Direct Determination of High-Affinity Binding Constants by Continuous Injection Isothermal Titration Calorimetry.

Isothermal titration calorimetry (ITC) is a method to determine thermodynamic values (ΔG, ΔH, and ΔS) for ligand-receptor binding in biological and abiological systems. It is challenging to directly determine subnanomolar dissociation constants using a standard incremental injection approach ITC (IIA-ITC) measurement. We recently demonstrated a continuous injection approach ITC (CIA-ITC) [ J. Phys. Chem. B 2021, 125, 8075-8087]enables the estimation of thermodynamic parameters in situ. In this work, we demonstrate a label-free and surface modification-free CIA-ITC to determine the complete binding thermodynamics of a ligand with a subnanomolar dissociation constant KD. The KD for desthiobiotin (DTB)-avidin binding was determined to be 6.5 pM with respect to the ligand by CIA-ITC, a quantity unsuccessfully measured with IIA-ITC and surface plasmon resonance spectroscopy (SPR). This value compares well with literature-reported spectroscopic determination of DTB-avidin binding. Criteria with respect to the concentration of the ligand and receptor and flow rate for obtaining true equilibrium dissociation constants without displacement titration are presented.

Continuous Injection Isothermal Titration Calorimetry for In Situ Evaluation of Thermodynamic Binding Properties of Ligand-Receptor Binding Models.

We utilize a continuous injection approach (CIA) rather than the traditional incremental injection approach (IIA) to deliver ligand (or receptor) to the calorimeter cell to evaluate thermodynamic binding parameters for three common ligand-receptor binding models-single independent, competitive, and two independent binding sites-using isothermal titration calorimetry (ITC). A general mathematical expression for the binding isotherm for any binding stoichiometry under continuous delivery of ligand (or receptor) resulting in an analytical solution for the thermodynamic binding parameters is presented. The advantages of CIA include reduction in experimental time, estimation of thermodynamic binding parameter values, and automation of the experiment since thermodynamic parameters are estimated in situ. We demonstrate the inherent advantages of CIA over IIA for the three binding models. For the single independent site model, we utilized the binding of Ba2+ ions to ethylenediaminetetraacetic acid (EDTA), while competitive binding was captured by titration of Ca2+ ions into a buffered solution of Ba2+ and EDTA. We experimentally simulated a two independent binding site system by injecting Ca2+ into a solution of EDTA and 1,3-diaminopropane-N,N,N',N'-tetraacetic acid (DPTA). The results demonstrate estimation of thermodynamic parameters with greater confidence and simultaneous reduction in the experimental time of 83% and titrating reagent of 50%, as compared to IIA.

Mechanism for Transition of Reverse Cylindrical Micelles to Spherical Micelles Induced by Diverse Alcohols.

Herein, the effects of various alcohols on lecithin/CaCl2 organogels are investigated. Mixtures of lecithin and CaCl2 form reverse cylindrical micelles, resulting in optically transparent organogels. The addition of various alcohols to a mixture of lecithin and CaCl2 induces a decrease in viscosity through which reverse cylindrical micelles are transformed into spherical micelles (or short cylindrical micelles). Long-hydrocarbon-chain alcohols decrease the viscosity of lecithin/CaCl2 mixtures more efficiently. Hydrogen bonding and hydrocarbon chain interactions between lecithin and alcohol play important roles in the morphological transition. More importantly, isothermal titration calorimetry was conducted to obtain thermodynamic variables such as the enthalpy, equilibrium constant, Gibbs free energy, entropy, and stoichiometry of the associated molecules observed in the transition. It was found that the transition is an entropically driven process, in which the endothermic and exothermic behaviors were observed depending on the hydrocarbon chain length in the alcohol. In addition, the enthalpy for the association of the alcohol with lecithin showed a linear relationship depending on the hydrocarbon chain length, in which the magnitude of hydrogen bonding and hydrocarbon chain interactions was obtained quantitatively. To the best of our knowledge, this is the first study reporting the thermodynamic properties of the morphological transition observed in a reverse self-assembly process.

Risk factor analysis for the development and progression of retinopathy of prematurity.

PURPOSE: To classify the risk factors that contribute to the development versus progression of retinopathy of prematurity (ROP). METHODS: The medical records of premature infants born with a birth weight (BW) less than 1501 g or a gestational age (GA) of 32 weeks or less were retrospectively reviewed. Twenty potential risk factors that may influence the development or progression of ROP were analyzed by univariate and multivariate logistic regression analyses. The progression of ROP was defined as type 1 ROP, threshold ROP, or aggressive posterior ROP for which treatment was recommended. RESULTS: A total of 324 eyes were included; 157 eyes (48.5%) showed ROP development, and 48 eyes exhibited ROP progression (14.8% of all eyes and 30.6% of the ROP-developed eyes). According to the univariate and multivariate logistic regression analyses, prenatal steroid use, GA, the duration of mechanical ventilation, and respiratory distress syndrome were associated with the development of ROP. However, GA, bronchopulmonary dysplasia, the number of red blood cell units transfused, intraventricular hemorrhage, and periventricular leukomalacia were significantly correlated with ROP progression. CONCLUSION: The risk factors that influenced ROP development versus ROP progression were not identical. Evaluating these risk factors during screening of high-risk premature infants will help determine the appropriate timing of examinations and treatment.

Microscale droplets covered by amphiphilic gold nanoparticles with various ligand ratios and concentrations.

We describe a simple and reliable route for forming microscale droplets covered with amphiphilic gold nanoparticles (AuNPs) functionalized with mixed hydrophilic and hydrophobic ligands on the AuNP surface. When an aqueous solution of amphiphilic AuNPs was mixed with hexane, the hexane (or water) droplets covered with amphiphilic AuNPs in the water (or hexane) phase were created, in which amphiphilic AuNPs in water phase migrated to the hexane-water interface. The extent of AuNP migration to the interface could be tuned by the ratio of the hydrophobic to hydrophilic ligands on the AuNP surface and the overall concentration of AuNPs. Importantly, the extent of the AuNP migration to the interface depending on the AuNP concentration followed the Langmuir isotherm model well. The equilibrium constant and maximum uptake of AuNPs at the interface were estimated using the Langmuir isotherm model. To the best of our knowledge, this is the first report of the equilibrium constant determination of amphiphilic AuNPs at the liquid-liquid interface. Based on the maximum uptake of AuNPs at the hexane-water interface, we demonstrated that the AuNPs could be closely packed at the interface.

Anisotropic Growth of Silver Nanoparticles Is Kinetically Controlled by Polyvinylpyrrolidone Binding.

Polyvinylpyrrolidone (PVP) is used in the synthesis of Ag nanoparticles (NPs) with controlled shape, most commonly producing cubes. The mechanism for shape control is unclear but believed by many to be caused by preferential binding of PVP to Ag(100) facets compared to Ag(111) facets and assumed by most to be the result of thermodynamic control, whereby facets with lower interfacial free energy predominate. To investigate this mechanism, we measured adsorption isotherms of PVP on different-shaped Ag NPs, to determine the thermodynamics of PVP adsorption to Ag(100) and Ag(111) facets. The equilibrium adsorption constant is independent of PVP molecular weight and depends only weakly on NP shape (and thus Ag facet). The equilibrium adsorption constant for PVP on Ag(111) (2.8 M-1) is about half that on Ag(100) (5 M-1). From a Wulff construction, this difference is not nearly enough to produce cubes via thermodynamic control. This result indicates the importance of kinetic control of the Ag nanoparticle shape by PVP, as has recently been proposed.

Gravimetric analysis of the autocatalytic growth of copper microparticles in aqueous solution.

The growth kinetics of copper microparticles was analysed by using the gravimetric method. The copper microparticles were synthesized in aqueous solution containing cupric ion and HCHO under various conditions (temperature, additive) and the total mass was monitored during the synthesis. The relation between the total mass and time was formularized using heterogeneous and pseudo-first order reaction kinetics of the autocatalytic surface growth of copper with a modification of the Finke-Watzky kinetic model. Fitting of theoretical curves to the experimental results with various temperatures provided the rate constants of the surface growth, and the reaction activation energy was found from the Arrhenius plot to be 105.4 kJ mol-1. The obtained value was validated by comparing it with one from copper film growth. Its change was observed with the addition of 2,2'-dipyridyl during synthesis.

Long-term clinical outcome of femtosecond laser-assisted lamellar keratectomy with phototherapeutic keratectomy in anterior corneal stromal dystrophy.

PURPOSE: To evaluate long-term outcome of femtosecond laser-assisted lamellar keratectomy (FLK) with phototherapeutic keratectomy (PTK) in patients with anterior corneal stromal dystrophies. METHODS: A total of 10 eyes from seven patients who underwent FLK were included. The patients had suffered from recurrent corneal erosion or visual disturbance in anterior corneal dystrophies (five Avellino dystrophies and two lattice dystrophies). Planar-shaped lamellar keratectomy was performed using femtosecond laser. The amount of corneal excision was determined by the depth of corneal opacity. Additional PTK with mitomycin C application was performed for smoothening of corneal cut surface. The patients were evaluated with following parameters: uncorrected visual acuity, best-corrected visual acuity (BCVA), mean anterior keratometric value, corneal irregularity, corneal high-order aberrations (HOA) and the recurrence of corneal erosion. RESULTS: Mean duration of follow-up was 64 months (2.5-9.5 years). The BCVA improved more than two lines of Snellen chart at last visit. The changes of keratometric values were within ±1 D in eight out of 10 eyes. Corneal irregularities in central 5 mm cornea and the values of total corneal HOA in central 6 mm cornea decreased by 0.3-3.1 D and 0.01-2.2 µm, respectively. Corneal erosion did not recur in any of those patients during follow-up and corneal dystrophy did not recur in eight out of 10 eyes. CONCLUSION: In anterior corneal stromal dystrophies, FLK with PTK can be an effective surgical option to improve VA through decreasing corneal irregularities and HOA, while minimising corneal curvature changes.

Refractive error change and vision improvement in moderate to severe hyperopic amblyopia after spectacle correction: Restarting the emmetropization process?

PURPOSE: The aims of the study were to develop guidelines for prescribing spectacles for patients with moderate to severe hyperopic amblyopia and to demonstrate how emmetropization progresses. METHODS: Children with hyperopic amblyopia who had a spherical equivalent of ≥ +4.0 diopters (D) or more were included, while those who had astigmatism of > 2.0 D or anisometropia of > 2.0 D were excluded. The patients were divided into a full correction group and an under-correction group according to the amount of hyperopia correction applied. The under-correction group was further subdivided into a fixed under-correction group and a post-cycloplegic refraction (PCR) under-correction group. The duration of amblyopia treatment and changes in initial hyperopia were compared between the groups. RESULTS: In total, 76 eyes of 38 patients were analyzed in this study. The full correction group and under-correction group were subjected to 5.5 months and 5.9 months of amblyopia treatment, respectively (P = 0.570). However, the PCR under-correction group showed more rapid improvement (2.9 months; P = 0.001). In the under-correction group, initial hyperopia was decreased by -0.28 D and -0.49 D at 6 months and 12 months, respectively, after initial cycloplegic refraction. Moreover, the amount of hyperopia under-correction was correlated with the amount of hyperopia reduction (P = 0.010). CONCLUSION: The under-correction of moderate to severe hyperopic amblyopia has beneficial effects for treating amblyopia and activating emmetropization. PCR under-correction can more rapidly improve visual acuity, while both fixed under-correction and PCR under-correction can induce emmetropization and effectively reduce initial hyperopia.

Higher Order Aberration and Astigmatism in Children with Hyperopic Amblyopia.

PURPOSE: To investigate the changes in corneal higher-order aberration (HOA) during amblyopia treatment and the correlation between HOA and astigmatism in hyperopic amblyopia children. METHODS: In this retrospective study, a total of 72 eyes from 72 patients ranging in age from 38 to 161 months were included. Patients were divided into two groups based on the degree of astigmatism. Corneal HOA was measured using a KR-1W aberrometer at the initial visit and at 3-, 6-, and 12-month follow-ups. Correlation analysis was performed to assess the association between HOA and astigmatism. RESULTS: A total of 72 patients were enrolled in this study, 37 of which were classified as belonging to the higher astigmatism group, while 35 were assigned to the lower astigmatism group. There was a statistically significant difference in success rate between the higher and lower astigmatism groups. In both groups, all corneal HOAs were significantly reduced during amblyopia treatment. When comparing the two groups, a significant difference in coma HOA at the 12-month follow-up was detected (p = 0.043). In the Pearson correlation test, coma HOA at the 12-month follow-up demonstrated a statistically significant correlation with astigmatism and a stronger correlation with astigmatism in the higher astigmatism group than in the lower astigmatism group (coefficient values, 0.383 and 0.284 as well as p = 0.021 and p = 0.038, respectively). CONCLUSIONS: HOA, particularly coma HOA, correlated with astigmatism and could exert effects in cases involving hyperopic amblyopia.

Congenital aniridia: long-term clinical course, visual outcome, and prognostic factors.

PURPOSE: To describe the clinical course of congenital aniridia and to evaluate prognostic factors for visual outcome after long-term follow-up. METHODS: The medical records of 120 eyes from 60 patients with congenital aniridia were retrospectively reviewed. The prevalence and clinical course of ophthalmic characteristics, systemic disease, refractive errors, and visual acuity were assessed. Prognostic factors for final visual outcomes were analyzed. RESULTS: Aniridic keratopathy developed in 82 (69%) of 119 eyes. Macular hypoplasia was observed in 70 eyes of 35 patients (91%). Cataract was observed in 63 of 120 eyes (53%). Nystagmus was present in 41 patients (68% of 60 patients) at the initial visit but decreased in five patients (8% of 60 patients). Ocular hypertension was detected in 19 eyes (20% of 93 eyes), six (32% of 19 eyes) of which developed secondarily after cataract surgery. The mean changes in spherical equivalent and astigmatism during the follow-up period were -1.10 and 1.53 diopter, respectively. The mean final visual acuity was 1.028 logarithm of minimal angle of resolution. Nystagmus and ocular hypertension were identified as prognostic factors for poor visual outcome. CONCLUSIONS: Identification of nystagmus and ocular hypertension was important to predict final visual outcome. Based on the high rate of secondary ocular hypertension after cataract surgery, careful management is needed.

Intermolecular N-H oxidative addition of ammonia, alkylamines, and arylamines to a planar σ(3)-phosphorus compound via an entropy-controlled electrophilic mechanism.

Ammonia, alkyl amines, and aryl amines are found to undergo rapid intermolecular N-H oxidative addition to a planar mononuclear σ(3)-phosphorus compound (1). The pentacoordinate phosphorane products (1·[H][NHR]) are structurally robust, permitting full characterization by multinuclear NMR spectroscopy and single-crystal X-ray diffraction. Isothermal titration calorimetry was employed to quantify the enthalpy of the N-H oxidative addition of n-propylamine to 1 ((n)PrNH2 + 1 → 1·[H][NH(n)Pr], ΔHrxn(298) = -10.6 kcal/mol). The kinetics of n-propylamine N-H oxidative addition were monitored by in situ UV absorption spectroscopy and determination of the rate law showed an unusually large molecularity (ν = k[1][(n)PrNH2](3)). Kinetic experiments conducted over the temperature range of 10-70 °C revealed that the reaction rate decreased with increasing temperature. Activation parameters extracted from an Eyring analysis (ΔH(⧧) = -0.8 ± 0.4 kcal/mol, ΔS(⧧) = -72 ± 2 cal/(mol·K)) indicate that the cleavage of strong N-H bonds by 1 is entropy controlled due to a highly ordered, high molecularity transition state. Density functional calculations indicate that a concerted oxidative addition via a classical three-center transition structure is energetically inaccessible. Rather, a stepwise heterolytic pathway is preferred, proceeding by initial amine-assisted N-H heterolysis upon complexation to the electrophilic phosphorus center followed by rate-controlling N → P proton transfer.

The relationship between higher-order aberrations and amblyopia treatment in hyperopic anisometropic amblyopia.

PURPOSE: To investigate the relationship between higher-order aberrations (HOAs) and amblyopia treatment in children with hyperopic anisometropic amblyopia. METHODS: The medical records of hyperopic amblyopia patients with both spherical anisometropia of 1.00 diopter (D) or more and astigmatic anisometropia of less than 1.00 D were reviewed retrospectively. Based on the results of the amblyopia treatment, patients were divided into two groups: treatment successes and failures. Using the degree of spherical anisometropia, subjects were categorized into mild, moderate, or severe groups. Ocular, corneal, and internal HOAs were measured using a KR-1W aberrometer at the initial visit, and at 3-month, 6-month, and 12-month follow-ups. RESULTS: The results of the 45 (21 males and 24 females) hyperopic anisometropic amblyopia patients who completed the 12-month follow-up examinations were analyzed. The mean patient age at the initial visit was 70.3 months. In total, 28 patients (62.2%) had successful amblyopia treatments and 17 patients (37.8%) failed treatment after 12 months. Among the patient population, 24 (53.3%) had mild hyperopic anisometropia and 21 (46.7%) had moderate hyperopic anisometropia. When comparing the two groups (i.e., the success and failure groups), ocular spherical aberrations and internal spherical aberrations in the amblyopic eyes were significantly higher in the failure group at every follow-up point. There were no significant differences in any of the HOAs between mild and moderate cases of hyperopic anisometropia at any follow-up. When the amblyopic and fellow eyes were compared between the groups there were no significant differences in any of the HOAs. CONCLUSIONS: HOAs, particularly ocular spherical aberrations and internal spherical aberrations, should be considered as reasons for failed amblyopia treatment.

Changes in Visual Function over Time in Koreans with Non-arteritic Anterior Ischaemic Optic Neuropathy.

Non-arteritic anterior ischaemic optic neuropathy (NAION) causes severe visual loss in elderly patients. However, there are not much data of clinical course of NAION in Asian patients. To evaluate changes in visual acuity and visual field defects associated with non-arteritic anterior ischaemic optic neuropathy (NAION) among Korean patients, the medical records of 50 eyes from 43 patients with NAION patients seen from 1989 to 2011 were reviewed. A significant change in visual acuity was defined as a three-line change in Snellen acuity. Visual field defects were evaluated with Goldmann perimetry. Changes in the visual field were evaluated using the grid method. Thirty-eight percent of eyes showed improvement, 54% showed no change, and 8% showed deterioration of visual acuity at the last follow-up. Thirty-four percent of eyes showed improvement, 54% showed no change, and 12% showed deterioration of the visual field at the last follow-up. Most improvement in visual acuity occurred during the first month after the initial visit and in visual field between the first and third months of follow-up. The prognosis of visual acuity in association with NAION was worse in Korean patients as compared with Western studies. However, improved prognosis of visual field defects might come from the use of different methods for evaluation of the visual field.

Synthesis and modeling of hollow intermetallic Ni-Zn nanoparticles formed by the Kirkendall effect.

Intermetallic Ni-Zn nanoparticles (NPs) were synthesized via the chemical conversion of nickel NPs using a zerovalent organometallic zinc precursor. After the injection of a diethylzinc solution, Ni NPs progressively transformed from a solid to a hollow Ni-Zn intermetallic structure with time. During the transformation of Ni NPs to intermetallic structures, they retained their overall spherical morphology. The growth mechanism for the solid-to-hollow nanoparticle transformation is ascribed to the nanoscale Kirkendall effect due to unequal diffusion rates of Ni and Zn. We develop a diffusion model for nonreactive, homogeneous, diffusion-controlled intermetallic hollow NP formation including moving boundaries at the interfaces of void-solid and solid-bulk solutions. Apparent diffusion coefficients for both metals and vacancy were evaluated from modeling the time-dependent growth of the void. The apparent diffusion coefficients obtained in this system compared favorably with results from measurement at grain boundaries in bulk Ni-Zn. This study represents the first combined experimental modeling of the formation of hollow nanostructures by the nanoscale Kirkendall effect.

Long-term visual outcomes of penetrating keratoplasty for Peters anomaly.

BACKGROUND: To investigate the long-term results and visual outcomes of penetrating keratoplasty (PKP) in Peters anomaly. METHODS: Twenty-three eyes from 22 patients with Peters anomaly who underwent PKP from 1998 to 2008 were reviewed retrospectively. Patients who were followed for more than 3 years after the first PKP were included in this study. The systemic and ophthalmic features of the recipients were assessed, and the various prognostic factors for graft survival were evaluated. Disease severity was determined according to other accompanying eye anomalies in mild or severe form. The final visual outcomes were presented with respect to graft clarity. RESULTS: Among the 22 patients, 14 patients had unilateral disease, and eight patients had bilateral disease. Associated systemic anomalies were observed in six patients. The mean age at the first PKP was 42.4 months. Nineteen eyes (83 %) underwent PKP after 12 months of age. The graft failure rates at 1 year, 3 years, 5 years, and 10 years after PKP were 30 %, 39 %, 70 %, and 77 % respectively. Graft rejection within 1 month after PKP and severe disease were significant risk factors for graft failure. The mean final VAs in the clear-graft group and the failed-graft group were 1.883 logMAR and 2.767 logMAR (P < 0.001). CONCLUSION: The results of delayed PKP in Peters anomaly were not inferior compared to the results of PKP performed at an earlier period in previous studies. If other congenital ophthalmic anomalies were present or graft rejection occurred within 1 month after PKP, the chance of graft failure was significantly increased.

Clinical characteristics of optic neuritis in Koreans greater than 50 years of age.

PURPOSE: To report clinical characteristics of optic neuritis (ON) in Koreans >50 years of age. METHODS: A retrospective chart review was performed on patients with ON between January 2000 and December 2009. We obtained the best-corrected visual acuity (BCVA), Goldmann perimetry, relative afferent pupillary defect (RAPD), and color function tests as well as brain magnetic resonance imaging (MRI) findings in patients who were in the acute stage of the disorder. RESULTS: Nine eyes in eight patients were included. The mean age of patients at presentation was 60.5 years (range, 53 to 71 years). Six patients were female, and two were male. There was one patient with bilateral ON. The mean BCVA at presentation was 20 / 400 (no light perception-20 / 70). Eight eyes (89%) complained of pain with eye movement. Six eyes (66%) had disc edema. Central scotoma was the most common field defect. All eyes had color abnormalities. Five eyes in four patients showed abnormalities of the involved optic nerves on MRI. The patients were followed for a mean of 11.3 months (range, 2 to 34 months). All of the patients recovered to a BCVA of 20 / 40 or better within 2 months. On the last follow-up, the mean BCVA was 20 / 20 (20 / 40 to 20 / 16). Four eyes showed remnant central scotoma. One eye had remnant RAPD, and two eyes had mild color abnormalities. CONCLUSIONS: Although ON is uncommon in elderly patients, it can develop in patients >50 years of age, and clinical features of optic neuritis in elderly patients are similar to those of younger patients.

The long-term survival analysis of bilateral lateral rectus recession versus unilateral recession-resection for intermittent exotropia.

PURPOSE: To conduct a comparison of the long-term surgical outcomes of bilateral lateral rectus recession (BLR) vs unilateral lateral rectus recession-medial rectus resection (RR) in treatment of intermittent exotropia. DESIGN: Nonrandomized, retrospective case series. METHODS: Consecutive patients who underwent BLR or RR for treatment of intermittent exotropia between 2002 and 2006 and had ≥2 years' follow-up were recruited. Surgical outcomes were grouped according to postoperative angle of deviation as overcorrection (esophoria/tropia >5 Δ), success (esophoria/tropia ≤5 Δ to exophoria/tropia ≤10 Δ), or undercorrection/recurrence (exophoria/tropia >10 Δ), and were compared between the BLR group and the RR group at postoperative 1 day, 1 month, 6 months, 1 year, and 2 years, and at the final examination. RESULTS: Of 128 patients, 55 underwent BLR and 73 underwent RR. The mean follow-up period was 44.2 months in the BLR group and 47.8 months in the RR group. At 1 day, 1 month, 6 months, 1 year, and 2 years after surgery, surgical outcomes in each group were not different (P > .05) However, the final outcome at a mean of 3.8 years was significantly different between the groups, demonstrating a higher success rate in the BLR group than in the RR group (58.2% vs 27.4%, P < .01). Cumulative probability of survival from recurrence was higher in the BLR group than in the RR group (P = .01, log-rank test). Recurrences were most common within 6 months from surgery; however, after that, recurrences occurred continuously in the RR group and rarely in the BLR group. CONCLUSION: Surgical outcomes by 2 years after surgery for intermittent exotropia were not different between the BLR and RR groups. However, final outcomes were better in the BLR group than in the RR group. This may be caused by the difference of recurrence rate over time: continuous recurrence of exotropia occurred in the RR group, while recurrence was low in the BLR group after postoperative 6 months.

The clinical outcomes of proton beam radiation therapy for retinoblastomas that were resistant to chemotherapy and focal treatment.

PURPOSE: To evaluate the clinical results of proton beam radiation therapy (PBRT) for treatment of retinoblastoma. METHODS: Children with retinoblastoma who were treated with chemotherapy and focal treatment such as brachytherapy and thermotherapy but showed no response or developed recurrences later received PBRT. The PBRT strategy was designed to concentrate the radiation energy to the retinoblastoma and spare the surrounding healthy tissue or organs. RESULTS: There were three patients who received PBRT. The first patient received PBRT because of an initial lack of tumor regression with chemotherapy and brachytherapy. This patient showed regression after PBRT. The second patient who developed recurrence of retinoblastoma as diffuse infiltrating subretinal seeding was taken PBRT. After complete regression, there was recurrence of tumor and the eye was enucleated. The third patient had unilateral extensively advanced retinoblastoma. Initial chemotherapy failed and tumor recurred. The tumor responded to PBRT and regressed significantly. However, the eye developed sudden multiple recurrences, so we had to perform enucleation. CONCLUSIONS: PBRT for retinoblastoma was effective in cases of showing no response to other treatment modalities. However, it should be carefully applied when there was recurrence of diffuse infiltrating subretinal seeding or extensively advanced retinoblastoma initially.

Surgical treatment of an enlarging retinal cyst associated with a choroidal coloboma.

PURPOSE: The purpose of this study was to describe a case of an enlarging retinal cyst associated with a choroidal coloboma, which was treated surgically in a child. METHODS: A retrospective case report. RESULTS: A funduscopic examination of a 5-year-old boy revealed a retinal cyst in the inferonasal area of the right fundus. The corrected visual acuity at initial examination was 20/40. During the follow-up period, the retinal cyst waxed and waned spontaneously. Seven years after the first examination, the visual acuity decreased to 20/1000 due to an enlarged retinal cyst, which obscured the macula and did not recover. At the 9-year follow-up, barrier laser around the retinal cyst and pars plana vitrectomy with retinectomy, internal drainage of the cyst, and 14% C3F8 gas tamponade were performed. There was a colobomatous choroidal defect at the base of the retinal cyst. The patient's visual acuity improved to 20/25, and the retina remained flat at the 2-year follow-up postoperatively. CONCLUSION: We managed a very rare case of a retinal cyst associated with a choroidal coloboma. During the 9-year follow-up, the retinal cyst waxed and waned spontaneously. The enlarging retinal cyst that caused visual impairment was treated successfully by barrier laser and vitreous surgery. The visual acuity recovered completely.