Handheld tonometer

[ophtho wannabe]

I am in a relatively small (two MDs) opthalmology practice. Our tonopen recently died, and we are now looking to replace it. Could anyone comment on their experience with the other handheld devices such as Accupen or Diaton? Thanks

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[orbitsurgMD]

I am in a relatively small (two MDs) opthalmology practice. Our tonopen recently died, and we are now looking to replace it. Could anyone comment on their experience with the other handheld devices such as Accupen or Diaton? Thanks

You might also include the ICare device and the venerable Perkins tonometer.

Accupen is priced the same as a traditional Tonopen, once you finish the obligatory pricing Kabuki with Reichert. The last time I priced out the Diaton, it wasn't much cheaper. Of course, no covers and no anesthetic. The only studies showing reasonable reliability compared to the Goldmann were very small.

The Icare is around $4000 and uses a proprietary disposable tip. So it is expensive. No anesthetic needed despite the contact. I know of only one person using one but none of the details of whether it is as reliable as Goldmann.

I have used the Perkins. I always found the results to be lower than Goldmann pressures, small sample size, though.

Were you dissatisfied enough not to want to repair your Tonopen?

 

[ophtho wannabe]

Thanks for the response. I am only familiar with the tonopen as that is what we used during my training so it is nice to here about other choices. I haven't looked into the cost of repairing the old tonopen yet. Our techs estimate it is 8-10 years old (not sure how reliable that is) so I'm not sure how much more life we can expect from it even after a repair.

 

[orbitsurgMD]

Thanks for the response. I am only familiar with the tonopen as that is what we used during my training so it is nice to here about other choices. I haven't looked into the cost of repairing the old tonopen yet. Our techs estimate it is 8-10 years old (not sure how reliable that is) so I'm not sure how much more life we can expect from it even after a repair.

If it is 8-10 years old, it would either be a Reichert or more likely a Medtronic unit (tonopens have been made by Reichert, Medtronic, Mentor, Bio-Rad and Oculab over the years). They are repairable, and lots of the older ones are still around. When you think about it there isn't much that you can't repair or replace on them. The contact parts are stainless steel, they might get dirty but they rarely wear out. Everything else, including the cases, displays and boards ought to be replaceable.

The new ones (not the Avia) are perennially selling for $2900 with a "discount".

 

[Visionary]

The contact parts are stainless steel, they might get dirty but they rarely wear out.

Might also want to make sure it's not just this. I don't know what problems you're having, specifically, but sometimes just cleaning the contact is enough to fix a malfunctioning tonometer.

 

[DevelopAll]

I am in a relatively small (two MDs) opthalmology practice. Our tonopen recently died, and we are now looking to replace it. Could anyone comment on their experience with the other handheld devices such as Accupen or Diaton? Thanks

.Since I'm familiar with Diaton I wanted to elaborate on its use options that can be helpful for your practice:
Yes Diaton is handheld and portable, but more importantly it is Non-Corneal. In other words, the readings that you get with Diaton are independent of biometric properties of the cornea, unlike Goldmann and all others which are affected by CCT and other corneal parameters and corneal diseases. .
.Diaton is useful as an accurate screening tool, and where corneal methods are not reliable (corneal edema, post lasik, corneal irregularities, etc). It takes readings over the upper eyelid, at the tarsus and over the sclera..
. .
.Also, unlike the other handhelds Diaton doesn’t required you to purchase consumables or require maintenance. Taking into account its already lower price (compared to new tonopens) and no need to make future purchases for it, Diaton can really cut costs for a relatively small practice..
. .
.Hope this helps..
. .

 

[orbitsurgMD]

.Since I'm familiar with Diaton I wanted to elaborate on its use options that can be helpful for your practice:
Yes Diaton is handheld and portable, but more importantly it is Non-Corneal. In other words, the readings that you get with Diaton are independent of biometric properties of the cornea, unlike Goldmann and all others which are affected by CCT and other corneal parameters and corneal diseases. .
.Diaton is useful as an accurate screening tool, and where corneal methods are not reliable (corneal edema, post lasik, corneal irregularities, etc). It takes readings over the upper eyelid, at the tarsus and over the sclera..
. .
.Also, unlike the other handhelds Diaton doesn’t required you to purchase consumables or require maintenance. Taking into account its already lower price (compared to new tonopens) and no need to make future purchases for it, Diaton can really cut costs for a relatively small practice..
. .
.Hope this helps..
. .

[Bolds mine]

That may be true, but you beg the question whether it is also independent of the thickness of the eyelid skin, the presence (or absence) of steatoblepharon, the relative thickness of levator tendon and muscle and any other subdermal tissues and the very real variations in the thickness of the tarsus. At least with corneal applanation devices, there are nomograms based on reliable study data to compensate for CCT. Is there any such comparable data on non-corneal devices like the Diaton? (Has there even been a published comparison comparing readings taken on a conjunctival versus transdermal contact with this device?)

 

[OphthoRU]

I used to think Diaton is only a screening tool. It's not to be used like the main tono-instrument.
By the way, how much does it cost?

 

[DevelopAll]

[Bolds mine]

That may be true, but you beg the question whether it is also independent of the thickness of the eyelid skin, the presence (or absence) of steatoblepharon, the relative thickness of levator tendon and muscle and any other subdermal tissues and the very real variations in the thickness of the tarsus. At least with corneal applanation devices, there are nomograms based on reliable study data to compensate for CCT. Is there any such comparable data on non-corneal devices like the Diaton? (Has there even been a published comparison comparing readings taken on a conjunctival versus transdermal contact with this device?)

You're right, there are a number of contraindications for Diaton such as blephritis and a scared lid which will affect the reading, but you'll need to weight how many cases you have with lid issues vs. corneal issues/irregularities...etc,. Just a great example where Diaton was successfully used on keratoprosthesis patients at MEEI, digits/an estimate was another alternative... There are many goldmann/tonopen/pascal comparisons with diaton... see an article with references from Ophth Times: http://www.oteurope.com/ophthalmolo...riendly/ArticleStandard/Article/detail/647697

Here is one of the clinical studies you've asked by Dr. Henry Perry - corneal and refractive surgeon - http://www.ocli.net/physicians/ocli-perry-old.htm

Comparison of Accuracy of Diaton Transpalpebral Tonometer Versus Goldmann Applanation Tonometer, Dynamic Contour Tonometer and Ocular Response Analyzer

PURPOSE: To compare intraocular pressure measurements obtained with the diaton transpalpebral tonometer with those from ocular response analyzer (ORA), dynamic (should be in same order as title)contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in patients diagnosed with primary open-angle glaucoma (POAG) and glaucoma suspects, and to determine the effects of central corneal thickness (CCT)
and corneal hysteresis (CH) on intraocular pressure (IOP) measurements with these devices.

METHODS: 40 patients (80 eyes) age 42-83 years with POAG and glaucoma suspects were included in the study. The average of ORA (corneal compensated IOP [IOP-ORAcc] and Goldmann-correlated IOP [IOP-ORAg]), DCT, GAT, and Diaton tonometer levels were compared and the devices were examined with respect to CCT and CH.
Spearman's correlation tests were used for statistical analysis.

RESULTS: Mean CCT was 561,2±32,4mum and mean CH was 10.6+/-2.0 mmHg. Mean IOP obtained using DCT was 18,9±4,1 mmHg, whereas those provided by ORA were 18,2±3,4 mmHg for IOP-ORAcc and 18,4±3,5 mmHg for IOP-ORAg. The mean IOP obtained using GAT and Diaton were 18,4±4,1 mmHg and 17,0±3,0 mmHg respectively.
The performed analysis of correlation between IOP meanings shows high conformity of results of Diaton with IOP-ORAcc and DCT. The differences between the measurements of DCT, ORA and Diaton were statistically significant. Correlated rates relations: between IOP-ORAcc and DCT 0,89; between IOP-ORAcc and Diaton 0,96; IOP-ORAcc and GAT 0,56; between GAT and Diaton 0,61; GAT and DCT 0,73; DCT and Diaton 0,87.

CONCLUSIONS: Transpalpebral Tonometry is an accurate method of IOP
measurement that is also independent from the biomechanical characteristics of cornea.
It can be recommended for IOP measurements of patients diagnosed with glaucoma including those cases where cornea pathology or cornea characteristics have been altered.

______

As you see CCT in this case study affects corneal tonometers greater vs. non-corneal diaton.

Need to run for now....I hope this helps

 

[OphthoRU]

in this turkish study they concluded:
The Diaton measurements show moderate correlation with those provided by applanation tonometry. The Diaton tonometer seems to be more affected by the corneal thickness, especially in the thinnest corneas.

i wonder, how.)

also, this chineese conclusion looks nice to me:
We cannot recommend Diaton as a substitute or alternative method for GAT for diagnosis and follow-up of patients with abnormal IOPs, but it may be helpful as a screening tool, especially for subjects whose age is between 20 and 50 years and for healthy subjects.

 

[DevelopAll]

Regarding the study from Turkey you've posted, I saw you added a smiley face, I agree their conclusions are simply impossible, since IOP with Diaton is taken over the tarsus and sclera (NOT CORNEA) - how can cornea have ANY effect? Unfortunately I see too many researchers without proper knowledge/training use the devices and start doing studies and come up with broad, confusing to others results. I personally use Diaton and it correlates very well with GAT within 1mm or so, specially if patients have normal corneas, if the cornea is distorted one way or another, either due to cct, scar, GAT result has to be adjusted, where Diaton gives results independent of corneal factors....ex: if one has thinner cornea, I trust Diaton more since it does give a much better (higher) result, taking cornea out of the picture as well as other biomechanics of the cornea.

Read this article from Review of Ophth:
Measuring IOP: The Cornea Factor

Leon Herndon, MD, Durham, N.C.

The relevance of central corneal thickness to glaucoma diagnosis isn't a new idea. It was first discussed 25 or 30 years ago, al*though it wasn't widely covered in American journals until about 10 years ago. However, the nuances of the relationship between glaucoma and CCT continue to unfold, both in terms of IOP and possible connections between CCT and anatomical features such as nerve fiber layer thickness.

The Biomechanics Factor
The most eye-opening development in the past few years has been the revelation that corneal biomechanics—the physical characteristics of corneal tissue—may affect the accuracy of intraocular pressure applanation measurement as much as, or more than, CCT. Much of the key work in this area has been done by Cynthia Roberts, PhD, a biomedical engineer at Ohio State University.1
Goldmann applanation tonometry measures IOP by flattening the cornea, which is not neutral in this measurement. Dr. Roberts has shown that factors affecting corneal resistance include structural considerations, such as the amount of rigidity produced by the way the collagen beams in the tissue line up. The "bendability" of corneal tissue can also be affected by short-term factors such as the presence of cor*neal edema.


read in full here: http://www.revophth.com/content/d/glaucoma_management/i/1303/c/25083/

Hope this helps.

 

[DevelopAll]

Here are a couple more studies of Diaton after surgeries + vs GAT Tonopen...etc.,:

1. Clinical use of transpalpebral diaton tonometry after keratophotorefractive surgeries

T. Dzhafarli MD., A. Illarionova MD.

Purpose: The purpose of the study is to evaluate the clinical use of transpalpebral scleral tonometry, reliability of its application in patients with refraction anomaly in pre- and postoperational periods, dynamics of eye morphometric rates (pachymetry of the central corneal zone, IOP) and their correlative bond before and after photorefractive surgery.

Setting: Russian State Medical University, Moscow, Russia.

Methods: The following factors were exclusion criteria from the study: cornea, upper eyelid and clera pathology. We have analyzed the results of prospective comparative case series clinical study in 98 patients (194 eyes) with ametropia, from which 39 persons (76 eyes), who had been subjected to excimerlaser vision correction. All patients were subject to the comlete refractive examination, including keratotopography, wavefront-aberrometry, US-biomicroscopy,pachymetry corneal thickness in central zone, IOP was measured with Goldman applanation tonometer, pneumotonometer and transpalpebral scleral Diaton tonometer using traditional methodology.

Results: In the patients who had not been subjected to photorefractive surgery the mean applanation IOP was 16.1±2.6 mmHg, the mean IOP evaluated with Diaton 14.7±2.5 mmHg. At that correlation between values of the applanation tonometer and Diaton was highly reliable r=0.73. The mean of the real IOP after applanation value conversion was 15.4±2.4 mmHg. Pearson correlation coefficient between real IOP and the Diaton result was 0.89. In the groups of patients, who underwent photorefractive vision correction, the mean applanation IOP 12.4±2.91 mmHg, modified taking into account keratometry IOP rates 13.9±3.0 mmHg, mean diaton-tonometry result 15.1±2.75 mm Hg - increase of correlation coefficient from 0.51 to 0.81.

Conclusions: The cornea thickness is an important factor in IOP evaluation and monitoring, and necessitates the inclusion of corneal pachymetry in the program of examination the patients with suspicion of glaucoma and hypertension, especially after various keratorefractive surgeries while using the traditional corneal methods of ophthalmotonometry. At the same time clinical application of transpalpebral scleral diaton tonometer makes it possible to evaluate IOP using only one device, the procedure being efficient, economical, simple and requires no additional instrument examination.


2. Clinical comparison of the Diaton and the Non-contact Tonometers with the Goldmann applanation tonometer in glaucoma patients


Purpose: Study of intraocular pressure evaluation (IOP) reliability using non-invasive devices, which require no anesthesia: transpalpebral scleral Diaton tonometer and non-contact pneumotonometer (NCT).

Method: Here the prospective comparative case series clinical study is presented. 87 patients (146 eyes) suffered from glaucoma (m:f = 51:36; age distribution: 29-85 years) were examined. For comparison IOP values received with Goldmann applanation tonometer (GAT) using the traditional methodology and digital mean values received with Diaton and NTC were used.

Results: Mean IOP was 17,4±7,6 mmHg with GAT, 16,7±5,58 mmHg with Diaton, 21,4±9,13 mmHg with NCT. Minimum IOP value was 6,0 mmHg with GAT, 6,0 mmHg with Diaton, 5,0 mmHg with NCT; maximum value was 40,0 mm Hg with GAT, 36,0 mmHg with Diaton, 47,0 mmHg with NCT. There was no significant difference of IOP values (t = -0,51, p < 0,001). The Pearson's correlation coefficient was r=0.89, p < 0,001 between GAT and Diaton; r=0,87, p < 0,001 between GAT and NCT. There was observed high correlation of both tonometers with GAT in IOP range up to 30 mm Hg. In case of IOP significant increase NCT showed IOP overestimation up to 7 mm Hg; Diaton showed IOP underestimation up to 4 mm Hg.

Conclusions: The study shows high reliability of transpalpebral screral Diaton tonometer enough for clinical purpose. It has both accuracy correlating with GAT and NCT's safety and operating speed. Diaton advantage is the possibility to evaluate IOP in cornea pathology, which is very important in glaucoma patients after corneal including laser surgeries.


3. Comparison of the Diaton Transpalpebral Tonometer Versus Goldmann Applanation

R. S. Davidson 1; N. Faberowski2 ; R. J. Noecker3 ; M. Y. Kahook1
1. Ophthalmology, Rocky Mountain Lions Eye Institute, Aurora, CO, USA.
2. Ophthalmology, Denver Health Medical Center, Denver, CO, USA.
3. Ophthalmology, UPMC, Pittsburgh, PA, USA.

Financial Disclosure
The authors have no financial interest in the subject matter being presented

Background
Diaton tonometry is a unique approach to measuring intraocular pressure (IOP) through the Eyelid. It is a non-contact (no contact with cornea), pen like, hand-held, portable tonometer. It requires no anesthesia or sterilization.

Purpose
To investigate the agreement in the measurement of intraocular pressure (IOP) obtained by transpalpebral tonometry using the Diaton tonometer versus Goldmann applanation in adult patients presenting for routine eye exams.

Methods
Retrospective chart review of consecutive IOP measurements performed on 64 eyes of 32 patients age 34-91 years with both the Diaton tonometer and Goldmann applanation. Results between groups were examined using analysis of variance (ANOVA) where appropriate.

Results
Mean IOP was 15.09 +/-4.31 mm Hg in the Goldmann group and 15.70 +/-4.33 mm Hg in the Diaton group (p=0.43).
Mean IOP variation between groups was 1.74 +/-1.42 mm Hg (range 0-8). 83% of all measurements were within 2 mm Hg of each other.

Conclusions
The transpalpebral method of measuring IOP with the Diaton tonometer correlates well with Goldmann applanation. Diaton applanation may be a clinically useful device for measuring IOP in routine eye exams.



4. Comparison of the Diaton Transpalpebral Tonometer Versus Tono-Pen Applanation

Theodore H. Curtis, M.D.1, Douglas L Mackenzie, M.D.1, Robert J. Noecker M.D.2, and Malik Y. Kahook M.D.1
1The Rocky Mountain Lions Eye Institute, University of Colorado Health Sciences Center, Aurora, CO
2Eye and Ear Institute, University of Pittsburgh Medical Center, Pittsburgh, PA

Financial Disclosures
· None of the authors have financial interests relevant to the supject discussed.
Purpose
· To compare intraocular pressure (IOP) measurements obtained with Diaton trans-palpebral tonometry versus Tonopen applanation tonometry in children and adults.

Introduction

· Goldmann applanation is the gold standard for IOP measurement
· It has been supplanted by TonoPen applanation in many settings because of it's ease of use, portability, convenience, and minimal training requirements.
· The TonoPen requires contact with the corneal surface, and has the risks of iatrogenic corneal injury, spread of pathogens, and requires topical anesthetics.

Introduction

· The newly-developed Diaton tonometer is a handheld device that measures pressure through the tarsal plate (Figures 1 & 2).
· It avoids contact with the cornea and the need for topical anesthesia.

Figure 1: The Diaton Transpalpebral Tonometer
Figure 2: Using the Diaton Tonometer

Methods

· We looked at 74 eyes of 38 consecutive patients who received both Tonopen and Diaton tonometry
· TonoPen measurements were taken in the sitting position following topical anesthesia with proparicaine.
· Diaton measurements were performed in the sitting position with the patient gazing at a 45o angle, placing the eyelid margin at the superior limbus. If necessary, gentle traction was placed on the brow to align the lid with the limbus. The device was activated when the signaling mechanism indicated the device was vertical.

Results

· Age range 3-91 years of age (mean 47.5 years).
· The average IOP with the Diaton was 16.24 (+/-5.11 mm Hg; range = 7-32 mmHg).
· The average IOP with the TonoPen was 16.37 (+/-4.90 mm Hg; range = 8-33 mmHg).
· The mean variation between the two modalities was 1.59 mmHg (+/-1.31 mm Hg; range = 0-6 mmHg).
· Eighty-one percent of all measurements were within 2 mmHg of each other (Table 1).
· There was no statistically significant difference in mean IOP values obtained with the two devices (p=0.87). Table

Conclusions
· The Diaton tonometer pressure measurements correlated well with TonoPen measurements in this retrospective review.
· We did not find problems performing the exam in children, and many were reassured by the fact that no drops were needed.
· There may be a notable benefit in patients after refractive surgery or with corneal pathology since the Diaton does not applanate the cornea.
· The Diaton tonometer appears to be a clinically useful device in the IOP measurement of both children and adults.

 

[orbitsurgMD]

in this turkish study they concluded:
The Diaton measurements show moderate correlation with those provided by applanation tonometry. The Diaton tonometer seems to be more affected by the corneal thickness, especially in the thinnest corneas.

i wonder, how.)

also, this chineese conclusion looks nice to me:
We cannot recommend Diaton as a substitute or alternative method for GAT for diagnosis and follow-up of patients with abnormal IOPs, but it may be helpful as a screening tool, especially for subjects whose age is between 20 and 50 years and for healthy subjects.

Unless there is some correlation between corneal thickness, and corneal rigidity and scleral rigidity?

 

[ophtho wannabe]

In case anyone cares, we ended up just having the Tonopen repaired which cost about $250. We'll see how it holds up. Thanks for all suggestions.

 

[OphthoRU]

Hey, does tonopen have any disposable parts? or is it fully self-sufficient?

 

[ophtho wannabe]

It requires a disposable cover for each use.