Topography scans possible with deep set eyes?

[russell s]

Hi all,

Having suffered moderate Keratoconus in my left eye for around 30 years (I'm 45) for which I wear a contact lens, fortunately my right eye has remained stable with only mild KC and has required no glasses/contact lenses. However, over the last 2-3 months the vision in my right eye has deteriorated and I'm now experiencing blurred sight and pronounced ghosting. Funny thing is, unlike my left eye, the symptoms in my right eye vary slightly on daily bases and in my opinion are the result of something happening to my eye over night during sleep.

A specialist at my local NHS hospital initially gave the back of my right eye a thorough investigation, ruling out any glaucoma or macular issues and booked me in for a topography scan of both eyes.

Having waited nearly (2) months for this test I was disappointed today to find that the eyepiece on the scanning machine would not marry up to my eyes and allow a scan to be made. Apparently my eyes are too 'deep set' (or I have too prominent eyebrow bones) for the machine. Slightly concerning given topography scans appear to be a key diagnostic tool fo Keratoconus!

So I'm wondering if this is typical or if there are any scanning machines capable of scanning 'deep set' eyes? Should I just accept that scans are not a possible?

Many thanks,

Russ

[Andrew MacLean]

Russ

I've never heard of that before. To be honest, I don't really know what to make of it.

Welcome to the forum, just the same.

Andrew

ps maybe one of our professional optometrists can shed some light?

[NickDash]

Russ

Sorry to hear that the NHS is again not offering the basic level of care needed for KC. Either this is a limit of the equipment or limit of the skill of the technician that has tried to acquire the topographies. Either way you should potentially try a private clinic which specialises in Keratoconus.

Deep recessed eyes should not preclude accurate measurements and certainly not with the latest equipment.
Without Topographies the condition can not be monitored accurately and certainly consideration of treatment plans such as Corneal Cross Linking and TCAT Cross Linking require this data.

Nick Dash
Optometrist

[longhoc]

Hi Russ

As Andrew said, an optometrist who uses this sort of equipmnet day in, day out, will be the best source of accurate information... Nick has offered his suggestion that you might not have had the scan done correctly. I looked at the marketing blurb for the Oculus Pentacam (the most widely used device for this sort of scan) http://www.pentacam.com/sites/technische_daten.php and their measuring distance is stated as being 80mm. Now, allowing for a bit of tolerance, this means that you'd need less than c. 70mm between the eye surface and the end of your forehead. It's quite a pronounced forehead which would have greater than this sort of depth ! Does that sound in the range for you ?

I've certainly experienced -- how shall I put this charitably ? -- perhaps less than greatly experienced operators of this equipment in the NHS. Often, only through countless times of having the thing done, I know more than they do. Have had instances where the operator doesn't make any serious attempt to adjust the seating height or the chin rest. As you have to hold position without blinking for about 15~20 seconds, if you're having to maintain an uncomfortable angle then you could easily have moved and/or blinked and the scan wouldn't have completed. Another possibility is that there's some clinics which are using really quite old models. These can't capture anything more than moderate keratoconus. So that's another reason (and the person using the scanner misrepresented what happened in reality).

What did your gut instinct tell you about the clinic you attended ? Did they seem well organised, knowledgable and helpful ? Did they appear to have the time to go through things with you and explain what was being done and why ? Were the staff focussed on the patient or did they give the impression of being distracted by other things e.g. record keeping etc. ? Was the staff/patient ratio sufficient or did you feel like you were on the meat rack ? I've learnt that, in the absence of any medical skills or training to look beyond the immediate situation and try and get a hunch about what sort of treatment I'm likely to get. As others have said, there's definitely good and bad out there. If the answer is tending towards the not-so-good, let us know and we can make some suggestions about what to do next.

Best wishes

Chris

[Accuvision Optom]

Hi Russ,

Welcome to the forum.

Please don't worry about having "deep set eyes"! It is something we encounter routinely.
Acquiring good topographic data can be a little more tricky but can be achieved by an experienced user.

I would like to point out that the "operating distance" quoted as 80mm by Chris for the Pentacam, is actually the distance from the machine to the patient. It does not relate to any anatomical dimensions as suggested.

Don't give up,

Anthony

[longhoc]

Many thanks for putting me right Anthony. We'd be a bit lost without the contributions from professionals who volunteer their time to post here. It's really appreciated.

Cheers

Chris

[russell s]

Firstly apologies for not replying sooner, but I have not had PC access for the last week or so.

Secondly a big thanks for all the responses and welcome extended here.

Chris, in answer to question re. the type of clinic I attend, it's at a medium size NHS hospital where I have been treated by their consultant optometrist for the last 10 years. Prior to that, following my initial diagnosis at the age of 22 at the same hospiatl, I visited the same optometrist privately. Over this total period, 23 years, I have only seen an eye specialist on two occasions and have had two attempted topography scans both dismissed as academic.

Whilst I would say I have been happy with my optomerist, the lack of KC knowledge at the hospital is obvious; its a busy clinic where the majority of patients are being treated for glaucoma, cataract and macular problems. Undoubtedly this is where the hospital's strength lies with KC certainly on the periphery of things - I was very disappointed with how readily they dismissed the scans!

When I was first diagnosed in 1988, (moderate KC in my right eye, mild in my left) I was fitted with a single GP lens. I struggled with the comfort of this lens for a number years and 90% of the time never wore it; the strength of my right eye got me by. Around 10 years ago, I was refereed back to the NHS where a Kerasoft No.2 lens was fitted. This has worked ok for the last 11 years, but it's performance varies throughout the day and it does little to improve ghosting. About a year ago my optometrist tried to fit me with an Kerasoft IC lens unsuccessfully.

As mentioned in my previous post, I've now suffered a marked deterioration in my other (right) eye and the condition is having a much greater affect on my life/work. I now feel it's time to seek better treatment outside the NHS and going by what I have read here it sounds like I need to find a private clinic/optometrist who know the condition well, has the appropriate diagnostic equipment and is au fait with the latest lenses/treatments.

So, could somebody please recommend a private clinic/optometrist fairly local to me? I live in Iver Heath, Bucks which is about 5 miles north west of Heathrow Airport.

In the meantime I plan to drop Anne Klepacz an email requesting an information pack.

Thanks again for the warm welcome,

Russ

[longhoc]

Hi Russell

Have sent a message with my own particular thoughts on that one, I'm sure others too can offer the benefit of their experiences.

As I said in the message, anything you need to know, don't hestiate to ask.

Good luck !

Cheers

Chris

[Ali Akay]

Hi Russell and others

In defence of the NHS clinic you attended, I need to say that, if they are using Medmont topographer, it can be extremely difficult to get measurements with very deep set eyes with this instrument. Most topographers work by projecting a target consisting of concentric rings onto your cornea, and analying the image reflected back from the corneal surface. This target is usually fairly large and flat, but, Medmont uses concentric rings in a small conical "funnel". This usually works very well, and overcomes the problems caused with other instruments with the patient's nose getting in the way. However, it can be difficult to get the target close enough to the eye to get a measurement if patient has very deep set eyes. I've really struggled on one or two occasions, and I'd like to think that I am experienced in using these machines! It may be that the problem you had was due to inexperienced operator, but, I'd like to suggest you give them the benefit of the doubt in case they use a Medmont machine and you do indeed have very deep set eyes. It is otherwise a beautiful instrument, and a dream to use compared to Pentacam and most other topographers. In different hospitals I work I've used Pentacam, Topcon, Nidek and Medmont instruments, and, despite the general assumption that Pentacam is the best, it does, not infrequently, produce some very dodgy results, and my favourite definitely is the Medmont. The main benefit of Pentacam is that it measures corneal thickness which can be very useful, but accuracy somewhat doubtful.

With regards to how useful topography actually is in management of KC, there's no doubt its a useful tool, but, if a patient is wearing rigid lenses the measurement would be affected by moulding effect of the lens unless the lens has been left off for a few days prior to the test which is often not practical. I feel one has to be careful not to judge the quality of care provided simply from the frequency of topography scans carried out. Unfortunately, long waiting lists, over-booked hospital clinics, and funding constraints are making it increasingly more difficult for many NHS clinics to provide a gold-standard service, and patients who want the best are increasingly having to turn to the private sector especially if they want to explore the latest treatment options.