Non-contact tonometry synchronized with cardiac rhythm and its relationship with blood pressure

Intrasession and Intersession Variabilities of Intraocular Pressure Measured by Noncontact Tonometer in Normal Volunteers

Purpose

Intraocular pressure (IOP) measured using a noncontact tonometer is evaluated by performing multiple measurements because IOP is affected by the ocular pulse. We investigated the relationship between value fluctuations in multiple measurements during noncontact tonometer measurements and cardiac rate.

Materials and Methods

Forty-two healthy subjects were included and IOP was measured using a noncontact tonometer. The measurement was performed three times each for the right eye and the left eye, for a total of six times. Blood pressure and cardiac rate were measured at the same time as the IOP measurement. Using repeated-measures analysis of variance, we examined whether the measured IOP and cardiac rate fluctuate throughout the day over the course of 4 days.

Results

There was a fluctuation in the IOP in a sequence only on day 1 of the four measurement days (P < 0.001). The IOP on day 1 tended to be high for the first and second measurements (P = 0.0111–0.0015). Systolic blood pressure and diastolic blood pressure did not fluctuate over the 4 days (P = 0.6247 and 0.7132), but cardiac rate was high only on day 1 (P = 0.0276).

Conclusion

The IOP on day 1 tended to be high in the first and second measurements. The IOP measured on days 2–4 did not fluctuate during the sequence of measurements. The cardiac rate measured at the same time as the IOP was high only on the first day.

Peripheral refraction of myopic eyes with spectacle lenses correction and lens free emmetropes during accommodation

PURPOSE

To measure axial and off-axis refraction patterns in myopic eyes with spectacle lenses correction and lens free emmetropes in young healthy subjects at different target distances from 2.00 m (0.50 D) to 0.20 m (5.00 D) in terms of sphere, astigmatism, and spherical equivalent refraction.

METHODS

Refraction was measured at the center, 20 and 40 degrees from the line of sight both nasally and temporally in 15 emmetropic and 25 myopic young healthy subjects with an open field, binocular, infrared autorefractor (Grand Seiko WAM-5500, Hiroshima, Japan). Fixation target was a Maltese cross set at 2.00, 0.50, 0.33 and 0.20 m from the corneal plane. Changes in off-axis refraction with accommodation level were normalized with respect to distance axial values and compared between myopic eyes with spectacle lenses correction and lens free emmetropes.

RESULTS

Off-axis refraction in myopic eyes with spectacle lenses correction was significantly more myopic in the temporal retina compared to lens free emmetropes except for the closest target distance. Relative off-axis refractive error changed significantly with accommodation when compared to axial refraction particularly in the myopic group. This change in the negative direction was due to changes in the spherical component of refraction that became more myopic relative to the center at the 0.20 m distance as the J0 component of astigmatism was significantly reduced in both emmetropes and myopes for the closest target.

CONCLUSION

Accommodation to very near targets (up to 0.20 m) makes the off-axis refraction of myopes wearing their spectacle correction similar to that of lens free emmetropes. A significant reduction in off-axis astigmatism was also observed for the 0.20 m distance.

The Impact of Overnight Orthokeratology on Accommodative Response in Myopic Subjects

This study aimed to evaluate the effects of two months of orthokeratology (OK) treatment in the accommodative response of young adult myopes. Twenty eyes (21.8 ± 1.8 years) were fitted with the Paragon CRT^® 100 LENS to treat myopia between −1.00 and −2.00 D. Low- and high-contrast visual acuity (LCDVA and HCDVA), central objective refraction, light disturbance (LD), and objective accommodative response (using the Grand Seiko WAM-5500 open-field autorefractometer coupled with a Badal system) were measured at baseline (BL) before lens wear and after 1, 15, 30, and 60 nights of OK. Refractive error correction was achieved during the first fifty days of OK lens wear, with minimal changes afterwards. LD analysis showed a transient increase followed by a reduction to baseline levels over the first 30 nights of treatment. The accommodative response was lower than expected for all target vergences in all visits (BL: 0.61 D at 1.00 D to 0.96 D at 5.00 D; 60 N: 0.36 D at 1.00 D to 0.79 D at 5.00 D). On average, the accommodative lag decreases over time with OK lens wear. However, these differences were not statistically significant (p > 0.050, repeated-measures ANOVA and Friedman test). This shows that overnight OK treatment does not affect objectively measured the accommodative response of young, low myopic eyes after two months of treatment stabilization.

Retinal Response of Low Myopes during Orthokeratology Treatment

The aim of this study was to evaluate the changes in retinal activity during orthokeratology (OK) treatment in 20 myopic eyes. Pattern electroretinography (PERG) and visual evoked potential (VEP) were assessed with the RETI-port/scan21 (Roland Consult, Wiesbaden, Germany). Measurements were taken at baseline (BL) and 1 night (1N), 15 nights (15N), 30 nights (30N), and 60 nights (60N) of OK lens wear. Repeated measures analysis of variance (ANOVA) and the Friedman test were used. Twenty eyes (23.20 ± 3.46 years, 70% female) with visual acuity ≤ 0.00 logMAR in post-treatment showed that despite a slight increase in retinal and cortical response amplitude, observed with both PERG and VEP, respectively, immediately after the initial treatment, these differences found were not statistically significant during the 60 days of OK treatment, despite a statistically significant increase in N95 response with PERG. This shows that retinal and cortical visual-related electrical activity is maintained or slightly increased during OK treatment.

Corneal morphology and visual outcomes in LASIK patients after orthokeratology: A pilot study

A STATEMENT OF SIGNIFICANCE

For the first time, this study shows that corneas that previous undergone orthokeratology treatment do not respond differently to LASIK compared with previous soft contact lens wear experience.

PURPOSE

To evaluate and compare the corneal morphology and visual outcomes of long-term soft and orthokeratology (OK) contact lens fitting in wearers undergoing corneal refractive surgery (LASIK) for myopia correction.

METHODS

Sixteen (16) myopic patients wearing hydrophilic soft contact lens (SCL, n = 8 subjects, control group) and OK (n = 8 subjects, OK group) lenses who undergone LASIK were retrospectively evaluated. Preoperative fitting of contact lenses and one year postoperative were studied using Pentacam (Oculus, Inc. GmbH, Wetzlar, Germany). Corneal pachymetry and volume, corneal topography, anterior and posterior surface elevation data and the anterior surface aberrometry of the cornea were recorded and used for fitting.

RESULTS

Age, refractive error and topographic parameters before LASIK did not showed statistically significant differences between the two study groups. LASIK post-treatment results showed identical changes in both control and OK groups and did not show significant differences in all the parameters evaluated. The changes on corneal parameters and HOA due to refractive surgery intervention were not different between Control and OK group (p > 0.050).

CONCLUSIONS

Corneal changes due to OK treatment are reversible after its discontinuation. The present study gives an overview of how OK does not impair future LASIK surgery for the correction of myopia and does not influence the success/results of such intervention. These findings suggest that OK CL wear does not change corneal biomechanics and does not compromise a possible LASIK refractive surgery. Although this is a pilot study and there is a need of evaluate this results/changes in future studies.

Relative peripheral refraction across 4 meridians after orthokeratology and LASIK surgery

Background

To characterize the axial and off-axis refraction across four meridians of the retina in myopic eyes before and after Orthokeratology (OK) and LASIK surgery.

Methods

Sixty right eyes with a spherical equivalent (M) between − 0.75 to − 5.25 D (cylinder <− 1.00 D) underwent LASIK (n = 26) or OK (n = 34) to treat myopia. Axial and off-axis refraction were measured with an open-field autorefractometer before and after stabilized treatments. Off-axis measurements were obtained for the horizontal (35° nasal and temporal retina) and vertical (15° superior and inferior retina) meridians, and for two oblique directions (45–225° and 135–315°) up to 20° of eccentricity. The refractive profile was addressed as relative peripheral refractive error (RPRE).

Results

OK and LASIK post-treatment results showed an increase of myopic relative refraction at several eccentric locations. At the four meridians evaluated, the M component of the pre-treatment RPRE values was not statistically different (p > 0.05) from the post-treatment RPRE within 30° and 20° of the central visual field after LASIK and OK, respectively. These results demonstrated that the treatment zone warrants an optimal central field of vision.

Conclusions

The present study gives an overview of RPRE after refractive corneal reshaping treatments (OK and LASIK) across vertical, horizontal and two oblique meridians together. This allows a 3D representation of RPRE at the retina and shows that the myopic shift induced by both treatments is more relevant in horizontal directions.

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 degrees of eccentricity in the nasal and temporal retinal area in 5 degrees 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 degrees in the temporal retina (p < 0.002). At 25 degrees 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 degrees limit, M component changed in the myopic direction up to -1.11 +/- 0.88 D at 35 degrees 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 degrees (r2 = 0.573, p < 0.001) and 35 degrees (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 degrees of visual field, and a myopic shift beyond the 25 degrees. In peripheral refraction for 30 degrees and 35 degrees, 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.

Comparison of the IOPen and iCare rebound tonometers with the Goldmann tonometer in a normal population

This study proposes to evaluate the level of accuracy of intraocular pressure (IOP) measurements of a second generation rebound tonometer (IOPen, taking as references the Goldmann Applanation Tonometer (GAT) and the iCare rebound tonometer. The right eyes of 101 consecutive clinical patients were assessed with the three tonometers. The IOPen and iCare measurements were taken by two different optometrists and the GAT by an ophthalmologist. In this study, statistically significant differences were found when comparing the IOPen tonometer with the other two tonometers (p < 0.001). The IOPen underestimated the IOP value when compared to the GAT and the iCare (mean differences were 2.94 +/- 4.65 mmHg and 3.20 +/- 4.72 mmHg (mean +/- S.D.), respectively). The frequency distribution of differences demonstrated that in more than 55% of measurements the IOP readings differed by more than 3 mmHg between the IOPen and the GAT. Based on the present population study, these results suggest that IOPen measurements should be interpreted with caution.

Influence of fogging lenses and cycloplegia on open-field automatic refraction

PURPOSE

To compare refractive values measured with and without cycloplegia, or with fogging lenses, using an open-field auto-refractor.

METHODS

One hundred and forty-two young adults were enrolled from a university population; 96 were female (67.6%) and 46 were male (32.4%), the age range was 18-26 years (mean 22.3 +/- 3.7 years). The refraction measurement was obtained for the right eye of each subject with the Grand Seiko Auto Ref/Keratometer WAM-5500 (GS) under three conditions, always in this sequence: (1) without cycloplegia (GS), (2) without cycloplegia but using a + 2.00 D fogging lens (GS_2D) and (3) with cycloplegia (GS_cycl).

RESULTS

When the average values of spherical equivalent were compared, both accommodation control strategies were almost equally successful: GS, M = -0.85 +/- 2.21 D; GC_2D, M = -0.53 +/- 2.10 D and GS_cycl, M = -0.57 +/- 2.24 D (Kruskal-Wallis test, p < 0.001). When the results were analysed separately for different refractive groups, emmetropes and hyperopes show statistically significant differences while myopes did not. When both accommodation strategies were compared there was a trend for more myopic subjects to display more negative values under cycloplegia, while low myopes, emmetropes and hyperopes tend to display more negative values with the +2.00 D fogging lenses, suggesting this was less effective for accommodation control.

CONCLUSIONS

Over-refraction through +2.00 D fogging lenses is useful to achieve additional relaxation of the accommodative response in a similar way to cycloplegia when open-field autorefraction is performed in young adults.

Technical note: a comparison of central and peripheral intraocular pressure using rebound tonometry

PURPOSE

To compare central and peripheral intraocular pressure (IOP) readings obtained with rebound tonometry.

METHODS

Intraocular pressure was measured on the right eye of 153 patients (65 males, 88 females), aged from 21 to 85 years (mean +/- S.D., 55.5 +/- 15.2 years) with the ICare rebound tonometer at centre, and 2 mm from the limbus (in the nasal and temporal regions along the 0-180 degrees corneal meridian).

RESULTS

Intraocular pressure values obtained with the ICare were 14.9 +/- 2.8; 14.1 +/- 2.5 and 14.5 +/- 2.7 mmHg at centre, nasal and temporal corneal locations, respectively. On average, nasal and temporal IOP readings were 0.75 and 0.37 mmHg lower than the central reading (p < 0.05 and p > 0.05, respectively). A highly significant correlation was found between central and peripheral measurements in nasal (r(2) = 0.905; p < 0.001) and temporal (r(2) = 0.879; p < 0.001) regions along the horizontal meridian. Almost 80% of patients presented nasal IOP values within +/-1 mmHg of the central value.

CONCLUSIONS

Intraocular pressure values measured with the ICare rebound tonometer on the nasal corneal region is slightly lower on average and highly correlated with IOP values recorded at corneal centre. Both nasal and temporal readings are in good agreement with central IOP, and could be used to obtain a reliable estimate of rebound IOP in corneas where central readings cannot be taken.

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 (< or =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.