Biography:

In the past Sunil Shah has collaborated on articles with Anupam Chatterjee and Neel Bhatt. One of their most recent publications is Chapter 4 - Surgical procedures. Which was published in journal .

More information about Sunil Shah research including statistics on their citations can be found on their Copernicus Academic profile page.

Sunil Shah's Articles: (11)

Assessment of the diurnal variation in central corneal thickness and intraocular pressure for patients with suspected glaucoma☆

AbstractObjectiveTo assess whether a single daily measurement using ultrasonic pachymetry gives a representative assessment of mean central corneal thickness (CCT) in patients with suspected glaucoma and whether diurnal changes in CCT are related to diurnal variations in intraocular pressure (IOP).DesignCross-sectional study.MethodCentral CCT and IOP were measured by a single observer in 56 eyes of 28 patients with suspected glaucoma using an ultrasonic pachymeter and a Goldmann tonometer. Four measurements were made over a 24-hour period: at 8:00 am, 12:00 pm, 4:00 pm, and 8:00 pm.Main outcome measuresIntraocular pressure and pachymetry.ResultsMean IOP was 19.80 mmHg at 8:00 am (95% confidence interval [CI], 18.95–20.66 mmHg), 20.38 mmHg at 12:00 pm (95% CI, 19.49–21.26 mmHg), 19.91 mmHg at 4:00 pm (95% CI, 19.99–21.83 mmHg), and 19.23 mmHg at 8:00 pm (95% CI, 18.35–20.11 mmHg). Mean CCT was 569.4 μm (95% CI, 560.2–578.7 μm), 567.6 μm (95% CI, 558.4–576.7 μm), 569.1 μm (95% CI, 559.5–578.6 μm), and 567.2 μm (95% CI, 557.9–576.4 μm) at the four respective time points. There was no significant correlation between IOP and CCT in any patient (Pearson rank correlation coefficient); nor was there any significant correlation between the mean diurnal variations of IOP and CCT.ConclusionsIn this group of patients with suspected glaucoma, there was no significant variation in CCT. Therefore, a single measurement of CCT is sufficient when assessing patients with suspected glaucoma. There was no correlation between change of IOP and change of CCT.

Results of Excimer Laser Retreatment of Residual Myopia after Previous Photorefractive Keratectomy

Background: Nine percent to 30% of all patients who undergo a single excimer laser photorefractive keratectomy (PRK) do not achieve an unaided visual acuity of 201 40 or better and may require optical correction to obtain adequate vision.Methods: The authors performed a retrospective analysis of the records of 164 patients who had undergone retreatment with the excimer laser for residual myopia after a previous PRK. Mean follow-up was 35.5 ± 15.2 weeks (range, 26-104 weeks).Results: The mean spherical equivalent (MSE) before retreatment was -2.59 ± 1.36 diopter (D) (range, -0.50 to -7.75 D). The final MSE after reablation was -0.52 - 1.36 D (range, 2.50 to -5.50). Of the 164 patients, 107 (65.2%) obtained a final refraction within 1.00 D of emmetropia and 111 (67.3%) achieved an unaided visual acuity of 20/40 or better. Only 10 patients (6.1 %) lost more than one Snellen line of bestcorrected visual acuity. The final MSE result for the subgroup of patients who had a preretreatment myopia of between -0.50 and -1.90 D (-0.31 ± 1.09 D) was significantly closer to emmetropia than that of the subgroup with a residual myopia of -4.00 to -7.75 D (-1.62 ± 1.94D).Conclusions: Excimer laser retreatment may provide a relatively safe and predictable method of correcting residual myopia after an earlier PRK with a 25% extra correction recommended for residual myopia.

Astigmatism Induced by Spherical Photorefractive Keratectomy Corrections

Purpose: The purpose of the study is to evaluate the induced astigmatism after spherical photorefractive keratectomy on the Summit Omnimed (Summit Instruments, Waltham, MA) and the Nidek EC-5000 (Nidek Co. Ltd, Aichi, Japan) excimer lasers.Methods: A total of 4269 eyes of 3289 patients were treated with a 5-mm optical zone using the Summit Omnimed excimer laser and 1825 eyes of 1303 patients treated with the Nidek EC-5000 excimer laser. The final astigmatic refractive outcome was compared with the initial refraction by vector analysis (Alpin and Jaffe method).Results: Subjective astigmatic refraction for the Summit laser reduced from a mean of -0.39 diopter (D) ± standard deviation (SD) 0.33 D (range, 0 to -2.50 D) to -0.33 D ± SD 0.41 D (range, 0 to -3.00 D). Surgically induced astigmatism (SIA) had a mean of 0.42 ± SD 0.34 D (range, 0 to 2.89 D). Mean SIA increased with increasing preoperative astigmatism by 0.60D SIA for every 1.00 D of preoperative cylinder.For the Nidek laser, subjective astigmatic refraction changed from a mean of -0.18 D ± SD 0.21 D (range, 0 to -1.25D) to -0.30 D ± SD 0.33 D (range, 0 to -3.OOD). Surgically induced astigmatism had a mean of -0.32 D ± SD 0.29 (range, 0 to 3.05 D). Mean SIA increased with increasing preoperative astigmatism by 0.47 D SIA for every 1.00 D of preoperative cylinder.Conclusions: The authors show that spherical photorefractive keratectomy corrections can induce significant astigmatic change, particularly if a large amount of preoperative astigmatism is present.

Relationship between corneal thickness and measured intraocular pressure in a general ophthalmology clinic1

AbstractObjectiveTo assess whether central corneal thickness (CCT) is a confounding factor in the classification of patients attending for glaucoma assessment in a district general hospital.DesignCross-sectional study by a single observer.ParticipantsPatients attending a general ophthalmic clinic: 235 clinically normal eyes, 52 eyes with normal-tension glaucoma (NTG), 335 eyes with primary open-angle glaucoma (POAG), 12 eyes with pseudoexfoliative glaucoma (PXE), 42 eyes with chronic angle closure glaucoma (CACG), and 232 glaucoma suspect (GS) eyes.InterventionCentral corneal thickness was measured using ultrasonic pachymetry.Main outcome measureCorrelation of CCT and diagnosis.ResultsMean CCT was 553.9 μm (95% confidence intervals [CI] for the mean, 549.0–558.8 μm) in the clinically normal eyes, 550.1 μm (95% CI, 546.6–553.7 μm) in the POAG eyes, 514.0 μm (95% CI, 504.8–523.3 μm) in the NTG eyes, 530.7 μm (95% CI, 511.2–550.1 μm) in the PXE eyes, 559.9 μm (95% CI, 546.8–573.0 μm) in the CACG eyes, and 579.5 μm (95% CI, 574.8–584.1 μm) in the GS eyes. The differences of mean CCT between the groups were highly significant (P < 0.001 analysis of variance). Eighty-five percent of eyes with NTG and only 36% of eyes with POAG had a mean CCT of 540 μm or less. Thirteen percent of eyes with POAG and 42% of GS eyes had a mean CCT greater than 585 μm.ConclusionsThe CCT measurement is desirable in patients attending for glaucoma assessment in a district general hospital to avoid misclassification resulting from the relationship between CCT and tonometric pressure. Central corneal thickness alone is not an accurate predictor for the clinical diagnosis in this group of eyes. However, many eyes diagnosed as having NTG have thin corneas, which would tend to lower the tonometrically recorded intraocular pressure (IOP), so the finding of a less-than-normal thickness cornea introduces some doubt as to the diagnosis of NTG. For the GS eyes, most eyes had thick corneas, which would tend to increase the tonometrically recorded IOP. Thus, GS eyes with modest elevation of IOP and a thick cornea may be at low risk of progressing to POAG. Thus, many patients with “high IOPs” and a thick CCT do not necessarily have high IOPs and may not need to be followed as GS eyes.

ArticlePredictability and outcomes of photoastigmatic keratectomy using the Nidek EC-5000 excimer laser1

AbstractPurpose: 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.

Epithelial debridement for secondary hyperopia following myopic excimer laser photorefractive keratectomy++++++

AbstractBackground: To evaluate epithelial debridement for the treatment of persistent hyperopia in eyes that had photorefractive keratectomy (PRK).Setting: Optimax Laser Eye Clinics, Manchester, London, Bristol, England.Methods: Epithelial debridement was performed on 46 eyes to reduce the hypermetropia following excimer laser PRK.Results: Mean age of the patients was 43 years ± 9.7 (SD). Mean refractive change was −0.51 diopter (D) ± 0.76 (range +0.75 to −2.50 D). Mean change in best corrected visual acuity (BCVA) was 0.00 Logmar units (range +0.40 to −0.20 units), although 33% of eyes lost one line or more of Logmar BCVA. Mean follow-up after debridement was 61.0 ± 26.9 weeks (range 26 to 140 weeks).Conclusions: Epithelial debridement is an unpredictable procedure to treat secondary hyperopia after PRK, producing a small mean change in spherical equivalent with a wide range of results. A significant number of eyes lost one line or more of Logmar BCVA. We therefore do not advocate epithelial debridement after PRK.

A 10-year follow up of ocular hypertensive patients within the Bolton Corneal Thickness Study: Can measured factors predict prognostic outcomes?

AbstractObjectiveThis is a case note review of a cohort of patients examining the effects of central corneal thickness (CCT), presenting intraocular pressure (IOP), age and gender on the risk of progression of ocular hypertension (OHT) to primary glaucoma (POAG) over a 10-year period.DesignCohort study with retrospective case note review.Participants and methods58 case notes from a cohort at the Bolton Royal Infirmary initially assessed 10 years ago were reviewed again. Presenting CCT, IOP, age and gender were recorded. Development of POAG was assessed by visual field and/or optic disc changes being present.Main outcome measuresThe effects of CCT, IOP, age and gender on the risk of progression of OHT to POAG were analysed in a multivariate logistic regression model following a preliminary univariate analysis.Results50 out of 116 eyes developed primary open angle glaucoma over the 10-year period. Thinner CCT (odds ratio 0.985 associated with each 1 μm increase in CCT), higher presenting IOP (odds ratio 1.131 associated with each 1 mmHg increase in IOP) and increasing age (odds ratio 1.062 associated with each 1 year increase in age) were found to be associated with progression to POAG.ConclusionPatients with a CCT of 579 μm or more, a presenting intraocular pressure of 26 mmHg or less and age 75 years or less had a lower risk of developing POAG within this cohort of patients.

Comparison of corneal biomechanics in pre and post-refractive surgery and keratoconic eyes by Ocular Response Analyser

AbstractPurposeTo compare biomechanical parameters measured by the Ocular Response Analyser (ORA) in the form of corneal hysteresis (CH), corneal resistance factor (CRF) and central corneal thickness (CCT) in eyes before and after excimer laser refractive surgery and keratoconic eyes.SettingTeaching Hospital and private eye clinic in Solihull, UK.MethodsProspective case comparison of 110 eyes selected for refractive surgery and 132 keratoconic eyes. The CH and CRF of each eye was measured by the ORA. The CCT was measured using ultrasonic pachymetry.ResultsThe mean preoperative (pre-op) CH for the normal refractive surgery eyes was 11.4 ± 1.9 mmHg, CRF 10.0 ± 1.6 mmHg and CCT 546.5 ± 33.0 μm. Post-operatively CH was 9.2 ± 2.1 mmHg, CRF 7.6 ± 1.8 mmHg and CCT 483.1 ± 40.8 μm. The values for keratoconic eyes were 9.4 ± 2.2 mmHg, 7.7 ± 2.6 mmHg and 488.1 ± 52.6 μm, respectively. The CH, CRF and CCT decreased as the severity of keratoconic eyes increased. All these parameters showed statistically significant difference between normal eyes and keratoconic eyes. This was also the case between post-operative eyes.ConclusionThe biomechanical parameters measured were very similar when comparing keratoconic and post-refractive surgery eyes.

The use of the Ocular Response Analyser to determine corneal hysteresis in eyes before and after excimer laser refractive surgery

AbstractPurposeTo compare corneal biomechanical parameters and two measures of intraocular pressure (IOP) in eyes before and after excimer laser refractive surgery, with the Ocular Response Analyser (ORA).Materials and methodsEighty normal eyes of 41 patients undergoing excimer laser refractive surgery in Birmingham, U.K. were recruited into three groups: Laser Assisted-Epithelial Keratomileusis (LASEK) (Myopes), Laser Assisted in Situ Keratomileusis (LASIK) (myopes) and LASIK (hyperopes). The preop and 3 months postop Goldmann correlated IOP (IOPg), corneal compensated IOP (IOPcc), corneal hysteresis (CH), and corneal resistance factor (CRF) were measured by the ORA. Central corneal thickness (CCT) was measured using ultrasonic pachymeter. The differences of the changes in IOPg, IOPcc, CH, CRF and CCT between the three groups were estimated. A General Linear Model was selected to investigate the influence of gender, age, initial conditions (CH, CRF, CCT, IOPcc and IOPg) and changes in CCT on the measured IOP.ResultsThe differences between the mean IOPg, CH and CRF after refractive surgery were statistically significant for all three groups. The hyperopic LASIK group had a significantly smaller change compared to the other groups (which had no statistical significance). The preop IOPg, preop CH and gender were significant predictors of the changes in measured pressure and biomechanical parameters after surgery in the myopic groups only.ConclusionCH and CRF were found to decrease after both myopic and hyperopic refractive surgery. CH and CRF measurement may prove important tools to clarify the role of corneal biomechanics for refractive surgery.

Can the accuracy of multifocal intraocular lens power calculation be improved to make patients spectacle free?

Highlights•Increased patient visual outcome expectations following lens implant surgery.•New segmental multifocal lens demonstrated improved visual outcome than previously.•Comparison of 5 conventional formulae, 1 new ray tracing technique or combination.•Results segregated into short/long axial length as per College of Ophthalmologists.•Excellent but equivalent results comparing biometry calculation formulae for power.

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