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Biomedical subjects

Sunil Shah

Publications and source records attributed to Sunil Shah.

At least 19 recordsLinked to original sources
PubMed2006

The use of the Reichert ocular response analyser to establish the relationship between ocular hysteresis, corneal resistance factor and central corneal thickness in normal eyes.

PURPOSE: The aim of this study was to measure ocular hysteresis and corneal resistance factor (CRF), novel methods of analysing ocular rigidity/elasticity and to determine the relationship between central corneal thickness (CCT), hysteresis and CRF in normal subjects. DESIGN: Prospective, cross-sectional, clinical trial. PARTICIPANTS: The study included 207 normal eyes. METHODS: Hysteresis and CRF were measured by the ocular response analyser. The CCT was measured using a hand held ultrasonic pachymeter. MAIN OUTCOME MEASURES: Ocular hysteresis and CRF in normal patients and their relationship with CCT. RESULTS: The mean hysteresis was 10.7+/-2.0 mmHg standard deviation (S.D.) (range 6.1-17.6 mmHg); the mean CRF was 10.3+/-2.0 (range 5.7-17.1 mmHg). The mean CCT was 545.0+/-36.4 microm (471-650 microm). The relationship between hysteresis and CCT; CRF and CCT; CRF and hysteresis were significant (p<0.0001). CONCLUSION: This study demonstrated that corneal hysteresis increased with increasing CCT, however, the correlation was moderate. It would appear that CCT, hysteresis and CRF may measure different biomechanical aspects of ocular rigidity and are likely to be useful additional measurement to CCT in the assessment of ocular rigidity when measuring intraocular pressure (IOP). This may be of particular importance when trying to correct IOP measurements for increased or decreased ocular rigidity.

Adolescent↗
PubMed2006

The AS biometry technique--a novel technique to aid accurate intraocular lens power calculation after corneal laser refractive surgery.

Intraocular lens power (IOL) calculation for cataract surgery has been shown to be inaccurate after photorefractive keratectomy (PRK), laser-assisted subepithelial keratectomy (LASEK) and laser in situ keratomileusis (LASIK). Many techniques exist to calculate corneal power with varying results and require the clinician to be aware of the pitfalls of IOL power calculation in post-refractive eyes. The AS biometry method proposed here is a simple method which does not rely on the calculation of corneal power. This new method is compared to the current gold standard the clinical history method (CHM). Twenty-nine eyes of 15 patients had routine biometry prior to LASIK, LASEK or PRK. The range of pre-operative spherical equivalent refractive error was -5.37 to +4.00 diopters. The post-operative refraction was measured at 3-6 months. The IOL power calculation was calculated using the AS biometry method and the CHM. The two methods were compared using the Student's paired t-test and the Bland Altman technique. There was no statistical difference between the AS biometry method and the CHM. The paired Student's t-test comparing the AS biometry method and the CHM showed no statistical difference, t=0.33 with a p-value of 0.75, at a 95% confidence interval. The authors conclude that the AS biometry technique is as accurate as the CHM. The former is a simpler method which avoids many of the pitfalls and confounding factors involved in IOL power calculation following corneal excimer laser surgery. However, like the CHM it requires measurements prior to laser surgery.

Adult↗
PubMed2006

Diurnal variation of ocular hysteresis in normal subjects: relevance in clinical context.

BACKGROUND: This study was conducted to assess the diurnal variation in ocular hysteresis, as measured by the Ocular Response Analyser to establish a relationship between diurnal hysteresis variation and diurnal intraocular pressure (IOP) variation. METHODS: Forty-two normal eyes of 21 colleagues and staff in a teaching hospital in Birmingham, UK, were recruited. The IOP and hysteresis were measured by the Ocular Response Analyser. The central corneal thickness (CCT) was measured using a hand-held ultrasonic pachymeter in the mid-pupillary axis. RESULTS: The mean ocular hysteresis at 8 am was 12.7 +/- 2.3 mmHg, at 11 am was 12.2 +/- 2.0 mmHg, at 2 PM was 12.7 +/- 2.1 mmHg and at 5 PM was 12.7 +/- 1.7 mmHg; the difference between the values at any time of measurement was not statistically significant (P > 0.9, repeated measures). IOP as measured by non-contact tonometry was 18.4 +/- 2.8 mmHg, 17.9 +/- 3.3 mmHg, 16.9 +/- 3.1 mmHg and 16.8 +/- 3.2 mmHg, respectively, for the same time period; the difference between the values in the morning and afternoon was statistically significant (P < 0.0001, repeated measures). The CCT was 548.8 +/- 29.5 microm, 547.0 +/- 31.4 microm, 548.2 +/- 29.6 microm and 548.6 +/- 29.4 microm, respectively; the difference between the values was not statistically significant at any time points. Multiple regression analysis showed the relationship between IOP and hysteresis was not statistically significant (P = 0.9). CONCLUSION: The ocular hysteresis reading was almost constant throughout the day, whereas the IOP readings showed highest values in the morning with a reducing trend being lowest in the afternoon. The CCT values were almost stable throughout the day. IOP appears to vary independently of a variation in hysteresis or CCT.

Adult↗
PubMed2006

Objective accommodative amplitude and dynamics with the 1CU accommodative intraocular lens.

PURPOSE: To compare the objective accommodative amplitude and dynamics of eyes implanted with the one-compartment-unit (1CU; HumanOptics AG, Erlangen, Germany) accommodative intraocular lenses (IOLs) with that measured subjectively. METHODS: Twenty eyes with a 1CU accommodative IOL implanted were refracted and distance and near acuity measured with a logMAR (logarithm of the minimum angle of resolution) chart. The objective accommodative stimulus-response curve for static targets between 0.17 and 4.00 D accommodative demand was measured with the SRW-5000 (Shin-Nippon Commerce Inc., Tokyo, Japan) and PowerRefractor (PlusOptiX, Nürnberg, Germany) autorefractors. Continuous objective recording of dynamic accommodation was measured with the SRW-5000, with the subject viewing a target moving from 0 to 2.50 D at 0.3 Hz through a Badal lens system. Wavefront aberrometry measures (Zywave; Bausch & Lomb, Rochester, NY) were made through undilated pupils. Subjective amplitude of accommodation was measured with the RAF (Royal Air Force accommodation and vergence measurement) rule. RESULTS: Four months after implantation best-corrected acuity was -0.01 +/- 0.16 logMAR at distance and 0.60 +/- 0.09 logMAR at near. Objectively, the static amplitude of accommodation was 0.72 +/- 0.38 D. The average dynamic amplitude of accommodation was 0.71 +/- 0.47 D, with a lag behind the target of 0.50 +/- 0.48 seconds. Aberrometry showed a decrease in power of the lens-eye combination from the center to the periphery in all subjects (on average, -0.38 +/- 0.28 D/mm). Subjective amplitude of accommodation was 2.24 +/- 0.42 D. Two years after 1CU implantation, refractive error and distance visual acuity remained relatively stable, but near visual acuity, and the subjective and objective amplitudes of accommodation decreased. CONCLUSIONS: The objective accommodating effects of the 1CU lens appear to be limited, although patients are able to track a moving target. Subjective and objective accommodation was reduced at the 2-year follow-up. The greater subjective amplitude of accommodation is likely to result from the eye's depth of focus of and the aspheric nature of the IOL.

Accommodation, Ocular↗
PubMed2005

Scotopic measurement of normal pupil size with the Colvard pupillometer and the Nidek auto-refractor.

PURPOSE: To compare prospectively, pupil size with the Nidek AR700A auto-refractor and the Colvard pupillometer. METHODS: Pupil diameter was measured in 46 eyes at 2 min intervals in a low mesopic and under photopic light conditions. RESULTS: The mean pupil diameter was 4.8+/-1.0mm with the Colvard pupillometer and 4.8+/-0.9mm with the Nidek auto-refractor in low mesopic light conditions. The mean photopic pupil diameter was 3.3+/-0.8mm with the Colvard pupillometer and 3.9+/-0.8mm with the Nidek auto-refractor. CONCLUSION: The pupil sizes are very similar with both instruments.

Adult↗
PubMed2004

The determinants and effect of shared care on patient outcomes and psychiatric admissions - an inner city primary care cohort study.

OBJECTIVE: The aim of this study was to determine the factors associated with receipt of different levels of shared care, and the effect of shared care on patient outcomes. METHOD: A total of 349 patients with severe mental illness were selected from general practice lists. Patient functioning was assessed using standardised questionnaires, and GPs completed a questionnaire about patients' shared care arrangements at baseline (response-rate 79%). Patients were followed up at 12 months. RESULTS: Receipt of high shared care was associated with greater patient satisfaction with services and social functioning at baseline (p < 0.005). Patients receiving high shared care showed greater improvements in SF-12 mental health scores at follow-up compared to low shared care groups (p = 0.02). This effect was abolished after adjustment for age, sex and psychiatric diagnosis. CONCLUSION: Receipt of high shared care was not associated with demographic or clinical characteristics. High shared care had limited value for patients in terms of improved clinical, social or general health functioning over one year.

Adult↗
PubMed2004

Surgical management of presbyopia.

Presbyopia is age-related reduction in amplitude of accommodation and the loss of the ability to change the eye's focus from far to near. It is the one of the most common age-related ailment. Traditional methods such as spectacle glasses or contact lenses are still the most widely used for correction of the problem. This article is an attempt to review the surgical options available for presbyopia.

Journal Article↗
PubMed2004

Chronic open angle glaucoma: patient awareness of the nature of the disease, topical medication, compliance and the prevalence of systemic symptoms.

PURPOSE: To study the awareness of the nature of the disease, compliance with treatment, and prevalence of systemic symptoms in a group of patients with chronic open angle glaucoma (COAG). METHOD: A structured questionnaire was designed and given to 260 consecutive COAG patients attending a general ophthalmology clinic. Questions related to the increased risk of COAG amongst family members, screening of family members, nature of field defects, variation in IOP, topical treatment and availability of a free eye test for a COAG patient in the UK were asked. Compliance and systemic symptoms were also assessed. RESULTS: Forty-one per cent (107 of 260) of patients in the study group were aware of the increased risk of COAG in family members and 45.5% (118 of 260) of patient's family members had undergone screening for COAG. Seventy-three per cent (191 of 260) of the patients were aware of their own and their family members' entitlement to a free eye test. Seventy-seven per cent of patients claimed full compliance. Thirty per cent of patients were noted to have systemic symptoms. CONCLUSIONS: The awareness of the nature of COAG in this population was low and incidence of perceived drug related systemic symptoms very high. Both of these may contribute to poor compliance.

Administration, Topical↗
PubMed2003

Predictors of depressive symptoms in older people--a survey of two general practice populations.

BACKGROUND: Studies have shown strong associations between disability, social support and depressive symptoms in older people; but socio-economic effects are less clear and little is known about the role of health locus of control. OBJECTIVE: To examine the roles of physical health, disability, social support, socio-economic factors and health locus of control as predictors of depressive symptoms in older people. METHOD: A postal survey of patients aged >/= 65 years from two London practices. Outcome measure was a score of > 5 on the 15-item Geriatric Depression Scale. Associations with other factors were examined using logistic regression and expressed as odds ratios. RESULTS: 70.4% (1602/2276) responded and provided Geriatric Depression Score 15 data, with 23.8% (381/1602) scoring > 5. After adjusting for age, sex and practice, high depression scores were associated with: (i) physical health and disability [e.g. severe versus no disability odds ratio 26.9 (15.7-46.2)]; (ii) social support [e.g. dissatisfaction with support odds ratio 4.2 (3.2-5.6)]; (iii) socio-economic [e.g. no occupational pension odds ratio 1.9 (1.5-2.4)]; (iv) health locus of control [e.g. internality 0.6 (0.6-0.7)]. After adjusting for disability, associations with general measures of physical health were reduced but still significant, while associations with social support, socio-economic factors, and health locus of control were unaffected. All four groups of factors were included in a final model for predicting depressive symptoms. CONCLUSIONS: Disability, physical health, social support, socio-economic factors, and health locus of control were all independent depression score predictors in this study. This has implications for measures to reduce depressive symptoms in older people.

Aged↗
PubMed2003

Alcohol debridement of the corneal epithelium in PRK and LASEK: an electron microscopic study.

PURPOSE: To determine the plane of cleavage of the corneal epithelium and smoothness of underlying stroma, after alcohol debridement in photorefractive keratectomy (PRK) and laser subepithelial keratectomy (LASEK). METHODS: The epithelial flap from six patients undergoing alcohol delamination of corneal epithelium before PRK and the epithelium and stroma from three eye bank donor eyes were fixed and processed for transmission (TEM) and scanning electron microscopy (SEM). The smoothness of the underlying stroma was studied by SEM and the plane of cleavage was determined by morphologic examination and morphometric measurements of basement membrane attached to the epithelial flap, using image-analysis software. RESULTS: A very smooth stromal bed, ideal for PRK was seen in the stroma of all three eye bank donor eyes after alcohol delamination. The plane of cleavage was determined to be at the hemidesmosomal attachments, including the most superficial part of the lamina lucida of the basement membrane. CONCLUSIONS: Alcohol delamination of the corneal epithelium before PRK or LASEK consistently results in a very smooth cleavage at the level of the hemidesmosomal attachments, including the superficial lamina lucida. It leaves behind a very smooth surface, which is ideal for PRK. It also allows for an intact epithelial flap to be lifted as a sheet from the corneal surface and hence is ideally suited for the LASEK technique.

Basement Membrane↗
PubMed2002

Predictability and outcomes of photoastigmatic keratectomy using the Nidek EC-5000 excimer laser.

PURPOSE: To evaluate the effect of astigmatic correction on the accuracy of the myopic and astigmatic correction in patients having photorefractive astigmatic keratectomy (PARK) and in those having photorefractive keratectomy (PRK). SETTING: Specialist excimer laser refractive clinic. METHODS: This prospective consecutive case series comprised 6097 eyes with a preoperative mean spherical equivalent (MSE) of -4.63 diopters (D) +/- 1.95 (SD) (range -0.75 to -13.00 D) and a mean cylinder of -1.13 +/- 0.73 D (range -0.50 to -6.00 D) having PARK with a Nidek EC-5000 excimer laser. Visual and refractive outcomes were assessed 12 months postoperatively and compared with those in 3004 eyes that had spherical PRK. RESULTS: At 12 months, the MSE was -0.02 +/- 0.79 D and the mean cylinder was -0.49 +/- 0.47 D in the PARK group; the MSE was -0.07 +/- 0.66 D in the PRK group. An MSE within +/-0.05 D of emmetropia was achieved by 69.8% and within +/-1.00 D, by 87.9%. The uncorrected visual acuity (UCVA) was 20/20 or better in 42.6% and 20/40 or better in 91.2%. Statistical significance (P <.001, analysis of variance) was achieved for MSE, sphere, cylinder, haze, and visual acuity (best corrected [BCVA] and UCVA) based on the preoperative cylinder. The loss of BCVA varied from 1.1% to 5.8% depending on the degree of astigmatism treated. Accuracy varied with the attempted myopic correction and the attempted astigmatic correction. CONCLUSIONS: Excimer laser PARK was an effective treatment for compound myopic astigmatism, but predictability decreased and complications increased as the attempted astigmatic correction increased.

Adult↗
PubMed2002

Mammography uptake predictors in older women.

BACKGROUND: In women aged under 65 years, socio-economic factors and general health behaviours are important predictors of mammography uptake. Little is known about whether these factors are important in older women. OBJECTIVE: To examine a broad range of mammography uptake predictors in women aged 65 and older registered with a London (UK) practice. METHODS: A survey of all female patients aged 65 and over (n = 613) in a south London practice included questions on mammography and cervical screening, general health and functional ability, socio-economic factors, mental health, health behaviours, and attitudes to health. Associations between mammography uptake and other factors were examined using logistic regression. RESULTS: The response rate was 70% (432/613). Increased age was strongly associated with decreased mammography uptake. Additionally, socio-economic factors and general health behaviours (previous cervical smear, drinking alcohol and being a non-smoker) were independently predictive of mammography uptake. Measures of physical and mental health and health attitudes were not independent predictors. Restricting analyses to the oldest women, outside the national screening programme, gave very similar results. CONCLUSIONS: In this sample of older women, socio-economic factors and general health behaviours were more predictive of mammography uptake than measures of physical and mental health or attitudes to health. Knowledge of these predictors is of increasing importance as the screening programme in the UK is extended up to age 70.

Age Factors↗
PubMed2002

New techniques in lamellar keratoplasty.

In the past years, several lamellar keratoplasty surgical techniques have been developed, modified or improved in the past years, including microkeratome assisted anterior and posterior lamellar keratoplasty, anterior lamellar keratoplasty using air-dissection or visco-dissection, sutureless posterior lamellar keratoplasty, LASIK for postkeratoplasty astigmatism, and excimer laser assisted keratophakia for keratoconus or to manage complications after LASIK. These procedures may continue to gain interest as alternative procedures for a penetrating keratoplasty in the treatment of various corneal disorders.

Corneal Transplantation↗
PubMed2002

Effect of corneal thickness on intraocular pressure measurements with the pneumotonometer, Goldmann applanation tonometer, and Tono-Pen.

PURPOSE: To compare intraocular pressure (IOP) measurements of the Ocular Blood Flow (OBF) pneumotonometer, Goldmann applanation tonometer, and Tono-Pen in eyes with normal corneas of various thicknesses. METHODS: IOP was measured with an OBF pneumotonometer, Tono-Pen and Goldmann applanation tonometer in random order in 181 eyes with normal corneas. Central corneal thickness (CCT) was measured using an ultrasonic pachymeter after all IOP determinations had been made. Right and left eyes were analyzed separately for statistical purposes. RESULTS: With all instruments, IOP varied with CCT, even though the variation in IOP was large. Readings with the OBF pneumotonometer showed a mean increase in IOP with increasing CCT of 0.28 mm Hg/10 microm, an increase of 0.23 mm Hg/10 microm with the Goldmann tonometer, and of 0.10 mm Hg/10 microm with the Tono-Pen. The OBF pneumotonometer consistently recorded comparatively higher IOPs than the other two instruments. CONCLUSIONS: The Tono-Pen is least affected by CCT when used to measure IOP in eyes with normal corneas. The OBF pneumotonometer appears to be more affected by variation in CCT than the Goldmann tonometer. This is contrary to expectations, based on the mechanism of measurement of IOP of the OBF pneumotonometer.

Cornea↗
PubMedDate not supplied

Nidek OPD-scan analysis of normal, keratoconic, and penetrating keratoplasty eyes.

PURPOSE: To determine by wavefront analysis the difference between eyes considered normal, eyes diagnosed with keratoconus, and eyes that have undergone penetrating keratoplasty METHODS: The Nidek OPD-Scan wavefront aberrometer was used to measure ocular aberrations out to the sixth Zernike order. One hundred and thirty eyes that were free of ocular pathology, 41 eyes diagnosed with keratoconus, and 8 eyes that had undergone penetrating keratoplasty were compared for differences in root mean square value. Three and five millimeter root mean square values of the refractive power aberrometry maps of the three classes of eyes were compared. Radially symmetric and irregular higher order aberration values were compared for differences in magnitude. RESULTS: Root mean square values were lower in eyes free of ocular pathology compared to eyes with keratoconus and eyes that had undergone penetrating keratoplasty. The aberrations were larger with the 5-mm pupil. Coma and spherical aberration values were lower in normal eyes. CONCLUSION: Wavefront aberrometry of normal, pathological, and eyes after surgery may help to explain the visual distortions encountered by patients. The ability to measure highly aberrated eyes allows an objective assessment of the optical consequences of ocular pathology and surgery. The Nidek OPD-Scan can be used in areas other than refractive surgery.

Corneal Topography↗
PubMedDate not supplied

Higher order aberrations with aspheric ablations using the Nidek EC-5000 CX II laser.

PURPOSE: To analyze the change in higher order aberrations in myopic and myopic astigmatic eyes following an aspheric ablation profile for laser in situ keratomileusis (LASIK) using a Nidek EC-5000 CX II excimer laser system. METHODS: We performed a retrospective audit of 38 eyes (19 patients) with myopia and myopic astigmatism. A customized aspheric transition zone profile (CATz) was used in all eyes (profile 4) with an ablation zone of 5 mm and a transition zone of 9 mm using FinalFit software and a Nidek EC-5000 CX II excimer laser system. RESULTS: Mean higher order aberrations (RMS) increased from 0.42 microm at baseline to 0.57 microm at 6-month follow-up. Mean spherical aberrations (Z12) increased from 0.02 microm at baseline to 0.33 microm after LASIK. Mean spherical aberration defocus equivalent (DEQ) increased from 0.56 microm at baseline to 1.54 at 6 months after surgery. Mean trefoil (Z6) was -0.11 microm at baseline and -0.14 microm at the 3-month examination. Mean coma (Z7) was -0.09 microm at baseline and -0.10 microm after surgery. Mean coma (Z8) was -0.03 at baseline and 0 at the 3-month examination. Mean trefoil (Z9) was -0.03 at baseline and -0.12 at the 3-month examination. CONCLUSION: The amount of postoperative higher order aberrations in these myopic eyes was acceptable. However, the clinical significance of these numerical changes in aberrations is not known.

Adult↗