Design and development of a noninvasive ocular pressure estimator.

SIGNIFICANCE: A snapshot intraocular pressure (IOP) is ineffective in identifying the IOP peak and fluctuation, especially during sleep. Because IOP variability plays a significant role in the progression of glaucoma, monitoring the IOP, especially during sleep, is essential to capture the dynamic nature of IOP. PURPOSE: We aimed to design an ocular pressure estimator (OPE) that can reliably and accurately measure the IOP noninvasively over closed-eyelid condition. METHODS: Ocular pressure estimator works on the principle that the external pressure applied by raising the IOP of the eyeball is transmitted through a compressible septum to the pressure sensor, thus recording the IOP. A fluid-filled pouch with a pressure sensor was placed over a rubber glove mimicking the eyelid (septum), covering the cornea of enucleated goat eyeballs. A pressure-controlled setup was connected to a goat cadaver eye, which was validated by a rebound tonometer. Cannulation of eyeballs through the lower limbus had the least difference from the control setup values documented using rebound tonometer, compared with cannulation through the optic nerve. Intraocular pressures ranging from 3 to 30 mmHg was induced, and the outputs recorded using OPE were amplified and recorded for 10 minutes (n = 10 eyes). We stratified the randomization of the number of times and the induced pressures. RESULTS: The measurements recorded were found to be linear when measured against an IOP range of 3 to 30 mmHg. The device has excellent reliability (intraclass correlation coefficient, 0.998). The repeatability coefficient and coefficient of variations were 4.24 (3.60 to 4.87) and 8.61% (7.33 to 9.90), respectively. The overall mean difference ± SD between induced IOP and the OPE was 0.22 ± 3.50 (95% confidence interval, -0.35 to 0.79) mmHg across all IOP ranges. CONCLUSIONS: Ocular pressure estimator offers a promising approach for reliably and accurately measuring IOP and its fluctuation noninvasively under a condition mimicking a closed eye.

Visual Field Evaluation Using Zippy Adaptive Threshold Algorithm (ZATA) Standard and ZATA Fast in Patients With Glaucoma and Healthy Individuals.

Purpose: To evaluate visual fields obtained with Zippy Adaptive Threshold Algorithm (ZATA) Standard and ZATA Fast from patients with glaucoma and healthy individuals. Methods: Fifty-five patients with glaucoma (median mean deviation [MD], -7.6 dB; interquartile range [IQR], -15.3 to -2.6 dB) and 22 healthy participants (median MD, -0.6 dB; IQR, -1.7 to 0.2 dB) performed ZATA Standard and ZATA Fast tests on a Henson 9000 perimeter and Swedish Interactive Thresholding Algorithm (SITA) Standard and SITA Fast tests on a Humphrey Field Analyzer. Tests were repeated within 90 days (median, 14 days; range, 7-26 days) to evaluate the test-retest variability. Results: The mean difference between the MD of the ZATA Standard and SITA Standard tests was 1.7 dB (95% confidence interval [CI], 0.9-2.4). Between ZATA Fast and SITA Fast, it was 0.9 dB (95% CI, 0.2-1.5 dB). Although there were systematic differences between the distributions of sensitivity estimates with ZATA and SITA, they did not affect the overall representation of damage by these tests. ZATA Standard and ZATA Fast were approximately 30% and 6% faster, respectively, than the corresponding SITA tests. Conclusions: ZATA Standard and ZATA Fast are suitable for clinical practice. However, differences between ZATA and SITA tests suggest that they should not be used interchangeably when patients with glaucoma are followed over time. Translational Relevance: This study examined the characteristics of ZATA visual field tests in a clinical population, and it supports the adoption of these tests for assessing patients with glaucoma.

Does the sampling frequency of an eye tracker affect the detection of glaucomatous visual field loss?

PURPOSE: Evidence suggests that eye movements have potential as a tool for detecting glaucomatous visual field defects. This study evaluated the influence of sampling frequency on eye movement parameters in detecting glaucomatous visual field defects during a free-viewing task. METHODS: We investigated eye movements in two sets of experiments: (a) young adults with and without simulated visual field defects and (b) glaucoma patients and age-matched controls. In Experiment 1, we recruited 30 healthy volunteers. Among these, 10 performed the task with a gaze-contingent superior arcuate (SARC) scotoma, 10 performed the task with a gaze-contingent biarcuate (BARC) scotoma and 10 performed the task without a simulated scotoma (NoSim). The experimental task involved participants freely exploring 100 images, each for 4 s. Eye movements were recorded using the LiveTrack Lightning eye-tracker (500 Hz). In Experiment 2, we recruited 20 glaucoma patients and 16 age-matched controls. All participants underwent similar experimental tasks as in Experiment 1, except only 37 images were shown for exploration. To analyse the effect of sampling frequency, data were downsampled to 250, 120 and 60 Hz. Eye movement parameters, such as the number of fixations, fixation duration, saccadic amplitude and bivariate contour ellipse area (BCEA), were computed across various sampling frequencies. RESULTS: Two-way ANOVA revealed no significant effects of sampling frequency on fixation duration (simulation, p = 0.37; glaucoma patients, p = 0.95) and BCEA (simulation, p = 0.84; glaucoma patients: p = 0.91). BCEA showed good distinguishability in differentiating groups across different sampling frequencies, whereas fixation duration failed to distinguish between glaucoma patients and controls. Number of fixations and saccade amplitude showed variations with sampling frequency in both simulations and glaucoma patients. CONCLUSION: In both simulations and glaucoma patients, BCEA consistently differentiated them from controls across various sampling frequencies.

Finite element method for estimation of applanation force and to study the influence of intraocular pressure of eye on tonometry.

PURPOSE: Discover the associations of force of applanation on the eye with the plunging depth of the cornea and quantify them. The results will be utilized as the feedback parameter in the new prototype development of eye care instruments as additional force may damage the internal structure of the eye or may result in erroneous output. METHOD: A finite element-based eye model is designed utilizing the actual dimensions of the human eye. A standardized tonometer is designed and the simulation is carried out at predetermined deformation of the cornea to find the force of applanation on the cornea during tonometry. Adding on, the influence of IOP during tonometry is analyzed for a range of plunging depths of the cornea. RESULTS: The graphical results inferred the linear relation between the force of applanation with the deformation of the cornea and the results are quantified. The resulting deformation and stress plot of FEM based simulation approach is analyzed and observations regarding deformations and stress are made. CONCLUSION: The human eye is successfully developed and also computed force on the cornea during tonometry is validated. The inference drawn from the deformation plot and stress plot is that the junction of cornea-sclera along with cornea-tonometer periphery undergo maximum deformation and experiences the highest stress compared to other areas of the eye while during tonometry.

Role of microperimetry in evaluating disease progression in age-related macular degeneration: a scoping review.

PURPOSE: Recent research has found variable evidence on the role of mesopic and dark-adapted scotopic microperimetry assessment in age-related macular degeneration. This scoping review summarises how mesopic and scotopic microperimetry can be used to assess disease progression in age-related macular degeneration and identifies gaps in the literature. METHODS: A population, concept, and context approach was used to develop the search strategy. Ovid MEDLINE, EMBASE, Cochrane Library, PubMed, CINAHL Plus, Web of Science, and SCOPUS databases were used to conduct the literature search. The key search terms used in the databases were age-related macular degeneration and microperimetry. RESULTS: Twelve studies were eligible and included in the review. All the studies (n = 12) were conducted in European countries [Germany (9), Italy (2), and the United Kingdom (1)]. The mesopic and scotopic sensitivities were measured using the Nidek scotopic microperimeter (MP1-S) (n = 6), scotopic Macular Integrity Assessment device (S-MAIA) (n = 5), and both MP1-s and S MAIA (n = 1). 83.3% (n = 10) studied (cross-sectional design) on mesopic, scotopic microperimetry and found reduced rod (scotopic) photoreceptors sensitivities compared to cone (mesopic) photoreceptors sensitivities in patients with small and reticular pseudodrusen despite having good visual acuity. Only 16.7% (n = 2) of studies followed participants with reticular drusen/large drusen for three years (longitudinal design) and found reduced scotopic over mesopic sensitivity at baseline and localized mesopic with profound scotopic sensitivity loss during follow-ups. CONCLUSION: Scotopic sensitivity is a better functional indicator than mesopic sensitivity to understand early and intermediate age-related macular degeneration progression. The evidence from longitudinal studies is debatable due to the limited stimuli range of existing microperimeters, smaller sample size, and lost follow-ups.

Development and validation of competency framework for teaching management of refractive errors: A participatory Delphi approach.

PURPOSE: Competency-based education and assessment are globally trending, also embraced by recently announced National education policy 2020, India. Medical programs are rapidly transforming to produce competent health professionals, to satisfy public health requirements. This paper describes Delphi study with a participatory approach, to develop a competency matrix required for training of eye care professionals. METHODS: Scoping review of literature formulated the baseline architecture of competency framework identifying two core competencies for management of refractive error, namely, "visual function assessment" and "optical technology management." The Delphi technique was employed for the development of a competency matrix with detailed knowledge, skills, and attitude (KSA) definitions for all competency elements. A heterogeneous group including optometry practitioners, academicians, researchers, association representatives, and industry representatives accomplished the objective in four rounds. RESULTS: Delphi study resulted in defining two competency clusters (CC): "CC1: Refraction" with 10 units and 43 elements and "CC2: Dispensing optics" with 8 units and 54 elements. KSA components of each of competency elements were identified and mapped with applied optics curriculum in the optometry program. CONCLUSION: Participation of all stakeholders of the educational system is essential and beneficial for nurturing of the competent workforce in healthcare. It helps build a curriculum not only having theoretical knowledge and skills but also the attitude and behavioral component of measurable competencies that satisfies the needs of the local healthcare system. This study has evolved a comprehensive competency matrix highlighting essential competencies required for the effective management of refractive error.

Efficacy of blink software in improving the blink rate and dry eye symptoms in visual display terminal users - A single-blinded randomized control trial.

PURPOSE: Dry eye disease (DED) is a multifactorial disease, more prevalent among visual display terminal users. Reduced blink rate is a risk factor to dry eye disorder, innovative means to remind to blink while using computers can be helpful. METHODS: Single-blinded Randomized Control Trial enrolled computer users with dry eye. Allocation concealment was done using opaque envelope and principal investigator was blinded. After baseline examination, eligible participants were randomized to intervention group (appearance of bars is 8 times/min) and control group (appearance of bars is 1 time/min). Participants from both groups used the software for 15 days, came for first follow up, and did not use the software for next 15 days until second follow-up examination. During each visit, detailed eye examination was done including blink rate, tear film break up time, and Ocular Surface Disease Index score. RESULTS: Forty-six participants (women n = 31; men n = 15) with a mean age of 28.02 (±6.295) years completed the study. Four participants were excluded from analysis because of early dropout. In the intervention group (n = 23) and control group (n = 23), participants were allocated. At the end of first phase, there was statistically significant difference in OSDI score (P = 0.021). Statistically significant difference was noticed in OSDI (P = 0.014) and blink rate (P = 0.049) as baseline, and final visit data were compared. CONCLUSION: "Blink-Blink" software with 8 reminders/min improved DED-related symptoms by increasing the blink rate. The carry-over effect after cessation of Blink-Blink software in improving blink rate was maintained even after 1 month. TRIAL REGISTRATION: : Clinical Trials Registry-India (CTRI): CTRI/2018/08/015176.

Revitalizing journal clubs: Millennial perspectives for enhancing student learning and engagement.

Background: Current trends in health professions education are aligned to meet the needs of the millennial learner. The aim of this study was to identify learners' perceptions of an ongoing journal club (JC) activity in the optometry curriculum and evaluate the utility and efficiency of this method in promoting student learning. Methods: A qualitative approach with a phenomenological research design was adopted. The perceptions of undergraduate and postgraduate optometry students about JCs were captured using focus group discussions. A narrative thematic analysis was done using the verbatim transcripts and moderator's notes. Results are reported using "consolidated criteria for reporting qualitative research" guidelines. Results: A total of 33 optometry students participated in the study. Data analysis revealed three major themes related to (i) The ongoing practice of JC, (ii) student perceptions of JC and its relevance in facilitating student learning, and (iii) suggestions for modification of JC for achieving optimal educational outcomes. Discussion: Student feedback indicates that an instructional redesigning of JC is necessary, considering the characteristics and expectations of the current generation of learners and the rapid strides made in the field of educational technology. The recommendations provided are likely to resurrect an age-old approach that still has educational relevance if blended with collaborative learning formats and appropriate technology.

Comparison of endpoint of subjective cycloplegic refraction with artificial aperture and post-mydriatic test among adults with refractive error.

PURPOSE: There is a need to understand the requirement for the post-mydriatic test (PMT) among adults for the final prescription of spectacles as this test increases the cost of eye care and causes inconvenience to the patient because of the additional visit to an eye care practitioner. We aim to compare the cycloplegic subjective refraction using apertures of various sizes and PMT in an adult population. METHODS: This prospective crossover study was conducted under standard settings in an eye clinic. Adult individuals between 18 and 35 years of with emmetropia and various degrees of ametropia participated in this study. Individuals with known ocular pathology were excluded. Non-cycloplegic objective refraction was performed followed by subjective refraction. Cycloplegic objective refraction was performed followed by subjective refraction with custom designed artificial apertures. After a washout period of cycloplegic, PMT was performed. The distribution of data was tested using the Kolmogorov-Smirnov test. Depending on the distribution of the data, either parametric or nonparametric test was done. RESULTS: Fifty-nine eyes of thirty individuals with a mean (±SD) age of 23(±4) years with a male: female ratio of 1:4 participated in this study. A comparison of measures of PMT and subjective refraction with 2, 3, 4, 5, and 6 mm aperture under cycloplegic effect using the Friedman test rendered a Chi square value (df = 5) of 1.92 which was not statistically different (P = 0.86). CONCLUSION: Performing subjective refraction with an appropriate spherical and cylindrical endpoint under cycloplegic effect with appropriate aperture overcomes the necessity of PMT.

Agreement and repeatability of Icare ic100 tonometer.

PURPOSE: To find the agreement and repeatability of Icare ic100 tonometer. METHODS: We included 150 subjects above the age of 18 years for this cross-sectional, multicenter study with intraocular pressure (IOP) ≥7 mmHg. After the initial ophthalmic examination, two masked examiners took five IOP measurements using three different instruments; Icare ic100, Icare TA01i, and Goldmann applanation tonometer (GAT) in only one eye of the participants. Comparison of agreement of IOP using different instruments was quantified with intraclass correlation coefficient (ICC) using the two-way random effects models of absolute agreement and Cronbach's alpha. The test-retest variability of the instruments was assessed by deriving repeatability coefficient (RC) and coefficient of variation (CV). RESULTS: Agreement between the tonometers across the different IOP groups had no statistically significant difference in their mean IOP. Icare ic100 was found to have good reliability across all IOP groups (ICC value >0.78) when compared with Icare TA01i. In comparison with GAT, Icare ic100 showed good reliability across all IOP groups (ICC >0.87) except >16 to <23 mmHg group where it showed moderate reliability (ICC = 0.52). Icare ic100 showed good repeatability with RC and CV of 2.67 and 4.89, respectively. CONCLUSION: Icare ic100 rebound tonometer can measure IOP with relatively small measurement error and can provide a reliable and repeatable reading in comparison with GAT across a wide pressure range without hampering corneal health.

Performance of Plusoptix A09 Photo Screener in Refractive Error Screening in School Children Aged between 5 and 15 Years in the Southern Part of India.

PURPOSE: To evaluate the performance of Plusoptix A09 in detecting ametropia, warranted against frequently-used technique of retinoscopy in children attending school (5-15 years) and its probability as a screening tool. METHODS: This study was the subset of a larger epidemiological study visual acuity refractive error squint conducted in schools to determine the prevalence of ocular morbidity among the 5-15 years' school children population. Every 7th student in the class (each school had mean value of 100 students) was randomly selected for this study after ascertaining their eligibility as per the inclusion criteria. A cohort of a total of 150 children within the age group of 5-15 (mean, 10.21 ± 2.83) years were recruited from 11 schools of Udupi district. Students with best corrected visual acuity of 20/20, refractive error within ±5.00 diopter (D), without any eccentric fixation, and no history of ocular pathology or seizures were recruited. Refractive error was tested by Plusoptix photorefractor followed by non-cycloplegic and cycloplegic retinoscopic techniques. The examiners performing these tests were masked and unware of the findings. Bland Altman plotted the agreement between the techniques, followed by the receiver operating characteristic curve (ROC), and sensitivity of Plusoptix. RESULTS: One-way analysis of variance calculated statistical differences among Plusoptix, objective retinoscopy, and cycloplegic retinoscopy for mean spherical value (1.12 ± 1.16 D, 0.65 ± 0.69 D, and 0.8 ± 0.82 D), cylindrical value (-0.83 D ± 1.27, -0.32 D ± 0.86, and -0.34 D ± -0.93), and spherical equivalent value (0.71 D ± 1.06, 0.45 D ± 0.7, and 0.61 D ± 0.81), with P = 0.0001, 0.0001, and 0.097, respectively. Bland Altman plots showed good agreement for spherical equivalent values of Plusoptix and objective retinoscopy. However, the area under the ROC curve (0.386) suggests that lower diagnostic ability of this device in this age group population in comparison to retinoscopy (0.575) with the sensitivity and specificity of Plusoptix was 69.2% and 84.8%. CONCLUSIONS: This study fails to report ideal sensitivity mandated for a screening tool, although good specificity and agreement are observed. Along with retinoscopy, this tool will be effective in screening a children's population aged between the age group of 5 and 15 years.

Prevalence of visual impairment in school-going children among the rural and urban setups in the Udupi district of Karnataka, India: A cross-sectional study.

AIM: The aim of this study is to estimate the prevalence of visual impairment among school-going children in Udupi district, Karnataka. MATERIALS AND METHODS: A cross-sectional study across eleven schools from both urban and rural parts of Udupi taluk was conducted to report the magnitude of visual impairment among the schoolchildren. Complex survey design was used in allocating the sample size through stratification and clustering. Totally 1784 schoolchildren between the age groups of 5 and 15 years participated in the study. Presenting visual acuity and objective refraction was measured using computerized logMAR acuity charts and Plusoptix A09 photorefractor, respectively. Manifest ocular deviation or squint was also recorded. RESULTS: The mean age of the students was found to be 10.62 ± 2.72 years. The prevalence of visual impairment, i.e., visual acuity worse than or equal to 20/40 in the better eye was found to be 4.32% (95% confidence interval: 3.38%, 5.26%). The prevalence rate was significantly higher among students from urban area (5.6%) compared to those from rural area (3.6%) (P = 0.011). CONCLUSION: Visual impairment was found to be 4.32% in the school-going population of Udupi district. Effective and user-friendly devices aided the visual deficit screening including refractive error and squint.

Glaucoma and its association with obstructive sleep apnea: A narrative review.

Obstructive sleep apnea (OSA) is one of the systemic risk factors for glaucoma which causes irreversible visual field (VF) damage. We reviewed the published data of all types of studies on the association between these two conditions and papers regarding functional and structural changes related to glaucomatous damage using Scopus, web of science, and PubMed databases. There is evidence that the prevalence of glaucoma is higher in OSA patients, which independent of intraocular pressure (IOP). Studies have reported thinning of retinal nerve fiber layer (RNFL), alteration of optic nerve head, choroidal and macular thickness, and reduced VF sensitivity in patients of OSA with no history glaucoma. A negative correlation of apnea-hypopnea index with RNFL and VF indices has been described in some studies. Raised IOP was noted which is possibly related to obesity, supine position during sleep, and raised intracranial pressure. Diurnal fluctuations of IOP show more variations in OSA patients before and after continuous positive airway pressure (CPAP) therapy when compared with the normal cases. The vascular factors behind the pathogenesis include recurrent hypoxia with increased vascular resistance, oxidative stress damage to the optic nerve. In conclusion, comprehensive glaucoma evaluation should be recommended in patients with OSA and should also periodically monitor IOP during CPAP treatment which may trigger the progression of glaucomatous damage.

Can intraocular pressure asymmetry indicate undiagnosed primary glaucoma? The Chennai Glaucoma Study.

AIM: : To investigate the association of intraocular pressure (IOP) asymmetry with undiagnosed primary glaucoma in rural and urban populations of south India. METHODS: Chennai Glaucoma Study is a population-based cross-sectional study. The participants were adults, 40 years or older. The prevalence of primary glaucoma was defined using International Society of Geographical and Epidemiological Ophthalmology classification. IOP asymmetry was diagnosed when the difference in IOP between 2 eyes was >3 mm Hg. Analysis included only bilaterally phakic subjects. We excluded subjects with known glaucoma, secondary glaucoma, pseudoexfoliation, ocular trauma, and ocular surgery. RESULTS: Of 6310 subjects, 3052 (48.4%) were rural residents. The mean age was 52 (standard deviation: 9.5) years. The prevalence of IOP asymmetry increased steadily with increasing patient age. The prevalence of undiagnosed primary glaucoma was 3.4% (95% confidence interval, 2.9-3.8). Undiagnosed primary glaucoma was 3 times more common in subjects with IOP asymmetry than without (odds ratio 3.08, 95% confidence interval, 2.1-4.3). The specificity of IOP asymmetry in detecting undiagnosed primary glaucoma was 92%. CONCLUSIONS: IOP asymmetry of >3 mm Hg has limited accuracy for the detection of undiagnosed primary glaucoma. The criterion should be combined with other indicators of glaucoma to build the pretest probability of the disease.

Optic disc dimensions and cup-disc ratios among healthy South Indians: The Chennai Glaucoma Study.

PURPOSE: To present optic disc and cup dimensions, cup-disc ratios (CDRs) and asymmetry among healthy South Indians, and their associations with ocular and systemic variables. METHODS: A total of 623 healthy phakic participants of the Chennai Glaucoma Study underwent complete eye examinations including optic disc stereo-photography. Planimetry was performed under stereo-viewing conditions. The morphological type of cupping (no cups, steep cups, partly sloping and fully sloping cups) was identified based on a modification of the classification by Jonas et al.( 11 ) The associations of planimetric measures (optic disc area, cup area and vertical cup-disc ratio [VCDR]) with age, gender, height, intraocular pressure, refraction, astigmatism, axial length and corneal thickness as explanatory variables were examined. The associations of asymmetries in the above planimetric measures with age, gender and asymmetries of the above explanatory variables were examined. RESULTS: Mean optic disc and cup areas were 2.82 ± 0.52 mm(2) and 0.53 ± 0.39 mm(2). Mean CDR was 0.36 ± 0.18. Men had larger discs (P = 0.03). Cup area and VCDR revealed significant associations with disc area (P <0.0001) and type of cupping (P < 0.0001). Mean disc and cup area asymmetries were 0.19 ± 0.16 mm(2) and 0.15 ± 0.15 mm(2). Mean VCDR asymmetry was 0.07 ± 0.08 mm(2). Cup area and VCDR asymmetries showed significant associations with disc area asymmetry (P < 0.0001, both) and asymmetry in the presence or absence of physiological cupping, i.e. subjects with physiological cupping in one eye and no cupping in the other (P < 0.0001, both). CONCLUSIONS: We present normative optic disc, cup and VCDR measures and asymmetries among healthy South Indians. We demonstrated the dependence of VCDR on the morphological type of cupping.

Glaucoma in India: estimated burden of disease.

Over the last decade the prevalence of glaucoma has been reported by the Vellore Eye Survey, Andhra Pradesh Eye Disease Study, Aravind Comprehensive Eye Survey, Chennai Glaucoma Study, and West Bengal Glaucoma Study. There have been some differences largely because of methodologic variations. We use the reported age and gender stratified prevalence estimates from these studies and the Indian population census estimates to calculate the number of persons with glaucoma or at risk of the disease in the country. On the basis of the available data, we estimate that there are approximately 11.2 million persons aged 40 years and older with glaucoma in India. Primary open angle glaucoma is estimated to affect 6.48 million persons. The estimated number with primary angle-closure glaucoma is 2.54 million. Those with any form of primary angle-closure disease could comprise 27.6 million persons. Most of those with disease are undetected and there exist major challenges in detecting and treating those with disease. In the light of the existing manpower and resource constraints, we evaluate options for improving case detection rates in the country.

Outcomes of cataract surgery in a rural and urban south Indian population.

PURPOSE: To assess the visual outcome after cataract surgery in a south Indian population. MATERIALS AND METHODS: Population-based cross-sectional study of subjects aged 40 years or more. Three thousand nine hundred and twenty-four rural subjects from 27 contiguous villages and 3850 urban subjects from five randomly selected divisions were studied. All subjects underwent a comprehensive ophthalmic examination that included visual acuity, refraction, slit-lamp biomicroscopy, applanation tonometry, gonioscopy, and dilated retinal examination. STATISTICAL ANALYSIS: Chi square test, t test and multivariate analysis were used. RESULTS: Five hundred and twenty-eight (216 males, 312 females, 781 eyes) rural subjects (13.5%, 95% confidence interval (CI) 12.4% to 14.6%) and 406 (197 males, 209 females, 604 eyes) urban subjects (10.5%, 95% CI 9.6-11.5%) had undergone cataract surgery. Outcome of cataract surgery was defined based on visual acuity. Using best-corrected visual acuity for classification, the single most important cause for visual impairment was cystoid macular edema in the aphakic group and posterior capsule opacification in the pseudophakic group. Aphakia (visual acuity of < 20/60 to

Lower threshold estimates at the onset of automated perimetry causing artefacts in perimetrically naive subjects.

Reduction in the threshold value of the primary points resulting in depressed points on the pattern deviation plot of Humphrey visual fields was observed in a series of four perimetrically naive subjects. The defect disappeared on repeated testing. This primary point defect could be attributed to the patient's poor understanding of the test, response bias or poor instruction by the perimetrist.

Prevalence of retinitis pigmentosa in South Indian population aged above 40 years.

PURPOSE: The study was undertaken to evaluate the prevalence of retinitis pigmentosa (RP) in rural and urban South India. METHODS: Seven thousand seven hundred and seventy four subjects aged 40 years or more from rural and urban Tamil Nadu, underwent comprehensive ophthalmic examination out of 9576 enumerated (81.17%). After a thorough ophthalmic examination, fundus photographs were taken for documentation. Statistical analysis was done using SPSS for Windows (ver 14). RESULTS: 7461 (95.9%) subjects had fundus details seen in both eyes. Thirteen subjects (0.17%; 4 males, 9 females) were diagnosed as retinitis pigmentosa. Retinitis pigmentosa in the urban population was seen in approximately 1 in 930 persons, while 1 in 372 of rural subjects had the disorder. This figure is greater than other reports from the western populations and that of the conservative estimate of 1 in 4000. The age and gender adjusted prevalence rate of retinitis pigmentosa to national census 2001 was 0.155%. Eight subjects (61.53%) had visual acuity less than 3/60. CONCLUSION: Prevalence of RP in South India appears to be alarmingly higher in comparison to those seen in other parts of the world.

Neural rim characteristics of healthy South Indians: the Chennai Glaucoma Study.

PURPOSE: To report neural rim dimensions for South Indians and examine rim shape with relevance to clinical evaluation. METHODS: Healthy phakic participants (n = 623) of the Chennai Glaucoma Study with normal frequency-doubling perimetry underwent complete eye examinations including optic disc digital stereophotography. Planimetry was performed under stereoviewing conditions using custom software. Rim area, shape, and associations were examined. Rim area asymmetry was studied in a subgroup of 565 subjects. RESULTS: Mean neuroretinal rim area was 2.29 +/- 0.39 mm(2). Disc area (P < 0.001) and type of cupping (P < 0.001) were associated with rim area. Mean rim area asymmetry was 0.18 +/- 0.15 mm(2); 95% of subjects had asymmetry < 0.5 mm(2). Disc area asymmetry (0.359, P < 0.0001) and intraocular pressure (IOP) asymmetry (P = 0.004) were related to rim area asymmetry. On average, the inferior rim was thickest and the temporal was thinnest. Mean inferior by superior rim width was 1.18 +/- 0.17; 2.5 percentile, 0.9. Thirty-eight (7.1%) subjects had the superior rim thicker than the inferior rim, the occurrence of which was associated with disc torsion (P = 0.002) and male sex (P = 0.04). Of the clinically relevant rim width measures in glaucoma (i.e., inferior, superior, and temporal) the temporal rim was thinnest in 469 (87.8%) eyes. Horizontally oval disc shape (P < 0.0001), type of cupping (P = 0.006), and astigmatism (P = 0.001) were associated with the presence of thicker temporal than superior/inferior rims. CONCLUSIONS: The report provides hitherto unreported neural rim measurements among healthy South Indians. The ISNT rule (inferior rim thicker than superior rim, thicker than nasal rim, thicker than temporal rim) was violated in a significant minority. Physiological associations with such violations are described.