Retinal ganglion cells toxicity caused by photosensitising effects of intravitreal indocyanine green with illumination in rat eyes.

AIM: To investigate the effects of indocyanine green (ICG) with or without illumination on rat retinal ganglion cells (RGC) and retinal morphology. METHODS: Intravitreal injections of 1.0 mg/ml ICG solution were performed in rat eyes with or without subsequent illumination for 5 minutes. Eyes in the control group had intravitreal injections of balanced salt solution with illumination. Retrograde labelling of RGC with 6% Fluoro-Gold was performed 1 month later and RGC densities were compared between the three groups. Light microscopy with measurements of outer nuclear layer (ONL) and inner nuclear layer (INL) thicknesses were also performed and compared. RESULTS: Eyes with ICG without illumination showed insignificant reduction in RGC density compared with the control group (p = 0.28), whereas a significant decrease in RGC density was found in eyes that had ICG injection with illumination (p = 0.036). A significant increase in ONL thickness was also observed in the ICG with illumination treated eyes compared with the ICG without illumination and the control groups (p<0.001). No significant difference in INL thickness was observed between the three groups. CONCLUSIONS: Intravitreal injection of 0.1 mg/ml ICG in rat eyes followed by illumination resulted in photosensitising toxicity to RGC. Lower ICG concentration or illumination level should be considered when performing ICG assisted macular surgery.

Ocular toxicity of hydroxychloroquine.

OBJECTIVES: To review the types, incidence, pathogenesis, risk factors, and clinical characteristics of hydroxychloroquine ocular toxicity and current views about its screening and management. DATA SOURCES: Literature search of Medline up to May 2005. STUDY SELECTION: Key words for the literature search were 'hydroxychloroquine', 'chloroquine', 'ocular', 'toxicity', 'retinopathy', and 'screening'. DATA EXTRACTION: Original articles and review papers were examined. DATA SYNTHESIS: Hydroxychloroquine ocular toxicity includes keratopathy, ciliary body involvement, lens opacities, and retinopathy. Retinopathy is the major concern: others are more common but benign. The incidence of true hydroxychloroquine retinopathy is exceedingly low; less than 50 cases have been reported. Although its pathogenesis is unclear, risk factors include: daily dosage of hydroxychloroquine, cumulative dosage, duration of treatment, coexisting renal or liver disease, patient age, and concomitant retinal disease. Patients usually complain of difficulty in reading, decreased vision, missing central vision, glare, blurred vision, light flashes, and metamorphopsia. They can also be asymptomatic. Most patients have a bull's eye fundoscopic appearance. All patients have field defects including paracentral, pericentral, central, and peripheral field loss. Colour vision is usually undisturbed in early retinopathy, but is impaired in the advanced stage. Most patients have visual loss. Some patients with advanced retinopathy may experience deteriorating visual acuity even after cessation of treatment. There is no consensus on the definition of retinopathy, most-effective ophthalmological assessment, or frequency of screening. Regular screening may be necessary to detect reversible premaculopathy. Cessation of the drug is the only effective management of the toxicity. CONCLUSION: Consensus with regard to various important aspects of hydroxychloroquine ocular toxicity is limited, especially the definition of true hydroxychloroquine retinopathy, the most effective ophthalmological assessment, and frequency of screening. Decisions to stop medication must be made in conjunction with the rheumatologist or physician managing the patient. Management of hydroxychloroquine retinopathy remains a clinical challenge.

Ocular toxicity of ethambutol.

OBJECTIVE: To review the literature on ocular toxicity of ethambutol--its background, clinical presentation, toxicity characteristics, management, monitoring, and preventive measures. DATA SOURCES: Literature search of Medline from 1962 to May 2005. STUDY SELECTION: All related literature in English using the search formula: (ethambutol OR myambutol) AND (eye* OR ophthal* OR ocular) AND (adverse OR toxic). DATA EXTRACTION: All information was collected and analysed by authors. DATA SYNTHESIS: Ethambutol hydrochloride is a commonly used first-line anti-tuberculous agent. Although rare, ocular toxicity in the form of optic neuritis (most commonly retrobulbar neuritis) has been well documented since its first use in the 1960s. Classically described as dose- and duration-related and reversible on therapy discontinuation, reversibility of optic neuritis remains controversial. International guidelines on prevention and early detection of ethambutol-induced ocular toxicity have been published. Nonetheless, opinion of the clinical effectiveness of regular vision tests to enable early detection of toxicity is divided. CONCLUSIONS: The course of ethambutol-induced ocular toxicity is unpredictable. Measures to ensure a high level of awareness in medical staff and patients of this potential adverse effect appear to be the best current preventive method. Classified by the World Health Organization as a place with an intermediate tuberculosis burden and good health infrastructure, Hong Kong is in a good position to examine the unanswered questions about ethambutol-induced ocular toxicity.

Virological response to peramivir treatment in adults hospitalised for influenza-associated lower respiratory tract infections.

An open-label trial on intravenous peramivir was conducted among adult patients hospitalised for influenza-associated lower respiratory tract complications (LRTCs). Virus culture and quantitative reverse transcription PCR (qRT-PCR) were performed serially until Day 10. Peramivir treatment was associated with viral RNA decline as well as culture and RNA negativity, which occurred at rates comparable with those of oseltamivir: by Day 5, viral load decline -2.5 log10 copies/mL [ßinteraction -0.071, standard error (SE) 0.121, 95% confidence interval (CI) -0.309 to 0.167]; culture-negative, 94% (vs. 95%); and RNA-negative, 44% (vs. 36%). Extended treatment of >5 days was required in 69% of cases because of slow clinical resolution and viral clearance in LRTCs. Peramivir was well tolerated. These data are useful for future trial design in this unique population.

Vitrectomy and gas tamponade without internal limiting membrane peeling for myopic foveoschisis.

AIM: To evaluate the clinical and anatomical outcomes of pars plana vitrectomy and gas tamponade without internal limiting membrane (ILM) peeling in symptomatic patients caused by myopic foveoschisis. METHODS: Nine eyes in eight highly myopic patients who had myopic foveoschisis with foveal detachment underwent vitrectomy without ILM peeling followed by gas tamponade. Main outcome measures include change in best corrected visual acuity (BCVA) and changes in height of the foveal detachment and resolution of the myopic foveoschisis measured by optical coherence tomography (OCT). RESULTS: After surgery, BCVA improved in eight eyes with the median BCVA improved from 20/80 to 20/50 (p=0.012). The mean line of visual improvement was 3.6 lines. OCT showed complete resolution of myopic foveoschisis with complete foveal reattachment in seven (77.8%) eyes with partial resolution in two (22.2%) eyes. The mean height of foveal detachment decreased from 505 mum preoperatively to 21 mum postoperatively (p<0.001). CONCLUSIONS: Vitrectomy without ILM peeling followed by gas tamponade appeared to result in favourable visual and anatomical outcomes for treating myopic foveoschisis in highly myopic eyes. The results are comparable with studies in which ILM removal was performed. Further controlled study will be useful to determine the role of ILM peeling in these patients.

The effects of indocyanine green and endoillumination on rabbit retina: an electroretinographic and histological study.

AIM: To evaluate the functional and morphological retinal toxicity associated with intravitreal injection of indocyanine green (ICG) dye in rabbit eyes during vitrectomy with endoillumination. METHODS: 20 eyes of 10 New Zealand pigmented rabbits were used in the study. All eyes underwent pars plana vitrectomy and removal of posterior vitreous cortex under endoillumination. In one eye of each rabbit, intravitreal injection of 0.1 ml of 2.5 mg/ml ICG was applied for 30 seconds followed by 10 minutes of endoillumination. The control eye had endoillumination only without ICG injection. Dark adapted and light adapted electroretinograms (ERGs) were performed before the surgery and 1 week after surgery for serial comparisons. Rabbits were killed 1 week after surgery and eyes were enucleated for histological examination. RESULTS: Serial ERG comparisons showed significant reduction in the light adapted a-wave amplitude (p = 0.037) and significant delays in the dark adapted and light adapted b-wave latencies (p = 0.020 and p = 0.038, respectively) in the ICG treated eyes. Histological examinations demonstrated loss of photoreceptor outer segments with focal absence of photoreceptors in some areas in the ICG injected eyes. CONCLUSIONS: Vitrectomy followed by intravitreal injection of 2.5 mg/ml ICG for 30 seconds with endoillumination may result in retinal toxicity causing functional and morphological retinal damages in rabbit eyes. The lowest concentration of ICG should be used if necessary for intraocular use to prevent potential retinal toxicity.

Treatment of epiretinal membrane: an update.

Epiretinal membrane is a common surgical disease of the elderly. The aetiology, clinical presentation, and diagnosis are briefly described. Management, principally vitrectomy and membrane removal, is then elaborated. Recent advances such as internal limiting membrane peeling are further discussed. The safety and efficacy of intra-ocular dyes, including indocyanine green and trypan blue, as well as the new technique of 'double staining', are evaluated.

Idiopathic macular hole surgery in Chinese patients: a randomised study to compare indocyanine green-assisted internal limiting membrane peeling with no internal limiting membrane peeling.

OBJECTIVE: To compare the anatomical and visual outcomes of primary idiopathic macular hole surgery using indocyanine green-assisted internal limiting membrane peeling versus no internal limiting membrane peeling. DESIGN: Prospective randomised controlled clinical trial. SETTING: University teaching hospital, Hong Kong. PATIENTS: Fifty-one eyes of 49 Chinese patients with primary idiopathic macular hole were studied. INTERVENTIONS: Patients were randomised to undergo pars plana vitrectomy with indocyanine green-assisted internal limiting membrane peeling (26 eyes) or surgery without internal limiting membrane peeling (25 eyes). Perfluorocarbon gas was used in all cases as internal tamponade. MAIN OUTCOME MEASURES: Primary macular hole closure rate and best-corrected visual acuity. RESULTS: The mean follow-up duration was 12 months (range, 6-23 months). Respectively to the indocyanine green-assisted internal limiting membrane peeling group and non-internal limiting membrane peeling group, the primary anatomical closure rate was 92.3% and 32.0% (P<0.001), whereas improvement in best-corrected visual acuity was 3.7 and 1.5 lines (P=0.002). More eyes in the first group (84.6%) had improvement of 2 or more lines of best-corrected visual acuity after surgery than in the second group (32.0%) [P<0.001]. Multivariate logistic regression showed indocyanine green-assisted internal limiting membrane peeling was the only significant predictor for primary closure of the macular hole (adjusted odds ratio=30.8). CONCLUSION: Indocyanine green-assisted internal limiting membrane peeling in idiopathic macular hole surgery results in significantly better anatomical and visual outcomes compared with non-internal limiting membrane peeling in Chinese patients.

RP1 in Chinese: Eight novel variants and evidence that truncation of the extreme C-terminal does not cause retinitis pigmentosa.

Heterozygous truncating mutations in the RP1 gene cause approximately 7% of autosomal dominant retinitis pigmentosa (RP) cases. To examine the role of RP1 mutations in RP, we screened 101 unrelated Chinese RP patients (unselected for mode of inheritance) and 190 elderly normal control subjects for sequence changes in the coding exons for the 2156 amino acid RP1 protein. One patient had a mutation, thus RP1 mutations cause about 0.0% to 5.4% (95% confidence interval) of all RP among Chinese. The mutation was R677X, the most common found in Americans. Five other known sequence changes were found. In addition, nine novel sequence alterations were identified: 746G>A (R249H), 1437G>T (M479I), 2116G>C (G706R), 3024G>A (Q1008Q), 3188G>A (Q1063R), 5797C>T (R1933X), 6423A>G (I2141M), and the variants 6542C>T and 6676T>A, both in the 3' untranslated region. One control subject and three members of a non-RP family were heterozygous for R1933X, which is therefore likely to be a non-disease-causing variant. The most C-terminal truncation previously reported was due to Tyr1053 (1-bp del) and occurred in RP patients. Thus the presence of a normal level of at least part of RP1 between amino acids 1052 and 1933 appears necessary to prevent RP. Hum Mutat 17:436, 2001.

Immunological and electrophysiological investigations of severe ptosis after bone marrow transplantation.

Ocular problems are common in recipients of stem cell transplantation (SCT), but ptosis is rarely reported and investigated. Among 346 consecutive SCT recipients, severe bilateral ptosis was noticed or reported in six cases (five women and one man), all with acute graft-versus-host disease (aGVHD) and chronic graft-versus-host disease (cGVHD). On univariate analysis, both aGVHD (P=0.001) and cGVHD (P<0.001) were associated with post SCT ptosis, while a trend was shown for female sex (P=0.086). The median level of anti-acetylcholine receptor antibody was significantly higher in ptosis cases than controls with cGVHD (student's t-test, P=0.01). Antistriated muscle antibody was detected in three cases and was not significantly different from controls (Fisher's exact test, P=0.29). Tensilon tests were uniformly negative. However in five cases, single fibre electromyogram at frontalis muscle showed irregular recruitment effort, suggesting localized neuromuscular transmission defect reminiscent of ocular myasthenia gravis (MG). Two patients were observed, while three patients did not respond to mestinon or steroids treatment and one patient underwent aponeurosis advancement surgery. Transplant physicians and ophthalmologists should be aware of the problem of post SCT ptosis, which may be related to alloimmune causes of neuromuscular transmission block. Diagnosis can be difficult to confirm even with invasive SF-EMG testing. Most cases warrant conservative treatment due to chronicity, benign course and poor response to medication.

Fibrous dysplasia masquerading as extramedullary relapse after bone marrow transplantation for chronic myeloid leukemia.

A 19-year old girl suffered from relapse of chronic myeloid leukemia (CML) after bone marrow transplantation. The disease was controlled by interferon and imatinib mesylate, but was complicated by autoimmune hyperthyroidism. She presented with unilateral proptosis with no extraocular muscle or visual defect at 26 months follow-up. Systemic investigations showed no recurrence of leukemia or thyrotoxicosis. Magnetic resonance imaging revealed an extensive retro-orbital base of skull lesion. A trans-oral biopsy showed fibrous dysplasia and continuous observation was advised. The unusual sequence of events and the differential diagnoses for unilateral proptosis in post bone marrow transplantation (BMT) cases are discussed.

Surgical technique for transcleral-fixation of a dislocated posterior chamber intraocular lens.

PURPOSE: To report a cornea-pars plana through-and-through technique for the repositioning and transcleral suture fixation of a dislocated posterior chamber intraocular lens. DESIGN: Interventional case series. METHODS: For transscleral suture fixation of a dislocated posterior chamber intraocular lens, one needle of a double-arm 10-0 Prolene needle is passed through the paracentesis site then underneath the intraocular lens haptic, and through the intended scleral outlet on the opposite side. The other needle of the Prolene suture is also passed through the same paracentesis, above the same haptic, and through the intended scleral outlet on the opposite side. The haptic is now well supported, and the knot is tied. A similar procedure is performed for the second haptic if necessary. RESULTS: Three eyes (three patients) were operated on using this technique with good visual and anatomic outcome. CONCLUSION: The described technique is simple, safe, allows early visual rehabilitation, and can be accomplished without an assistant.

Modified sutureless sclerotomies in pars plana vitrectomy.

PURPOSE: To study the effectiveness and safety of a modified sutureless sclerotomy technique in pars plana vitrectomy. METHODS: We rotated the scleral tunnels of the original sutureless sclerotomy technique through 90 degrees, thus rendering them parallel to the corneoscleral limbus. This modified technique was applied to 25 consecutive eyes (25 patients) that had pars plana vitrectomy during a 2-month period. RESULTS: Twenty (80%) of 25 eyes (25 patients) did not require suturing of the sclerotomy sites associated with pars plana vitrectomy. Eight (11%) of 75 sclerotomy sites required suturing to ensure watertight closure. No clinically significant complications were encountered. CONCLUSION: The modified sutureless sclerotomy technique was found to be safe, more convenient, and easier to perform, especially in eyes with small interpalpebral space.

Ultrasound biomicroscopy of conventional and sutureless pars plana sclerotomies: a comparative and longitudinal study.

PURPOSE: To report the rate of ultrasonically visible vitreous incarceration and longitudinal changes of incarcerated vitreous in pars plana sclerotomies after conventional suturing or sutureless technique using ultrasound biomicroscopy. METHODS: Twenty-five consecutive eyes (25 patients) undergoing primary three-port pars plana vitrectomy participated. The first 16 pars plana vitrectomies were performed with standard conventional sutured sclerotomies, and the following nine pars plana vitrectomies were performed with modified sutureless sclerotomies. Patient demographics, diagnoses, procedures, and complications were recorded. Each patient had ultrasound biomicroscopy performed 1 week before surgery, and also after surgery at 1 week, 2 weeks, 3 weeks, 4 weeks, 2 months, 3 months, and 6 months. Visible vitreous incarceration was graded as 0 to 3. RESULTS: Vitreous incarceration was seen in 41 of 48 sclerotomies (85.4%) in the conventionally sutured group, and in 23 of 27 sclerotomies (85.2%) in the sutureless group, with no significant difference in severity among sclerotomies within each group and between the two groups. There was a significant difference in the rate of vitreous incarceration between diabetic patients with proliferative retinopathy and others (P =.002). No progressive change of visible vitreous incarceration was noted in any eye during the 6-month postoperative period. No sclerotomy-related complications occurred during the study period. CONCLUSIONS: Ultrasound biomicroscopy showed no difference in the amount of visible vitreous incarceration in conventionally sutured or sutureless sclerotomies. There was no visible longitudinal change in the incarcerated vitreous during the 6 months of follow-up in uncomplicated cases.

Indocyanine green staining and removal of internal limiting membrane in macular hole surgery: histology and outcome.

PURPOSE: To report the surgical technique, outcome, and histologic findings involving indocyanine green staining and removal of internal limiting membrane in primary macular hole surgery. METHODS: Prospectively, consecutive patients with idiopathic macular hole or myopic macular hole with retinal detachment were recruited. After pars plana vitrectomy and epiretinal membrane removal, the internal limiting membrane was stained and removed. The specimens were stained using hematoxylin and eosin and periodic acid-Schiff. Immunohistochemical staining was also performed for glial fibrillary acidic protein, vimentin, type I and type IV collagen, and actin. RESULTS: Among 10 patients (10 eyes) in the study, nine eyes had stage 3 or 4 macular hole. Four of them had chronic macular hole. The tenth patient had retinal detachment resulting from a myopic macular hole. Postoperatively, all cases had closure of macular hole without an elevated edge and the retina was attached. Seven patients had improvement of 2 or more Snellen lines, whereas visual acuity remained the same for the other three patients. In six eyes in which complete histologic examinations were feasible, internal limiting membrane was confirmed and two eyes also had a small amount of epiretinal membrane. Myofibrocytes in internal limiting membrane, either scattered or as a single layer, were found in three cases. CONCLUSIONS: Removal of indocyanine green--stained internal limiting membrane around idiopathic macular hole or myopic macular hole with retinal detachment is confirmed with histology and may contribute to macular hole closure and retinal reattachment.

Molecular diagnostics for retinitis pigmentosa.

BACKGROUND: At least 1 million people worldwide have retinitis pigmentosa (RP), making it relatively common among the inherited forms of blindness. Mutations in many genes may cause RP. The most common known mutation, Pro347Leu in rhodopsin, is found in no more than about 1% of unrelated patients, implying the impracticality of a diagnostic test which would screen only for a few, common mutation sites. CONCLUSIONS: Ongoing discovery and study of RP genes makes it feasible to consider a molecular diagnostic test which would screen coding regions of all known RP genes by a mutation detection method such as conformation-sensitive gel electrophoresis followed by sequencing. The parallel development of RP genetic knowledge and treatments such as gene therapy will make such tests both possible and necessary.

Internal limiting membrane removal in macular hole surgery for severely myopic eyes: a case-control study.

AIMS: To determine the surgical outcome of indocyanine green (ICG) assisted retinal internal limiting membrane (ILM) peeling in macular hole surgery for severely myopic eyes and compare the visual and anatomical outcomes with an emmetropic control group. METHODS: 10 severely myopic eyes (-6.0 D or greater) of 10 patients with macular holes without retinal detachment were recruited prospectively. All eyes received ICG assisted ILM removal of 3-4 disc diameters around the macular holes. Cases were matched with a prospective control group of 10 emmetropic macular hole patients who underwent identical ICG assisted ILM peeling surgery in the same period. RESULTS: The mean refractive error in the myopic and control group was -11.8 D and +0.3 D, respectively (two tailed t test, p < 0.001). The mean follow up duration for the myopic and control group was 12.1 and 13.3 months, respectively (two tailed t test, p = 0.63). The primary anatomical closure rate in both groups was 90% (Fisher's exact test, p = 1.0). For both the myopic and control groups, there were significant improvement in the mean log MAR visual acuity after the surgery with improvements from 0.86 to 0.57 for the myopic group (two tailed t test, p = 0.015) and 0.89 to 0.44 for the control group (two tailed t test, p = 0.002). The mean preoperative and postoperative visual acuity, rates of final visual acuity of 20/50 or better, and improvement of two or more lines were not statistically different between the two groups. CONCLUSION: ICG assisted ILM peeling in macular hole surgery for severely myopic eyes without retinal detachment gives promising anatomical and visual outcomes, which are comparable to that of non-severely myopic eyes.

Indocyanine green assisted retinal internal limiting membrane removal in stage 3 or 4 macular hole surgery.

AIMS: To determine surgical outcome in primary idiopathic stage 3 or 4 macular holes with indocyanine green (ICG) assisted retinal internal limiting membrane (ILM) peeling. METHODS: A prospective, consecutive, interventional case series with 41 eyes of 40 patients was included. No patient defaulted follow up. Besides a standard macular hole surgery, all eyes received ICG assisted ILM removal of 3-4 disc diameters around macular holes. At the end of the surgery, 12% perfluoropropane gas was used. A face down posture for 2 weeks was required postoperatively. RESULTS: The mean follow up period was 15.1 months (range 6-24 months). Twenty (48.8%) eyes had stage 3 macular holes and 21 (51.2%) had stage 4 macular holes. The overall median duration of holes was 11 months. 19 (46.3%) were chronic macular holes of more than 12 months' duration. The anatomical success rates after one surgery was 87.8% (36 eyes), while that of chronic and non-chronic ones was 78.9% and 95.5%, respectively. The median preoperative and postoperative visual acuity was 20/200 (range 20/60 to counting fingers) and 20/100 (range 20/20 to 20/400), respectively. 24 (58.5%) eyes had improvement of two or more Snellen lines. The mean was 3.2 lines (range two to nine lines), with 3.6 lines and 2.7 lines for non-chronic and chronic holes, respectively. For all the 41 eyes, 16 (39%) eyes had a final visual acuity of 20/50 or better. CONCLUSION: ICG assisted retinal ILM removal, in idiopathic primary chronic and non-chronic stage 3 or 4 macular hole surgery, appears to give a promising anatomical closure rate without compromising the visual result.

Comparison of outcomes of primary and secondary implantation of scleral fixated posterior chamber intraocular lens.

AIM: To assess and compare the results of primary and secondary implantation of scleral fixated posterior chamber intraocular lens (SFIOL). METHODS: The medical records of a consecutive series of 55 eyes of 55 patients with SFIOLs implanted during (group 1) or after (group 2) complicated senile cataract surgery were retrospectively reviewed and analysed. RESULTS: There were 30 and 25 eyes in group 1 and 2, respectively. Follow up was from 6 to 36 months. Mean logMAR postoperative best corrected visual acuity in group 1 was not significantly different (0.50 (SD 0.36)) from that of group 2 (0.36 (0.21)) (p=0.109). Postoperative best corrected visual acuity of 6/12 or better was achieved in 58.6% and 76.0% in group 1 and 2, respectively. The difference was not statistically significant (p=0.177). In group 1, 25 (83.3%) eyes had a total of 55 early complications, while in group 2, 16 (64%) eyes had 26 early complications (p=0.028). The difference in early complication was statistically significant. For late complication after 1 month, 21 (70.0%) eyes had a total of 37 complications in group 1, while 13 eyes (52.0%) had 19 complications in group 2 (p=0.077). The difference in late complication was not statistically significant. CONCLUSION: Secondary implantation of SFIOL after cataract extraction seems to have a lower early complication rate than primary implantation in complicated cataract extraction although the final visual acuity and late complication rate are not significantly different.

Effects of trypan blue on cell viability and gene expression in human retinal pigment epithelial cells.

AIM: To evaluate the effects of trypan blue on cell viability and gene expression in human retinal pigment epithelial (RPE) cells. METHODS: Three concentrations (0.06 mg/ml, 0.6 mg/ml, and 4 mg/ml) of trypan blue were applied to human ARPE19 cells for 1 minute. Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. RPE cells were sampled daily for 6 consecutive days to assess the effects of trypan blue on cell viability. The effects of trypan blue on the expression of apoptosis related and cell cycle arrest gene expressions including c-fos, c-jun, p53, and p21 were performed using reverse transcription-polymerase chain reaction and immunostaining. RESULTS: The MTT assay showed a concentration dependent suppression effect of trypan blue on cell viability, with higher reduction in the 0.6 mg/ml and 4 mg/ml trypan blue treated groups. No significant change in the expression of c-fos and c-jun was found with all three concentrations of trypan blue. An increase in p53 expression was found in the 4 mg/ml trypan blue treated group at 10-30 minutes after trypan blue application. Immunostaining showed a mild, albeit insignificant, increase of p53 expression in the RPE cells. No significant increase in p21 expression was observed in the 0.06 mg/ml trypan blue treated group but there were significant increases in p21 expression in both the 0.6 mg/ml (p = 0.032) and the 4 mg/ml (p = 0.025) treated groups. CONCLUSIONS: Trypan blue may lead to toxicity on cultured RPE cells as indicated by the reduction in cell viability and changes in the expression of apoptosis related and cell cycle arrest genes at higher concentrations. The application of 0.06 mg/ml trypan blue for 1 minute appeared to have no significant effect on cultured RPE.