Clinical Efficacy of Navigated Panretinal Photocoagulation in Proliferative Diabetic Retinopathy JAY CHHABLANI, SARITA SAMBHANA, ANNIE MATHAI, VISHALI GUPTA, J. FERNANDO AREVALO, AND IGOR KOZAK  PURPOSE:

To compare the clinical efficacy of navigated pattern and conventional slit-lamp pattern panretinal photocoagulation (PRP).  DESIGN: Randomized clinical trial.  METHODS: Seventy-four eyes with proliferative diabetic retinopathy (PDR) in need of PRP were randomly assigned to 1 of 4 groups: PRP conventional pattern 30 ms, 100 ms, navigated pattern 30 ms, 100 ms pulse. Navigated laser is a fundus camera–based photocoagulator with retinal eye tracking. Outcome variables included stability of visual acuity, regression or development of neovascularization and need for retreatment sessions and surgical intervention, pain perception, and procedure time.  RESULTS: There was no change in visual acuity between pre- and post-treatment measurements among the study groups. Short pulse groups in total required 22 procedures compared to 12 procedures in long pulse groups (P < .05). A trend toward worse outcome using 30 ms pulse duration treatments is expressed by slightly increased relative risk of 1.3 compared to 100 ms groups. Only 2 eyes required vitreoretinal surgery for nonclearing vitreous hemorrhage, 1 in each 30 ms group; insignificantly different between study groups (P [ .98). The pain score was lower with navigated laser as compared to conventional laser in both 30 ms groups (P [ .1) and 100 ms groups, where it reached statistical significance (P [ .02). Pain experience was significant (P < .001) between navigated 100 ms pattern and conventional single-spot 100 ms treatments.  CONCLUSIONS: This study demonstrates better clinical efficacy of 100 ms compared to 30 ms treatments using both conventional and navigated pattern lasers. The ability to use long-pulse-duration navigated pattern treatments broadens therapeutic options for PRP in

Accepted for publication Feb 16, 2015. From L V Prasad Eye Institute, Hyderabad, India (J.C., S.S., A.M.); and King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia (V.G., J.F.A., I.K.). Inquiries to Igor Kozak, King Khaled Eye Specialist Hospital, P.O. Box 7191, Riyadh 11462, Kingdom of Saudi Arabia; e-mail: ikozak@kkesh. med.sa

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proliferative diabetic retinopathy. (Am J Ophthalmol 2015;159(5):884–889. Ó 2015 by Elsevier Inc. All rights reserved.)

L

ASER PANRETINAL PHOTOCOAGULATION (PRP) IS

effective for the treatment of proliferative diabetic retinopathy (PDR). The Diabetic Retinopathy Study (DRS)1 and Early Treatment Diabetic Retinopathy Study (ETDRS)2,3 established standardized treatment with parameters of 200–500 mm spot size and pulse duration of 100–200 milliseconds (ms) and power to produce moderate-intensity burns. This procedure is continued peripherally to achieve a total of 1200–1600 applications over 2–3 sessions.3 The ETDRS protocol represents the current gold standard for treating PDR. The introduction of pattern scanning laser systems such as PASCAL (Topcon Medical Laser Systems, Inc; Tokyo, Japan) allow delivery of various predetermined laser spot patterns4 that significantly reduce treatment time and the patient’s perception of pain.5–7 However, this improvement requires a reduction of the pulse duration to 10–30 ms, which deviates from the ETDRS protocol. This reduction in pulse duration is required to respect the eye movements that occur while the laser pattern is applied to the retina. Some have speculated that the reduced effectiveness of pattern scanning laser compared to conventional laser photocoagulation for cases of neovascularization is attributable to this reduction in pulse duration.8 Others have suggested adjustment of the treatment parameters to compensate for the reduced efficacy in neovascularization.9 In 2009, fundus camera–based navigated laser photocoagulation with retinal eye tracking (NAVILAS; OD-OS GmbH, Berlin, Germany) was introduced.10 Initial studies established its role in focal treatment.11–13 However, this laser technology has several navigation functions for panretinal laser treatment, including imaging and the delivery of single and multispot laser patterns into the far periphery by continuous prepositioning of the laser beam relative to eye movements. Owing to stable fixation, multispot treatment patterns may be applied with longer pulse durations (eg, 100 ms or longer). Hence, navigated panretinal pattern photocoagulation (nPRP) allows adherence to the EDTRS protocol.

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RIGHTS RESERVED.

0002-9394/$36.00 http://dx.doi.org/10.1016/j.ajo.2015.02.006

Recently, conventional and navigated pattern PRP spots were compared for treatment of PDR.14 A study concluded that navigated PRP achieved more uniform laser burns compared to conventional pattern PRP.14 However, the clinical efficacy of navigated and conventional pattern laser has not been previously compared. This prospective, interventional, randomized trial compared the clinical efficacy of navigated pattern and conventional slit-lamp pattern PRP by assessing differences in the stability of visual acuity, regression or development of neovascularization, retreatments, and other surgical interventions.

METHODS  PATIENTS:

This study was performed at the L V Prasad Eye Institute, Hyderabad, India and the King Khaled Eye Specialist Hospital (KKESH), Riyadh, Saudi Arabia. The study and data accumulation were carried out with approval from the Institutional Review Boards at each site. This study adhered to the tenets of the Declaration of Helsinki. Prior informed consent was obtained from the study patients, who subsequently underwent either navigated laser or conventional pattern laser treatment. Patients were enrolled at both study sites. Inclusion criteria were age of 18 years or older with type 1 or 2 diabetes mellitus and high-risk PDR, defined as neovascularization at the optic disc (NVD); presence of NVD associated with vitreous or preretinal hemorrhage; and neovascularization elsewhere (NVE) with more than a half disc area associated with vitreous or preretinal hemorrhage. Patients with low-risk PDR features with special indications such as monocular status, patients with poor compliance, and pregnant patients were excluded. Other exclusion criteria were any history of prior panretinal laser treatment or vitrectomy in the study eye; history of anti-angiogenic injections within the previous 2 months; evidence of center-involved diabetic macular edema; intravitreal dexamethasone implant; media opacities such as significant cataract, corneal opacity, or vitreous hemorrhage obscuring fundus details; coagulation abnormalities; or use of anticoagulants other than aspirin. All patients underwent a comprehensive ophthalmic evaluation including measurement of best-corrected visual acuity, slit-lamp biomicroscopy, intraocular pressure (IOP) measurement by applanation tonometry, and dilated funduscopy. Color fundus photographs and fluorescein angiography were performed at baseline prior to laser photocoagulation, as previously described.14  LASER PROCEDURE AND FOLLOW-UP:

Laser photocoagulation was performed using the NAVILAS (OD-OS GmbH, Berlin, Germany) laser system for patients randomized to navigated PRP or the PASCAL pattern scanning laser (Topcon Medical Laser Systems, Inc, Tokyo, Japan) for patients randomized to conventional single-spot or

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pattern PRP. Treatments were performed by the same vitreoretinal specialists at each site (J.C. and I.K.). Patients were consecutively enrolled and randomized into 4 groups: Group 1: navigated PRP with short pulse (20–30 ms) duration patterns (NAVILAS 30); Group 2: conventional PRP with short pulse (20–30 ms) duration patterns (PASCAL 30); Group 3: navigated pattern laser with long pulse (100–200 ms) duration (NAVILAS 100); Group 4: conventional single-spot laser with long pulse (100–200 ms) duration (PASCAL 100). Laser parameters were as follows: power to achieve a grayish white burn, spot size of 300 mm for the navigated groups and 200 mm for the conventional groups; 1.5 burn width spacing for patterns and pulse duration according to the treatment group. All treatments with the NAVILAS laser were performed with a proprietary lens (OD-OS GmbH) with no spot magnification. Topical 0.5% proparacaine was instilled in the eye prior to placement of the lens. Therefore the spot was set at 300 mm, to achieve 300 mm burn on the retina to match the retinal burn size in the conventional groups. For all treatments with the PASCAL laser, a Mainster 165 PRP lens was used (Ocular Instruments Inc, Bellevue, Washington, USA) with 1.963 magnification. At KKESH only, patients graded their perception of pain using a visual analog pain scale (VAS). The VAS consisted of a 10-cm line, with 0 on one end representing no pain and 10 at the other end representing the worst pain ever experienced.14 The time for laser application was recorded to review the utility of the laser settings in each group. All patients were evaluated from enrollment in January 2013 until their last visit at 6 months. Postoperatively, all participants underwent an ophthalmic examination including measurement of visual acuity, slit-lamp biomicroscopy, applanation tonometry, dilated funduscopy, and color fundus photography. A loss to follow-up was not recorded.  STATISTICAL ANALYSIS:

All data were entered into a MS-Excel 2010 spreadsheet (Microsoft Corporation, Redmond, Washington, USA) and analyzed with Statistical Package R (Foundation for Statistical Computing, Vienna, Austria).15,16 Statistical significances were calculated with Student t test (visual acuity, treatment time, pain score), x2 test, and the relative risk (regression/recurrence rate of neovascularization, need for additional treatment). A P value less than .05 was considered statistically significant.

RESULTS  PATIENTS AND LASER PROCEDURE:

The study sample was composed of 74 eyes (52 eyes from L V Prasad Eye Institute and 22 eyes from KKESH) of 47 patients with high-risk PDR. There were 21 eyes in Group 1, 22 eyes in Group 2, 17

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TABLE 1. Clinical Comparison of Navigated and Conventional Pattern Laser Panretinal Photocoagulation in Proliferative Diabetic Retinopathy: Baseline Characteristics

Pulse

Pattern

Number of Eyes

Age

Mean VA (SD) (logMAR)

Mean Follow-up (SD) (mo)

NVD

NVE

VH

Mean Number of Spots (SD)

30 ms 30 ms 100 ms 100 ms

Navigated pattern Conventional pattern Navigated pattern Conventional single-spot

21 22 17 14

51 6 9 55 6 7 53 6 10 52 6 8

0.37 6 0.32 0.47 6 0.31 0.52 6 0.52 0.62 6 0.52

663 564 662 563

6 7 11 7

18 19 11 9

2 5 3 3

1810 6 369 2334 6 656 1120 6 446 1433 6 513

logMAR ¼ logarithm of minimal angle of resolution; NVD ¼ neovascularization of disc; NVE ¼ neovascularization elsewhere; SD ¼ standard deviation; VA ¼ visual acuity; VH ¼ vitreous hemorrhage.

TABLE 2. Clinical Comparison of Navigated and Conventional Pattern Laser Panretinal Photocoagulation in Proliferative Diabetic Retinopathy: Visual Acuity at Baseline and at Last Follow-up Pulse

Pattern

Baseline VA (SD) (logMAR)

Follow up VA (SD) (mo)

P

30 ms 30 ms 100 ms 100 ms

Navigated pattern Conventional pattern Navigated pattern Conventional single spot

0.37 6 0.32 0.47 6 0.31 0.52 6 0.52 0.62 6 0.52

0.37 6 0.37 0.53 6 0.43 0.47 6 0.36 0.53 6 0.44

.35 .47 .52 .62

logMAR ¼ logarithm of minimal angle of resolution; SD ¼ standard deviation; VA ¼ visual acuity.

eyes in Group 3, and 14 eyes in Group 4. Table 1 presents the mean age of the patients, baseline ocular characteristics, and number of laser applications for all groups. At the end of the procedure all visible retinal areas were filled with photocoagulation burns. The laser power to produce white retinal burns was similar among all groups (200– 400 mW), as was density of laser applications. All treatments were uneventful and no adverse events such as bleeding or vision loss occurred.  VISUAL ACUITY: There was no significant change in visual acuity in any of the groups (Table 2). There was no change in visual acuity in the navigated short pulse group. There was minor (but not statistically significant) loss of visual acuity in the conventional short pulse group.  REGRESSION/DEVELOPMENT OF NEOVASCULARIZATION: Both NVD and NVE were grouped together and

analyzed as ‘‘neovascularization’’ as they both represent the same process in different locations. We have used clinical and fluorescein angiographic criteria to diagnose the presence/regression of neovascularization. There was no statistically significant change in the development or resolution of neovascularization in all groups (Table 3). There was no new development of neovascularization in Groups 3 and 4 (long pulse) out to 6 months postoperatively. Nine percent of eyes in Group 1 (navigated short pulse) and 5% of eyes in Group 2 (conventional short pulse) developed new neovascularization. The resolution of neovascularization 886

was highest in the 30 ms conventional group (23% of eyes with neovascularization resolved) and lowest in the 30 ms navigated pattern group (5% resolution rate). Neovascularization resolved in 3 of 17 eyes (18%) in the navigated long pulse and 2 of 14 eyes (14%) in conventional long pulse group. There was no statistical difference in the development of neovascularization between the short-pulse-duration groups and long-pulse-duration groups.  NEED FOR ADDITIONAL TREATMENT:

The need for additional treatment included presence/development of vitreous hemorrhage or persistent neovascularization. Table 4 presents the proportion of eyes in each group that required additional therapeutic procedures. One eye in the navigated short pulse group and 1 eye in the conventional short pulse group required vitreoretinal surgery owing to nonclearing vitreous hemorrhage that spared the visual axis. None of the eyes in the long pulse groups required additional surgery. These events were not statistically significantly different between the short-pulseduration (Groups 1 and 2) and Long-Pulse-Duration (Groups 3 and 4) groups (P ¼ .98). Short-pulse-duration groups required 22 procedures and long-pulse-duration groups required 12 procedures. This difference was statistically significant (P < .05). A trend toward worse outcome (additional procedures) using short-pulse-duration treatments is expressed by slightly increased relative risk of 1.3 compared to the long-pulse-duration treatments (Table 4).

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TABLE 3. Clinical Comparison of Navigated and Conventional Pattern Laser Panretinal Photocoagulation in Proliferative Diabetic Retinopathy: Development vs Resolution vs Persisting Neovascularization per Group 30 ms Navigated Pattern (21 eyes)

30 ms Conventional Pattern (22 eyes)

Baseline

Baseline þ

Baseline



þ

Follow-up



Follow-up

þ 

24% 5%

9% 23%

9% 59%

þ

þ 

100 ms Conventional Pattern (14 eyes)

Baseline 

Follow-up

þ 

5% 46%

100 ms Navigated Pattern (17 eyes)

þ



36% 14%

0% 50%

Follow-up

47% 18%

0% 35%

þ 

þ ¼ present;  ¼ absent; Upper left box ¼ nonresolved neovascularization; Upper right box ¼ developed neovascularization; Lower left box ¼ resolved neovascularization; Lower right box ¼ unchanged.

TABLE 4. Clinical Comparison of Navigated and Conventional Pattern Laser Panretinal Photocoagulation in Proliferative Diabetic Retinopathy: Required Additional Laser and Surgical Treatment Pulse

Pattern

Number of Additional PRP (%)

Number of Required Surgeries

30 ms 30 ms 100 ms 100 ms

Navigated pattern Conventional pattern Navigated pattern Conventional single spot

10 (47%) 10 (45%) 7 (41%) 5 (35%)

1 1 0 0

Relative Risk of Additional Procedure

1.3 (Increased risk) 1.3 (Increased risk) 1.1 (No increased risk) Control group

PRP ¼ panretinal photocoagulation.

 TREATMENT TIME: TABLE 5. Clinical Comparison of Navigated and Conventional Pattern Laser Panretinal Photocoagulation in Proliferative Diabetic Retinopathy: Treatment Time (Seconds per 100 Shots) and Pain Score Pulse

Pattern

Treatment Time

Pain Scorea

30 ms 30 ms 100 ms 100 ms

Navigated pattern Conventional pattern Navigated pattern Conventional single spot

21 6 30 s 78 6 28 s 115 6 27 s 156 6 51 s

1.0 6 0.31 2.0 6 0.65 1.5 6 0.56 3.8 6 2.10

a

Treatment time was consistently shorter in the groups that underwent navigated pattern treatment (Groups 1 and 3) compared to groups without navigated pattern treatment (Groups 2 and 4). Treatment time was statistically significantly lower using the navigated long pulse pattern compared to a single spot for the long-pulse-duration groups (P ¼ .05).

DISCUSSION

Using Visual Analog Scale (0–10).

PANRETINAL LASER PHOTOCOAGULATION IS THE GOLD

 PAIN SCORE:

The pain score was lower in the navigated short pulse group compared to the conventional short pulse group (P ¼ .1). The pain score was statistically significantly lower in the navigated long pulse group compared to the conventional long pulse group (P ¼ .02). The experience of pain was statistically significantly different using the navigated pattern compared to a single spot for the longpulse-duration groups (Groups 3 and 4) (P < .001) (Table 5).

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standard for the treatment of high-risk PDR.1 A recent study suggests that intravitreal pharmacotherapy may prevent worsening of diabetic retinopathy.17 Multispot pattern lasers are replacing conventional single-spot lasers owing to ease of use and reduced pain. Pattern laser systems can deliver multiple laser applications with a single depression of the foot pedal. The compromise is shortened pulse duration and lower energy delivery to the tissue, resulting in a greater possibility of undertreatments. However, the potential for undertreatment can be mitigated by changing parameters such as spot size, spot spacing, or increasing

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number of laser applications.8,9,18 This new treatment paradigm differs from the ETDRS recommendations using a single-shot long-pulse-duration argon laser.1 Recently, navigated panretinal photocoagulation was introduced with short and long pulse durations, which can be used with multispot application.14 This is possible because of the simultaneous imaging and delivery of multispot patterns to the retinal periphery while compensating for eye movements. Navigated PRP can deliver 100 ms treatments, which, in conjunction with navigated tracking, is a significant advancement in laser delivery technology. Hence, it is now possible for multispot laser delivery to adhere to the ETDRS guidelines. The present study compared the clinical efficacy of new nPRP to conventional pattern PRP for the treatment of high-risk PDR. Adverse events were not recorded in any of the treatments. Care was taken to completely fill in all retinal areas with photocoagulation burns. There was no significant change in visual acuity between baseline and the last follow-up. Measurement of central retinal thickness after PRP was not an objective of this study. Resolution of neovascularization and prevention of further surgical intervention are the most important clinical outcomes for the treatment of PDR. However, a number of factors affect outcomes, including severity of PDR and systemic control of glycemia. We found that there was no statistically signficant development of neovascularization after PRP in all groups. Additionally, no new neovascularization developed following treatment using the ETDRS parameters with 100 ms pulse duration. Three eyes (1 eye in Group 1 and 2 eyes in Group 2) that underwent short-pulse-duration treatment (30 ms) developed new neovascularization. However, this outcome was not statistically different compared to long-pulse-duration groups (100 ms). In this study we found that the greatest resolution of neovascularization was in eyes that underwent conventional pattern laser with short pulse duration (Group 2, 23% resolution). However, this outcome was not significantly different from the long-pulse-duration groups (Group 3, 18% resolution; Group 4, 14% resolution). Additionally, we found that 46% of eyes in the shortpulse-duration groups (Groups 1 and 2) had persistent neovascularization, compared to 28% of eyes in the longpulse-duration groups (Groups 3 and 4). These outcomes concur with Chappelow and associates’8 comparison of conventional pattern laser (pulse duration 20 ms) to conventional single-spot argon laser (pulse duration 200 ms). Chappelow and associates reported that 73% of eyes had persistent or recurrence of neovascularization in the short-pulse-duration group, compared to 34% eyes in the conventional argon laser group. We found that the short-pulse-duration groups required statistically significantly more retreatments compared to the long-pulse-duration groups (P < .05), despite the lack 888

of statistical differences among individual groups. None of the eyes in the long-duration groups required vitreoretinal surgery, compared to 2 eyes that required vitrectomy in the short-duration groups. Additionally, the relative risk was 1.3 times greater for patients in the short-pulseduration groups to undergo additional surgeries or repeat laser treatments compared to the long-pulse-duration groups. Based on these observations, treatment with longer pulse duration may result in better control of the disease compared to short-pulse-duration treatments with adjusted parameters. In a study comparing standard (long-duration) and short-pulse PRP, Nagpal and associates7 reported that only 4 of 60 eyes in a solid-state green laser group (200 ms) and 2 of 60 eyes in a conventional pattern scan laser group (20 ms) required additional treatment. These outcomes are lower than those of the present study. The differences between studies are likely attributable to differences in the study samples. For example, we included only patients with high-risk PDR and excluded severe nonproliferative retinopathy, whereas Napgal and associates7 included cases of nonproliferative retinopathy. Additionally, the severity of PDR differed between our study and that of Nagpal and associates.7 The Manchester Pascal Study Group evaluated eyes with moderate PDR and found no significant differences between the effects of standard single-spot multisession vs multispot single-session PRP laser on PDR activity.18 In their cohort,18 28% of eyes showed regression with short-pulse-duration multispot PRP after a single session,19 which is comparable to our results for the short-pulse-duration groups (23%). The Manchester Pascal Study Group18 found that both groups required additional PRP, which is similar to the findings of the current study, especially for the short-pulse-duration groups. The Manchester Pascal Study Group used comparable laser spot size and power but smaller spacing between spots. Laser dosimetry in PRP is still evolving in order to mitigate undertreatment and overtreatment. In the current study, patients who underwent navigated pattern laser treatment experienced less pain than those undergoing conventional laser treatment. The reduction in pain and discomfort could be attributable to the infrared imaging’s causing less photostimulation compared to the white light with standard laser. Additionally, sudden treatments may not trigger repeated pain sensation compared to single-spot treatments. The protocol did not avoid treatment in the horizontal meridians, close to the long posterior ciliary nerves, which could be an additional source of pain. However, complete PRP was applied to eyes in all treatment arms, thus standardizing the laser delivery protocol and minimizing confounders. Treatment times were comparable, with some trends favoring navigated treatments. Limitations of our study include the relatively small sample size of each group, resulting in a lack of statistical difference for some comparisons. We did not correlate the treatment effect with medical risk factors such as

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hypertension and cholesterol levels, but all of our patients were largely uncontrolled for numerous risk factors. However, we have mitigated some of the drawbacks of this study by prospective enrollment and randomization. Additionally, the surgeons had extensive experience with both lasers, preventing an effect of a learning curve.

In summary, this prospective randomized trial demonstrates better clinical efficacy of PRP with 100 ms compared to 30 ms treatments using both conventional and navigated pattern lasers. The ability to use long-pulse-duration navigated pattern treatments broadens therapeutic options for PRP for proliferative diabetic retinopathy.

ALL AUTHORS HAVE COMPLETED AND SUBMITTED THE ICMJE FORM FOR DISCLOSURE OF POTENTIAL CONFLICTS OF INTEREST and the following were reported. Dr Arevalo is a consultant for Second Sight LLC and Alcon Laboratories and has received payments for lectures from Iridex, Optos Inc, Novartis Pharmaceuticals, Alimera Sciences, Second Sight LLC, and Alcon Laboratories. Dr Kozak has received payment for lecture from Bayer (Leverkusen, Germany) and meeting travel expense from OD-OS, Inc (Teltow, Germany). The authors indicate no funding support. Contribution of authors: design (J.C., I.K.) and conduct of the study (J.C., S.S., A.M., V.G., J.F.A., I.K.); collection (J.C., I.K.), management (J.C., I.K.), analysis (J.C., I.K.), and interpretation of the data (J.C., S.S., A.M., V.G., J.F.A., I.K.); and preparation, review, or approval of the manuscript (J.C., S.S., A.M., V.G., J.F.A., I.K.).

REFERENCES 1. The Diabetic Retinopathy Study Research Group. Photocoagulation treatment of proliferative diabetic retinopathy: clinical application of Diabetic Retinopathy Study (DRS) findings, DRS Report Number 8. Ophthalmology 1981;88(7):583–600. 2. Early Treatment Diabetic Retinopathy Study Research Group. Photocoagulation for diabetic macular edema: ETDRS report number 1. Arch Ophthalmol 1985;103(12):1796–1803. 3. Early Treatment Diabetic Retinopathy Study Research Group. Photocoagulation for diabetic macular edema: ETDRS report number 4. Int Ophthalmol Clin 1987;27(4):265–272. 4. Blumenkranz MS, Yellachich D, Andersen DE, et al. Semiautomated patterned scanning laser for retinal photocoagulation. Retina 2006;26(3):370–376. 5. Sanghvi C, McLauchlan R, Delgado C, et al. Initial experience with the Pascal photocoagulator: a pilot study of 75 procedures. Br J Ophthalmol 2008;92(8):1061–1064. 6. Muqit MM, Marcellino GR, Gray JC, et al. Pain responses of Pascal 20 ms multi-spot and 100 ms single-spot panretinal photocoagulation: Manchester Pascal Study, MAPASS report 2. Br J Ophthalmol 2010;94(11):1493–1498. 7. Nagpal M, Marlecha S, Nagpal K. Comparison of laser photocoagulation for diabetic retinopathy using 532-nm standard laser versus multispot pattern scan laser. Retina 2010;30(3):452–458. 8. Chappelow AV, Tan K, Waheed NK, Kaiser PK. Panretinal photocoagulation for proliferative diabetic retinopathy: pattern scan laser versus argon laser. Am J Ophthalmol 2012; 153(1):137–142.e2. 9. Alasil T, Waheed NK. Pan retinal photocoagulation for proliferative diabetic retinopathy: pattern scan laser versus argon laser. Curr Opin Ophthalmol 2014;25(3):164–170. 10. Liesfeld B, Amthor KU, Dowell D, et al. Navigating comfortably across the retina. IFMBE Proceedings 2009;25(11): 243–246.

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11. Kozak I, Oster SF, Cortes MA, et al. Clinical evaluation and treatment accuracy in diabetic macular edema using navigated laser photocoagulator NAVILAS. Ophthalmology 2011;118(6):1119–1124. 12. Kernt M, Cheuteu R, Liegl RG, et al. Navigated focal retinal laser therapy using the NAVILASÒ system for diabetic macula edema. Ophthalmologe 2012;109(7):692–698. 13. Kozak I, Kim JS, Oster SF, et al. Focal navigated laser photocoagulation in retinovascular disease: clinical results in initial case series. Retina 2012;32(5):930–935. 14. Chhablani J, Mathai A, Rani P, et al. Comparison of conventional pattern and novel navigated panretinal photocoagulation in proliferative diabetic retinopathy. Invest Ophthalmol Vis Sci 2014;55(6):3432–3438. 15. R Development Core Team. R: A language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing; 2008. Available at http://www.Rproject.org. Accessed August 2, 2014. 16. Sachs L, Hedderich J. Angewandte Statistik. Methodensammlung mit R. Berlin: Springer Berlin; 2009:1–212. 17. Bressler SB, Qin H, Melia M, et al; Diabetic Retinopathy Clinical Research Network. Exploratory analysis of the effect of intravitreal ranibizumab or triamcinolone on worsening of diabetic retinopathy in a randomized clinical trial. JAMA Ophthalmol 2013;131(8):1033–1040. 18. Muqit MM, Marcellino GR, Henson DB, et al. Single-session vs. multiple-session pattern scanning laser panretinal photocoagulation in proliferative diabetic retinopathy: The Manchester Pascal Study. Arch Ophthalmol 2010;128(5): 525–533. 19. Muqit MM, Marcellino GR, Henson DB, Young LB, Turner GS, Stanga PE. Pascal panretinal laser ablation and regression analysis in proliferative diabetic retinopathy: Manchester Pascal Study Report 4. Eye (Lond) 2011;25(11): 1447–1456.

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Clinical efficacy of navigated panretinal photocoagulation in proliferative diabetic retinopathy.

To compare the clinical efficacy of navigated pattern and conventional slit-lamp pattern panretinal photocoagulation (PRP)...
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