Rationale for the diabetic retinopathy clinical research network treatment protocol for center-involved diabetic macular edema.

OBJECTIVE: To describe the underlying principles used to develop a web-based algorithm that incorporated intravitreal anti-vascular endothelial growth factor (anti-VEGF) treatment for diabetic macular edema (DME) in a Diabetic Retinopathy Clinical Research Network (DRCR.net) randomized clinical trial. DESIGN: Discussion of treatment protocol for DME. PARTICIPANTS: Subjects with vision loss resulting from DME involving the center of the macula. METHODS: The DRCR.net created an algorithm incorporating anti-VEGF injections in a comparative effectiveness randomized clinical trial evaluating intravitreal ranibizumab with prompt or deferred (≥24 weeks) focal/grid laser treatment in eyes with vision loss resulting from center-involved DME. Results confirmed that intravitreal ranibizumab with prompt or deferred laser provides superior visual acuity outcomes compared with prompt laser alone through at least 2 years. Duplication of this algorithm may not be practical for clinical practice. To share their opinion on how ophthalmologists might emulate the study protocol, participating DRCR.net investigators developed guidelines based on the algorithm's underlying rationale. MAIN OUTCOME MEASURES: Clinical guidelines based on a DRCR.net protocol. RESULTS: The treatment protocol required real-time feedback from a web-based data entry system for intravitreal injections, focal/grid laser treatment, and follow-up intervals. Guidance from this system indicated whether treatment was required or given at investigator discretion and when follow-up should be scheduled. Clinical treatment guidelines, based on the underlying clinical rationale of the DRCR.net protocol, include repeating treatment monthly as long as there is improvement in edema compared with the previous month or until the retina is no longer thickened. If thickening recurs or worsens after discontinuing treatment, treatment is resumed. CONCLUSIONS: Duplication of the approach used in the DRCR.net randomized clinical trial to treat DME involving the center of the macula with intravitreal ranibizumab may not be practical in clinical practice, but likely can be emulated based on an understanding of the underlying rationale for the study protocol. Inherent differences between a web-based treatment algorithm and a clinical approach may lead to differences in outcomes that are impossible to predict. The closer the clinical approach is to the algorithm used in the study, the more likely the outcomes will be similar to those published. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

Effects of ranibizumab on exudative disciform scars.

BACKGROUND AND OBJECTIVE: To evaluate the effect of intravitreal ranibizumab in patients with leaking disciform scars. PATIENTS AND METHODS: In this retrospective case series, 31 eyes received one or two ranibizumab injections for treatment of choroidal neovascularization. Visual acuity, central retinal thickness, and macular volume were measured prior to injection and at 1-month follow-up. RESULTS: After one injection (n = 31), mean optical coherence tomography (OCT) central foveal thickness decreased from 317 to 242 microm (P = .00016). Mean OCT macular volume decreased from 7.89 to 6.80 mm3 (P = .00019). After two injections (n = 12), mean OCT central foveal thickness decreased from 310 to 248 microm following the second injection (P = .04). Mean OCT macular volume decreased from 7.80 to 6.43 mm3 at 1-month follow-up after a second injection (P = .006). There was no significant change in visual acuity after injections. CONCLUSION: In the short-term, ranibizumab decreases the leakage associated with choroidal neovascularization in chronic macular degeneration.

Preoperative visual acuity as a prognostic indicator for laser treatment of macular edema due to branch retinal vein occlusion.

BACKGROUND AND OBJECTIVE: To determine the visual outcome of laser treatments for macular edema due to branch retinal vein occlusion (BRVO) in patients with a preoperative visual acuity (VA) of 20/200 or worse compared to patients with a preoperative VA of better than 20/200. PATIENTS AND METHODS: Records of 88 patients with macular edema secondary to BRVO undergoing laser treatment from 1984 to 2003 were reviewed. Mean VA was measured before and after each treatment and after the final treatment. RESULTS: All patients received between one and five laser treatments. Preoperative VA was better than 20/200 in 56 patients (group 1) and 20/200 or worse in 32 patients (group 2). Patients in group 1 had a mean improvement of 0.48 lines and 57% had a final VA of 20/40 or better. Patients in group 2 had a mean improvement of 1.69 lines and 20% had a final VA of 20/40 or better. CONCLUSIONS: Patients with poor VA (20/200 or worse) secondary to macular edema due to BRVO responded positively to laser treatment. The level of preoperative VA can be a useful predictor of visual outcome. These patients should consider laser treatment before alternative, more aggressive approaches.

Diurnal variation in retinal thickening measurement by optical coherence tomography in center-involved diabetic macular edema.

OBJECTIVE: To evaluate diurnal variation in retinal thickness measured with optical coherence tomography (OCT) in patients with center-involved diabetic macular edema. METHODS: Serial OCT3 measurements were performed in 156 eyes of 96 subjects with clinically diagnosed diabetic macular edema and OCT central subfield retinal thickness of 225 microm or greater at 8 am. Central subfield thickness was measured from OCT3 retinal thickness maps at 6 points over a single day between 8 am and 4 pm. A change in central subfield thickening (observed thickness minus mean normal thickness) of at least 25% and of at least 50 microm at 2 consecutive points or between 8 am and 4 pm was considered to have met the composite outcome threshold. RESULTS: At 8 am, the mean central subfield thickness was 368 microm and the mean visual acuity was 66 letters (approximately 20/50). The mean change in relative central subfield retinal thickening between 8 am and 4 pm was a decrease of 6% (95% confidence interval, -9% to -3%) and the mean absolute change was a decrease of 13 microm (95% CI, -17 to -8). The absolute change was significantly greater in retinas that were thicker at 8 am (P<.001) but the relative change was not (P = .14). The composite threshold of reduction in central subfield thickening (as defined above) was observed in 5 eyes of 4 subjects (3% of eyes; 95% CI, 1% to 8%) while 2 eyes of 2 subjects (1%; 95% CI, 0% to 5%) had an increase in central subfield thickening of this same magnitude. The maximum decrease was observed at 4 pm in all 5 eyes. CONCLUSION: Although on average there are slight decreases in retinal thickening during the day, most eyes with diabetic macular edema have little meaningful change in OCT central subfield thickening between 8 am and 4 pm.

A pilot study of multiple intravitreal injections of ranibizumab in patients with center-involving clinically significant diabetic macular edema.

OBJECTIVE: To evaluate the biologic activity of multiple intravitreal injections of ranibizumab in patients with center-involving clinically significant diabetic macular edema (DME) and to report any associated adverse events. DESIGN: Single-center, open-label, dose-escalating pilot study. PARTICIPANTS: A total of 10 eyes of 10 patients (mean age, 69.3 years [range, 59-81]) with DME involving the center of the macula and best-corrected visual acuity (BCVA) in the study eye between 20/63 and 20/400. INTERVENTION: Three intravitreal injections of ranibizumab (0.3 mg or 0.5 mg each injection) administered on day 0, month 1, and month 2, and observation until month 24. MAIN OUTCOME MEASURES: Primary end points were the frequency and severity of ocular and systemic adverse events. Secondary end points were BCVA and measurement of retinal thickness by optical coherence tomography. RESULTS: Of the 10 patients enrolled, 5 received 0.3-mg and 5 received 0.5-mg ranibizumab. Intravitreal injections of ranibizumab were well tolerated. No systemic adverse events were reported. Five occurrences of mild to moderate ocular inflammation were reported. At month 3, 4 of 10 patients gained > or =15 letters, 5 of 10 gained > or =10 letters, and 8 of 10 gained > or =1 letters. At month 3, the mean decrease in retinal thickness of the center point of the central subfield was 45.3+/-196.3 microm for the low-dose group and 197.8+/-85.9 microm for the high-dose group. CONCLUSIONS: Ranibizumab appears to be a well-tolerated therapy for patients with DME. This pilot study demonstrates that ranibizumab therapy has the potential to maintain or improve BCVA and reduce retinal thickness in patients with center-involved clinically significant DME.

Multiple laser treatments for macular edema attributable to branch retinal vein occlusion.

PURPOSE: To report the visual outcome of multiple laser treatments for macular edema attributable to branch retinal vein occlusions (BRVO) and to determine if any prognostic factors exist for improvement. DESIGN: Retrospective chart review. METHODS: A private practice with four vitreoretinal surgeons performed laser treatments on 88 eyes of 88 patients with macular edema secondary to BRVO from 1984 to 2003. Mean preoperative and postoperative visual acuities were collected after each laser treatment. Final visual acuities were also documented. RESULTS: All 88 patients received at least one laser treatment, and 46 patients of the initial 88 underwent multiple treatments. Overall, forty-one (46.6%) of the total 88 patients improved by 2 or more lines, whereas 33 patients (37.5%) were within 1 line of the preoperative vision, and 14 patients (15.9%) worsened by 2 or more lines. The mean final visual improvement was 0.92 lines for all 88 patients. The group of patients that responded favorably to the first laser treatment (n = 37) showed an overall improvement of 3.5 lines. However, patients who responded poorly to the first laser treatment resulted in an overall worsening of vision by 0.96 lines. CONCLUSIONS: Our study found that multiple laser treatments can improve visual acuity and resolve macular edema and that each additional laser treatment gives a patient a modest chance of visual improvement. A positive or stable visual response to first laser treatment portends a favorable prognosis with subsequent laser treatments.

Localization of disulfide bonds in the frizzled module of Ror1 receptor tyrosine kinase.

The frizzled (FRZ) module is a novel module type that was first identified in G-protein-coupled receptors of the frizzled and smoothened families and has since been shown to be present in several secreted frizzled-related proteins, in some modular proteases, in collagen XVIII, and in various receptor tyrosine kinases of the Ror family. The FRZ modules constitute the extracellular ligand-binding region of frizzled receptors and are known to mediate signals of WNT family members through these receptors. With an eye toward defining the structure of this important module family, we have expressed the FRZ domain of rat Ror1 receptor tyrosine kinase in Pichia pastoris. By proteolytic digestion and amino acid sequencing the disulfide bonds were found to connect the 10 conserved cysteines in a 1-5, 2-4, 3-8, 6-10, and 7-9 pattern. Circular dichroism and differential scanning calorimetry studies on the recombinant protein indicate that the disulfide-bonded FRZ module corresponds to a single, compact, and remarkably stable folding domain possessing both alpha-helices and beta-strands.

Chemical modification and nuclear magnetic resonance studies on human plasminogen kringle 4. Assignment of tyrosine and histidine resonances to specific residues in the sequence.

Modification of kringle 4 with tetranitromethane leads to the selective nitration of tyrosine 40 but on prolonged incubation with reagent, reaction of tyrosine 49 is also observed. Nitration of tyrosines 40 and 49 had no influence on the lysine-Sepharose affinity of kringle 4, indicating that these residues are not important for the functional integrity of the ligand-binding site. Comparison of the NMR spectra of native kringle 4 with those of kringle 4 in which tyrosine 40 or tyrosines 40 and 49 are nitrated permitted the identification of the resonances of these residues. These NMR studies also showed that the chemical modifications caused little perturbation of the three-dimensional structure of the protein. Cross-linking of lysine 35 and tyrosine 40 with 1,3-difluoro-4,6-dinitrobenzene demonstrates that in the kringle-fold the reactive epsilon-amino and phenolic groups of these residues can approach each other to a distance of 0.5 nm. NMR spectra of this kringle 4 species also confirmed the assignment of the resonances to tyrosine 40. NMR spectra of a kringle 4 derivative in which the disulphide bridge between cysteines 1 and 79 has been broken by selective reduction and alkylation showed that the core structure of the kringle-fold and the lysine-binding site are unaltered by this modification. This observation is in agreement with earlier results which showed that the lysine-Sepharose affinity of kringle 4 is not affected by reduction and alkylation of this disulphide bridge. Comparison of the NMR spectra of native and disulphide-cleaved kringle 4 aided in the assignment of resonances to residues adjacent to the site of modification (tyrosine 2 and histidine 3) and permitted the tentative assignment of the resonances of tyrosines 9 and 73.

Residues Cys-1 and Cys-79 are not essential for refolding of reduced-denatured kringle 4 fragment of human plasminogen.

It was shown previously that the Cys-1-Cys-79 disulphide bond forms in the last step of refolding of kringle 4 and that this bond is not essential for the lysine-Sepharose affinity of the kringle 4 fragment (Trexler, M. and Patthy, L. (1983) Proc. Natl. Acad. Sci. U.S.A. 80 2457-2461). Here we show that kringle 4, carboxymethylated on Cys-1 and Cys-79, regains its lysine-Sepharose affinity following denaturation and reductive cleavage of its disulphide bonds. The rate of refolding under aerobic conditions or in the presence of oxidized and reduced glutathione was similar to that observed in the case of native kringle 4. Our results suggest that Cys-1 and Cys-79 residues of kringles are not essential for the maintenance or acquisition of the biologically active kringle-fold.