Quantitative analysis of diabetic macular edema after scatter laser photocoagulation with the scanning retinal thickness analyzer

Structural and functional changes to the retina and optic nerve following panretinal photocoagulation over a 2-year time period

PurposeTo evaluate long-term structural and functional changes to the retina and optic nerve following panretinal photocoagulation (PRP) in diabetic retinopathy (DR) patients.MethodsParticipants were patients with DR requiring PRP and control patients with DR not requiring PRP. The Heidelberg retinal tomography (HRT) and optical coherence tomography (OCT) were performed to analyze the optic nerve and macula. Best-corrected visual acuity (BCVA) and visual field (VF) testing were done to measure central and peripheral vision. Wide-field fluorescein angiogram was performed to monitor the progression of diabetic ischemia. The primary outcome measure was to determine the degree of retinal and optic nerve changes before and after PRP.ResultsThere was a non-significant thickening of the macula and retinal nerve fiber layer at 6 months post laser that recovered by 24 months. Mean perfused ratio was significantly increased (P=0.02) at 12 and 24 months post laser. Independently grading patient stereophotographs, grader 1 indicated there was a non-significant increase in cup to disk ratio post laser, while grader 2 indicated a significant increase at 6 (P=0.04), 12 (P=0.02), and 24 months (P=0.005). There was a significant VF decrease (P≤0.02) at 12 and 24 months post laser with BCVA showing a non-significant trend of deteriorating results.ConclusionDespite an improvement in peripheral perfusion, there was a significant progressive decline of peripheral VF over the study period. Clinical grading of the optic nerve was more unreliable following PRP, despite the absence of significant morphological changes as detected by the OCT and HRT.

A randomized controlled trial of panretinal photocoagulation with and without intravitreal ranibizumab in treatment-naive eyes with non-high-risk proliferative diabetic retinopathy

PURPOSE

To compare the efficacy of panretinal photocoagulation (PRP) and intravitreal ranibizumab injection with PRP alone in patients with treatment-naive bilateral non-high-risk proliferative diabetic retinopathy.

METHODS

Sixty eyes of 30 patients were randomized either to the study group (SG) receiving PRP plus 2 ranibizumab injections or to the control group (CG) receiving PRP alone. Mean change in best-corrected visual acuity and in optical coherence tomography were compared at baseline and 1, 3, and 6 months.

RESULTS

Best-corrected visual acuity was significantly better at 6 months in the SG; however, there was decrease in best-corrected visual acuity in the CG. Central macula thickness decreased significantly at 6 months in SG when compared with baseline (-47.6 μm, P < 0.001) and did not reveal significant difference in the CG. In eyes with diabetic macular edema, best-corrected visual acuity increased by 3.6 letters (P = 0.06) in the SG and decreased by 4.4 letters in the CG (P = 0.003). Central macula thickness decreased by 69.3 μm (P = 0.001) in the SG and decreased by 45.5 μm (P = 0.11) in the CG.

CONCLUSION

Intravitreal ranibizumab in combination with PRP can be an effective treatment in eyes with non-high-risk proliferative diabetic retinopathy and diabetic macular edema.

Short pulse laser induces less inflammatory cytokines in the murine retina after laser photocoagulation

AIMS

The purpose of this study was to evaluate the effect of pulse duration on the expression of inflammatory cytokines in the murine retina after laser photocoagulation treatment with a PASCAL(®) pattern scan laser photocoagulator and conventional laser treatment.

METHODS

Retinal scatter laser photocoagulation was performed on C57BL/6J mice using a short pulse (10 ms) with a PASCAL laser or conventional settings (100 ms) with a multicolor laser. Eyes were enucleated before treatment (control) and 1 day, 3 days and 7 days after treatment. The levels of inflammatory cytokines (i.e., VEGF, MCP-1, RANTES and IL-6) in the retina/choroid were quantified by an ELISA. The expression patterns of VEGF and macrophages (i.e., F4/80) in the retina/choroid were evaluated by immunohistochemistry.

RESULTS

The levels of RANTES, IL-6 and MCP-1 after PASCAL and conventional laser treatments were significantly elevated compared with controls (p < 0.05). Conventional laser treatment, but not PASCAL treatment, resulted in the up-regulation of VEGF. RANTES and IL-6 levels on day 1 and MCP-1 levels on day 3 in the sensory retina were also significantly up-regulated with conventional laser treatment compared with PASCAL treatment (p < 0.05). Immunohistochemical analysis showed that PASCAL treatment was associated with lower VEGF and F4/80 expression levels compared with conventional laser treatment.

CONCLUSIONS

Our data suggested that the short pulse duration induced fewer inflammatory cytokines in the sensory retina compared with the conventional pulse duration. Short pulse laser photocoagulation with the PASCAL may prevent macular edema after panretinal photocoagulation.

Changes of choroidal thickness after treatment for diabetic retinopathy

PURPOSE

To investigate the choroidal thickness changes after intravitreal bevacizumab injection (IVB), panretinal photocoagulation (PRP) or both for diabetic retinopathy treatment.

MATERIALS AND METHODS

The study included 31 eyes (31 patients) in the IVB group, 35 eyes (35 patients) in the PRP group and 35 eyes (35 patients) in the IVB-PRP group. Enhanced depth imaging optical coherence tomography (EDI-OCT) was performed before and 1 month after each treatment to measure subfoveal and extrafoveal (500 and 1000 μm) choroidal thicknesses. The best-corrected visual acuity (BCVA) and central macular thickness (CMT) were also measured.

RESULTS

The choroidal thickness at all locations significantly decreased after treatment in all groups, but there was no significant difference in the amount of change among the three groups. The subfoveal choroidal thickness and CMT significantly decreased after treatment in the IVB and IVB-PRP groups. In the PRP group, the CMT significantly increased, while the choroidal thickness significantly decreased after treatment. The subfoveal choroidal thickness and CMT were significantly reduced after IVB, but there was no significant correlation between their changes. The BCVA was improved significantly in the IVB and IVB-PRP group, but not in the PRP group.

CONCLUSIONS

The choroidal thickness decreased after all treatments, suggesting that IVB or PRP rapidly reduced choroidal vascular permeability.

Intravitreal bevacizumab in the treatment of diabetic ocular neovascularization

PURPOSE

To evaluate the efficacy of intravitreal bevacizumab for treating diabetic retinal and/or iris neovascularization.

METHODS

Consecutive, prospective, interventional case series study of 60 eyes with diabetic retinal and/or iris neovascularization. Patients had a complete ocular examination before receiving 1.25 mg (0.05 mL) of intravitreal bevacizumab. Abnormal new vessels elsewhere in the retina, optic disk, or iris were graded by size and associated hemorrhage or glaucoma. Patients had complete postinjection ophthalmic evaluations with regrading of the abnormal new vessels at 3 months and 6 months. The main outcome measures included clinical partial or total regression of abnormal new vessels, changes in visual acuity, and complications related to the intravitreal injections.

RESULTS

Twenty-six patients (47.3%) were men (mean age, 59 years). Abnormal new vessel regression at 6 months occurred in 65% of new vessels of the iris (P = 0.001), 45% of new vessels of the optic disk (P = 0.009), and 43% of new vessels elsewhere (P = 0.008). The visual acuity improved in 20% of eyes, which was not significant (P = 0.235); the visual acuity deteriorated in 23% of eyes (P = 0.163). No systemic or ocular side effects developed except for postinjection hypotony in one eye.

CONCLUSION

Intravitreal bevacizumab is a well-tolerated medication that causes regression of abnormal diabetic neovascularization. New vessels of the iris responded more than new vessels of the optic disk and new vessels elsewhere.

Retinal function and morphology of severe non-proliferative diabetic retinopathy before and after retinal photocoagulation

PURPOSE

The purpose of this project was to investigate the changes in macular function and macular morphology of severe non-proliferative diabetic retinopathy (NPDR), due to photocoagulation, using the multifocal electroretinogram (mfERG) and optical coherence tomography (OCT).

METHODS

Thirty-five volunteers were in the control group, with one eye per person examined with the mfERG. Both the mfERG and OCT were conducted on 30 patients with diabetes who had severe NPDR before, and two, seven and 14 days after, treatment with photocoagulation.

RESULTS

Compared with the control group, the P1 and N1 response densities in the patients with NPDR appeared to decrease significantly at rings 2-3 and rings 3-4, respectively, whereas no difference was seen in the implicit times. At two days after photocoagulation, the P1 and N1 response densities decreased significantly in ring 1 and they were still lower than the pre-photocoagulation values at 14 days after photocoagulation. In addition, no change was found in the implicit times before and after photocoagulation. There was no obvious difference in the macular thickness after treatment. At two days after treatment, the P1 response density in ring 1 negatively correlated with the corresponding macular thickness.

CONCLUSION

The para-macular function was significantly impaired in those patients with severe NPDR and photocoagulation reduced the central macular function. Even after 14 days, the central macular function had not returned to pre-photocoagulation levels.

Intravitreal Bevacizumab (Avastin) for Diabetic Retinopathy: The 2010 GLADAOF Lecture

This paper demonstrates multiple benefits of intravitreal bevacizumab (IVB) on diabetic retinopathy (DR) including diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR) at 24 months of followup. This is a retrospective multicenter interventional comparative case series of intravitreal injections of 1.25 or 2.5 mg of bevacizumab for DME, PDR without tractional retinal detachment (TRD), and patients who experienced the development or progression of TRD after an intravitreal injection of 1.25 or 2.5 mg of bevacizumab before vitrectomy for the management of PDR. The results indicate that IVB injections may have a beneficial effect on macular thickness and visual acuity (VA) in diffuse DME. Therefore, in the future this new therapy could complement focal/grid laser photocoagulation in DME. In PDR, this new option could be an adjuvant agent to panretina photocoagulation so that more selective therapy may be applied. Finally, TRD in PDR may occur or progress after IVB used as an adjuvant to vitrectomy. Surgery should be performed 4 days after IVB. Most patients had poorly controlled diabetes mellitus associated with elevated HbA1c, insulin administration, PDR refractory to panretinal photocoagulation, and longer time between IVB and vitrectomy.

Evaluation of the aldose reductase inhibitor fidarestat on ischemia-reperfusion injury in rat retina

This study evaluated the effects of retinal ischemia-reperfusion (IR) injury and pre-treatment with the potent and specific aldose reductase inhibitor fidarestat on apoptosis, aldose reductase and sorbitol dehydrogenase expression, sorbitol pathway intermediate concentrations, and oxidative-nitrosative stress. Female Wistar rats were pre-treated with either vehicle (N-methyl-D-glucamine) or fidarestat, 32 mg kg(-1) d(-1) for both, in the right jugular vein, for 3 consecutive days. A group of vehicle- and fidarestat-treated rats were subjected to 45-min retinal ischemia followed by 24-h reperfusion. Ischemia was induced 30 min after the last vehicle or fidarestat administration. Retinal IR resulted in a remarkable increase in retinal cell death. The number of TUNEL-positive nuclei increased 48-fold in the IR group compared with non-ischemic controls (p<0.01), and this increase was partially prevented by fidarestat. AR expression (Western blot analysis) increased by 19% in the IR group (p<0.05), and this increase was prevented by fidarestat. Sorbitol dehydrogenase and nitrated protein expressions were similar among all experimental groups. Retinal sorbitol concentrations tended to increase in the IR group but the difference with non-ischemic controls did not achieve statistical significance (p=0.08). Retinal fructose concentrations were 2.2-fold greater in the IR group than in the non-ischemic controls (p<0.05). Fidarestat pre-treatment of rats subjected to IR reduced retinal sorbitol concentration to the levels in non-ischemic controls. Retinal fructose concentrations were reduced by 41% in fidarestat-pre-treated IR group vs. untreated ischemic controls (p=0.0517), but remained 30% higher than in the non-ischemic control group. In conclusion, IR injury to rat retina is associated with a dramatic increase in cell death, elevated AR expression and sorbitol pathway intermediate accumulation. These changes were prevented or alleviated by the AR inhibitor fidarestat. The results identify AR as an important therapeutic target for diseases involving IR injury, and provide the rationale for development of fidarestat and other AR inhibitors.

Combined laser and intravitreal triamcinolone for proliferative diabetic retinopathy and macular edema: one-year results of a randomized clinical trial

PURPOSE

To evaluate laser combined with intravitreal triamcinolone acetonide (IVTA) for the management of patients with proliferative diabetic retinopathy (PDR) and clinically significant macular edema (CSME).

DESIGN

Randomized clinical trial.

METHODS

settings: Single center. study population: Twenty-two patients with bilateral treatment-naïve moderate PDR and CSME. intervention: Laser (panretinal and macular) photocoagulation was performed in each eye, followed by IVTA in one randomly assigned eye. Best-corrected visual acuity (BCVA), fundus photography, and optical coherence tomography were performed at baseline and at months 1, 3, 6, 9, and 12. main outcome measures: Changes in BCVA, central macular thickness (CMT), and total macular volume (TMV).

RESULTS

The mean logarithm of the minimal angle of resolution (logMAR) BCVA improved significantly, and mean CMT and TMV were significantly reduced in the IVTA group compared with the laser-only group (controls) at all study follow-up visits (P < .001). The mean logMAR BCVA (Snellen equivalent) was 0.44 (20/50(-2)) for the IVTA group and 0.38 (20/50(+1)) for the controls at baseline, and 0.12 (20/25(-1)) for the IVTA group and 0.32 (20/40(-1)) for the controls at 12 months (P < .001). The mean CMT and TMV were, respectively, 360 microm and 8.59 mm(3) for the IVTA group and 331 microm and 8.44 mm(3) for the controls at baseline, and 236 microm and 7.32 mm(3) for the IVTA group and 266 microm and 7.78 mm(3) for the controls at 12 months (P < .001).

CONCLUSIONS

The combination of laser photocoagulation with IVTA was associated with improved BCVA and decreased CMT and TMV when compared with laser photocoagulation alone for the treatment of moderate PDR with CSME.

Intravitreal bevacizumab (Avastin) for proliferative diabetic retinopathy: 6-months follow-up

AIMS

To study the effects of intravitreal bevacizumab (Avastin) on retinal neovascularization (RN) in patients with proliferative diabetic retinopathy (PDR).

METHODS

Retrospective study of patients with RN due to PDR who were treated with at least one intravitreal injection of 1.25 or 2.5 mg of bevacizumab. Patients underwent ETDRS best-corrected visual acuity (BCVA) testing, ophthalmoscopic examination, optical coherence tomography (OCT), and fluorescein angiography (FA) at baseline and follow-up visits.

RESULTS

Forty-four eyes of 33 patients with PDR and a mean age of 57.2-years (range: 23-82 years) participated in the study. Thirty-three eyes (75%) had previous panretinal photocoagulation (PRP). Twenty-seven eyes (61.4%) showed total regression of RN on fundus examination with absence of fluorescein leakage, 15 eyes (34.1%) demonstrated partial regression of RN on fundus examination and FA. Follow-up had a mean of 28.4 weeks (range from 24 to 40 weeks). BCVA and OCT demonstrated improvement (P<0.0001). Three eyes without previous PRP ('naive' eyes) and with vitreous haemorrhage have avoided vitreo-retinal surgery. One eye (2.2%) had PDR progression to tractional retinal detachment requiring vitrectomy, and one eye (2.2%) had vitreous haemorrhage with increased intraocular pressure (ghost cell glaucoma). No systemic adverse events were observed.

CONCLUSIONS

Intravitreal bevacizumab resulted in marked regression of RN in patients with PDR and previous PRP, and rapid resolution of vitreous haemorrhage in three naive eyes. Six-months results of intravitreal bevacizumab at doses of 1.25 or 2.5 mg in patients with PDR do not reveal any safety concerns.

Posterior pole retinal thickness measurements by the retinal thickness analyzer in healthy Chinese subjects

PURPOSE

To assess retinal thickness at the posterior pole in healthy Chinese subjects with the retinal thickness analyzer (RTA).

METHODS

Retinal thicknesses at the posterior pole and fovea were measured by the RTA in 331 eyes of 178 healthy Chinese subjects. Retinal thicknesses as a function of sex, age, refractive errors, and axial length were also evaluated.

RESULTS

The average thickness of the foveal area +/- SD was 158.6 +/- 24.8 microm, the average thickness of the perifoveal region (600-2,500 microm from fovea) +/- SD was 174 +/- 25.2 microm, and the average thickness of the posterior pole region (600-6,000 microm from fovea) +/- SD was 171.9 +/- 25.3 microm. There was no significant difference in retinal thicknesses of the foveal, perifoveal, and posterior pole regions in either right or left eyes or as a function of different spherical equivalents. Moreover, there was no significant difference of foveal thickness between males and females. Greater retinal thicknesses of the foveal, perifoveal, and posterior pole regions were associated with age of older than 40 years and axial length of < 24 mm, and greater perifoveal and posterior pole thicknesses were found for females. Furthermore, there were no significant correlations between age, refractive errors, and axial lengths with retinal thicknesses.

CONCLUSION

Retinal thicknesses of the posterior pole region differed by age, axial length, and sex, but there was no effect of laterality or different spherical equivalents. The RTA is a fast and noninvasive technology to assess retinal conditions with thickening or thinning in the fovea and posterior pole.

Diagnostic accuracy of the Retinal Thickness Analyser: differentiation between normal eyes and eyes with glaucoma or macular pathologies

BACKGROUND

The Retinal Thickness Analyser (RTA) is intended to detect glaucomatous changes as well as macular pathologies at the posterior pole. We determined the diagnostic accuracy for eyes with manifest glaucoma or macular diseases.

METHODS

We examined 71 eyes with long-term, established eye conditions. Included were 28 eyes with glaucoma, 21 with different macular diseases and 22 normal eyes. All examinations were evaluated in a blind-test by RTA experts without any clinical information on the patients. After comparison of the RTA interpretation with the clinical diagnosis, we determined sensitivity, specificity, positive and negative predictive values.

RESULTS

Of 71 examinations, 15 (21%) were not interpretable. If these results are excluded, the following diagnostic accuracy values were calculated for glaucoma and macular disorders respectively: sensitivity 75 and 59%, specificity 55 and 97%, positive predictive value 48 and 90% and negative predictive value 80 and 84%. These values were not significantly different when both eyes of each patient were included in the final analysis (n=133).

CONCLUSION

The diagnostic values of the RTA determined in this case control study were not satisfactory. However, no clinical information was used in the assessment. The extent to which additional clinical information increases the diagnostic value remains to be determined.

Macular function assessed with mfERG before and after panretinal photocoagulation in patients with proliferative diabetic retinopathy

PURPOSE

To examine macular function and its correlation to macular thickness before and after panretinal photocoagulation for proliferative retinopathy in diabetic patients.

METHODS

Ten diabetic patients (aged 57 +/- 10 years, diabetes duration 21 +/- 10 years) treated with panretinal photocoagulation outside the great vascular arcade underwent multifocal electroretinography (mfERG) and optical coherence tomography (OCT) before and 6 months after treatment. When focal treatment in the macular region was performed prior to panretinal photocoagulation the investigations took place 3 weeks after this treatment but before the panretinal photocoagulation. One eye per patient was examined. Amplitudes and implicit times of the mfERG response were analyzed within the four innermost (27 degrees) of the six concentric rings registered by the mfERG, which corresponds to the area measured by the OCT (psi 3.5 mm).

RESULTS

Visual acuity was similar before and after photocoagulation, 1.0; 0.7-1.0 (md, range) versus 1.0; 0.6-1.0 (md, range). The mean values of the ring average amplitudes were reduced in the first and second, third and fourth concentric rings from foveola after photocoagulation, p = 0.001, p = 0.011 and p = 0.004, respectively. No change was seen in implicit time after treatment. OCT values were similar before and after photocoagulation. There was no correlation between retinal thickness assessed with OCT and amplitudes measured by the mfERG.

CONCLUSION

In spite of unchanged values of retinal thickness and visual acuity, panretinal photocoagulation seems to cause a functional impairment in the adjacent untreated macula, shown by reduced amplitudes measured by the mfERG.

Eccentricity and measurement variability and repeatability with the retinal thickness analyser

AIMS

To define the variability and repeatability of retinal thickness measurements using the retinal thickness analyser (RTA) and to elucidate any interaction between eccentricity (that is, position relative to the fovea) and variability and repeatability.

METHODS

The sample comprised 20 normal subjects of mean age 33 years. Each subject attended for two visits. Repeated RTA scans were acquired centred on the fovea and for any one of the four possible non-foveal scan areas. The mean retinal thickness (+SD) was calculated for a series of concentric circular bands centred on fixation. A repeated measures analysis of variance (ANOVA) was used to determine any significant interaction between the variability of RTA thickness values and eccentricity.

RESULTS

The group mean coefficient of variation and coefficient of repeatability were highest at the fovea. The repeated measures ANOVA revealed that the within test variability of RTA measurements varied significantly with eccentricity (p<0.0001). Similarly, the between test repeatability varied significantly with eccentricity (p = 0.045).

CONCLUSION

The significantly elevated within test variability and between test repeatability in the foveal area need to be considered when using the RTA to evaluate patients with macular disease.

Retinal thickness analysis(RTA): an objective method to assess and quantify the retinal thickness in healthy controls and in diabetics without diabetic retinopathy

BACKGROUND

Since it has been shown that photocoagulation is indicated in patients with diabetic macular edema, quantitative and objective assessment of retinal thickness is of clinical importance.

METHODS

A laser slit beam was projected on the retina and scanned across a 2 x 2 mm retinal area in 200 msec. Nine type 1 and 2 diabetic patients without funduscopically and photographically visible diabetic retinopathy and 10 healthy controls were scanned with the RTA. The intraindividual and interindividual variabilities of the RTA were determined.

RESULTS

The intraindividual and interindividual variability was 5 microm and 15 microm, respectively. The mean value of the mean foveal thickness (MFT) and perifoveal retinal thickness (PFT) in the 10 healthy controls was 152 +/- 15 microm and 175 +/- 14 microm, respectively, and 181 +/- 26 microm and 191 +/- 27 microm, respectively, in the group of nine diabetics without signs of diabetic retinopathy. The MFT in the group of diabetic patients was significantly (P < 0.001) larger than in the control groups.

CONCLUSION

Retinal thickness in diabetic patients without diabetic retinopathy was increased in all measurements in comparison with the findings in healthy subjects. Retinal thickness measurements with the RTA could possibly detect early signs of diabetic retinopathy before funduscopic and photographic signs are visible and may be helpful in guiding treatment.

Diabetic macular oedema: the effect of photocoagulation on fluorescein transport across the blood-retinal barrier

BACKGROUND/AIM

The visual loss secondary to diabetic macular oedema can be controlled to some extent by photocoagulation, though the mechanism of action is largely unknown. The purpose of the present study was to quantitate the effect of photocoagulation on the blood-retinal barrier using fluorescein as a tracer of passive and active transport.

METHODS

A prospective study of 46 eyes in 34 patients with clinically significant macular oedema (CSMO) examined by vitreous fluorometry before and 6 months after macular photocoagulation treatment.

RESULTS

In 23 eyes CSMO was not present at follow up (responding eyes), in another 23 other eyes CSMO was still present (non-responding eyes). With reference to the presence or absence of CSMO at follow up, the passive transport (permeability) for responding eyes decreased after photocoagulation in contrast with an increase in non-responding eyes; the difference between the groups at follow up was significant (p=0.03). The active transport for responding eyes decreased slightly at follow up, while it increased for non-responding eyes; the difference between the groups at follow up was not significant (p=0.09).

CONCLUSION

Following photocoagulation a reduction of diabetic macular oedema, defined as disappearance of CSMO, is paralleled by a decrease of the passive permeability while the hypothesis of an increase in the active transport from the retina to the blood could not be supported by this study.

Comparison of foveal thickness measured with the retinal thickness analyzer and optical coherence tomography

PURPOSE

To assess and compare the reliability and reproducibility of retinal thickness measurements for the retinal thickness analyzer (RTA) and optical coherence tomography (OCT) in normal and edematous retina.

METHODS

The authors measured the foveal thickness of 21 normal eyes and 9 eyes with macular edema with both methods in random order. With the RTA, the fovea was measured 10 times; with the OCT, six scans (one horizontal and five vertical cross-sections) of the fovea were obtained.

RESULTS

Mean foveal thickness of normal eyes measured 153 microm with OCT and 181 microm with RTA (median for both methods 150 microm). Coefficients of variation (CV) within the same subjects were 10% (OCT) and 9% (RTA) reducing to 9% (OCT) and 7% (RTA) when scans were repeated only five times for both methods. The RTA, however, yielded an interpatient CV of 33% (OCT 17%), which was caused by several falsely high readings in normal individuals. In eyes with retinal thickening the OCT measured a mean of 324 microm with 15% intra- and 58% interpatient CV. The RTA yielded a mean of 403 microm with CV of 18% and 73%, respectively.

CONCLUSION

Both methods yield reproducible measurements of foveal thickness in normal individuals and individuals with macular edema. However, falsely high measurements may occur with the RTA, reducing its reliability as compared to the OCT.

A quantitative in vivo study of retinal thickness before and after laser treatment for macular edema due to retinal vein occlusion

PURPOSE

To evaluate quantitatively the effect of grid laser photocoagulation in macular edema due to central and branch retinal vein occlusion, using the retinal thickness analyzer.

METHODS

Five patients with cystoid and non-cystoid macular edema were studied before and after argon grid laser treatment. All were examined clinically, with fluorescein angiography, and measurement of retinal thickness. Macular thickness was correlated to visual acuity measured on the ETDRS chart.

RESULTS

Laser-slit images obtained with the retinal thickness analyzer in patients with macular edema disclosed discrete intraretinal changes after photocoagulation. Biomicroscopy and fluorescein angiography were insensitive to these small changes in the retinal thickness. No patient had any change in visual acuity after three months, but the retinal thickness was greater at this interval. The retinal thickening may be explained by a postoperative inflammatory response or by altered retinal blood flow or, in two of the eyes, by the effect of combined peripheral photocoagulation.

CONCLUSIONS

The retinal thickness analyzer offers a refined tool for the diagnosis of subclinical changes of macular edema in retinal vein occlusion and is therefore also useful for assessing the effects of treatment.

Perifoveal microcirculation before and after vitrectomy for diabetic cystoid macular edema

PURPOSE

To quantify the perifoveal microcirculation in diabetic eyes before and after successful vitreous surgery for cystoid macular edema without posterior vitreous detachment, and to determine whether improvement in perifoveal microcirculation is associated with improvement in postoperative visual acuity.

METHODS

In a prospective study, vitreous surgery was performed on 11 eyes of nine consecutive diabetic patients with cystoid macular edema, and their mean perifoveal capillary blood flow velocity was measured by fluorescein angiography with a scanning laser ophthalmoscope. Visual acuity was measured preoperatively and postoperatively, and the results were converted to the logarithm of the minimum angle of resolution (logMAR). The correlation between changes in logMAR visual acuity and capillary blood flow velocity was evaluated.

RESULTS

In all nine eyes of seven patients with successful vitreous surgery, the cystoid macular edema resolved within 6 months after surgery, and the mean capillary blood flow velocity was significantly increased compared with that before surgery (2.19 mm per second versus 2.68 mm per second, P =.021); the changes in capillary blood flow velocity were significantly correlated with the changes in the logMAR visual acuity (P =.024).

CONCLUSIONS

Vitreous surgery may improve perifoveal microcirculation in the eyes of diabetic patients with cystoid macular edema and resolve the macular edema. Improvement of perifoveal microcirculation may be an important factor affecting visual outcome.

Cystoid macular edema following cataract surgery

Cystoid macular edema (CME) remains a troublesome problem after cataract surgery and other types of ocular surgical procedures. It is recognized as the most frequent cause of decreased vision in patients following cataract surgery. Although the disease was first described more than 40 years ago, its cause is unclear, and all available therapeutic interventions, mainly based on theories regarding the pathogenesis of the condition, are of doubtful effectiveness and are still far from being satisfactory. Most published literature on the incidence and treatment of CME consists of small, retrospective case series and cannot provide reliable answers as to whether a given factor or intervention is associated with the occurrence or outcome of the disease.