From stem cell niche environments to engineering of corneal epithelium tissue.

Studies on stem cells (SC) show that SC functions are determined by the extracellular microenvironment, known as the "niche", and by intrinsic genetic programs in the SCs; both are involved in regulating the delicate balance of self-renewal and differentiation. We have identified an animal model of limbal SC (LSC) deficiency and transplantation of SC-containing limbal tissue to treat the LSC deficiency, which could not only replace LSCs by providing new healthy corneal epithelial cells but also restore the lost niche of the limbal stromal layer, causing the regression of vessels and rearrangement of the corneal stromal lamellae. The purpose of the ex-vivo expansion technique is to develop a method that will enable culture of a small number of SCs which could than be expanded in a defined cultured system while preserving the original characteristics and properties of the SCs. In addition, SC characteristics will continue to be maintained when the cultured cells are transplanted back into the host. Bromodeoxyuridine-retaining, ΔNp63, ABCG2, p120, and N-cadherin immunoreactive studies of LSC cultured on an amniotic membrane have been performed. Pathological studies have been conducted for cases with preexisting central corneal stromal opacity treated by transplantation of LSCs followed by penetrating keratoplasty. The results indicate that the amniotic membrane can provide the niche environment for cultured LSCs and maintain the limbal-like environment for the transplanted area of cornea.

Changes in corneal basal epithelial phenotypes in an altered basement membrane.

BACKGROUND: To examine the corneal epithelial phenotype in an altered basement membrane. METHODOLOGY/PRINCIPAL FINDINGS: Corneas from 9 patients with symptoms of continuous unstable corneal curvature (CUCC) were harvested by penetrating keratoplasty and subjected to histology examination and immunohistochemical staining with transactivating and N-terminally truncated pP63 transcript (ΔNp63), cytokeratin 3 (Krt3), ATP-binding cassette sub-family G member 2 (ABCG2), connexin 43 (CX43), p38 mitogen-activated protein kinases (p38MAPK), activating protein 2 (TFAP2), and extracellular signal-regulated kinase (Erk1/2) monoclonal antibodies. Positive immunostaining with ABCG2, p38MAPK, and TFAP2 monoclonal antibodies was observed in the basal epithelial cells of CUCC patients, and CX43 and ΔNp63 were detected in the full-thickness epithelial cells of CUCC patients. CONCLUSIONS/SIGNIFICANCE: Our results indicate that alteration of the corneal basement membrane induces a de-differentiation-like phenotype in corneal basal epithelial cells.

Estimation accuracy of surgically induced astigmatism on the cornea when neglecting the posterior corneal surface measurement.

PURPOSE: To evaluate the accuracy of corneal surgically induced astigmatism (SIA) estimation when neglecting the posterior corneal surface measurement. METHODS: Fifty right eyes undergoing phacoemulsification were measured with a rotating Scheimpflug camera (Pentacam; Oculus Inc., Wetzlar, Germany) both before and after surgery. Clear corneal incisions with one suture were used in the phacoemulsification surgery. The keratometric corneal SIA (KSIA) was derived using the anterior corneal surface measurement and the keratometric index (1.3375) while neglecting the posterior corneal surface measurement. The Pentacam-derived total corneal SIA (PSIA) was derived by vergence tracing and polar value analysis [KP(135) and KP(180)] of the measurements on both corneal surfaces. RESULTS: The mean arithmetic estimation errors of the KSIA for the PSIA were 0.16 ± 0.32 (-0.52 to 1.14) D for the KP(135), and -0.02 ± 0.30 (-0.75 to 1.29) D for the KP(180). There was a significant difference between the KP(135) components of the KSIA and PSIA. Bivariate analysis revealed a statistically significant difference between the combined means of the KSIA and PSIA. Overall, 24% had either a KP(135) component of the KSIA that differed by > 0.50 D from that of the PSIA or a KP(180) component of the KSIA that differed by > 0.50 D from that of the PSIA. The blurring strength caused by neglecting the posterior corneal measurement was > 0.50 D in 24% of eyes. CONCLUSION: Neglecting the posterior corneal surface measurement may lead to significant deviation in the corneal SIA estimation after phacoemulsification in a proportion of eyes.

Ex vivo expansion of corneal stem cells on amniotic membrane and their outcome.

OBJECTIVES: To identify the stem-cell property of the ex vivo expansion of limbal stem cells (LSCs) on amniotic membrane (AM) in culture system and after clinical transplantation. METHODS: Four key factors have to be performed in the defined culture system: (1) the label-retaining cells have to be identified; (2) the cells can be serially expanded and passaged in vitro; (3) the expanded cells can be labeled by tissue-specific keratin or markers, and (3) their stem cells cannot be labeled by those keratin or markers. RESULTS: The ex vivo-expanded LSCs on AM were positive for p63 and ABCG2 and BrdU label-retaining studies on flat mount preparation. When the ex vivo-expanded LSCs with AM were transplanted into a subcutaneous layer of nude mice, they formed multiple layers of cells. Only the basal layer of cells was positive for p63 and BrdU. The cells over the suprabasal layers were positive for K12/K3. The pathologic studies of corneal specimen of successful LSC transplantation after penetrating keratoplasty demonstrated that P63-positive cells were noticed all over the basal layer of central cornea and AM could be identified at 10 months after LSC transplantation. CONCLUSIONS: These results indicate that the AM provided the niche function for cultured LSCs and maintained the limbal-like environment for the transplanted area of cornea. The survival of cases depends on the severity of the disease entity, culture technique, and maintenance of the niche environment for LSCs in the culture and after clinical transplantation.

Effects of aging on anterior and posterior corneal astigmatism.

PURPOSE: To evaluate age-related changes in astigmatism of both corneal surfaces and the whole cornea. METHODS: The right eyes of 370 subjects were measured with a rotating Scheimpflug camera (Pentacam). Astigmatisms of the anterior and posterior corneal surfaces were determined. The total corneal astigmatism was derived using power vector summation and vergence tracing. Age-related changes to corneal astigmatism were evaluated using polar value analysis (both in diopter and millimeter). RESULTS: For the anterior and total cornea, the proportion of with-the-rule astigmatisms decreased and those of oblique and against-the-rule astigmatisms increased with age. For the posterior cornea, most eyes displayed against-the-rule astigmatisms in all age groups. There was a significant trend toward against-the-rule astigmatism associated with increasing age for both anterior and total corneal astigmatisms (mean changes of -0.18 and -0.16 diopters/5 years, respectively), and toward with the rule in posterior corneal astigmatism (a mean change of 0.022 diopters/5 years). Regarding shape changes, a "flat meridian toward a more vertical orientation" trend with increasing age for both the anterior and posterior corneal surfaces was observed (mean changes of 0.0295 and 0.0224 mm/5 years, respectively). The posterior corneal surface compensated for the astigmatism arising from the anterior corneal surface in 91.4% and 47.7% of eyes in the 21-30 and > or =71 years groups, respectively. CONCLUSIONS: There were age-related shifts toward against-the-rule and with-the-rule astigmatisms for the anterior and posterior corneal surfaces, respectively. The compensating effects of the posterior corneal surface on anterior corneal astigmatism decreased with advancing age.

Estimation of the effective lens position using a rotating Scheimpflug camera.

PURPOSE: To describe a no-history method of estimating the effective lens position (ELP) for double-K intraocular lens (IOL) power calculation in eyes that had previous refractive surgery. SETTING: Departments of Ophthalmology, Taipei Medical University Hospital and Taipei City Hospital, Taipei, Taiwan. METHODS: The corneal height (H(m)) and anterior chamber diameter (AG(m)) in 106 unoperated eyes were measured using a rotating Scheimpflug camera. The theoretical anterior corneal radius (R(rt)) was then derived from H(m) and AG(m) by regression and rearrangement of the Fyodorov equation. The ELP estimate was then calculated from R(rt). The performance of this ELP estimation method in double-K IOL power calculation and the performance of other methods were compared retrospectively in 11 eyes having cataract surgery that had previous refractive surgery. The refractive results 9 to 12 weeks after cataract surgery were selected for data analysis. RESULTS: The new ELP estimation method, combined with the BESSt formula or the Savini et al. method for estimating post refractive-surgery corneal power (K(post)) in the double-K SRK/T formula, provided the best IOL power prediction results. The mean arithmetic and absolute IOL prediction errors were -0.05+/-0.62 diopters (D) and 0.49+/-0.34 D, respectively, when combined with the BESSt formula and 0.03+/-0.73 D and 0.60+/-0.36 D, respectively, when combined with the Savini et al. method. With either combination, all 11 eyes were within+/-1.00 D of the refractive prediction error. CONCLUSION: This ELP estimation method may be helpful for IOL power calculation in post refractive-surgery eyes when historical data are unavailable.

Intraocular lens power calculation after automated lamellar keratoplasty for high myopia.

PURPOSE: To report intraocular lens (IOL) power calculation in 2 eyes that were highly undercorrected by previous myopic automated lamellar keratoplasty (ALK). METHODS: A 35-year-old man underwent bilateral myopic ALK, which caused high residual myopia (-9.0 -4.0 x 171 and -9.5 -4.5 x 74). The patient then underwent cataract surgery with IOL implantation for cataract development. The double-K clinical history method was utilized, and satisfactory IOL power prediction results were obtained. Two no-history IOL power calculation methods (Rosa correcting factor method and Ferrara theoretical variable refractive index method), which involved axial length-dependent modification of the keratometer-measured corneal radius, and 1 no-history IOL power calculation method (Shammas' method), which involved axial length-independent modification of the keratometer-measured corneal power, were tested on these 2 eyes. RESULTS: In both eyes, the double-K SRK-T clinical history method gave small IOL prediction errors (-0.66 and -0.81 D). The Shammas' no-history method gave a slightly higher IOL prediction error in the right eye (-1.67 D) and a small IOL prediction error in the left eye (-0.74 D). Unacceptable IOL power prediction errors would have resulted if Rosa's correcting factor method (-8.07 and -8.35 D) or Ferrara's theoretical variable refractive index method (-17.56 and -18.51 D) had been applied. When we utilized Rosa's method for the IOL power calculation by assuming that the previous ALK had fully corrected the refractive error, the predicted IOL powers were very close to the benchmark IOL powers (IOL power prediction errors: 1.16 and 0.37 D). When we utilized Ferrara's method with the same assumption, the IOL power prediction errors remained high (-6.32 and -7.16 D). CONCLUSIONS: For patients who have had previous myopic ALK (and whose eyes are highly undercorrected) and who require cataract surgery and for whom the pre-ALK history is available, the double-K method appears to yield excellent predictive results. However, if the pre-ALK history is not available, the Shammas' no-history method appears to yield better results than the Rosa's or the Ferrara's method. High undercorrection by the previous ALK might have been one of the major reasons why Rosa's method resulted in a high IOL prediction error in these 2 eyes. The cause for the marked IOL prediction error by Ferrara's method in this case, however, remains to be determined.

Seasonal variations in the occurrence of retinal vein occlusion: a five-year nationwide population-based study from Taiwan.

PURPOSE: To determine whether seasonal variation exists in the incidence of retinal vein occlusion. DESIGN: Retrospective, nationwide population-based administrative database study. METHODS: We collected data on outpatient and emergency visits for the period from January 1999 through December 2003 from the Taiwan National Health Insurance Research Database, a source that covers more than 96% of Taiwan's 23 million citizens. In total, 20,792 patients with a first-time diagnosis of either central retinal vein occlusion or branch retinal vein occlusion (The International Classification of Disease, Ninth Revision, Clinical Modification [ICD-9-CM] code 362.35 or 362.36, respectively) were identified. Monthly incidence of retinal vein occlusion was obtained for each age group, each gender group, and for the entire sample. The autoregressive integrated moving average method of analysis was adopted to examine seasonality in the monthly incidence of retinal vein occlusion. RESULTS: The monthly incidence rates of retinal vein occlusion revealed significant seasonality, with a clear peak in January for each age group and each gender group, as well as for the total sample. CONCLUSIONS: Our study demonstrates significant seasonal variations in the retinal vein occlusion incidence, with the peak occurrence in the winter month of January.

Validity of the keratometric index: evaluation by the Pentacam rotating Scheimpflug camera.

PURPOSE: To determine the keratometric index based on actual measurements of the anterior and posterior corneal surfaces using a rotating Scheimpflug camera (Pentacam, Oculus) and evaluate the accuracy of this keratometric index in estimating total and posterior corneal powers. SETTING: Departments of Ophthalmology, Taipei Medical University Hospital and Taipei City Hospital, Taipei, Taiwan. METHODS: The right eye of 221 subjects was measured with the Pentacam system. The radius of the best-fit sphere for the anterior corneal surface (rant) and posterior corneal surface (rpost), mean radius of simulated keratometry (rsimK), and central corneal thickness were obtained. The ratio of rant to rpost (AP ratio) and keratometric index were calculated in each eye. RESULTS: The means for rant, rpost, rsimK, and AP ratio were 7.75 mm +/- 0.28 (SD), 6.34 +/- 0.28 mm, 7.75 +/- 0.27 mm, and 1.223 +/- 0.034 mm, respectively. These parameters were normally distributed. The mean calculated keratometric index (Ncal) was 1.3281 +/- 0.0018. Using the keratometric indices of 1.3281 (Ncal), 1.3315 (Gullstrand schematic eye), and 1.3375 (conventional), the mean arithmetic and absolute estimation errors for the total corneal power were, 0.00 +/- 0.24 diopter (D) and 0.17 +/- 0.17 D, 0.43 +/- 0.23 D and 0.45 +/- 0.21 D, and 1.21 +/- 0.24 D and 1.21 +/- 0.24 D, respectively. The total corneal power was predicted to within +/-0.50 D of the actual value in 95.0%, 60.2%, and 0.9% of eyes, respectively. The mean arithmetic and absolute estimation errors for the posterior corneal power using an AP ratio of 1.223 (this study) or 1.132 (Gullstrand schematic eye) were 0.00 +/- 0.17 D and 0.13 +/- 0.12 D and 0.47 +/- 0.18 D and 0.47 +/- 0.17 D, respectively. The posterior corneal power was estimated to within +/-0.50 D of the actual value in 97.7% and 60.2% of eyes, respectively. CONCLUSION: Using the Pentacam-derived keratometric index improved the prediction accuracies of total and posterior corneal powers.

Reduction of indocyanine green-associated photosensitizing toxicity in retinal pigment epithelium by sodium elimination.

OBJECTIVE: To determine if eliminating sodium affects indocyanine green (ICG) photosensitizing toxicity and uptake in cultured human retinal pigment epithelial (RPE) cells. METHODS: Cultured human RPE cells were exposed to ICG (2.5 mg/mL) in balanced salt solution and sodium-free balanced salt solution for 2 minutes. Afterwards, ICG was removed, and the cells were irradiated with a light beam (4 x 10(4) lux) for 40 minutes. Toxicity was monitored using light microscopy, calcein AM-ethidium homodimer 1 staining, trypan blue exclusion test, and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium viability assay. Indocyanine green uptake was measured by optical absorption at 790 nm. RESULTS: Photoreactive changes occurred in RPE cells exposed to ICG and light. These changes included cell shrinkage, cell death, pyknotic nuclei, reduced viability, and reduced mitochondrial dehydrogenase activity. These changes were less severe when ICG was dissolved in sodium-free balanced salt solution. In addition, ICG uptake was reduced when the solvent was sodium-free balanced salt solution. CONCLUSION: Indocyanine green and intense light exposure in RPE cells caused photosensitizing toxicity that was reduced when sodium in the solvent was eliminated and replaced with other cations. CLINICAL RELEVANCE: Eliminating sodium from the solvent reduced ICG uptake into RPE and its associated photosensitizing toxicity. This reconstitution method of ICG may be helpful for safer intravitreal ICG use in macular hole surgery.

Annual database of intraocular lens power in a Taiwanese population.

BACKGROUND: To derive a unique database of intraocular lens (IOL) power for Taiwanese, an ethnic group with a strikingly high prevalence of myopia. METHODS: A retrospective series of 3068 cases visiting Chang Gung Memorial Hospital, Linkou for cataract removal and posterior chamber IOL implantation between July 1999 and June 2000 was reviewed. The distribution of IOL powers and a possible age-correspondence was analyzed by one-way analysis of variance (ANOVA) test and multiple regression. RESULTS: Using the SRK/II linear regression formula, with an "A" constant of 118.5, the mean predicted IOL power required for emmetropia was 20.0 +/- 5.1 diopter (D). The mean IOL power for males was 19.8 +/- 5.1 D. The mean IOL power for females was 20.1 +/- 5.1 D. Moreover, ANOVA results documented a statistically significant tendency of age-dependence for IOL power distribution in the 3 groups (male, female, and male and female; F=24.53, p<0.05; F=16.39, p<0.05; F=40.54; p<0.05, respectively). In particular, it statistically significantly differed among decades over 40 years indicating that IOL power increased with age. However, the implanted IOL power decreased with age in patients younger than 40 years old. Multiple regression analysis showed that age, but not gender, was statistically significantly correlated to the IOL power distribution (p<0.05). CONCLUSION: We provide a unique database of IOL power for cataract surgeries in Taiwan. An age-related correspondence of the database of IOL powers was also documented in this study, which can therefore be regarded further cross-sectional evidence for the age-dependence prevalence of myopia.

GDNF gene therapy attenuates retinal ischemic injuries in rats.

PURPOSE: To examine the protective effects of glial cell line-derived neurotrophic factor (GDNF) on retinal ischemia-reperfusion injury by using gene delivery. METHODS: Gene delivery to retinal cells was achieved through intravitreal injections of recombinant adeno-associated virus expressing GDNF (rAAV-GDNF) in the right eyes and AAV expressing Escherichia coli LacZ (rAAV-LacZ) in the left eyes of Sprague-Dawley rats. Ischemic injury was introduced three weeks after gene delivery. The synthesis and accumulation of GDNF within the retina were determined using immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) three weeks after gene delivery. The neuroprotective effects of GDNF were evaluated by determining the preservation of the inner retina thickness and the cell counts in the retinal ganglion cell (RGC) layer one week after reperfusion. In addition, eletroretinograms (ERGs) were performed to determine the functionality of the retinas. Finally, the levels of RGC apoptosis were measured using the TdT-dUTP terminal nick-end labeling (TUNEL) method 6 h after reperfusion. RESULTS: Gene expression of GDNF was demonstrated through immunohistochemistry and ELISA. Thinning of the inner retina and decreased numbers of cells in RGC layer were noted after ischemia in all of the eyes. However, the thickness of the inner retina and the numbers of cells in RGC layer were better preserved in rAAV-GDNF treated eyes than in rAAV-LacZ treated eyes seven days after reperfusion (p=0.028 and p<0.001, respectively). Also, seven days after reperfusion, the rAAV-GDNF treated eyes had retained larger b-wave amplitudes than rAAV-LacZ treated eyes (p=0.003). Finally, rAAV-GDNF treated eyes had statistically fewer apoptotic cells in the RGC layer than the control eyes (p=0.011). CONCLUSIONS: In these experiments, GDNF moderately protected rat retina from ischemia-reperfusion injury, possibly by preventing apoptosis in retinal cells.

Ultrasound biomicroscopy in pigmented conjunctival cystic nevi.

PURPOSE: To report the use of ultrasound biomicroscopy in the clinical diagnosis and management of pigmented conjunctival cystic nevi. METHOD: Two patients, aged 11 and 18 years, with rapidly growing raised conjunctival melanocytic lesions suspected to be inflamed juvenile conjunctival nevus underwent ultrasound biomicroscopic and histopathologic examinations. RESULTS: Ultrasound biomicroscopic examination of the lesions revealed multiple areas of cystic tissue, which is compatible with pathologic finding of compound nevus with epithelial inclusion cysts formation. Furthermore, clear interface was found between the mass and the underlying sclera. CONCLUSION: Pigmented conjunctival nevi may obscure cysts under slit-lamp examination. Ultrasound biomicroscopy is a useful diagnostic adjunct to distinguish cysts in conjunctival lesions. Additionally, this technique may be helpful in delineating the extent of lesions prior to excision biopsy.

Cytotoxicity of indocyanine green on retinal pigment epithelium: implications for macular hole surgery.

OBJECTIVE: To evaluate the potential cytotoxic effects of indocyanine green (ICG) on cultured human retinal pigment epithelium (RPE) and the resultant implications for macular hole surgery. METHODS: Human RPE cells were exposed to ICG in concentrations from 0.001 to 5 mg/mL. The exposure duration ranged from 5 minutes to 3 hours. Light microscopy, MTS viability assay, and calcein AM-ethidium homodimer 1 staining were used to evaluate the cytotoxic effects of ICG. RESULTS: The RPE cells incubated with up to 5 mg/mL of ICG for 5 minutes or less exhibited no morphologic change and no significant decrease in dehydrogenase activity. When RPE cells were exposed to 5 mg/mL of ICG for 10 minutes, 1 mg/mL of ICG for 20 minutes, or 0.01 mg/mL of ICG for 3 hours, cell morphologic features were altered, mitochondrial dehydrogenase activity decreased, and some cells were necrotic. CONCLUSIONS: Indocyanine green caused cytotoxicity in cultured human RPE in a dose- and time-dependent manner. Cell death occurred by necrosis. CLINICAL RELEVANCE: Exposure of RPE cells to ICG concentrations up to 5 mg/mL for 5 minutes or less was not injurious; prolonged exposure to a low ICG concentration was toxic. Since ICG may be retained in the vitreous cavity for a lengthy period, thorough washout of ICG during macular hole surgery is required.

Expression of tissue inhibitor of metalloproteinase-4 in normal human corneal cells and experimental corneal neovascularization.

PURPOSE: To study the expression of TIMP-4 in cultured corneal cells and in corneal neovascularization. METHODS: Human limbo-corneal epithelial cells, fibroblasts, and endothelial cells were cultured in serum-free, PMA- or basic fibroblast growth factor (bFGF)-treated condition. Neovascularization in rat cornea was induced by suturing. The expression of TIMP-4 was examined by immunohistochemistry, Western blot and RT-PCR. RESULTS: TIMP-4 was constitutively expressed in cultured human corneal cells. The expression was only mildly enhanced after mitogen treatment. TIMP-4 immunoreactivity was predominantly expressed in normal rat corneal epithelium, and also in ingrowing blood vessels following suturing, which persisted up to day 28. Increased staining in corneal epithelium and blood vessels were also noted in vascularized human corneas. CONCLUSIONS: TIMP-4 is expressed in the cornea, which may play a role in modulating extracellular matrix remodeling associated with corneal wound healing and angiogenesis.

Gene therapy for detached retina by adeno-associated virus vector expressing glial cell line-derived neurotrophic factor.

PURPOSE: To examine the protective effect of glial cell line-derived neurotrophic factor (GDNF) on retinal detachment (RD)-induced photoreceptor damage by using gene delivery. METHODS: Gene delivery to photoreceptors was achieved by subretinal injection of recombinant adeno-associated virus expressing GDNF (rAAV-GDNF) in the right eyes and AAV expressing Escherichia coli LacZ (rAAV-LacZ) in the left eyes of Lewis rats. RD in bilateral eyes was induced with subretinal injection of high-density vitreous substitute in the temporal retina 3 weeks after gene delivery. The synthesis and accumulation of GDNF within the retina was monitored 3 weeks after RD by immunohistochemistry and enzyme-linked immunosorbent assay (ELISA), respectively. The rescue of photoreceptors was evaluated by monitoring the preservation of the thickness of photoreceptor outer segment (OS) and outer nuclear layer (ONL). Apoptosis in the photoreceptors was studied using the TdT-dUTP terminal nick-end labeling (TUNEL) method 2 days after RD. Müller cell activity was checked using the immunohistochemistry with glial fibrillary acidic protein (GFAP) antibody 28 days after RD. RESULTS: Gene delivery was demonstrated by immunohistochemical study. The results of ELISA confirmed that high levels of neurotrophic factors were produced in retinas. Photoreceptor OS degeneration and the gradual shortening of the ONL were noted after RD in all the eyes. However, rAAV-GDNF-treated eyes retained longer OS than rAAV-LacZ-treated eyes 7 (P = 0.012) and 28 days (P = 0.008) after RD. ONL was also longer in rAAV-GDNF-treated eyes than in rAAV-LacZ-treated eyes 7 (P = 0.012) and 28 days (P = 0.008) after RD. GDNF-treated eyes had statistically less apoptotic cells than control eyes in photoreceptor layer (P = 0.043). Subretinal proliferation of Müller cells was suppressed in the GDNF-treated group, indicating less scar formation. CONCLUSIONS: GDNF is a potential factor that can protect photoreceptors from degeneration. In addition to preserving the OS and ONL structures, GDNF may exert its protective action by preventing the apoptosis of photoreceptors after RD. GDNF gene therapy may be a valuable adjuvant to current treatments in certain complicated forms of RD.

Amniotic membrane transplantation for pseudomonal keratitis with impending perforation.

BACKGROUND: To determine whether amniotic membrane transplantation (AMT) can be used as adjunctive therapy to promote wound healing and prevent perforation in bacterial keratitis caused by Pseudomonas aeruginosa. METHODS: We report on 6 eyes from 6 patients with bacterial keratitis caused by Pseudomonas aeruginosa associated with prominent stromal melting and extensive stromal loss. AMT was performed after treatment with fortified antibiotics for at least 1 week. The mean follow-up period was 12.8+/-2.5 months. RESULTS: The lesion became sterile in all but 1 case for which AMT was performed. Rapid reepithelialization and decreased inflammation was observed in 5 cases, with complete reepithelialization occurred at 9.4+/-2.1 days postoperatively. The amniotic membrane dissolved in the remaining case with active, extensive corneal infection and persistent epithelial defect; this case finally received evisceration due to intractable glaucoma. In all other cases, after AMT treatment, lesions did not extend, stromal loss was limited, and considerable stromal thickness was preserved. CONCLUSION: AMT may be considered an alternative method for treating pseudomonal keratitis, especially when stromal melting and loss are extensive, and the infection has been controlled.

Acanthamoeba keratitis presenting as dendritic keratitis in a soft contact lens wearer.

Acanthamoeba keratitis is a rare cause of corneal infection in Taiwan, which can result in devastating visual outcomes. A 37-year-old woman, who wore soft contact lenses, suffered from severe pain in her left eye. Biomicroscopy revealed dendritic keratitis, radial keratoneuritis, and fine keratic precipitates on her cornea. Culture, using non-nutrient agar plate seeded with Escherichia coli, resulted in heavy growth of Acanthamoeba. The inpatient treatment, including topical neomycin-polymyxin B and metronidazole (0.5%) eyedrops, oral ketoconazole, and then oral prednisolone, successfully controlled the corneal infection. The best-corrected visual acuity was 0.9 without any evidence of recurrence of infection after 21 months of follow up. Acanthamoeba keratitis can present as dendritic keratitis, which mimics herpes simplex infection, thus, delays appropriate treatment. Early diagnosis and judicious treatment are essential for restoring the vision and avoiding the subsequent need of penetrating keratoplasty.

High-density vitreous substitute in the management of advanced Coats' disease.

Advanced Coats' disease is a threat to vision. Management of advanced Coats' disease has long been a challenge to ophthalmologists. Some people have attempted to use pars plana vitrectomy and intraocular diathermy on diseased vessels followed by intraocular gas or silicone oil injection. However, internal drainage is technically difficult. We present a case of advanced Coats' disease for which, after an encircling buckle and pars plana vitrectomy, intravitreal injection of perfluorodecaline was used to displace the subretinal fluid to the peripheral subretinal space, and transscleral external drainage was achieved. Finally panretinal laser photocoagulation, cryotherapy and endodiathermy were performed on diseased vessels. Visual improvement and reattachment of the posterior pole were achieved. So we think a high-density vitreous substitute can be a useful adjunct in the management of advanced Coats' disease. It minimizes the disadvantages of the internal or external approaches, while maintaining most of the advantages of both.