Pain response and follow-up of patients undergoing panretinal laser photocoagulation with reduced exposure times

A Comprehensive Meta-Analysis on the Role of Analgesics and Anti-Inflammatories in Pan-retinal Photocoagulation

PURPOSE

Pan-retinal photocoagulation (PRP) is the mainstay of treatment for proliferative diabetic retinopathy (PDR), reducing the risk of severe vision loss. Pain poses a potential obstacle to effective laser delivery and patient compliance. Therefore, implementing pain relief strategies can enhance both treatment efficacy and patient comfort.

DESIGN

A systematic review and meta-analysis.

METHODS

We conducted a systematic review and meta-analysis according to PRISMA guidelines. The PubMed, Embase and Cochrane Central Register of Controlled Trials databases were searched for randomized controlled trials (RCTs) that enrolled patients undergoing PRP due to DR and compared analgesics or non-steroidal anti-inflammatory drugs (NSAID) to placebo. Pain was evaluated with the visual analogue scale. The version 2 of the Cochrane Collaboration's Risk of Bias in Randomized Controlled Trials tool and its version for crossover trials were used to assess the risk of bias. The Grading of Recommendations, Assessment, Development, and Evaluation tool was used to measure the certainty of evidence.

RESULTS

A total of 13 studies were included, comprising 1404 eyes from RCTs, nine of which were crossover. Patients who were administered analgesia reported a significantly lower pain sensitivity compared to those who received placebo (Standardized mean difference [SMD] -0.38; 95% confidence interval [CI] -0.58, -0.17; P<0.01; I2=69%). Subgroup analysis of systemic administration of analgesics/NSAIDs (metamizole, Entonox, acetaminophen, ibuprofen, caffeine, mefenamic acid, intramuscular ketorolac tromethamine, and potassium diclofenac) also showed a statistically significant reduction in pain when compared to placebo (SMD -0.28; 95% CI -0.50, -0.07; P<0.01; I2=43%). Exclusive eye drops administration (ketorolac tromethamine 0.5% and sodium diclofenac 0.1%) also showed a significant difference in pain sensitivity (SMD -0.46; 95% CI -0.88, -0.05; I2=83%), however with a more significant heterogeneity.

CONCLUSION

The results of this meta-analysis including over 1000 patients demonstrated that the use of analgesics significantly reduced pain sensitivity during PRP, and systemic analgesia is potentially better than topical administration when compared to placebo.

Delivery Systems in Ocular Retinopathies: The Promising Future of Intravitreal Hydrogels as Sustained-Release Scaffolds

Slow-release delivery systems are needed to ensure long-term sustained treatments for retinal diseases such as age-related macular degeneration and diabetic retinopathy, which are currently treated with anti-angiogenic agents that require frequent intraocular injections. These can cause serious co-morbidities for the patients and are far from providing the adequate drug/protein release rates and required pharmacokinetics to sustain prolonged efficacy. This review focuses on the use of hydrogels, particularly on temperature-responsive hydrogels as delivery vehicles for the intravitreal injection of retinal therapies, their advantages and disadvantages for intraocular administration, and the current advances in their use to treat retinal diseases.

[Pain after panretinal photocoagulation: 50-millisecond pulse versus conventional pulse]

Background

Diabetic retinopathy is a progressive disfunction of blood vessels of the retina secondary to chronic hyperglycemia. There are several treatments, out of which panretinal photocoagulation (PRP) stands out.

Objective

To compare the level of pain in patients undergoing PRP with different impulse.

Material and methods

Comparative, cross-sectional study that compared the level of pain in patients undergoing PRP with a 50-millisecond pulse (group A) versus conventional 200 milliseconds pulse (group B). Mann-Whitney U test was used.

Results

There were 26 patients, 12 (46.16%) female and 14 (53.84%) males. The median age was 58.73 ± 7.31 (40-75) years. 40 eyes were studied, 18 (45%) right and 22 (55%) left. The mean level of glycated hemoglobin was 8.15 ± 1.08 (6.5-12) %. The mean laser power was 297 ± 53.61 (200-380) and 214.5 ± 41.73 (170-320) milliwatts; the mean fluence was 18.85 ± 5.28 (12-28) J/cm2 and 65.9 ± 12.87 (52-98) J/cm2; the mean level of pain was 3.1 ± 1.33 (1-5) and 7.5 ± 1.23 (6-10) points for group A and B, respectively, and there was statistically significant difference (p ˂ 0.001) in the level of pain. There were no complications in any group.

Conclusion

The application of retinal 50-millisecond pulse PRP causes less pain and side effects than 200-millisecond pulse PRP.

The efficacy of oral pain relief cocktail during pan-retinal photocoagulation for diabetic retinopathy: a randomized clinical trial

PURPOSE

to evaluate the pain-relieving effect of analgesic combinations during pan-retinal photocoagulation (PRP) in patients with non-proliferative diabetic retinopathy (NPDR).

METHODS

This study was a randomized, double-blind, placebo-controlled trial. Patients with severe NPDR without previous history of PRP were included in the study. Both eyes of the patients were treated with a pan-retinal photocoagulation procedure. The retina was divided into four quadrants and the treatment plan for patients submitted to PRP was divided into four sessions. Different oral medications were given to patients 1 hour before the procedure. Capsules containing a combination of analgesic drugs (including 325 mg acetaminophen, 200 mg ibuprofen, and 40 mg caffeine, referred to as N), pregabalin capsules (75 mg, referred to as P), a combination of N capsules and P capsules (referred to as NP), and the placebo were used in each session. Each patient scored the pain sensation immediately after the procedure using a visual analog scale (VAS).

RESULT

60 eyes of 30 patients were studied. The mean value of VAS in patients receiving the placebo was 3.3 ± 1.822 units, while this scale was 3.067 ± 1.507, 3.5 ± 1.479, and 3.5 ± 1.77 in the N, P, and NP consumed patients, respectively. There was no significant difference in VAS levels and the patient's vital signs between different sessions (P = 0.512).

CONCLUSION

No evidence of the pain-relieving effect of N, P or NP was found during PRP.

TRIAL REGISTRATION

IRCT20200915048724N1. Registered 20 October 2020, https://www.irct.ir/trial/51345.

Transnasal sphenopalatine ganglion block for pain relief during panretinal photocoagulation laser for diabetic retinopathy: a pre and post interventional study

This study was performed to utilize transnasal Sphenopalatine Ganglion (SPG) block for pain reliving during panretinal photocoagulation (PRP) in diabetic patients with diabetic retinopathy. This pre and post interventional study was performed on 20 patients with proliferative diabetic retinopathy. The first PRP treatment session of all the patients is performed with no transnasal SPG block, but before holding the second session, all the patients underwent transnasal SPG block and pain levels during and after PRP were compared to each other. Before the transnasal SPG block, each nostril of all the cases was inspected for finding any obstruction in each PRP session. Transnasal SPG block was also performed in with 2% lidocaine. The mean age of the included cases was 52.84 ± 8.62 years old (from 36 to 72 years old). All the cases underwent two PRP lasers treatment sessions with the same characteristic (spot size, power and duration) for each patient. In the first and second PRP treatment sessions, the mean NRS scores were obtained immediately after the PRP laser (8.4 vs. 4.2), 15 min (8.2 vs. 4.2), 1 h (8.0 vs. 4.1), and 24 h (5.4 vs. 3.6) after the PRP respectively. The mean NRS scores significantly reduced during the second PRP treatment session compared to the first session (p < 0.001). Transnasal SPG block is a safe and effective strategy used for relieving pain caused by the PRP laser treatment in patients with diabetic retinopathy.

Pain Perception of Patients Undergoing Laser Panretinal Photocoagulation: Comparison of Single-Spot Versus Multispot Techniques

BACKGROUND AND OBJECTIVE

To compare pain intensity with single-spot versus multispot technique in laser panretinal photocoagulation, using a 532-nm, solid-state laser system.

MATERIALS AND METHODS

This was a prospective, interventional, randomized, single-masked comparison trial. Patients received two types of intervention: conventional single-spot technique, with an exposure time of 150 ms, and multispot technique, done with an exposure time of 20 ms, Both techniques used power sufficient to produce visible gray-white burns, and spot size of 20 μm. Participants received both treatments in the same eye, each one in one hemiretina, and were randomized to receive first single- or multispot technique and to the initial site of treatment. We assessed pain intensity using a numerical pain scale immediately after completion of each treatment.

RESULTS

A significantly lower pain scale was observed with the multispot when compared with the single-spot technique (coefficient [Coef]: -1.61; 95% CI, -2.49 to -0.74; P < .001), which was not affected by treatment order, the hemiretina treated, or treatment duration (P > .05). Among demographic characteristics, multiracial patients had a pain scale 1.25 greater than that of White patients (Coef: 1.25; 95% CI, 0.47 to 2.04; P = .002), but there is no effect of age or sex on the pain scale (P > .05). Regarding treatment duration, a shorter procedure was also observed in the multispot technique (Coef: -1.13; 95% CI, -1.43 to -0.82; P < .001), and it was not affected by order of treatment (P = .098), hemiretina (P = .327), pain (P = .141), or demographic data, such as age, sex, and race (P > .05).

CONCLUSION

The use of the multispot technique, with a short pulse duration (20 ms), is significantly less painful and less time-consuming for patients with proliferative retinopathy compared with the conventional single-spot technique using an exposure time of 150 ms. [Ophthalmic Surg Lasers Imaging Retina. 2022;53:40-45.].

Method for controlled tissue theranostics using a single tunable laser source

Tissue diseases and related disorders need to be first recognized using diagnostic methods and then later treated by therapeutic methods-a joint procedure called theranostics. One of the main challenges in the field of retinal therapies remains in the success of the treatment, typically improving the local metabolism, by sparing the surrounding tissue and with the immediate information of the laser effect. In our study, we present a concept for real-time controlled tissue theranostics on a proof-of-concept study capable of using a single tunable ps laser source (in terms of irradiance, fluence, and repetition rate), done on ex-vivo human retinal pigment epithelium. We have found autofluorescence intensity and lifetime imaging diagnostics very promising for the recognition and quantification of laser effects ranging from selective non-destructive molecular tissue modification to complete tissue ablation. The main novelty of our work presents the developed algorithm for optimized theranostics based on the model function used to quantify laser-induced tissue changes through the diagnostics descriptors, fluorescence lifetime and fluorescence intensity parameters. This approach, together with the operation of the single adaptable laser source, can serve as a new theranostics method in personalized medicine in the future not only limited to treat retinal diseases.

Comparison of Pain Scores Among Patients Undergoing Conventional and Novel Panretinal Photocoagulation for Diabetic Retinopathy: A Systematic Review

PURPOSE

To summarize key findings from a systematic review focusing on pain as an adverse outcome of panretinal photocoagulation (PRP) among patients with diabetic retinopathy.

DESIGN

Systematic review.

METHODS

We systematically searched articles in major databases from July to September 2020. Studies that compared pain outcomes of PRP among diabetic patients who underwent conventional single-spot laser (SSL), conventional multi-spot laser (MSL), and/or novel navigated laser (NNL) were included. The Cochrane RoB 2 tool and ROBINS-I tool were used to evaluate the risk of bias of the included randomized controlled trials (RCTs) and controlled clinical trials (CCTs), respectively.

RESULTS

We included 13 RCTs and 4 CCTs. Thirteen studies were included for Comparison 1 (Conventional SSL versus Conventional MSL), 3 studies were included for Comparison 2 (NNL versus Conventional MSL), and 3 studies were included for Comparison 3 (NNL versus Conventional SSL). A total of 783 patients and 1961 eyes were included in this review. The review showed that NNL yielded the lowest pain scores, followed by conventional MSL, then by conventional SSL.

CONCLUSION

This review summarizes findings of multiple studies that reported pain as an adverse outcome of PRP among patients with advanced diabetic retinopathy. Data from RCTs with mostly some concerns for bias (RoB 2 tool) and CCTs with mostly moderate risk of bias (ROBINS-I tool) show benefit of using MSL over SSL, and NNL over conventional systems for PRP in diabetic retinopathy, considering pain as the primary outcome.

Comparison of navigated laser and conventional single-spot laser system for induced pain during panretinal photocoagulation

To compare the panretinal photocoagulation (PRP)-induced pain response between novel navigated laser (Navilas) and conventional single-spot laser. The eyes were randomly assigned to Navilas or conventional laser. Contralateral eyes underwent PRP with the other system with 30 min resting interval. Pulse duration was 100 ms in conventional laser and 30 ms or 100 ms in Navilas and power setting was enough to create gray-white light burn on both devices. Pain response was evaluated by verbal scale (VS) (0-4) and visual analog scale (VAS) (0-10) after each PRP application. The mean age of 70 patients (140 eyes) was 62.52 ± 9.49 years. Mean power and spot numbers for Navilas and conventional laser were 291.9 ± 85.3 mW vs 368.4 ± 72.0 mW, and 375.4 ± 108.4 vs 374.2 ± 105.0 (p < 0.001 and p = 0.53, respectively). Pain scores for Navilas and conventional laser were 1.19 ± 0.73 and 1.99 ± 0.84 for VS and 2.41 ± 1.65 and 4.74 ± 2.17 for VAS (p < 0.001 and p < 0.001). More comfortable PRP is achieved with Navilas system in comparison with conventional single-spot laser system. However, small number of patients treated with same pulse duration and different contact lenses used for two systems should be taken into consideration. Besides, we did not report comparative clinical efficiency of either laser system.

Central retinal thickness following panretinal photocoagulation using a multispot semi-automated pattern-scanning laser to treat ischaemic diabetic retinopathy: Treatment in one session compared with four monthly sessions

PURPOSE

To compare central retinal thickness (CRT) after panretinal photocoagulation (PRP) with a multispot semi-automated PAttern-SCAnning Laser (PASCAL) in one session (SS-PRP) versus four monthly sessions (MS-PRP) in diabetic retinopathy.

METHODS

Multicentre, prospective, randomized, single-blinded, controlled trial evaluating the noninferiority of SS-PRP versus MS-PRP for CRT measured with macular spectral-domain optical coherence tomography (SD-OCT), with a 9-month follow-up in patients presenting severe nonproliferative diabetic retinopathy (DR) or mild proliferative DR without macular oedema (ME) at baseline.

RESULTS

Ninety-seven eyes of 97 participants with a mean age of 57.0 ± 14.2 years were included. The mean change of CRT from baseline to 9 months was not statistically different in SS-PRP or in MS-PRP: +16.9 ± 28.3 μm versus +24.7 ± 31.8 μm, respectively (p = 0.224). The variation in mean best-corrected visual acuity (BCVA) from baseline to 9 months was similar in both groups: -1.1 ± 6.5 letters versus -0.6 ± 6.2 letters (p = 0.684). The number of patients with stabilization of DR was not statistically different between the two groups. No severe complication was recorded in either group.

CONCLUSION

This study showed the noninferiority of PRP performed in one session versus four monthly sessions with a PASCAL concerning central retinal thickness for treating mild proliferative or severe nonproliferative DR without ME at baseline.

PASCAL laser platform produces less pain responses compared to conventional laser system during the panretinal photocoagulation: a randomized clinical trial

Background

Most of patients experience pain during the panretinal photocoagulation(PRP). Laser photocoagulation delivery has advanced with the introduction of pattern-scanning laser systems (PASCAL). Shorter pulse duration and less choroidal penetration believed to reduce pain during the laser treatment.

Objectives

To compare the severity of expressed pain scores in patients with PDR who underwent PRP either with PASCAL laser or conventional laser.

Methods

A total of 28 patients with a diagnosis of PDR who were scheduled for bilateral PRP therapy were enrolled into the prospective study. Both eyes were treated within the same session and while one eye was treated with PASCAL the other was treated with conventional laser randomly. Pulse duration was adjusted to 100-ms in conventional laser and 30 ms in PASCAL. The severity of pain was graded using a verbal scale and a visual analog scale (VAS).

Results

Mean age was 61.36±9.10 years. Mean verbal and VAS scores were 1.32±0.47 and 2.86±1.21 in the PASCAL laser and 2.39±0.49 and 5.75±1.35 in the conventional laser group, respectively. Differences between expressed pain scores obtained by both two scales were statistically significant (p<0.001).

Conclusion

PASCAL laser significantly alleviates pain levels possibly due to the shorter laser pulse duration and lower intensity.

Comparison of 577-nm Multispot and Standard Single-Spot Photocoagulation for Diabetic Retinopathy

OBJECTIVE

To compare two different laser strategies of panretinal photocoagulation for diabetic retinopathy.

METHODS

Single-center, randomized study including 41 eyes treated with 577-nm multispot laser with a 20-ms pulse duration (group 1) or a 532-nm single-spot laser with a 100-ms pulse duration (group 2). The outcomes included best-corrected visual acuity (BCVA) and imaging changes at baseline, 6 and 12 months, laser parameters, and results of subjective pain analysis.

RESULTS

At 12 months, the treatments did not differ significantly in BCVA, central retinal thicknesses (CRTs), improved macular edema, vitreomacular interface changes, patient-reported pain scores, or angiographic responses. Group 1 had significantly fewer treatment sessions but used more laser spots (p < 0.001).

CONCLUSION

The multispot laser required fewer applications with more spots delivered to compensate for lower fluency, showing similar patient tolerance to single-spot laser. Both groups maintained the initial visual acuities and CRTs; about 50% of cases had vitreomacular interface changes and improved macular edema, with similar angiographic improvements after 12 months.

Different lasers and techniques for proliferative diabetic retinopathy

BACKGROUND

Diabetic retinopathy (DR) is a chronic progressive disease of the retinal microvasculature associated with prolonged hyperglycaemia. Proliferative DR (PDR) is a sight-threatening complication of DR and is characterised by the development of abnormal new vessels in the retina, optic nerve head or anterior segment of the eye. Argon laser photocoagulation has been the gold standard for the treatment of PDR for many years, using regimens evaluated by the Early Treatment of Diabetic Retinopathy Study (ETDRS). Over the years, there have been modifications of the technique and introduction of new laser technologies.

OBJECTIVES

To assess the effects of different types of laser, other than argon laser, and different laser protocols, other than those established by the ETDRS, for the treatment of PDR. We compared different wavelengths; power and pulse duration; pattern, number and location of burns versus standard argon laser undertaken as specified by the ETDRS.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2017, Issue 5); Ovid MEDLINE; Ovid Embase; LILACS; the ISRCTN registry; ClinicalTrials.gov and the ICTRP. The date of the search was 8 June 2017.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of pan-retinal photocoagulation (PRP) using standard argon laser for treatment of PDR compared with any other laser modality. We excluded studies of lasers that are not in common use, such as the xenon arc, ruby or Krypton laser.

DATA COLLECTION AND ANALYSIS

We followed Cochrane guidelines and graded the certainty of evidence using the GRADE approach.

MAIN RESULTS

We identified 11 studies from Europe (6), the USA (2), the Middle East (1) and Asia (2). Five studies compared different types of laser to argon: Nd:YAG (2 studies) or diode (3 studies). Other studies compared modifications to the standard argon laser PRP technique. The studies were poorly reported and we judged all to be at high risk of bias in at least one domain. The sample size varied from 20 to 270 eyes but the majority included 50 participants or fewer.Nd:YAG versus argon laser (2 studies): very low-certainty evidence on vision loss, vision gain, progression and regression of PDR, pain during laser treatment and adverse effects.Diode versus argon laser (3 studies): very-low certainty evidence on vision loss, vision gain, progression and regression of PDR and adverse effects; moderate-certainty evidence that diode laser was more painful (risk ratio (RR) troublesome pain during laser treatment (RR 3.12, 95% CI 2.16 to 4.51; eyes = 202; studies = 3; I² = 0%).0.5 second versus 0.1 second exposure (1 study): low-certainty evidence of lower chance of vision loss with 0.5 second compared with 0.1 second exposure but estimates were imprecise and compatible with no difference or an increased chance of vision loss (RR 0.42, 95% CI 0.08 to 2.04, 44 eyes, 1 RCT); low-certainty evidence that people treated with 0.5 second exposure were more likely to gain vision (RR 2.22, 95% CI 0.68 to 7.28, 44 eyes, 1 RCT) but again the estimates were imprecise . People given 0.5 second exposure were more likely to have regression of PDR compared with 0.1 second laser PRP again with imprecise estimate (RR 1.17, 95% CI 0.92 to 1.48, 32 eyes, 1 RCT). There was very low-certainty evidence on progression of PDR and adverse effects.'Light intensity' PRP versus classic PRP (1 study): vision loss or gain was not reported but the mean difference in logMAR acuity at 1 year was -0.09 logMAR (95% CI -0.22 to 0.04, 65 eyes, 1 RCT); and low-certainty evidence that fewer patients had pain during light PRP compared with classic PRP with an imprecise estimate compatible with increased or decreased pain (RR 0.23, 95% CI 0.03 to 1.93, 65 eyes, 1 RCT).'Mild scatter' (laser pattern limited to 400 to 600 laser burns in one sitting) PRP versus standard 'full' scatter PRP (1 study): very low-certainty evidence on vision and visual field loss. No information on adverse effects.'Central' (a more central PRP in addition to mid-peripheral PRP) versus 'peripheral' standard PRP (1 study): low-certainty evidence that people treated with central PRP were more likely to lose 15 or more letters of BCVA compared with peripheral laser PRP (RR 3.00, 95% CI 0.67 to 13.46, 50 eyes, 1 RCT); and less likely to gain 15 or more letters (RR 0.25, 95% CI 0.03 to 2.08) with imprecise estimates compatible with increased or decreased risk.'Centre sparing' PRP (argon laser distribution limited to 3 disc diameters from the upper temporal and lower margin of the fovea) versus standard 'full scatter' PRP (1 study): low-certainty evidence that people treated with 'centre sparing' PRP were less likely to lose 15 or more ETDRS letters of BCVA compared with 'full scatter' PRP (RR 0.67, 95% CI 0.30 to 1.50, 53 eyes). Low-certainty evidence of similar risk of regression of PDR between groups (RR 0.96, 95% CI 0.73 to 1.27, 53 eyes). Adverse events were not reported.'Extended targeted' PRP (to include the equator and any capillary non-perfusion areas between the vascular arcades) versus standard PRP (1 study): low-certainty evidence that people in the extended group had similar or slightly reduced chance of loss of 15 or more letters of BCVA compared with the standard PRP group (RR 0.94, 95% CI 0.70 to 1.28, 270 eyes). Low-certainty evidence that people in the extended group had a similar or slightly increased chance of regression of PDR compared with the standard PRP group (RR 1.11, 95% CI 0.95 to 1.31, 270 eyes). Very low-certainty information on adverse effects.

AUTHORS' CONCLUSIONS

Modern laser techniques and modalities have been developed to treat PDR. However there is limited evidence available with respect to the efficacy and safety of alternative laser systems or strategies compared with the standard argon laser as described in ETDRS.

Electroretinogram evaluation for the treatment of proliferative diabetic retinopathy by short-pulse pattern scanning laser panretinal photocoagulation

Panretinal photocoagulation (PRP) is a standard method for proliferative diabetic retinopathy (PDR) treatment. However, conventional PRP usually significantly damages the retinal structure and vision. Retinal pattern scanning laser (PASCAL) photocoagulation has emerged as a new technique with fewer complications for the treatment of retinal disorders. This study compares the therapeutic effects of short-pulse PASCAL to conventional single-spot PRP for PDR. Fifty-two PDR patients (104 eyes) were randomly assigned into a short-pulse PASCAL-PRP treatment (SP) group and a conventional PRP treatment (TP) group. The best corrected visual acuity (BCVA) and full-field flash electroretinogram (ERG) data were evaluated before and after the two treatments. The BCVA data between before and after the PRP treatments did not show any significant difference. After the PRP treatment, the b-wave amplitude (b-A) in the dark-adapted 3.0 ERG (p = 0.0005) and the amplitude in the light-adapted 3.0 flicker ERG (p = 0.009) were significantly higher in the SP group compared with that of the TP group. In addition, after the PRP treatment, the a-wave implicit time (a-T) of light-adapted 3.0 ERG prolonged significantly in the TP group compared to the SP group. Compared with the parameters before the treatments, the a-A and b-A under dark-adapted 3.0 ERG and the b-A under the light-adapted 3.0 ERG in both TP and SP groups after the treatments decreased significantly (p < 0.05). Short-pulse PASCAL-PRP significantly attenuated partial vision damage compared to conventional PRP, although it still caused limited retinal injury and mild reduction in retinal function. These findings suggest that short-pulse PASCAL-PRP is a promising technique for PDR treatment.

Patient Comfort with Yellow (577 nm) vs. Green (532 nm) Laser Panretinal Photocoagulation for Proliferative Diabetic Retinopathy

PURPOSE

Pain associated with panretinal photocoagulation (PRP) can adversely affect the number and quality of retinal burns delivered and subsequently increase the number of treatment sessions required to achieve regression of proliferative diabetic retinopathy (PDR). We assessed comfort in patients undergoing treatment with yellow (577 nm) vs. green (532 nm) PRP for PDR.

DESIGN

Prospective, single-center, randomized crossover clinical trial.

SUBJECTS

Patients with PDR with high-risk characteristics.

METHODS

Subjects were equally randomized to first receive PRP with a laser indirect ophthalmoscope with either green (IQ 532; IRIDEX, Mountain View, CA) or yellow (IQ 577; IRIDEX) laser, followed by additional treatment with the opposite laser using standardized settings in the superior hemisphere of a single treatment eye per patient. Topical anesthetic was used in all study eyes before each treatment and power was titrated until moderate grey-white retinal burns were achieved.

MAIN OUTCOME MEASURES

The primary outcome measure was patient's perceived pain as measured with a standardized 10-point pain scale. Secondary outcome measures included laser power, treatment time, number of treatment shots with each laser, and physician ease-of-use score with each laser on a 10-point scale.

RESULTS

Forty patients (40 eyes) with a mean age of 54.0 years were enrolled. Mean pain scores were similar when comparing treatment with yellow and green laser (3.1 ± 2.3 vs. 2.8 ± 2.6; P = 0.40). No significant difference was seen in visual acuity (P = 0.44) or central macular thickness (P = 0.39) 1 month after PRP. Additionally, there were no significant differences when comparing minimum power required (243.2 ± 74.2 vs. 234.0 ± 59.6 mW; P = 0.55), treatment time (5.1 ± 3.6 vs. 5.6 ± 3.9 minutes; P = 0.384), and number of treatment shots (257.6 ± 12.6 vs. 258.0 ± 2.3; P = 0.68). Six of 7 co-investigators (85%) preferred using yellow laser over green and reported ease-of-use scores of 9.0 ± 1.2 and 7.6 ± 1.4, respectively (P = 0.07). No severe adverse events occurred.

CONCLUSIONS

Patient comfort during PRP for PDR utilizing laser indirect ophthalmoscopy is similar for green and yellow wavelengths.

Evaluation of retinal blood flow before and after panretinal photocoagulation using pattern scan laser for diabetic retinopathy

PURPOSE

Laser speckle flowgraphy (LSFG) can measure blood flow in the ocular fundus. We analyzed the relationship between retinal blood flow and panretinal photocoagulation (PRP) in diabetic retinopathy.

METHODS

This retrospective observational study examined the eyes of 35 patients with proliferative diabetic retinopathy (PDR) or non-PDR (NPDR). PRP was performed using a pattern scan laser. Using LSFG, blood flow was evaluated as the mean blur rate (MBR) or the relative flow volume (RFV). We also evaluated MBR in the vessels of the optic nerve head (MBR-V), RFV at the first retinal artery (RFV-A), and RFV at the first retinal vein (RFV-V) before bifurcation. Blood flows were measured prior to treatment initiation, during each PRP session, and after PRP.

RESULTS

The total number of laser spots created was 4258 ± 461. Regression of neovascular activity at 6 months after PRP occurred in 29 (82.85%) eyes. MBR-V significantly decreased to 83.9 ± 16% (p = .0039), 79.3 ± 21% (p = .0001), and 73.5 ± 26% (p = .0001) after the first, second, and third PRP treatment sessions. MBR-V was also reduced to 75.0 ± 25% (p = .0001), 75.0 ± 25% (p = .0001), and 80.3 ± 22% (p = .0001) at 1, 3, and 6 months following PRP. During and at 6 months after the PRP treatments, RFV-A and RFV-V were also significantly reduced (p< .01).

CONCLUSIONS

During and after PRP treatments using pattern scan laser, retinal blood flow was reduced. Retinal blood flow may be an auxiliary measurement for effectively evaluating PRP or PDR.

Comparison of Efficacy and Side Effects of Multispot Lasers and Conventional Lasers for Diabetic Retinopathy Treatment

Panretinal photocoagulation (PRP) is a standard treatment for proliferative diabetic retinopathy. Conventional laser (CL) therapy is performed in one or more sessions in single spot mode. Visual disabilities have been reported after treatment with CL, including central vision loss due to macular edema and peripheral visual field loss resulting from extensive inner retinal scarring. Multispot laser (MSL) photocoagulation has recently been introduced to clinical practice. Studies comparing PRP conducted with MSL and CL have reported that MSLs resulted in less retinal tissue damage and pain, and greater patient comfort compared to CL. The aim of this review was to compare the efficacy and side effects of MSLs and CLs for diabetic retinopathy treatment.

Lesion strength control by automatic temperature guided retinal photocoagulation

Laser photocoagulation is an established treatment for a variety of retinal diseases. However, when using the same irradiation parameter, the size and strength of the lesions are unpredictable due to unknown inter- and intraindividual optical properties of the fundus layers. The aim of this work is to investigate a feedback system to generate desired lesions of preselectable strengths by automatically controlling the irradiation time. Optoacoustics were used for retinal temperature monitoring. A 532-nm continuous wave Nd:YAG laser was used for photocoagulation. A 75-ns/523-nm Q-switched Nd:YLF laser simultaneously excited temperature-dependent pressure transients, which were detected at the cornea by an ultrasonic transducer embedded in a contact lens. The temperature data were analyzed during the irradiation by a LabVIEW routine. The treatment laser was switched off automatically when the required lesion strength was achieved. Five different feedback control algorithms for different lesion sizes were developed and tested on rabbits in vivo. With a laser spot diameter of 133???m, five different lesion types with ophthalmoscopically visible diameters ranging mostly between 100 and 200???m, and different appearances were achieved by automatic exposure time control. The automatically controlled lesions were widely independent of the treatment laser power and the retinal pigmentation.

Changes in pupil size following panretinal retinal photocoagulation: conventional laser vs pattern scan laser (PASCAL)

PurposeTo evaluate and compare the possible changes in pupil size subsequent to panretinal laser photocoagulation (PRP) via conventional laser and pattern scan laser (PASCAL).Patients and methodsForty eyes of 40 patients with diabetic retinopathy were included. 20 eyes had a PRP via conventional laser and formed Group 1. 20 eyes had a PRP via PASCAL laser and formed Group 2. The participants underwent standard ophthalmologic examination at baseline. Automated infrared pupillometry were performed at baseline and month 1.ResultsThe mean pupillary measurements (mm) for Group 1 (in the order photopic, mesopic, and scotopic conditions) were 2.88±0.34, 3.38±0.40, and 3.95±0.38, and changed to 3.64±0.42, 4.18±0.42, and 4.58±0.48, respectively. There was significant increase in pupil size at month 1 (P<0.001, P<0.001, and P<0.00, respectively). For Group 2, they were 2.90±0.38, 3.43±0.36, and 3.90±0.40, and changed to 3.18±0.42, 3.74±0.36, and 4.10±0.38, respectively. There was significant increase in pupil size at month 1 (P=0.018, P=0.014, and P=0.014, respectively). The pupil size increased significantly in both groups in all illumination conditions.ConclusıonWe have demonstrated via automated infrared pupillary measurements that PRP may significantly increase pupil size whether it is performed with conventional laser or PASCAL laser.

Investigation of Thermal Effects of Photocoagulation on Retinal Tissue Using Fine-Motion-Sensitive Dynamic Optical Coherence Tomography

To enable an objective evaluation of photocoagulation, we characterize thermal tissue changes induced by laser irradiation with different laser parameters using optical coherence tomography (OCT). Spectral-domain OCT with a newly developed image processing method was used to monitor the thermal changes of ex vivo porcine retina. A sequence of OCT B-scans was obtained at the same retinal position simultaneously with the photocoagulation. Cross-sectional tissue displacement maps with respect to an OCT image taken before laser irradiation were computed for images taken before, during, and after laser irradiation, by using a correlation-based custom algorithm. Cross-sectional correlation maps (OCT correlation maps) were also computed from an OCT image taken before laser irradiation as a base-line to visualize alterations of tissue microstructure induced by laser irradiation. By systematically controlling laser power and exposure times, tissue displacements and structural changes of 200 retinal regions of 10 porcine eyes were characterized. Thermal tissue changes were characterized by B-scan images, OCT correlation maps, and tissue displacement maps. Larger tissue deformation was induced with higher laser power and shorter exposure time, while the same total laser energy (10 mJ) was applied. The measured tissue displacements revealed the complicated dynamics of tissue displacements. Three types of dynamics were observed; lateral expansion, lateral constriction, and a type showing more complicated dynamics. The results demonstrated the ability of this OCT-based method to evaluate retinal changes induced by laser irradiation. This evaluation could lead to further understanding of thermal effects, and increasing reproducibility of photocoagulation therapy.

Pan-retinal photocoagulation and other forms of laser treatment and drug therapies for non-proliferative diabetic retinopathy: systematic review and economic evaluation

BACKGROUND

Diabetic retinopathy is an important cause of visual loss. Laser photocoagulation preserves vision in diabetic retinopathy but is currently used at the stage of proliferative diabetic retinopathy (PDR).

OBJECTIVES

The primary aim was to assess the clinical effectiveness and cost-effectiveness of pan-retinal photocoagulation (PRP) given at the non-proliferative stage of diabetic retinopathy (NPDR) compared with waiting until the high-risk PDR (HR-PDR) stage was reached. There have been recent advances in laser photocoagulation techniques, and in the use of laser treatments combined with anti-vascular endothelial growth factor (VEGF) drugs or injected steroids. Our secondary questions were: (1) If PRP were to be used in NPDR, which form of laser treatment should be used? and (2) Is adjuvant therapy with intravitreal drugs clinically effective and cost-effective in PRP?

ELIGIBILITY CRITERIA

Randomised controlled trials (RCTs) for efficacy but other designs also used.

DATA SOURCES

MEDLINE and EMBASE to February 2014, Web of Science.

REVIEW METHODS

Systematic review and economic modelling.

RESULTS

The Early Treatment Diabetic Retinopathy Study (ETDRS), published in 1991, was the only trial designed to determine the best time to initiate PRP. It randomised one eye of 3711 patients with mild-to-severe NPDR or early PDR to early photocoagulation, and the other to deferral of PRP until HR-PDR developed. The risk of severe visual loss after 5 years for eyes assigned to PRP for NPDR or early PDR compared with deferral of PRP was reduced by 23% (relative risk 0.77, 99% confidence interval 0.56 to 1.06). However, the ETDRS did not provide results separately for NPDR and early PDR. In economic modelling, the base case found that early PRP could be more effective and less costly than deferred PRP. Sensitivity analyses gave similar results, with early PRP continuing to dominate or having low incremental cost-effectiveness ratio. However, there are substantial uncertainties. For our secondary aims we found 12 trials of lasers in DR, with 982 patients in total, ranging from 40 to 150. Most were in PDR but five included some patients with severe NPDR. Three compared multi-spot pattern lasers against argon laser. RCTs comparing laser applied in a lighter manner (less-intensive burns) with conventional methods (more intense burns) reported little difference in efficacy but fewer adverse effects. One RCT suggested that selective laser treatment targeting only ischaemic areas was effective. Observational studies showed that the most important adverse effect of PRP was macular oedema (MO), which can cause visual impairment, usually temporary. Ten trials of laser and anti-VEGF or steroid drug combinations were consistent in reporting a reduction in risk of PRP-induced MO.

LIMITATION

The current evidence is insufficient to recommend PRP for severe NPDR.

CONCLUSIONS

There is, as yet, no convincing evidence that modern laser systems are more effective than the argon laser used in ETDRS, but they appear to have fewer adverse effects. We recommend a trial of PRP for severe NPDR and early PDR compared with deferring PRP till the HR-PDR stage. The trial would use modern laser technologies, and investigate the value adjuvant prophylactic anti-VEGF or steroid drugs.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013005408.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Changes in Pupil Size Following Panretinal and Focal/Grid Retinal Photocoagulation: Automatic Infrared Pupillometry Study

PURPOSE

To evaluate possible changes in pupil size subsequent to panretinal and focal/grid laser photocoagulation.

METHODS

Sixty-four eyes of 64 participants were included. Thirty-two eyes with planned panretinal photocoagulation formed Group 1, and 32 eyes with planned focal retinal photocoagulation formed Group 2. The participants underwent full ophthalmologic examination at baseline. Automated infrared pupillometry was performed at baseline and month 1.

RESULTS

The mean pupillary measurements (in millimeters) for Group 1 (in order photopic, mesopic, scotopic) were 3.09 ± 0.69 mm, 3.66 ± 0.85 mm, and 3.87 ± 1.01 mm and changed to 3.34 ± 0.74 mm, 3.82 ± 0.92 mm, and 4.03 ± 1.02 mm. There was a significant increase in pupil size at month 1 (P = 0.001, P = 0.001, P = 0.003). For Group 2, they were 2.65 ± 0.87 mm, 3.08 ± 1.08 mm, and 3.18 ± 1.19 mm and changed to 2.92 ± 0.72 mm, 3.45 ± 0.76 mm, and 3.57 ± 0.88 mm. There was no significant difference in pupil size at month 1 (P = 0.151, P = 0.106, P = 0.095).

CONCLUSION

We have demonstrated through automated infrared pupillary measurements that panretinal laser photocoagulation may significantly influence pupil size and focal/grid laser photocoagulation may not.

Metamizole versus placebo for panretinal photocoagulation pain control: a prospective double-masked randomized controlled study

BACKGROUND

Diabetic retinopathy is one of most common and threatening ocular diseases. Many of these patients need to be submitted to panretinal photocoagulation (PRP), experiencing a significant level of pain. The purpose of this study is to evaluate the effectiveness of oral metamizole in reducing pain during PRP in patients with proliferative diabetic retinopathy (PDR) and very severe non-proliferative diabetic retinopathy (VSNDR).

METHODS

Patients from a single center with PDR or VSNDR and indication of bilateral PRP were recruited for a double-masked, controlled, prospective study. The treated eyes were randomly assigned in two groups, and each patient had one eye assigned per group. Group A received 1000 mg of metamizole and group B received a placebo pill 40 min before the laser treatment. The groups were switched for the treatment of the fellow eye. Each patient scored the pain sensation immediately after each PRP section using Scott's visual analogue scale (VAS). The paired Student t test was used to measure the significance between the two groups VAS scores, with significance level adopted of p < 0.05.

RESULTS

Twenty-one patients were recruited. The level of pain was significantly lower when submitted to PRP after oral metamizole treatment compared to placebo (p = 0.002). The mean pain scores for groups A and B were 4.72 ± 1.708 and 5.89 ± 1.967, respectively. The minimum/maximum scores within groups A and B were 1/8 and 1/10, respectively.

CONCLUSIONS

The use of 1000 mg of metamizole 40 min before PRP significantly reduces the pain associated with the procedure in patients with PDR or VSNDR.

Recent developments in laser treatment of diabetic retinopathy

Laser photocoagulation has been the mainstay of diabetic retinopathy treatment since its development in mid-20^th century. With the advent of antivascular endothelial growth factor therapy, the role of laser therapy appeared to be diminished, however many advances in laser technology have been developed since. This review will describe recent advances in laser treatment of diabetic retinopathy including pattern scan laser, short-pulse duration and a reduced fluence laser, and navigated laser system for proliferative diabetic retinopathy and macular edema.

New treatments for diabetic retinopathy

Diabetic retinopathy is the major cause of vision loss in middle-aged adults. Alteration of the blood-retinal barrier (BRB) is the hallmark of diabetic retinopathy and, subsequently, hypoxia may result in retinal neovascularization. Tight control of systemic factors such as blood glucose, blood pressure and blood lipids is essential in the management of this disease. Vascular endothelial growth factor (VEGF) is one of the most important factors responsible for alteration of the BRB. The introduction of anti-VEGF agents has revolutionized the therapeutic strategies used in people with diabetic retinopathy, and the use of laser therapy has been modified. In the present article, we examine the clinical features and pathophysiology of diabetic retinopathy and review the current status of new treatment recommendations for this disease, and also explore some possible future therapies.

Randomised clinical trial evaluating best-corrected visual acuity and central macular thickness after 532-nm subthreshold laser grid photocoagulation treatment in diabetic macular oedema

Purpose

To compare best-corrected visual acuity (BCVA) and central macular thickness (CMT) after 532-nm subthreshold laser grid photocoagulation and threshold laser grid photocoagulation for the treatment of diabetic macular oedema (DME).

Patients and methods

Twenty-three patients (46 eyes) with binocular DME were enroled in this study. The two eyes of each patient were divided into a subthreshold photocoagulation group and a threshold photocoagulation group. The eyes of the subthreshold group underwent 532-nm patter scan laser system (PASCAL) 50% end point subthreshold laser grid photocoagulation therapy, whereas the threshold photocoagulation group underwent short-pulse grid photocoagulation with a 532-nm PASCAL system. BCVA and CMT were assessed in all patients before treatment, 7 days after treatment, and 1, 3, and 6 months after treatment.

Results

After grid photocoagulation, the mean BCVA improved in both the subthreshold group, and the threshold group, and the two groups did not differ statistically significantly from each other. Similarly, the macular oedema diminished in both groups after treatment, and the two groups did not differ statistically significantly from each other with regard to CMT.

Conclusion

Both 532-nm subthreshold laser grid photocoagulation and threshold laser grid photocoagulation can improve the visual acuity and reduce CMT in DME patients.

Laser photocoagulation for proliferative diabetic retinopathy

BACKGROUND

Diabetic retinopathy is a complication of diabetes in which high blood sugar levels damage the blood vessels in the retina. Sometimes new blood vessels grow in the retina, and these can have harmful effects; this is known as proliferative diabetic retinopathy. Laser photocoagulation is an intervention that is commonly used to treat diabetic retinopathy, in which light energy is applied to the retina with the aim of stopping the growth and development of new blood vessels, and thereby preserving vision.

OBJECTIVES

To assess the effects of laser photocoagulation for diabetic retinopathy compared to no treatment or deferred treatment.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2014, Issue 5), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to June 2014), EMBASE (January 1980 to June 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 3 June 2014.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) where people (or eyes) with diabetic retinopathy were randomly allocated to laser photocoagulation or no treatment or deferred treatment. We excluded trials of lasers that are no longer in routine use. Our primary outcome was the proportion of people who lost 15 or more letters (3 lines) of best-corrected visual acuity (BCVA) as measured on a logMAR chart at 12 months. We also looked at longer-term follow-up of the primary outcome at two to five years. Secondary outcomes included mean best corrected distance visual acuity, severe visual loss, mean near visual acuity, progression of diabetic retinopathy, quality of life, pain, loss of driving licence, vitreous haemorrhage and retinal detachment.

DATA COLLECTION AND ANALYSIS

We used standard methods as expected by the Cochrane Collaboration. Two review authors selected studies and extracted data.

MAIN RESULTS

We identified a large number of trials of laser photocoagulation of diabetic retinopathy (n = 83) but only five of these studies were eligible for inclusion in the review, i.e. they compared laser photocoagulation with currently available lasers to no (or deferred) treatment. Three studies were conducted in the USA, one study in the UK and one study in Japan. A total of 4786 people (9503 eyes) were included in these studies. The majority of participants in four of these trials were people with proliferative diabetic retinopathy; one trial recruited mainly people with non-proliferative retinopathy. Four of the studies evaluated panretinal photocoagulation with argon laser and one study investigated selective photocoagulation of non-perfusion areas. Three studies compared laser treatment to no treatment and two studies compared laser treatment to deferred laser treatment. All studies were at risk of performance bias because the treatment and control were different and no study attempted to produce a sham treatment. Three studies were considered to be at risk of attrition bias.At 12 months there was little difference between eyes that received laser photocoagulation and those allocated to no treatment (or deferred treatment), in terms of loss of 15 or more letters of visual acuity (risk ratio (RR) 0.99, 95% confidence interval (CI) 0.89 to 1.11; 8926 eyes; 2 RCTs, low quality evidence). Longer term follow-up did not show a consistent pattern, but one study found a 20% reduction in risk of loss of 15 or more letters of visual acuity at five years with laser treatment. Treatment with laser reduced the risk of severe visual loss by over 50% at 12 months (RR 0.46, 95% CI 0.24 to 0.86; 9276 eyes; 4 RCTs, moderate quality evidence). There was a beneficial effect on progression of diabetic retinopathy with treated eyes experiencing a 50% reduction in risk of progression of diabetic retinopathy (RR 0.49, 95% CI 0.37 to 0.64; 8331 eyes; 4 RCTs, low quality evidence) and a similar reduction in risk of vitreous haemorrhage (RR 0.56, 95% CI 0.37 to 0.85; 224 eyes; 2 RCTs, low quality evidence).None of the studies reported near visual acuity or patient-relevant outcomes such as quality of life, pain, loss of driving licence or adverse effects such as retinal detachment.We did not plan any subgroup analyses, but there was a difference in baseline risk in participants with non-proliferative retinopathy compared to those with proliferative retinopathy. With the small number of included studies we could not do a formal subgroup analysis comparing effect in proliferative and non-proliferative retinopathy.

AUTHORS' CONCLUSIONS

This review provides evidence that laser photocoagulation is beneficial in treating proliferative diabetic retinopathy. We judged the evidence to be moderate or low, depending on the outcome. This is partly related to reporting of trials conducted many years ago, after which panretinal photocoagulation has become the mainstay of treatment of proliferative diabetic retinopathy.Future Cochrane Reviews on variations in the laser treatment protocol are planned. Future research on laser photocoagulation should investigate the combination of laser photocoagulation with newer treatments such as anti-vascular endothelial growth factors (anti-VEGFs).

25th RCOphth Congress, President's Session paper: 25 years of progress in medical retina

The quarter century since the foundation of the Royal College of Ophthalmologists has coincided with immense change in the subspecialty of medical retina, which has moved from being the province of a few dedicated enthusiasts to being an integral, core part of ophthalmology in every eye department. In age-related macular degeneration, there has been a move away from targeted, destructive laser therapy, dependent on fluorescein angiography to intravitreal injection therapy of anti-growth factor agents, largely guided by optical coherence tomography. As a result of these changes, ophthalmologists have witnessed a marked improvement in visual outcomes for their patients with wet age-related macular degeneration (AMD), while at the same time developing and enacting entirely novel ways of delivering care. In the field of diabetic retinopathy, this period also saw advances in laser technology and a move away from highly destructive laser photocoagulation treatment to gentler retinal laser treatments. The introduction of intravitreal therapies, both steroids and anti-growth factor agents, has further advanced the treatment of diabetic macular oedema. This era has also seen in the United Kingdom the introduction of a coordinated national diabetic retinopathy screening programme, which offers an increasing hope that the burden of blindness from diabetic eye disease can be lessened. Exciting future advances in retinal imaging, genetics, and pharmacology will allow us to further improve outcomes for our patients and for ophthalmologists specialising in medical retina, the future looks very exciting but increasingly busy.

The evolution of laser therapy in ophthalmology: a perspective on the interactions between photons, patients, physicians, and physicists: the LXX Edward Jackson Memorial Lecture

PURPOSE

To present the evolution of laser therapy in modern ophthalmic practice.

DESIGN

Review of published experimental and clinical studies.

METHODS

A review was undertaken of the work of multiple investigators leading to the invention of the laser, its biophysical effects on ocular tissues from which it derives its name (light-amplified stimulation of emitted radiation), and the development of various laser-based devices and methods to treat common ophthalmologic disorders, with particular emphasis on new and emerging retinal and anterior segment applications.

RESULTS

Because the eye is optimized for the transmission of light and its transduction into neural signals, lasers are particularly well suited for ophthalmic therapy. This fact and the high demands for precision in therapy have inspired the development of highly sophisticated laser systems that have impacted the treatment of common diseases. These include diabetic retinopathy, age-related macular degeneration, retinal venous occlusive disease, retinopathy of prematurity, and optical aberrations including ametropia, cataract, and glaucoma, among others. Recent developments in scanning laser systems, including image-guided systems with eye tracking, real-time feedback, and ultra-short pulse durations, have enabled increased selectivity, precision, and safety in ocular therapy. However, improved outcomes have been associated with increased cost of medical care, and attention to and optimization of their cost effectiveness will continue to be required in the future.

CONCLUSIONS

The invention and evolution of modern ophthalmic lasers have enhanced therapeutic options and can serve as a heuristic model for better understanding the process of innovation, including the societal benefits and also unintended consequences, including increased costs.

The change of macular thickness following single-session pattern scan laser panretinal photocoagulation for diabetic retinopathy

PURPOSE

To identify the incidence and risk factors of macular edema development following single-session pattern scan laser panretinal photocoagulation (PRP) for eyes with diabetic retinopathy.

METHODS

Medical records were reviewed in consecutive patients who underwent single-session PRP for diabetic retinopathy. The eyes with baseline central subfield retinal thickness (CRT) less than 300 μm were included.

RESULTS

Macular edema developed in 11 (8.5%) of 129 eyes 1 months after PRP. In the multivariate analysis, baseline CRT (μm) (odds ratio [OR] = 1.04, 95% confidence interval [CI] = 1.00-1.08, p = 0.048) and presence of intraretinal cystoid spaces or subretinal fluid on spectral-domain optical coherence tomography (SD-OCT) images (OR = 38.33; 95% CI = 1.36-1,083.14, p = 0.032) were significantly associated with macular edema development at 1-month visit. Macular edema developed in two (2.1%) of 97 eyes without cystoid spaces or subretinal fluid. The macular edema was spontaneously resolved in five (45.5%) of 11 cases at 3-month visit.

CONCLUSIONS

SD-OCT may be helpful in predicting the development of macular edema, although the macular edema rarely developed after single-session pattern scan laser PRP and was spontaneously resolved in many cases.

Changes in peripapillary retinal nerve fiber layer thickness after pattern scanning laser photocoagulation in patients with diabetic retinopathy

Purpose

To examine the effects of panretinal photocoagulation (PRP) using a pattern scanning laser (PASCAL) system on the retinal nerve fiber layer (RNFL) thickness in patients with diabetic retinopathy.

Methods

This retrospective study included 105 eyes with diabetic retinopathy, which consisted of three groups: the PASCAL group that underwent PRP with the PASCAL method (33 eyes), the conventional group that underwent conventional PRP treatment (34 eyes), and the control group that did not receive PRP (38 eyes). The peripapillary RNFL thickness was measured by optical coherence tomography before, six months, and one year after PRP to evaluate the changes in peripapillary RNFL.

Results

The RNFL thickness in the PASCAL group did not show a significant difference after six months (average 3.7 times, p = 0.15) or one year after the PRP (average 3.7 times, p = 0.086), whereas that in the conventional group decreased significantly after six months (average 3.4 times, p < 0.001) and one year after PRP (average 3.4 times, p < 0.001).

Conclusions

The results of this study suggest that the PASCAL system may protect against RNFL loss by using less energy than conventional PRP.

Subvisible retinal laser therapy: titration algorithm and tissue response

PURPOSE

Laser therapy for diabetic macular edema and other retinal diseases has been used within a wide range of laser settings: from intense burns to nondamaging exposures. However, there has been no algorithm for laser dosimetry that could determine laser parameters yielding a predictable extent of tissue damage. This multimodal imaging and structural correlation study aimed to verify and calibrate a computational model-based titration algorithm for predictable laser dosimetry ranging from nondamaging to intense coagulative tissue effects.

METHODS

Endpoint Management, an algorithm based on a computational model of retinal photothermal damage, was used to set laser parameters for various levels of tissue effect. The algorithm adjusts both power and pulse duration to vary the expected level of thermal damage at different percentages of a reference titration energy dose. Experimental verification was conducted in Dutch Belted rabbits using a PASCAL Streamline 577 laser system. Titration was performed by adjusting laser power to produce a barely visible lesion at 20 ms pulse duration, which is defined as the nominal (100%) energy level. Tissue effects were then determined for energy levels of 170, 120, 100, 75, 50, and 30% of the nominal energy at 1 hour and 3, 7, 30, and 60 days after treatment. In vivo imaging included fundus autofluorescence, fluorescein angiography, and spectral-domain optical coherence tomography. Morphologic changes in tissue were analyzed using light microscopy, as well as scanning and transmission electron microscopy.

RESULTS

One hundred and seventy percent and 120% levels corresponded to moderate and light burns, respectively, with damage to retinal pigment epithelium, photoreceptors, and at highest settings, to the inner retina. 50% to 75% lesions were typically subvisible ophthalmoscopically but detectable with fluorescein angiography and optical coherence tomography. Histology in these lesions demonstrated some selective damage to retinal pigment epithelium and photoreceptors. The 30% to 50% lesions were invisible with in vivo multimodal imaging, and damage was limited primarily to retinal pigment epithelium, visible best with scanning electron microscopy. Over time, photoreceptors shifted into the coagulated zone, reestablishing normal retinal anatomy in lesions ≤100%, as seen in optical coherence tomography and light microscopy. Transmission electron microscopy at 2 months demonstrated restoration of synapses between shifted-in photoreceptors and bipolar cells in these lesions. Retinal pigment epithelium monolayer restored its continuity after 1 week in all lesions. No damage could be seen <30% level.

CONCLUSION

A retinal laser dosimetry protocol based on the Endpoint Management algorithm provides reproducible changes in retinal morphology in animals with various levels of pigmentation. This algorithm opens doors to clinical trials of well-defined subvisible and nondestructive regimes of retinal therapy, especially important for treatment of macular disorders.

Pain score of patients undergoing single spot, short pulse laser versus conventional laser for diabetic retinopathy

BACKGROUND

To compare pain score of single spot short duration time (20 milliseconds) panretinal photocoagulation (PRP) with conventional (100 milliseconds) PRP in diabetic retinopathy.

METHODS

Sixty-six eyes from 33 patients with symmetrical severe non-proliferative diabetic retinopathy (non-PDR) or proliferative diabetic retinopathy (PDR) were enrolled in this prospective randomized controlled trial. One eye of each patient was randomized to undergo conventional and the other eye to undergo short time PRP. Spot size of 200 μm was used in both laser types, and energy was adjusted to achieve moderate burn on the retina. Patients were asked to mark the level of pain felt during the PRP session for each eye on the visual analog scale (VAS) and were examined at 1 week, and at 1, 2, 4 and 6 months.

RESULTS

Sixteen women and 17 men with mean age 58.9 ± 7.8 years were evaluated. The conventional method required a mean power of 273 ± 107 mW, whereas the short duration method needed 721 ± 406 mW (P = 0.001). An average of 1,218 ± 441 spots were delivered with the conventional method and an average of 2,125 ± 503 spots were required with the short duration method (P = 0.001). Average pain score was 7.5 ± 1.14 in conventional group and 1.75 ± 0.87 in the short duration group (P = 0.001). At 1 week, 1 month, and 4 months following PRP, the mean changes of central macular thickness (CMT) from baseline in the conventional group remained 29.2 μm (P = 0.008), 40.0 μm (P = 0.001), and 40.2 μm (P = 0.007) greater than the changes in CMT for short time group.

CONCLUSION

Patient acceptance of short time single spot PRP was high, and well-tolerated in a single session by all patients. Moreover, this method is significantly less painful than but just as effective as conventional laser during 6 months of follow-up. The CMT change was more following conventional laser than short time laser.

Automatic temperature controlled retinal photocoagulation

Laser coagulation is a treatment method for many retinal diseases. Due to variations in fundus pigmentation and light scattering inside the eye globe, different lesion strengths are often achieved. The aim of this work is to realize an automatic feedback algorithm to generate desired lesion strengths by controlling the retinal temperature increase with the irradiation time. Optoacoustics afford non-invasive retinal temperature monitoring during laser treatment. A 75 ns/523 nm Q-switched Nd:YLF laser was used to excite the temperature-dependent pressure amplitudes, which were detected at the cornea by an ultrasonic transducer embedded in a contact lens. A 532 nm continuous wave Nd:YAG laser served for photocoagulation. The ED50 temperatures, for which the probability of ophthalmoscopically visible lesions after one hour in vivo in rabbits was 50%, varied from 63°C for 20 ms to 49°C for 400 ms. Arrhenius parameters were extracted as ΔE=273 J mol(-1) and A=3 x 10(44) s(-1). Control algorithms for mild and strong lesions were developed, which led to average lesion diameters of 162 ± 34 μm and 189 ± 34 μm, respectively. It could be demonstrated that the sizes of the automatically controlled lesions were widely independent of the treatment laser power and the retinal pigmentation.

Study of clinical applications and safety for Pascal® laser photocoagulation in retinal vascular disorders

PURPOSE

To establish safe laser parameter standards for 10-30 ms Pascal(®) laser in clinical practice and to evaluate clinical and visual outcomes using this 532-nm multi-spot photocoagulation system.

METHODS

Retrospective observational case series of 313 patients treated between 2006 and 2008. Evaluation of eight groups: A - panretinal photocoagulation (PRP) for proliferative diabetic retinopathy (PDR); B - focal laser treatment for clinically significant diabetic macular oedema; C - grid laser for diffuse diabetic macular oedema; D - sector PRP for ischaemic branch retinal vein occlusions (I-BRVO); E - full PRP for ischaemic central retinal vein occlusions (I-CRVO); F - macular laser treatment for macular oedema secondary to non-ischaemic BRVO; G - full PRP for rubeosis iridis and/or neovascular glaucoma (NVG) secondary to I-BRVO, I - CRVO or PDR; H - laser retinopexy for retinal breaks/degenerations.

RESULTS

Mean LogMAR visual acuity for all procedures improved postlaser (p = 0.065), and laser prevented visual loss in 85% eyes. Topical anaesthesia was only required. At mean follow-up of 5 months, 72% procedures had a successful clinical outcome. Significantly higher powers were required for PRP using Pascal(®) compared to conventional laser (p = 0.001) in PDR, I-BRVO, I-CRVO and NVG. Sixty-seven per cent of patients (15/20) were successfully treated with single-session 20-ms PRP using a mean 1952 burns. There were no laser-associated adverse effects or ocular complications associated with multi-spot PRP or macular Pascal(®) arrays.

CONCLUSIONS

The clinical efficacy using 10- to 30-ms pulse duration Pascal(®) laser is comparable to conventional standard protocols used for the treatment of vascular retinal disorders. Higher power, 10- to 30-ms pulse duration laser may be safely and effectively used in clinical practice.

Pain and accuracy of focal laser treatment for diabetic macular edema using a retinal navigated laser (Navilas)

Aim

To investigate treatment-related pain and the accuracy of navigated laser photocoagulation in the treatment of clinically significant macular edema.

Methods

Focal laser treatment of diabetic macular edema in 54 consecutive patients was digitally planned on fundus images and performed using the navigated laser photocoagulation system Navilas^® (OD-OS GmbH, Teltow, Germany). Treatment-related pain was quantified on a visual analog scale directly after treatment and compared with a matched control group who received conventional laser treatment (n = 46). In addition, for Navilas-treated patients, the accuracy of spot placement on color images was analyzed 1 month after treatment.

Results

In total, 5423 laser spots (mean 100 per eye) were analyzed. With navigated treatment, 90% of laser spots were visible on color images, of which 96% were within 100 μm from the target. Eighty percent of the laser spots were placed and visible within the 100 μm target on an intention-to-treat basis for color imaging. Optical coherence topography confirmed that laser effects were limited to the outer retina. Treatment-related pain following navigated laser photocoagulation was significantly lower than that of conventional laser treatment (1.6 vs 4.4 on a visual analog scale, P < 0.001).

Conclusion

Navigated laser effects could be visualized to a high percentage on post-treatment color images, and their location showed a high concordance to targeted areas. Patients reported that treatment-related pain following Navilas laser photocoagulation was significantly lower than pain following conventional laser treatment.

The impact of pulse duration and burn grade on size of retinal photocoagulation lesion: implications for pattern density

PURPOSE

Shorter pulses used in pattern scanning photocoagulation (10-20 milliseconds [ms]) tend to produce lighter and smaller lesions than the Early Treatment Diabetic Retinopathy Study standard 100-ms exposures. Smaller lesions result in fewer complications but may potentially reduce clinical efficacy. It is worthwhile to reevaluate existing standards for the number and size of lesions needed.

METHODS

The width of the coagulated zone in patients undergoing retinal photocoagulation was measured using optical coherence tomography. Lesions of "moderate," "light," and "barely visible" clinical grades were compared for 100, 200, and 400 μm spot sizes and pulse durations of 20 ms and 100 ms.

RESULTS

To maintain the same total area as in 1,000 standard burns (100 ms, moderate) with a 400-μm beam, a larger number of 20-ms lesions are required: 1,464, 1,979, and 3,520 for moderate, light, and barely visible grades, respectively. Because of stronger relative effect of heat diffusion with a smaller beam, with 200 μm this ratio increases: 1,932, 2,783, and 5,017 lesions of 20 ms with moderate, light, and barely visible grades correspond to the area of 1,000 standard burns.

CONCLUSION

A simple formula is derived for calculation of the required spot spacing in the laser pattern for panretinal photocoagulation with various laser parameters to maintain the same total coagulated area.

Panretinal photocoagulation for proliferative diabetic retinopathy: pattern scan laser versus argon laser

PURPOSE

To evaluate the efficacy of the pattern scan laser (PASCAL) in treating newly diagnosed high-risk proliferative diabetic retinopathy (PDR).

DESIGN

Retrospective comparative case series.

METHODS

SETTING

Institutional.

STUDY POPULATION

Eighty-two consecutive eyes of the same number of patients with newly diagnosed high-risk PDR treated with panretinal photocoagulation (PRP) using either argon green laser (41 eyes treated before February 2007) or PASCAL (41 eyes treated February 2007 or thereafter), then followed for at least 6 months.

PROCEDURE

Retrospective chart review with attention to main outcome measures, age, sex, race, follow-up interval, insulin dependence, hemoglobin A1c, and total number of lasers spots.

MAIN OUTCOME MEASURES

Persistence or recurrence of neovascularization, incidence of vitreous hemorrhage (VH), neovascularization of the iris (NVI), neovascular glaucoma (NVG), and need for vitrectomy.

RESULTS

Patients treated with the PASCAL and argon laser received a similar number of spots (1438 vs 1386; P = .59). Patients treated with the PASCAL were more likely to experience persistence or recurrence of neovascularization within 6 months of initial treatment (73% vs 34%; P < .0008). The study was not adequately powered to detect a significant difference in incidence of vitreous hemorrhage, NVI, NVG, or need for vitrectomy.

CONCLUSIONS

When using traditional laser settings, PRP performed with the PASCAL is less effective than that performed with traditional argon laser in effecting lasting regression of retinal neovascularization in the setting of previously untreated high-risk PDR. Physicians may need to change treatment parameters when using PASCAL pattern laser therapy for high-risk PDR.

Pascal panretinal laser ablation and regression analysis in proliferative diabetic retinopathy: Manchester Pascal Study Report 4

AIMS

To quantify the 20-ms Pattern Scan Laser (Pascal) panretinal laser photocoagulation (PRP) ablation dosage required for regression of proliferative diabetic retinopathy (PDR), and to explore factors related to long-term regression.

METHODS

We retrospectively studied a cohort of patients who participated in a randomised clinical trial, the Manchester Pascal Study. In all, 36 eyes of 22 patients were investigated over a follow-up period of 18 months. Primary outcome measures included visual acuity (VA) and complete PDR regression. Secondary outcomes included laser burn dosimetry, calculation of retinal PRP ablation areas, and effect of patient-related factors on disease regression. A PDR subgroup analysis was undertaken to assess all factors related to PDR regression according to disease severity.

RESULTS

There were no significant changes in logMAR VA for any group over time. In total, 10 eyes (28%) regressed after a single PRP. Following top-up PRP treatment, regression rates varied according to severity: 75% for mild PDR (n=6), 67% for moderate PDR (n=14), and 43% in severe PDR (n=3). To achieve complete disease regression, mild PDR required a mean of 2187 PRP burns and 264 mm(2) ablation area, moderate PDR required 3998 PRP burns and area 456 mm(2), and severe PDR needed 6924 PRP laser burns (836 mm(2); P<0.05).

CONCLUSIONS

Multiple 20-ms PRP treatments applied over time does not adversely affect visual outcomes, with favourable PDR regression rates and minimal laser burn expansion over 18 months. The average laser dosimetry and retinal ablation areas to achieve complete regression increased significantly with worsening PDR.

Analgesic effect of etoricoxib (Arcoxia®) 120 mg during retinal laser photocoagulation

Purpose

Panphotocoagulation reduces the risk of vision loss in proliferative diabetic retinopathy. However, not many patients tolerate this treatment well due to pain. Therefore, we evaluated the analgesic effect of etoricoxib during photocoagulation in patients with proliferative diabetic retinopathy.

Methods

A prospective, randomized, double-blind study was conducted on 44 consecutive patients eligible for panphotocoagulation due to proliferative diabetic retinopathy. During the first panphotocoagulation session, both groups were treated without medication. During the following session, the control group received a placebo pill while the other group received etoricoxib 120 mg. Both groups took the medicines 1 hour before the treatment. After each session, the patients quantified the level of pain on a subjective visual scale.

Results

A total of 52 patients were selected for the study and the data of 44 patients were analyzed. In the control group, the average level of pain in the first session was 7.68 (standard deviation 1.70), dropping to an average of 7.32 (standard deviation 1.39) after ingestion of placebo. Therefore, there was no statistical difference (p=0.1187). In contrast, the average level of pain without the drug in the group taking etoricoxib 120 mg was 7.95 (standard deviation 1.46) vs 5.18 (standard deviation 1.65) with the drug, a significant statistical difference (p<0.001).

Conclusions

Etoricoxib 120 mg reduces pain and can be used before panphotocoagulation. Data show that the medication is more effective against pain during photocoagulation than placebo.