal and blood-aqueous barriers. The purpose of this study was to evaluate if triolein emulsion could disrupt the barriers, and we wanted to suggest as an experimental model for future blood-ocular barrier studies. MATERIALS AND METHODS: The triolein emulsion was made of 0.1 ml triolein and 20 ml normal saline, and this was infused into the carotid artery of ten cats (the experimental group). As a control group, only normal saline was infused in another ten cats. Precontrast and postcontrast T1-weighted MR images were obtained at 30 minutes and 3 hours after embolization in both groups. The signal intensities were evaluated qualitatively and quantitatively in the anterior and posterior chambers and also in the vitreus fluid. Statistical analysis was performed by employing the Kruskal Wallist test, Dunn's Multiple Comparison test and the Wilcoxon signed rank test. RESULTS: In the control group, no contrast enhancement was demonstrated in the anterior or posterior chamber or in the vitreus fluid of the ipsilateral or contralateral eyeball on the 30 minutes MR images. The anterior chambers of the ipsilateral and contralateral eyeballs revealed delayed contrast enhancement on the 3 hour MR images. In the experimental group, the 30 minute-postembolization MR images were not different from those of the control group. The 30 minute-postembolization MR images demonstrated delayed contrast enhancement in the anterior chamber of the ipsilateral and contralateral eyeballs and in the posterior chamber of the ipsilateral eyeball. The delayed contrast enhancement of the posterior chamber of the ipsilateral eyeball was statistically significant (p<0.05). CONCLUSION: The present study demonstrated significant contrast enhancement in the posterior chamber with infusion of the triolein emulsion, and this can serve as a model for blood-aqueous barrier studies.

Effects of Varying the Mitomycin C Subconjunctival Injection Time in Glaucoma Filtration Surgery in Rabbits

PURPOSE: To investigate the effects of varying the time of Mitomycin-C (MMC) subconjunctival injection before, during and after operation. METHOD: We divided rabbits into 3 groups according to injection time. Subconjunctival injections of 0.01% MMC 0.05 ml were given to the preoperative group at 6, 12 and 24 hours before operation, and to the postoperative group at 6, 12 and 24 hours after operation. The control group was given the injections during operation. Bleb formation and histologic analyses were studied for 4 weeks after operation. RESULTS For gross findings, the blebs of the preoperative and control groups were seen on the fourth day and completely formed at one week after operation, and were larger than those of the postoperative group. On the other hand, the blebs of the postoperative group were seen to have poor formation, displaying hypervascularity on the fourth day and disappearing one week after operation. For histologic findings, the proliferation of collagen fibers and the undifferentiation of fibroblasts observed in the preoperative and control groups were almost identical. But, the proliferation of collagen fibers and well-differentiated fibroblasts were seen to increase in the postoperative group, so aqueous flow was obstructed at week 3. CONCLUSIONS: Subconjunctival injections within 24 hours before or during glaucoma filtration surgery were better for bleb formation and preservation than those administerd after surgery.

Effects of Varying the Mitomycin C Subconjunctival Injection Time in Glaucoma Filtration Surgery in Rabbits

PURPOSE: To investigate the effects of varying the time of Mitomycin-C (MMC) subconjunctival injection before, during and after operation. METHOD: We divided rabbits into 3 groups according to injection time. Subconjunctival injections of 0.01% MMC 0.05 ml were given to the preoperative group at 6, 12 and 24 hours before operation, and to the postoperative group at 6, 12 and 24 hours after operation. The control group was given the injections during operation. Bleb formation and histologic analyses were studied for 4 weeks after operation. RESULTS For gross findings, the blebs of the preoperative and control groups were seen on the fourth day and completely formed at one week after operation, and were larger than those of the postoperative group. On the other hand, the blebs of the postoperative group were seen to have poor formation, displaying hypervascularity on the fourth day and disappearing one week after operation. For histologic findings, the proliferation of collagen fibers and the undifferentiation of fibroblasts observed in the preoperative and control groups were almost identical. But, the proliferation of collagen fibers and well-differentiated fibroblasts were seen to increase in the postoperative group, so aqueous flow was obstructed at week 3. CONCLUSIONS: Subconjunctival injections within 24 hours before or during glaucoma filtration surgery were better for bleb formation and preservation than those administerd after surgery.

Quantified Values of Anterior Chamber Depth and Angle Measurements Using Ultrasound Biomicroscopy and Topography

PURPOSE: To compare the measured values of anterior chamber depth and angle in glaucoma patients using Ultrasound Biomicroscopy (UBM) and Orbscan(TM) IIz Topography. METHODS: We measured the anterior chamber depth and angles of four directions in 26 eyes of 13 primary open angle glaucoma (POAG) patients, 26 eyes of 13 normal tension glaucoma (NTG) patients, and 20 eyes of 10 angle closure glaucoma (ACG) patients, with UBM and Orbscan. RESULTS: The values of anterior chamber depth did not show any difference between UBM and Orbscan. The values for anterior chamber angle in POAG and NTG eyes were not different between UBM and Orbscan, but the values for all anterior chamber angles except the superior angle, measured with UBM were significantly larger than those for ACG measured by Orbscan. CONCLUSIONS: Both UBM and Orbscan showed similar results in the measurement of anterior chamber depth and angle in POAG and NTG patients, but showed different results in the anterior chamber angle for ACG patients. UBM will be more useful in evaluating the anterior chamber angle in ACG patients because it can assess the structures of the anterior chamber angle objectively.

Decompression Retinopathy after Trabeculectomy

PURPOSE: To present a case of a unilateral diffuse retinal hemorrhage in a 15-year-old girl, who underwent bilateral trabeculectomy for steroid induced glaucoma. METHODS: Despite the maximally tolerable medical treatment, IOP in the right eye remained above 50 mmHg for four months, and was simultaneously elevated in the left eye. So we performed bilateral trabeculectomy. RESULTS: On the first postoperative day, diffuse retinal hemorrhages were observed in the right eye; however, no retinal hemorrhage was found in the left eye. The hemorrhages resolved completely without consequences two months later. CONCLUSIONS: In the case of high IOP for a long period, sudden lowering of IOP may acutely increase the blood flow and consequently rupture multiple retinal capillaries because of altered autoregulatory function. Special care is therefore needed to prevent an abrupt fall in IOP before, during, and after surgery, especially when IOP has been highly elevated for an extended period.

Vitrectomy for Proliferative Diabetic Retinopathy in those under 40 Years of Age

PURPOSE: We compared the surgical outcomes of vitrectomy for proliferative diabetic retinopathy between younger and older groups. METHODS: We reviewed the data of 185 patients (227 eyes) who had undergone vitrectomy and endolaser photocoagulation and who were followed up for at least 6 months. We divided them into two age-based groups: less than 40 years of age (52 eyes), and more than 40 years of age (175 eyes). We compared preoperative status, surgical outcomes, and postoperative complications. RESULTS: Postoperative visual acuity improved in 75.0% in the younger group, and 68.6% in the older group, and the difference was not statistically significant. The proportion of eyes with good visual acuity of 0.6 or better was statistically significantly (Ed-confirm this addition) higher in the younger group (30.8%) than in the older group (17.1%). The proportion of eyes with postoperative visual acuity of no light perception was statistically significantly higher in the younger group. The visual acuity in the patients who lacked photocoagulation was poorer in the younger group. Postoperative recurrent vitreous hemorrhage, corneal epithelial defect, and additional operation rate was more prevalent in the younger group. CONCLUSIONS: We found no significant difference in the overall postoperative results between younger and older patients. Early panretinal photocoagulation and vitrectomy can be helpful to maintain visual function of young patients. Special care is needed to prevent postoperative complications.

Differences in Intraocular Pressure, Corneal Thickness, and Corneal Endothelium Related to Duration in Diabetes

PURPOSE: This study evaluated the differences of intraocular pressure (IOP), corneal thickness, and corneal endothelial morphology compared with age-matched, healthy control subjects, as well as the correlation according to the duration of diabetes. METHODS: Goldmann applanation tonometry, ultrasound pachymetry, and non-contact specular microscopy were performed in 200 patients with diabetes and 100 control subjects. RESULTS: The diabetic subjects had higher IOP, thicker cornea and less cell density, less hexagonality, and more irregular cell size of corneal endothelium than the controls (P<0.05). Central corneal thickness and coefficient of variation in cell size were higher in diabetes of over 10 years duration than in diabetes of under 10 years duration (P<0.05), while endothelial cell density and percentage of hexagonal cells were lower in the diabetes of over 10 years group (P<0.05). Central corneal thickness was correlated with duration of diabetes but IOP and corneal endothelial morphologic characteristics were not. CONCLUSIONS: Especially, those with a diabetes duration of over 10 years have more corneal morphological abnormalities and a higher IOP than normal subjects. Therefore, any surgical procedures should be performed carefully in the diabetic cornea that is easily damaged by, for example, phacoemulsification.

Sutured Posterior Chamber Intraocular Lens in the Vitrectomized Eye: Comparison of PMMA and Acrysof(R) Foldable Lenses

PURPOSE: To compare the clinical outcomes of scleral fixated posterior chamber intraocular lens in vitrectomized eyes according to IOL types. METHODS: Clinical outcomes of 28 eyes of 28 patients who underwent scleral fixated posterior chamber IOL after pars plana vitrectomy and lensectomy were evaluated according to the IOL type used: 19 eyes with PMMA lens (group 1) and 9 with Acrysof(R) foldable lens (group 2) RESULTS: Postoperative BCVA improved or was stabilized in 7 eyes (36.8%) of group 1, and 7 eyes (77.7%) of group 2 (P=0.04). Mean postoperative change in astigmatism was 1.19 +/- 0.79 diopter in group 1 and 0.62 +/- 0.47 diopter in group 2 (P=0.25). Estimated refractive error was -0.76 +/- 0.26 and -0.74 +/- 0.24 diopter in groups 1 and 2, respectively, and postoperative refractive error was -1.31 +/- 1.27 and -1.23 +/- 1.34 diopter, respectively. This showed a slight myopic shift in both groups. There were postoperative complications such as hyphema in 4 eyes (26.3%) in group 1 and in 1 eye (11.1%) in group 2, and transiently increased IOP in 5 eyes (26.3%) and in 1 eye (11.1%), respectively. The other complications that were found in group 1 were glaucoma, retinal detachment, choroidal detachment, and cystoid macular edema. CONCLUSIONS: Scleral fixation using foldable IOL is thought to be a relevant method in vitrectomized eyes, as it showed less postoperative astigmatism change and complications, and better visual outcome.

The Change of Intraocular Pressure after Phacoemulsification in Patients with Open Angle Glaucoma

PURPOSE: We evaluated the change of the intraocular pressure (IOP) after phacoemulsification and IOL implantation in patients with cataract and open angle glaucoma. METHODS: We divided the patients into two groups; group 1 (non trabeculectomy group: IOP was well controlled medically, and had not undergone trabeculectomy) and group 2 (trabeculectomy group: trabeculectomy was performed). Phacoemulsification was performed in both groups, and preoperative and postoperative IOP was compared. RESULTS: IOP decreased after phacoemulsification in both groups. Early transient postoperative IOP elevation was observed in 3 patients of group 1, but postoperative IOP was lower than preoperative IOP throughout the follow up period, and there was no difference between the two groups. The average number of antiglaucomatous agent decreased to 0.29 postoperatively from 1.23 preoperatively and there was no significant difference between two groups. CONCLUSIONS: IOP reduction was observed in open angle glaucoma patients combined with cataract after phacoemulsification, even in the patients who had undergone trabeculectomy previously (group 2). The difference between preoperative and postoperative IOP was larger in group 1, and mean postoperative IOP was lower in group 2.

A Comparative Study for Apoptosis on the Degree of the Amount of Photorefractive Ablation in Photorefractive Keratectomy

PURPOSE: This study was aimed to evaluate changes in the stromal keratocyte after ablation of 50 micrometer and 100 micrometer with use of photorefractive keratectomy(PRK). METHODS: At 4 hours, 24 hours, 72 hours, 7 days and 1 month after PRK, each group of rabbits including normal control group was treated with terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labeling(TUNEL) staining using ApopTag(R) kit in vivo, then apoptotic keratocytes were evaluated with light microscope. RESULTS: There was no response with TUNEL staining of the epithelial cells, stromal keratocyte, and endothelium in normal cornea. In the ablation group, however, regardless of the depth of photorefractive ablation, the TUNEL signal was maximal after 4 hours, and it decreased with time. The signal was more intense in 100 micrometer ablation group than 50 micrometer ablation group, although the signal was not observed at the endothelial cells in both groups. The number of apoptotic stromal keratocytes at each time point of 4 hr, 24 hr, 72 hr, and 1 week was 57+/-8.9, 49+/-7.5, 36+/-5.1, and 12+/-1.3 cells/field in 100 micrometer ablation group, and 31+/-4.4, 28+/-4.6, 21+/-3.9, and 5+/-1.1 cells/field in 50 micrometer ablation group, and the difference between the two groups was statistically significant(P<0.05). CONCLUSION: The more the amount of ablation with photorefractive keratectomy, the stronger the apoptotic response. The postoperative apoptotic response was observed especially within 1 week. These findings suggest that early suppression of postoperative apoptosis within 1 week will influence on the prognosis of visual quality after photorefractive keratectomy, and more studies will be needed in the future.

The Change of Intraocular Pressure after Extracapsular Cataract Extraction in Patients with Angle-closure Glaucoma

We evaluated the effect of cataract extraction on the intraocular pressure(IOP)in patients with cataract and angle closure glaucoma. We divided the patients into two groups, one of which underwent trabeculectomy(group 1), and the other control(group 2). Also, we assessed the effect of peripheral anterior synechiolysis performed during the cataract extraction on IOP. There was a significant difference between the preoperative IOP of two groups, but no difference was noted until 6 months after the operation. However the difference became significant afterwards. IOP reduction was more significant after the synechiolysis in group 2, but no difference was found in group 1. It is thought that the IOP decrease can be achieved by cataract extraction only in chronic angle closure glaucoma. but the effect may not be maintained. Synechiolysis may be helpful to further decrease in IOP after cataract extraction only.