Retinal nerve fiber layer thickness in amblyopia

Purpose: To report retinal nerve fiber layer thickness (RNFLT) in eyes with amblyopia compared with contralateral healthy eyes. Methods: In this cross-sectional study, we included patients with anisometropic amblyopia, strabismic amblyopia, and mixed amblyopia. All subjects underwent complete ophthalmic examination, including RNFLT measurement with time-domain OCT (Stratus OCT) and scanning laser polarimeter (GDX VCC). A paired “t” test was used to compare average and quadrant-wise RNFL thickness between the amblyopic and contralateral normal eyes. In addition, an analysis of variance test was used to compare various RNFL thickness parameters between the three groups. Results: A total of 33 eyes of 33 subjects with anisometropic amblyopia, 20 eyes of 20 subjects with strabismic amblyopia, and 38 eyes of 38 subjects with mixed amblyopia were included. In the anisometropic amblyopia group, the average RNFLT in the amblyopic eye was 98.2 ?m and 99.8 ?m in the fellow normal eye (P = 0.5), the total foveal thickness was 152.82 ?m (26.78) in the anisometropic eye and 150.42 ?m (23.84) in the fellow eye (P = 0.38). The difference between amblyopic and contralateral normal eye for RNFL and macular parameters was statistically insignificant in all three groups. The RNFL thickness in four quadrants was similar in the amblyopic and non-amblyopic eye between all three groups and statistically non-significant. Conclusion: Our study showed that RNFL thickness was similar in amblyopic and non-amblyopic eyes between all three amblyopia groups

Assessment of peripapillary retinal nerve fiber layer thickness using scanning laser polarimetry (GDx VCC) in normal Indian children.

Purpose: To obtain reference values of RNFL thickness in normal Indian children and to study the association of RNFL thickness with central corneal thickness(CCT) and axial length(AL). Materials and Methods: 200 normal Indian children (mean age 8.6 ± 2.9 yrs) were examined on the GDxVCC. The inferior average (IA), superior average (SA), temporal-superior-nasal-inferior-temporal (TSNIT) average and nerve fiber index (NFI) values were recorded and compared between males and females as well as between the different age groups. The association of TSNIT average with AL and CCT was examined. Results: Values for the RNFL parameters were-SA: 64.9 ± 9.7, IA: 63.8 ± 8.8, TSNIT average: 53.5 ± 7.7 and NFI 21.5 ± 10.8. Superior, inferior and TSNIT averages did not differ significantly between males and females (P = 0.25, P = 0.19, P = 0.06 respectively; Mann-Whitney U test). No significant differences were found in TSNIT average across age groups. There was a statistically significant positive correlation between CCT and TSNIT average (r = 0.25, r2 = 0.06, P < 0.001). The correlation TSNIT average and AL(r = −0.12; r2= 0.01) was not significant (P = 0.2). Conclusion: Reference values for RNFL parameters reported for Indian children are similar those reported in adults. There is a small correlation between central corneal thickness and RNFL as reflected in average TSNIT.

Is the observed lowering of intraocular pressure due to treatment.

Objective: Use Bayes' theorem to estimate the intraocular pressure (IOP) lowering effect of medical treatment initiated for glaucoma and determine if IOP comparisons to the baseline IOP of the same eye is clinically useful. Materials and Methods: The probability that treatment with prostaglandin is responsible for an observed 20% decrease in IOP with prostaglandin treatment was calculated using Bayes' theorem using the following available information: the probability of a 20% decrease in IOP given treatment with prostaglandin, the probability of a treatment effect using prostaglandin and the overall probability of a 20% decrease in IOP. The calculations were repeated to account for a possible 2 mmHg overestimation of effect caused by measurement error in performing applanation tonometry. Results: The probability that treatment is responsible for an observed 20% decrease in IOP following initiation of treatment with a prostaglandin was 99%. After adjusting for measurement error this probability was 98%. Obtaining two IOP measurements marginally increased the probability. Conclusion: Following initiation of treatment with prostaglandin, Bayes' theorem allows us to infer that treatment effect is the most likely explanation for an observed 20% decrease in IOP from the baseline; this inference remains even after adjusting for known measurement error. The high probability of a treatment effect is due to the high prior odds of treatment effect and the high likelihood ratio for prostaglandin producing such an effect. If data is available, similar calculations can be used for other percentage decreases, other medications and for the monocular trial.

Glaucoma in developing countries.

Objective: To describe the background and strategy required for the prevention of blindness from glaucoma in developing countries. Materials and Methods: Extrapolation of existing data and experience in eye care delivery and teaching models in an unequally developed country (India) are used to make recommendations. Results: Parameters like population attributable risk percentage indicate that glaucoma is a public health problem but lack of simple diagnostic techniques and therapeutic interventions are barriers to any effective plan. Case detection rather than population-based screening is the recommended strategy for detection. Population awareness of the disease is low and most patients attending eye clinics do not receive a routine comprehensive eye examination that is required to detect glaucoma (and other potentially blinding eye diseases). Such a routine is not taught or practiced by the majority of training institutions either. Angle closure can be detected clinically and relatively simple interventions (including well performed cataract surgery) can prevent blindness from this condition. The strategy for open angle glaucoma should focus on those with established functional loss. Outcomes of this proposed strategy are not yet available. Conclusions: Glaucoma cannot be managed in isolation. The objective should be to detect and manage all potential causes of blindness and prevention of blindness from glaucoma should be integrated into existing programs. The original pyramidal model of eye care delivery incorporates this principle and provides an initial starting point. The routine of comprehensive eye examination in every clinic and its teaching (and use) in residency programs is mandatory for the detection and management of potentially preventable blinding pathology from any cause, including glaucoma. Programs for detection of glaucoma should not be initiated unless adequate facilities for diagnosis and surgical intervention are in place and their monitoring requires reporting of functional outcomes rather than number of operations performed.

Unusual presentation in Axenfeld-Rieger syndrome.

We report an unusual presentation of a case of Axenfeld-Rieger (A-R) syndrome. A 14-year-old male presented with gradual dimness of vision for 1 year and redness of left eye for 3 days. The patient had megalocornea with Haab's striae in the right eye and posterior embryotoxon in both the eyes. In the left eye, there was a white cord-like structure traversing the anterior chamber with adhesions to iris tissue along its course. On two antiglaucoma medications, his intraocular pressure (IOP) was 22 mm Hg in the right eye and 18 mm Hg in the left eye. Gonioscopy revealed a cord-like structure originating at the level of Schwalbe's line. He underwent right eye trabeculectomy with mitomycin-C. This case highlights a rare presentation of a strange cord-like structure, a rare presentation of A-R syndrome.

Evaluation of a glaucoma patient.

The diagnosis of glaucoma is usually made clinically and requires a comprehensive eye examination, including slit lamp, applanation tonometry, gonioscopy and dilated stereoscopic evaluation of the optic disc and retina. Automated perimetry is obtained if glaucoma is suspected. This establishes the presence of functional damage and provides a baseline for follow-up. Imaging techniques are not essential for the diagnosis but may have a role to play in the follow-up. We recommend a comprehensive eye examination for every clinic patient with the objective of detecting all potentially sight-threatening diseases, including glaucoma.

Correlation between ocular parameters and amplitude of accommodation.

Aim: To study the relationship between ocular parameters and amplitude of accommodation (AA) in the peri-presbyopic age group (35–50 years). Materials and Methods: Three hundred and sixteen right eyes of consecutive patients in the age group 35–50 years, who attended our outpatient clinic, were studied. Emmetropes, hypermetropes and myopes with best-corrected visual acuity of 20/20, J1 in both eyes were included. The AA was calculated by measuring the near point of accommodation. The axial length (AL), central anterior chamber depth (CACD) and lens thickness (LT) were also measured. Results: There was moderate correlation (Pearson’s correlation coefficient r = 0.56) between AL and AA as well as between CACD and AA (r = 0.53) in myopes in the age group 35–39 years. In the other age groups and the groups taken as a whole, there was no correlation. In hypermetropes and emmetropes, there was no correlation between AA and the above ocular parameters. No significant correlation existed between LT and AA across different age groups and refractive errors. Conclusion: There was no significant correlation between AA and ocular parameters like anterior chamber depth, AL and LT.

Evaluation of Ahmed glaucoma valve implantation through a needle-generated scleral tunnel in Mexican children with glaucoma.

Purpose: To evaluate the results and extrusion rates of the Ahmed glaucoma valve (AGV) implantation through a needle-generated scleral tunnel, without a tube-covering patch, in children. Materials and Methods: A retrospective review of the charts of 106 Mexican children implanted with 128 AGVs operated between 1994 and 2002, with the needle track technique, at our institution, with at least six months follow up was done. Main outcome measures were intraocular pressure (IOP) control, tube extrusions or exposure and other complications. Results: Kaplan-Meier analysis demonstrated a 96.9% survival rate at six months, 82.4% at one year, 78.7% at two years, 70% at three years and 41.6% at four years. Total success at the last follow-up (IOP between 6 and 21 mm Hg without medications) was achieved in 30 eyes (23.5%), 58 eyes (45.3%) had qualified success (only topical hypotensive drugs) and 40 eyes (31.3%) were failures. The mean pre- and post-operative IOP at the last follow up was 28.4 mmHg (SD 9.3) and 14.5 mmHg (SD 6.3), respectively. No tube extrusions or exposures were observed. Tube-related complications included five retractions, a lens touch and a transitory endothelial touch. The risk of failure increased if the eye had any complication or previous glaucoma surgeries. Conclusion: Medium-term IOP control in Mexican children with glaucoma can be achieved with AGV implantation using a needle-generated tunnel, without constructing a scleral flap or using a patch to cover the tube. There were no tube extrusions, nor any tube exposures with this technique.

Impact of a month-long training program on the clinical skills of ophthalmology residents and practitioners.

A cohort study was performed to assess the impact of an intensive, hands-on, supervised training program in ophthalmic clinical evaluation, for ophthalmology residents and private practitioners. All students underwent one-month training in comprehensive ophthalmology examination and investigations at a tertiary care center between January 2004 and January 2006. The training methodology included didactic lectures, video-demonstrations and hands-on training. The participants completed a self-assessment with a set of 23 questions designed to assess the level of confidence in various skills on the first and last day of the training. Of a total of 118 students, 67 (56.8%) were residents and 51 (43.2%) were practitioners. The mean score pre-training was 38.3 out of 92 (S.D. ±16.9), and was 70.6 out of 92 (S.D.± 10.1) post-training. The mean increase in the scores was 32.3 (P value < 0.001). We concluded that intensive, short-term training programs could improve the self-perceived level of confidence of ophthalmology residents and practitioners.

Aniridia associated with congenital aphakia and secondary glaucoma.

We report a case of aniridia associated with congenital aphakia and secondary glaucoma. A 35-year-old male presented with aniridia, congenital aphakia and secondary glaucoma in both eyes. After an unsuccessful medical management, he underwent trabeculectomy with mitomycin C and anterior vitrectomy under local anesthesia in his left eye. Postoperatively, at the end of six months, intraocular pressure (IOP) in his left eye was controlled without medications. This case highlights the rare association of aniridia with congenital aphakia and secondary glaucoma.

Likelihood ratios: Clinical application in day-to-day practice.

In this article we provide an introduction to the use of likelihood ratios in clinical ophthalmology. Likelihood ratios permit the best use of clinical test results to establish diagnoses for the individual patient. Examples and step-by-step calculations demonstrate the estimation of pretest probability, pretest odds, and calculation of posttest odds and posttest probability using likelihood ratios. The benefits and limitations of this approach are discussed.

Practical approach to medical management of glaucoma.

Primary open angle glaucoma (POAG) is usually a chronic, slowly progressive disease. At present, all resources are directed towards reduction of intraocular pressure (IOP), the only known causal and treatable risk factor for glaucoma, and medical management is frequently the first choice in most cases. With the introduction of innovative tools for early diagnosis and newer medications for treatment, decision-making in diagnosis and treatment of glaucoma has become more complex. The philosophy of glaucoma management is to preserve the visual function and quality of life (QOL) of the individual with minimum effects on QOL in terms of cost, side effects, treatment regime, follow-up schedules as well as socioeconomic burden. Our aim should be not to treat just the IOP, optic disc or visual field, but to treat the patient as a whole so as to provide maximum benefit with minimal side effects. In this article, we describe the scientific approach to medical management, mainly of POAG.

Learning micro incision surgery without the learning curve.

We describe a method of learning micro incision cataract surgery painlessly with the minimum of learning curves. A large-bore or standard anterior chamber maintainer (ACM) facilitates learning without change of machine or preferred surgical technique. Experience with the use of an ACM during phacoemulsification is desirable.

An evaluation of medical college departments of ophthalmology in India and change following provision of modern instrumentation and training.

AIM: To evaluate teaching and practice in medical college ophthalmology departments in a representative Indian state and changes following provision of modern instrumentation and training. STUDY TYPE: Prospective qualitative study. MATERIALS AND METHODS: Teaching and practice in all medical colleges in the state assessed on two separate occasions by external evaluators. Preferred criteria for training and care were pre-specified. Methodology included site visits to document functioning and conduct interviews. Assessments included resident teaching, use of instrumentation provided specifically for training and standard of eye care. The first evaluation (1998) was followed by provision of modern instrumentation and training on two separate occasions, estimated at Rupees 34 crores. The follow-up evaluation in 2006 used the same methodology as the first. RESULTS: Eight departments were evaluated on the first occasion; there were 11 at the second. On the first assessment, none of the programs met the criteria for training or care. Following the provision of modern instrumentation and training, intraocular lens usage increased dramatically; but the overall situation remained essentially unchanged in the 8 departments evaluated 8 years later. Routine comprehensive eye examination was neither taught nor practiced. Individually supervised surgical training using beam splitters was not practiced in any program; neither was modern management of complications or its teaching. Phacoemulsification was not taught, and residents were not confident of setting up practice. Instruments provided specifically for training were not used for that purpose. Students reported that theoretical teaching was good. CONCLUSIONS: Drastic changes in training, patient care and accountability are needed in most medical college ophthalmology departments.

Understanding and using sensitivity, specificity and predictive values.

In this article, we have discussed the basic knowledge to calculate sensitivity, specificity, positive predictive value and negative predictive value. We have discussed the advantage and limitations of these measures and have provided how we should use these measures in our day-to-day clinical practice. We also have illustrated how to calculate sensitivity and specificity while combining two tests and how to use these results for our patients in day-to-day practice.

Barriers to accessing eye care services among visually impaired populations in rural Andhra Pradesh, South India.

PURPOSE: To understand the reasons why people in rural south India with visual impairment arising from various ocular diseases do not seek eye care. MATERIALS AND METHODS: A total of 5,573 persons above the age of 15 were interviewed and examined in the South Indian state of Andhra Pradesh covering the districts of Adilabad, West Godavari and Mahaboobnagar. A pre-tested structured questionnaire on barriers to eye care was administered by trained field investigators. RESULTS: Of the eligible subjects, 1234 (22.1%, N=5573)) presented with distant visual acuity < 20/60 or equivalent visual field loss in the better eye. Of these, 898 (72.7%, N=1234) subjects had not sought treatment despite noticing a decrease in vision citing personal, economic and social reasons. The analysis also showed that the odds of seeking treatment was significantly higher for literates [odds ratio (OR) 1.91, 95% confidence interval (CI) 1.38 to 2.65], for those who would be defined as blind by visual acuity category (OR 1.35, 95% CI 0.96 to 1.90) and for those with cataract and other causes of visual impairment (OR 1.50, 95% CI 1.11 to 2.03). Barriers to seeking treatment among those who had not sought treatment despite noticing a decrease in vision over the past five years were personal in 52% of the respondents, economic in 37% and social in 21%. CONCLUSION: Routine planning for eye care services in rural areas of India must address the barriers to eye care perceived by communities to increase the utilization of services.