A Prospective Trial Evaluating Scleral Rebound Tonometry
Sara Duke, MD, Andrew Logeman, Shuchi Patel, MD
Loyola University Chicago, Department of Ophthalmology, Maywood IL
Introduction
Results
Current devices used to estimate intraocular
pressure (IOP) perform the measurements on
the cornea. This is not possible in some
patients such as those with a keratoprosthesis
or other corneal pathology. Glaucoma is
known to occur in about 75% of patients
following a keratoprosthesis, but accurate
pressure readings to monitor for adequate IOP
control are not possible. Previous studies
have examined the use of the TonoPen,
Schiotz tonometer and pneumotonometer on
the sclera to measure IOP with limited
success, and none have repeatedly shown a
statistically significant correlation to corneal
tonometry.
184 eyes from 101 patients ages 24-90 years
old were included in this study. 116 eyes from
59 patients were analyzed as 68 eyes were
omitted due to incomplete data.
Purpose
To determine if a predictable relationship
exists between the gold standard of IOP
measurement, Goldmann applanation
tonometry (GAT), and scleral rebound
tonometry (RT) to provide an accurate and
reliable assessment of IOP via scleral
measurements.
Methods
A prospective non-randomized trial of
individuals 18 years of age and older. Each
had his/her IOP measured by GAT, next corneal
RT then scleral RT on the inferotemporal
sclera. The patient’s age, gender, refractive
error, central corneal thickness (CCT), axial
length (AL) and phakic status were recorded.
Pearson’s correlation and multivariate
regression analysis were used for statistical
examination.
Mean GAT IOP was 15.91 mmHg (SD 4.13),
mean corneal RT was 14.50 mmHg (SD 4.24)
and mean scleral RT was 48.84 (SD 21.41).
Mean spherical equivalent refraction (SE) was 0.21 D (SD 2.05), mean CCT was 547.68 µm (SD
45.65), mean AL was 24.06 mm (SD 1.21). 89
eyes were phakic and 27 were pseudophakic.
Results
Demographics/Characteristics
Average
(mmHg)
Standard
Deviation
Average
Standard
Deviation
GAT
15.91
4.13
CCT (µm)
547.68
45.65
Corneal RT
14.50
4.24
AL (mm)
24.06
1.21
Scleral RT
48.84
21.41
SE (D)
-0.21
2.05
Pearson analysis reveals a strong positive
correlation between GAT and corneal RT (0.77)
but weak positive correlation between GAT and
scleral RT (0.22) as well as corneal RT and
scleral RT (0.22). This trend persists when
phakic and pseudophakic eyes are evaluated
independently. Multivariate regression
analysis was also performed and did not find a
correlation between scleral RT and GAT when
accounting for GAT, CCT, AL and SE.
101 (59)
Eyes included (analyzed)
184 (116)
Male:Female
28:31
Mean age (range)
65 (37-90)
Mean spherical equivalent
-7.00 to -2.01
-2.00 to +2.00
+2.01 to +3.25
-0.21
15.7%
78.5%
5.8%
Past Ocular History (eyes)
Glaucoma
Glaucoma suspect
Ocular hypertension
Pseudophakic
Diabetes
Thyroid eye disease
39
39
3
27
14
2
Conclusions
•Scleral RT shows consistently higher IOP
measurements than the corneal IOP
measurements from the same eye.
Discussion
Scleral RT shows IOP measurements that are
consistently higher than corneal IOP
measurements by roughly 33-34 mmHg.
Corneal RT correlates well to GAT;
unfortunately, scleral RT measurements have
poor correlation to corneal measurements
independent of phakic status. Analysis of
scleral RT with relation to GAT, CCT, AL and SE
concurrently fails to reveal a statistically
significant regression model in either phakic
or pseudophakic eyes. This is likely due to the
increased number of variables which effect
scleral rigidity. In addition, the overlying
conjunctiva undoubtedly contributes to
inconsistent scleral IOP readings.
Patients included (analyzed)
Multivariate regression model assessing the relationship between scleral rebound
tonometry and ophthalmic variables as listed above.
References
1.Barraza RA, Sit AJ. Investigation to determine a relationship between scleral and corneal tonometry. ARVO poster presentation; May 02,
2010.
2.Brusini P, Salvetat ML, Zeppieri M, Tosoni C, Parisi L. Comparison of ICare tonometer with Goldmann applanation tonometer in
glaucoma patients. J Glaucoma 2006; 15(3): 213-217.
3.Erlich JR, Haseltine S, Shimmyo M, Radcliffe NM. Evaluation of agreement between intraocular pressure measurements using
Goldmann applanation tonometry and Goldmann correlated intraocular pressure by Reichert’s ocular response analyser. Eye 2010;
24(10); 1555-1560.
4.Duke SL, Abugo U, Patel S. A prospective trial comparing scleral pneumotonometry to Goldmann applanation tonometry. ARVO poster
presentation; May 10, 2012.
5.Shen CC, Downs J, Mansberger SL. Assessment of intraocular pressure along the limbus and sclera using contact and indentation
tonometry. ARVO poster presentation; May 02, 2010.
•Scleral RT has a statistically significant
positive correlation to corneal RT.
•In this study, scleral RT does not provide
accurate and reliable IOP measurements when
compared to GAT even after adjusting for
phakic status, CCT, AL and SE.
•Further studies are needed to establish an
accurate and reliable method of scleral
tonometry such that patients with a
keratoprosthesis and glaucoma can be better
monitored.
Acknowledgements: This work was supported by the
Richard A. Perritt Charitable Foundation.