Association of Body Surface Area Versus Body Mass Index on Outcomes in Peripheral Arterial Disease.

OBJECTIVE: Numerous studies have indicated that increased obesity in patients with established peripheral artery disease (PAD) is inversely associated with disease prognosis, a phenomenon coined as the "obesity paradox". A major cause of criticism in studies investigating the obesity paradox is the use of body mass index (BMI) as a surrogate marker in defining and quantifying the degree or severity of obesity. We conducted a retrospective review to verify whether the obesity paradox persists in patients with PAD when using body surface area (BSA) as an alternative anthropometric measure. METHODS: Patients undergoing surgery (open or endovascular) for PAD between January 2009 and March 2020 were identified from the Vascular Quality Initiative (VQI) national database. The association between BSA/BMI and risk of post-operative complications was evaluated using logistic regression and restricted cubic spline analysis, both of which adjusted for demographic and comorbid risk predictors. When analyzing BSA and BMI as categorical variables, patients were grouped according to BSA quintiles and the World Health Organization (WHO) BMI categories. RESULTS: A total of 130,428 patients were included based on our eligibility criteria, of which 85,394 (65.5%) were men. Patients were typically hypertensive (87.8%), diabetic (50.4%), and overweight (63.0% over 25 kg/m2). Patients with a high BMI or BSA typically presented at a younger age and with greater pre-operative administration of drugs (statin, ACE-inhibitor, anticoagulant, and beta blocker). Our results indicate that BSA and BMI are inversely associated with post-operative risk of all-cause morbidity, mortality, and cardiac complications. This finding was displayed when analyzing BMI/BSA as a continuous variable, or when indexing patients into BMI/BSA groups. CONCLUSION: Our data suggests that the obesity paradox persists in patients with PAD when using either BMI or BSA as anthropometric measures. Future studies with a prospective design and utilizing newer anthropometric indices should be conducted to fully verify the presence of this phenomenon.

Misidentification of the True Aortic Annulus With 2-dimensional Echocardiography: A Critical Appraisal Using 3-Dimensional Imaging.

OBJECTIVES: This study aimed to evaluate the accuracy of identifying the true aortic valve (AV) annulus using 2-dimensional (2D) echocardiography, with the goal of highlighting potential misidentification issues in clinical practice. DESIGN: An observational study employing 3-dimensional (3D) datasets to generate 2D images of the AV annulus for analysis. SETTING: The study was conducted in an academic medical center. PARTICIPANTS: Three-dimensional transesophageal echocardiography datasets were obtained from 11 patients with normal AV and aortic root anatomies undergoing coronary artery bypass surgery. Attending anesthesiologists certified by the National Board of Echocardiography (NBE) were approached subsequently to participate in this study. INTERVENTIONS: Two images per patient were generated from 3D datasets, reflecting the mid-esophageal long-axis view of the AV, a true AV annulus image, and an off-axis image. A survey was distributed to NBE-certified perioperative echocardiographers across 12 academic institutions to identify the true AV annulus from these images. MEASUREMENTS AND MAIN RESULTS: The survey, completed by 45 qualified respondents, revealed a significant misidentification rate of the true AV annulus, with only 36.8% of responses correctly identifying it. The rate of correct identification varied across image sets, with 44.4% of participants unable to correctly identify any true AV annulus image. CONCLUSIONS: The study highlighted the limitations of 2D echocardiography in accurately identifying the true AV annulus in complex 3D structures like the aortic root. The findings suggest a need for greater reliance on advanced imaging modalities, such as 3D echocardiography, to improve accuracy in clinical practice.

Advancing Precision in 3D Echocardiography: Incorporating 3D Markers to Aid Spatial Orientation.

The incorporation of 3D imaging into diagnostic and interventional echocardiography has rapidly expanded in recent years. Applications such as multiplanar reconstruction that were once considered research tools and required off-cart analysis can now readily be performed at the point of image acquisition and in real-time during live image acquisition for procedural guidance. While the application and quality of 3D images have significantly improved in recent years, there remains a noticeable lag in the evolution of artificial intelligence that would further simplify the interpretative processes, both during live sessions and offline analyses. Users are still required to mentally reconstruct sliced images during multiplanar reconstruction based on color-coded planes. While this may be an effortless task for the seasoned echocardiographer, it can be a challenging task for echocardiographers who are less familiar with 3D imaging and multiplanar reconstruction. This article describes the utility of using 3D markers to aid in image interpretation.

Artificial Intelligence for Anesthesiology Board-Style Examination Questions: Role of Large Language Models.

New artificial intelligence tools have been developed that have implications for medical usage. Large language models (LLMs), such as the widely used ChatGPT developed by OpenAI, have not been explored in the context of anesthesiology education. Understanding the reliability of various publicly available LLMs for medical specialties could offer insight into their understanding of the physiology, pharmacology, and practical applications of anesthesiology. An exploratory prospective review was conducted using 3 commercially available LLMs--OpenAI's ChatGPT GPT-3.5 version (GPT-3.5), OpenAI's ChatGPT GPT-4 (GPT-4), and Google's Bard--on questions from a widely used anesthesia board examination review book. Of the 884 eligible questions, the overall correct answer rates were 47.9% for GPT-3.5, 69.4% for GPT-4, and 45.2% for Bard. GPT-4 exhibited significantly higher performance than both GPT-3.5 and Bard (p = 0.001 and p < 0.001, respectively). None of the LLMs met the criteria required to secure American Board of Anesthesiology certification, according to the 70% passing score approximation. GPT-4 significantly outperformed GPT-3.5 and Bard in terms of overall performance, but lacked consistency in providing explanations that aligned with scientific and medical consensus. Although GPT-4 shows promise, current LLMs are not sufficiently advanced to answer anesthesiology board examination questions with passing success. Further iterations and domain-specific training may enhance their utility in medical education.

Virtual Reality Training for Central Venous Catheter Placement: An Interventional Feasibility Study Incorporating Virtual Reality Into a Standard Training Curriculum of Novice Trainees.

OBJECTIVES: This study assess the feasibility of integrating virtual reality (VR) simulation into the central venous catheter (CVC) placement training curriculum. DESIGN: The study consists of 3 parts: (1) Evaluating current manikin-based training for CVC placement through surveys for senior first-year anesthesia residents and cardiac anesthesia faculty who supervise resident performing the procedure; (2) Interventional study training novice trainees with VR simulator and assessing their reaction satisfaction; and (3) pilot study integrating VR training sessions into CVC training curriculum for first-year anesthesia residents. SETTING: Conducted at a single academic-affiliated medical center from December 2022 to August 2023. PARTICIPANTS: Junior first-year anesthesia residents. INTERVENTIONS: VR training sessions for CVC placements using the Vantari VR system. MEASUREMENTS AND MAIN RESULTS: Primary outcome: novice trainees' satisfaction with VR training for CVC procedure. Satisfaction of resident and faculty with standard manikin-based training was also collected. Faculty expressed concerns about residents' confidence and perceived knowledge in performing CVC placement independently. Novice trainees showed high satisfaction and perceived usefulness with VR training, particularly in understanding procedural steps and developing spatial awareness. Pilot integration of VR training into the curriculum demonstrated comparable training times and emphasized structured stepwise training modules to ensure completion of vital procedural steps. CONCLUSIONS: This study underscores the potential of VR simulation as a complementary training tool for CVC placement rather than a substitution of standard manikin training. VR is offering immersive experiences and addressing limitations of traditional manikin-based training methods. The integration of VR into training curricula warrants further exploration to optimize procedural proficiency and patient safety in clinical practice.

Synergistic Effect of Nilavembu Choornam-Gold Nanoparticles on Antibiotic-Resistant Bacterial Susceptibility and Contact Lens Contamination-Associated Infectious Pathogenicity.

Antibiotic-resistant bacterial colonies mitigate rapid biofilm formation and have complex cell wall fabrications, making it challenging to penetrate drugs across their biofilm barriers. The objective of this study was to investigate the antibacterial susceptibility of antibiotic-resistant bacteria and contact lens barrenness. Nilavembu Choornam-Gold Nanoparticles (NC-GNPs) were synthesized using NC polyherbal extract and characterized by UV-visible spectrophotometer, SEM-EDX, XRD, Zeta sizer, FTIR, and TEM analysis. Contact lenses with overnight cultures of antibiotic-resistant bacteria K. pneumoniae and S. aureus showed significant differences in growth, biofilm formation, and infection pathogenicity. The NC-GNPs were observed in terms of size (average size is 57.6 nm) and surface chemistry. A zone of inhibition was calculated for K. pneumoniae 18.8 ± 1.06, S. aureus 23.6 ± 1.15, P. aeruginosa 24.16 ± 0.87, and E. faecalis 24.5 ± 1.54 mm at 24 h of NC-GNPs alone treatment. In electron microscopy studies, NC-GNP-treated groups showed nuclear shrinkage, nuclear disintegration, degeneration of cell walls, and inhibited chromosomal division. In contrast, normal bacterial colonies had a higher number of cell divisions and routinely migrated toward cell multiplications. NC-GNPs exhibited antibacterial efficacy against antibiotic-resistant bacteria when compared to NC extract alone. We suggest that NC-GNPs are highly valuable to the population of hospitalized patients and other people to reduce the primary complications of contact lens contamination-oriented microbial infection and the therapeutic efficiency of antibiotic-resistant bacterial pathogenicity.

National cervical cancer burden estimation through systematic review and analysis of publicly available data in Pakistan.

BACKGROUND: Cervical cancer is a major cause of cancer-related deaths among women worldwide. Paucity of data on cervical cancer burden in countries like Pakistan hamper requisite resource allocation. OBJECTIVE: To estimate the burden of cervical cancer in Pakistan using available data sources. METHODS: We performed a systematic review to identify relevant data on Pakistan between 1995 to 2022. Study data identified through the systematic review that provided enough information to allow age specific incidence rates and age standardized incidence rates (ASIR) calculations for cervical cancer were merged. Population at risk estimates were derived and adjusted for important variables in the care-seeking pathway. The calculated ASIRs were applied to 2020 population estimates to estimate the number of cervical cancer cases in Pakistan. RESULTS: A total of 13 studies reported ASIRs for cervical cancer for Pakistan. Among the studies selected, the Karachi Cancer Registry reported the highest disease burden estimates for all reported time periods: 1995-1997 ASIR = 6.81, 1998-2002 ASIR = 7.47, and 2017-2019 ASIR = 6.02 per 100,000 women. Using data from Karachi, Punjab and Pakistan Atomic Energy Cancer Registries from 2015-2019, we derived an unadjusted ASIR for cervical cancer of 4.16 per 100,000 women (95% UI 3.28, 5.28). Varying model assumptions produced adjusted ASIRs ranging from 5.2 to 8.4 per 100,000 women. We derived an adjusted ASIR of 7.60, (95% UI 5.98, 10.01) and estimated 6166 (95% UI 4833, 8305) new cases of cervical cancer per year. CONCLUSION: The estimated cervical cancer burden in Pakistan is higher than the WHO target. Estimates are sensitive to health seeking behavior, and appropriate physician diagnostic intervention, factors that are relevant to the case of cervical cancer, a stigmatized disease in a low-lower middle income country setting. These estimates make the case for approaching cervical cancer elimination through a multi-pronged strategy.

Virtual Reality: The Future of Invasive Procedure Training?

Invasive procedures are associated with adverse events that are both hazardous to patients and expensive to treat. A trainee is expected to perform complex sterile invasive procedures in a dynamic environment under time pressure while maintaining patient safety at the highest standard of care. For mastery in performing an invasive procedure, the automatism of the technical aspects is required, as well as the ability to adapt to patient conditions, anatomic variability, and environmental stressors. Virtual reality (VR) simulation training is an immersive technology with immense potential for medical training, potentially enhancing clinical proficiency and improving patient safety. Virtual reality can project near-realistic environments onto a head-mounted display, allowing users to simulate and interact with various scenarios. Virtual reality has been used extensively for task training in various healthcare-related disciplines and other fields, such as the military. These scenarios often incorporate haptic feedback for the simulation of physical touch and audio and visual stimuli. In this manuscript, the authors have presented a historical review, the current status, and the potential application of VR simulation training for invasive procedures. They specifically explore a VR training module for central venous access as a prototype for invasive procedure training to describe the advantages and limitations of this evolving technology.

Timing of Blood Transfusions and 30-Day Patient Outcomes After Coronary Artery Bypass Graft Surgery.

OBJECTIVE: Packed red blood cell transfusion during coronary artery bypass graft surgery is known to be associated with adverse outcomes. However, the association of the timing between transfusions in relation to discharge and 30-day postoperative outcomes has not been studied. The study authors investigated the impact of transfusion timing on 30-day surgical outcomes. DESIGN: A retrospective review. SETTING: At a single tertiary-care academic hospital. PARTICIPANTS: A total of 2,481 adult patients underwent primary coronary artery bypass graft surgery between January 2014 and December 2020. MEASUREMENTS AND MAIN RESULTS: The relationship between the timing of packed red blood cell transfusion (intraoperative, postoperative, or both) and 30-day postoperative outcome variables was calculated as an odds ratio. The influence of timing of transfusion on adjusted probability of postoperative complications was plotted against the lowest intraoperative hematocrit. The median age of the population was 67 years (60.0-74.0), body mass index was 28.5 (25.6-32.3) kg/m2, and 497 (20.0%) were female. A total of 1,588 (36%) patients received packed red blood cell transfusions; 182 (7.3%) received intraoperative transfusions, 489 (19.7%) received postoperative transfusions, and 222 (9.0%) received both (intraoperative and postoperative transfusions). Postoperative transfusion was associated with significantly higher odds of readmission (1.83 [1.32-2.54], p = 0.002) and heart failure (1.64 [1.2-2.23], p = 0.008) compared to patients with no transfusions; whereas intraoperative transfusions were not. CONCLUSION: The authors' data suggested that the postoperative timing of transfusion in patients undergoing coronary artery bypass graft surgery may be associated with an increased incidence of 30-day heart failure and readmission. Prospective research is needed to conclusively confirm these findings.

Do boys complete the family: Sex selection by choosing when your family is complete?

OBJECTIVE: Preference for sons has sometimes resulted in adverse practices such as female infanticide or neglect in some cultures. We analyzed data from a population representative survey in an urban informal settlement in Rawalpindi, Pakistan to identify if there was a preference for boys by couples. The preferences of couples were measured by comparing the gender of the last child in the family with other relevant indicators. METHODS: Data from a cross-sectional survey from Dhok Hassu, Rawalpindi are presented. Dhok Hassu is an urban informal settlement where an urban lab was established to test health and development interventions. Data were gathered from 1556 Married Women of Reproductive Age (MWRA) through cluster randomization and analyzed through descriptive statistics and a binomial regression. RESULTS: The sex ratio for all children is 1.16 in favour of boys and increases 1.39 for the last child and increases to 2.45 among certain (Afghan) ethnic households. When a boy, as opposed to a girl, is the last child, the family size is 4.21 vs. 3.95 children (p: 0.044), Preference for sons is evident in Dhok Hassu where women desire and are on average likely to have another child if the youngest living child is a daughter. Family size was larger and contraceptive use was high in families where the last child was male with an AOR of 2.018, LL: 1.255, UL: 3.244. CONCLUSIONS: A relatively less well described method of sex selection is described where couples continue to have children until they have a boy. In effect, having boys complete families. There is need to better understand motivations of families to have boys in the changing context of societies, particularly in the face of urbanization and increasing entry of women in work place.

Ultrastructure Features and Three-Dimensional Transmission Electron Tomography of Dhub Lizard (Uromastyx Aegyptia) Cornea and Its Adaptation to a Desert Environment.

We report ultrastructural features and transmission electron tomography of the dhub lizard (Uromastyx aegyptia) cornea and its adaptation to hot and dry environments. Six corneas of dhub lizards were fixed in 2.5% glutaraldehyde and processed for electron microscopy and tomography. The ultrathin sections were observed with a JEOL 1400 transmission electron microscope. The cornea of the dhub lizard is very thin (~28-30 µm). The epithelium constitutes ~14% of the cornea, whereas the stroma constitutes 80% of the cornea. The middle stromal lamellae are significantly thicker than anterior and posterior stromal lamellae. Collagen fibril (CF) diameters in the anterior stroma are variable in size (25-75 nm). Proteoglycans (PGs) are very large in the middle and posterior stroma, whereas they are small in the anterior stroma. Three-dimensional electron tomography was carried out to understand the structure and arrangement of the PG and CFs. The presence of large PGs in the posterior and middle stroma might help the animal retain a large amount of water to protect it from dryness. The dhub corneal structure is equipped to adapt to the dry and hot desert environment.

Collagen Fibrils and Proteoglycans of Macular Dystrophy Cornea: Ultrastructure and 3D Transmission Electron Tomography.

We report the ultrastructure and 3D transmission electron tomography of collagen fibrils (CFs), proteoglycans (PGs), and microfibrils within the CF of corneas of patients with macular corneal dystrophy (MCD). Three normal corneas and three MCD corneas from three Saudi patients (aged 25, 31, and 49 years, respectively) were used for this study. The corneas were processed for light and electron microscopy studies. 3D images were composed from a set of 120 ultrastructural images using the program "Composer" and visualized using the program "Visuliser Kai". 3D image analysis of MCD cornea showed a clear organization of PGs around the CF at very high magnification and degeneration of the microfibrils within the CF. Within the MCD cornea, the PG area in the anterior stroma was significantly larger than in the middle and posterior stroma. The PG area in the MCD cornea was significantly larger compared with the PG area in the normal cornea. The CF diameter and inter-fibrillar spacing of the MCD cornea were significantly smaller compared with those of the normal cornea. Ultrastructural 3D imaging showed that the production of unsulfated keratin sulfate (KS) may lead to the degeneration of micro-CFs within the CFs. The effect of the unsulfated KS was higher in the anterior stroma compared with the posterior stroma.

Exploring the typology of decision-makers, institutions, and incentives that shape health decisions in Pakistan and insulate decision makers from citizens feedback.

Introduction: In developing countries such as Pakistan, program and policies underperform in providing public good as weak institutions lead to decisions that are unresponsive to citizens and are driven by personal motivations of the incumbents. We describe the decision-making processes in the health sector through the framework of "Public Choice" theory which posits how individual motives shape institutional performance and direction. Methods: We conducted 84 qualitative interviews with five types of stakeholders: politicians, senior and mid-level bureaucrats, donors, public health experts and media personnel spanning 2 periods over a decade. The initial interviews were conducted during 2013-2015 period and a case study on decision-making during the COVID-19 response was added in 2020-2022 period. Findings: Most new ideas originate from top political leadership, guided by personal agendas or political expediency. Senior bureaucrats implement politicians' agenda and mid-level officials maintain the status quo and follow established "authority." Since officials' performance, promotions, transfers, and the rare dismissals are based on tenure deviations rather than work performance, individuals and institutions are reluctant to take initiative without "consensus" among their colleagues often leading to inaction or delays that obviate initiative and reform. The public sector lacks institutional memory, formal information gathering, and citizen engagement, impacting public goods, health services, and policies. Media and donor personnel are important influencers. However, media mostly report only "hot issues" in health, with short publication and reader attention cycles. Donor personnel are the most likely to follow evidence for decision making, albeit while following their institutional priorities determined centrally. The COVID-19 response is presented as a contrast from usual practices, where evidence was used to guide decisions, as the pandemic was perceived as a national threat by the highest leadership. Conclusion: Absence of citizen feedback and formal systems for evidence gathering and processing leads to decisions that neglect the needs of those they serve, prioritizing personal or political gains and perpetuating the status quo. However, the COVID-19 pandemic emphasized the importance of evidence-based decision-making and offers valuable lessons for reforming decision-making processes.

A Learning Health System Approach to Increasing Human Papillomavirus Immunizations Among Young Adults.

INTRODUCTION Immunization rates against the human papillomavirus (HPV) remain suboptimal in the young adult population. Little is known about the most effective means for encouraging vaccination in this population. METHODS The authors conducted a clinical trial of 3 methods to encourage HPV vaccination in a large Northern California integrated Health Plan. Young adults aged 18-26 with evidence of insufficient HPV vaccination were sent a bulk secure message from the Health Plan (standard outreach); those who did not respond were randomized to no further outreach, a second, personalized secure message from a specific practitioner, or a letter mailed to their home. The primary outcome was receipt of at least 1 HPV vaccine within 3 months following the initial bulk secure message. RESULTS In total, 7718 young adults were randomized. After 3 months, 86 patients (3.5%) who received no additional outreach obtained an immunization, compared with 114 (4.6%) who received the second secure message (p = 0.05) and 126 (5.1%) who received the mailed letter (p = 0.006). DISCUSSION Supplemental mailed or personalized electronic messages increased vaccination beyond no additional intervention, although gains were not clinically meaningful. These findings highlight the need for more successful alternatives to encourage uptake of such preventive health interventions among young adults. The successful conduct of this rapid-cycle, randomized trial showed that such evaluations are feasible, providing actionable data to inform implementation strategies. CONCLUSIONS Further study is needed to identify effective strategies for improving preventive health uptake in this important and underserved population. Rapid-cycle randomized evaluation strategies can provide critical information to focus efforts for achieving this goal.

Deep learning applications in neuro-oncology.

Deep learning (DL) is a relatively newer subdomain of machine learning (ML) with incredible potential for certain applications in the medical field. Given recent advances in its use in neuro-oncology, its role in diagnosing, prognosticating, and managing the care of cancer patients has been the subject of many research studies. The gamut of studies has shown that the landscape of algorithmic methods is constantly improving with each iteration from its inception. With the increase in the availability of high-quality data, more training sets will allow for higher fidelity models. However, logistical and ethical concerns over a prospective trial comparing prognostic abilities of DL and physicians severely limit the ability of this technology to be widely adopted. One of the medical tenets is judgment, a facet of medical decision making in DL that is often missing because of its inherent nature as a "black box." A natural distrust for newer technology, combined with a lack of autonomy that is normally expected in our current medical practices, is just one of several important limitations in implementation. In our review, we will first define and outline the different types of artificial intelligence (AI) as well as the role of AI in the current advances of clinical medicine. We briefly highlight several of the salient studies using different methods of DL in the realm of neuroradiology and summarize the key findings and challenges faced when using this nascent technology, particularly ethical challenges that could be faced by users of DL.

Plasmodium vivax Mimicking Morphologic Features of Plasmodium falciparum.

Plasmodium vivax (P. vivax) is the most common cause of malaria in Pakistan. Several cases of severe malaria due to P.vivax have been reported from Pakistan and India, however morphological characteristics of the parasite have been mainly ignored. We present two cases of P. vivax mono-infection, which were characterized by multiple infected red blood cells, similar to that seen in Plasmodium falciparum, as observed under microscopy. Both cases were confirmed as mono-infection of P.vivax on Giemsa stained thick and thin films, malaria rapid diagnostic test (RDT) and Polymerase Chain Reaction (PCR). Morphology on peripheral blood smear remains the gold standard for diagnosis of malaria and mimicking morphological features leads to misdiagnosis and mismanagement of patients.

Large sharing networks and unusual injection practices explain the rapid rise in HIV among IDUs in Sargodha, Pakistan.

BACKGROUND: Of the nearly 100,000 street-based IDUs in Pakistan, 20% have HIV. We investigated the recent rise in HIV prevalence from 12 to 52% among IDUs in Sargodha despite > 70% coverage with syringe exchanges. METHODS: We interviewed approximately 150 IDUs and 30 outreach workers in focus group discussions. RESULTS: We found six rural and 28 urban injecting locations. Urban locations have about 20-30 people at any time and about 100 daily; rural locations have twice as many (national average: 4-15). About half of the IDUs started injecting within the past 2 years and are not proficient at injecting themselves. They use street injectors, who have 15-16 clients daily. Heroin is almost exclusively the drug used. Most inject 5-7 times daily.Nearly all injectors claim to use fresh syringes. However, they load, inject and share using a locally developed method called scale. Most Pakistani IDUs prefer to double pump drug the syringe, which allows mixing of blood with drug in the syringe. The injector injects 3 ml and keeps 2 ml (the scale) as injection fee. The injector usually pools all the leftover scale (now with some blood mixed with drug) either for his own use or to sell it. Most IDUs backload the scale they buy into their own fresh syringes. DISCUSSION: Use of an unprecedented method of injecting drugs that largely bypasses fresh syringes, larger size of sharing networks, higher injection frequency and near universal use of street injectors likely explain for the rapid rise in HIV prevalence among IDUs in Sargodha despite high level provision of fresh syringes. This had been missed by us and the national surveillance, which is quantitative. We have addressed this by hiring injectors as peer outreach workers and increasing syringe supply. Our findings highlight both the importance of qualitative research and operations research to enrich the quality of HIV prevention programs.

Cornea and its adaptation to environment and accommodation function in veiled chameleon (Chamaeleo calyptratus): ultrastructure and 3D transmission electron tomography.

We investigate the ultrastructural features and 3D electron tomography of chameleon (Chamaeleon calyptratus) which is a native of desert environments of Saudi Arabia. The corneas of the chameleon were fixed in 2.5% glutaraldehyde containing cuprolinic blue in sodium acetate buffer for electron microscopy and tomography, and observed under a JEOL 1400 transmission electron microscope. The thin cornea (21.92 µm) contained 28-30 collagen fibril lamellae. The middle stromal lamellae (from 13 to 19) contained keratocytes with a long cell process and filled with granular material. The CF diameter increased from lamella 1 (30.44 ± 1.03) to Lamella 5 (52.83 ± 2.00) then decreased towards the posterior stoma. The percentage of large CF diameters (55-65 nm) was very high in the lamellae L14 (38.8%) and L15 (85.7%). The mean PGs area of the posterior stroma (448.21 ± 24.84 nm2 ) was significantly larger than the mean PGs area of the anterior, (309.86 ± 8.2 nm2 ) and middle stroma 245.94 ± 8.28 nm2 ). 3D electron tomography showed the distribution of PGs around and over the CF. Variable diameters of CFs in the anterior stroma may provide compact lamellae which may restrict the low wavelength of light. Variable diameters of CFs in the anterior stroma may provide compact lamellae which may restrict the low wavelength of light. This accommodation function is achieved by bending of the cornea. During bending the anterior stroma was stretched and the posterior stroma was compressed due to the presence of small CFs. The middle stroma remained stiff due to the presence of large CFs. Large proteoglycans not only maintain hydration for a longer period of time, but also act as a lubricant to neutralise the shear forces in the anterior and posterior stroma during bending.