R Thomas

L V Prasad Eye Institute, Bhaganagar, Andhra Pradesh, India

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Publications (51)48.26 Total impact

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    ABSTRACT: To report progression of primary angle closure suspects (PACS) to primary angle closure (PAC) at the 5 year follow up of a population based sample. 82 of 118 PACS who could be contacted and 110 randomly selected normals from a population based survey in 1995 were invited for a follow up examination in 2000. Progression to PAC was based on the development of raised IOP or synechiae in a PACS. 50 of the 82 PACS contacted were examined. 11 (22%; 95% CI 9.8 to 34.2) developed PAC (seven synechial and four appositional); all were bilateral PACS. Two of 50 people previously diagnosed as PACS were reclassified as normal. One person among the 110 normals progressed to PAC. The relative risk of progression among PACS was 24 (95% CI 3.2 to 182.4). There was no significant difference in axial length, anterior chamber depth, or lens thickness between those who progressed and those who did not. None of the patients developed optic disc or field damage attributable to angle closure. One angle closure suspect was diagnosed to have normotensive glaucoma. In this population based study of PACS the 5 year incidence of PAC was 22%; none developed functional damage. Bilateral PACS was a clinical risk factor for progression.
    British Journal of Ophthalmology 05/2003; 87(4):450-4. · 2.81 Impact Factor
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    ABSTRACT: To evaluate the morphology of the optic nerve head in an unselected population group in south India. The study included 70 subjects forming a population based sample, selected in a random manner. Mean age was 47.5 (SD 8.7) years, mean refractive error measured -0.07 (1.11) dioptres (range -4.50 to +2.50 dioptres). Optic disc slides were morphometrically analysed. Mean optic disc area measured 2.58 (0.65) mm(2). It was statistically independent of age and refractive error. Optic disc shape was slightly vertically oval. Mean neuroretinal rim area was 1.60 (0.37) mm(2). It was significantly and positively correlated with optic disc size and optic cup size. It was independent of age, sex, refractive error, and axial length. In all subjects included in the study, the rim was smallest in the temporal horizontal optic disc sector. Mean horizontal cup/disc diameter ratio (0.66 (0.07)) was significantly (p<0.001) higher than the mean vertical cup/disc diameter ratio (0.56 (0.08)). Both ratios were highly significantly (p <0.001) and positively correlated with optic disc size. The alpha zone of parapapillary atrophy (0.84 (0.29) mm(2)), and beta zone (0.13 (0.38) mm(2)), respectively, occurred in 69 (98.6%) subjects and in eight (11.4%) subjects, respectively. They were significantly larger in the temporal horizontal sector. The alpha zone was significantly (p<0.001) larger and occurred significantly more often than beta zone. Retinal arterioles and venules were wider, and in spatial correlation, the visibility of the retinal nerve fibre layer was significantly better, in the temporal inferior disc arcade and the temporal superior arcade than in the nasal superior arcade and the nasal inferior vessel arcade. Except for the absolute size measurements these optic nerve head parameters did not differ markedly (p >0.05) from the values found in white people. South Indians and white people do not show marked differences in the morphology of the optic nerve head as measured by morphometric optic disc parameters, with the possible exception of the absolute optic disc dimensions.
    British Journal of Ophthalmology 02/2003; 87(2):189-96. DOI:10.1136/bjo.87.2.189 · 2.81 Impact Factor
  • R Thomas, T Kuriakose, R Parikh
    Indian Journal of Ophthalmology 10/2001; 49(3):203; author reply 204. · 0.93 Impact Factor
  • R Thomas, J Muliyil, P Paul
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    ABSTRACT: Ophthalmologists are frequently confronted with treatment options that claim to be better than those currently in use. Statistically significant P values are invariably provided by way of proof. For many ophthalmologists a simple look at this revered P value is enough evidence that a statistically significant result has indeed been obtained. Unfortunately, traditional interpretation of a study based on the P value at an arbitrary cut-off (P<0.05 or any other value) limits the ability to fully appreciate clinical implications. In this article the authors introduce the reader to and illustrate the use of "confidence intervals" as opposed to P values in examining the applicability of study results. Further, what is statistically significant may not necessarily be clinically significant; perhaps not enough for the practitioner to change from the currently preferred method of treatment. To resolve this, the authors have also used common ophthalmic examples to introduce the "number needed to treat", as a simple clinical approach for the practising ophthalmologist wishing to assess the clinical significance of treatment options.
    Journal of the Indian Medical Association 10/2001; 99(10):561-4, 566.
  • R Thomas, R George
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    ABSTRACT: Visual field testing is mandatory for many ophthalmic conditions including glaucoma. The current gold standard for visual field testing is automated perimetry. In this article we familiarize the reader with the components of an automated perimetry printout. We describe a systematic approach that leads to a thorough interpretation of the printout. With the help of examples the reader should be able to learn to identify a normal field, detect the presence of a field defect, determine whether it is due to glaucoma, and establish progression, if any.
    Indian Journal of Ophthalmology 07/2001; 49(2):125-40. · 0.93 Impact Factor
  • S Korah, R Thomas, J Muliyil
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    ABSTRACT: (1) To determine the agreement between optical and ultrasound pachometry for central corneal thickness measurements used to "correct" applanation intraocular pressure (IOP) readings. (2) To determine the inter- and intra-observer variability of optical and ultrasound pachometry. Central corneal thickness (CCT) was measured in a masked manner using optical and ultrasound pachometry in 50 normal eyes. To assess intra- and inter-observer variability, multiple masked measurements were obtained in 51 eyes (optical pachometry) and 34 eyes (ultrasound pachometry). Agreement was determined by a published technique that uses the mean of the differences, standard error (SE) and standard deviation (SD). The mean difference in CCT between optical and ultrasound pachometry was 0.001 mm (SD 0.031 mm; SE 0.00439 mm). The mean inter-observer difference for the optical pachometer was 0.019 mm (SD 0.049 mm; SE 0.0069); the mean intra-observer difference was 0.003 mm (SD 0.017; SE 0.0.0024). The mean inter-observer difference for ultrasound pachometry was 0.001 mm (SD 0.009; SE 0.0015) and the mean intra-observer difference was 0.002 mm (SD 0.011; SE 0.0019). Ultrasound pachometry is the more reliable method for the measurement of central corneal thickness used to correct applanation IOP values. Optical pachometry had good intra-observer variability. The range of error in IOP correction for corneal thickness (inter-observer) that can occur using the ultrasound pachometer is -1.2 mmHg to +1.4 mmHg as compared to -5.6 mmHg to +8.5 mmHg with the optical pachometer.
    Indian Journal of Ophthalmology 01/2001; 48(4):279-83. · 0.93 Impact Factor
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    ABSTRACT: To determine whether the use of pattern standard deviation instead of corrected pattern standard deviation, as part of Anderson's criteria, makes a difference in categorizing a single field printout using the full threshold strategy on the Humphrey's Field Analyzer. Forty-eight patients with glaucomatous field defects of varying severity underwent full threshold perimetry on the Humphrey's Field Analyzer. The third field of one eye was used for the study. The agreement between CPSD and PSD alone was determined. Each field was then categorized using Anderson's criteria first using CPSD and then PSD. The kappa statistic was used to determine agreement in both situations. The agreement between CPSD and PSD alone, as determined by kappa, was 0.77. The kappa statistic for categorization using Anderson's criteria was 0.82; the weighted kappa was 0.92. There was almost perfect agreement using the PSD instead of CPSD as part of Anderson's criteria. This substitution seems valid for the spectrum of field defects used in this series, at least for the full threshold programs.
    Journal of Glaucoma 01/2001; 9(6):480-2. DOI:10.1097/00061198-200012000-00010 · 2.43 Impact Factor
  • R Thomas, S Korah, J Muliyil
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    ABSTRACT: To determine the effect of central corneal thickness (CCT) on applanation tonometry and any resultant misclassification of normals as ocular hypertension. The central corneal thickness was measured using the ultrasound pachometer in 50 normals, 25 glaucoma and 23 ocular hypertensive patients. The student's "t" test was used to determine any significant difference in CCT between the three groups. There was a statistically significant difference in the mean CCT of the ocular hypertensives (0.574 +/- 0.033 mm) as compared to the glaucomas (0.534 +/- 0.030 mm) and normals (0.537 +/- 0.034 mm). Applying the described correction factor for corneal thickness, 39% of eyes with ocular hypertension were found to have a corrected IOP of 21 mmHg or less. Increased corneal thickness in ocular hypertension may lead to an overestimation of IOP in 39% of cases. Measurement of central corneal thickness is advisable when the clinical findings do not correlate with the applanation IOP.
    Indian Journal of Ophthalmology 07/2000; 48(2):107-11. · 0.93 Impact Factor
  • R Thomas, T Kuriakose, R George
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    ABSTRACT: A surgical approach designed to reliably attain the modern goal of small incision cataract surgery 99.8% of the time is described. Phacoemulsification as well as a manual small incision technique is utilised to achieve the desired outcome as often as possible and for all types of cataracts. The logic, and required surgical steps are described and illustrated. This surgical technique allows the advantages of small incision surgery to be reliably achieved. The method is flexible and allows decisions and steps to be modified depending on the skill and comfort zone of the individual surgeon.
    Indian Journal of Ophthalmology 07/2000; 48(2):145-51. · 0.93 Impact Factor
  • Source
    R Thomas, T Kuriakose
    Community eye health / International Centre for Eye Health 02/2000; 13(35):38-9.
  • A Mathai, R Thomas
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    ABSTRACT: To report the incidence, management and complications of nucleus dislocation into the vitreous during phacoemulsification. Retrospective review of 1250 consecutive phacoemulsification performed by consultants and residents in a teaching hospital. The incidence of nucleus drops was 0.8% (10 out of 1250). Loss of nuclear fragments occurred during phacoemulsification in 9 patients. In one, the dislocation was caused by hydro-dissection. All except one patient (who refused further intervention) underwent pars plana vitrectomy with removal of nuclear fragments. Eight of them had intraocular lens (IOL) inserted at the time of cataract surgery or at vitrectomy; one patient was scheduled for a secondary IOL. Postoperative best corrected visual acuity ranged from 6/24-6/6; 8 patients achieved a vision of 6/12 or better. Complications included cystoid macular oedema (5 patients), retinal break (1 patient) and retinal detachment (1 patient). Appropriate management of posteriorly dislocated nucleus can restore good visual acuity. The use of phacoemulsification mandates availability of referral facilities for management of complications.
    Indian Journal of Ophthalmology 10/1999; 47(3):173-6. · 0.93 Impact Factor
  • R Thomas, T Arun, J Muliyil, R George
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    ABSTRACT: To report the effect of laser peripheral iridotomy on the angles of eyes with chronic angle closure glaucoma. The hospital records of 171 consecutive patients with chronic primary angle closure glaucoma (CPACG) seen between October 1994 and March 1997 were analyzed to study the gonioscopic outcome of laser peripheral iridotomy (LPI). Success was defined as open angles (with or without medications for intraocular pressure (IOP) control) following LPI at the 1 month follow-up. Forty-seven eyes of 34 patients had chronic appositional angle closure glaucoma (CAACG), and 186 eyes of 124 patients had chronic synechial angle closure glaucoma (CSACG). Seventy eyes of 57 patients that underwent primary trabeculectomy for advanced disease were excluded from the study. Two hundred thirty-three eyes of 158 patients underwent LPI; the angles could be opened in 171 eyes (73.4%; confidence interval 67.7% to 79.1%) of 117 patients. Medications to control the IOP were required in 25 eyes (10.7%) of 19 patients. Fifty-four eyes of 34 patients that did not respond to LPI underwent argon laser gonioplasty. Gonioplasty was successful in opening at least 180 degrees of the angle in all eyes. There was no significant difference in success between CAACG (74.5%) and CSACG (73.1%). Age, IOP, and field loss were not predictors of outcome. There was perfect concordance of results between the 2 eyes of patients who had bilateral LPI. In this series, laser iridotomy was successful in opening the angle in 73.4% of eyes. Gonioplasty opened the angle in all eyes that underwent this procedure. The effect of iridotomy on one eye was predictive of the effect on the fellow eye.
    Ophthalmic surgery and lasers 07/1999; 30(7):547-53.
  • S Korah, R Thomas, J Muliyil
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    ABSTRACT: Ophthalmologists are often confronted with difficult clinical management problems. In such cases, even published experience may be limited; consequently multiple, generally unproven management options are usually available. When placed in such situations, most of us decide on the most appropriate course of action based on intuition or (limited) previous experience. In this article, we use examples to introduce the concept of decision analysis, a method of generating objective decisions for complex clinical problems.
    Indian Journal of Ophthalmology 04/1999; 47(1):41-8. · 0.93 Impact Factor
  • R P Copt, R Thomas, A Mermoud
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    ABSTRACT: To determine the effect of central corneal thickness (CCT) on the measurement of intraocular pressure (IOP) and on the resultant reclassification of patients as having primary open-angle glaucoma (POAG), normal tension glaucoma (NTG), or ocular hypertension (OHT). Intraocular pressure (Goldmann applanation tonomety) and CCT (ultrasound pachymetry) were measured in 22 patients with NTG, 49 with POAG, 44 with OHT and in 18 control subjects. The CCT was used to obtain a corrected value for the IOP and to reclassify the type of glaucoma. There was no significant difference in CCT between controls (552 +/- 35 microns) and patients with POAG (543 +/- 35 microns), but the CCT in the group with NTG (521 +/- 31 microns) was significantly lower than that in the control group or the group with POAG (P < .001), and the CCT in the group with OHT (583 +/- 34 microns) was significantly higher than in controls or patients with POAG (P < .001). Correcting IOP for corneal thickness, 31% of the patients with NTG could be reclassified as having POAG, and 56% of the patients with OHT as normal. Patients with NTG have a thinner CCT than do patients with POAG or controls. Underestimation of the IOP in patients with POAG who have thin corneas may lead to a misdiagnosis of NTG, while overestimation of the IOP in normal subjects who have thick corneas may lead to a misdiagnosis of OHT.
    Archives of Ophthalmology 02/1999; 117(1):14-6. · 4.49 Impact Factor
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    ABSTRACT: We retrospectively analyzed 135 eyes with phacolytic glaucoma. A trabeculectomy was added to standard cataract surgery if symptoms endured for more than seven days, or if preoperative control of intraocular pressure (IOP) with maximal medical treatment was inadequate. In the early postoperative period, IOP was significantly lower in the combined surgery group (89 eyes) compared to the cataract surgery group (46 eyes) (p < 0.001). At 6 months there was no difference in IOP or visual acuity between the two groups. There were no serious complications related to trabeculectomy. It is reasonable to conclude that in eyes with a long duration of phacolytic glaucoma, addition of a trabeculectomy to cataract surgery is safe, prevents postoperative rise in intraocular pressure and decreases the need for systemic hypotensive medications. A randomized trial is on to further address this question.
    Indian Journal of Ophthalmology 09/1998; 46(3):139-43. · 0.93 Impact Factor
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    ABSTRACT: Glaucoma is fast emerging as a major cause of blindness in India. In order to estimate the prevalence of primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG) in an urban South Indian population, we examined 972 individuals aged 30-60 years, chosen using a cluster sampling technique from 12 census blocks of Vellore town. They underwent a complete ocular examination, including applanation tonometry and gonioscopy, at the Medical College Hospital. Characteristic field defects on automated perimetry was a diagnostic requisite for POAG. Prevalence (95% CI) of POAG, PACG, and ocular hypertension were 4.1 (0.08-8.1), 43.2 (30.14-56.3), and 30.8 (19.8-41.9) per 1,000, respectively. All the PACG cases detected were of the chronic type. Hitherto unavailable community-based information on primary glaucoma in our study population indicates that PACG is about five times as common as POAG.
    Indian Journal of Ophthalmology 07/1998; 46(2):81-6. · 0.93 Impact Factor
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    ABSTRACT: The use of artificial drainage devices (ADDs) or "setons" in glaucoma surgery is generally restricted to patients with refractory glaucoma at high risk for failure from conventional filtration surgery. ADDs, both valved and nonvalved are currently available in this country. Recently, some of these devices have been propogated as primary treatment even for primary glaucomas. This article examines the role of ADDs in the modern management of the glaucomas. Specific indications for ADDs and methods to reduce the complication of overfiltration are discussed. The use of antimitotics, such as 5-fluorouracil or mitomycin, with traditional filtration has decreased the indications for ADDs. The literature and our experience confirm that currently there is no role for use of ADDs as a primary procedure in most glaucomas.
    Indian Journal of Ophthalmology 04/1998; 46(1):41-6. · 0.93 Impact Factor
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    ABSTRACT: Patients for cataract surgery in India routinely undergo preoperative syringing to rule out chronic dacryocystitis. We determined the sensitivity and specificity of the clinical test of regurgitation on pressure over the lacrimal sac (ROPLAS) as a screening test for chronic dacryocystitis and compared it to syringing. 621 consecutive outpatients who needed syringing for various reasons (including 318 who had routine syringing prior to cataract surgery) were examined in a masked manner for regurgitation on pressure over the lacrimal sac. They then underwent syringing by a trained (masked) observer. The sensitivity and specificity of ROPLAS were 93.2% and 99.3%, respectively. Using a 6.6% prevalence of chronic dacryocystitis (the prevalence in our cataract population), the negative predictive value of the test was 99.5%. In the presence of regurgitation of pressure over the sac, the high specificity of ROPLAS confirms chronic dacryocystitis. In view of the opportunity costs, when ROPLAS is negative, preoperative syringing in cataract is perhaps unnecessary, unless the findings are equivocal or the index of suspicion for chronic dacryocystitis is very high.
    Indian Journal of Ophthalmology 01/1998; 45(4):211-4. · 0.93 Impact Factor
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    R Thomas, J Muliyil
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    ABSTRACT: Data obtained from surveys using distant direct ophthalmoscopy (DDO) with an undilated pupil for the detection of cataracts suggest an annual incidence of 3.8 million cataracts and over 9 million cataract-blind people in India today. We recalculated the projections after adjusting for the sensitivity and specificity of DDO. Our calculations suggest that the incidence of cataract may have been overestimated by approximately 60%; corroborative evidence is provided. The specificity and sensitivity of diagnostic tests used in surveys may distort the projected figures and have adverse implications for the planning of services.
    The National medical journal of India 01/1998; 11(4):182-4. · 0.91 Impact Factor
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    ABSTRACT: The increasing popularity of phacoemulsification in our country raises important training issues. We prospectively analyzed the incidence of complications and visual outcomes in the initial 70 phacoemulsifications (70 patients) performed by the first two residents learning phacoemulsification in our training programme. Both were experienced in standard (manual) extracapsular cataract extraction. Postoperative follow up of 6 weeks or longer was available in 59 eyes. The 11 patients (11 eyes) lost to follow up did not have any intra-operative complications. The overall incidence of vitreous loss was 10%, similar to the frequency of this complication (determined retrospectively) in the first 70 standard extracapsular cataract extractions performed by the same residents. Intraocular lenses (IOL) were successfully implanted in 62 eyes, as planned. One IOL dislocated into the vitreous was successfully repositioned. Other complications encountered included superior corneal edema (3 eyes), iris damage inferiorly (7 eyes) and clinical cystoid macular edema (5 eyes). A best corrected visual acuity of 6/12 or better was obtained in 56 (94.8%) of the 59 eyes available for the six week follow up. In the eyes with vitreous loss, 6 out of 7 had visual acuity better than 6/12. No nuclei were lost into the vitreous. The rate of surgical complications for residents learning phacoemulsification in a supervised manner can be acceptably low.
    Indian Journal of Ophthalmology 01/1998; 45(4):215-9. · 0.93 Impact Factor

Publication Stats

688 Citations
48.26 Total Impact Points

Institutions

  • 1994–2003
    • L V Prasad Eye Institute
      Bhaganagar, Andhra Pradesh, India
  • 1994–2001
    • Christian Medical College Vellore
      • Department of Ophthalmology
      Velluru, Tamil Nadu, India
  • 1999
    • University of Lausanne
      Lausanne, Vaud, Switzerland
  • 1998
    • National Research and Education Network of India (ERNET)
      Bengalūru, Karnātaka, India
  • 1996
    • University of Sydney
      Sydney, New South Wales, Australia