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1.  Keratocyte loss in corneal infection through apoptosis: a histologic study of 59 cases 
BMC Ophthalmology  2004;4:16.
Background
Keratocyte loss by apoptosis following epithelial debridement is a well-recognized entity. In a study of corneal buttons obtained from patients of corneal ulcer undergoing therapeutic keratoplasty, we observed loss of keratocytes in the normal appearing corneal stroma, surrounding the zone of inflammation. Based on these observations, we hypothesized that the cell loss in the inflammatory free zone of corneal stroma is by apoptosis that could possibly be a non-specific host response, independent of the nature of infectious agent.
Methods
To test our hypothesis, in this study, we performed Terminal deoxyribonucleotidyl transferase-mediated d-Uridine 5" triphosphate Nick End Labelling (TUNEL) staining on 59 corneal buttons from patients diagnosed as bacterial, fungal, viral and Acanthamoeba keratitis. The corneal sections were reviewed for morphologic changes in the epithelium, stroma, type, degree and depth of inflammation, loss of keratocytes in the surrounding stroma (posterior or peripheral). TUNEL positivity was evaluated in the corneal sections, both in the zone of inflammation as well as the surrounding stroma. A correlation was attempted between the keratocyte loss, histologic, microbiologic and clinical features.
Results
The corneal tissues were from 59 patients aged between 16 years and 85 years (mean 46 years) and included fungal (22), viral (15), bacterial (14) and Acanthamoeba (8) keratitis. The morphological changes in corneal tissues noted were: epithelial ulceration (52, 88.1%), destruction of Bowman's layer (58, 99%), mild to moderate (28; 47.5%) to severe inflammation (31; 52.5%). Morphologic evidence of disappearance or reduced number of keratocytic nuclei in the corneal stroma was noted in 49 (83%) cases; while the TUNEL positive brown cells were identified in all cases 53/54 (98%), including cases of fungal (19), bacterial (14), viral (13), and Acanthamoeba keratitis. TUNEL staining was located mostly in the deeper stroma and in few cases the peripheral stroma. TUNEL positivity was also noted with the polymorphonuclear infiltrates and in few epithelial cells (10 of 59, 17%) cases, more with viral infections (6/10; 60%).
Conclusions
We report apoptotic cell death of keratocytes in the corneal stroma in infectious keratitis, a phenomenon independent of type of infectious agent. The inflammatory cells in the zone of inflammation also show evidence of apoptotic cell death. It could be speculated that the infective process possibly triggers keratocyte loss of the surrounding stroma by apoptosis, which could possibly be a protective phenomenon. It also suggests that necrotic cell death and apoptotic cell deaths could occur simultaneously in infective conditions of the cornea.
doi:10.1186/1471-2415-4-16
PMCID: PMC545077  PMID: 15617577
infectious keratitis; apoptosis; keratocytes; TUNEL stain
2.  Comparative evaluation of diode laser versus argon laser photocoagulation in patients with central serous retinopathy: A pilot, randomized controlled trial [ISRCTN84128484] 
BMC Ophthalmology  2004;4:15.
Background
To evaluate the efficacy of diode laser photocoagulation in patients with central serous retinopathy (CSR) and to compare it with the effects of argon green laser.
Methods
Thirty patients with type 1 unilateral CSR were enrolled and evaluated on parameters like best corrected visual acuity (BCVA), direct and indirect ophthalmoscopy, amsler grid for recording scotoma and metamorphopsia, contrast sensitivity using Cambridge low contrast gratings and fluorescein angiography to determine the site of leakage.
Patients were randomly assigned into 2 groups according to the statistical random table using sequence generation. In Group 1 (n = 15), diode laser (810 nm) photocoagulation was performed at the site of leakage while in Group 2 (n = 15), eyes were treated with argon green laser (514 nm) using the same laser parameters. Patients were followed up at 4, 8 and 12 weeks after laser.
Results
The mean BCVA in group 1 improved from a pre-laser decimal value of 0.29 ± 0.14 to 0.84 ± 0.23 at 4 weeks and 1.06 ± 0.09 at 12 weeks following laser. In group 2, the same improved from 0.32 ± 0.16 to 0.67 ± 0.18 at 4 weeks and 0.98 ± 0.14 at 12 weeks following laser. The improvement in BCVA was significantly better in group 1 (p < 0.0001) at 4 weeks. At 4 weeks following laser, all the patients in group1 were free of scotoma while 6 patients in group 2 had residual scotoma (p < 0.05). The mean contrast sensitivity in group 1 improved from pre-laser value of 98.4 ± 24.77 to 231.33 ± 48.97 at 4 weeks and 306.00 ± 46.57 at 12 weeks following laser. In group 2, the same improved from 130.66 ± 31.95 to 190.66 ± 23.44 at 4 weeks and 215.33 ± 23.25 at 12 weeks. On comparative evaluation, a significantly better (p < 0.001) improvement was noted in group 1.
Conclusion
Diode laser may be a better alternative to argon green laser whenever laser treatment becomes indicated in patients with central serous retinopathy in terms of faster visual rehabilitation and better contrast sensitivity. In addition, diode laser also has the well-recognized ergonomic and economic advantages.
doi:10.1186/1471-2415-4-15
PMCID: PMC528729  PMID: 15516262
diode laser; central serous retinopathy; laser in CSR
3.  Erytrocyte membrane anionic charge in type 2 diabetic patients with retinopathy 
BMC Ophthalmology  2004;4:14.
Background
The Steno hypothesis states that changes in basement membrane anionic charge leads to diabetic microvascular complications. In diabetic nephropathy, loss of basement membrane glycosaminoglycans and the association between glomerular basement membrane heparan sulphate and proteinuria has been documented. A correlation between erythrocyte surface and the glomerular capillary wall charges has also been observed.
The aim of this study is to evaluate the relationship between retinopathy and erythrocyte anionic charge and urinary glycosaminoglycan excretion in type 2 diabetic patients.
Methods
49 subjects (58 ± 7 yrs, M/F 27/22) with type 2 diabetes with proliferative retinopathy (n = 13), nonproliferative retinopathy (n = 13) and without retinopathy (n = 23) were included in the study. 38 healthy subjects were selected as control group (57 ± 5 yrs, M/F 19/19). Erythrocyte anionic charge (EAC) was determined by the binding of the cationic dye, alcian blue. Urinary glycosaminoglycan and microalbumin excretion were measured.
Results
EAC was significantly decreased in diabetic patients with retinopathy (255 ± 30 ng alcian blue/106 RBC, 312 ± 30 ng alcian blue/106 RBC for diabetic and control groups respectively, p < 0.001). We did not observe an association between urinary GAG and microalbumin excretion and diabetic retinopathy. EAC is found to be negatively corralated with microalbuminuria in all groups.
Conclusions
We conclude that type 2 diabetic patients with low erythrocyte anionic charge are associated with diabetic retinopathy. Reduction of negative charge of basement membranes may indicate general changes in microvasculature rather than retinopathy. More prospective and large studies needs to clarify the role of glycosaminoglycans on progression of retinopathy in type 2 diabetic patients.
doi:10.1186/1471-2415-4-14
PMCID: PMC526283  PMID: 15473902
4.  Methods of assessment of patients for Nd:YAG laser capsulotomy that correlate with final visual improvement 
BMC Ophthalmology  2004;4:13.
Background
This paper attempts to clarify the usefulness of various simple pre-operative measures in estimating the potential for a visually successful capsulotomy.
Methods
24 patients attending for capsulotomy had pre-operative measures of glare with BAT tester, visibility of posterior pole and grading of posterior capsular pearls and fibrosis seen at slit lamp. Visual function was measured before and after standardised capsulotomy. Correlations of the various preoperative measures with eventual visual function improvements were calculated.
Results
Pearls at slit lamp and poor posterior pole visualisation were all correlated with improvements in visual acuity and contrast sensitivity after capsulotomy. Amount of fibrosis visible at slit lamp and glare assessment were not correlated with vision improvements after laser.
Conclusion
Of the various measures that are taken prior to Nd : YAG capsulotomy, some correlate with eventual visual improvement but for others no clinical utility was found. Practitioners should note these findings as they are especially of use in more questionable or high-risk cases to help determine whether referral for PCO treatment by Nd: YAG capsulotomy is likely to benefit the patient.
doi:10.1186/1471-2415-4-13
PMCID: PMC521490  PMID: 15387889
5.  Evaluation of the prophylactic use of mitomycin-C to inhibit haze formation after photorefractive keratectomy in high myopia: a prospective clinical study 
BMC Ophthalmology  2004;4:12.
Background
To study the effect of prophylactic application of mitomycin-C on haze formation in photorefractive keratectomy (PRK) for high myopia.
Methods
Fifty-four eyes of 28 myopic patients were enrolled in this prospective study. All eyes were operated by PRK followed by 0.02% mitomycin-C application for two minutes and washed with 20 ml normal saline afterwards. All eyes were examined thoroughly on the first 7 days and one month after surgery; 48 eyes (88.9%) at 3 and 6 months postoperatively. Hanna grading (in the scale of 0 to 4+) was used for assessment of corneal haze.
Results
The mean spherical equivalent refraction (SE) was -7.08 diopters (D) ± 1.11 (SD) preoperatively. Six months after surgery, 37 eyes (77.1%) achieved an uncorrected visual acuity (UCVA) of 20/20 or better, all eyes had a UCVA of 20/40 or better and 45 (93.7%) eyes had an SE within ± 1.00D. One month postoperatively, 2 eyes (3.7%) had grade 0.5+ of haze, while at 3 and 6 months after surgery no visited eye had haze at all. All eyes had a best corrected visual acuity (BCVA) of 20/40 or better and there were no lost lines in BCVA by 6 months after surgery. In spatial frequencies of 6 and 12 cycles per degree contrast sensitivity had decreased immediately after PRK and it had increased 1.5 lines by the 6th postoperative month compared to the preoperative data.
Conclusions
The results show the efficacy of mitomycin-C in preventing corneal haze after treatment of high myopia with PRK. This method- PRK + mitomycin-C – can be considered an alternative treatment for myopic patients whose corneal thicknesses are inadequate for laser in situ keratomileusis (LASIK). However, the results should be confirmed in longer follow-ups.
doi:10.1186/1471-2415-4-12
PMCID: PMC520812  PMID: 15363107
6.  Case-control study on uveal melanoma (RIFA): rational and design 
BMC Ophthalmology  2004;4:11.
Background
Although a rare disease, uveal melanoma is the most common primary intraocular malignancy in adults, with an incidence rate of up to 1.0 per 100,000 persons per year in Europe. Only a few consistent risk factors have been identified for this disease. We present the study design of an ongoing incident case-control study on uveal melanoma (acronym: RIFA study) that focuses on radiofrequency radiation as transmitted by radio sets and wireless telephones, occupational risk factors, phenotypical characteristics, and UV radiation.
Methods/Design
We conduct a case-control study to identify the role of different exposures in the development of uveal melanoma. The cases of uveal melanoma were identified at the Division of Ophthalmology, University of Essen, a referral centre for tumours of the eye. We recruit three control groups: population controls, controls sampled from those ophthalmologists who referred cases to the Division of Ophthalmology, University of Duisburg-Essen, and sibling controls. For each case the controls are matched on sex and age (five year groups), except for sibling controls. The data are collected from the study participants by short self-administered questionnaire and by telephone interview. During and at the end of the field phase, the data are quality-checked.
To estimate the effect of exposures on uveal melanoma risk, we will use conditional logistic regression that accounts for the matching factors and allows to control for potential confounding.
doi:10.1186/1471-2415-4-11
PMCID: PMC515306  PMID: 15318944
7.  Corneal topographic changes following retinal surgery 
BMC Ophthalmology  2004;4:10.
Background
To study the effect of retinal/ vitreoretinal surgeries on corneal elevations.
Methods
Patients who underwent retinal/ vitreoretinal surgeries were divided into 3 groups. Scleral buckling was performed in 11 eyes (Group 1). In 8 (25%) eyes, vitreoretinal surgery was performed along with scleral buckling (Group 2). In 12 eyes, pars plana vitrectomy was performed for vitreous hemorrhage (Group 3). An encircling element was used in all the eyes. The parameters evaluated were best-corrected visual acuity (BCVA), change in axial length, and corneal topographic changes on Orbscan topography system II, preoperative and at 12 weeks following surgery.
Results
There was a statistically significant increase in anterior corneal elevation in all the three groups after surgery (p = 0.003, p = 0.008 & p = 0.003 respectively). The increase in posterior corneal elevation was highly significant in all the three groups after surgery (p = 0.0000, p = 0.0001 & p = 0.0001 respectively). The increase in the posterior corneal elevation was more than the increase in the anterior elevation and was significant statistically in all the three groups (group I: p = 0.02; group II: p = 0.01; group III: p = 0.008).
Conclusions
Retinal/ vitreoretinal surgeries cause a significant increase in the corneal elevations and have a greater effect on the posterior corneal surface.
doi:10.1186/1471-2415-4-10
PMCID: PMC509420  PMID: 15291963
anterior corneal elevation; posterior corneal elevation; scleral buckling; retinal surgery
8.  Retinopathy and microalbuminuria in type II diabetic patients 
BMC Ophthalmology  2004;4:9.
Background
The aim of this study was to identify risk factors for the development of retinopathy and microalbuminuria and their correlation in type II diabetic patients.
Methods
In this cross-sectional study 590 patients suffering from diabetis type II were examined. Fundoscopy was performed by practising ophthalmologist. The ratio of urinary albumin to creatinine was assessed by clinitek 100 (Bayer corporation–USA). HbA1C, height and weight also were measured.
Results
The overall prevalence of retinopathy was 39.3% (232 patients), 5.4% of which showed to be prolifrative diabetic retinopathy (PDR). The diabetic retinopathy had significant inverse correlation with body mass index (BMI) (P = 0.02). HbA1C was higher in patients with PDR (mean = 10.5%) than in patients with no signs of retinopathy (mean = 9.5%) and this difference was statistically significant (P = 0.001). The prevalence of microalbuminuria was 25.9% while 14.5% of the patients revealed to have macroalbuminuria. As expected, diabetic retinopathy and renal involvement were highly positively correlated. (P = 0.001).
Conclusion
Microalbuminuria is associated with diabetic retinopathy in type II diabetic patients and is a reliable marker of retinopathy.
doi:10.1186/1471-2415-4-9
PMCID: PMC459228  PMID: 15228626
9.  Does a small central Nd:YAG posterior capsulotomy improve peripheral fundal visualisation for the Vitreoretinal surgeon? 
BMC Ophthalmology  2004;4:8.
Background
To evaluate the effect of Nd:YAG capsulotomy for posterior capsular opacification (PCO) on visualisation of the peripheral fundus with scleral indentation.
Methods
Patients undergoing Nd:YAG capsulotomy for PCO were examined pre- and four weeks post- Nd:YAG capsulotomy. In order to give a quantitative measure of visualisation of the peripheral retina, a novel scalar measurement was developed. Changes in the degree of visualisation following Nd:YAG capsulotomy were calculated.
Results
There was a significant improvement in fundal visualisation of the retinal periphery with scleral indentation following Nd:YAG capsulotomy (p = 0.001).
Conclusion
Peripheral fundal visualisation with scleral indentation improves following a small central Nd:YAG capsulotomy. This finding is important in relation to the detection of peripheral pseudophakic retinal breaks, particularly in those patients deemed at high risk following Nd:YAG capsulotomy.
doi:10.1186/1471-2415-4-8
PMCID: PMC449714  PMID: 15228627
10.  Triple-A syndrome with prominent ophthalmic features and a novel mutation in the AAAS gene: a case report 
BMC Ophthalmology  2004;4:7.
Background
Triple-A syndrome (Allgrove syndrome) is an autosomal recessive disorder characterized by adrenal insufficiency, alacrima, achalasia, and – occasionally – autonomic instability. Mutations have been found in the AAAS gene on 12q13.
Case presentation
We present the case of a 12 year-old boy with classic systemic features of triple-A syndrome and several prominent ophthalmic features, including: accommodative spasm, dry eye, superficial punctate keratopathy, and pupillary hypersensitivity to dilute pilocarpine. MRI showed small lacrimal glands bilaterally. DNA sequencing of PCR-amplified fragments from the 16 exons of the AAAS gene revealed compound heterozygosity for a new, out-of-frame 5-bp deletion in exon 15, c1368-1372delGCTCA, and a previously-described nonsense mutation in exon 9, c938C>T, R286X.
Conclusions
In addition to known ophthalmic manifestations, triple-A syndrome can present with accommodative dysregulation and ocular signs of autonomic dysfunction.
doi:10.1186/1471-2415-4-7
PMCID: PMC459227  PMID: 15217518
11.  Pupillary anomaly masquerading as a glaucomatous visual field defect: a case report 
BMC Ophthalmology  2004;4:6.
Background
Patients are often referred to ophthalmologists with focal visual field defects on routine testing, possibly related to a potential diagnosis of glaucoma. However, examination of the individual patient's ocular characteristics as well as facial characteristics may often reveal a cause of the visual field defect.
Case presentation
We describe a patient who was found to have a superior visual field defect on routine testing by the optician. Repeat perimetry with pharmacological dilatation of the pupil revealed that the cause of the field defect was related to an eccentric inferiorly displaced pupil, secondary to trauma some years previously.
Discussion
Individual patient characteristics, including both ocular, as well as facial, need to be considered, when interpreting any visual field defect.
doi:10.1186/1471-2415-4-6
PMCID: PMC436060  PMID: 15198808
12.  Autoantibodies against retinal proteins in paraneoplastic and autoimmune retinopathy 
BMC Ophthalmology  2004;4:5.
Background
Autoimmune retinal degeneration may occur in patients who present with sudden or, less commonly, subacute loss of vision of retinal origin, associated with an abnormal ERG, through the action of autoantibodies against retinal proteins. Often the patients are initially diagnosed with or suspected of having a paraneoplastic retinopathy (PR), such as cancer-associated retinopathy (CAR). However, there is limited information on the occurrence, the specificity of autoantibodies in these patients, and their association with clinical symptoms.
Methods
Sera were obtained from 193 retinopathy patients who presented with clinical symptoms resembling PR or autoimmune retinopathy (AR), including sudden painless loss of vision, typically associated with visual field defects and photopsias, and abnormal rod and/or cone responses on the electroretinogram (ERG). Sera were tested for the presence of anti-retinal autoantibodies by Western blot analysis using proteins extracted from human retina and by immunohistochemistry. Autoantibody titers against recoverin and enolase were measured by ELISA.
Results
We identified a higher prevalence of anti-retinal autoantibodies in retinopathy patients. Ninety-one patients' sera (47.1%) showed autoantibodies of various specificities with a higher incidence of antibodies present in retinopathy patients diagnosed with cancer (33/52; 63.5%; p = 0.009) than in retinopathy patients without cancer (58/141; 41.1%). The average age of PR patients was 62.0 years, and that of AR patients was 55.9 years. Autoantibodies against recoverin (p23) were only present in the sera of PR patients, autoantibodies against unknown p35 were more common in patients with AR, while anti-enolase (anti-p46) autoantibodies were nearly equally distributed in the sera of patients with PR and those with AR. In the seropositive patients, the autoantibodies persisted over a long period of time – from months to years. A rebound in anti-recoverin autoantibody titer was found to be associated with exacerbations in visual symptoms but not in the recurrence of cancer. When compared to sera from healthy subjects, autoantibodies against retinal proteins from both groups of patients were cytotoxic to retinal cells, indicating their pathogenic potential.
Conclusions
These studies showed that patients with sudden or subacute, unexplained loss of vision of retinal origin have anti-retinal antibodies in a broad range of specificity and indicate the need for autoantibody screening. Follow-up tests of antibody levels may be useful as a biomarker of disease activity associated with worsening of vision. Moreover, the heterogeneity in autoantibody specificity may explain the variation and complexity of clinical symptoms in retinopathy patients.
doi:10.1186/1471-2415-4-5
PMCID: PMC446200  PMID: 15180904
13.  Lymph node removal enhances corneal graft survival in mice at high risk of rejection 
BMC Ophthalmology  2004;4:3.
Background
As shown previously, the submandibular (SM) lymph node (LN) is required for priming the immune response during corneal graft rejection. In this study, we wished to determine whether corneal grafts at "high-risk" of rejection were also protected after selective SM LN removal and if so to investigate whether this improved corneal graft survival was due to induction of specific regulatory/suppressor cells or was due to immunological "ignorance".
Methods
Two sets of experiments were performed. (1) Adoptive transfer of possible regulatory splenocytes from mice with long-term accepted corneal graft after SM LN removal. (2) SM LN removal and corneal grafts in "high-risk" hosts, which had been (A) subjected to corneal trauma with vascularization or (B) allosensitized by previous corneal graft or (C) allosensitized by previous skin graft.
Results
Adoptive transfer of splenocytes from tolerant mice after SM LN removal did not enhance corneal graft survival in naive recipients (p > 0.05).
SM LN removal in mice with corneal vascularization enhanced corneal allograft survival compared to grafted controls with/without vascularization (p < 0.0001). The removal of the SM LN in mice, who had already been allosensitized by a previous corneal graft, did not statistically prolong corneal graft survival (p > 0.05). SM LN removal procedure did not delay rejection of corneal grafts in mice allosensitized by a previous skin transplant with the same strain combination (p > 0.05).
Conclusion
The results suggest that removal of the SM LN in "high-risk" mice prevents rejection by mechanisms involving immune "ignorance", since prior allosensitization prevents graft acceptance after LN removal. In allosensitized recipients the stronger the allosensitization (skin- vs. corneal graft-presensitization) the greater the possibility of priming for rejection at alternative draining LN sites.
doi:10.1186/1471-2415-4-3
PMCID: PMC406505  PMID: 15038832
14.  Intraocular pressure and ocular pulse amplitude using dynamic contour tonometry and contact lens tonometry 
BMC Ophthalmology  2004;4:4.
Background
The new Ocular Dynamic Contour Tonometer (DCT), investigational device supplied by SMT (Swiss Microtechnology AG, Switzerland) allows simultaneous recording of intraocular pressure (IOP) and ocular pulse amplitude (OPA). It was the aim of this study to compare the IOP results of this new device with Goldmann tonometry. Furthermore, IOP and OPA measured with the new slitlamp-mounted DCT were compared to the IOP and OPA measured with the hand-held SmartLens®, a gonioscopic contact lens tonometer (ODC Ophthalmic Development Company AG, Switzerland).
Methods
Nineteen healthy subjects were included in this study. IOP was determined by three consecutive measurements with each of the DCT, SmartLens®, and Goldmann tonometer. Furthermore, OPA was measured three times consecutively by DCT and SmartLens®.
Results
No difference (P = 0.09) was found between the IOP values by means of DCT (mean: 16.6 mm Hg, median: 15.33 mm Hg, SD: +/- 4.04 mm Hg) and Goldmann tonometry (mean: 16.17 mm Hg, median: 15.33 mm Hg, SD: +/- 4.03 mm Hg). The IOP values of SmartLens® (mean: 20.25 mm Hg, median: 19.00 mm Hg, SD: +/- 4.96 mm Hg) were significantly higher (P = 0.0008) both from Goldmann tonometry and DCT. The OPA values of the DCT (mean: 3.08 mm Hg, SD: +/- 0.92 mm Hg) were significantly lower (P = 0.0003) than those obtained by SmartLens® (mean: 3.92 mm Hg, SD: +/- 0.83 mm Hg).
Conclusions
DCT was equivalent to Goldmann applanation tonometry in measurement of IOP in a small group of normal subjects. In contrast, SmartLens® (contact lens tonometry) gave IOP readings that were significantly higher compared with Goldmann applanation tonometer readings. Both devices, DCT and SmartLens® provide the measurement of OPA which could be helpful e.g. for the management of glaucoma.
doi:10.1186/1471-2415-4-4
PMCID: PMC394329  PMID: 15038831
Dynamic contour tonometry; Goldmann applanation tonometry; contact lens tonometry; ocular pulse amplitude; glaucoma
15.  High grade lymphoma in the nasopharynx presented as sudden onset of bilateral blindness 
BMC Ophthalmology  2004;4:2.
Background
Sudden onset of bilateral blindness is rare; hysteria, cortical infarction or bilateral central retinal arterial occlusion can cause this.
Case presentation
The authors describe a single case of sudden onset bilateral blindness in a patient with nasopharyngeal carcinoma, which is unusual. Biopsy revealed a high-grade lymphoma. After treatment the patient made a complete visual recovery, with no evidence of visual sequelae and no clear reasons for this complete recovery.
Conclusion
CT and MR imaging did not demonstrate any lesions invading any part of the visual pathway or even indeed the occipital cortex. High dose steroids may have reduced the mass effect of the tumour or the blindness may have been hysterical but is unlikely.
doi:10.1186/1471-2415-4-2
PMCID: PMC387828  PMID: 15102322
lymphoma; nasopharynx; blindness
16.  Variability of wavefront aberration measurements in small pupil sizes using a clinical Shack-Hartmann aberrometer 
BMC Ophthalmology  2004;4:1.
Background
Recently, instruments for the measurement of wavefront aberration in the living human eye have been widely available for clinical applications. Despite the extensive background experience on wavefront sensing for research purposes, the information derived from such instrumentation in a clinical setting should not be considered a priori precise. We report on the variability of such an instrument at two different pupil sizes.
Methods
A clinical aberrometer (COAS Wavefront Scienses, Ltd) based on the Shack-Hartmann principle was employed in this study. Fifty consecutive measurements were perfomed on each right eye of four subjects. We compared the variance of individual Zernike expansion coefficients as determined by the aberrometer with the variance of coefficients calculated using a mathematical method for scaling the expansion coefficients to reconstruct wavefront aberration for a reduced-size pupil.
Results
Wavefront aberration exhibits a marked variance of the order of 0.45 microns near the edge of the pupil whereas the central part appears to be measured more consistently. Dispersion of Zernike expansion coefficients was lower when calculated by the scaling method for a pupil diameter of 3 mm as compared to the one introduced when only the central 3 mm of the Shack – Hartmann image was evaluated. Signal-to-noise ratio was lower for higher order aberrations than for low order coefficients corresponding to the sphero-cylindrical error. For each subject a number of Zernike expansion coefficients was below noise level and should not be considered trustworthy.
Conclusion
Wavefront aberration data used in clinical care should not be extracted from a single measurement, which represents only a static snapshot of a dynamically changing aberration pattern. This observation must be taken into account in order to prevent ambiguous conclusions in clinical practice and especially in refractive surgery.
doi:10.1186/1471-2415-4-1
PMCID: PMC362876  PMID: 15018630

Results 1-16 (16)