Real computer lens design and applications..
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Computer lenses are designed specifically for computer use to reduce eye strain. They have features like blue light filtering, anti-reflective coating, and a wider intermediate vision zone compared to regular prescription lenses. Computer lenses accurately correct refractive errors and are optimized for the 18-28 inch viewing distance of computer screens. Various designs exist like single vision, computer progressives, and occupational bifocals/trifocals. The ideal computer lens reduces glare, enhances contrast, blocks blue light, and provides clear vision at intermediate distances for prolonged computer use. Precise measurements are needed to position the optical center over the pupil for comfort.
Real computer lens design and applications..
- 1. Computer lens : Uses, Applications & Designs Presenter: Bipin Koirala IOM , MMC
- 2. Computer lenses Computer lenses are the prescription glasses that are designed to wear when doing computer related work.
- 3. Why do we need computer lens ? What is computer vision syndrome ? Computer vision syndrome / Digital eye strain A group of eye and vision-related problems that result from prolonged computer, tablet, e-reader and cell phone use.
- 4. What are the symptoms of computer vision syndrome? Eyestrain Headache Blurred vision Dry eyes Neck and shoulder pain Reduced work efficiency
- 5. What are the factors to cause digital eye strain?? Glare on a digital screen Poor lighting Improper viewing distances Poor seating posture Uncorrected vision problems A combination of these factors
- 6. • Uncorrected or Under corrected vision problems can be major contributing factors to computer-related eyestrain • Which includes all form of refractive errors i.e. Myopia , Hyperopia Astigmatism and Presbyopia
- 7. Role of pixels on computer vision syndrome • Pixels on screen of computer screen don’t have well defined margin and are brighter at center and diminish towards periphery. • It makes eye difficult to focus during long working time. Pixels ?? Pixels are tiny dots on computer screen that makes up a image
- 8. What is blue light ? • Scatters more easily than other visible light, it is not as easily focused. Blue light?? Blue light is short wavelength and high energy visible light rays
- 9. How does blue light contribute CVS? When we're looking at computer screens and other digital devices that emit significant amounts of blue light, this unfocused visual "noise" reduces contrast and can contribute to digital eye strain.
- 10. • Research has shown that lenses that block blue light with wavelengths less than 450 nm (blue-violet light) increase contrast significantly. • Computer glasses with blue light filter may increase comfort when you're viewing digital devices for extended periods of time.
- 11. What are the sources of Blue light ? • Fluorescent light • Flat screen of TV , smartphones , computer screen • LED light used indoor
- 12. A Study of Computer Vision Syndrome at the Workplace - Prevalence and Causative Factors Soumya Harapanahalli Venkatesh1 , Anita T Girish1 , Shashikala2 , Praveen Kulkarni3 , Snigdha Mannava4 , Rajendra Rajarathnam5 Results: The prevalence of vision related problems were reported by 83.5% of subjects. Association of duration of computer use and visual symptoms was noted. Only 38.8% of them were aware of Computer Vision Syndrome. Symptoms were more in people who did not use anti-glare glasses. Research corner
- 13. Research corner Nepalese Medical Journal, (2018) Vol. 1, Computer Vision Syndrome Prevalence and Associated Factors Among the Medical Student in Kist Medical College Basnet Anjila,1 Basnet Pragya,1 Karki Poojyashree,1 Shrestha Shriraj2 1 Department of Ophthalmology, KIST Medical College and Teaching Hospital, Lalitpur, Nepal 2 Department of Orthopaedics, KIST Medical College and Teaching Hospital, Lalitpur, Nepal
- 14. Results: Among 100 medical students 74% of the medical students sampled who used to spend 2 hours or more on their digital screens on a daily basis were complaining of one or more of CVS manifestation. Eye strain, burning eyes, neck, shoulder, or back pain, dryness, irritation and redness of eyes, headaches during or after working on computer and overall body fatigue were recorded in 89%,87%,78%,77%,71%and 68% respectively.
- 15. What should we expect from a ideal computer lens? Reduce glare Correct refractive error Enhance contrast Eliminate blue rays Reduce unwanted reflections Work for intermediate distance( Presbyopia)
- 16. Anti reflection coating • Main purpose of AR coating is to reduce unwanted reflection from front as well as back surface of lens • AR coating works on the Principle of interference. • As reflection decreases light transmission increases • AR coating has wide application like as applied with photochromic , various tinted sunglass lenses , ophthalmic lens equipment's.
- 17. • Beside ARC is also used to look good i.e. better cosmesis. • ARC coating has great role in a computer lens as it reduces unwanted reflection and glare hence reducing eye strain
- 18. • Regular plastic lenses reflect roughly 8 percent of light hitting the lenses, so only 92 percent of available light enters the eye for vision. • High index plastic lenses can reflect up to 50 percent more light than regular plastic lenses
- 19. Today's modern anti-reflective coatings can virtually eliminate the reflection of light from eyeglass lenses, allowing nearly 99.5 percent of available light to pass through the lenses and enter the eye for good vision. Popularly found coating of AR are Zeiss’s foundation coating , Crizal , UTMC
- 20. Graphical representation of light transmission in AR coated and non coated lens 0 10 20 30 40 50 60 70 80 90 100 uncoated plastic lens AR coated lens Transmission %
- 21. • Magnesium fluoride , sodium oxide , oxides of Titanium, Zirconium are commonly use AR materials. • Typically 6-7 layers of AR coating are available with alternate layer of high and low refractive index materials. • To decrease further reflection multilayer is used but efficiency of AR coat is not related to no of layers used.
- 22. • Recently Rhodenstocks 11 layered coating is available in market. • Other coating like hydrophobic coat , hard coat are used along with AR coating. • Hoya marketed Recharge EX3 Anti-reflective treatment that blocks high-energy blue light emitted by electronic devices — such as computers, e-readers, smartphones, and even energy-efficient light bulbs — that could be damaging to the eyes over time.
- 23. Why multi layer AR coat? Multi layer coat actually is designed so that it can work for large range of wavelength To work efficiently for large range of incident angle
- 24. What does color of AR coat indicate? Color in multi layer coat is actually due to residual reflection on the lens surface . If coat looks Green then it is transmitting Red and Blue light. If coat is Blue, it is transmitting longer wave length like Green , Red.
- 25. Coatings in a typical computer lens
- 26. Blue ray cut lens • Special type of lens • Blocks blue light with wavelengths less than 450 nm (blue-violet light) increase contrast significantly • Special polymeric resin are used during during lens manufacturing which gives it blue light eliminating property.
- 27. Refractive error and Computer lens options • For patient above 40 yrs Bifocals can provide clear distance and near vision, but intermediate vision (needed for computer use and seeing your smartphone) often remains a problem. • And progressive lenses or trifocals, though they offer some help for intermediate vision, often don't have a large enough intermediate zone for comfortable computer work.
- 28. • Computer glasses also should accurately correct any astigmatism we might have. • Precise measurements should be taken to insure the optical center of each lens is directly in front of your pupils when you are looking at your preferred working distance.
- 29. • Computer glasses should have about 60 percent the magnifying power of reading glasses. • But the optimal magnification depends on how far you prefer to sit from your computer screen and how close you like to hold your digital devices • For the greatest comfort at your computer, you may benefit from having a Customized Eyeglasses prescription for your computer work.
- 30. • Computer glasses are also a good choice if you wear bifocals or progressive lenses, because these lenses are generally not optimal for the distance to your computer screen.
- 31. What exactly is “Computer Glasses?” Is it different from a routine Presbyopic Glasses?... • Regular Eyeglasses (For Far Vision) & Reading (Presbyopia) glasses are Entirely different from Computer Glasses. • Regular glasses (For Far & reading) are probably not quite right for computer work.
- 32. • Many people have misconception that the Reading / Presbyopic Glasses & the Computer Glasses are the same things. Unfortunately, This is a “Myth” Reality: Reading Glasses are for near vision only (For 12 to 18 inches from the eye) to read the newspaper or any other printed material.
- 33. Now, Computer Screens are positioned “20 to 26 inches” away from the eyes. Average Distance for Computer Work is “18 to 28 inches” away from the eyes. So Reality is that, Computer Work falls in the “Intermediary Zone of Vision”
- 34. 21st Century Zones of Vision Far Zone : > 20 Feet's (6 meters) (For Driving Vehicles) Intermediary Zone : 18 to 28 inches (For Computer Work) Near Zone :12 to 18 inches (For Reading and other near Work)
- 35. What was real Problem with 19th century Prescription of Glasses?? • During 90s most young people wear single vision eyeglasses to correct their distance vision. • Reading glasses are prescribed to correct near vision only. • And bifocals prescribed for those over age 40 with presbyopia correct only near and far.
- 37. Even trifocals and progressive lenses (which do have some lens power for intermediate vision) have only a small portion of the lens dedicated to this area. Hence not comfortable for computer work Many people try to compensate for their blurred vision by leaning forward, or by tipping their head to look through the bottom portion of their glasses. Both of these actions can result in a sore neck, sore shoulders and a sore back.
- 38. Lens design options for computer glass Bifocal lens design Single vision lens designPAL design Multi focal lens design Clip on design
- 39. Single vision lens Consists of modified lens power prescribed to give the most comfortable vision at the user's computer screen. This lens relaxes the amount of accommodation required to keep things in focus at the distance of the computer screen and provides the largest field of view Reducing the risk of eyestrain, blurred vision, and unnatural posture that can cause neck and back pain. Used comfortably by younger and older computer
- 40. Occupational PALs Popular type of computer eyeglass lenses for people with presbyopia It is a multifocal lens that corrects near, intermediate, and distance error. larger intermediate zone than regular progressive lenses for more comfortable vision at the computer works. It has less lens area for distance vision. So these lenses are not recommended for driving or other significant distance vision tasks.
- 41. Hard design vs soft design PAL Soft design PAL are better for computer work Wide intermediate zone. Occupational PALs are marketed as AO Technica , Hoya Tact
- 42. Comparison between ordinary PAL & computer PAL
- 43. Research corner Comparison of progressive addition lenses for general purpose and for computer vision: an office field study Wolfgang Jaschinski Dr Ing , Mirjam König Dipl Ing (FH) , Tiofil M Mekontso Dipl Stat Arne Ohlendorf Dr Sc Hum , Monique Welscher Dipl Ing (FH) Background: Two types of progressive addition lenses (PALs) were compared in an office field study: 1. General purpose PALs with continuous clear vision between infinity and near reading distances and 2. Computer vision PALs with a wider zone of clear vision at the monitor and in near vision but no clear distance vision.
- 44. • Results Head inclination when looking at the monitor was significantly lower by 2.3 degrees with the computer vision PALs than with the general purpose PALs. Vision at the monitor was judged significantly better with computer PALs, while distance vision was judged better with general purpose PALs; however, the reported advantage of computer vision PALs differed in extent between participants. Accordingly, 61 per cent of the participants preferred the computer vision PALs, when asked without information about lens design. After full information about lens characteristics and additional eight weeks of free spectacle use, 44 per cent preferred the computer vision PALs.
- 45. Computer trifocal Another option for presbyopic computer users What is difference between ordinary trifocal and computer trifocal?? larger intermediate zone than regular trifocalsAnswer: Provides wide field of view and better comfort for prolonged work
- 46. Occupational bifocal Another option for presbyopic computer users What is difference between ordinary bifocal and occupational bifocal?? Answer: The top part of this lens for intermediate vision (computer screen} the bottom portion for near vision (reading). Provides better comfort for person who needs frequent switch of view between near and intermediate distance Proof readers , Article typers in publication companies
- 47. Clip-ons Computer lenses are also available in clip-ons that can be attached to regular eyeglasses Clip on piece will have added power needed for intermediate distance over distance RX
- 48. Over – The - Counter glasses Small plus powered lens is worn over-the-counter glasses . Usually of power (+1 to +1.50 Dsph) Not a better option
- 49. Prism lens • Reliving type of prism correction are considered Not commonly used option
- 50. How to calculate power for computer lens ??? Find distance Rx of patient in both eyes •Step 1 Find the add power needed for comfortable near work •Step 2 Power for computer glass = distance power + ( near / 2) •Step 3
- 51. Example A 45 yrs old male presented to optometry clinic with a complain of eye strain during prolonged computer work with no history of use of glass Step 1 (Distance correction is done ) OD: +0.50 Dsph = 6/6 OS: +0.75 Dsph = 6/6 Step 2 : (Near correction determined ) OU: + 1.50 Dsph = N6 ( plus build up method ) Step 3 : Calculation of computer lens OD: +1.25 DSph OS: +1.50 Dsph
- 52. Tints in computer lens • Anti-blue light lenses fight glare while their tint improves the screen/light contrast, helping to prevent fatigue and the strain often caused by computer user • Lens color is yellow.
- 53. • The Hayden Tinted Computer Reader is a full framed style with a slight tint for easing eye strain while at the computer. The Hayden has the magnification you select on the entire lens along with a light amber tint, and anti-glare coating.
- 54. • Pink (also rose or red) most soothing for their eyes and preferred by many computer users.
- 55. Is there any role of polarizing lens for computer use?? • Polarizing lens are often combined with glass tints • Some companies suggest that , they help against reflected glare from visual display unit (VDU) . • Similarly some polarizing sheet are used over screen to reduce unwanted light . • Not so popular.
- 58. References Clinical optics. System for ophthalmic dispensing. CET articles Internet
Editor's Notes
- #13: Material and methods: Cross sectional study was conducted among the software professionals of a multinational company. Informed consent was obtained from the study subjects after inclusion criteria were met. Data was collected using a selfadministered pre tested questionnaire. Data was analysed using SPSS version 22 program
- #22: Magneta color in single layer …. Color is due to residual reflection. Mgf2 glass and quartz plastics More layer more transmission more neutral color hues. Efficiency depends on refractive index of coat , degree of adherence of coat with layers , thickness of coat. In multi layer these layers are alternately half wave length and quarter wave length in thickness. mu
- #42: Hard design Soft design Spherical distance zone Aspheric distance zone Wider distance and near vision zone Narrower distance and near vision zone Narrow and short intermediate corridor Wide and large intermediate corridor Rapid increase in unwanted astigmatism Gradual increase in unwanted astigmatism
- #46: Lined trifocal
- #47: Also called enhanced near lens