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Comparison of the ICare® rebound tonometer with the Goldmann tonometer in a normal population

The aim of this study was to evaluate the accuracy of measurement of intraocular pressure (IOP) using a new induction/impact rebound tonometer (ICare®) in comparison with the Goldmann applanation tonometer (AT).

Implantable Collamer Posterior Chamber Intraocular Lenses: A Review of Potential Complications

PURPOSE To review the peer-reviewed literature reporting postoperative complications of the most recent models of Visian Implantable Collamer posterior chamber intraocular lenses (ICL, STAAR Surgical Co). METHODS A literature search of the PubMed database was performed to identify all articles related to ICL complications. Articles were obtained and reviewed to identify those that reported complications using the latest ICL designs. RESULTS Cataract was the major postoperative complication reported: 136 (5.2%) in 2592 eyes. Of those, 43.4% (n=59) were reported within 1 year, 15.4% (n=21) between 1 and 3 years, and 35.3% (n=48) ≥ 3 years after ICL implantation. Twenty-one (15.4%) cataracts were reported as surgically induced, 46 (33.8%) eyes had poor vault (<200 μm), and cataract surgery was carried out in 27.9% (n=38) of eyes. Early acute intraocular pressure increase was also reported to be relatively frequent, whereas acute pupillary block was less frequent and mostly resolved with additional iridotomies. A total of 42 ICLs were explanted due to cataract and IOP. Reported endothelial cell loss varied from 9.9% at 2 years to 3.7% 4 years postoperatively. This loss was reported to be more pronounced within the first 1 to 2 years, with stability or lower progression after that time. CONCLUSIONS The majority of reported complications after ICL implantation are cataract formation. The improvements in lens geometry and more accurate nomograms applied to the selection of the lens to be implanted, in addition to the surgeons learning curve, might be factors in the decreased occurrence of postoperative complications reported currently.

Peripheral refraction in myopic patients after Orthokeratology

Purpose. The purpose of this study was to characterize the central and peripheral refraction across the horizontal meridian of the visual field before and after myopic corneal refractive therapy (CRT) with contact lenses. Methods. Twenty-eight right eyes from 28 subjects (mean age ± SD = 24.6 ± 6.3 years) were fitted with Paragon CRT contact lenses to treat myopia between −0.88 and −5.25 D of spherical equivalent. Along with a complete set of examination procedures to assess suitability for treatment, the central and peripheral refractions were measured along the horizontal meridian up to 35° of eccentricity in the nasal and temporal retinal area in 5° steps. Results. Baseline central average spherical equivalent (M) measured by subjective refraction changed from −1.95 ± 1.27 D to −0.38 ± 0.67 D. Changes in M component ranged between 1.42 ± 0.89 D at center and 0.43 ± 0.88 D at 20° in the temporal retina (p < 0.002). At 25° to both sides of the central refraction measurement, peripheral refraction after treatment was not statistically different from baseline values (p > 0.351). Beyond the 25° limit, M component changed in the myopic direction up to −1.11 ± 0.88 D at 35° in temporal retina (p < 0.001). Treatment induced was symmetric between nasal and temporal visual field along the horizontal meridian (p > 0.05 for all eccentricities). Furthermore, the degree of myopic increase in spherical equivalent for 30° (r2 = 0.573, p < 0.001) and 35° (r2 = 0.645, p < 0.001) eccentric refraction was highly correlated with axial spherical equivalent at baseline. Conclusions. CRT inverts the pattern of peripheral refraction in spherical equivalent refraction, creating a treatment area of myopic reduction within the central 25° of visual field, and a myopic shift beyond the 25°. In peripheral refraction for 30° and 35°, the amount of myopia induced in terms of spherical equivalent has an almost 1:1 relationship with the amount of baseline spherical equivalent refraction to be corrected.

Clinical performance of the Reichert AT550: a new non-contact tonometer

The aim of the present study was to assess the level of accuracy for measurements of intra‐ocular pressure (IOP) obtained with a new non‐contact tonometer (NCT) the Reichert AT550®. Measurements were compared against those obtained with the Reichert Xpert Plus, Goldmann applanation tonometer and Perkins tonometer. Thirty‐five university students were assessed with the four tonometers in a randomised order, with non‐contact tonometry performed first. Each of the four measurement devices had its own trained clinical observer. Plots of differences of IOP as a function of the mean for each pair of instruments were obtained. No statistically significant differences were found when comparing the AT550® NCT with contact applanation tonometry (AT) (p > 0.05), displaying the closest level of agreement (as represented by the lowest mean difference and the narrowest confidence interval) with the Goldmann tonometer (limits of agreement, 0.12 ± 2.17). In conclusion, readings of IOP with the AT550® NCT are clinically comparable with those obtained with Goldmann tonometry in a population with IOP within the normal range.

Correlations between corneal biomechanical properties measured with the ocular response analyzer and ICare rebound tonometry.

PurposeTo investigate the biomechanical properties of the normal cornea, and correlate them with central and peripheral corneal thickness and age. MethodsSeventy-six right eyes of volunteers were measured with Ocular Response Analyzer (ORA), ICare rebound tonometry and an ultrasound pachymeter at corneal center and at 4 mm from corneal center in the nasal and temporal directions. ResultsICare readings were significantly correlated with central and peripheral corneal thickness and corneal biomechanical properties. Corneal resistance factor was the biomechanical parameter with the higher correlation with ICare intraocular pressure (IOP) values. ICare tonometry at center and Goldmann equivalent IOP obtained with ORA were significantly higher for thicker than thinner corneas (P<0.05). IOP compensated for corneal properties with the ORA was lower than the remaining IOP values measured in the study. Higher correlation was found between Goldmann equivalent IOP with ORA and ICare IOP values. ConclusionsIOP values obtained with the rebound tonometer are higher in thicker corneas and are positively correlated with biomechanical corneal parameters, namely corneal resistance factor. Although corneal thickness plays a significant role in rebound tonometry, elastic and viscous properties of the cornea seem to play a significant role in the interaction of the tonometer probe with the ocular surface. However, the mechanism behind this process is presently unknown.

Clinical performance of non-contact tonometry by Reichert AT550 in glaucomatous patients.

Measuring intraocular pressure (IOP) by non‐contact tonometry (NCT) has been demonstrated to be a valid and reliable technique to be used in primary eye care; it is easier to use, it does not transmit infectious diseases, and it is not necessary to use anaesthetic or staining eye drops. Recently, a new NCT device has showed an excellent level of agreement with Goldmann tonometry, but there are no records of its performance in glaucomatous eyes. To rectify this, IOP was measured in twenty‐two patients (44 eyes) receiving medical treatment to control elevated IOP, with AT550® and Goldmann tonometry. Mean values of IOP were 18.98 ± 2.77 and 19.08 ± 3.02 mmHg using Goldmann and AT550®, respectively. Plots of differences against means displayed good agreement (mean difference ± limits of agreement, −0.09 ± 3.30); this value was not significantly different from zero (t‐test for dependent samples, p = 0.709). In conclusion, IOP values as measured with the AT550® NCT are clinically comparable with those obtained with Goldmann tonometry in glaucomatous patients. This validates this NCT not only for screening of IOP but to follow‐up glaucomatous patients with a rapid, non‐invasive method.

Refractive, biometric and topographic changes among Portuguese university science students: a 3-year longitudinal study

Purpose:  The aim of this study was to investigate the changes in refractive, biometric and topographic ocular parameters among university students in Portugal during a 3‐year period.

Central vault after phakic intraocular lens implantation: Correlation with anterior chamber depth, white-to-white distance, spherical equivalent, and patient age

PURPOSE: To compare the central postoperative vault of a phakic intraocular lens (pIOL) to correct myopia, myopic astigmatism, and hyperopia and identify ocular and lens parameters that might predict the vault amount. SETTING: Fernández‐Vega Ophthalmological Institute, Oviedo, Spain. DESIGN: Cohort study. METHODS: Three months after implantation of Implantable Collamer Lens pIOLs to correct myopia, hyperopia, and myopic astigmatism, central vault was measured using optical coherence tomography. Patients were divided into groups according to the preoperative anterior chamber depth (ACD) to compare the effects of ACD, white‐to‐white (WTW) distance, and lens diameter on postoperative pIOL vault. RESULTS: Hyperopic pIOLs had statistically significantly lower vault followed by myopic pIOLs and toric pIOLs, which had a higher mean value and narrower range (260 to 860 μm). Measured vaults had a positive correlation with preoperative ACD (r = .32, P<.001) and WTW (r = .29, P<.001) and a negative correlation with preoperative spherical equivalent (SE) (r = −0.21, P<.001) and patient age (r = −0.12, P=.025). Eyes with a vault of 250 μm or less had a shallower ACD than eyes with a vault between 250 μm and 750 μm (mean difference −0.11 mm; P=.012) and those with a vault greater than 750 μm (mean difference −0.25 mm; P<.001). CONCLUSIONS: Central vaulting was lower in hyperopic eyes. Current nomograms for pIOL diameter selection based on ACD and WTW might yield ideal vault and may have to be adjusted for older patients, shallower ACD, lower WTW, and lower SE. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Age differences in central and peripheral intraocular pressure using a rebound tonometer.

Aim: To evaluate the influence of age on the measurements and relationships among central and peripheral intraocular pressure (IOP) readings taken with a rebound tonometer. Methods: The IOPs were measured using the ICare rebound tonometer on the right eyes of 217 patients (88 men and 129 women) aged 18–85 years (mean 45.9 (SD 19.8) years), at the centre and at 2 mm from the nasal and temporal limbus along the horizontal meridian. Three age groups were established: young (⩽30 years old; n = 75), middle aged (31–60 years old; n = 77) and old patients (>60 years old; n = 65). Results: A high correlation was found between the central and peripheral IOP readings, with the central readings being higher than the peripheral ones. Higher IOP values for the central location were found in the younger patients. Older patients had significantly lower temporal IOP readings than those for the remaining two groups (p<0.001), whereas no significant differences were found among groups when IOP was measured at the central and nasal locations. A significant decrease was observed in the nasal and temporal IOP readings as the age increased (p = 0.011 and 0.006, respectively). Conclusion: Older patients had lower IOP values than the middle-aged and younger patients in the temporal peripheral location. A negative correlation was found between age and IOP by rebound tonometry in the corneal periphery but not in its centre.

The influence of cycloplegia in objective refraction

The purpose of this study was to compare refractions measured with an autorefractor and by retinoscopy with and without cycloplegia. The objective refractions were performed in 199 right eyes from 199 healthy young adults with a mean age of 21.6 ± 2.66 years. The measurements were performed first without cycloplegia and repeated 30 min later with cycloplegia. Data were analysed using Fourier decomposition of the power profile. More negative values of component M and J0 were given by non‐cycloplegic autorefraction compared with cycloplegic autorefraction (p < 0.0001). However more positive values for the J45 vector were given by non‐cycloplegic autorefraction, although this difference was not statistically significant (p = 0.233). By retinoscopy, more negative values of component M were obtained with non‐cycloplegic retinoscopy (p < 0.0001); for the cylindrical vectors J0 and J45 the retinoscopy without cycloplegia yields more negative values (p = 0.234; p = 0.112, respectively). Accepting that differences between cycloplegic and non‐cycloplegic retinoscopy are only due to the accommodative response, the present results confirm that when performed by an experienced clinician, retinoscopy is a more reliable method to obtain the objective starting point for refraction under non‐cycloplegic conditions.