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Glaucoma

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Authors

Piotr Kanclerz, MD, PhD, works in private practice at the Medical University of Gdańsk in Poland.

Extended depth-of-field IOLs: Clarifying current nomenclature

A recurring feature at the 2024 American Society of Cataract and Refractive Surgery (ASCRS) Annual Meeting in Boston, Massachusetts, was the call for environmentally friendly practices worldwide, with the goal of decreasing the impact of ophthalmic surgeries on the planet.

A driving force in this movement is EyeSustain

 an organization dedicated to the development of such friendly environmental practices, that exists as a global coalition of eye societies providing education and resources to support sustainable practices in ophthalmology.

Here is a sampling of the ASCRS discussions on the topic.

Greening eye care: reducing ophthalmology’s environmental footprint

The presenters, led by first author Sarishka Desai, BA, described the EyeSustain platform and its 5-pronged mission: educate the global ophthalmic community about more sustainable practices, collaborate with industry to reduce our carbon footprint and surgical waste, support research and innovative solutions that reduce ophthalmology’s environmental impact, support advocacy and education about the public health impact of climate change, and collaborate with industry to reduce our carbon footprint and surgical waste.

Desai, of the University of Connecticut School of Medicine in Farmington, and colleagues presented EyeSustain’s approach to reducing the ophthalmic carbon footprint. She was joined in the study by Nitya Devireddy, BS, MPH, of Penn State College of Medicine in Hershey, Pennsylvania; Sofia Miguez, BA, of Yale School of Medicine in New Haven, Connecticut; and Barbara Erny, MD, of the Department of Ophthalmology at Stanford University in California.

The greenhouse gas data associated with health care are startling. Health care is responsible for 4.4% of all global greenhouse gas emissions, 71% of which arise from the manufacturing, use, and disposal of medical supplies. Ophthalmology has the highest procedural volume of any surgical specialty, with 50 million cataract surgeries expected to be performed globally each year by 2050, Desai reported.

In light of the procedural data, the authors highlighted 6 areas that are currently undergoing research and quality improvement initiatives through the EyeSustain system.

 of cataract surgeons and nurses by David Chang and Cassandra Thiel found that 93% of respondents believe that the trash associated with OR procedures is excessive, and that methods to reduce waste should be identified and implemented.

 encouraged regulatory agencies to allow electronic instructions for use be disseminated in lieu of the traditional paper instructions included with each cataract pack.

Ongoing projects spearheaded by EyeSustain members, including medical students and ophthalmology residents, are taking a look at educating surgeons and surgical staff about sustainability and the impact of OR waste, OR water consumption, and evaluation of flash sterilization associated with cataract surgery.

In recognition of the fact that medications in the OR represent an estimated $560 million in waste annually, a multisociety position paper

 recently formulated 3 key recommendations: topical drugs in multidose containers can be used for multiple patients in surgical facilities if proper guidelines are followed; topical drugs in multidose containers can be used until the manufacturer’s labeled date of expiration if proper guidelines are followed; and, when applicable, patients should be able to take their partially used medication home for postoperative use.

The Aravind Eye Care system’s low-carbon model from Madurai, India, uses alternate energy sources, transport, infrastructure, and equipment maintenance.

 Studying global systems of eye care and waste produced can provide a deeper understanding of the impact of hospitals and providers on climate change, as well as ideas on how western eye care systems can proactively reduce carbon emissions.

The EyeSustain platform includes ophthalmology-specific action steps for greening offices and clinics in collaboration with the 

Partnerships can be established with large manufacturers to reduce packaging, make instruments reusable, and streamline the manufacturing and distribution processes.

In addition to the impact of practice waste on the environment, EyeSustain also recommends studying the effects of climate change on the incidence rates of ophthalmologic conditions, including cataracts, allergic disease, and glaucoma, among others.

Desai and her colleagues recommended that institutions take the following steps:

Conduct a waste audit to quantify the carbon footprint of an institution’s OR emissions. This includes using the EyeSustain-Zasti Carbon Footprint Calculator, using the Sustainability Index for Disposables in Cataract Surgery calculator for cataract packs to evaluate the item-by-item potential for carbon dioxide savings, and surveying clinical staff to identify areas of perceived excess waste.

Identify key stakeholders at an institution and an enthusiastic, multidisciplinary team and completing the OR Sustainability Pledge (

), which has been completed by ambulatory surgery centers/hospital outpatient departments from 9 countries thus far.

Implement best practices; multisociety recommendations for sustainability are easily accessible at eyesustain.org and My Green Doctor for outpatient/clinic resources and local legislation using the American Academy of Ophthalmology Topical Medical Waste Reduction Act legislative template.

Using phacoemulsification waste to guide changes in surgical sustainability

Adjustments to improve the sustainability of ophthalmic surgical practice can have a large impact when scaled to case volume, according to author Margaret Tharp, BSc, who described this study at the ASCRS meeting. She and her coauthors Stella Protopapas, BA, MPH, and Minka Gill, BSc, are from the Indiana University School of Medicine in Bloomington, whereas David J. Palmer, MD, ABO, is from the Northwestern University Feinberg School of Medicine in Chicago, Illinois.

In their study, they sought to draw connections between results from a 24-hour waste audit at an outpatient surgical center and current resources available from EyeSustain to improve the sustainability of ophthalmic surgical practice.

The authors documented the extensive waste generated from 1 day of surgeries in an institution that included 13 phacoemulsification procedures, 5 plastic surgeries, 3 urologic surgeries, and 5 otolaryngologic cases. The waste products were sorted as medications (eg, propofol, eye drop containers), textiles (eg, surgical gowns, drapes), metals (eg, metal wiring, disposable instruments), and plastics (eg, hard, soft, wrappings).

When the amounts of the waste products were tallied, the authors found that “ophthalmology produced the greatest amount of waste in a single day relative to other operating specialties, despite producing the least amount of waste per case. Most ophthalmic waste was from textiles, hard plastics, and medications,” the authors reported.

The specific 13 phacoemulsification procedures resulted in 95.4 lb of waste broken down as follows: 18.5 lb of hard plastic, 5.5 lb of soft plastic, 8.3 lb of wrapping, 13.5 lb of medications, 41.2 lb of textiles, 6.7 lb of miscellaneous waste, and no metals. Compared with other operating specialties, ophthalmology produced the least amount of waste per case but the greatest amount of waste in total due to the relatively high case volume.

It has been reported that “discarded/unused pharmaceuticals from US cataract surgeries demonstrated waste of [approximately] $150 per case while generating carbon dioxide–equivalent emissions that approximated 25,000 to 100,000 flights from San Francisco, California, to Boston annually.

Small changes can have dramatic results. Tharp and colleagues suggested that the following would have positive consequences.

Revising the use of tetracaine bottles intraoperatively; for example, reusing the bottles between cases or sending the bottles home with patients

Optimizing packaging of surgical supplies and electronic instructions

Utilizing intravenous sedation to limit anesthesia gas carbon dioxide–equivalent emissions

Focusing on cutting waste also creates an opportunity to explore the practices of global leaders in sustainable eye care, such as the efforts of the Aravind Eye Hospitals, which provide similar surgical success rates at a fraction of the waste produced by US practices.

 A downside may be that such practices require significant reuse of materials, central sterilization, and stakeholder diligence, which can require complex interventions, according to Tharp. 

EyeSustain’s Surgical Facility Sustainability Pledge can serve as a guide for ophthalmologists to improve the sustainability of their practice in an approachable and lasting manner.

Factors contributing to the carbon footprint of cataract surgery

Omar Taboun, MSc, a medical student at Western University’s Schulich School of Medicine & Dentistry in London, Ontario, Canada, working under the direction of Netan Choudhry, MD, FRCSC, also described the negative impact of cataract surgery on the environment at the ASCRS meeting.

He commented, “We know that climate change can affect human health through various means, such as adverse weather events causing injury and exposure to pollutants [exacerbating] underlying health conditions. As health care providers, it is our responsibility to treat patients for their conditions that may ultimately be influenced by environmental factors. Counterintuitively, the health care sector is itself a greenhouse gas emitter,” Taboun said.

Surgery contributes significant emissions to the environment through the necessary materials and tools used during procedures. In addition, the need to maintain sterility increases waste.

The term footprint indicates the sum of all emissions direct and indirect resulting from this procedure, Taboun explained, the resultant value of which is typically reported in carbon dioxide equivalents

And although cataract surgery requires only a few minutes to complete, the procedural volume has increased exponentially over the past 2 decades,

Taboun and colleagues developed a 2-fold goal: they wanted to increase their understanding of the carbon footprint and waste accumulation to identify the primary contributors and pinpoint areas for improvement to enhance the sustainability of cataract surgery.

They conducted a literature search of PubMed, Google Scholar, and Medline to identify studies related to the carbon footprint and the elements of cataract surgery. The results yielded 6 studies, with 2 being the basis for this discussion,

He highlighted 3 main points extracted from the published data: the lowest footprint published was just under 6 kg of carbon dioxide equivalents; the highest published footprint was just over 180 kg of carbon dioxide; and the major factors contributing to the footprint include procurement of pharmaceuticals and materials, building and energy use, such as heating/cooling, lighting, electricity-powered tools, and travel by patients and staff to the location where the procedure is performed.

Taboun directed attention to centers that already have sustainable practices in place, such as the Aravind Eye Hospital, which reports the lowest footprint. These sustainable practices include the use of multiple operating tables in a single room; reusing gloves, gowns, and various medical equipment;

and using highly efficient autoclave settings.

Importantly, when these changes were implemented in the Aravind Eye Hospital,

 the rates of endophthalmitis remained comparable to other centers: 0.02% vs from 0.04% to 0.07% reported.

Taboun offered 3 ways that surgeons can offset the negative effects of cataract surgery on the environment—by focusing on procurement, energy use, and travel emissions.

Reduce emissions associated with procurement by collaborating with manufacturers to reduce packaging as much as possible and encouraging recycling in every OR.

Reduce building and energy use by incorporating renewable energy, such as solar panels, and more strategic lighting protocols and optimizing energy use within surgical centers.

Establish outreach clinics closer to more populous regions, whereby mostly staff members must travel, and patients less so, which will reduce travel emissions, along with performing bilateral procedures.

“Implementing sustainable practices, although challenging, will allow us to continuously provide this procedure and restore vision for millions of people at less of a cost to the environment,” Taboun said.

1. Chang DF, Thiel CL; Ophthalmic Instrument Cleaning and Sterilization Task Force. Survey of cataract surgeons’ and nurses’ attitudes toward operating room waste

. 2020;46(7):933-940.doi:10.1097/j.jcrs.0000000000000267

2. Schehlein EM, Hovasesian J, Shukla AG, Talley Rostov A, Findl O, Change DF. Reducing ophthalmic surgical waste through electronic instructions for use: a multi-society position paper. 

. 2024;50(3):197-200. doi:10.1097/j.jcrs.0000000000001381

3. Cleaning and Sterilization Task Force. Reducing topical drug waste in ophthalmic surgery: multisociety position paper

. 2022;48(9):1073-1077; doi:10.1097/j.jcrs.0000000000000975

4. Goel H, Wemyss TA, Harris T, et al. Improving productivity, costs and environmental impact in International Eye Health Services: using the ‘Eyeficiency’ cataract surgical services auditing tool to assess the value of cataract surgical services. 

. 2021 ;6(1):e000642. doi:10.1136/bmjophth-2020-000642. 2021

5. US EPA O. Greenhouse gas equivalencies calculator. United States Environmental Protection Agency. Updated January 2024. https://www.epa.gov/energy/greenhouse-gas-equivalencies-calculator

6. Gadani H, Vyas A. Anesthetic gases and global warming: [otentials, prevention and future of anesthesia. 

. 2011;5(1):5-10. doi:10.4103/0259-1162.84171

7. Thiel CL, Schehlein E, Ravilla T, et al. Cataract surgery and environmental sustainability: waste and lifecycle assessment of phacoemulsification at a private healthcare facility. 

. 2017;43(11):1391-1398. doi:10.1016/j.jcrs.2017.08.017

8. Pandey D, Agrawal M, Pandey JS. Carbon footprint: current methods of estimation. 

. 2011 ;178(1-4):135-160. doi:10.1007/s10661-010-1678-y

9. Pandey D, Agrawal M, Pandey JS. (2011). Carbon footprint: current methods of estimation. 

. 2011;178(1-4):135-160. doi:10.1007/s10661-010-1678-y

10 Rachmiel R, Trope GE, Chipman ML, Buys YM. Cataract surgery rates in Ontario, Canada, from 1992 to 2004: more surgeries with fewer ophthalmologists. 

11. Morris DS, Wright T, Somner JEA, Connor A. The carbon footprint of cataract surgery. 

. 2013;27(4):495-501. doi:10.1038/eye.2013.

12. Latta M, Shaw C, Gale J. The carbon footprint of cataract surgery in Wellington. 

13. Ravindran RD, Venkatesh R, Chang DF, Sengupta S, Gyatsho J, Talwar B. Incidence of post-cataract endophthalmitis at Aravind Eye Hospital: outcomes of more than 42,000 consecutive cases using standardized sterilization and prophylaxis protocols. 

. 2009;35(4):629-636. doi:10.1016/j.jcrs.2009.01.002

14, Pershing S, Lum F, Hsu S, et al. Endophthalmitis after cataract surgery in the United States: a report from the Intelligent Research in Sight registry, 2013-2017. 

. 2020;127(2):151-158. doi:10.1016/j.ophtha.2019.08.026

Organization eyes green practices, shifting ophthalmology landscape.

Minimizing the carbon footprint of ophthalmic surgeries

Ophthalmology Times Omar Salamanca Orbis Glaucoma

, Omar Salamanca, MD, staff ophthalmologist, Orbis Flying Eye Hospital, discusses Orbis's tailored glaucoma training programs, which focus on hands-on surgical skills, early detection, telemedicine, and personalized follow-up care, helping underserved regions improve glaucoma management and blindness prevention.

This transcript has been lightly edited for clarity.

. I'm joined by Dr. Omar Salamanca, staff ophthalmologist, Orbis Flying Eye Hospital, to discuss how Orbis treats and trains in glaucoma. Thanks for joining me. First, how does Orbis tailor its glaucoma treatment protocols to meet the specific needs of the regions where you provide care?

: Hi, David. Thank you for this interview, for providing this information to the people. My team, we normally visit the country 6 months or 1 year before. So, we try to understand what is happening in the ophthalmology field in the country. We have to understand what the level of training is, and we can tailor the program according to that. We can scale up or down according to the needs. Because we, as Orbis Flying Eye Hospital, can provide different levels of training, starting from basic, intermediate, or advanced. So, after these interviews, we decide what kind of surgeries we’re going to teach during the Flying Eye Hospital program.

: What role do you see telemedicine and virtual reality playing in the future of glaucoma training through Orbis, particularly with the Flying Eye Hospital?

: Well, technology definitely is something very important now to train all the personnel in eye care—not only in eye care, but in medicine. So, it’s a very important tool. And with Orbis, we have different platforms. We have Cybersight, and with Cybersight, we have a lot of courses, nearly 20 different courses, again at different levels: intermediate, basic, and advanced. We also have this system to telementor for the doctors. So, that means that we can ask the doctor to upload the information of a specific patient, and they will be connected with a glaucoma expert anywhere in the world. Within 24 hours, they will have recommendations, and they can start this conversation about the patient. It’s a very interesting platform that helps. That platform allows you to include images, which are very important in ophthalmology, and you can also upload videos. You can do it from your laptop or even from your cell phone. And another important thing is about the artificial intelligence in Cybersight. We have a system where you can upload the single images of the fundus. So, it works very well for diabetic retinopathy because it can tell you if it’s positive or negative for that disease. But we can also check for the optic disc. The system, within 10 or 20 seconds, will tell you if the optic disc is normal or abnormal. After that, you can make a decision as a doctor. I have to say that glaucoma diagnosis is a little bit more complex, so we need to consider age, intraocular pressure, and visual fields, but it’s a very important tool that we have available in Cybersight.

: What are the key challenges you face when diagnosing and treating glaucoma in underserved regions, and how does Orbis help overcome these barriers?

: Yes. There are many different barriers, according to the countries that we visit, of course. But first is sometimes the doctor doesn’t have the surgical skills to deal with this disease. But sometimes, they don’t even have the clinical skills to properly diagnose the disease. So, this is where Orbis is focused, mainly doing the MTH programs. But again, it’s mentioned in the access to the health services. Sometimes, the patients don’t live close to the centers. So, with this technology that we mentioned before, we try to close that gap. Sometimes, there’s a lack of instruments, lack of special equipment, and Orbis not only provides the training through the FEH programs, but we also work with Orbis offices in the country, so we try to do some long-term programs to address these needs.

: How does Orbis ensure that training participants acquire hands-on experience in glaucoma surgery and postoperative care, especially in complex cases?

: It’s a very dedicated process, because we plan in advance, like 1 year. One of my jobs at Orbis is to visit the country 1 year before to understand how the situation in ophthalmology is, and especially glaucoma, because that’s my specialty. So, I have a lot of interviews with the doctors who have an interest in glaucoma, trying to understand what the level of training is, because there are different surgeries that we need to perform to treat glaucoma. And those are very basic, like trabeculectomies, and sometimes include tube insertions or the MIGS. So, regarding that assessment, we decide what kind of surgery we will teach during the program, and we identify the expert in that surgery. Before we start the program, we do a simulation training week in the Flying Eye Hospital. So, that’s part of my role. I teach them with the plastic eyes, with models, and in the very safe environment without patients. I try to teach very, very specifically—how to hold the instruments, how to grab the eye. This is very important. And the following week, we have the surgeries with patients. The expert should have a lot of experience teaching residents and doctors in their home countries, so they teach them and also follow up on the outcome of the surgery. And when we finish the program, in 6 weeks or 8 weeks, it depends, one of the staff visits the country to see the outcomes and to provide feedback. It’s a very, very connected program. We try to connect.

: What kind of follow-up care is typically provided for glaucoma patients after Orbis has completed a project, and how are they monitored for disease progression?

: Yes, through our platform, Cybersight, we are able to upload the information before surgery, during surgery, and after surgery. We encourage local doctors to communicate with the volunteer faculty, our expert, but also the Orbis staff is visiting the country to be sure that the outcome is according to the clinical standards. If we identify something that is not going well, we have to provide the advice regarding how to treat the patient, and we also provide, not only advice, but sometimes some medications to treat the patient after surgery. As mentioned before, sometimes we support them with technology. So, it’s very important, not only to do the surgery, because most of the time it goes well, but with time, especially with glaucoma, you can identify some specific conditions that you need to treat to prevent the progression of the disease.

: How do the Orbis glaucoma training programs address the differences between open-angle and angle-closure glaucoma, particularly in those diverse populations with varying genetic predispositions?

: That’s a very, very interesting question. Glaucoma, in the end, is a problem in the optic nerve, which is in the back part of the eye. What you mentioned is something in the anterior segment. So, we try to focus the training, because the diagnosis may be different and treatment also may be a little bit different, but that’s part of the program that we decide. If we are going to Asia, for instance, we will find more narrow-angle glaucoma. But if we go to Africa, there’s going to be more prevalent open-angle glaucoma. So, we try to understand that context for the countries. We also identify and provide the structure or the content of the training lectures—how to make a distinction between narrow-angle and open-angle. We have to focus on gonioscopy, which is something very specific to identify if the angle is narrow or not. When you’re a glaucoma specialist, you see glaucoma as a whole, but you have to check for the details. And we’re very good at trying to identify those details because it’s very important regarding the prognosis and also the treatment.

: How do you balance teaching new glaucoma surgical techniques with the importance of improving early detection and preventive care while you’re on a training mission?

: That’s definitely a must. We cannot focus only on training in the latest surgical techniques. We have to go to prevention, and that’s not including only ophthalmologists. We also have to include local doctors—I mean, general practitioners, nurses, optometrists—because what we know about glaucoma is if we detect it earlier, we will have more chances to provide proper treatment. So, during the program, specifically, we have lectures in our classroom, and we broadcast the surgeries. But between surgeries, we are speaking about how to understand the risk factors for glaucoma, which is very important, how to properly assess the optic nerve, intraocular pressure. So, we have to do a balance. The other thing is that we raise awareness about blindness prevention. We invite people from the government, sometimes prime ministers or the Ministry of Health, and other important people, so we can bring attention to blindness prevention, and this is where glaucoma screening in the early stage has a very, very important role.

: What kind of feedback do you get from the trainees afterwards?

: Well, we have the professional feedback, which is regarding the cases. But it’s also a very good thing because we establish a good relationship with them. So, they start speaking not only about the cases that we did there in the program, but we also start having new conversations about new cases, new opportunities for them to be trained. Sometimes, we interact with them in medical conferences or at the Congress. So, it’s a very interesting part, not only in the professional field but also in the personal field. We start growing this community that’s been trained with the Orbis program. We try to establish this fair communication. And sometimes we become friends with them.

Orbis Flying Eye Hospital's glaucoma training programs are tailored to meet the specific needs of underserved regions, focusing on hands-on surgical skills, early detection, telemedicine, and personalized follow-up care. The programs utilize technology platforms like Cybersight for remote mentoring and AI-assisted diagnostics. Challenges in these regions include limited surgical and clinical skills, access to healthcare, and equipment shortages. Orbis addresses these through comprehensive training, simulation exercises, and long-term support. The programs emphasize balancing new surgical techniques with early detection and preventive care, fostering a collaborative community among trainees.

Omar Salamanca, MD, staff ophthalmologist, Orbis Flying Eye Hospital, discusses Orbis's tailored glaucoma training programs, which focus on hands-on surgical skills, early detection, telemedicine, and personalized follow-up care, helping underserved regions improve glaucoma management and blindness prevention.

Adapting glaucoma training and treatment: Insights from the Orbis Flying Eye Hospital

Our ability to perceive visual detail begins with the photoreceptor cells in our eyes. A specialized region of the retina called the fovea is responsible for high-acuity vision, and within it, color-sensitive cone photoreceptors enable us to distinguish fine details.

The density of these cones varies between individuals, influencing visual resolution. Additionally, our eyes make minute, continuous movements—differing in pattern and size across individuals—when focusing on a single object. Researchers from University Hospital Bonn (UKB) and the University of Bonn have examined how sharp vision is influenced by these small eye movements and the foveal cone mosaic.

By utilizing high-resolution imaging and micro-psychophysics, they demonstrated that eye movements are calibrated to optimize sampling by cones. Their findings were recently published in 

Humans achieve clear vision by fixating on an object through the fovea, a small pit in the retina densely packed with cone photoreceptors. This mosaic of cones reaches densities exceeding 200,000 per square millimeter, within an area roughly 200 times smaller than a quarter. These foveal cones sample the visible field and transmit signals to the brain, functioning similarly to pixels in a camera sensor with millions of photosensitive elements. Unlike camera pixels, however, cone distribution in the fovea is non-uniform, and each individual’s fovea has a unique density arrangement.

“Unlike a camera, our eyes are constantly and unconsciously in motion," explained Wolf Harmening, PhD, head of the AOVision Laboratory in the Department of Ophthalmology at UKB and a member of the Transdisciplinary Research Area “Life & Health” at the University of Bonn. 

This movement occurs even when fixating on a stationary object. These fixational eye movements introduce slight variations in photoreceptor stimulation, which the brain interprets to refine spatial details. Drift, a component of these fixational movements, varies among individuals, and excessive movement can impair vision. Until now, the relationship between drift, foveal cone distribution, and fine visual resolution remained unexplored.

Using High-Resolution Imaging and Micro-Psychophysics

Harmening’s research team addressed this gap by employing an adaptive optics scanning light ophthalmoscope (AOSLO)—the only one of its kind in Germany. This tool allowed for precise examination of the connection between foveal cone density and the smallest details perceivable. While using the AOSLO, researchers also tracked eye movements as they measured the visual acuity of 16 healthy participants engaged in a challenging visual task. The AOSLO recorded the movement of visual stimuli across participants’ retinas, enabling identification of specific photoreceptors contributing to vision.

First author Jenny Witten from the Department of Ophthalmology at UKB and a PhD candidate at the University of Bonn analyzed these movements during a letter discrimination task.

Eye Movements are Fine-Tuned to Cone Density

The study showed that humans can perceive finer details than the cone density in the fovea alone would suggest.

“From this, we conclude that the spatial arrangement of foveal cones only partially predicts resolution acuity,” Harmening noted.

High-acuity vision is facilitated by the fovea, a retinal region densely packed with cone photoreceptors. Individual variations in cone density and eye movement patterns influence visual resolution. Researchers from University Hospital Bonn and the University of Bonn demonstrated that eye movements are calibrated to optimize cone sampling, enhancing visual clarity. Using an adaptive optics scanning light ophthalmoscope, they found that drift movements align with high-density retinal areas, refining spatial details. These findings advance understanding of vision physiology and have implications for ophthalmologic and neuropsychological conditions.

A group of German researchers has discovered how tiny eye movements and the density of photoreceptors assist in visual acuity.

Piotr Kanclerz, MD, PhD

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