Evaluation of the blood–aqueous barrier by laser flare cell photometry following retinal cryocoagulation

The Blood-ocular Barriers and their Dysfunction: Anatomy, Physiology, Pathology

Complex barriers comprise the blood-aqueous (BAB) and the blood-retinal barrier (BRB), and separate anterior and posterior eye chambers, vitreous body, and sensory retina from the circulation. They prevent pathogens and toxins from entering the eye, control movement of fluid, proteins, and metabolites, and contribute to the maintenance of the ocular immune status. Morphological correlates of blood-ocular barriers are tight junctions between neighboring endothelial and epithelial cells, which function as gatekeepers of the paracellular transport of molecules, thereby limiting their uncontrolled access to ocular chambers and tissues. The BAB is composed of tight junctions between endothelial cells of the iris vasculature, endothelial cells of Schlemm's canal inner wall, and cells of the nonpigmented ciliary epithelium. The BRB consists of tight junctions between endothelial cells of the retinal vessels (inner BRB) and epithelial cells of the retinal pigment epithelium (outer BRB). These junctional complexes respond rapidly to pathophysiological changes, thus enabling vascular leakage of blood-derived molecules and inflammatory cells into ocular tissues and chambers. Blood-ocular barrier function, which can be clinically measured by laser flare photometry or fluorophotometry, is compromised in traumatic, inflammatory, or infectious processes, but also frequently contributes to the pathophysiology of chronic diseases of the anterior eye segment and the retina, as exemplified by diabetic retinopathy and age-related macular degeneration.

ANTERIOR CHAMBER FLARE DURING BEVACIZUMAB TREATMENT IN EYES WITH EXUDATIVE AGE-RELATED MACULAR DEGENERATION

PURPOSE

To study the anterior chamber flare during bevacizumab treatment of exudative age-related macular degeneration.

METHODS

During a 2-year prospective follow-up, 50 patients recently diagnosed with exudative age-related macular degeneration were treated at once-a-month visits if subretinal or intraretinal fluid or a new hemorrhage was present in the lesion area. Flare was measured weekly during the first month and then monthly in both eyes.

RESULTS

Higher flare was associated with older age (P = 0.007, Linear Mixed Model), higher number of smoking pack-years (P = 0.019), macular cysts (P = 0.041), and pseudophakia (P = 0.003). The levels gradually increased during the follow-up (P < 0.0001) but less in the eyes with classic CNV (P = 0.011). Flare decreased during treatment-free periods lasting for at least two consecutive visits (P = 0.005). A peak in flare was observed 1 week after the first injection (P = 0.034, Wilcoxon signed rank test). In the fellow eyes, higher flare values in the beginning of the follow-up were associated with later conversion into exudative age-related macular degeneration (P = 0.015, Mann-Whitney U test).

CONCLUSION

Anterior chamber flare correlated poorly with the CNV activity. Higher levels may, however, precede or exist early in the process that leads to the development of exudative age-related macular degeneration.

Short Pulse Duration High-Power Laser Photocoagulation during Vitrectomy for Diabetic Retinopathy Reduces Postoperative Inflammation

The aim of this preliminary study was to determine the effectiveness of short pulse duration, high-power laser photocoagulation (PC) during vitrectomy for diabetic retinopathy (DR).The effects of short pulse duration PC with power of 340-360 mW and duration of 0.02 second were compared to conventional PC with power of 120-150 mW and duration of 0.2 second. The degree of inflammation was quantified by laser flare cell photometry before and at 1 day, 1 week, 4 week, and 12 weeks postoperatively. Twenty-two eyes of 22 consecutive patients were studied. Ten eyes were treated with short pulse duration PC and 12 eyes with conventional PC. The total energy was significantly lower in the short pulse duration PC group than in the conventional PC group (P = 0.007). The flare cell values were not significantly different between the two groups after 1 day, but at 1 week, the flare cell value was significantly lower in the short pulse duration PC group than in the conventional PC group (P = 0.04). This difference was also present at 4 and 12 weeks (P<0.05). The significant lower inflammation after short pulse duration PC than conventional PC indicates that the short pulse duration PC protocol should be considered to treat DR.

Cryotherapy of sclerotomy sites for prevention of late post-vitrectomy diabetic hemorrhage: a randomized clinical trial

BACKGROUND

To evaluate the role of cryotherapy of sclerotomy sites in prevention of late (after 4 weeks) post-vitrectomy diabetic hemorrhage.

METHODS

In a prospective randomized double-masked clinical trial, a total of 124 eyes of 119 patients underwent pars plana vitrectomy for complications of proliferative diabetic retinopathy. At the end of vitrectomy, the eyes were randomly assigned to two groups. The case group received two cryotherapy spots at each sclerotomy site, whereas the eyes in the control group received no further intervention. Evaluations were repeated at months 1, 2, 4, and 6. The primary outcome measure was occurrence of vitreous hemorrhage after the first month and up to the sixth month. Ultrasound biomicroscopy (UBM) examination of the sclerotomy sites was performed concurrent with the occurrence of vitreous hemorrhage or at the last follow-up.

RESULTS

Thirty-six eyes were excluded mostly because of early postoperative vitreous hemorrhage. Finally, the data of 42 eyes of the cases and 46 eyes of the controls were used for analysis. Late vitreous hemorrhage occurred in 17 out of 88 eyes (19.3%). This rate was significantly higher in the cases compared to the controls, 28.6% (12 eyes) versus 10.9% (five eyes) within 6 months (P = 0.036). There was no statistically significant difference in the UBM findings of the sclerotomy sites between the two groups. No relationship was noticed between morphologic patterns detected by UBM and occurrence of late vitreous hemorrhage.

CONCLUSIONS

Cryotherapy of the sclerotomy sites at the end of the operation is not helpful for prevention of late post-vitrectomy diabetic hemorrhage, and it may even increase this risk.

Alterations of aqueous flare and cells detected by laser flare-cell photometry in patients with Behcet's disease

PURPOSE

To quantitatively evaluate aqueous flare and cells in patients with Behcet's disease.

METHODS

This study included 30 Behcet's patients (52 eyes) with active uveitis. The patients were treated with immunosuppressive agents. Aqueous flare and cells were quantified using the laser flare-cell photometry before treatment and 1 and 2 months after treatment.

RESULT

Before treatment, mean aqueous flare (ph/ms) in Behcet's eyes was 25.7 ± 20.5. After treatment, flare values were significantly reduced after 1 and 2 months compared with those before treatment. No significant difference was found between flare values after 1 and 2 months. Before treatment, mean cell counts (cells/0.5 mm(3)) in Behcet's eyes were 23.2 ± 29.4. After treatment, cell counts were also significantly reduced after 1 and 2 months compared with those before treatment. Cell counts were further significantly reduced from 1 to 2 months.

CONCLUSION

Both aqueous flare and cells were significantly increased in Behcet's patients with active uveitis and improved after a two-month treatment. Breakdown of the blood-aqueous barrier lasts longer than aqueous cells in these patients.

Laser flare-cell photometry: methodology and clinical applications

Diagnosis and management of intraocular inflammation involves the assessment of cells and protein levels ("flare") in the aqueous humor. These factors are difficult to quantify precisely on clinical examination alone. Laser flare-cell photometry provides an automated technique to quantify these factors objectively, and it has been used in a variety of research and clinical situations to assess anterior segment inflammation. Any new technique requires evaluation to determine accuracy and reproducibility of measured values, and initial applications require critical appraisal to assess the value of the technique. Both in vitro and in vivo studies of laser flare-cell photometry have been performed to determine its validity and utility as a research and clinical tool. This article reviews published studies that describe the technique of laser flare-cell photometry; it provides new in vitro data that supplements information on the capabilities of this technique and factors that influence photometry results, and it reviews representative publications that have used laser flare-cell photometry for study of specific disease entities. This information can help clinicians and researchers to become familiar with the strengths and limitations of laser flare-cell photometry, to identify appropriate future uses for this technique, and to use it and interpret its results appropriately. Laser flare-cell photometry offers an opportunity to improve upon current techniques of inflammation assessment and should not be considered simply an objective surrogate for clinical grading of cells and flare at the slit-lamp biomicroscope. Its research applications and utility for monitoring patients with uveitis have not yet been fully explored.