Photocoagulation Up to Ora Serrata in Diabetic Vitrectomy to Prevent Recurrent Vitreous Hemorrhage.

PURPOSE: To evaluate the role of performing photocoagulation up to ora serrata during vitrectomy in preventing recurrent vitreous hemorrhage (VH) in patients undergoing pars plana vitrectomy (PPV) for proliferative diabetic retinopathy (PDR). METHODS: This retrospective, nonrandomized study included 60 eyes from 60 patients who had undergone PPV for VH due to PDR. These patients were divided into two groups: group 1, those who underwent photocoagulation up to ora serrata using the scleral indentation technique during surgery; and group 2, those who did not undergo scleral indentation when photocoagulation and underwent photocoagulation up to vortex veins. Their hospital records were analyzed to investigate the recurrence rate of VH, the time until recurrence of VH after surgery, logarithm of the minimal angle of resolution (logMAR) best-corrected visual acuity (BCVA) measured before surgery and at 1, 2, and 3 years after surgery, and the occurrence of complications such as neovascular glaucoma (NVG) during follow-up. RESULTS: Group 1 exhibited lower recurrence rate of VH (2 of 30 [6.7%] vs. 10 of 30 [33.3%], p = 0.01) and lower occurrence of postoperative NVG (2 of 30 [6.7%] vs. 8 of 30 [26.7%], p = 0.038) compared with group 2. There were no statistically significant differences in logMAR BCVA measured at 1, 2, and 3 years between the two groups (at 1 year: 0.54 ± 0.43 vs. 0.54 ± 0.44, p = 0.954; at 2 years: 0.48 ± 0.47 vs. 0.55 ± 0.64, p = 0.235; at 3 years: 0.51 ± 0.50 vs. 0.61 ± 0.77, p = 0.200). Logistic regression analysis showed that among several factors that could affect recurrence rate of VH, only range of photocoagulation performed was a statistically significant factor (odds ratio, 0.119; 95% confidence interval, 0.022-0.659; p = 0.015). CONCLUSIONS: Photocoagulation treatment over a wider range with scleral indentation could be a beneficial adjunct procedure for preventing postoperative recurrent VH following diabetic vitrectomy.

Design and fabrication of diffractive optical elements by use of gray-scale photolithography.

Diffractive optical elements (DOEs) are key components in the miniaturization of optical systems because of their planarity and extreme thinness. We demonstrate the fabrication of DOEs by use of gray-scale photolithography with a high-energy-beam sensitive glass photomask. We obtained DOE lenses with continuous phase profiles as small as 800 microm in diameter and 5.9 microm in the outermost grating pitch by selecting a suitable optical density for each height level and optimizing the process variables. Microlenses patterned with eight levels and replicated by UV embossing with the polymer master mold showed a diffraction efficiency of 81.5%, which was sufficiently high for the devices to be used as optical pickups. The effects of deviations in diffraction efficiency between the DOE height and profile design were analyzed.