Rifle Scopes Blinded, Randomized scope testing

[db2000]

With all the vastly varying anecdotal reports of IQ between scopes, I think a blinded, randomized controlled trial of scopes would be very interesting. Because there’s some degree of objectivity and methodology in evaluating IQ, I think this could be very revealing.
Bias seems to be one of the greatest influences on individuals as far as I can tell. Whether conscious or subconscious, it can be hard to admit a $600 scope is optically close to a $4k scope.
Just like some people taste soap with cilantro or prefer different flavors than others, I believe vision is the same way. This may be obvious to some folks but it’s definitely not accepted main stream because people continue to argue to the point of insults (myself included ) over IQ of scopes. In contrast, most everyone is in agreement that scope features are subjective, so no need to try and examine that. The test could be standardized to be blinded. It would take some effort but certainly doable. A way to make diopter, magnification and parallax adjustments without fingering the scope. The trial would need to include a professional eye examination and history as well obviously.

 

[RTH1800]

Far more to a scope than glass.

 

[Rob01]

Total waste of time and effort to prove something that will not be proven or agreed upon. Buy the scope you like and use it.

 

[beetroot]

Tactical Scopes: Field Test Results Summary & Overall Scores

This is the executive summary and overall scores from an epic scope field test focused on long-range...

precisionrifleblog.com

10 years old now, but this style of test has been done before, so could be done again.

But as Rob eluded to, would be a lot of effort to go to for little gain.
Anyone who knew enough about scopes to judge optically quality will probably be able to guess the scope based off the reticle, so ot be very hard to do a truely blind test.

 

[Convex]

Used to read reviews about a car I lusted after and how it was so much better if you spent another 10 grand on a performance tune boosting the engine up another 100 hp, and honestly spent a lot of time trying to talk myself into buying the car and springing for the expensive upgrade.

Revisiting the spec on the difference in 0-60 times for the car with/without the expensive upgrade was a difference of 2/10ths of a second, and of course in my old age/retirement the logic "10 grand for 2/10ths of a second, fuck that" won out.


Before I retired and could renew my money quickly blowing that kind of money didn't hurt so bad, but in a way, having to be careful kind of makes you grow up re your purchases.


My wife doesn't have my OCD so she is my conscious and has saved me buying a boatload of gear I didn't really need. Like when I was walking out of Home Depot, and I've already got 6 hand drills (I think) but I start to slow down around the sales stand w/the new drills and "keep going" is whispered softly in my ear.

My wife already knows how many hand drills I got because she uses 'em.

Unless you're rich, sooner or later, you gotta grow up.


Of course even rich guys start to feel real pain when they think they can change out their women every 2 years.

 

[db2000]

Tactical Scopes: Field Test Results Summary & Overall Scores

This is the executive summary and overall scores from an epic scope field test focused on long-range...

precisionrifleblog.com

10 years old now, but this style of test has been done before, so could be done again.

But as Rob eluded to, would be a lot of effort to go to for little gain.
Anyone who knew enough about scopes to judge optically quality will probably be able to guess the scope based off the reticle, so ot be very hard to do a truely blind test.

Good point on the reticle. I guess potentially there’s examiners from other types of optics that potentially would not but who knows.

 

[db2000]

Total waste of time and effort to prove something that will not be proven or agreed upon. Buy the scope you like and use it.

It’s called research. Not trying to “prove” anything. If fact, certainly not trying to organize the experiment either. Just making discussion on a discussion board. Thanks for your opinion.

 

[supercorndogs]

Another problem is going to be the range of IQ in a particular scope. Just because you get two of the same modle doesn't mean they will be the same.

 

[TheHorta]

All these elite glass snobs are afraid of the truth. If that ever happened it would confirm what many of us already know — #Barska-is-Best

 

[db2000]

All these elite glass snobs are afraid of the truth. If that ever happened it would confirm what many of us already know — #Barska-is-Best

Whatever happened to you trading me that HISS for my Super Yoter. You pinky promised

 

[FuhQ]

With all the vastly varying anecdotal reports of IQ between scopes, I think a blinded, randomized controlled trial of scopes would be very interesting. Because there’s some degree of objectivity and methodology in evaluating IQ, I think this could be very revealing.
Bias seems to be one of the greatest influences on individuals as far as I can tell. Whether conscious or subconscious, it can be hard to admit a $600 scope is optically close to a $4k scope.
Just like some people taste soap with cilantro or prefer different flavors than others, I believe vision is the same way. This may be obvious to some folks but it’s definitely not accepted main stream because people continue to argue to the point of insults (myself included ) over IQ of scopes. In contrast, most everyone is in agreement that scope features are subjective, so no need to try and examine that. The test could be standardized to be blinded. It would take some effort but certainly doable. A way to make diopter, magnification and parallax adjustments without fingering the scope. The trial would need to include a professional eye examination and history as well obviously.

So, you want to build a wall with just the very back rubber piece of the objective sticking through, so you can't see anything forward of that... Sort of like a glory hole for scopes? "The Scory Hole"?

 

[FuhQ]

All these elite glass snobs are afraid of the truth. If that ever happened it would confirm what many of us already know — #Barska-is-Best

Fuck that... I'll call your Barska and raise you Quigley-Ford... How much concrete can you work?

 

[hafejd30]

Way more to a scope than simply how it looks through the glass

Personally I’m one that would give up glass for reliability

Then there’s size, reticle, illumination, zoom range etc etc that factor in on which scope is “better” for the user





Plus why waste all that effort when NF ATACR will dominate anyways

 

[koshkin]

Image quality can be objectively measured. All you need to do is pony up some cash for the right equipment and training so that you can measure away. Now, depending on what exactly you want to measure, you are looking at mid-to-high five figures and on up from there for a turnkey test station.

PRB test was a valiant effort that came crashing down because he did not know what he was doing as fa as evaluations go.

ILya

 

[Emerson0311]

The interesting thing about high end tools is that as the skill of the user grows, different features and specific performance attributes rise and fall on the priority list. The folks simping for $600 units over $3K+ units usually do not have a use for the small but significant advantages the top end gear offers. They don’t even understand what those advantages are. The more I build skill and experience with really good tools, the more I become aware of all my errors in skill and use. A basic task only “needs” a basic tool, but high performance users can get a lot more out of a top end tool.

 

[Convex]

Image quality can be objectively measured. All you need to do is pony up some cash for the right equipment and training so that you can measure away. Now, depending on what exactly you want to measure, you are looking at mid-to-high five figures and on up from there for a turnkey test station.

PRB test was a valiant effort that came crashing down because he did not know what he was doing as fa as evaluations go.

ILya

Correct me if I'm wrong but you can blow that on just a collimator alone!?


Again your brain adjusts to however bad your vision becomes. In the month the between surgery for both eyes, I was utterly shocked comparing what I could see with what I previously thought wasn't that bad but could then see how it was almost fog coming thru my left eye after the surgery on my rt.


And to make matters worse, I had a differing amount of astigmatism so I was having more and more trouble setting up my focus (it would be right for my left eye, but out of whack for my rt and so forth).


I'm sure there are folks in the same boat where their vision isn't as good as they think it is, and just for the sake of their vision should get their eyes checked.

I dodged the total blindness that comes w/glaucoma, by finding out I had it, when they couldn't stop it with drugs, they installed stints/little relief valves to lower the pressure and put the glaucoma to sleep in addition to correcting my vision.


It doesn't do any good drinking great champagne thru a dirty glass.

 

[koshkin]

Correct me if I'm wrong but you can blow that on just a collimator alone!?


Again your brain adjusts to however bad your vision becomes. In the month the between surgery for both eyes, I was utterly shocked comparing what I could see with what I previously thought wasn't that bad but could then see how it was almost fog coming thru my left eye after the surgery on my rt.


And to make matters worse, I had a differing amount of astigmatism so I was having more and more trouble setting up my focus (it would be right for my left eye, but out of whack for my rt and so forth).


I'm sure there are folks in the same boat where their vision isn't as good as they think it is, and just for the sake of their vision should get their eyes checked.

I dodged the total blindness that comes w/glaucoma, by finding out I had it, when they couldn't stop it with drugs, they installed stints/little relief valves to lower the pressure and put the glaucoma to sleep in addition to correcting my vision.


It doesn't do any good drinking great champagne thru a dirty glass.

A collimator can be a lot more than that depending on the performance you are looking for. For riflescopes, the collimator is not all that expensive since you do not need very large optics.

ILya

 

[Convex]

Yes... They're very specialized depending on function.

Years ago was looking in a catalog, one of cheapest collimators this outfit sold was 25 grand and up

 

[Taylorbok]

It doesn't do any good drinking great champagne thru a dirty glass.

.... Still gonna get me drunk

 

[Convex]

I guess that'll work, I love it LOL!!!


Long time ago a friend of my who's been a Rollei repair technician (who's already got a collimator he uses for still camera lenses) had been considering branching out into testing cine lenses so he was checking out something along the lines of this and after thinking seriously about it he didn't want to risk the cash outlay and eventually passed.


He felt like it was going to take a boatload of testing those types of optics for him to make his money back on the gear.

https://www.chrosziel.com/lens-testing-instruments-for-service-manufacturing-maintenance/

https://www.chrosziel.com/CamCollimator-CLC-2-platforms/C-LTBMK2-L#top

Actually all of this is in your backyard Koshkin and what you said about using precision test gear along w/the requisite training should be repeated ad nauseum to folks who think they can plop two red dot sights on the countertop at the local gunshop to conduct "tests".

 

[koshkin]

I guess that'll work, I love it LOL!!!


Long time ago a friend of my who's been a Rollei repair technician (who's already got a collimator he uses for still camera lenses) had been considering branching out into testing cine lenses so he was checking out something along the lines of this and after thinking seriously about it he didn't want to risk the cash outlay and eventually passed.


He felt like it was going to take a boatload of testing those types of optics for him to make his money back on the gear.

https://www.chrosziel.com/lens-testing-instruments-for-service-manufacturing-maintenance/

https://www.chrosziel.com/CamCollimator-CLC-2-platforms/C-LTBMK2-L#top

Actually all of this is in your backyard Koshkin.

These are relatively decent systems optimized for vis stuff. Fairly inexpensive by our standards and limited in scope. The software is done pretty well though. For all of these low volume systems, software is usually a bit quirky.

As far as my backyard goes... I live in Albuquerque. Not sure how any of this is anywhere near it.

ILya

 

[Convex]

Not backyard-location

Backyard-expertise


And of course this was going to be all he could afford if he decided to spring for it.

 

[grassassin]

This comes closest to a "blind" test.

 

[grassassin]

I think subjective opinions are important. I also think objective facts are important.

Pasted here is the intro to an article that might help us get beyond squinting through scopes while scratching our heads and muttering opinions about "sharp glass." We don't necessarily need to spend tens of thousands on scientific testing equipment to get there (though it would help).

Attached is the entire text of the article in PDF format if you care to read on. It is long. You've been warned. Here's the introduction:

A Framework for the Scientific and Objective Comparison of Rifle Scopes

April 2025

Ryan Amundson
[email protected]

Introduction: The Challenge and Importance of Objective Rifle Scope Evaluation

The selection of a rifle scope represents a critical decision for shooters engaged in precision-dependent activities, ranging from competitive target shooting and long-range hunting to tactical and military applications. However, navigating the market to compare different models presents significant challenges. Manufacturer claims often emphasize specific features without providing comprehensive performance data, while subjective user reviews, though potentially helpful, lack the rigor and repeatability necessary for definitive comparison. The inherent complexity of optical and mechanical systems further complicates assessment, making it difficult to discern meaningful differences based solely on specifications or anecdotal evidence.
This challenge underscores the critical need for scientific, objective methodologies in evaluating rifle scope performance. For applications where precision, reliability, and consistency are paramount, subjective assessments are insufficient. Objective testing provides verifiable, data-driven insights into a scope's true capabilities and limitations. Interestingly, surveys of experienced long-range shooters have indicated that mechanical performance—the precision and reliability of adjustments and zero retention—is often rated as even more critical than optical performance. This highlights the necessity of moving beyond simple evaluations of image clarity ("sharp glass") to encompass rigorous testing of the entire system.
This report outlines a comprehensive framework for the scientific and objective comparison of rifle scopes. It details the key performance parameters across optical, mechanical, and durability domains, describes the standardized test procedures and specialized instrumentation required for their measurement, and references applicable industry standards (such as ISO and MIL-STD). The goal is to provide a robust methodology that enables rigorous, evidence-based evaluation and comparison, empowering users to make informed decisions based on verifiable performance data rather than marketing claims or subjective opinion.

 

[rothgyr]

I have bad eyes. People go on about how night and day difference going from an ATACR to a ZCO/Tangent was, and I can't see a difference. Being a glasses wearer, I'm so used to aberrations show up on my periphery or the horizon that I just don't care about CA like some people do.

It might be some form of dyslexia or something, but I have a hard time picking out hashes on a reticle if they're too similar. After $2k, it's going to be about features. I'll pass up a Minox/Tangent vs a Razor III because I want lower parallax settings for a .22. I'll keep on using my USO FDN and ATACR 7-35 vs a ZCO because I can read a JVCR and MIL-XT better on the fly than I can with any of ZCO's reticles. I still hit targets.

One of the guys dominating our regional PRS matches is using a Burris XTR3 gen 1 because he likes it. Guy has run ZCO, MK5s, RZR3, XTR Pro, Zeiss, and who knows what else, but he loves his poverty Burris.

After $2k, do marginal differences IQ really matter that much? Depends on the user. My hobby is primarily shooting and building rifles. Others' hobby might be more of collecting high end optics and trying to have the perfect gun?

 

[Taylorbok]

I have bad eyes. People go on about how night and day difference going from an ATACR to a ZCO/Tangent was, and I can't see a difference. Being a glasses wearer, I'm so used to aberrations show up on my periphery or the horizon that I just don't care about CA like some people do.

It might be some form of dyslexia or something, but I have a hard time picking out hashes on a reticle if they're too similar. After $2k, it's going to be about features. I'll pass up a Minox/Tangent vs a Razor III because I want lower parallax settings for a .22. I'll keep on using my USO FDN and ATACR 7-35 vs a ZCO because I can read a JVCR and MIL-XT better on the fly than I can with any of ZCO's reticles. I still hit targets.

One of the guys dominating our regional PRS matches is using a Burris XTR3 gen 1 because he likes it. Guy has run ZCO, MK5s, RZR3, XTR Pro, Zeiss, and who knows what else, but he loves his poverty Burris.

After $2k, do marginal differences IQ really matter that much? Depends on the user. My hobby is primarily shooting and building rifles. Others' hobby might be more of collecting high end optics and trying to have the perfect gun?

Preaching to the choir, I have a stigmatism than can't be corrected, optically I can't tell the difference between my Cronus and my ZCO.

 

[Edsel]

…I think a blinded, randomized controlled trial of scopes would be very interesting. Because there’s some degree of objectivity and methodology in evaluating IQ, I think this could be very revealing.

It would be exceedingly hard to satisfy a true “blind” condition, particularly among shooters already familiar with turret, ocular, illumination, and reticle designs.

The study population itself would be a nightmare to screen.

While studies with pharmaceutical cohorts and interventions are mechanistically quite simple, it’s the threshing out of confounders and dealing with the study population which makes them horribly expensive.

 

[stanley_white]

I have bad eyes. People go on about how night and day difference going from an ATACR to a ZCO/Tangent was, and I can't see a difference. Being a glasses wearer, I'm so used to aberrations show up on my periphery or the horizon that I just don't care about CA like some people do.

It might be some form of dyslexia or something, but I have a hard time picking out hashes on a reticle if they're too similar. After $2k, it's going to be about features. I'll pass up a Minox/Tangent vs a Razor III because I want lower parallax settings for a .22. I'll keep on using my USO FDN and ATACR 7-35 vs a ZCO because I can read a JVCR and MIL-XT better on the fly than I can with any of ZCO's reticles. I still hit targets.

One of the guys dominating our regional PRS matches is using a Burris XTR3 gen 1 because he likes it. Guy has run ZCO, MK5s, RZR3, XTR Pro, Zeiss, and who knows what else, but he loves his poverty Burris.

After $2k, do marginal differences IQ really matter that much? Depends on the user. My hobby is primarily shooting and building rifles. Others' hobby might be more of collecting high end optics and trying to have the perfect gun?

$5k scope with $2k eyes sounds like both my story and a country song that needs to be written.

-Stan

 

[grassassin]

I have bad eyes. People go on about how night and day difference going from an ATACR to a ZCO/Tangent was, and I can't see a difference. Being a glasses wearer, I'm so used to aberrations show up on my periphery or the horizon that I just don't care about CA like some people do.

It might be some form of dyslexia or something, but I have a hard time picking out hashes on a reticle if they're too similar. After $2k, it's going to be about features. I'll pass up a Minox/Tangent vs a Razor III because I want lower parallax settings for a .22. I'll keep on using my USO FDN and ATACR 7-35 vs a ZCO because I can read a JVCR and MIL-XT better on the fly than I can with any of ZCO's reticles. I still hit targets.

One of the guys dominating our regional PRS matches is using a Burris XTR3 gen 1 because he likes it. Guy has run ZCO, MK5s, RZR3, XTR Pro, Zeiss, and who knows what else, but he loves his poverty Burris.

After $2k, do marginal differences IQ really matter that much? Depends on the user. My hobby is primarily shooting and building rifles. Others' hobby might be more of collecting high end optics and trying to have the perfect gun?

Yes, shooting is my hobby, not the tools themselves. Sometimes I forget and it always feels good to be reminded of it.

My eyes are trash. I have a hard time distinguishing the finer points of optical perfection so assuming that I don't feel myself struggling with a demanding eye box, if I can see bullet trace and reasonably read wind via mirage in a scope, that pretty much checks the boxes for me when it comes to the quality of the glass itself. From that point on it is all about a much longer list of considerations having to do with build-quality, reticle design, feature set, etc. Those subjective-dependent considerations are huge. Tracking precision and repeatability, though, is critical and the objective measurement of these fortunately require no expensive equipment to evaluate.

 

[ZCOklahoma]

Learned some of these optical effects over the past weekend. I currently own two ZCO 8-40 and a Burris XTR Pro. I have owned practically everything else, except Tangent over the past few years. I started wearing contacts about a week ago, and I zeroed my ZCO without them. Got the contacts in the night before the match and when I got behind my diopter, I couldn’t see squat. Had to really adjust it.

Put the Burris XTR Pro on my center fire rifle this weekend and thought the eye box was great. ( No contacts)

Took a quick glance this morning WITH contacts and couldn’t see anything and it looked like I was looking through a straw.

I definitely have some things to work on with getting my eyes adjusted instead of blaming my equipment.

I just wonder how all of this affects my parallax on shots. Especially rimfire.

 

[carbonbased]

Learned some of these optical effects over the past weekend. I currently own two ZCO 8-40 and a Burris XTR Pro. I have owned practically everything else, except Tangent over the past few years. I started wearing contacts about a week ago, and I zeroed my ZCO without them. Got the contacts in the night before the match and when I got behind my diopter, I couldn’t see squat. Had to really adjust it.

Put the Burris XTR Pro on my center fire rifle this weekend and thought the eye box was great. ( No contacts)

Took a quick glance this morning WITH contacts and couldn’t see anything and it looked like I was looking through a straw.

I definitely have some things to work on with getting my eyes adjusted instead of blaming my equipment.

I just wonder how all of this affects my parallax on shots. Especially rimfire.

So, did you go from naked eyes to contacts? Or from eyeglasses to contacts?

I definitely have had to readjust the diopter between glasses, contacts, and now nothing (after cataract surgery). But never have had a FOV change…hmmm…

 

[ZCOklahoma]

So, did you go from naked eyes to contacts? Or from eyeglasses to contacts?

I definitely have had to readjust the diopter between glasses, contacts, and now nothing (after cataract surgery). But never have had a FOV change…hmmm…

Naked eye to contacts. My contact prescription has my right eye for seeing up close and my left eye for distance. I asked the eye doctor for this because I couldn’t locate my targets anymore with my naked eye. My eyes are currently trying to determine who will be the dominant eye now. I was left eye dominant before.

 

[carbonbased]

Naked eye to contacts. My contact prescription has my right eye for seeing up close and my left eye for distance. I asked the eye doctor for this because I couldn’t locate my targets anymore with my naked eye. My eyes are currently trying to determine who will be the dominant eye now. I was left eye dominant before.

Do you shoot right or left-handed?

I am right handed and just so happen to have a similar focus setup. Only it’s permanent via new lenses after cataracts, and also opposite from yours. My right eye is set for distance, and the left for closeup.

If you’re looking through your scope with your closeup eye, methinks there will be major issues. My doc told me to go with the distance eye for use with the scope.

I’ll take a gander through my scopes with my closeup eye and report back.

 

[ZCOklahoma]

Are you right or left-handed?

I am right handed and just so happen to have a similar focus setup. Only it’s permanent via new lenses after cataracts, and also opposite from yours. My right eye is set for distance, and the left for closeup.

If you’re looking through your scope with your closeup eye, methinks there will be major issues. My doc told me to go with the distance eye for use with the scope.

I’ll take a gander through my scopes with my closeup eye and report back.

I am right handed and left eye dominant with no correction. I will switch my contacts and give that a try when I get home.

 

[carbonbased]

I am right handed and left eye dominant with no correction. I will switch my contacts and give that a try when I get home.

Cool.

Gah, I just had a wave of “old old man” juju flow over me lol. Here I am talking about “my closeup eye” like it’s a bolt-on car part haha

 

[308pirate]

With all the vastly varying anecdotal reports of IQ between scopes, I think a blinded, randomized controlled trial of scopes would be very interesting. Because there’s some degree of objectivity and methodology in evaluating IQ, I think this could be very revealing.
Bias seems to be one of the greatest influences on individuals as far as I can tell. Whether conscious or subconscious, it can be hard to admit a $600 scope is optically close to a $4k scope.
Just like some people taste soap with cilantro or prefer different flavors than others, I believe vision is the same way. This may be obvious to some folks but it’s definitely not accepted main stream because people continue to argue to the point of insults (myself included ) over IQ of scopes. In contrast, most everyone is in agreement that scope features are subjective, so no need to try and examine that. The test could be standardized to be blinded. It would take some effort but certainly doable. A way to make diopter, magnification and parallax adjustments without fingering the scope. The trial would need to include a professional eye examination and history as well obviously.

This is stupid

 

[diggler1833]

Learned some of these optical effects over the past weekend. I currently own two ZCO 8-40 and a Burris XTR Pro. I have owned practically everything else, except Tangent over the past few years. I started wearing contacts about a week ago, and I zeroed my ZCO without them. Got the contacts in the night before the match and when I got behind my diopter, I couldn’t see squat. Had to really adjust it.

Put the Burris XTR Pro on my center fire rifle this weekend and thought the eye box was great. ( No contacts)

Took a quick glance this morning WITH contacts and couldn’t see anything and it looked like I was looking through a straw.

I definitely have some things to work on with getting my eyes adjusted instead of blaming my equipment.

I just wonder how all of this affects my parallax on shots. Especially rimfire.

I wear glasses (20/50 vision now), but I still take them off and have my diopters set for looking through my optics with my naked eye. I feel your pain, so made the adjustment accordingly to just keep my glasses off when I shoot.

It has bit me before. I killed a really nice buck at 295 yards a few seasons ago... only to get up on him and realize that he was a really nice 2-1/2 year old, and would have been a monster in another two years.

 

[carbonbased]

I am right handed and left eye dominant with no correction. I will switch my contacts and give that a try when I get home.

Ok, so I just tried it. At first I didn’t notice a difference. But after switching eyes back and forth a bunch (and readjusting the diopter each time) I did notice that with the closeup eye there is a fair bit more black periphery around the image circle. Not “looking through a cardboard tube” level, but enough to notice.

I liken it to the effect of adding an ocular cap, which adds more black around the image. Only in this case it seems like the image itself is smaller and “further away”. Could be an illusion, just like the scope cap example is, but it’s there.

I wonder if the effect might increase/decrease the higher up the contact correction is? I’m no optical engineer, for sure.

With the closeup eye, I had to bottom out the diopter setting to just barely get the reticle in focus.

Are you nearsighted, like me?

 

[ZCOklahoma]

Yes sir. I’m nearsighted.

 

[FCrifles]

If one could get all the big boys with no reticles in them and have everything in a line covered up, as area 419 did, plus the tester could adjust parallax for their eyes, then you would have a more non bias outcome, IMO. Anyone that loves the high-end glass, will likely recognize some of the reticles.

 

[carbonbased]

I am right handed and left eye dominant with no correction. I will switch my contacts and give that a try when I get home.

Not sure if you know this, but there’s no guarantee that the swapped contacts will fit. Sometimes it’s like having two feet that are different sizes, only here it’s cornea shapes. It’ll probably work ok, though.

The other issue is if both naked eyes have close RX corrections. If they don’t, you’ll notice when you swap! No harm done trying, however.

There can be other left/right contact differences depending on the contact and prescription, like toric lenses for astigmatism, but I’m guessing that is not the case here.