Half-Dose vs. Half-Time PDT for Central Serous Chorioretinopathy
Photodynamic therapy (PDT) with verteporfin has proved effective in both acute and chronic central serous chorioretinopathy (CSC); however, this therapy is associated with dose-dependent ocular complications. Liu et al. compared the efficacy of 2 lower-risk treatment protocols—using either half-dose or half-time PDT exposure—and found that both regimens led to significant visual and anatomic improvement.
The authors carried out a retrospective chart review in Taiwan of 61 eyes that received PDT guided by fluorescein angiography for acute or chronic CSC involving the fovea. Of these eyes, 35 received half-dose PDT, and 26 received half-time PDT. Best-corrected visual acuity (BCVA) was measured at baseline and at post-PDT follow-up visits. Two clinical markers were defined for evaluating treatment efficacy: complete resolution of subretinal fluid (SRF) and recurrence of SRF, as measured on optical coherence tomography.
Both groups showed significant improvement in BCVA at months 1, 3, 6, and 12 after treatment, and multiple regression analysis showed that the type of PDT was not significantly correlated with visual improvement. All eyes that received half-time PDT showed complete resolution of SRF within 6 months after treatment; 3 eyes that received half-dose PDT had persistent SRF, but because they were lost to follow-up at months 5, 7, and 8, no conclusions could be drawn about their ultimate outcomes. Three of 32 eyes in the half-dose group and 2 of 26 eyes in the half-time group had recurrence of SRF, but all had complete resolution after another PDT treatment. No adverse systemic or ocular side effects were observed in any cases.
The authors noted that their study was limited by its retrospective nature and by the small patient population, which lacked the statistical power to determine significant differences between the 2 groups in treatment effects. Nevertheless, they concluded that both half-dose and half-time PDT regimens were effective in treating CSC.
Comparing Glaucomatous Disc Change With Stereo Viewing vs. MatchedFlicker Software
Optic disc evaluation is important in following glaucoma progression. However, in practice, examination of sequential simultaneous stereo photographs is time consuming, requires specialized equipment, and thus is not routinely performed. Schaefer et al. compared this method against a new software program, MatchedFlicker (Flicker) and found that the latter was faster and more specific, but less sensitive, in identifying progression when used by ophthalmologists in training.
In this study, 2 resident ophthalmologists and 1 glaucoma fellow in the same university program independently evaluated 140 image pairs from 100 glaucomatous/ocular hypertensive patient eyes. Among these images, 50 pairs had been assessed by the Ocular Hypertension Treatment Study reading center as showing progression over 1 to 5 years; 50 others were taken minutes apart and served as controls; and 20 duplicates were chosen from each group to assess observer variability.
The observers viewed each of the image pairs by both methods: (1) using 2 sets of stereo viewers to compare changes and (2) using Flicker, which superimposes images on a computer screen and then rapidly “flickers” between them so that any differences between the pairs appears as motion. Using the handheld stereo viewer, the observers correctly identified progression or nonprogression in 76.0% of the slide pairs versus 87.6% using Flicker. Assessment speed averaged 34.1 seconds per image pair with the stereo viewer versus 24.9 seconds with the Flicker program. In this group of trainees, Flicker was, overall, significantly more specific but less sensitive than stereo slides; and, in particular, it was more accurate for the 2 less-experienced residents.
The authors also noted that Flicker data can be integrated more easily than stereo pairs into electronic medical records. They concluded that Flicker has good clinical potential for detecting glaucoma progression when used in conjunction with other functional and structural tests.
Preloaded Tissues for DMEK
In a laboratory study, Parekh et al. tested the feasibility of preloading endothelial tissue, rolled inside a cartridge, for use in Descemet membrane endothelial keratoplasty (DMEK). They found that grafts they prepared using this method survived and showed active metabolism for up to 4 days.
The researchers experimented with 20 human corneas that were deemed unsuitable for transplantation. Their method involved punching out and stripping the donor endothelium to 8.5-mm diameter, manually tri-folding the graft with the endothelium inward, placing it gently into an intraocular lens cartridge, and filling the cartridge with transport medium (TM). The tissue was stored for 4 days at room temperature in TM and assessed for viability. They cautioned that, because the TM contains bovine serum, the graft would need to be washed gently with balanced salt solution before being transplanted in a human eye.
In all 20 cases, the researchers were able to successfully peel and load the tissues, at average times of 20 minutes each for stripping and 4.5 minutes for loading. There was no endothelial cell loss immediately after the stripping procedure, although there was 4.35% loss after preservation. Cell mortality was observed only at the folds, and after a learning curve, the researchers found that mortality could be reduced to minimal or none.
The researchers concluded that this method of endothelial tissue preparation could reduce the time, difficulty, and potential waste of donor tissue in DMEK. However, they noted that their study was a proof of concept and has not yet undergone clinical evaluation.
American Journal of Ophthalmology summaries are written by Peggy Denny and edited by Richard K. Parrish II, MD.
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