The effect on the macular function of laser photocoagulation for diabetic macular edema

Association Between Contrast Sensitivity and Central Subfield Thickness in Center-Involving Diabetic Macular Edema

Purpose: To evaluate the association between contrast sensitivity (CS) and central subfield thickness (CST) in diabetic macular edema (DME). Methods: This prospectively recruited, cross-sectional study included eyes with DME evaluated from November 2018 to March 2021. CST was measured using spectral-domain optical coherence tomography on the same day as CS testing. Only eyes with center-involving DME (CST >305 µm for women; >320 µm for men) were included. CS was evaluated using the quantitative CS function (qCSF) test. Outcomes included visual acuity (VA) and the following qCSF metrics: area under the log CS function, contrast acuity (CA), and CS thresholds at 1 to 18 cycles per degree (cpd). Pearson correlation and mixed-effects regression analyses were performed. Results: The cohort included 52 eyes of 43 patients. Pearson correlation analysis showed a stronger association between CST and CS thresholds at 6 cpd (r = -0.422, P = 0.002) than CST and VA (r = 0.293, P = 0.035). Mixed-effects univariate and multivariate regression analyses showed significant associations between CST and CA (β = -0.001, P = .030), CS at 6 cpd (β = -0.002, P = .008), and CS at 12 cpd (β = -0.001, P = .049) but no significant associations between CST and VA. Among the visual function metrics, the effect size of CST was largest on CS at 6 cpd (βStandardized = -0.37, P = .008). Conclusions: In patients with DME, CS may be more strongly associated with CST than VA. Including CS as an adjunct visual function outcome measure in eyes with DME may prove clinically valuable.

FUNCTIONAL AND STRUCTURAL EFFECTS OF NONDAMAGING RETINAL LASER THERAPY FOR MACULAR TELANGIECTASIA TYPE 2: A Randomized Sham-Controlled Clinical Trial

PURPOSE

Macular telangiectasia (MacTel) Type 2 is a progressing neurovascular disease of the macula, currently lacking effective treatment. This study assessed the effect of nondamaging retinal laser therapy (NRT) compared with sham.

METHODS

Twelve MacTel patients were enrolled in this double-masked, controlled, randomized clinical trial. For the nine patients with both eyes eligible, one eye was randomized to NRT or sham and the other received alternate treatment. For three patients with only one eye eligible, that eye was randomly assigned either NRT or sham. Ellipsoid zone disruption, best-corrected visual acuity, and macular automated perimetry at 12 months served as structural and functional measures.

RESULTS

Eleven eyes were randomized to sham and 10 to NRT. Baseline best-corrected visual acuity was 66 letters (20/50) for sham and 72 letters (20/40) for NRT (P = 0.245). Ellipsoid zone disruption area was 298 µm2 in sham and 368 µm2 in NRT (P = 0.391). At 12 months, ellipsoid zone disruption increased by 24% in sham and decreased by 34% in NRT (P < 0.001). Best-corrected visual acuity measures remained stable during follow-up compared with baseline. At 1 year, the mean macular sensitivity was 28 dB in the NRT group, compared with 26 dB in sham.

CONCLUSION

Nondamaging retinal laser therapy was safe and well tolerated in patients with MacTel and resulted in structural and functional improvements, which could represent a protective effect of laser-induced hyperthermia. Longer follow-up and larger number of patients should help corroborate these effects.

Correlation between anterior chamber flare changes and diabetic macular edema after intravitreal injection of ranibizumab and aflibercept

PURPOSE

To evaluate aqueous flare change patterns following anti-vascular endothelial growth factor therapy for diabetic macular edema (DME) and investigate the relationship between changes in flare values and central macular thickness (CMT).

STUDY DESIGN

Retrospective, interventional case series METHODS: A total of 84 eyes of 62 patients with DME received either intravitreal ranibizumab (IVR; n = 62) or aflibercept (IVA; n = 22). A laser flare photometer (Kowa FM500, Kowa Company, Ltd) was used to measure flare values, and CMT was assessed using optical coherence tomography. Flare values and CMT were measured prior to injection (baseline) and at, 1, 7 and 14 days after injection.

RESULTS

Flare values in the IVR group decreased significantly at day 14 (P = 0.001), whereas the IVA group showed a significant increase in flare values at day 1 (P < 0.001). In the IVA group, the baseline flare values were significantly higher in the CMT reduction group than in the non-CMT reduction group (P = 0.035). There was no correlation between changes in flare values and CMT either in the IVA or IVR group.

CONCLUSIONS

Flare value changes in patients treated with IVR decreased at day 14 post-injection. This may indicate when the most anti-inflammatory effect was obtained. There was no correlation between changes in flare values and CMT either in the IVA or IVR group; nevertheless, our research suggests that the baseline flare value is a predictive factor for the efficacy of IVA in DME.

Sublethal Photothermal Stimulation with a Micropulse Laser Induces Heat Shock Protein Expression in ARPE-19 Cells

Purpose/Aim of the Study. Subthreshold micropulse diode laser photocoagulation is an effective treatment for macular edema. The molecular mechanisms underlying treatment success are poorly understood. Therefore, we investigated the effects of sublethal laser energy doses on a single layer of densely cultured ARPE-19 cells as a model of the human retinal pigment epithelium (RPE). Materials and Methods. A single layer of densely cultured human ARPE-19 cells was perpendicularly irradiated with a micropulse diode laser. Nonirradiated cells served as controls. Sublethal laser energy was applied to form a photocoagulation-like area in the cultured cell layers. Hsp70 expression was evaluated using quantitative polymerase chain reaction and immunocytochemistry. Results. Photocoagulation-like areas were successfully created in cultured ARPE-19 cell layers using sublethal laser energy with our laser irradiation system. Hsp70 mRNA expression in cell layers was induced within 30 min of laser irradiation, peaking at 3 h after irradiation. This increase was dependent on the number of laser pulses. Hsp70 upregulation was not observed in untreated cell layers. Immunostaining indicated that Hsp70 expression occurred concentrically around laser irradiation sites and persisted for 24 h following irradiation. Conclusion. Sublethal photothermal stimulation with a micropulse laser may facilitate Hsp70 expression in the RPE without inducing cellular damage.

Evaluation of the New "SAVE" Protocol in Diabetic Macular Edema Over the Course of Anti-VEGF Treatment

BACKGROUND

To evaluate a recently established grading protocol for diabetic macular edema (DME) over the course of intravitreal anti-VEGF treatment with ranibizumab.

METHODS

Fluorescein angiography images and optical coherence tomography scans before treatment and after 3 monthly applied intravitreal ranibizumab injections were retrospectively graded for each included study eye according to the recently introduced "SAVE" grading protocol ("S"= subretinal fluid; "A"= "area of retinal thickening"; "V"="vitreo-retinal abnormalities"; "E"="etiology of leakage focal versus non-focal") and correlated with best-corrected visual acuity (BCVA) in letters (lett).

RESULTS

Five of the 39 included study eyes had subretinal fluid ("S") before treatment which resolved during treatment. BCVA of study eyes with an initial retinal thickening smaller than one disc diameter ("A") was non-significantly higher compared to patients with a retinal thickening greater than one disc diameter (34.0 ± 17.9 lett versus 25.3 ± 13.3 lett, p=0.236) but became significant during treatment (40.5 ± 10.0 lett versus 28.3 ± 13.1 lett, p=0.004). No difference in BCVA was observed between patients with or without vitreo-retinal abnormalities ("V") before and during therapy. BCVA in patients with focal leakage ("E") was significantly higher than in patients with non-focal leakage before (33.1 ± 12.3 lett versus 23.3 ± 13.3 lett, p=0.017) and during (38.9 ± 10.9 lett versus 26.3 ± 12.6 lett, p=0.002) therapy.

CONCLUSIONS

Applying the grading protocol "SAVE", focal leakage ("E") was the only retrospectively observed parameter which significantly correlated with a better BCVA before therapy and over the course of treatment in patients with fovea-involving DME.

Subthreshold micropulse diode laser photocoagulation for diabetic macular edema in Japanese patients

PURPOSE

To assess the efficacy and safety of subthreshold micropulse diode laser photocoagulation for diabetic macular edema (ME).

DESIGN

Prospective, nonrandomized interventional case series.

METHODS

SETTING

Institutional.

PATIENTS

Thirty-six consecutive diabetic patients (43 eyes) with clinically significant ME and a central macular thickness (CMT) <600 microm by optical coherence tomography.

OBSERVATION PROCEDURES

Subthreshold micropulse diode laser photocoagulation was done with a 15% duty cycle (0.2 to 0.3 sec; 200 microm) at 50% to 90% of the burn threshold energy. The treated area was monitored on color images for 12 months.

MAIN OUTCOME MEASURES

CMT, best-corrected visual acuity (BCVA), and total macular volume at 3 months.

RESULTS

After 3 months, there was a significant reduction of CMT (P = .05, paired t test), but the changes of BCVA and macular volume were not significant. The preoperative CMT, BCVA (logarithm of the minimal angle of resolution; logMAR), and macular volume were 341.8 +/- 119.0 microm, 0.12 +/- 0.20, and 8.763 +/- 1.605 mm(3) respectively, vs 300.7 +/- 124.1 microm, 0.12 +/- 0.21, and 8.636 +/- 1.408 mm(3) at 3 months. CMT decreased significantly from 1 month (P = .015, Friedman test). Visual acuity was improved or maintained within 0.2 logMAR for 12 months in 94.7% of the patients. No obvious laser scars were detected in any patient.

CONCLUSIONS

In patients with moderate diabetic ME, subthreshold micropulse diode laser photocoagulation controls ME and maintains visual acuity with minimal retinal damage. These findings confirm the efficacy of this method for Japanese patients.

Protein kinase C expression in the rabbit retina after laser photocoagulation

BACKGROUND

Laser photocoagulation is a well-established treatment for diabetic retinopathy but the mechanism behind its effectiveness has not been elucidated. The protein kinase C (PKC) family is a group of enzymes which has been the subject of extensive interest in clinically related research since the advent of its role in the pathogenesis of diabetic retinopathy. With this study we wanted to explore whether PKC expression is altered in the retina after laser photocoagulation.

METHODS

Normal rabbit eyes were treated with laser photocoagulation of varying intensity and examined after 30 min to 7 weeks. Treated and untreated regions of the retina were investigated histologically with the MC5 monoclonal antibody against PKC. Labeling for glial fibrillary acidic protein (GFAP), as well as hematoxylin and eosin (H&E) staining was also performed to assess the laser-induced trauma.

RESULTS

In the normal retina, the MC5 antibody labeled rod bipolar cells and photoreceptor outer segments corresponding to PKC alpha. A translocated PKC expression with labeling concentrated in the rod bipolar terminals was seen in specimens examined 30 min after laser treatment, and after 1 week, no expression was seen in any part of the retina. After 2 weeks, PKC expression again indicated a translocated labeling pattern. After 5 weeks, labeling was found only in rod bipolar terminals in the peripheral retina. When comparing high- and low-intensity laser treatment 7 weeks postoperatively, no labeling was found in the high intensity-treated retinas, whereas low intensity-treated eyes displayed a near-normal labeling pattern. H&E staining revealed focal neuroretinal edema immediately after laser treatment, also in untreated areas. At later stages, destruction of the outer nuclear layer and migration of pigment epithelial cells in laser-lesioned areas was seen. GFAP-labeled Müller cells were seen 1 week postoperatively in the entire retina. Labeling after this time decreased, but was still present in laser spots after 5 and 7 weeks.

CONCLUSIONS

Laser photocoagulation alters the expression of PKC in the entire normal rabbit retina. The response follows a temporal pattern and is also related to laser intensity. These findings may help to explain the high efficacy of laser treatment in diabetic retinopathy.

Contrast sensitivity following focal laser photocoagulation in clinically significant macular oedema due to diabetic retinopathy

PURPOSE

To evaluate the influence of focal aser photocoagulation on contrast sensitivity in diabetic patients with clinically significant macular oedema (CSMO).

METHODS

A prospective non-comparative interventional study was performed on a group of patients with CSMO at Dr Rajendra Prasad Centre for Ophthalmic Sciences, New Delhi, a tertiary eye care centre. Thirteen diabetc patients (14 eyes) with CSMO and no history of prior photocoagulation were recruited for this study. Direct focal photocoagulation of all leaking microaneurysms was performed using an argon green laser (514 nm). A contact lens was used as a slit lamp delivery system. Evaluation of the best corrected Snellen visual acuity, contrast senstivity, slit lamp biomicroscopy, macular status on direct ophthalmoscopy and fluorescein angiography was carried out 1 month and 3 months after laser photocoagulation.

RESULTS

Following direct focal laser photocoagulation, focal CSMO resolved completely in all but one eye, 4-8 weeks later, as seen on slit lamp biomicroscopy and/or fluorescein angiography. Post-treatment, visual acuity remained stationary in eight eyes, improved by one line in three eyes, by two lines in two eyes and by three lines in one eye. The mean +/- SD pretreatment and post-treatment decimal visual acuities were 0.49+/-0.30 and 0.59+/-0.28, respectively. The mean +/- SD pre-laser contrast sensitivity score was 121.3+/-83.6, which increased significantly to a mean +/- SD of 151.6+/-80.5 fo lowing direct focal photocoagulation.

CONCLUSION

Focal argon laser photocoagulation in CSMO in diabetics helps in improving the contrast sensitivity and stabilizes the visual acuity. The changes in contrast sensitivity and visual acuity are independent of each other.

Scanning laser ophthalmoscope fundus perimetry before and after laser photocoagulation for clinically significant diabetic macular edema

PURPOSE

To prospectively evaluate functional and funduscopic changes after laser treatment in patients with diabetic retinopathy and clinically significant macular edema by scanning laser ophthalmoscope fundus perimetry.

METHODS

Thirty eyes of 30 patients with clinically significant macular edema as a result of diabetic retinopathy were prospectively examined before and at least 3 months after focal laser treatment with automatic fundus threshold perimetry using the scanning laser ophthalmoscope. Thresholds of light sensitivity were compared with age-corrected normal values and correlated with corrected visual acuity and subjective appraisal of visual function.

RESULTS

In 30 eyes, fundus perimetry lasted for 10.5+/-2.7 (mean+/-SD) minutes with 322+/-67 stimulus presentations for each eye. Whereas eight eyes remained stable (< +/-1 dB change), 15 improved concerning mean deviation (MD) (3.1+/-1.7 dB) after focal laser treatment. Stability of fixation remained the same after focal laser treatment (0.75+/-0.57 degree). Laser scars showed marked loss of function (MD > 13 dB).

CONCLUSIONS

Although light sensitivity was reduced in areas of macular edema, there was no correlation between the amount of edema and visual function. Fundus perimetry allows the creation of exact maps of retinal dysfunction before and after laser treatment. It may help in making management decisions in diabetic and nondiabetic patients by offering a sensitive parameter in addition to visual acuity.

Laser treatment of diabetic macular edema: comparison of ETDRS-level treatment with threshold-level treatment by using high-contrast discriminant central visual field testing

Grid laser is recognized as an extremely effective treatment of diabetic macular edema, although it causes significant chorioretinal damage when applied and scars that expand with time. The purpose of this study is to compare the effects of two methods of grid laser photocoagulation for diabetic macular edema on high-contrast target discrimination in the central visual field. Grid laser photocoagulation with the Early Treatment Diabetic Retinopathy Study intensity burns has previously been shown to cause full retinal thickness burns. In this study, it produced severe destruction of paraxial vision, most marked at 2 degrees to 10 degrees from fixation. Grid laser using threshold-level burns, in contrast, appeared to produce some improvement in thresholded high-contrast vision at eccentricities from 2 degrees to 3 degrees outward, but failed to normalize visual parameters at these intercepts or at intercepts closer to fixation. Therefore, the recommendations are made (1) to use screening modalities other than biomicroscopic perception of retinal swelling to define earlier opportunities for intervention in the diabetic maculopathic process and (2) to use threshold or sub-threshold methods of laser grid photocoagulation for treating leakage and/or edema.

The pattern electroretinogram (PERG) after laser treatment of the peripheral or central retina

PURPOSE

To understand whether laser photocoagulation of the retina for the treatment of diabetic retinopathy (DR) alters directly or indirectly the function of the macular region.

METHODS

Transient pattern electroretinograms (PERGs) to 30' checks have been recorded in DR patients before and 7-10 days after one treatment session (established protocol with Argon laser) of either the peripheral retina (panretinal treatment) or the central retina (paramacular focal treatment).

RESULTS

Treatment of the peripheral retina causes, in most eyes, a small increase (about 15% on average) of the PERG amplitude. Focal paramacular treatment causes a marked decrement (about 40% on average) of the PERG amplitude. Simulated retinal amputation induced by focal treatment, obtained by means of adequate stimulus masking, resulted in a 15-20% PERG decrement only.

CONCLUSIONS

The PERG increase after peripheral treatment may be due to rearrangement of both retinal and choroideal hemodynamics and does not necessarily result in useful long term changes. The PERG decrease after focal, paramacular treatment is far larger than that expected on the basis of the amputated area only. This may result from thermal and/or toxic damaging effects spreading outside the treated area. The results are relevant for both a better monitoring of central retinal function in the course of laser treatment and a better evaluation of the cost/benefit ratio after photocoagulation in DR.