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Biomedical subjects

S P Percival

Publications and source records attributed to S P Percival.

At least 19 recordsLinked to original sources
PubMed1999

12 year results of a prospective trial comparing poly(methyl methacrylate) and poly(hydroxyethyl methacrylate) intraocular lenses.

PURPOSE: To compare long-term biocompatibility of single-piece poly(methyl methacrylate) (PMMA) and poly(hydroxyethyl methacrylate) (P-HEMA) intraocular lenses (IOLs). SETTING: District General Hospital, United Kingdom. METHODS: In a prospective trial of 250 eyes that had uncomplicated extracapsular cataract extraction, 2 groups of 125 eyes each were matched for age and sex. One group received single-piece looped PMMA IOLs and the other, single-piece solid-haptic P-HEMA IOLs. In all eyes, the IOLs were implanted in the capsular bag at the time of surgery using the envelope technique. RESULTS: Twelve years after surgery, 75 eyes were available for examination. In the PMMA group (40 eyes), 50% had a visual acuity of 20/20 and 50% had intact capsules, many of them with a degree of fibrosis. In the P-HEMA group (35 eyes), 71% had an acuity of 20/20 and 80% had intact capsules (P = .0085). CONCLUSION: In the long term, biocompatibility was better in the P-HEMA group than in the PMMA group.

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PubMed1999

The benefits of phacotrabeculectomy using 10-0 polyglactin sutures.

PURPOSE: To determine the efficacy of a small scleral flap sutured with 10-0 polyglactin (Vicryl). METHODS: One hundred and sixty-five eyes underwent clear cornea punch trabeculectomy under a 5.0 mm wide scleral flap that was closed with two 10-0 Vicryl sutures after phacoemulsification and insertion of a single-piece PMMA lens. Complications, tonometric and visual results were assessed at regular intervals. Statistical analysis was by Fisher's exact test. RESULTS: One hundred eyes that were followed for 1 year showed a mean intraocular pressure (IOP) of 14.7 mmHg, representing a fall of 36.5%. At 2 years the mean IOP was 16 mmHg (33 eyes). At final follow-up 87% had a corrected acuity of 6/12 or better and 96% had IOPs below 22 mmHg without additional medication. Complications included 11.5% fibrin reaction, 5.5% secondary hyphaema and 7.3% hypotony. There was a significant association of fibrin with both hypotony and pseudoexfoliation. CONCLUSIONS: These mid-term results show that 10-0 Vicryl compares favourably with other suture materials the results of which have been reported, and obviates the need for routine use of antimetabolites or for post-operative manipulations at the slit-lamp.

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PubMed1998

Phacotrabeculectomy: comparison of results from 3.5- and 5.2-mm incisions.

BACKGROUND AND OBJECTIVE: To compare the intraocular pressure control, visual results, and astigmatic results of 3.5-mm and 5.2-mm incisions following phacotrabeculectomy with 12 months of follow-up. PATIENTS AND METHODS: Fifty eyes underwent clear cornea punch trabeculectomy under a 5.0 x 2.5-mm scleral flap, closed with two 10-0 polyglactin sutures. The first 25 eyes underwent wound extension to 5.2 mm for insertion of a single-piece polymethylmethacrylate (PMMA) lens. The next 25 eyes underwent wound extension to 3.5 mm for insertion of a folded silicone lens. RESULTS: The mean intraocular pressure decrease from the preoperative level was 7.6 mm Hg in the 3.5-mm incision group and 7.8 mm Hg in the 5.2-mm incision group. One patient required continued medication. The best-corrected visual acuity was 20/40 or better in 86% of the patients, with no significant difference between the groups. The mean "with the wound" induced astigmatism showed no statistical difference between the two groups. CONCLUSIONS: The use of 10-0 polyglactin appears to aid filtration, yet minimizes hypotony or the need for antimetabolites. For surgeons who wish to reduce costs without compromising results during phacotrabeculectomy, there is merit in considering a 5.2-mm incision; moreover, the more rigid single-piece PMMA lens appears to be associated with fewer complications in the immediate postoperative period.

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PubMed1994

Preliminary results with a new hydrogel intraocular lens.

The merits of hydrogel as an intraocular lens material are that it is soft, foldable, hydrophilic, autoclavable and more biocompatible than polymethylmethacrylate (PMMA). Twenty eyes were implanted with a new hydrogel design after phacoemulsification. Fifty per cent achieved a corrected acuity of 6/5 and all achieved 6/9 with correction. Results confirmed an excellent biocompatibility of the material but two cases of asymptomatic decentration indicated the occasional instability within the capsular sac. For best results the hydrogel requires an intact capsulorrhexis with a diameter between 4.5 and 5.0 mm.

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PubMed1993

Prospectively randomized trial comparing the pseudoaccommodation of the AMO ARRAY multifocal lens and a monofocal lens.

A prospective trial was set up to compare pseudoaccommodation. Fifty patients were randomized into two groups. Group 1 comprised 25 patients who had a monofocal implant and a postoperative refractive aim of -0.3 to -1.3 diopter (D) spherical equivalent and an astigmatic component between 1.0 and 1.75 D cylinder. Group 2 comprised 25 patients who had a new multizone refraction style multifocal implant and a postoperative refractive aim of -0.5 to +0.5 D spherical equivalent and an astigmatic component of less than 1.0 D cylinder. Eighty percent of postoperative refractions in Group 1 and 88% in Group 2 were within 0.5 D either side of the refractive aim. Forty-eight percent of Group 1 and 72% of Group 2 could see both 20/40 and J3 unaided. Four percent of Group 1 and 84% of Group 2 could read J2 with the distance correction. Sixteen percent of Group 1 and 48% of Group 2 could read J2 at 25 cm unaided (P = .03). Sixty-four percent of Group 1 and 88% of Group 2 stated they could manage daily activities without glasses. However, 88% of Group 1 and 52% of Group 2 requested reading glasses to improve clarity of the smallest print.

Accommodation, Ocular↗
PubMed1993

Heparin-modified lenses for eyes at risk for breakdown of the blood-aqueous barrier during cataract surgery.

To determine the appropriateness of heparin-surface-modified (HSM) lenses in eyes at risk for breakdown of the blood-aqueous barrier, 36 consecutive patients with cataracts associated with chronic recurrent or past uveitis had extracapsular cataract extraction and insertion of an HSM posterior chamber one-piece intraocular lens (IOL). Examinations for implant precipitates (IPs), fibrin membranes, IOL synechias, and visual outcome were done postoperatively. Results show that despite a recurrence of overt uveitis with keratic precipitates in 13 eyes (36.1%), IPs were seen in only six eyes (16.6%) and were generally small and few in number. An acute postoperative fibrin reaction, which is related to blood-aqueous barrier breakdown, occurred in nine eyes. Implant synechias were found in three eyes. We found that HSM provided a cell-free IOL surface in the majority of eyes at high risk for blood-aqueous barrier breakdown and uveitis. Heparin surface modification does not prevent complications but tends to protect the IOL from inflammation changes that might otherwise occur.

Adult↗
PubMed1992

Prospective audit comparing ambulatory day surgery with inpatient surgery for treating cataracts.

OBJECTIVES: To compare the cost effectiveness and safety of inpatient cataract surgery (with one night in hospital postoperatively) with ambulatory day case surgery under local anaesthesia. DESIGN: Prospective study of patients receiving inpatient (group 1) or day case (group 2) surgery. SETTING: One ophthalmic surgical firm. PATIENTS: 100 patients in each group, excluding those with coexisting ocular conditions, contraindications to local or request for general anaesthesia, ill health, or lack of agreed minimum social care; four patients died during follow up. INTERVENTIONS: Envelope method and implantation of the posterior chamber lens into the capsular sac in both groups. MAIN MEASURES: Perioperative complications, operating and turnover times, visual outcome at three to six days and 10 weeks to six months after operation, patient satisfaction (according to self administered questionnaire) at three to six days, and total costs (1989 salaries) for both groups. RESULTS: Patients in both groups did not differ significantly in age or sex, perioperative complications, visual outcome (6/9 or better in 78 patients in group 1 and 75 in group 2 at one month after operation and 6/12 or better in 92/98 in group 1, 90/98 in group 2 at final follow up), or patient satisfaction. The mean total cost per patient for group 1 patients was 365.99 pounds and for group 2, 221.62 pounds. CONCLUSIONS: Day case surgery for cataract is safe and more cost effective. IMPLICATIONS: Day case surgery should be recommended to increase availability of cataract surgery and thereby improve quality of life for more patients.

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PubMed1991

Comparative analysis of three prospective trials of multifocal implants.

A clinical analysis of best cases four to 12 months postoperatively was made to assess the function of 47 3M multifocal implants, 40 Iolab multifocal implants and 24 AMO multifocal implants. Overall 86 (79%) eyes could see 6/12 and N6 unaided. The multifocal function for each lens worked well for distance, intermediate and near in the majority but an increase in depth of field was at a cost of reduced resolution efficiency. The 3M lens was associated with symptoms of poor optical quality in 29.8% and with an inability to read N5 with correction in 17%. The Iolab lens provided better reading vision but less good distant vision than the other types and was associated with symptoms of poor optical quality in 15%. Many of these had a pupil diameter greater than 3.5 mm. The AMO lens gave a poorer unaided reading vision than the other lens types but had the lowest incidence of optical symptoms.

Humans↗
PubMed1989

Prospective study of the new diffractive bifocal intraocular lens.

The visual results of 55 bifocal lens implantations are compared with 55 matched PMMA monofocal implantations. 84% of the eyes with bifocal implants compared with 20% of the eyes with monofocal implants could read N8 or better with the distance correction (p less than 0.001). 52% of +/- 3.5D bifocal eyes could read N5 with the distance correction. The mean reading addition for a near point of 25 cm was 0.3D in the bifocal group and 2.2D in the monofocal group. 20% of eyes with bifocal implants could not be corrected to N5 at a comfortable distance (p = 0.005). It was found that the clear advantages of this bifocal lens must be countered in a minority by a loss in quality of vision particularly for reading.

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PubMed1989

Intraocular lens design and the inhibition of epithelium.

Of 1170 eyes implanted with posterior chamber lenses between 1981 and 1986 and having intact capsules at surgery, 1015 were examined two years after surgery, 741 were examined three years after surgery, and 308 were examined five years after surgery. At three years the capsulotomy rate for epithelium was 25% for 263 'lasergap' lenses, 2.4% for 296 convex posterior lenses, 8.2% for 73 planoposterior lenses with angulated loops. The highly significant difference for lasergap design, whether ridged, meniscus, or bossed, is of immediate interest to surgeons concerned with minimising the need for secondary capsulotomy. The two-year follow-up of soft hydrogel lenses suggested that these lenses also do not significantly retard the ingrowth of epithelium.

Adult↗
PubMed1988

Analysis of the need for secondary capsulotomy during a five-year follow-up.

From 783 consecutive extracapsular cataract extractions with intact posterior capsules at the close of surgery, 655 eyes were available for examination three years after surgery and 447 eyes were available five years after surgery. By five years postoperatively, the need for secondary capsulotomy was 49% of 67 eyes that had not received an implant, 23% of 159 eyes that had received a Binkhorst iridocapsular lens, and 13% of 221 eyes that had received a posterior chamber lens. Among posterior chamber lenses, the surface area of the implant was considered to be a more important factor in inhibiting capsule opacification than posterior vaulting of the lens. Posterior vaulting was associated with a lower incidence of epithelialization but a higher incidence of capsular fibrosis. A small subgroup of 19 glaucoma triple procedures examined at three years showed a significantly higher incidence of capsulotomy (21.0%) than the other 369 posterior chamber lens implantations examined at three years (6.8%).

Adult↗
PubMed1988

Hydrogel intraocular lens experience with endocapsular implantation.

The experience is presented of three independent surgeons using Hydrogel posterior chamber intraocular lenses in a combined series of 157 endocapsular cataract extractions. One hundred and fifty of these eyes were examined after a minimum follow-up period of one year and 92.0% achieved visual acuity of 6/12 or better, and 98.6% achieved this if pre-existing pathology was excluded. Insertion of this lens has proved to be simple, the adaptions of technique required are described and the complications are presented and analysed.

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PubMed1988

Radial keratotomy: where did it go wrong?

A prospective study was set up to determine the effectiveness, predictability, stability, safety and feasibility within the National Health Service of radial keratotomy. The methods adopted include a new simplified guide to surgery with a predicted accuracy in 84 of 100 operations. Ninety-six percent of eyes with myopia of -6.0D or less preoperatively were seeing 6/12 or better six months after surgery. Refraction remained stable within a range 0.5D spherical equivalent between the first and sixth postoperative months in 96%, between the first and twelfth postoperative months in 90% and between the first and second years in 100% of eyes examined. There were no cases of progressive hypermetropia. Sixty-four percent of the 61 patients admitted to postoperative symptoms. Three percent of eyes lost best corrected vision. The disappointments were few but were analysed in detail. The least reliable were found to be associated with the higher myopes requiring a 3.0 mm clear optical zone.

Adult↗
PubMed1987

Early experience with soft hydrogel lens implants.

A new material which more closely mimics the properties of living tissue than polymethylmethacrylate is under investigation. Twelve hydrogel lenses were placed into the ciliary sulcus following the standard nucleus extraction technique and 38 were placed into the lens capsule using the endocapsular technique. Six months following surgery 66 per cent of sulcus fixated lenses were found to have both haptics in the sulcus and 76 per cent of capsule fixated lenses were found to have both haptics encapsulated. The hydrogel lens was found to be well tolerated within the eye with 32 per cent of eyes achieving a visual acuity of 6/5 and 94 per cent achieving 6/12 or better.

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PubMed1987

Redefinition of high myopia: the relationship of axial length measurement to myopic pathology and its relevance to cataract surgery.

Owing to growing confusion over the true incidence of RD in HM after cataract surgery, a new definition for HM has been formulated based on measurement of axial length. Of 38 noncataractous phakic eyes with treated RD, 45% were found to have axial lengths more than 1 mm longer than would be expected from the eye's refraction. Of 180 moderate to highly myopic eyes examined 2 years after extracapsular extraction with lens implantation, 2 were found to have developed RD. Using the historic definition for HM by refraction (spectacle equivalent of -6.0 dptr or more), the incidence of RD was found to be 1/62 eyes (1.6%) but using the improved definition of axial length 26.5 mm or more, the incidence was found to be 2/49 eyes (4.1%). Both these studies suggested that axial length, in addition to myopic pathology, is a factor associated with RD and that a definition of HM based on axial length is more appropriate than that based on refraction.

Cataract Extraction↗
PubMed1985

Results of a clinical trial of sodium hyaluronate in lens implantation surgery.

The results from a four-year clinical trial on the use of sodium hyaluronate (Healon) are presented. Six hundred three consecutive primary lens implantations were performed: 500 after extracapsular cataract extraction and 103 after intracapsular cataract extraction. The safety and efficacy of Healon were analyzed by examining postoperative ocular hypertension, uveitis, visual acuity, and endothelial cell loss. The results of the trial confirm that Healon is safe and effective and, provided it is not used in excessive quantities, free from serious side effects.

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