Case Reports
In the following section, experts present case reports regarding the biomechanical properties of the cornea. The cases illustrate how important biomechanical properties in the daily clinical practice already are: either for screening before refractive surgery, the assessment after corneal cross-linking or to ensure a highly accurate measurement of intraocular pressure.
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Biomechanical Characterization of Subclinical Keratoconus Without Topographic or Tomographic Abnormalities
- 27-year old man with diagnosis of keratoconus in the left eye and normal right eye.
- Completely normal 4 Maps refractive OD.
- BADD score of 0.74 in the Belin/Ambrósio enhanced ectasia display indicated also a completely normal eye OD.
- 35-year old man referred to as „unilateral ectasia“ in the left eye.
- Fellow eye no signs of keratoconus in slit lamp examination.
- Completely normal 4 Maps refractive OD.
- BADD score of 0.68 in the Belin/Ambrósio enhanced ectasia display indicated also a completely normal eye OD.
- Completely normal 4 Maps refractive OD
- BADD-score 0.74
- Clinical keratoconus OS (kc grade 2-3)
- CBI abnormal (CBI = 0.7)
- DA ratio as individual parameter outside the normal range (>2 SD)
- CBI abnormal (CBI = 1)
- All individual biomechanical parameters abnormal
- Completely normal 4 Maps refractive OD
- Clinical keratoconus OS (kc grade 2-3)
- normal Belin Ambrósio analysis with BADD = 0.68 OD
- Normal pachymetric progression
- Normal elevation even in „enhanced“ elevation maps
- CBI abnormal (CBI = 1) with biomechanical response parameters indicating a soft cornea
- CBI abnormal (CBI = 1) with biomechanical response parameters indicating a very soft cornea
- These two patients were part of a case series of 12 patients with a diagnosis of subclinical keratoconus.
- All these patients were completely normal on tomography and topography in one eye but the other eye had clinical keratoconus.
- As keratoconus is a bilateral disease and „true unilateral keratoconus does not exist“1 these eyes are of particular interest to test the sensitivity to detect „sub-tomographic ectasia“.
- All patients of this case series had biomechanical changes already present in the tomographic „normal“ eye with abnormal CBI-index.
- CBI provides the possibility of an early diagnosis when tomography is normal on both eyes but show early signs of biomechanical decompensation.
Riccardo Vinciguerra, MD; Renato Ambrósio, Jr., MD, PhD; Cynthia J. Roberts, PhD; Claudio Azzolini, MD; Paolo Vinciguerra, J Refract Surg. 2017;33(6):399-407
Patient 1
Patient 2
Patient 1:
Figure 1: 4 Maps Refractive of the left and right eye
Patient 1:
OD
OS
Figure 2: Biomechanical parameters with Corvis Biomechanical Index (CBI) of left and right eye
Patient 2:
Figure 3: 4 Maps Refractive of the left and right eye
Patient 2:
Figure 4: Belin / Ambrósio display of the right eyes
Patient 2:
Figure 5: Biomechanical parameters with Corvis Biomechanical Index (CBI) of left and right eye
Conclusions
1José A. P. Gomes, MD, PhD, Donald Tan, MD, PhD,Christopher J. Rapuano, MD, Michael W. Belin, MD, Renato Ambrósio, Jr, MD, PhD, José L. Guell, MD,François Malecaze, MD, PhD,Kohji Nishida, MD,and Virender S. Sangwan, MD: “Global Consensus on Keratoconus and Ectatic Diseases”: Cornea 2015;34:359–369
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Corneal Ectasia After LASIK Despite Low Preoperative Risk: Tomographic and Biomechanical Findings in the Unoperated, Stable, Fellow Eye
- DCVA 20/15 OD with 6.00 = 1.00 x 180° (unoperated stable eye).
- OS: progressive corneal ectasia after LASIK with no detectable preoperative risk factors.
- Randleman ERSS score was 2 for the pre-op status of the operated eye and 1 OD for the stable unoperated eye.
- Unoperated eye OD remains stable with normal topography and stable refraction for > 5 years.
- Placido topography shows normal topography OD
- Placido topography reveals post LASIK ectasia OS
- Normal Placido topography OD (Keratograph 5M)
- Normal Pentacam 4 maps refractive with slightly inferior steepening
- Corneal thickness 545 µm
- No progression over the past 10 years
- Abnormal Tomographic Biomechanical Assessment with TBI = 0.82 indicates high ectasia risk OD
- Integration of Scheimpflug Tomography and Biomechanics reveals the high ectasia risk
- Corneal ectasia after LASIK despite low risk factors pre-operatively OS.
- Unoperated eye OD remains stable with normal topography and stable refraction for > 5 years and reveals low risk factors based on corneal topography alone.
- Tomographic Biomechanical Assessment reveals high ectasia susceptibility OD based on the TBI.
- Ectasia might have been prevented OS if Tomographic Biomechanical assessment would have been already available.
Renato Ambrósio, Jr, MD, PhD; Daniel G. Dawson, MD; Marcella Salomão, MD; Frederico P. Guerra, MD; Ana Laura C. Caiado, MD; Michael W. Belin, MD
Figure 1: Placido topography of the right and left eye.
Topography / tomography of the stable unoperated eye OD:
Figure 2: 4 Maps Refractive of the stable right eye
Figure 3: Placido Topography of the stable right eye
Figure 4: Ambrósio, Roberts & Vinciguerra Tomography and Biomechanics Report (ARV Report)
Conclusions
- Two identical 48 year-old female twins were presented for clinical evaluation.
- Twin1: Uncorrected visual acuity 20/200 OD and 20/40 OS.
- Twin 2: 20 /25 OD and 20/30 OS.
- Mild keratoconus detected OD of twin 1 by classical slit-lamp findings.
- Twin 1: Grade 1 topographical keratoconus pattern OD and also topographical abnormalities OS.
- Corneal front surface topography was normal in both eyes of twin 2.
- Corneal tomography (Pentacam) and biomechanical assessment was performed on both twins.
- Front surface topography shows inferior steepening on both eyes.
- Keratoconus grade 1 OD and „kc possible“ OS on the Topographical Keratoconus classification (TKC).
- Relatively normal topography on both eyes of twin 2.
- No keratoconus detected based on anterior surface indices on twin 2.
- TBI abnormal in all eyes of both twins with altered biomechanical properties.
- Case illustrates the possibility for enhancing the sensitivity for detecting subclinical ectasia using corneal tomography in combination with corneal biomechanical analysis.
- This case also demonstrates that subclinical keratoconus or fruste disease may occur in both eyes.
- It further demonstrate the better representation of corneal genotype in detecting mild, subclinical or fruste keratoconus in the fellow eye based on Tomographic Biomechanical Assessment.
- These cases present high risk of susceptibility for ectasia progression if environmental factors are associated (second hit).
Gustavo Guerra, Vitor Buchmuller de Oliveira, Ivan Ferreira, Isaac Ramos, Michael W Belin Renato Ambrósio Jr
Corneal front surface topography on both twins
Figure 1: Front surface topography OU of the two twins
Twin 1
Twin 2
Figure 2: Ambrósio, Roberts & Vinciguerra Tomography and Biomechanics Report (ARV Report) of both twins.
Conclusions
- Male, 30 years
- First visit at 10th of July 2017
- Positive family history of glaucoma
- Refraction:
- OD: -0.5 / -0.25 @100
- OS: +1.0 / -2.75 @ 89
- Visual acuity: OD = 1.25; OS = 0.6
- Fundus: abnormal papilla OS
- Slit lamp examination:
- OD no findings
- OS Vogt striae, Fleischer ring
- Topography / Tomography relatively normal OD with suspicious pachymetric progression.
- Tomographic / Biomechanical Assessment abnormal with TBI = 1
- Reduced Stiffness Parameter (SP-A1).
Prof. Eberhard Spörl, PhD; Robert Herber University of Dresden, Germany
Prof. Dr. Frederik RAISKUP, MD, PhD, FEBO
Figure 1: Ambrósio, Roberts & Vinciguerra Tomography and Biomechanics Report (ARV Report) OD.
- Condition after LASIK on both eyes.
- Reduced visual acuity OD: BCVA 20/100 OD; 20/20 OS.
- Slit-lamp biomicroscopy OD: Layer of corneal opacity underneath the flap.
- Goldman Applanation Tonometry: 12mmHg OD.
- High-resolution Scheimpflug images and slit lamp examination identified a hyperreflective zone without a fluid-filled space under the flap.
- Biomechanical Response before and after medical treatment (Oral acetazolamide 250 mg TID, topical fixed combination of dorzolamide and timolol maleate BID).
- Biomechanical Response before and after medical treatment (Oral acetazolamide 250 mg TID, topical fixed combination of dorzolamide and timolol maleate BID).
- Case of Pressure-induced Stromal Keratopathy (PISK).
- Could be easily misdiagnosed as deep lamelar keratitis.
- This would lead to improper steroid therapy (potential vision loss by glaucomatous neuropathy).
- Goldman applanation tonometry was 12mmHg, whereas Corvis® ST IOP was 53.5 mmHg with low deformation amplitude.
- Corneal biomechanical assessment together with ultra-high speed Scheimpflug imaging provided valuable data for proper diagnosis and treatment regimen.
Faria-Correia F, Ramos I, Valbon B, Luz A, Roberts CJ, Ambrósio R Jr.; J Refract Surg. 2013 29(5):356-3588
Figure 1: Scheimpflug images on 15th of February and two days later OD
Figure 2: Maximal corneal deformation on 15th of February and two days later OD after medical treatment
Conclusions
- Visual acuity: UDVA 20/20 in both eyes.
- Anterior surface keratoconus (Amsler Krumeich related) grading still indicates pre-stage.
- Mild change in anterior and posterior surface tomography detected OS.
- Biomechanical parameters also indicate softening of the tissue in both eyes.
- Based on these findings CXL is indicated OU.
- Baseline tomographic biomechanical assessment reveals „sub-topographical keratoconus OD and keratoconus stage 1-2 OS (Amsler grading).
- Tomographic & Biomechanical assessment shows indicates keratoconus already on both eyes (TBI = 0.98 OD and TBI = 0.99 OS).
- The display reveals progression for the left eye on anterior (A) and posterior (B) curvature as indicated by the increase of the bars over the solid red line.
- No significant changes based on tomographic parameters could be observed for OD.
- Biomechanical parameters indicate also progression in both eyes as the values shift into the „red“ population of keratoconic patients as indicated by the the black vertical lines.
- Case of asymmetric early ectasia in 2014 with keratoconus pre-stage OD based on Amsler criteria.
- Based on Tomographic Biomechanical Assessment keratoconus was confirmed in 2014 OU.
- The keratoconus very mildly progressed as shown by moderate change of anterior and posterior curvature data OS.
- However, tomographic data didn´t show progression OD whereas biomechanical parameters showed further softening of the tissue in both eyes.
- Corneal cross-linking was indicated also for OD.
Prof. Renato Ambrósio, MD, PhD; Rio de Janeiro; Brazil
2014
Figure 1: Ambrósio, Roberts & Vinciguerra Tomography and Biomechanics Report (ARV Report) in 2014 for both eyes.
Figure 2: Pentacam ABCD progression display for both eyes.
OD (2014)
OS (2014)
OD (2018)
OS (2018)
Figure 3: Four biomechanical parameters and the relation to normative data of healthy patients (green) and keratoconic patients (red) in 2014 (top) and 2018 (bottom) of right and left eye.
Conclusions
- Patient with frank keratoconus in both eyes.
- UV-cross-linking was performed in combination with topo-guided PRK.
- Consequently, the cornea has become slightly thinner and the topography more regular.
- Biomechanical response was monitored 10 month after the procedure with the Corvis® ST.
- greater stability in post-op “blue” image than in pre-op “red” image despite thinner cornea due to the PRK.
- greater stability in post-op “blue” image than in pre-op “red” image.
- Stiffness parameter SP-A1 has increased from 25 to 50.
- Due to the CXL the cornea has become slightly thinner and the topography more regular.
- However, Dynamic Corneal Response video shows clearly higher rigidity after the procedures.
- Biomechanical parameters such as Stiffness Parameter SP-A1 also show quantitatively stiffening of the cornea.
- This case suggests that biomechanical parameters from the Corvis® ST are able to detect early changes in biomechanics following CXL.
- The efficiency of the procedure can be measured at a time point before corneal shape modifications usually occur.
Prof. Renato Ambrósio, MD, PhD; Cynthia Roberts, USA
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Direct Comparison
Red: Keratoconus cornea, Blue: same cornea after CXL
Screening parameter pre-op
Screening parameter post-op
Figure 1: Change of biomechanical parameters after CXL plus topo-guided PRK.
Conclusions
- 39 year old female.
- Contact lens intolerant.
- Asks for refractive surgery.
- Out of contact lenses for three days.
- Refraction:
- 9.00 -2.25 @10° OD giving 20/25.
- 9.25 -2.00 @170° OS giving 20/25. - Tear film assessment indicates some dry eye problems.
- Inferior steepening Placido-topography maps.
- Short break-up times indicate insufficient tear-film quality.
- Corneal tomography reveals normal elevation maps and normal pachymetric progression.
- Biomechanical parameters indicate stiff corneas in both eyes.
- TBI indicates very low risk for ectasia.
- The patient had a corneal warpage that caused the inferior steepening in Placido topography maps.
- Both tomography and biomechanics confirm that the cornea was stable with no incidence of subclinical keratoconus.
- Corneal stiffness was even higher than the mean of healthy population.
- Contact lens intolerance was caused by severe dry eye problems as observed by short Break-up times (NIKBUT measurements) and several Meibomian Glands dropouts.
Prof. Renato Ambrósio, MD, PhD; Rio de Janeiro; Brazil
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Figure 1: Placido topography of anterior surface and non-invasive break-up time measurements (NIKBUT) OU.
OD
OS
Figure 2: Ambrósio, Roberts & Vinciguerra Tomography and Biomechanics Report (ARV Report) for both eyes.
