Stephen J. Charles

Initial experience with the Pascal photocoagulator: a pilot study of 75 procedures.

Background: The Pascal is a semiautomated photocoagulator that delivers a pattern array of multiple burns in a rapid predetermined sequence with a single foot pedal depression. Each burn is reduced to 10 or 20 ms to achieve this. The authors report their early experience with this system. Methods: 75 procedures done in 60 patients divided into four groups—group A, patients undergoing panretinal photocoagulation (PRP); group B, patients undergoing focal or modified grid macular laser; group C, patients undergoing macular grid and group D, patients undergoing retinopexy—were retrospectively studied. Results: 31/34 procedures in group A, 24/26 procedures in group B, 5/7 procedures in group C and all eight patients in group D had successful outcomes. Significantly higher powers were required with the Pascal than with conventional laser (p<0.001) in eyes that underwent PRP and focal/modified grid macular treatment with both systems. Single session PRP was successfully performed in five patients, and five were successfully treated with a macular grid using pattern arrays only. No adverse events were noted. Conclusion: Although the shorter pulse duration of the Pascal necessitates the use of a higher power, it is not associated with adverse effects. The results here suggest that the Pascal photocoagulator is safe and effective, and offer several potential advantages related to the brief exposure time.

Pain responses of Pascal 20 ms multi-spot and 100 ms single-spot panretinal photocoagulation: Manchester Pascal Study, MAPASS report 2.

Aims To evaluate pain responses following Pascal 20 ms multi-spot and 100 ms single-spot panretinal photocoagulation (PRP). Methods Single-centre randomised clinical trial. 40 eyes of 24 patients with treatment-naive proliferative diabetic retinopathy randomised to 20 and 100 ms PRP under topical 0.4% oxybuprocaine. A masked grader used a pain questionnaire within 1 h (numerical pain score (NPS)) and 1 month after treatment (numerical headache score (NHS)). Primary outcome measure was NPS immediately post-PRP. Secondary outcome measures were mean NHS scores and levels of photophobia reported within 4 weeks of primary PRP. Results Mean laser fluence was significantly lower using 20 ms PRP (4.8 J/cm2) compared to 100 ms PRP (11.8 J/cm2; p<0.001). Mean NPS scores for treatment were 2.4 (2.3) (mild) for 20 ms PRP group compared to 4.9 (3.3) (moderate) in 100 ms PRP group—a significant difference (95% CI 4.3 to 0.68; p=0.006). Mean NHS score within 1 month was 1.5 (2.7) in 20 ms PRP group compared to 3.2 (3.5) in the 100 ms PRP group (p<0.05). The median duration of photophobia after 20 ms PRP was 3 h, and significantly less compared to 100 ms PRP after which 72 h of photophobia was reported (p<0.001). Conclusions Multi-spot 20 ms PRP was associated with significantly lower levels of anxiety, headache, pain and photophobia compared to 100 ms single-spot PRP treatment. Possible reasons include lower fluence, shorter-pulse duration, and spatial summation of laser nociception with multi-spot Pascal technique.

Optos-guided pattern scan laser (Pascal)-targeted retinal photocoagulation in proliferative diabetic retinopathy

Purpose:  To investigate the clinical effects and safety of targeted pattern scan laser (Pascal) retinal photocoagulation (TRP) in proliferative diabetic retinopathy (PDR).

In Vivo Laser-Tissue Interactions and Healing Responses From 20- vs 100-Millisecond Pulse Pascal Photocoagulation Burns

OBJECTIVES To compare in vivo burn morphologic features and healing responses of Pascal 20- and 100-millisecond panretinal photocoagulation (PRP) burns in proliferative diabetic retinopathy. DESIGN Prospective randomized controlled trial with 24 eyes assigned to either 20- or 100-millisecond Pascal PRP. Fundus autofluorescence and Fourier domain optical coherence tomography (FD-OCT) were performed 1 hour and 2 and 4 weeks after treatment. Main outcome measures included burn morphologic features on FD-OCT and greatest linear diameter (GLD) of laser burns as evaluated in 6 standard Early Treatment of Diabetic Retinopathy Study photographic fields using autofluorescence. RESULTS The contemporaneous increase in autofluorescence is observed with increasing pulse duration. Differences in mean GLD between 100- and 20-millisecond burns were 63 mum at 1 hour and 198 mum at 4 weeks (P < .001 for both). At 4 weeks, all burns corresponded to defects at the junction of inner and outer segments of photoreceptors (JI/OSP) and apical retinal pigment epithelium. After 4 weeks, the GLD of 20-millisecond burns reduced significantly by 35% (P < .001), with no change in 100-millisecond burns. CONCLUSIONS All burns initially appear as equivalent square-edged, columnar foci of hyperreflectivity in the outer retina. Pascal 20-millisecond burns progressively reduce in size, and this suggests a novel healing response localized to the JI/OSP and apical retinal pigment epithelium. The higher-fluence 100-millisecond burns develop larger defects due to thermal blooming and collateral damage.

Single-session vs multiple-session pattern scanning laser panretinal photocoagulation in proliferative diabetic retinopathy: The Manchester Pascal Study.

OBJECTIVE To investigate the effects of pattern scanning laser (Pascal; OptiMedica, Santa Clara, California) multispot panretinal photocoagulation given in a single-session (SS-PRP) vs single-spot multiple-session PRP (MS-PRP) on proliferative diabetic retinopathy (PDR). METHODS Single-center, randomized clinical trial of 40 eyes. Proliferative diabetic retinopathy was treated with a 400-mum spot size in 1500 burns given either as Pascal in 20-millisecond SS-PRP or in 3 sessions (100-millisecond MS-PRP) during a 4-week period. Visual acuity, central subfield retinal thickness (CRT), and 24-2 Swedish interactive thresholding algorithm visual fields were recorded at baseline and 4 and 12 weeks. MAIN OUTCOME MEASURES Central subfield retinal thickness, mean deviation, and PDR grade at 12 weeks. RESULTS There was a significant increase in mean CRT with MS-PRP (22 mum at 4 weeks, 95% CI, -32.25 to -10.75; 20 mum at 12 weeks, 95% CI, -28.75 to -10.82; P < .001) and no significant increase in the SS-PRP group. The mean deviation increased significantly in the SS-PRP group after 4 weeks (0.73 dB, P = .048), with no significant changes in either group at other points. A positive effect on PDR was observed in 74% of eyes in the SS-PRP group vs 53% in the MS-PRP group (P = .31). Mean treatment time for SS-PRP was 5.04 minutes (SD, 1.5 minutes) compared with 59.3 (SD, 12.7 minutes) in the MS-PRP group (P < .001). CONCLUSIONS There were no adverse outcomes (CRT, visual acuity, or visual field) from using multispot SS-PRP vs single-spot MS-PRP at 12 weeks postlaser, and treatment times were significantly shorter for multispot SS-PRP. Pascal SS-PRP was as effective as MS-PRP in the treatment of PDR. APPLICATION TO CLINICAL PRACTICE Twenty-millisecond Pascal SS-PRP may be safely and rapidly performed in 1500 burns with a similar efficacy to conventional MS-PRP. TRIAL IDENTIFIER: Research and Development Office PIN R00037, Central Manchester University Hospitals Foundation Trust.

Fundus autofluorescence and Fourier-domain optical coherence tomography imaging of 10 and 20 millisecond Pascal retinal photocoagulation treatment

Aim: To report the evolution of pattern scanning laser (Pascal) photocoagulation burns in the treatment of diabetic retinopathy, using Fourier-domain optical coherence tomography (FD-OCT) and fundus autofluorescence (AF), and to evaluate these characteristics with clinically visible alterations in outer retina (OR) and retinal pigment epithelium (RPE). Methods: Standard red-free and colour fundus photography (FP), FD-OCT, and fundus camera-based AF were performed in 17 eyes of 11 patients following macular and panretinal photocoagulation (PRP). Results: One hour following Pascal application, visibility of threshold burns on FP was incomplete. AF enabled visualisation of complete treatment arrays at 1 h, with hypoautofluorescence at sites of each laser burn. AF signals accurately correlated with localised increased optical reflectivity within the outer retina on FD-OCT. AF signals became hyperautofluorescent at 1 week, and corresponded on FD-OCT to defects at the junction of the inner and outer segments of the photoreceptors (JI/OSP) and upper surface of RPE. A 10 ms macular laser pulse produced a localised defect at the level of JI/OSP and RPE. Macular and 20 ms PRP burns did not enlarge at 1 year’s and 18 months’ follow-up respectively. Conclusions: We report the in vivo spatial localisation and clinical correlation of medium-pulse Pascal photocoagulation burns within outer retina and RPE, using high-resolution FD-OCT and AF. Ophthalmoscopically invisible and threshold Pascal burns may be accurately localised and mapped by AF and FD-OCT, with monitoring over time.

Scleral hydraulic conductivity and macromolecular diffusion in patients with uveal effusion syndrome

PURPOSE To determine whether uveal effusion syndrome (UES) is caused by altered scleral permeability to water and large molecules. METHODS Transscleral water movement was measured using surgically removed sclera clamped in a modified Ussing chamber and connected to a water column set at intraocular pressure. Sclera was also clamped between two hemichambers, and transscleral diffusion of FITC-dextrans (4.4-77 kDa) was measured with a spectrophotometer. Clinical data were prospectively collected using postal questionnaires. RESULTS Ten patients (mean age, 63 years; mean spherical equivalent, +4.7 D) had a median preoperative visual acuity of 0.20 that improved to 0.33 after surgery. Nine eyes showed visual improvement, three worsened, and two were unchanged. Histology showed disorganization of collagen fibrils, with amorphous deposits expanding the interfibrillary spaces. The mean thickness (+/-1 SD) of the excised scleral specimens was 585 +/- 309 microm, and the mean specific hydraulic conductivity was 23.9 +/- 27.5 x 10(-14) cm(2), compared with 5.8 +/- 3.9 x 10(-14) cm(2) in age-matched control specimens (P = 0.068). Three specimens had hydraulic conductivity above the 95% CI of the controls. Control eyes showed a significant reduction in diffusion coefficient (D) with age. Eyes had a mean D of 5.69 +/- 5.35 x 10(-8) cm(2) x s(-1), similar to control eyes (6.14 +/- 2.40 x 10(-8) cm(2) x s(-1), 20 kDa dextran). In one eye, the result was higher than the 95% CI of the control; in three, it was lower. CONCLUSIONS UES is not caused by reduced scleral hydraulic conductivity, which tends to be higher than expected. Reduced macromolecular diffusion may impede the normal transscleral egress of albumin with subsequent osmotic fluid retention in some, but not all eyes.

Objective morphological assessment of macular hole surgery by scanning laser tomography

AIM To assess the morphological change in retinal topography using a scanning laser tomographer following macular hole surgery. To compare the results of scanning laser tomography with clinical evaluation and visual function assessment. METHODS The sample for this pilot study comprised four eyes exhibiting different stages of macular hole formation preoperatively. Subjects were assessed preoperatively and at 1 and 3 months postoperatively. Each assessment included visual acuity, letter contrast sensitivity, clinical examination (including automated static perimetry), and scanning laser tomography. The Heidelberg retina tomograph (HRT) was used to acquire digitised scanning laser tomography images of the macula (10° and 20° fields). Surgery essentially comprised vitrectomy, peeling of the posterior hyaloid face, if still attached, and intraocular gas tamponade. The magnitude and significance of topographic change were determined postoperatively using the HRT topographic difference facility. RESULTS Topographic difference analysis of the right and left eyes of case 1 showed a significant reduction in the height of the retina postoperatively. Topographic difference analysis of case 2 showed no significant change in topography. Topographic difference analysis of case 3 showed a significant increase in the height of the retina postoperatively. Scanning laser tomography agreed with clinical assessment based upon fundus biomicroscopy in three of the four eyes studied; the postoperative closure of the stage 2 macular hole (as noted by clinical assessment) proved to be too small to reach statistical significance. Scanning laser tomography agreed with the assessment of visual function in two eyes; the agreement between scanning laser tomography and visual function depends, in part, on the stage of development of the macular hole. CONCLUSION Scanning laser tomography provides an objective evaluation of the outcome of macular hole surgery. Studies employing larger sample sizes are required to fully determine the clinical worth of the technique.

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.

Displacement of nuclear fragments into the vitreous complicating phacoemulsification surgery in the UK: incidence and risk factors

Aims: To study the epidemiology and risk factors contributing to displacement of nuclear fragments into the vitreous (DNFV) complicating phacoemulsification in the UK. Methods: Cases were collected prospectively between March 2003 and March 2004 by active surveillance through the British Ophthalmological Surveillance Unit (BOSU). Case–control analysis of risk factors was performed by visiting 10 randomly selected centres using a total of 521 cases of uncomplicated phacoemulsification. Validation analysis to assess under-reporting was performed in a total of 13 randomly selected units. Results: 610 cases of DNFV were confirmed during the reporting period. The estimated incidence of DNFV was 0.19–0.28%. The group with complications was significantly older than the control group (mean 76.8 vs 74.3 years: p<0.001). Significant preoperative risk factors were posterior synechiae (5.1% vs 2.2%), incomplete pupil dilation (59.5% vs 8.8%), pseudoexfoliation (5.6% vs 1.4%) and previous vitrectomy (7.8% vs 2.2%). Significant operative variables related to surgical experience, topical (14.3% vs 3.1%) and sub-Tenon’s (51.4% vs 37.2%) anaesthesia, and requirement for vision blue (trypan blue ophthalmic solution) (13.7% vs 2.4%). Conclusions: The estimated incidence of DNFV during phacoemulsification surgery in the UK is two or three per 1000 operations. Risk factors have been identified that should help to guide case selection for phacoemulsification surgery and modify techniques.