Eye to Eye: bridging the gap

May 5, 2025 Staff reporters

In a new occasional series, we cover insights from online Q&As, where ophthalmologists field burning questions from optometrists around the country. We kick the series off with Drew Jones’ pick of responses from Drs Adam Watson (Eye Institute Auckland) and Shira Sheen (Eye Institute Hawke’s Bay) on topics ranging from ptosis and cataracts to keratoconus and blepharoplasty. Answers have been abridged.

What information is helpful in cataract surgery referrals? 

 

Dr Shira Sheen (SS): Optometrists usually know the patient well and have a lot of information that we can benefit from. That includes details of whether they are outdoorsy and active, do they spend time in front of a computer, do they read a lot, what’s their dominancy, amblyopia, best corrected unaided vision, do they wear contact lenses, prefer monofocal or multifocal, read without glasses? One very important thing is if the patient has prisms in their glasses. I had a bad experience not knowing that before surgery with a premium lens. She finished up with good vision, but it was double vision! She ended up having premium lenses but with glasses with a prism. I'm not against that, but when people spend money on premium lenses, they expect to get rid of their glasses. So you can start the discussion about premium lenses before the patient comes to us. 

 

Dr Adam Watson (AW): I always want to know if there is a suspicion of amblyopia. If someone has cataracts and they’re 6/12 in each eye, it's pretty hard to say whether they might have been amblyopic. So, if we know 10–15 years ago this person didn't have cataracts but they only had best corrected vision of 6/9 in one eye, then the likelihood of them benefiting from an extended depth of focus or a trifocal lens is much smaller, so you'd probably have a different conversation with that patient. Referring optometrists should ask patients about their expectations and desires after cataract surgery. It’s helpful for us to know if they would love to be able to read a newspaper without glasses or are they interested in having terrific distance vision for some reason? 

SS: Especially if they are short sighted and they expect they still will be after surgery. I tell them it’s like restarting the computer – whatever you had before, it's gone!

 
AW: It’s very hard for a mild myope to understand that, potentially, they're not going to have mild myopia anymore!

 
SS: The patient’s personality is also an important factor. The optometrist knows how many times they’ve brought back their glasses or contacts because whatever you fit them with, they’re unhappy. If you’re referring such a patient, please tell us. With, for example, multifocal lenses, it can take up to a year to adapt, so at first they might be unhappy because the result is not what they expected. 

 

Can upper-eyelid ptosis worsen after cataract surgery?

 
AW: For someone who has a bit of ptosis, surgery may worsen it. And someone who doesn't have a ptosis may occasionally have one after surgery. It’s thought that eyelid speculums during surgery may have enough impact on the eyelid tissues to cause a bit of droopiness. The standard age-related ptosis is caused by a weakening of the tissue between the levator muscle that lifts the eyelid; if you have anything pulling on or interfering with that tissue, it could make it worse. It's not common, but it can happen.

 
SS: It's more challenging when the eyes are small and deep-set. So have the second eye done and, if there is ptosis there too, then we're even! A colleague did a study about whether to treat cataract or ptosis first. They checked the corneal astigmatism and how the topography is affected by ptosis and found there is an effect. So, if you are considering having a toric lens implanted, fix the ptosis first because otherwise you will fix the surface of the cornea, but not take into account the effect of the eyelid, which is pulling to the side and creating astigmatism post-op.
 
AW: The thing that’s going to make the most difference to a patient is having the cataract done, so I often do that first. 

 

What are the criteria for crosslinking being indicated?
 
AW: Of the two indications for crosslinking, the obvious one is worsening keratoconus. Crosslinking is effective at stabilising keratoconus; in about 50% of cases there may be a little bit of corneal flattening or regularisation as well. Quite commonly you get a little bit of improvement in vision, but the main purpose of crosslinking is to stop keratoconus getting worse. If there is demonstrated progression of keratoconus beyond the noise of your topography device – there's always a little bit of variability, even if you do it twice on the same day – which may be 0.5D or a convincing keratometry (Ks) increase of maybe a dioptre, that's an indication for doing crosslinking. The other indication is keratoconus in a person younger than 18 years, because the likelihood of progression is very high. Waiting for progression in a young person is not necessary or desirable because often the progression can happen quite quickly.
 
SS: Would you take refraction into account?
 
AW: Refraction is often difficult in keratoconus because it's subjective and in doing a subjective refraction on someone with keratoconus, you’ll often get a variety of refractions depending on who's doing it, plus variabilities on the day. So refraction is important, if you go from, say, a dioptre of cyl to having 2.5D of cyl, but even then it does depend on what people's endpoints are for refraction. With the variability in keratoconus, refraction is a softer indicator.
 
SS: Would you recommend the optometrist to refer to an eye specialist for assessment if there is progression like that?

 
AW: If an optometrist sees a patient and thinks they have keratoconus – if they haven't got a topographer, they can use other clinical signs – they might advise the patient to come back in a year. When they return, they might find a bit more cyl, so they think there's progression. But when they're subsequently referred to an ophthalmologist who does topography, all they've got is that little snapshot in time. So they don't know if it’s progression and they have to ask the patient to come back in six to nine months to do another topography. If you think a patient probably has keratoconus, they should have topography because that is the gold standard in creating a baseline. 

 

What is the risk of infectious keratitis following crosslinking?
 
AW: Crosslinking is pretty similar to having surface laser, so you're removing the epithelium in most cases then doing the crosslinking. Then you’d usually put a contact lens on for a period of time, plus antibiotic and anti-inflammatory drops. With photorefractive keratectomy the risk of infection is probably about 1 in 2,000. The evidence base suggests crosslinking’s keratitis risk is probably somewhere between 1 in 500 and 1 in 1,000. So it's important to alert patients to the risk of infection, which can cause scarring and worse vision. But, on balance, it is an extremely beneficial procedure for keratoconus. 

 

Can crosslinking be repeated?
 
AW: Yes. The likelihood of progression of keratoconus, despite having crosslinking, is about 3–4%. Patients can also sabotage crosslinking if they're aggressive eye rubbers. For the eye that's been crosslinked, it takes about four weeks to recover normal vision, but for topographic stability, wait at least three months before prescribing someone glasses. There is a tendency for flattening, possibly even after one to two years, but I wouldn't let that put you off prescribing glasses after three to six months. 

 

Can someone with keratoconus be a pilot? 

 
AW: Having keratoconus is not a blanket ‘no’ to being a commercial pilot. If they have stable mild keratoconus, they can still be a commercial pilot, although they do need regular examinations and confirmation of their stability. I have two patients who have keratoconus and who are commercial pilots. They have good corrected vision and they are maintaining their licence with no particular problems, as long as they're seen on a yearly basis.
 
SS: If they cannot achieve 6/6 vision, they may not be accepted as pilots. For suitable candidates, refractive procedures such as LASIK or other laser surgeries may help meet the required visual standard. However, LASIK is generally not recommended in keratoconus.

 

Can you crosslink pellucid cases?
 
AW: Yes. Pellucid is probably best thought of as being a variant or subtype of keratoconus and it’s often over-diagnosed. Often we'll look at a topography and see that sort of ‘droopy crab claw’ and it's very tempting to think it’s pellucid. But pellucid actually needs to involve thinning of the inferior cornea, too. 

 

How long do contact-lens-wearing patients need to have lenses out of their eyes before assessment and doing biometry?
 
SS: At least three weeks if it's hard contact lenses and maybe two weeks if it's a daily soft lens.
 
AW: Shira is probably more conservative than I am for soft contact lenses. If the patient said they’d had their lenses out for 24 hours, I'd probably be happy with that. For hard lenses, though, because they cause corneal moulding, I was given the advice that for each year of hard contact lens wear you need to have a one-week holiday from them. So for 30 years of hard lens wear, that's 30 weeks without them. 
 

SS: So they’d better come in when they are 15!

AW: But in most cases we come back to roughly three months. If you want to be very careful about it, then the answer would be: when the cornea stops changing, which requires a topographic measurement every four to six weeks.
 
SS: Sometimes it's a long process because they cannot function without contact lenses for so long, so they do one eye without a lens, then the other.

AW: It’s quite common for the referring optometrist to put them in soft lenses temporarily, which gives the cornea a chance to relax and get back to its native shape. Shira, how about if you get a patient who has moderate keratoconus and they wear hard lenses and need cataract surgery?
 
SS: I’ve never had the case like that, but I would try and shorten the time they need to suffer without being able to see properly and do the topography to assess if the cornea hasn't changed any more. Then I would probably proceed.
 
AW: I would too and make a judgement about whether it was likely they are still going to need hard contact lenses after surgery. You can tell just from what the topography and a subjective refraction shows. But most of the time, that patient's going to end up in hard contacts, so I would tend to proceed without doing the wash-out time because it's probably not that helpful. I’ll aim for a mildly myopic outcome, because I find it tends to give them the best compromise for their vision. 

 

For patients with dermatochalasis who need blepharoplasty, is it preferable for the optometrist to carry out the C76 visual field test, as medical insurance often requires? 

 
AW: You’d think that sounds like a pretty good idea, but maybe you should leave it to us because when people do visual fields, there’s always the tendency for the patient to open their eyes really wide to ‘do their best’. But they have to relax their eyebrows; it can be helpful to put a piece of sticky tape across their forehead so it reminds them not to do that. If a patient came in with a C76 visual field that suggested they weren’t eligible, I’d end up repeating it just to make sure.

 

Does cost dictate how you approach surgery?
 
AW: I ask myself how I would advise a family member and let that guide me. I’ll often say to a patient, if we set aside cost, this is what I would recommend.
 
SS: I used to not mention things like premium lenses to public patients until I had one patient who was very upset. He told me it was my job to tell him what is available and it’s his decision what to do with his money. So that’s important for optometrists, too, because it's about the trust patients have in you. I’ve had several public patients who didn’t know about the lenses that are only available privately, which could have reduced their dependency on glasses. They were upset the optometrist didn’t tell them about those because they waited seven months just to see me.
 
AW: We should try not to make decisions for people. We shouldn't assume too much, so having those conversations is not just necessary but also desirable. 

 

How do you determine whether a pterygium surgery should be done prior to cataract surgery?  

SS: If the pterygium is big and affecting the corneal surface and creating astigmatism, it’s smart to remove it before surgery to try and create an even surface before proceeding to cataract surgery.   

AW: Then let the cornea heal for a minimum of three months. I look to see whether it looks active – if it's red and inflamed and you think it's going to get worse, then I'd probably think about doing the pterygium first.  

 

How long after pterygium removal can you perform reliable Ks or biometry prior to cataract removal?  

 

SS: It’s the time it takes the cornea to recover, which is around three to six months. So if you wanted to proceed to cataract surgery after three months, I would check corneal topography at two-week intervals to see that it's stable. If it seems a patient is likely to need cataract surgery and their vision is starting to deteriorate, I suggest initiating referral for pterygium surgery, so by the time they get to the point where they cannot drive or they are anxious to have the surgery done, the cornea will be ready.  
  

Who is suitable for kerarings?

 
AW: Kerarings are little semi-circular implants that change the cornea’s shape. They are suitable for people with moderate keratoconus – not those with mild disease who can get really good glasses correction, or severe keratoconus cases that really need a corneal transplant. It’s patients in the middle who have got a diopter value up to about 54D who have gone beyond the point where they can wear glasses and get a good correction and they have to look at wearing RGP contact lenses. But perhaps they've tried RGPs and they're not comfortable, they won't tolerate them or they just won't wear them. These patients are in the zone for kerarings, which restore them to a point where they're not dependent on RGPs, they can wear glasses and get pretty good, functional vision. 

 

Is there ever a role for small photorefractive keratectomy (PRK) treatments with crosslinking?  

 

AW: With mild keratoconus, particularly, it is accepted that, combined with crosslinking, doing a little bit of surface laser is a pretty safe procedure. Dr John Kanellopoulos in Greece developed the Athens Protocol, which is not so much a refractive treatment, but usually treating more moderate keratoconus to try and restore some corneal regularity. John and other practitioners around the world have established that combining crosslinking with a conservative surface laser treatment is a safe and stable procedure, which is very unlikely to lead to further progression. So as long as the patient understands what the issues are and the potential for progression, that's a reasonable thing to do.    

 

Is there a maximum amount of refractive cylinder that be can be corrected with LASIK versus SMILE?

  

AW: There are accepted upper limits for laser vision correction with both techniques – around 6D of cyl. You could potentially correct more, but the likelihood of getting an accurate outcome diminishes quite quickly when you're toward those generally accepted limits.  Whether SMILE is as good as LASIK in correcting refractive cylinder depends on the technique you’re using to control your astigmatism axis. One of the problems with SMILE was that there wasn’t a great way to control the axis other than marking the cylinder axis then manually rotating the eye just before you do the treatment – not the easiest way to get an accurate outcome. But there are now machines that automate that process.  

 

Can you repeat SMILE treatment?  
  
AW: No. SMILE involves femtosecond laser but instead of creating a flap on the top, like you do with LASIK, and popping the flap back down, it creates a wafer of tissue within the cornea, called a refractive lenticule, and it also creates a little incision. So we reach in there and pull out that refractive lenticule. So you can't do SMILE again because you could end up with inaccuracies and slivers of tissue that cause issues; so you can do PRK, or even LASIK in some cases, if you need to do a retreatment. It works very well, but obviously it takes a little longer to recover vision.   

 

Is there ever a role for small photorefractive keratectomy (PRK) treatments with crosslinking? 

 

AW: With mild keratoconus, particularly, it is accepted that, combined with crosslinking, doing a little bit of surface laser is a pretty safe procedure. Dr John Kanellopoulos in Greece developed the Athens Protocol, which is not so much a refractive treatment but usually treating more moderate keratoconus to try and restore some corneal regularity. John and other practitioners around the world have established that combining crosslinking with a conservative surface laser treatment is a safe and stable procedure, which is very unlikely to lead to further progression. So as long as the patient understands what the issues are and the potential for progression, that’s a reasonable thing to do.