Disruption of the blood-aqueous barrier following retinal laser photocoagulation and cryopexy in pigmented rabbits

Clinical factors contributing to postoperative aqueous flare intensity after 27-gauge pars plana vitrectomy for the primary rhegmatogenous retinal detachment

PURPOSE

To investigate the perioperative clinical factors, which contribute to the postsurgical aqueous flare intensity (AFI) following 27-gauge pars plana vitrectomy (27GPPV) for primary rhegmatogenous retinal detachment (RRD).

STUDY DESIGN

Retrospective clinical study.

METHODS

We performed retrospective analyses of the medical records of 47 eyes of 47 patients with primary RRD who had undergone 27GPPV with a wide-angle viewing system. AFI was measured preoperatively and 1 week, 1 month, 3 months, 6 months, and 12 months after the surgery.

RESULTS

AFI was significantly increased 1 week after the surgery (p<0.01) and then decreased overtime. At 6 months after surgery it was still statistically significantly higher than preoperative AFI (p=0.03). There was no statistical difference between preoperative AFI and that at 12 months following surgery. Multiple regression analyses revealed that the number of retinal photocoagulations and the performance of scleral indentation had significant positive correlation with AFI at 1 week, 1 month, 3 months, and 6 months, and at 1 month and 3 months after the surgery, respectively.

CONCLUSION

Intraoperative retinal photocoagulation and scleral indentation are probable causes of increased AFI after 27G PPV for RRD.

Laser flare-cell photometer: principle and significance in clinical and basic ophthalmology

A slit-lamp examination is an indispensable and essential clinical evaluation method in ophthalmology, but, it is qualitative subjective. To complement its weaknesses in making a quantitative evaluation of flare intensity and number of cells in the aqueous humor in the eye, we invented the laser flare-cell photometer in 1988. The instrument enables a non-invasive quantitative evaluation of flare intensity and number of cells in the aqueous with good accuracy and repeatability as well as maneuverability equal to slit-lamp microscopy. The instrument can elucidate the pathophysiology in the blood-aqueous barrier (BAB) function in a variety of ocular disorders. The accuracy of the instrument makes it possible to investigate not only the pathophysiology of intraocular disorders but also the effects of various drugs and surgical procedures in BAB. The instrument does not only lighten the burden on patients in clinical examinations and study but it also helps minimize the sacrifice of experimental animals and improves the reliability of the results by minimizing inter-individual variations through its good repeatability. Here I shall relate how the instrument has been applied to clinical and basic studies in ophthalmology and what novel knowledge its application contributed to pathophysiology in ophthalmology.

Comparison of macular thickness and inflammatory cytokine levels after microincision versus small incision coaxial cataract surgery

PURPOSE

To compare the macular thickness and volume change, and inflammatory cytokine levels after cataract surgery performed using two different sizes of incision (microincision versus small incision).

METHODS

In this randomized, comparative clinical trial, 84 eyes with nuclear density from Grade 3-4 were randomly divided into two groups (microincision, 2.2 mm; and small incision, 2.75 mm). Forty-two patients underwent phacoemulsification with microincision coaxial cataract surgery and 42 patients underwent phacoemulsification with small incision coaxial cataract surgery. Clinical measurements included preoperative, 1-week, 1-month and 2-month postoperative best corrected visual acuity, central corneal thickness (CCT) and endothelial cell count. ELISA and RT-PCR were performed for IL-1β, IL-6, VEGF and PGE2 preoperatively and at 1 week postoperatively.

RESULTS

The percentage increase in CCT in the microincision group was significantly higher than that in the small incision group at 1 week after cataract surgery (p = 0.01). The increase in macular thickness in the microincision group was significantly higher than that in small incision group at 1 month after cataract operation (p = 0.04). Also, IL-1β, IL-6, VEGF and PGE2 concentrations and their expression ratio in the microincision group were significantly higher than those in the small incision group at 1 week after cataract surgery compared to the preoperative period (p < 0.05).

CONCLUSIONS

Phacoemulsification with microincision coaxial cataract surgery may increase the macular thickness compared to phacoemulsification with small incision coaxial cataract surgery. Blood-aqueous barrier breakdown may occur more frequently after microincision cataract surgery than after small incision cataract surgery.

Time course of changes in aqueous flare intensity after vitrectomy for rhegmatogenous retinal detachment

PURPOSE

To investigate the time course of changes in aqueous flare intensity after vitrectomy for rhegmatogenous retinal detachment (RD) and to determine the clinical factors related to an increase in aqueous flare.

METHODS

The present study included 22 unilateral patients with RD undergoing primary 20-gauge vitrectomy. Aqueous flare intensity was measured preoperatively and at 1 week, 2 weeks, 1 month, and 3, 6, and 12 months postoperatively using the laser flare meter.

RESULTS

Before vitrectomy, aqueous flare intensity was significantly higher in eyes with RD than in contralateral normal eyes. Vitrectomy increased aqueous flare intensity, and the peak was observed at the first postoperative week. Aqueous flare intensity decreased to a stable level at 3 months postoperatively but remained significantly higher than that of contralateral and preoperative eyes throughout the observation period. Clinical factors that were found to be significantly correlated with an increase in aqueous flare intensity included 1) before the surgical procedure: extent of RD and intraocular pressure, and 2) 3 months postoperatively: size of retinal breaks, number of laser photocoagulation spots, operation time, and performance of combined cataract surgery. Multiple regression analysis revealed that aqueous flare intensity at 3 months postoperatively had significant correlation with the size of retinal breaks (P < 0.005) and the number of laser photocoagulation spots (P < 0.05).

CONCLUSION

Aqueous flare intensity after vitrectomy for RD decreased to a stable level at 3 months postoperatively but remained significantly higher than the normal level. The size of retinal breaks and the degree of surgical invasion were associated with the increase in aqueous flare.

Role of vascular endothelial growth factor in the breakdown of the blood-aqueous barrier after retinal laser photocoagulation in pigmented rabbits

PURPOSE

Retinal laser photocoagulation is used to treat a variety of retinal diseases. Breakdown of the blood-aqueous barrier has been noted after retinal laser photocoagulation. The effect of vascular endothelial growth factor (VEGF) on the function of the blood-aqueous barrier after retinal laser photocoagulation remains undetermined. The current study was designed to evaluate the relationship between intraocular levels of VEGF and breakdown of the blood-aqueous barrier after retinal laser photocoagulation in rabbits.

METHODS

Pigmented rabbits were treated with retinal laser photocoagulation in one eye; the other served as control. Laser flare photometry was carried out on post-treatment days 1, 3, 7, and 14. Animals were sacrificed at the time period just mentioned postlaser, the eyes were removed, and samples of vitreous and aqueous humor were collected. Intraocular VEGF levels were measured by using an immunoassay. An intravitreal injection of VEGF was administered, and the aqueous flare intensity and VEGF levels in the aqueous and vitreous humor were measured at the time periods just mentioned.

RESULTS

A significant increase in the aqueous flare intensity after retinal laser photocoagulation was noticed on postoperative day 1, with the values returning to baseline levels on day 14. The VEGF levels in the vitreous of the lasered eyes were significantly increased on day 1 compared with the nonlasered control eyes. The VEGF levels in the aqueous humor of the lasered eyes were also significantly increased on day 1 compared with the control eyes. An intravitreal injection of VEGF induced a significant increase in the aqueous flare intensity and VEGF levels in the aqueous and vitreous humor.

CONCLUSIONS

The current results suggested that retinal laser photocoagulation can produce a breakdown of the blood-aqueous barrier. VEGF may play a role in the blood-aqueous barrier dysfunction after retinal laser photocoagulation.

A role for photoreceptors in retinal oedema and angiogenesis: an additional explanation for laser treatment?

PURPOSE

To investigate the possible roles of retinal photoreceptors in macular oedema and retinal angiogenesis with particular reference to the mode of action of laser therapy.

METHODS

(i) Studies in rats made hypoxic for 2 h by administering an oxygen/nitrogen mixture of reduced oxygen content, and growth factors determined by RT-PCR, western blotting, and immunohistochemistry. Assessment of blood-retinal barrier integrity using fluorescent and electron-dense tracers. (ii) Studies in pigs with one retina made hypoxic by selective embolisation of the retinal capillary circulation with fluorescent microspheres. (iii) Assessment of laser therapy in selected cases of retinal neovascularisation indicating a role for photoreceptors.

RESULTS

In the hypoxic retina, angiogenic and vascular permeability factors such as vascular endothelial growth factor (VEGF), nitric oxide synthases (NOSs), and insulin-like growth factor-1 are upregulated in retinal astrocytes and Müller cells but are also present in large amount in the photoreceptors. Hypoxia-inducible factor-1 (HIF-1) is upregulated in retinal glial cells but not in the photoreceptors, suggesting that growth factors in the photoreceptors may not have been generated there. The tracer dye, rhodium isothiocyanate, leaking from an abnormally permeable inner blood-retinal barrier in the hypoxic retina accumulates in the photoreceptors.

CONCLUSIONS

The results indicate that laser treatment of macular oedema or retinal neovascularisation may obtain its effect not only by improving oxygen availability in the inner retina, but also by reducing the load of angiogenic/permeability factors that accumulate in the photoreceptors in hypoxic/ischaemic conditions.

Elevated intravitreal interleukin-6 levels in patients with proliferative diabetic retinopathy

BACKGROUND

We conducted this study to elucidate the possible role of interleukin-6 (IL-6) in the pathogenesis of proliferative diabetic retinopathy (PDR).

METHODS

Together with pertinent clinical and laboratory data, intravitreal and serum concentrations of IL-6 were determined in 8 patients with PDR by means of enzyme-linked immunosorbent assay (ELISA). The results were compared with data from 8 nondiabetic control subjects undergoing vitrectomy.

RESULTS

Significantly higher intravitreal IL-6 concentrations were found in patients with PDR (mean [SD], 755 [177] pg/mL) compared with control subjects (93 [151] pg/mL) (p = 0.001). The serum IL-6 levels in the PDR group were lower than the measurable threshold of the ELISA kit (<0.16 pg/mL). Diabetic patients with macular edema had a higher mean (SD) level of intravitreal IL-6 (896 [73] pg/mL) compared with patients without macular edema (613 [119] pg/mL) (Mann-Whitney U test, p = 0.03). Correlation analysis did not reveal any significant association between intravitreal IL-6 levels and patient age, duration of either diabetes mellitus or vitreous hemorrhage, panretinal photocoagulation, type of current medical therapy, hyperglycemia, or the biochemical indicators of renal function.

INTERPRETATION

IL-6, a proinflammatory cytokine, may have a role in PDR. Intraocular production of IL-6 appears to be responsible for the elevated intravitreal levels observed.

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

PURPOSE

To evaluate the influence of peripheral 360 degrees retinal cryocoagulation on the blood-aqueous barrier of patients with retinal vascular disorders.

METHODS

The aqueous of 50 eyes of 50 patients with diabetic retinopathy or central vein occlusion was measured by laser flare photometry (FC-2000, Kowa) before peripheral 360 degrees retinal cryocoagulation and 1 day, 1 week, and 1 month thereafter.

RESULTS

Mean aqueous flare values before treatment were 15.7 (+/-8.2) photon counts/ms; mean cell count was 9.8 (+/-14.8) cells/0.5 mm(3). One day after retinal cryocoagulation flare values had increased statistically significantly to a mean of 39.2 (+/-85.8) photon counts/ms, while the increase in mean cell number to 15.0 (+/-37.2) cells/0.5 mm(3) did not reach statistical significance. One week following treatment, mean flare values had dropped to 30.9 (+/-49.6) photon counts/ms and were no longer significantly elevated compared with baseline, while the mean cell count of 11.1 (+/-27.0) cells/0.5 mm(3) was now statistically significantly elevated compared with baseline. One month after treatment the flare values had decreased to a mean of 19.7 (+/-12.0) photon counts/ms, and mean cell count had decreased to 8.1 (+/-10.4) cells/0.5 mm(3); at this point neither parameter showed a statistically significant difference from baseline values.

CONCLUSION

Peripheral 360 degrees retinocryocoagulation does not lead to permanent disturbance of the blood-aqueous barrier.