Surgical eye camp in rural area of Nepal and its role in Vision 2020

Blindness continues to remain a major public health problem in Nepal and cataract is the leading cause. Cataract surgical coverage is relatively low in the rural areas where prevalence of blindness is high. This is a descriptive cross sectional camp based study in a remote village of Nepal, where 4 days screening of the eye disease mainly the cataract was done. The aim of the study was to evaluate the role of surgical outreached eye camps in rural Nepal and its impact in Vision 2020. 250 patients (54.80% males and 45.20% females) underwent eye health screening tests. Cataract was the commonest ocular disease (29.6%) among the screened population and 24% (60 patients) of them required cataract surgery (57% male and 43% female). The mean age of the operated patient was 71.84 ± 10.6years. Among the operated cases, bilateral blindness was present in 21.66% and unilateral blindness in 70% but after vision restoring cataract surgery, normal visual acuity (6/6-6/18) was achieved in 31(51.66%), and vision of 6/24-6/60 in 23 (38.33%) cases. Cataract remains to be the major cause of blindness in Nepal and arrangement of repeated surgical eye camps in the remote areas of Nepal could aid in reducing the preventable cause of blindness thereby help in achieving the goal of Vision 2020

Profile of paediatric low vision population: a retrospective study from Nepal.

BACKGROUND: Childhood blindness and low vision have become major public health problems in developing countries. The purpose of this study was to categorise the causes of visual impairment according to aetiology and provide detailed local information on visually impaired children seeking low-vision services in a tertiary eye centre in Nepal. METHODS: A retrospective study was conducted of all visually impaired children (visual acuity of less than 6/18 in the better eye), aged less than 17 years seen in the low-vision clinic at the Sagarmatha Chaudhary Eye Hospital in Lahan between January 1, 2012 and December 31, 2013. RESULTS: Of the 558 visually impaired children, the majority were males, 356 (63.7 per cent). More than half (56.5 per cent) of the children were in the 11 to 16 years age group. Many of the low-vision children (52.9 per cent) were identified as having moderate visual impairment (visual acuity less than 6/18 to 6/60). Most children were diagnosed with childhood (36.2 per cent) or genetic (35.5 per cent) aetiology, followed by prenatal (22.2 per cent) and perinatal (6.1 per cent) aetiologies. Refractive error and amblyopia (20.1 per cent), retinitis pigmentosa (14.9 per cent) and macular dystrophy (13.4 per cent) were the most common causes of paediatric visual impairment. Nystagmus (50.0 per cent) was the most common cause of low vision in the one to five years age group, whereas refractive error and amblyopia were the major causes in the six to 10 and 11 to 16 years age group (17.6 and 22.9 per cent, respectively). Many of the children (86.0 per cent) were prescribed low-vision aids and 72.0 per cent of the low-vision aid users showed an improvement in visual acuity either at distance or near. CONCLUSION: Paediatric low vision has a negative impact on the quality of life in children. Data from this study indicate that knowledge about the local characteristics and aetiological categorisation of the causes of low vision are essential in tackling paediatric visual impairment. The findings also signify the importance of early intervention to ensure a better quality of life

Comparison of retinal nerve fiber layer and macular thickness for discriminating primary open-angle glaucoma and normal-tension glaucoma using optical coherence tomography

Purpose The aim of this study was to evaluate the discrimination capabilities of macular and peripapillary retinal nerve fiber layer (pRNFL) thickness parameters as measured using spectral domain optical coherence tomography (SD-OCT) between primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG). Methods A total of 90 subjects were enrolled: 30 healthy subjects, 30 subjects with POAG and 30 subjects with NTG, consecutively. Retinal nerve fiber layer thickness, macular thickness and volume measurements were obtained with circular and radial SD-OCT scans. All parameters were compared between groups using an analysis of variance test. Areas under receiver-operating characteristic (AROC) curves with sensitivities at specificities greater than or equal to 90 per cent were generated to compare discrimination capabilities of various parameters between POAG and NTG. Results Macular thickness and volume measurements were the highest in normal subjects, followed by NTG and POAG (p < 0.05). Average retinal nerve fiber layer thickness had perfect discrimination for normal-POAG (AROC: 1.000; sensitivity: 100 per cent) and near perfect discrimination for normal-NTG (AROC: 0.979; sensitivity: 93 per cent) as well as NTG-POAG pairs (AROC: 0.900; sensitivity: 60 per cent). Inferior outer macular thickness (IOMT) and total volume were the best macular thickness and volume parameters having similar AROCs and sensitivities between normal and POAG (IOMT, AROC: 0.987; sensitivity: 92 per cent and total volume, AROC: 0.997; sensitivity: 97 per cent), normal and NTG (IOMT, AROC: 0.862, sensitivity: 47 per cent and total volume, AROC: 0.898, sensitivity: 67 per cent) and also between NTG and POAG (IOMT, AROC: 0.910, sensitivity: 53 per cent and total volume, AROC: 0.922, sensitivity: 77 per cent). In each comparison group, there was no statistically significant difference in AROCs between average retinal nerve fiber layer and inferior outer macular thickness, as well as total volume. Conclusions The macular parameters offer comparable performance to pRNFL parameters for the discrimination of NTG and POAG. Average retinal nerve fiber layer thickness, total macular volume and inferior outer macular thickness were the best SD-OCT parameters with superior discriminating capabilities

Flash VEP in Clinically Stable Pre-Term and Full-Term Infants

Purpose Pre-term infants are at risk of abnormal visual development that can range from subtle to severe. The aim of this study was to compare flash VEPs in clinically stable pre-term and full-term infants at 6 months of age. Methods Twenty-five pre-term and 25 full-term infants underwent flash VEP testing at the age of 6 months. Monocular VEPs were recorded using flash goggles on a RETIscan system under normal sleeping conditions. Amplitude and peak time responses of the P2 component in the two eyes were averaged and compared between the two groups. Multiple regression analyses were performed to assess the relationship of the P2 responses with birth weight (BW) and gestational age (GA). Results At 6 months corrected age, pre-term infants had significantly delayed P2 peak times than full-term infants (mean difference: 10.88 [95% CI 4.00–17.76] ms, p = 0.005). Pre-term infants also showed significantly reduced P2 amplitudes as compared to full-term infants (mean difference: 2.36 [0.83–3.89] µV, p = 0.003). Although the regression model with GA and BW as fixed factors explained 20% of the variance in the P2 peak time (F2,47 = 5.98, p = .0045), only GA showed a significant negative relationship (β = −2.66, p = .003). Neither GA (β = 0.21, p = .28) nor BW (β = 0.001, p = .32) showed any relationship with P2 amplitude. Conclusions Our results demonstrate that, compared with full-term infants, clinically stable pre-term infants exhibit abnormal flash VEPs, with a delay in P2 peak time and a reduction in P2 amplitude. These findings support a potential dysfunction of the visual pathway in clinically stable pre-term infants as compared to full-term infants

Exploring Transfer Learning in Medical Image Segmentation using Vision-Language Models

Medical Image Segmentation is crucial in various clinical applications within the medical domain. While state-of-the-art segmentation models have proven effective, integrating textual guidance to enhance visual features for this task remains an area with limited progress. Existing segmentation models that utilize textual guidance are primarily trained on open-domain images, raising concerns about their direct applicability in the medical domain without manual intervention or fine-tuning. To address these challenges, we propose using multimodal vision-language models for capturing semantic information from image descriptions and images, enabling the segmentation of diverse medical images. This study comprehensively evaluates existing vision language models across multiple datasets to assess their transferability from the open domain to the medical field. Furthermore, we introduce variations of image descriptions for previously unseen images in the dataset, revealing notable variations in model performance based on the generated prompts. Our findings highlight the distribution shift between the open-domain images and the medical domain and show that the segmentation models trained on open-domain images are not directly transferrable to the medical field. But their performance can be increased by finetuning them in the medical datasets. We report the zero-shot and finetuned segmentation performance of 4 Vision Language Models (VLMs) on 11 medical datasets using 9 types of prompts derived from 14 attributes.Comment: 25 pages, 9 figure

Deep-learning assisted detection and quantification of (oo)cysts of Giardia and Cryptosporidium on smartphone microscopy images

The consumption of microbial-contaminated food and water is responsible for the deaths of millions of people annually. Smartphone-based microscopy systems are portable, low-cost, and more accessible alternatives for the detection of Giardia and Cryptosporidium than traditional brightfield microscopes. However, the images from smartphone microscopes are noisier and require manual cyst identification by trained technicians, usually unavailable in resource-limited settings. Automatic detection of (oo)cysts using deep-learning-based object detection could offer a solution for this limitation. We evaluate the performance of three state-of-the-art object detectors to detect (oo)cysts of Giardia and Cryptosporidium on a custom dataset that includes both smartphone and brightfield microscopic images from vegetable samples. Faster RCNN, RetinaNet, and you only look once (YOLOv8s) deep-learning models were employed to explore their efficacy and limitations. Our results show that while the deep-learning models perform better with the brightfield microscopy image dataset than the smartphone microscopy image dataset, the smartphone microscopy predictions are still comparable to the prediction performance of non-experts.Comment: 18 pages (including supplementary information), 4 figures, 7 tables, submitting to Journal of Machine Learning for Biomedical Imagin

Refractive Status in Nepalese Pre-Term and Full-Term Infants Early in Life.

SIGNIFICANCE: This study suggests that pre-term infants, even without retinopathy of prematurity, are at risk for abnormal refractive development and informs the need for close monitoring of refractive error in such infants, regardless of their retinopathy of prematurity status. PURPOSE: The present study aims to investigate the refractive error trend in Nepalese pre-term infants without retinopathy of prematurity (ROP) in the first 6 months of life and explore the association of refractive error with birth weight (BW) and gestational age (GA). METHODS: Thirty-six pre-term infants without ROP and 40 full-term infants underwent cycloplegic retinoscopy at birth, term (for pre-term only), 3 months, and 6 months chronologically. Refractive status was classified into emmetropia (mean spherical equivalent refraction [SER] 0 to +3.00D), myopia (SER +3.00D). Refractive parameters at various age points were compared between the pre-term and full-term infants using general linear model repeated measures ANOVA. RESULTS: At birth, the SER in the pre-term infants was +0.84 ± 1.72D; however, there was a shift toward myopia at 6 months of age (SER = -0.33 ± 1.95D). There was a significant difference in SER, astigmatism, and anisometropia between pre-term and full-term infants by 6 months of age (P < .01). Astigmatism and anisometropia showed an increasing trend with age in pre-term infants (P < .05 at 6 months) in contrast to a decreasing trend in full-term infants (P < 0.05 at 3 and 6 months). In pre-term infants, there was a statistically significant positive relationship between GA and SER (β = 0.32, R = 17.6%, P < .05) but a negative relationship between BW and astigmatism (β = -1.25, R = 20.6%, P < .01). CONCLUSIONS: Pre-term infants who do not develop ROP show a trend toward increasing myopia and demonstrate greater astigmatism and anisometropia than full-term infants in their first 6 months of life

Visual deficits in Nepalese patients with oculocutaneous albinism

Background: Albinism poses a significant threat to visual functions and causes remarkable ocular morbidity often resulting in visual disabilities. The study aimed at describing the visual status in patients with diagnosed cases of complete oculocutaneous albinism (OCA) attending to a tertiary eye hospital in Nepal. Methods: This was a cross-sectional descriptive hospital-based study of all diagnosed oculocutaneous albinotic cases (16 males and 9 females; mean age of 16 years) who visited the Department of Ophthalmology at the Institute of Medicine, for ocular consultation between September 1, 2011 and December 1, 2013. Results: Twenty-five cases (50 eyes) with OCA were enrolled in the study. All the participants had maximally reduced visual acuity (mean: 1.24 ± 0.50 logMAR). Myopic astigmatism was the most common refractive error (n = 17; 34%). 58% of all participants had with-the-rule astigmatism. Considering the spherical equivalent power, most of the eyes (n = 30; 60%) had myopia, with overall mean SE refractive error of −1.59 ± 5.39 D. Visual acuity improved significantly with refractive correction in place (paired sample t-test, p < 0.05). Horizontal pendular nystagmus was the most common nystagmus (n = 34 eyes; 68%). Alternating esotropia and alternating exotropia each were observed in 16% of participants who had strabismus (40% of all cases). The diaphanous iris, foveal hypoplasia and poliosis were the most consistent clinical features. Conclusion: Patients with OCA present with a broad spectrum of visual deficits that impair the visual functions. Significant improvement in visual acuity following optical correction serves as an impetus to the reduction of visual disabilities in individuals with albinism

Intraeye retinal nerve fiber layer and macular thickness asymmetry measurements for the discrimination of primary open-angle glaucoma and normal tension glaucoma

Purpose: The aim of this study was to evaluate the diagnostic capability of intraeye retinal nerve fiber layer (RNFL) thickness and macular thickness (MT) asymmetry measurements for the discrimination of normal tension glaucoma (NTG) and primary open-angle glaucoma (POAG) using spectral domain optical coherence tomography (SD-OCT). Methods: A total of 90 subjects were enrolled including 30 consecutive healthy subjects, 30 consecutive subjects with POAG, and 30 consecutive subjects with NTG. RNFL thicknesses around the optic disc as well as MT measurements were taken with circular and radial SD-OCT scans. Intraeye retinal and MT asymmetry were calculated as the absolute difference between superior and inferior hemispheres of the eye using posterior pole asymmetry analysis protocol. Analysis of variance was used for comparison and areas under the receiver operating characteristic (AROC) were obtained for different parameters among the three diagnostic groups. Results: There was a significant difference in MT asymmetry for all comparison groups (normal-NTG, p < 0.05; normal-POAG, p < 0.001; and NTG-POAG, p < 0.001). Intraeye retinal nerve fiber thickness asymmetry measurements were not different between the groups (normal-NTG, p < 0.187; normal-POAG, p < 0.056; and NTG-POAG, p < 0.837). The area under ROC curves exceeded 0.800 for all the studied parameters, including the MT asymmetry except for intraeye RNFL thickness asymmetry which had the lowest AROC as well as the least sensitivity for identifying subjects with NTG from normal (AROC = 0.626, sensitivity = 30%); POAG from normal (AROC = 0.644, sensitivity = 37%) and NTG from POAG (AROC = 0.533, sensitivity = 13%). Conclusion: The intraeye MT asymmetry holds significant potential as a distinguishing parameter for NTG and POAG