Diode laser photocoagulation for diabetic macular oedema

Optimizing treatment for diabetic macular edema during cataract surgery

Diabetic macular edema (DME) causes visual impairment in diabetic retinopathy (DR). Diabetes mellitus is a global epidemic and diabetic individuals are at risk of developing DR. Approximately 1 in 10 diabetic patients suffers from DME, which is the commonest cause of vision-threatening DR at primary-care screening. Furthermore, diabetes predisposes to a higher frequency and a younger onset of cataract, which further threatens vision in DME patients. Although cataract extraction is an effective cure, vision may still deteriorate following cataract surgery due to DME progression or recurrence, of which the risks are significantly higher than for patients without concurrent or previous history of DME at the time of operation. The management of pre-existing DME with visually significant cataract is a clinical conundrum. Deferring cataract surgery until DME is adequately treated is not ideal because of prolonged visual impairment and maturation of cataract jeopardizing surgical safety and monitoring of DR. On the other hand, the progression or recurrence of DME following prompt cataract surgery is a profound disappointment for patients and ophthalmic surgeons who had high expectations for postoperative visual improvement. Prescription of perioperative anti-inflammatory eye drops is effective in lowering the risk of new-onset DME after cataract surgery. However, management of concurrent DME at the time of cataract surgery is much more challenging because DME is unlikely to resolve spontaneously even with the aid of anti-inflammatory non-steroidal or steroid eye drops. A number of clinical trials using intravitreal injection of corticosteroids and anti-vascular endothelial growth factor (anti-VEGF) as first-line therapy have demonstrated safety and efficacy to treat DME. These drugs have also been administered perioperatively for the prevention of DME worsening in patients undergoing cataract surgery. This article reviews the scientific evidence to guide ophthalmologists on the efficacy and safety of various therapies for managing patients with DME who are particularly vulnerable to cataract surgery-induced inflammation, which disintegrates the blood-retinal barrier and egression of fluid in macular edema.

Intraocular reflectance of the ocular fundus and its impact on increased retinal hazard

PURPOSE

Inside the eye light can be reflected multiple times due to light-tissue interactions and the spherical geometry of the eye. Due to these optical properties, a defined retinal area is not only illuminated by direct light but also by indirect, reflected light from the inner side of the eyewall. During illumination for ophthalmic surgery, this could lead to an unintended increase in intraocular retinal irradiance, which was already discussed in previous studies but without a detailed consideration of spectral differences and a potential influence of pigmentation. In this study this effect is investigated wavelength-dependent to see if different wavelengths lead to different increase in irradiance, with a special focus on the raise in photochemical and thermal hazard to the retina. It is also examined whether this effect is dependent on the pigmentation of the eye.

METHODS

The reflectance properties of either less or highly pigmented porcine eyes are measured in the wavelength range between 350 and 1100nm with an integrating sphere and a spectrometer. With these reflectance spectra the wavelength-dependent Sphere Multiplier M of porcine eyes can be calculated, which represents the increase of radiance due to multiple reflections inside a sphere compared to a planar diffuser of the same size. Based on measurements of the emitted irradiance of ophthalmic illumination fibers the increase in photochemical and thermal retinal hazard due to these multiple reflections is calculated for eyes with small and high amounts of pigmentation.

RESULTS

The reflectance of the inner eyewall in the range between 350 and 1100nm is significantly higher for eyes with low pigmentation (between 4.90% and 37.44% reflectance) in comparison to eyes with a high amount of pigmentation (between 4.30% and 28.88% reflectance). The Sphere Multiplier for the inner side of the eyewall (sclera, choroid and retina) ranges between 1.13 and 1.59 and between 1.13 and 1.48 for eyes with low and high pigmentation, respectively, in the range between 350 and 1100nm. The reflectance, as well as the Sphere Multiplier, is strongly wavelength-dependent due to the absorption spectra of melanin and hemoglobin, which are located in the eye. With increasing wavelength, the reflection properties and the Sphere Multiplier also increases. With this, the photochemical retinal hazard of highly pigmented eyes increases by (14.11± 0.09)% and of lightly pigmented eyes by (16.75±0.35)% compared to if the reflection properties are not considered. The thermal retinal hazard increases by (14.30±0.07)% for highly pigmented eyes and by (19.65±0.17)% for low pigmented eyes.

CONCLUSION

This study demonstrates that the anatomy and pigmentation of the eye plays an important role for the reflectance properties of the eye and for the photochemical and thermal hazard to the retina.

Direct Photocoagulation for Treating Microaneurysms with Hyperreflective Ring in Eyes with Refractory Macular Edema Associated with Branch Retinal Vein Occlusion

Microaneurysms (MAs) with hyperreflective rings are sometimes detected in eyes with refractory macular edema (ME) associated with branch retinal vein occlusion (BRVO) for more than 12 months after onset when examined using optical coherence tomography (OCT). We proposed that these MAs could result in refractory ME secondary to BRVO and hypothesized that OCT-guided direct photocoagulation of MAs could result in a reduction in refractory ME. Eleven eyes (from eleven different patients) with refractory ME associated with BRVO for more than 12 months following initial treatment were included. The mean number of MAs in each eye at baseline was 3.5 ± 2.0 (range, 1–8). The mean central subfield thickness, central macular volume, and parafoveal macular volume significantly decreased 6 months following initial direct photocoagulation when compared with those at baseline (baseline = 378.7 ± 61.8 μm, post-treatment = 304.2 ± 66.7 μm, p = 0.0005; baseline = 0.3 ± 0.049 mm³, post-treatment = 0.24 ± 0.053 mm³, p = 0.001; and baseline = 2.5 ± 0.14 mm³, post-treatment = 2.28 ± 0.15 mm³, p = 0.001, respectively). Moreover, the mean best-corrected visual acuity significantly improved 6 months following initial direct photocoagulation when compared with that at baseline (baseline = 0.096 ± 0.2 logarithm of the minimum angle of resolution (logMAR), post-treatment = 0.0077 ± 0.14 logMAR, p = 0.031). Direct photocoagulation could be suggested as a treatment option for refractory ME associated with BRVO in MAs with a hyperreflective ring on OCT.

The impact of central foveal thickness on the efficacy of subthreshold micropulse yellow laser photocoagulation in diabetic macular edema

To evaluate the efficacy of short-term subthreshold micropulse yellow laser photocoagulation (SMYLP) on eyes with diabetic macular edema (DME) with different central foveal thicknesses (CFT). Eighty eyes of 40 patients who had previously undergone ranibizumab treatment for DME and who subsequently had recurrent macular edema were included to the study. The study subjects were divided into four groups according to their initial CFT values (group 1, 250-300 μm; group 2, 301-400 μm; group 3, > 401 μm; group 4, 250-300 μm untreated control subjects). Patients were treated with SMYLP for one session and followed for 6 months. All patients underwent complete ophthalmologic evaluation. The alteration from baseline in CFT and the best corrected visual acuity (BCVA) were measured. Patients with a pretreatment CFT ≤ 300 μm experienced the statistically significant reduction in CFT and gain in BCVA at 2 months (p < 0.05), whereas patients with baseline CFT > 300 μm experienced no significant change (p > 0.05). Hyperautofluorescence lesions, that were not previously described, were detected in fundus autofluorescence imaging in the early period after SYMLP laser and these lesions were regressed with time. Our study indicates that the SYMLP provides a statistically significant improvement in BCVA and a reduction in CFT in the patients with a pretreatment CFT of 300 μm or less in DME and can be safe and effective in mild DME 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.

Efficacy of subthreshold micropulse laser in the treatment of diabetic macular edema is influenced by pre-treatment central foveal thickness

PURPOSE

To determine if the severity of diabetic macular edema influences the effectiveness of subthreshold micropulse (STMP) laser treatment.

METHODS

A total of 63 eyes of 58 patients with diabetic macular edema were divided into two groups based on their initial central foveal thickness (CFT). Group 1 had CFT ≤400 μm, group 2 had CFT >400 μm. The change from baseline in CFT and visual acuity were compared at 3, 6 and 12 months follow-up. Patients were considered for retreatment with micropulse laser at 3 months if macular edema had not improved. Patients were considered for rescue anti-VEGF injections if there was clinically significant macular edema at 6 months follow-up. Number of laser retreatments, injections, and any adverse effects from STMP laser were recorded.

RESULTS

Group 1 (n=33) experienced an average of 55 μm reduction in CFT and 0.2 log MAR gain in visual acuity at 12 months (P<0.001). No patient required rescue anti-VEGF injections. Group 2 (n=30) experienced no significant change in CFT or visual acuity by 6 months despite retreatment with STMP in 19 eyes. From 6 to 12 months follow-up, all the patients in group 2 received rescue Bevacizumab injections that resulted in 307 μm reduction in CFT and 0.3 log MAR improvement in visual acuity (P<0.001). No adverse effects from STMP laser were recorded.

CONCLUSION

Severity of edema can influence the effects of STMP laser. STMP monotherapy is safe and effective in treating edema of mild to moderate severity.

Recent developments in retinal lasers and delivery systems

Photocoagulation is the standard of care for several ocular disorders and in particular retinal conditions. Technology has offered us newer lasing mediums, wavelengths and delivery systems. Pattern scan laser in proliferative diabetic retinopathy and diabetic macular edema allows laser treatment that is less time consuming and less painful. Now, it is possible to deliver a subthreshold micropulse laser that is above the threshold of biochemical effect but below the threshold of a visible, destructive lesion thereby preventing collateral damage. The advent of solid-state diode yellow laser allows us to treat closer to the fovea, is more effective for vascular structures and offers a more uniform effect in patients with light or irregular fundus pigmentation. Newer retinal photocoagulation options along with their advantages is discussed in this review.

Laser treatment for diabetic macular edema in the 21st century

Diabetic macular edema (DME) is the leading cause of blindness in the diabetic population. The diabetes Control and Complications Trial reported that 27% of patients affected by type 1 diabetes develop DME within 9 years of onset. Other studies have shown that in patients with type 2 diabetes, the prevalence increased from 3% to 28% within 5 years of diagnosis to twenty years after the onset. At the present time, despite the enthusiasm for evaluating several new treatments for DME, including the intravitreal therapies for DME (e.g., corticosteroids, and anti-VEGF drugs), laser photocoagulation remains the current gold standard and the only treatment with proven efficacy in a wide range of clinical trials for this condition. Despite being the standard technique for comparison and evaluation of the emerging treatments, we have generally poor understanding of the ETDRS recommendations, and we often forget about the results of laser in DME. The purpose of this review is to update our knowledge on laser photocoagulation for DME with an extensive review of the ETDRS results and discuss the laser techniques. Furthermore, we will describe the new developments in laser systems and review the current indications and results. Finally, we will discuss the results of laser treatments versus the current pharmacological therapies. We conclude by trying to provide a general overview that which laser treatment must be indicated and what types of lasers are currently recommended.

Retina rejuvenation therapy for diabetic macular edema: a pilot study

PURPOSE

To prospectively investigate the safety and efficacy of a novel frequency-doubled nanosecond-pulsed laser with discontinuous beam energy distribution (2RT, Ellex) for the treatment of diabetic macular edema.

METHODS

Twenty-three consecutive patients (38 eyes) with newly diagnosed diabetic macular edema were recruited and assessed with logarithm of the minimum angle of resolution best-corrected visual acuity, central macular thickness measured with optical coherence tomography (OCT/scanning laser ophthalmoscope, OPKO/OTI), microperimetry, fundus photography, and fundus fluorescein angiography. Macular grid treatments were performed with 2RT laser system by 1 operator. Patients were examined with logarithm of the minimum angle of resolution best-corrected visual acuity, central macular thickness, microperimetry, and fundus photography at 3 weeks and 6 weeks and 3 months and 6 months. Fundus fluorescein angiography was repeated at 3 months and 6 months.

RESULTS

Six months postoperatively, 17 patients (28 eyes) completed the study. No complications were identified after 2RT therapy. Intraoperative retinal discoloration was observed in 2 cases, fully resolved at 3 months with no permanent anatomical or functional changes. Mean logarithm of the minimum angle of resolution visual acuity improved from 20/44 at baseline to 20/27 at 6 months. The change in best-corrected visual acuity was significant (P = 0.0190). Central macular thickness in the central 1-mm subfield, retinal exudates and vascular leakage decreased in the majority of patients at 6 months (46, 41, and 55%, respectively), although the change from baseline was not statistically significant. Microperimetry confirmed photoreceptor integrity and showed a trend of improvement that correlated with decreased central macular thickness.

CONCLUSION

For the first time, we achieved a beneficial effect on diabetic macular edema without the side effects of conventional laser therapy. The efficacy of this system in comparison with standard argon laser photocoagulation and in the treatment of other conditions affecting the retinal pigment epithelium needs further investigation.

Characterization of microaneurysm closure after focal laser photocoagulation in diabetic macular edema

PURPOSE

To characterize microaneurysm closure following focal laser photocoagulation in diabetic macular edema (DME) using simultaneous fluorescein angiography (FA) and spectral-domain optical coherence tomography (SD-OCT).

DESIGN

Retrospective observational case series.

METHODS

Leaking microaneurysms (n = 123) were analyzed in eyes (n = 29) with nonproliferative diabetic retinopathy (NPDR) that underwent navigated focal laser photocoagulation in DME and were followed at 3, 6, and 12 months. Closure of diabetic microaneurysms was characterized in detail following focal laser using SD-OCT.

RESULTS

Closure rate of microaneurysms by both FA and SD-OCT was 69.9% (84/123), 79.7% (98/123), and 82.9% (102/123) at 3, 6, and 12 months, respectively. Microaneurysm closure rate increased at 6 and 12 months compared to 3 months (P < .003, P < .001). Over half of closed microaneurysms (45/86, 52.3%) left hyperreflective spots while the remaining half (41/86, 47.7%) disappeared without any hyperreflectivity by SD-OCT at 3 months. Hyperreflective spots decreased at 6 (36/99, 36.4%) and 12 months (17/102, 16.7%) with a concomitant increase in complete loss of reflectivity at 6 (63/99, 63.6%) and 12 months (85/102, 83.3%). Smaller outer and inner diameters and heterogeneous lumen reflectivity were positively associated with microaneurysm closure at 12 months (P < .0001, P < .001, P < .03).

CONCLUSIONS

Characterization of microaneurysms following focal laser photocoagulation resulted in hyperreflective spots and complete resolution of all reflectivity using SD-OCT. Smaller microaneurysms and those with heterogeneous lumen were positively associated with microaneurysm closure. These findings provide greater understanding of localized retinal changes following focal laser photocoagulation in DME treatment.

Diabetic macular edema: new trends in management

The treatment of diabetic macular edema may be evolving from a laser ablative approach into a pharmacotherapeutic approach. The exponential growth that has occurred over the past decade in the retinal pharmacotherapy field has led to the development of several pharmacotherapies for retinal vascular diseases such as diabetic macular edema. Many of these agents, in the form of intravitreal injections or sustained delivery devices, have already undergone clinical trial testing for safety and efficacy and many others are currently being similarly evaluated. Some of these agents have proven to be more efficacious than traditional laser therapy, and it is possible that traditional laser therapy for diabetic macular edema may be abandoned altogether in the near future, especially with the introduction of the micropulse laser. However, more research and experience is still needed in order to determine the best treatment agent or combination of therapeutic modalities, as well as the best treatment regimen for a given patient. In this article, we briefly review the major new developments in the field of diabetic macular edema treatment. In addition, we touch on some of the promising forthcoming therapies.

Micropulsed diode laser therapy: evolution and clinical applications

Many clinical trials have demonstrated the clinical efficacy of laser photocoagulation in the treatment of retinal vascular diseases, including diabetic retinopathy. There is, however, collateral iatrogenic retinal damage and functional loss after conventional laser treatment. Such side effects may occur even when the treatment is appropriately performed because of morphological damage caused by the visible endpoint, typically a whitening burn. The development of the diode laser with micropulsed emission has allowed subthreshold therapy without a visible burn endpoint. This greatly reduces the risk of structural and functional retinal damage, while retaining the therapeutic efficacy of conventional laser treatment. Studies using subthreshold micropulse laser protocols have reported successful outcomes for diabetic macular edema, central serous chorioretinopathy, macular edema secondary to retinal vein occlusion, and primary open angle glaucoma. The report includes the rationale and basic principles underlying micropulse diode laser therapy, together with a review of its current clinical applications.

Diabetic macular edema: pathogenesis and treatment

Diabetic macular edema is a major cause of visual impairment. The pathogenesis of macular edema appears to be multifactorial. Laser photocoagulation is the standard of care for macular edema. However, there are cases that are not responsive to laser therapy. Several therapeutic options have been proposed for the treatment of this condition. In this review we discuss several factors and mechanisms implicated in the etiology of macular edema (vasoactive factors, biochemical pathways, anatomical abnormalities). It seems that combined pharmacologic and surgical therapy may be the best approach for the management of macular edema in diabetic patients.

Diabetic macular edema: what is focal and what is diffuse?

PURPOSE

To review the available information on classification of diabetic macular edema (DME) as focal or diffuse.

DESIGN

Interpretive essay.

METHODS

Literature review and interpretation.

RESULTS

The terms focal diabetic macular edema and diffuse diabetic macular edema frequently are used without clear definitions. Published definitions often use different examination methods and often are inconsistent. Evaluating published information on the prevalence of focal and diffuse DME, the responses of focal and diffuse DME to treatments, and the importance of focal and diffuse DME in assessing prognosis is hindered because the terms are used inconsistently. A newer vocabulary may be more constructive, one that describes discrete components of the concepts such as extent and location of macular thickening, involvement of the center of the macula, quantity and pattern of lipid exudates, source of fluorescein leakage, and regional variation in macular thickening and that distinguishes these terms from the use of the term focal when describing one type of photocoagulation technique. Developing methods for assessing component variables that can be used in clinical practice and establishing reproducibility of the methods are important tasks.

CONCLUSIONS

Little evidence exists that characteristics of DME described by the terms focal and diffuse help to explain variation in visual acuity or response to treatment. It is unresolved whether a concept of focal and diffuse DME will prove clinically useful despite frequent use of the terms when describing management of DME. Further studies to address the issues are needed.

A proposed new classification for diabetic retinopathy: the concept of primary and secondary vitreopathy

BACKGROUND

Many eyes with proliferative diabetic retinopathy (PDR) require vitreous surgery despite complete regression of new vessels with pan retinal laser photocoagulation (PRP). Changes in the vitreous caused by diabetes mellitus and diabetic retinopathy may continue to progress independent of laser regressed status of retinopathy. Diabetic vitreopathy can be an independent manifestation of the disease process.

AIM

To examine this concept by studying the long-term behavior of the vitreous in cases of PDR regressed with PRP.

MATERIALS AND METHODS

Seventy-four eyes with pure PDR (without clinically evident vitreous traction) showing fundus fluorescein angiography (FFA) proven regression of new vessels following PRP were retrospectively studied out of a total of 1380 eyes photocoagulated between March 2001 and September 2006 for PDR of varying severity. Follow-up was available from one to four years.

RESULTS

Twenty-three percent of eyes showing FFA-proven regression of new vessels with laser required to undergo surgery for indications produced by vitreous traction such as recurrent vitreous hemorrhage, tractional retinal detachment, secondary rhegmatogenous retinal detachment and tractional macular edema within one to four years.

CONCLUSION

Vitreous changes continued to progress despite regression of PDR in many diabetics. We identifies this as "clinical diabetic vitreopathy" and propose an expanded classification for diabetic retinopathy to signify these changes and to redefine the indications for surgery.

Subthreshold micropulse diode laser photocoagulation for clinically significant diabetic macular oedema: a three-year follow up

PURPOSE

To report the long-term visual outcome of subthreshold micropulse diode laser photocoagulation for clinically significant diffuse diabetic macular oedema (CSME).

DESIGN

Non-comparative case-series.

METHODS

The main outcome measures of this 3-year follow-up study of infrared (810 nm) subthreshold diode micropulse laser photocoagulation for CSME were visual outcome and the angiographic CSME status of 19 patients (25 eyes).

RESULTS

Visual acuity stabilized or improved in 84% of treated eyes by the end of the first year. The result was maintained in the second year and by the third year, 92% maintained vision. However, more patients needed supplementary grid laser in the third year than in the second year. CSME decreased in 92% of the eyes and resolved in 88% in the first year. By the second year, 92% showed complete resolution. However, in the third year, recurrent CSME was noted in 28% of patients.

CONCLUSION

This study has the longest follow up reported so far and demonstrating that subthreshold micropulse diode laser photocoagulation has a beneficial long-term effect on visual acuity and resolution of CSME with minimal chorio-retinal damage.

Current treatment approaches in diabetic macular edema

PURPOSE

To review current treatment approaches in diabetic macular edema (DME).

METHODS

The underlying pathopathology, classifications and diagnostic examination techniques including fluorescein angiography, optical coherence tomography and stereoscopic biomicroscopy. Treatment modalities with focal or grid argon laser photocoagulation, pars plana vitrectomy with and without peeling of the inner limiting membrane (ILM), as well as intravitreal injections using triamcinolone acetonide or novel vascular endothelial growth factor (VEGF) inhibitors are described.

RESULTS

DME results from a series of biochemical and cellular changes, causing progressive leakage and exudation. Focal and grid photocoagulation remains the standard care for diabetic maculopathy. However, the availability of new agents raises the possibility of improvements if significant benefits can be validated in randomized clinical trials. Posterior vitreous attachments play a critical role through several mechanical or physiological mechanisms. Vitrectomy without ILM removal seems to be effective in reducing the retinal thickness and improving visual acuity.

CONCLUSION

A proper evaluation of the vitreous and retina is fundamental to select the most appropriate treatment approach in DME. While small microaneurysms with focal DME may be treated by conventional focal photocoagulation, diffuse DME which do not respond to grid photocoagulation may benefit from intravitreal injections using triamcinolone acetonide or novel VEGF inhibitors. Eyes with DME and additional vitreous traction may benefit from pars plana vitrectomy without ILM peeling. A combination of laser, pharmacological and surgical treatment modalities may be necessary to maintain central vision in eyes with DME.

Use of the Diode Laser With Intraoperative Mitomycin C in Endocanalicular Laser Dacryocystorhinostomy

PURPOSE

To determine the safety and efficacy of the diode laser with intraoperative mitomycin C in endocanalicular laser dacryocystorhinostomy (ECL-DCR).

METHODS

In a prospective case series of 40 ECL-DCRs using the diode laser, mitomycin C was placed intraoperatively in all cases. The main outcome measure was resolution or improvement of epiphora and no major laser damage intranasally. Patients were followed for at least 18 months.

RESULTS

Forty consecutive ECL-DCRs on 30 patients (23 females, 7 males, mean age 62 years) were performed from April 2000 to December 2001. The success rate at 12 months postoperatively was 87.5%. All failures were due to a constricted nasal osteotomy. No significant intraoperative or postoperative complications were recorded.

CONCLUSIONS

Diode laser ECL-DCR with mitomycin C appears to be a safe and effective treatment modality for primary acquired nasolacrimal duct obstruction.

Transpupillary thermotherapy for the treatment of occult CNV in age-related macular degeneration: a prospective randomized controlled pilot study

PURPOSE

To evaluate whether transpupillary thermotherapy (TTT) reduces the risk of moderate visual loss in patients with occult choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD).

METHODS

A group of 25 patients were recruited and randomized into TTT or placebo groups. Patients were included if they had a subfoveal purely or predominantly (> 50%) occult CNV secondary to AMD with best corrected visual acuity (BCVA) of 6/60 or better and the lesion was not larger than 4.5 mm. Treatment was carried out using an 810-nm Oculight diode laser with a fixed spot size covering the whole lesion according to the standard protocol. The same procedure was used for the control group, except that the power was set at zero. The patients were followed up at 6 weeks, 3 months and then every 6 months for up to 2 years. A maximum of three treatments were administered in both groups if there was evidence of persistent leakage from CNV.

RESULTS

At the 12-month follow-up, there was no significant difference in the mean values for BCVA distance and near or contrast sensitivity between the treatment and control groups. The Mann-Whitney test was used to assess the differences in BCVA and contrast sensitivity between the groups, both at baseline and at the 12-month follow-up. No statistically significant difference was found; both groups lost on average two lines of BCVA.

CONCLUSION

Transpupillary thermotherapy appeared to have been of no benefit in preventing further visual loss in patients with occult CNV in this pilot study.

ULTRASTRUCTURAL ANALYSIS OF RABBIT RETINA IRRADIATED WITH A NEW 670-NM DIODE RED LASER AT DIFFERENT POWERS

PURPOSE

Diode lasers have compact dimensions, efficient electric-optical conversion, absence of major cooling requirements, long useful life, and minimal maintenance. We verified the structural and ultrastructural effects of diode red laser emissions at 670 nm on pigmented rabbit retina.

METHODS

Transpupillary laser pulses were applied to rabbit retinas at variable powers with a spot size of 500 microm ( approximately 1,000 microm at the retina level) and duration of 200 milliseconds. Light and electron microscopic analyses were performed.

RESULTS

Subthreshold non-visible lesions were produced using a power of 200 mW. Ophthalmoscopically visible lesions were produced using a power of 400 mW. More prominent lesions were obtained using a higher power (600 mW). Structural and peculiar ultrastructural changes correlated with the power used. In general, damage was incurred by the retinal pigment epithelium with extension into the superficial choroid posteriorly and into the outer retina anteriorly. The inner retina was involved at higher power levels.

CONCLUSIONS

Ultrastructural analysis of rabbit retina treated with the 670-nm diode laser adds newer insights on tissue changes after thermal irradiation. The effects observed are consistent with those reported for the krypton red laser. The 670-nm diode laser is an economic small-size photocoagulator that appears to be a promising modality for transpupillary laser photocoagulation of the retina.

Vitrectomy for persistent diffuse diabetic macular edema

PURPOSE

To evaluate the potential benefit of vitrectomy in eyes with persistent diffuse macular edema.

DESIGN

Prospective randomized comparative clinical trial.

METHODS

Eyes with diffuse diabetic macular edema for 6 to 18 months, an attached posterior hyaloid, and grid laser photocoagulation performed at least 4 months before were included. Patients were randomized either to a vitrectomy group or to a control group.

MAIN OUTCOME MEASURES

Evaluations of Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity, reading vision, and retinal thickness were carried out at baseline and 1, 3, and 6 months after enrollment.

RESULTS

Fifty-six eyes (100%) were enrolled in this study. Twenty-five eyes (44.6%) were randomized into Gr I (vitrectomy group) and 31 eyes (55.4%) into Gr II (controls). Both groups were comparable in mean age (62.7 years and 63.9 years) and distribution of gender (one third male, two thirds female). ETDRS visual acuity showed a statistical significance in favor of Gr I at all time points (P = .035 to .005 Fisher's exact test). With Jaeger charts a significance for Gr I was found only at the 6-month examination (P = .01). With optical coherence tomography, the different behavior of retinal thickness changes in both groups during follow-up was statistically significant; P values were <.0001 for month 1, 3, and 6, preferring Gr I.

CONCLUSIONS

We provide evidence that vitrectomy with internal limiting membrane peeling is superior to observation alone in eyes with persistent diffuse diabetic macular edema for 6 to 18 months. Longer follow-up periods and larger series might be needed to confirm these results and gain additional information.

Infrared micropulsed laser treatment for diabetic macular edema--subthreshold versus threshold lesions

PURPOSE

To assess the effectiveness of subthreshold (invisible after placement) and threshold (barely visible after placement) 810nm laser photocoagulation in the treatment of clinically significant diabetic macular edema.

METHODS

A grid of subthreshold laser spots was used to treat patients with diabetic edema. Retrospectively, the results of treatment of 20 eyes of 20 patients were compared to the results of treatment of 120 eyes of 120 patients using a grid of threshold laser lesions.

RESULTS

At six months, 60% of subthreshold treated eyes and 75% of threshold treated eyes showed anatomic resolution of macular edema. Improvement or stabilization of visual acuity was achieved in 85% of threshold or subthreshold treated eyes.

CONCLUSION

Gentle grid treatment of regions of diabetic macular edema was effective in ameliorating the edema and limiting visual loss. Subthreshold laser was less effective in promoting resolution of edema compared to threshold lesions, though the difference was not significant in this instance.

Subthreshold micropulse diode laser treatment in diabetic macular oedema

BACKGROUND/AIM

Enlargement of laser scars after retinal argon laser photocoagulation can give rise to deterioration in visual acuity. Subthreshold micropulse diode laser may decrease this risk. The aim of this study was to compare the effectiveness of subthreshold micropulse diode laser (810 nm) and conventional argon laser (514 nm) photocoagulation for the treatment of clinically significant macular oedema in diabetic patients.

METHODS

23 eyes of 16 patients were randomised to either treatment. Follow up was conducted for a minimum of 5 months. Changes in visual acuity and macular oedema measured by optical coherence tomography were examined.

RESULTS

Visual acuity remained stable in all treatment groups throughout the observation period. Changes in retinal thickness were small both foveally and perifoveally. In patients with focal macular oedema a significant reduction in retinal thickness (9% approximately -26 microm, p = 0.02) was seen foveally 3 months after diode laser photocoagulation.

CONCLUSION

Subthreshold micropulse diode laser and conventional argon laser treatment showed an equally good effect on visual acuity. Subthreshold micropulse diode laser showed a stabilising or even improving effect on macular oedema. The combination of primary diode laser and supplementary argon laser might be particularly favourable in reducing diabetic macular oedema.

Initial clinical experience using a diode red laser (670 nm) in the treatment of retinal disease

AIM

To investigate the clinical use of a 670-nm diode red laser in the treatment of a number of retinal conditions.

METHODS

In all, 17 eyes of 17 patients were treated for conditions such as proliferative diabetic retinopathy, retinal neovascularization in central retinal vein occlusion, rhegmatogenous retinal lesions and retinal breaks, and prophylactic peripheral retinopexy prior to silicone oil removal after three port pars plana vitrectomy.

RESULTS

Regression of neovascularization was observed in all the eyes treated for vascular proliferation at the 3-month follow-up visit. Adhesive pigmented scars were observed in the remaining eyes 1 month after treatment. No major complications were recorded.

CONCLUSIONS

In this pilot study, the 670-nm diode laser appears to be a promising modality for laser photocoagulation of the retina.

Lasers in ophthalmology

Laser technology continues to progress with the addition of new lasers, new delivery systems, and new applications. The introduction of lasers to veterinary ophthalmology has radically changed the level of care that we can provide to our patients. The development of the diode laser has particularly had an impact on veterinary ophthalmology. The diode's affordability, portability, and broad applications for veterinary patients have allowed laser surgery to become a routine part of veterinary ophthalmology practice. Educating the public and veterinary community in available laser techniques will generate improved ophthalmic care and provide more data on which to build future applications.

Frequency-doubled Nd:YAG laser for the treatment of exudative diabetic maculopathy

PURPOSE

To determine the clinical efficacy of frequency-doubled Nd:YAG (FD YAG) laser for the treatment of diabetic clinically significant macular oedema (CSMO).

METHODS

A prospective pilot study was carried out on 55 eyes with CSMO. FD YAG laser exposures were applied in a focal or grid pattern. The results were evaluated by Snellen visual acuity, slit-lamp biomicroscopy, colour photography and fundus fluorescein angiography.

RESULTS

At mean review of 5.3 months, macular oedema had resolved either completely or partly in 44 (80%) eyes, was unchanged in 10 (18%) eyes and progressed in 1 (2%) eye. Visual acuity improved in 11 (20%), stabilised in 40 (73%) and deteriorated in 4 (7%) eyes.

CONCLUSION

FD YAG laser therapy is effective in the treatment of CSMO. It combines the ergonomic advantages of a solid-state laser with the benefits of its wavelength. A comparison between the clinical results of FD YAG and other lasers used in the treatment of CSMO is, however, required.

Transpupillary thermotherapy (TTT) for the treatment of choroidal neovascularisation

AIM

To assess the effectiveness of transpupillary thermotherapy (TTT) for the treatment of classic and occult choroidal neovascularisation (CNV).

METHOD

In a retrospective, case selected, open label trial 44 eyes of 42 patients with CNV secondary to age related macular degeneration (ARMD) were studied. 44 eyes with angiographically defined CNV were treated with diode laser (810 nm) TTT. Laser beam sizes ranged between 0.8 and 3.0 mm and power settings between 250-750 mW. Treatment was given in one area for 1 minute, the end point being no visible change, or a slight greying of the retina. Outcome was assessed with Snellen visual acuity and clinical examination; in 24/44 patients angiographic follow up was available.

RESULTS

12 predominantly classic CNV and 32 predominantly occult membranes were followed up for a mean of 6.1 months (range 2-19). Mean change in vision for classic membranes was -0.75 (SD 1.75) Snellen lines and occult membranes was -0.66 Snellen lines (2.1) (p>0.05). Predominantly classic membranes were closed in 75% (95% CI: 62.5-87.5) of eyes, remained persistent in 25% (95% CI: 12.5-37.5); no recurrences occurred. Predominantly occult membranes were closed in 78% (95% CI: 70.1-85.3) of eyes, remained persistent in 12.5% (95% CI: 6.6-18.5), and were recurrent in 5.1% (95% CI: 4.2-14.3).

CONCLUSIONS

Transpupillary thermotherapy is a potential treatment for CNV. It is able to close choroidal neovascularisation while maintaining visual function in patients with classic and occult disease. Further trials of TTT are needed to compare this intervention with the natural history and other treatment modalities.

Grid photocoagulation for focal diabetic macular edema with focal leaks and hard exsudates involving the peri-foveolar area

This study was conducted to determine whether indirect grid laser therapy is effective in reducing focal diabetic macular edema characterised by focal leaks and hard exsudates involving the para-foveal area (less than 300 microns from the center of the fovea). Since focal coagulation of microaneurysms in such a critical location can be deleterious, indirect grid pattern laser treatment may be used in such cases.

Quantitative fluorescein angiography following diode laser retinal photocoagulation

OBJECTIVE

An in vivo study was done to establish if laser-induced damage of the retina could be quantified using fluorescein angiography.

METHOD

This study was carried out on rabbit eyes (n = 6) with an 810 nm diode laser (spot diameter: 500 microm, pulse duration: 1 second, power: 100 mW-400 mW) adapted on a slit lamp. Fluorescence measurements were performed with a fundus camera connected to a fluorescence imaging system. Fluorescence staining of the retina was evaluated by mathematical modeling. Lesions were correlated to laser parameters and to histologic data.

RESULTS

Image analysis shows that the laser lesions stained progressively. Fluorescence appears first at the borders of the lesion exhibiting a fluorescent ring. A progressive increase of the fluorescence into the central zone is observed. The maximum fluorescence intensity into the center of the laser spot is obtained after a delay depending on the laser energy. Below 100 +/- 20 mW, lesions are detectable by fluorescence imaging only. A fluorescence plateau appears for a threshold light dose above 200 +/- 20 mW. Mathematical modeling demonstrates that quantitative assessment of laser-induced damage to the retina is feasible using fluorescence imaging.

CONCLUSION

The quantification of fluorescence staining in terms of both intensity and time can contribute to a better quantification of laser-induced damage. At last, since laser damage may mimic naturally occurring pathology, this method should also be considered to quantify different types of lesions.

Diode laser-induced thermal damage evaluation on the retina with a liposome dye system

BACKGROUND AND OBJECTIVES

The aim of the study was to evaluate the feasibility of retinal thermal damage assessment in a rabbit eye model by using laser-induced release of liposome-encapsulated dye.

STUDY DESIGN/MATERIALS AND METHODS

After anesthesia, thermosensitive liposomes (DiStearoyl Phosphatidyl Choline: DSPC) loaded with 5,6-carboxyfluorescein were injected intravenously to pigmented rabbits. Retinal photocoagulations were performed with a 810nm diode laser (P=100-400 mW, laser spot=500 microm, 1s) (OcuLight, IRIS Medical Instruments, Mountain View, CA). Fluorescence measurements in the area of the laser exposures were then realized with a digitized angiograph (CF-60UVi, Canon-Europe, The Netherlands; OcuLab, Life Science Resources, UK).

RESULTS

Fluorescent spots were observed for power ranging from 100 +/- 5 mW to 400 +/- 5 mW. The fluorescence intensity increased linearly with the power and reached a plateau at 280 +/- 5 mW. The fluorescence intensity was correlated to the maximum temperature at the center of the laser spot with a linear increase from 42 +/- 3 degrees C to 65 +/- 3 degrees C. These results are in agreement with our two previous studies with DSPC liposomes for temperature measurements in a tissue model and then in a vascular model.

CONCLUSION

This preliminary study demonstrates the possibility of a laser-induced release of liposome-encapsulated dye for a quantification of diode laser induced thermal damage in ophthalmology. Such a method could be useful for a real-time monitoring of laser photocoagulation for conditions such as choroidal neovascular membranes when a precise thermal damage is required near the foveolar area.

Micropulse laser in the treatment of diabetic macular edema

The micropulse laser is a new development in laser therapy. Micropulsing is frequent short pulses of subthreshold intensity applied to retinal lesions. It has been shown to be effective in diabetic macular edema, branch vein occlusion, and drusen. Although the initial landmark studies showed it to be effective, the exact parameters have not been established. This article illustrates the current state of its use.

Clinical applications of the MicroPulse diode laser

PURPOSE

To evaluate the efficacy of the Iris Oculight MicroPulse 810 nm diode laser in the treatment of macular oedema secondary to either branch retinal vein occlusion (BRVO) or diabetic maculopathy and in the treatment of proliferative diabetic retinopathy. The specific advantages of this type of laser delivery are greater retinal pigment epithelial specificity and less damage to the inner retina, thus preserving visual field and colour contrast sensitivity.

METHODS

Fifty-two eyes of 33 consecutive patients were treated over a 6-month period. Thirteen eyes had proliferative diabetic retinopathy and 39 had macular oedema secondary to BRVO or diabetic maculopathy. Panretinal and grid pattern photocoagulation were performed using the micropulse mode with the laser on for 100-300 microseconds and off for between 1900 and 1700 microseconds repeatedly in a pulse envelope of 0.1-0.3 s duration. Microaneurysms were not treated directly. Patients were assessed clinically and angiographically at 3 and 6 months.

RESULTS

Ten eyes (77%) with proliferative disease showed some regression of new vessels at 6 months. Twenty-two eyes (57%) showed resolution of macular oedema at 6 months. Visual acuity was maintained in 27 eyes (69%) and improved in 11 eyes (28%).

CONCLUSION

Diode laser in micropulse mode is effective in the management of diabetic and occlusive macular oedema and proliferative diabetic disease.

The effect of the surgeon and the laser wavelength on the response to focal photocoagulation for diabetic macular edema

OBJECTIVE

To determine the effect of the surgeon and the wavelength of laser used on the response to focal photocoagulation for diabetic macular edema.

DESIGN

Retrospective case-control study.

PARTICIPANTS

Forty-four matched pairs of cases by two different retina surgeons in the study of surgeon influence were examined. Sixty-nine matched pairs of cases using dye yellow versus argon green laser treatment in the study of wavelength influence also were studied. In both studies, eyes were matched for the only patient-dependent variables affecting outcome: age, initial visual acuity, follow-up time, and diabetic control by diet versus any other method.

INTERVENTION

Focal laser photocoagulation for clinically significant diabetic macular edema was performed.

MAIN OUTCOME MEASURE

Visual acuity at 6 months follow-up was measured.

RESULTS

For the study in which the only difference was the surgeon, at 6 months follow-up the mean difference in logarithm of the minimum angle of resolution (logMAR) visual acuity was -0.045, 95% confidence interval (-0.160, 0.070). For the study in which wavelength varied, at 6 months the mean difference in logMAR visual acuity was -0.048, 95% confidence interval (-0.147, 0.052). The power of the surgeon study to detect a difference in the logMAR visual acuity of 0.3 is 88% and of the wavelength study to detect this difference is 99%.

CONCLUSION

In looking at the 6-month visual outcome after focal laser photocoagulation for clinically significant diabetic macular edema, different fellowship trained surgeons and the choice of green or yellow wavelength had no effect on the treatment outcome.

Diabetic retinopathy

Diabetic retinopathy is the commonest cause of blindness amongst individuals of working age. The onset of retinopathy is variable. Regular ophthalmic screening is essential in order to detect treatable lesions early. Retinal laser therapy is highly effective in slowing the progression of retinopathy and in preventing blindness. As the sufferers of diabetes mellitus, the commonest endocrine disorder, now constitute approximately 1-2% of Western populations, concerted multidisciplinary effort must be made towards cost-effective community screening by the medical community.

The treatment of macular disease using a micropulsed and continuous wave 810-nm diode laser

OBJECTIVE

The purpose of the study is to determine whether the 810-nm diode wavelength using a rectangular waveform is clinically effective in the treatment of choroidal neovascularization from age-related macular degeneration and to determine whether macular edema secondary to branch vein occlusion or diabetic retinopathy can be effectively treated with this laser using the micropulse waveform.

DESIGN

Review of consecutive nonrandomized patients whose eyes were treated with the diode laser over a 30-month period.

PARTICIPANTS

Fifty-three patients with an initial presentation of choroidal neovascularization located subfoveally (77%), extrafoveally (17%), and juxtafoveally (6%); 14 patients with macular edema from a branch vein occlusion; and 59 patients with diabetic macular edema, 40 of which were treated for the first time.

INTERVENTION

Ablative rectangular wave laser photocoagulation was applied to the choroidal neovascular membranes and very light threshold treatment was applied in a macular grid to treat retinal edema. Microaneurysms were not targeted.

MAIN OUTCOME MEASURES

Anatomic resolution of macular edema or choroidal neovascularization and visual acuity.

RESULTS

Sixty percent of eyes treated for choroidal neovascularization had no persistence or recurrence at 6 months, and 72% achieved visual stabilization. In 8% of eyes, some localized bleeding occurred during photocoagulation. Clinical resolution of macular edema from branch vein occlusion occurred by 6 months in 92% of eyes, and 77% had stabilization of visual acuity. At 6 months, 76% of newly treated patients with diabetic macular edema and 67% of previously treated patients had clinical resolution of their edema. Vision was improved or stabilized in 91% and 73% of newly treated and retreated patients at 6 months, respectively.

CONCLUSIONS

The micropulsed 810-nm diode laser is clinically effective in the treatment of macular edema from venous occlusion and diabetic retinopathy, and the rectangular (normal) mode diode laser can be used in many eyes with choroidal neovascularization.

Diode laser (810 nm) versus argon green (514 nm) modified grid photocoagulation for diffuse diabetic macular edema

OBJECTIVE

To compare argon green (514 nm) versus diode laser (810 nm) modified grid laser photocoagulation treatment in diffuse diabetic macular edema (DDME).

DESIGN

Randomized, prospective clinical trial.

PARTICIPANTS

Patients with DDME and diabetic retinopathy of fewer than two high-risk characteristics in severity, no previous laser photocoagulation for diabetic macular edema, and no other ocular condition that could interfere with assessment of treatment results.

INTERVENTION

One hundred seventy-one eyes of 91 patients were randomized to either argon green (514 nm) or diode laser (810 nm) modified grid laser photocoagulation for DDME. Follow-up was conducted for a minimum of 12 months (16.55 +/- 3.52 months). Retreatment was performed for residual edema involving the foveal avascular zone.

MAIN OUTCOME RESULTS

Visual improvement, visual loss, reduction-elimination of macular edema, and the number of supplemental treatments.

RESULTS

A comparison of visual improvement, visual loss, reduction-elimination of macular edema, and the number of supplemental treatments showed no statistical difference between the groups (P > 0.05 for all groups). Reduction-elimination of DDME was better in the group without cystoid macular edema than the group with cystoid macular edema, but visual outcome appeared to be similar in both groups. History of hypertension or poor initial visual acuity (< or = 20/80) at entry into the study had no significant effect on the outcome. However, the patients without systemic vascular disease have improved more than those with systemic vascular disease regardless of the type of the laser used.

CONCLUSIONS

Diode laser (810 nm) modified grid laser photocoagulation for DDME is equivalent to argon green (514 nm) and patients without systemic vascular disease are more likely to improve after laser treatment with either wavelength.

The effect of patient characteristics on response to focal laser treatment for diabetic macular edema

PURPOSE

The purpose of the study was to determine which patient characteristics influence response to focal photocoagulation for clinically significant diabetic macular edema (CSME).

METHODS

A retrospective chart review was performed of 547 eyes from 361 patients who were observed for at least 1 year (mean, 2.6 +/- standard deviation 1.7 years) after surgery. Preoperative patient characteristics were tested for their significance in predicting outcome using multiple regression analysis.

RESULTS

Increasing patient age has a negative effect on visual outcome (P = 0.0179). Patients with diet-controlled diabetes show improvement in mean vision, whereas patients whose diabetes is controlled with insulin, oral agents, or both show declines, and these differences are significant (P < 0.0001). Neither cataract surgery before or after focal photocoagulation nor simultaneous panretinal photocoagulation for patients having concomitant high-risk proliferative retinopathy had a significant effect on outcome.

CONCLUSIONS

Younger patients with CSME and those with diet-controlled diabetes can be given more favorable prognoses. Patients with CSME and high-risk proliferative disease can have cost-effective simultaneous focal and panretinal photocoagulation without adversely affecting visual outcome.

Comparative effects of argon green and krypton red laser photocoagulation for patients with diabetic exudative maculopathy

AIMS/BACKGROUND

Focal treatment of diabetic macular oedema is usually done using a haemoglobin absorbing wave-length, such as argon green laser. This study aimed to compare photocoagulation with argon green (514 nm) and krypton red (647 nm), which is poorly absorbed by haemoglobin, in the focal treatment of patients with diabetic exudative maculopathy.

METHODS

A total of 151 eyes of 78 outpatients were assigned randomly to receive either argon green (n = 79) or krypton red (n = 72) laser treatment. Pretreatment and post-treatment ocular examinations included visual acuity, fundus biomicroscopic examination, and fluorescein angiography. A total of 141 eyes of 73 patients were available for evaluation after 1 year follow up.

RESULTS

No statistically significant difference was found between the two treatment groups with respect to visual acuity results, resorption of hard exudates, and resolution of focal retinal oedema.

CONCLUSION

Krypton red laser was effective in the treatment of diabetic exudative maculopathy. Our data suggest that differential absorption of the various wavelengths by haemoglobin within microaneurysms may not be an important factor for ultimate success of focal treatment.