How To Check For Cornneal Thickness?

Posted on Thu, 21 Aug 2014

Medically reviewed by Ask A Doctor - 24x7 Medical Review Team

Thu, 21 Aug 2014 Answered on

Mon, 8 Sep 2014 Last reviewed on

Question : Greetings. I recently went for an annual checkup to a new ophthalmologist. For the previous several years I was diagnosed with "borderline glaucoma" with no adverse effects and pressure of 21-23 in both eyes (my left eye also has a nevus at the back). The new doctor found my pressure to be in a NORMAL range (18-19) in both eyes and said that my right eye had a thickened cornea which produces a false positive for elevated IOP. He also said that different examining machines can produce different results! The previous doctor had never tested my corneas! In any event my left eye does not have a thickened cornea, yet now fell also within the normal range. He told me I could come back in six months to check again. I am a bit mystified by these differences and changes! Any clarifications would be greatly appreciated!

Answered by Dr. N K Mishra (5 hours later)

Brief Answer:
Glaucoma Suspect

Detailed Answer:
My Dear
thanks for sending your query to us.
I would rate this new ophthalmologist higher.Cornneal thickness effects iop measurements .Certain equipments like Applanation tonometer give you more accurate iop measurements as they take Corneal thickness in to account. That is the reason why you are glaucoma suspect and not a glaucoma patient.
Follow the instructions of this ophthalmologist and do get back to me in case of any further query in this regard

Above answer was peer-reviewed by : Dr. Yogesh D

Follow up: Dr. N K Mishra (9 minutes later)

Thank you. The thickness was only in the left eye, so how does it occur that a lower number was achieved in the other eye as well when no lower numbers had been suggested over several years by the other doctor?Also, how would equipment in different offices produce different results? Does this affect the number of both false positives and false negatives in the population??

Answered by Dr. N K Mishra (1 hour later)

Brief Answer:
Glaucoma suspect

Detailed Answer:
My Dear,
Thanks for getting back to us.
It is not the same instrument in different offices that gives different result,but it is different instruments for measuring iop in the same office that give you different readings due to taking in account corneal thickness.
There is indententation methods where corneal elasticity and thickness makes a difference,while applanation method does not indent so gives more accurate reading.
That is why i will go with the ophthalmologist taking in account corneal thickness,iop reading is more reliable.
Thicker or thinner cornea effects the apparent reading and not the actual reading.
I hope i have made it understandable to you,any difficulty,do get back to me.

Above answer was peer-reviewed by : Dr. Bhagyalaxmi Nalaparaju

Follow up: Dr. N K Mishra (19 minutes later)

Thank you. Do you mean that could even make a lower reading in the other eye that is not specifically affected by thicker cornea??

Answered by Dr. N K Mishra (28 minutes later)

Brief Answer:
Glaucoma suspect

Detailed Answer:
Welcome back,
That is true and at all examinations the iop should be within normal limits.
Any problem ,please do get back to us.

Above answer was peer-reviewed by : Dr. Bhagyalaxmi Nalaparaju