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Biomedical subjects

I A Pearce

Publications and source records attributed to I A Pearce.

15 recordsLinked to original sources
PubMed2005

Visual loss following removal of intraocular silicone oil.

AIM: To investigate the cause of visual loss following removal of intraocular silicone oil in patients who underwent vitrectomies for retinal detachment or giant retinal tear. METHODS: The clinical records of three cases with visual loss following removal of silicone oil were reviewed. Investigations carried out included fundus fluorescein angiogram, optical coherence tomography, and electrophysiological studies. RESULTS: Visual acuities dropped from 6/9 to 6/36 in two cases and 6/24 to 3/24 in the third. None of the three cases had macula detachment at any stage. Fundus fluorescein angiogram and optical coherence tomography were normal in all cases. Pattern electroretinogram showed reduced amplitudes of the P50 and N95 components. Multifocal electroretinogram indicated a selective damage to the central part of the macula. CONCLUSIONS: The results suggest that the abnormality arises predominantly in the central part of the macula, especially the outer and middle layers. However, the exact mechanism still remains obscure.

Adult↗
PubMed2005

A pilot study on the use of a perfluorohexyloctane/silicone oil solution as a heavier than water internal tamponade agent.

AIMS: To report a prospective two centred non-comparative interventional pilot study of a solution of perfluorohexyloctane and silicone oil (Densiron-68) as a heavier than water internal tamponade. METHODS: 42 consecutive patients were recruited. The indications include proliferative vitreoretinopathy, retinal detachments arising from inferior retinal breaks, and inability to posture. RESULTS: The success rate with one operation using Densiron was 81% and with further surgery 93%. At the end of the study all tamponade agents were removed in 90% of patients. Visual acuity improved from mean logMAR of 1.41 (SD 0.64) to 0.94 (SD 0.57), p = 0.001. There was little evidence of dispersion and excessive inflammation. CONCLUSION: This new tamponade agent is being compared to conventional silicone oil in a prospective international randomised trial.

Adult↗
PubMed2002

Vitreous penetration of levofloxacin in the uninflamed phakic human eye.

AIMS: To assess the vitreous penetration of oral levofloxacin (a new fluoroquinolone antibiotic with improved Gram positive activity) in uninflamed phakic eyes. METHODS: 15 patients for macula hole surgery were recruited to the study. 10 received a single 500 mg dose of levofloxacin by mouth preoperatively. Five acted as controls. Serum and undiluted vitreous samples were obtained at surgery and analysed by HPLC. RESULTS: Levofloxacin was detectable 2.5 hours after administration in the vitreous. A peak concentration of 1.6 microg/ml (or mg/l) was measured between 2.5 and 4 hours post-dose. CONCLUSION: Oral levofloxacin reaches the vitreous rapidly in the uninflamed phakic eye. Levels did not reach MIC(90) for the commonest infecting organisms. Nevertheless, levofloxacin would be expected to be active against a higher proportion of infecting organisms than either ciprofloxacin or ofloxacin.

Administration, Oral↗
PubMed2000

Vertical diplopia following local anaesthetic cataract surgery: predominantly a left eye problem?

PURPOSE: Vertical diplopia is an uncommon but disappointing complication of otherwise successful local anaesthetic cataract surgery. We studied strabismus patterns in a group of such patients to identify the nature and extent of extraocular muscle involvement. METHODS: A retrospective review identified 15 cases of vertical diplopia following local anaesthetic cataract surgery between July 1994 and January 1998. Peribulbar anaesthesia was used in all cases and given by right-handed professionals. RESULTS: All cases had otherwise successful cataract surgery (mean age 80.5 years; median pre-operative VA 6/18; median post-operative VA 6/9). The mean level of vertical diplopia was 7.2 prism dioptres (PD) in the primary position (range 2-25 PD). The left inferior rectus (IR) was paretic in 6 cases and restricted in 5 cases. The left superior rectus (SR) was not affected in any of the cases. The right IR was restricted in a single case. The right SR was paretic in 2 cases and restricted in a single case. None of the cases had clinical involvement of the oblique muscles. Eleven of the cases were managed successfully with prisms. Two of the cases required strabismus surgery. CONCLUSIONS: The incidence of left eye extraocular muscle involvement was greater than right eye involvement, although this did not reach statistical significance (73% vs 27%; p = 0.075). This may be due to the more difficult access of right-handed individuals giving left eye peribulbar injections with the needle tract being directed more closely to the muscle cone. The IR muscle is more commonly affected than the SR (80% vs 20%; p = 0.019). An equal incidence of paretic and restricted rectus muscle pathology was found in this study (53% vs 47%; p = 0.818). The exact aetiology of muscle injury is unknown but could be due to direct muscle or nerve trauma, anaesthetic toxicity, periocular haemorrhage or a combination of these.

Aged↗
PubMed2000

Stabilisation of diabetic retinopathy following simultaneous pancreas and kidney transplant.

BACKGROUND/AIMS: Simultaneous pancreas and kidney transplantation (SPK) has become an important option in selected IDDM patients with end stage renal disease (ESRD). Successful SPK transplants are associated with long term normoglycaemic control and improved quality of life. However, debate still continues on the benefit to patients in terms of stabilisation or amelioration of diabetic retinopathy. The progression of diabetic retinopathy (DR) in a cohort of 20 SPK transplant patients is reported. METHODS: All patients were reviewed postoperatively with corrected visual acuity, slit lamp examination, and fundal biomicroscopy. Preoperative data were collected retrospectively and DR was considered unstable if there had been a drop in Snellen acuity greater than three lines or a need for laser photocoagulation or vitrectomy in the 2 years preoperatively. RESULTS: 20 patients who received SPK transplants between March 1983 and April 1994 were reviewed (mean age 35.1 years; mean duration of IDDM = 24.6 years). 17 patients still had functioning grafts at a mean follow up of 5.1 years. Nine of these patients had unstable DR before transplantation. Of these, 89% (8/9) had stabilised DR following transplantation with only a single case requiring laser photocoagulation. Of the eight patients that had stable DR before transplantation all had stable DR following transplantation. 41% of cases (7/17) required cataract surgery during the follow up period. CONCLUSIONS: Advanced diabetic retinopathy is present in a high proportion of cases managed with SPK transplant as a consequence of the duration of IDDM and the presence of ESRD. More than 90% of cases have stable DR following transplant.

Adult↗
PubMed1998

Visual function and patient satisfaction after macular hole surgery.

PURPOSE: Over recent years success in macular hole surgery has increased in terms of anatomical closure. However, debate still continues on the benefit to the patient in terms of visual outcome. We designed a prospective study to investigate the outcome of full thickness macular hole (FTMH) surgery in terms of anatomical closure, visual outcome, incidence of complications and patient satisfaction. METHODS: Thirty eyes of 30 consecutive patients with FTMH were prospectively studied (stage 2 = 2; stage 3 = 23; stage 4 = 5). All cases had surgery involving vitrectomy, injection of an autologous platelet aggregate over the hole and gas tamponade. At 3 months post-operatively all cases were assessed for closure of the FTMH, Snellen acuity and the incidence of complications. At this stage all patients completed a patient satisfaction questionnaire. RESULTS: Anatomical closure of the hole was achieved in 83% of cases (25/30). Visual improvement of 2 Snellen lines or more occurred in 50% of cases (15/30). A vision of 6/12 or better was achieved in 27% of cases (8/30). A post-operative lens opacity was present in 46% (13/28) of phakic patients and a temporal, peripheral wedge-shaped field defect occurred in 17% (5/30) of cases. In this study, 53%, 70%, 57% and 67% of patients gave a positive response to specific questions about satisfaction with near, intermediate and distance vision and overall visual function respectively. CONCLUSIONS: Although the anatomical success of FTMH surgery is high the functional outcome in terms of Snellen acuity is less rewarding. Analysis of patient satisfaction suggests that the arbitrary visual outcome measures presently used may underestimate the functional benefit to the patient. Improved objective measures of visual outcome are required to assess the benefit of surgery in these cases.

Aged↗
PubMed1998

Three year visual outcome for treated stage 3 retinopathy of prematurity: cryotherapy versus laser.

BACKGROUND/AIMS: In the management of retinopathy of prematurity (ROP), several studies have demonstrated laser photocoagulation to be as effective as cryotherapy in reducing the incidence of unfavourable structural outcome. However, few data are available on the functional outcome. The 3 year visual acuity outcome of infants treated with laser or cryotherapy in a neonatal unit is presented. METHODS: The case notes of 34 infants (64 eyes) treated with cryotherapy, between 1989 and 1992, and 32 infants (59 eyes) treated with laser, between 1992 and 1995, were reviewed. RESULTS: In the cryotherapy group 69% of eyes had a favourable structural outcome. Of these structurally successful eyes 62.5%, 35.0%, and 33.3% of eyes had visual acuities within normal limits at the 12 month, 24 month, and 36 month corrected age milestones respectively. In the laser group 93% of eyes had a favourable structural outcome. Of these structurally successful eyes 96.4%, 66.7%, and 59.5% of eyes had visual acuities within normal limits at the 12 month, 24 month, and 36 month corrected age milestones respectively. CONCLUSION: In the management of ROP, when laser photocoagulation induces a structurally successful result, the potential for normal visual acuity development at 3 years is high. Whether the poorer functional outcome of the eyes treated with cryotherapy is an artefact of the historical nature of the study or as a result of an adverse effect of the destructive transcleral application is unknown.

Child Development↗
PubMed1997

Does cryotherapy before drainage increase the risk of intraocular haemorrhage and affect outcome? A prospective, randomised, controlled study using a needle drainage technique and sustained ocular compression.

AIMS/BACKGROUND: A prospective, randomised, controlled clinical trial was conducted to investigate the effect of performing cryotherapy before drainage of subretinal fluid (SRF) on the incidence of intraocular haemorrhage (IOH) in the management of retinal detachment. METHODS: Eighty eyes of 80 patients with rhegmatogenous retinal detachment requiring SRF drainage were recruited. Thirty four cases were randomised to receive drainage before cryotherapy (drainage, air injection, cryotherapy, and explant = DACE group) while 46 cases had drainage after cryotherapy (cryotherapy, drainage, air injection, and explant = CDAE group). All cases had trans-scleral drainage of SRF using a 27 gauge hypodermic needle combined with prolonged, intraocular hypertension. RESULTS: There was a low incidence of IOH associated with drainage in both groups with no statistically significant difference between the groups (DACE group = 2.9%; CDAE group = 4.3%; p = 0.43). There was no significant difference between the groups in the rate of anatomical success with a single operation (DACE group = 82.4%; CDAE group = 86.9%; p = 0.38). There was no significant difference between the groups in the visual outcome. An improvement of two Snellen lines or more occurred in 52.9% of the DACE group and in 56.5% of the CDAE group (p = 0.93). CONCLUSION: It was concluded that the surgical sequence of applying cryotherapy before drainage of SRF can be safely and effectively performed. The sequences CDAE and CDE, when air injection is not required, along with DACE should all be part of the surgical repertoire for the management of retinal detachments.

Adolescent↗
PubMed1988

N-methyl-D-aspartate raises cytosolic calcium concentration in rat cerebellar granule cells in culture.

The effects of glutamate receptor agonists on cytosolic calcium concentration in freshly isolated cerebellar granule cells and cells maintained in short term culture were determined using the fluorescent indicator fura-2. In freshly isolated cells depolarisation with high-K+ or addition of N-methyl-D-aspartate (NMDA) had no or only small effects on cytosolic calcium. After cells had been grown in monolayer culture for 20 h marked increases in cytosolic calcium concentration in response to 25 mm K+ or NMDA were detected. Other glutamate agonists had no (quisqualate) or small (kainate) effects on cytosolic calcium concentration. NMDA elevated cytosolic calcium concentration in the absence or presence of Mg2+ both before and after depolarisation by high K+. The results suggest that the effect of NMDA on granule cell differentiation and survival could be mediated by elevation of cytosolic calcium levels.

Animals↗
PubMed1987

Glutamate acting on NMDA receptors stimulates neurite outgrowth from cerebellar granule cells.

The effect of endogenous glutamate on neurite outgrowth from cerebellar granule cells in culture was examined. Neurite outgrowth was inhibited by enzymatic removal of endogenous glutamate from the culture medium. The broad-spectrum glutamate receptor antagonist kynurenate also inhibited neurite outgrowth from granule cells in serum-containing and serum-free cultures; the inhibition by kynurenate was reversed by exogenous glutamate. Neurite outgrowth was inhibited to the same extent by the NMDA receptor antagonist APV. These results indicate that endogenous glutamate, possibly released by granule cells themselves, stimulated neurite outgrowth through activation of the NMDA class of glutamate receptors. Activation of NMDA receptors on developing neurons may be an important mechanism for the regulation of neuronal growth and differentiation.

2-Amino-5-phosphonovalerate↗
PubMed1977

Streptococcal infections that fail to cause recurrences of rheumatic fever.

Prospective studies of recurrences of streptoccal infection and acute rheumatic fever were conducted among patients attending the acute rheumatic fever prophylaxis clinic (City of Memphis Hospitals, Memphis, Tennessee) between 1965 and 1972. The patient population consisted of 124 rheumatic children and adults, two-thirds of whom had evidence of rheumatic heart disease. A total of 104 immunologically documented streptococcal infections occurred during 235 patient-years of follow-up (44.3 infections per 100 patient-years) without a single recurrence of rheumatic fever. Immune responses tended to be modest, and 80% of the infections were subclinical. The majority of our group A streptococcal isolates were obtained from routine cultures of specimens from asymptomatic individuals. Many of these strains were "pyoderma" serotypes, whereas others exhibited a characteristic (production of opacity factor) recently reported to be associated with decreased immunogenicity. Several factors may have contributed to the low recurrence rate of acute rheumatic fever, including the age range of the population under study and immunologically significant infections with strains of Streptococcus that were not group A, but a major reason may be the possibility that the group A strains prevalent in this population have diminished rheumatogenic potential.

Adolescent↗