Sep. 01, 2025
When you decide to go ahead with cataract surgery, the first thing you decide is what type of lens to use to replace your damaged natural lens. At Kleiman Evangelista Eye Centers, we are the premier experts in cataract and LASIK eye surgery in Dallas. We’ll do everything possible to make sure the process goes smoothly.
During the procedure, we replace your natural lens with a monofocal or multifocal artificial intraocular lens (IOL). Your eye doctor will discuss the different types of premium replacement lenses available during your consultation. Fortunately, we offer all three premium lens types so you can choose from the widest selection available.
RuiQi Optics supply professional and honest service.
A premium lens can improve nearsightedness and farsightedness. Some IOLs correct for astigmatism. Most patients don’t need glasses following cataract surgery, depending on the type of lens they choose. This is in comparison to a standard, or monofocal, lens which only corrects vision at one distance.
You have many options when it comes to budgeting for traditional or premium lenses. Most patients who opt for more expensive premium lenses are more than happy with the results. Simply put, you need premium IOLs to avoid wearing glasses following your cataract surgery. These lenses mimic your natural sight, whereas monofocal intraocular lenses leave you dependent on glasses as they only correct either distance or near vision.
Premium lenses may cost much more than traditional monofocal lenses. However, most patients agree the results are worth the expense as the visual results are meant to last forever provided that the health of the eyes remains stable.
The different types of lenses include the following:
Multifocal lenses are a great choice if you do a lot of close work on the computer or with tasks such as crafting, as they typically result in better near vision. However, multifocal lenses may cause effects such as halos and glare more often than monofocal IOLs.
Many patients who receive multifocal IOLs feel like they made a good investment. These lenses improve near and far vision and often result in freedom from glasses. No routine replacement is necessary, as intraocular lenses are designed to last throughout your lifetime.
You may be able to achieve 20/20 vision without glasses following cataract surgery. However, the presence of the following conditions may prevent 20/20 vision. These conditions may be present before cataract surgery or can occur anytime after surgery:
With the assistance of glasses, most patients gain 20/20 vision following cataract surgery.
It takes between one and three months for your eyes to fully heal after cataract surgery. Once they are completely healed, you can come in for an eye exam and we will update your eyeglass prescription, if necessary.
You may not need glasses if you have good overall eye health without significant astigmatism. However, vision may still change over time with the aging process. Therefore, you may still need eyeglasses at some point.
Typically, no matter what lens you choose, you can look forward to less dependence on glasses following successful cataract surgery at Kleiman Evangelista Eye Centers.
There is no limitation on when you can undergo cataract surgery. However, it may be easier to remove cataracts before they mature. This can impact recovery time and how long the surgery takes. Mature cataracts can cause severe visual impairment and carry a higher risk of complications. Therefore, it makes sense to have the operation sooner rather than later for most people.
The artificial lenses designed for cataract surgery are meant to last a lifetime. Sometimes, the natural capsule that holds the lens becomes clouded, typically months or years after cataract surgery. If this occurs, we can treat the condition with laser therapy to restore your vision.
Exciting new technology continues to improve patient outcomes and recovery. Scientists and eye doctors are currently working on new refractive IOLs that can improve vision results following cataract surgery. Typically, eye doctors remove cataracts from one eye and let it heal prior to treating the other eye. This requires two surgeries and two trips to the clinic. The newest IOLs that we are currently using are the PanOptix lens, a trifocal lens, and the Vivity lens, an extended depth of focus lens.
[DISPLAY_ULTIMATE_SOCIAL_ICONS]Why does a larger diameter lens make a smaller beam when focused?
The same shape lens and larger has a longer focal length. The size of the spot at a given distance is about the LED size times the ratio of that distance to the focal length.
How does the ratio of diameter to depth of the lens affect the size of the beam? If a 75mm diameter by 25mm thick lens and a 75mm diameter by 15mm thick lens were to be used on the same led, which one would give the smallest focused beam and why?
The thicker and more curved the lens the shorter the focal length. It also depends on the refractive index of the material. So the thicker 75 mm. lens would have a larger spot.
What is the relationship of led die size to lens diameter? In other words, is bigger always better? LOL, I know I’m asking for trouble there, but keep it in reference to these lenses.
If the whole light scales up together, LED and lens included, the angular beam spread does not change.
Is there an optimum size for the different leds, as far as diameter of the lens?
A larger lens of the same focal length will catch more light. It doesn’t depend much on the LED.
Is there an optimum diameter vs thickness for different leds?
To get the same spot size with a larger LED one needs a larger or thinner lens.
Is there a way to determine this ahead of time. A scientific way of determining?
Most everything about optics is understood scientifically, but of course it takes more data and more work to get more detail.
The focusing specification of a lens depends on its focal length, which lesser than 15mm is quite rare. (eg.: lens placed 15mm away from LED, to get fully focused)
Thus with higher focal length, they need bigger diameter lens to cover the effective light ray from LED (XM-L2 is 125 degree i think)
Example: (using 120 degree, easier calculation)
15mm focal length
±52mm diameter lens
20mm focal length
±69.5mm diameter lens
For more information, please visit Aspheric Lens.
Even so, the light passing through lens according to calculation above is around 60-75% of the light produced only.
There are still light more than 125 degree angle. Lens is always the larger diameter, the shorter focal length, the better.
However, smaller the lens (in fully focused senario), the thinner the beam it is. (pretty much useless, unless for flashy that is)
Ideally for thrower (especially crazy type), its better to have crazy wide lens.
For exact figure or reference, I couldn’t provide you with anything, since I’m not light field specialist nor a thrower builder (not really need one, maybe I will build a pencil beam for fun) All these are base on optic science I learned, not really precise, but enough I guess…
A few years ago… I was trying out various lenses on lights to see what the results were.
I live close to Surplus Shed; and if you want to grab lenses off the shelves and try them on lights while you’re there, the owner doesn’t care.
Of course if you buy a few after your experiments, they appreciate that.
If you buy some, give good feedback on forums that might entice others to purchase a few lenses… they like that even more.
I mentioned this on another flashlight forum; and posted the results of some of the lens/light combos. I included the stock numbers of the lenses if there was anything anyone liked and wanted to try themselves.
I got lectured that you can’t just grab lenses and stick them in lights, you have to do all the math first.
One member was (politely) being outright insulting.
Anyway… here’s part of the “lecture thread” I had saved as a Word file (as it has some useful information):
Re: Aspheric lenses - 52mm/37mm fl - 52mm/33mm fl - 50mm/35mm fl - 50mm/38.5mm fl ~ B
Melles Griot Asperic Lenses.
52mm with 37mm focal length is here.
This is why I wanted to know the distance from the emitter to the back of the aspheric lens:
See, Fb is 21.9mm - so the pest possible placement of the LED from the back of the aspheric lens would be 21.9mm. MrMimzu found the distance to be 27mm, so moving the emitter slightly closer to the back of the lens should provide more throw.
The 52mm w/ 33mm focal length, the Fb is only 16mm - which would be bad.
Conversely, the 50mm w/38.5mm focal length, the Fb is 24.3mm - so if the emitter placement is indeed 27mm, then the 50mm w/38.5mm focal length should throw better.
The moral here is for maximum throw, the LED should be Fb distance from the back of the asperic lens for best throw. Having the emitter at the exact focal point of the lens should focus the most rays straight ahead - of course the focal point is measured from the middle of the lens, so we have to look at the Fb number.
Optimal distances from back of asperic lens to emitter:
52mm w/33mm fl = ~16mm
52mm w/37mm fl = ~22mm
50mm w/35mm fl = ~23mm
50mm w/38.5mm fl = ~24mm
So, considering the Fb for the 52/37 and the 50/35 are only 1mm apart - I would be surprised if they threw that much different.
You can get a magnesium fluoride AR coating on the 50mm lenses for $20 and on the 52mm lenses for $40.
I guess one of the things I don't get still, is why isn't there a way to concentrate the light (bend it), to make a smaller spot? Ok, the aspheric does that, but look at the size of a square die pattern of an XR-E and a SST-90. At 100', with an aspheric, the XR-E is very small and the SST-90 is very large. Why can't the SST-90 be focused to a relatively small spot? and if it can be, what will it take to do that? As an example only, say the XR-E square die spot is ten feet at 100 yards and the SST-90 is 30 feet at 100 yards. Why can't the SST-90 spot also be 10' at 100 yards and what will it take to accomplish that?
The science behind lens flashlights? For who has had the subject back then: look up your secondary school ray physics (it is actually 17th century science, not 19th, Galilei and Huygens could have helped you design the best optical design for your flashlight, heck, they could have made quite descent lenses for it!), it will tell you most of what is happening with aspheric flashlight optics (reflector optics is more complicated btw).
There are a few complications because we use such short focal lengths. *The lens must be aspheric instead of spheric to produce a better image, *because the cone of light that the lens catches is so wide there is light loss at the edge because of direct reflection, AR-coating will help a bit.
There's good fortune as well for use in flashlights: the lens does not have to be melles-griott quality, a crap chinese lens does the job almost as well because we do not need a perfect die image, a bit blurry is actually more desired, as long as the lens is not so bad that the light gets all over the place.
In short, theory predicts, and I found this in practice as well, using a fixed emitter size and brightness, hotspot brightness (throw) is lineair with aspheric lens surface area. Given that surface area, a shorter focal length lens (thicker) gives a larger hotspot (more light), a longer focal length (thinner) lens gives a smaller (but not brighter) hotspot. So unfortunately to get more throw optically, the only way is using bigger lenses. What does not help is that to get twice the throw, the lens must be twice the surface area, but will be 4 times as heavy, not counting the increased size and weight of the flashlight housing. You can avoid that heavy lens a bit by using a thinner longer focal length lens, that gives the same throw but with a smaller hotspot with more light loss. (I was pleasantly surprised by the UF- that they did not go for the thinner long focus lens but put a massive chunk of glass in there :-) )
I realise that some (a lot) of this post has already been said but I was called away before I could post it, so it is what it is
The degree’s that are mentioned in the data sheet are for 50% emittence, that is the point (in degree’s) where the output is 50% of the output at 90 degree’s.
Look at the image we have all seen before, if you measure the output through a small hole at 90 degree’s then measured it at the red line the result will be 50% of the output.
So from one red line to the other (125 degree’s) you get most, but not all, of the output.
For an Aspheric lens the lower the degree’s the better, the led is throwing more out front.
Have a play here,
With B = the led (62.5), C = center of lens (90), A = ignore
b = half of lens diameter, a = focal length, c = ignore
In the linked calculator enter 62.5 into “Angle A or B” and half of the diameter of the lens into “Side b” then “calculate”.
The top figure is the focal length for the 125 degree angle, less is better, more not so good.
I hope that lot is understandable :nerd_face:
Cheers David
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