Validation of two scoring systems for the prediction of posterior capsule rupture during phacoemulsification surgery.

AIM: To attempt to validate two scoring systems for the prediction of intraoperative complication during phacoemulsification surgery. METHODS: The study population was patients attending Sunderland Eye Infirmary who underwent phacoemulsification surgery between 1 January 2001 and 31 December 2003. The authors applied each scoring system to a control group of 300 patients from this study population and extrapolated the results to give an estimate of the spread of scores for the entire population. They then applied the same scoring systems to all complicated cases from the same study population. Using these results they were able to calculate the risk of a complication for a particular score on each scoring system. CONCLUSION: The application of these systems in clinical practice would allow appropriate selection of phacoemulsification cases for trainee surgeons, more accurate consent from patients for their phacoemulsification surgery, and the unbiased comparison of surgical outcomes from surgeons with differing case mix difficulties.

The role of case mix in the relation of volume and outcome in phacoemulsification.

BACKGROUND/AIM: The authors previously demonstrated a decrease in complication rate with an increase in volume of cases performed by a surgeon. All studies of volume and outcome are potentially hampered by the issue of case mix, in that some lower volume surgeons may in fact do fewer cases because they have more complex patients. This study was designed to assess the influence of case mix on the volume-outcome relation in phacoemulsification surgery that had previously been demonstrated. METHODS: This study took place wholly in Sunderland Eye Infirmary. 667 cases from between 1996 and 2001 were randomly selected from the operative lists of the six surgeons involved in a previous study. The case complexity was assessed using a potential difficulty score (PDS) devised from preoperative data predictive of potential surgical difficulty. The PDS was validated by a retrospective analysis of a sample of 100 cases. RESULTS: 528 complete sets of notes were retrieved. The overall PDS scores ranged from 1 to 6. There was a difference between the proportions of patients with each PDS value (p=0.015) in the two groups, which suggested that the low volume surgeons were doing potentially more difficult cases. The median PDS for each volume group were the same (=1.0). Retrospective validation analysis of the PDS score revealed higher mean and median values in complicated cases compared to uncomplicated cases. CONCLUSION: This follow up study re-emphasises the importance of case mix adjustment in comparative assessment of healthcare quality. These results may explain in part the trend previously demonstrated of lower complication rates for higher volume surgeons.

The relation of volume with outcome in phacoemulsification surgery.

BACKGROUND/AIMS: High case volume has been associated with better health outcomes for a variety of procedures and conditions including coronary angioplasty, carotid endarterectomy, colorectal surgery, and various types of cancer surgery. The association of volume and outcome has important implications for patient safety and healthcare delivery planning. The relation between surgical volume and outcome has not, as far as is known, been looked at for phacoemulsification alone. METHODS: All cataract surgery performed from 1996 to 2001 by six consultant surgeons was reviewed. Using theatre logbooks and cross checking with the hospital database, the total number of phacoemulsification procedures performed per surgeon per year was calculated. The total number of operations in which it was judged that significant intraoperative complications occurred was also counted. RESULTS: When the data were pooled for all the surgeons there was evidence that complication rate decreased over time (Spearman's rho = -0.319, p = 0.058). If the data were pooled from all the years and all the surgeons then there was strong evidence of a decrease in complication rate with an increase in the number of cases (Spearman's rho = -0.63, p<0.01). CONCLUSIONS: This study is the first to describe a possible relation between volume of surgery and the outcome (as measured by complication rates) for phacoemulsification. There are however some caveats in that the issue of case mix was not addressed and that the results are from a single unit and may not necessarily be generalisable

Ischaemic heart disease may predispose to pseudophakic cystoid macular oedema.

PURPOSE: Pseudophakic macular oedema (PMO) is uncommon following uncomplicated phacoemulsification and lens implantation and the cause of infrequent cases is rarely understood. This study was undertaken to determine whether a relationship exists between ischaemic heart disease (IHD) and PMO. METHODS: Retrospective case note review was carried out of 177 (252 eyes) consecutive patients without pre-existing retinal disease who underwent phacoemulsification and intraocular lens implantation during a 12 month period. Patients with a post-operative best corrected visual acuity < 6/9 underwent slit-lamp biomicroscopy and fluorescein angiography to identify PMO. IHD was defined on clinical and electrocardiographic grounds. The incidence of IHD was compared in patients with and without PMO and statistical analysis performed using the Fisher's exact test. RESULTS: PMO occurred in 4 patients (6 eyes), all of whom had IHD, whereas no PMO occurred in the remaining 173 patients (246 eyes) (p = 0.04). CONCLUSIONS: Pseudophakic macular oedema represents an important complication following modern phacoemulsification and intraocular lens implantation and is associated significantly with ischaemic heart disease.

Clinical factors influencing the visual prognosis of the fellow eyes of normal tension glaucoma patients with unilateral field loss.

AIM: To investigate the influence of several clinical variables on the development of visual field loss in the "second eye" of patients with normal tension glaucoma (NTG) presenting with unilateral field loss. METHODS: Patients with NTG and unilateral field loss at presentation were selected from a cohort of 403 consecutive diagnoses of NTG. The state of the visual field "normal" or with a visual field defect was defined using the Advanced Glaucoma Intervention Study (AGIS) template. Where available, optic disc planimetry was carried out on stereo photographs taken at presentation. Measurements of the topography of each of these optic discs were compared with morphometric values from a group of normal subjects, allowing for differences in age and disc size. For each patient the percentage of the relative neuroretinal rim (NRR) area was calculated. The time taken to develop a visual field defect was related to clinical factors including age, sex, peak and mean diurnal intraocular pressure (IOP), refraction, relative NRR area, and the AGIS score of the fellow eye at presentation RESULTS: 54 patients were included in the study. The median (range) follow up time was 49.2 (11.1-116.7) months. 14 (26%) patients developed field loss in the eyes with an initially normal field. The estimate of the median time to field loss onset was 95.1 months. Field damage developed more rapidly in women and in patients with greater AGIS score in the contralateral eye at the beginning of follow up ((adjusted hazard ratio, HR (95% confidence interval, CI) 0.20 (0. 04; 0.93); 1.19 (1.02; 1.41) respectively)). Little evidence of any association was found between time to onset of field loss and each of age, refraction, and peak or mean diurnal IOP. Planimetric disc analysis was carried out in 33 (61%) patients. Of these 10 (30%) developed field loss in the eyes with initial normal field at a median follow up of 95.1 months. After adjustment for sex and AGIS, relative NRR area was found to be significantly related to the time of onset of field damage, the greater the reduction in relative NRR area, the shorter the time to visual field loss (HR 0.93 (0.89; 0. 99)). CONCLUSIONS: NTG patients with unilateral field loss are at high risk of developing field damage in the eyes with an initially normal visual field. In this study, the visual prognosis of the eye with the normal visual field at presentation was found to be influenced by the extent of the reduction in relative NRR area together with the severity of field damage in the contralateral eye at presentation.

The relationships of age changes in retinal pigment epithelium and Bruch's membrane.

PURPOSE: To study the correlations between age, Bruch's membrane (BM) thickness, retinal pigment epithelial (RPE) autofluorescence, and RPE residual body content. METHODS: Eight-millimeter-diameter macular discs from 88 unpaired human eye bank eyes were obtained within 72 hours of death, fixed in 10% neutral buffered formalin, and hemisected horizontally. One portion of the macular disc was embedded in paraffin and stained with periodic acid-Schiff for the measurement of BM thickness. RPE autofluorescence measurements were performed on unstained, deparaffinized sections. A second portion of the macular disc was prepared for electron microscopy to evaluate RPE residual body content. Linear and polynomial regression techniques were used to investigate the correlations between age, BM thickness, RPE autofluorescence, and RPE residual body content. RESULTS: Bruch's membrane thickness increased with age according to the linear model. RPE autofluorescence and RPE residual body content also increased with age, but the correlations were best approximated by a quadratic model. The correlations between RPE autofluorescence and residual body content and between BM thickness and RPE autofluorescence were best approximated by a linear regression model. There was considerable variation in these correlations between specimens and within the same age group. CONCLUSIONS: Although the changes in RPE and Bruch's membrane increased with age and there was a direct correlation between changes in the two tissues, there was considerable variation within each age group and between specimens. This probably reflects the multifactorial nature of the process.

Frequency of asymmetric visual field defects in normal-tension and high-tension glaucoma.

OBJECTIVE: The purpose of the study was to evaluate the frequency of asymmetric visual field loss at presentation in patients with normal-tension glaucoma (NTG) and high-tension glaucoma (HTG). DESIGN: A retrospective cross-sectional study design was used. PARTICIPANTS: Four hundred and three NTG patients and 337 consecutive HTG patients (consecutive diagnoses between 1986 and 1996). INTERVENTION: Analysis of the frequency of unilateral field loss presentations in NTG and HTG. The visual fields of fellow eyes were compared to determine the side of more severe field loss. For the NTG patients, the relationship between the side with greater field loss and corresponding intraocular pressure (IOP) was investigated. MAIN OUTCOME MEASURES: Humphrey field analyzer mean defect (MD) and mean diurnal IOP. RESULTS: In the NTG group, 101 (25%) patients presented with unilateral field loss. The proportion of cases with unilateral field loss decreased with increasing age of presentation (chi-square test for trend = 26.9; P < 0.0001). Sixty-four percent of the patients had unilateral field loss in the left eye. Sixty-eight percent of the cases with bilateral field loss had a higher MD in the left eye. The diurnal IOP was estimated as 0.23 +/- 0.068 mmHg (mean +/- SE) higher in the left eye (P = 0.001). In the HTG group, 104 (31%) patients presented with unilateral field loss. The proportion of cases with unilateral field loss decreased with increasing age of presentation (chi-square test for trend = 4.6; P = 0.03). Right and left eyes had an equal chance of having field loss in unilateral cases and of being the side of more advanced field damage in bilateral cases. CONCLUSIONS: The frequency of cases with unilateral field loss was similar in HTG and NTG patients. Patients with unilateral field loss at presentation were more likely to be at the younger end of the age range. In the NTG population we studied, the left eye was more frequently the side of onset of field loss and 2.1 times more likely to present with a greater field defect than the right eye. In HTG patients, right and left eyes showed an equal chance of being the side of onset of field damage and the more affected side.

Pulsatile ocular blood flow investigation in asymmetric normal tension glaucoma and normal subjects.

AIMS: This study was designed to investigate pulsatile ocular blood flow (POBF) in normal tension glaucoma (NTG) patients and in normal controls. NTG patients with unilateral field loss were evaluated to compare POBF values between eyes with and without field loss. METHODS: POBF measurements from more than 1500 subjects were collected during a period of 6 months from six optometric centres. Subjects with systemic vascular diseases (such as systemic hypertension and diabetes), ophthalmic diseases, a positive family history of glaucoma, and those individuals receiving treatment with systemic beta blockers were excluded on the basis of a questionnaire. For comparison, 95 NTG patients with unilateral field loss, selected from 403 consecutive patients with NTG, underwent POBF testing. For each individual age, sex, intraocular pressure, refraction, and pulse rate were entered into a database. RESULTS: Data from 777 subjects were included in the analysis. POBF measurements of patients and subjects were compared allowing for differences in age, sex, intraocular pressure, refraction, and pulse rate. POBF was significantly lower in eyes of NTG patients with and without field loss (p < 0.001 and p = 0.01 respectively). Eyes of NTG patients with field loss showed significantly lower POBF than the contralateral eyes with normal field (p < 0.001). CONCLUSIONS: POBF was significantly lower in eyes of NTG patients with and without field loss than in normal subjects, suggesting that differences in ocular blood perfusion are relevant to the development of NTG and are detectable from the early stage of the disease. Furthermore, the finding of lower POBF in NTG eyes with field loss than in the contralateral eyes with normal field suggests that haemodynamic differences between fellow eyes contribute to determine the side of onset of the disease.