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Results for “INTRAOCULAR PRESSURE”

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PubMed1996

The effects of therapeutic contact lenses on intraocular pressure measurement.

PURPOSE: To evaluate the accuracy of intraocular pressure (IOP) measurements taken through three commonly used therapeutic contact lenses, using both the Tono-Pen and pneumatonometer. METHODS: We measured the IOP of ten normal eyes and ten eyes with abnormal anterior segments using Tono-Pen, pneumatonometry, and Goldman application tonometry. Three different soft contact lenses (Acuvue, 04, and Permalens) were sequentially placed on the eyes and repeat measurements were taken. The readings obtained for each contact lens were compared to the baseline readings taken without a lens in place in order to assess the effect that each contact lens had on the accuracy of IOP measurements. RESULTS: All three contact lenses permitted accurate IOP measurements in eyes with both normal and abnormal anterior segments. Variations in water content and central thickness did not affect the accuracy of IOP measurements. CONCLUSIONS: Both Tono-Pen and pneumatonometry proved to be equally reliable in recording accurate IOP measurements through therapeutic contact lenses.

Adult↗

PubMed1980

Breakdown of the normal optic nerve head blood-brain barrier following acute elevation of intraocular pressure in experimental animals.

Five hours of elevated intraocular pressure produced evidence of an altered blood-brain barrier at the optic nerve head in 27 of 29 monkey eyes. The change in vascular permeability was documented by fluorescein angiography (18 of 21 eyes), by Evans blue fluorescence microscopy (21 of 23 eyes), or by both methods. Leakage occurred from major blood vessels as well as from microvasculature of the nerve head. In 22 eyes, rapid axonal transport was studied after intravitreal injection of tritiated leucine. In 18 of these 22 eyes, autoradiography demonstrated a local interruption of axonal transport. In 15 eyes examined by all three methods, leakage from microvasculature (as opposed to leakage from the major vessels) was loosely associated with severe and widespread blockade of axonal transport at the lamina cribrosa. Although cause-and-effect relationships are not proved, ischemia may be responsible both for the focal endothelial damage with breakdown of the normal blood-brain barrier and for the local abnormalities of axonal transport.

Animals↗

PubMed1988

Nd:YAG laser posterior capsulotomy does not produce elevation of intraocular pressure in cynomolgus monkeys.

The mechanism of the intraocular pressure (IOP) elevation commonly seen in patients following neodymium (Nd):YAG laser posterior capsulotomy is unclear. Substance P, a potent polypeptide that is released into the eye after trigeminal nerve stimulation, may be the cause. In rabbits, topical application of nitrogen mustard causes a rise in IOP which is blocked by capsaicin, a presumed substance P depletor. In the present study, six eyes of three cynomolgus monkeys underwent extracapsular lensectomies. After 2 to 3 months, capsaicin was administered by retrobulbar injection on one side of each animal, and vehicle on the contralateral side. One day later, Nd:YAG laser posterior capsulotomies were performed using 31 mJ (total energy) per eye. Diurnal IOP measurements were made before and after the retrobulbar injections and the capsulotomies. Ten weeks later, laser capsulotomies were repeated using 200 mJ/eye without pretreatment with any potential blockers. None of the six eyes, each undergoing two separate capsulotomies 10 weeks apart, showed a postoperative rise in IOP. These results demonstrate that the cynomolgus monkey is a poor model for studying IOP elevation that often occurs following Nd:YAG laser posterior capsulotomy.

Animals↗

PubMed1994

[Seasonal variation in intraocular pressure].

Generally speaking, physicians have the impression that intraocular pressure (IOP) in winter is higher than in summer, but it is very difficult to evaluate the difference between summer and winter IOP statistically, because the treatments of glaucoma patients are changed according to their conditions. We compared the winter and summer IOP of normal subjects and of several glaucoma patients who had no therapy or no change in therapy. The subjects were divided into four groups, i.e., 20 eyes of the normal group, 17 eyes of the ocular hypertensive group, 24 eyes of the primary open angle glaucoma group, and 52 eyes of the low tension glaucoma group. The difference in mean IOP between summer and winter were evaluated for each subject. In all groups, the mean difference in mean winter IOP was significantly higher. The ups and downs of IOP were greater in the ocular hypertensive group and the primary open angle glaucoma group than in the normal group and the low tension glaucoma group. These results suggest that the seasonal variation of IOP should be taken in consideration when treating glaucoma patients.

Adult↗

PubMed1992

Metipranolol-induced adverse reactions: II. Loss of intraocular pressure control.

This paper reviews the behaviour of intraocular pressure (IOP) in glaucomatous eyes treated with metipranolol with and without drug-induced adverse reactions (ADRs). Two hundred and forty seven patients with open angle glaucoma who were receiving the three different strengths of metipranolol (0.1%, 0.3%, and 0.6%) in our Department and the 7 patients who participated in the metipranolol rechallenge trial were included in this study. Out of the 247 patients, there were 52 eyes of 29 patients who showed 78 episodes of ADRs associated with metipranolol. Forty five of these 78 episodes (57.6%) were associated with loss of IOP control. Two of the 7 eyes treated with metipranolol in the rechallenge trial showed loss of IOP control, 1 of them without any signs of ocular inflammation. We further studied all the glaucomatous eyes controlled with metipranolol 0.6% only and 22 eyes were identified with loss of IOP control but without recognisable signs or symptoms of ADR. Five other eyes in this group later developed metipranolol-induced ADRs. The possible pathophysiological mechanisms for the loss of IOP control are discussed and it is suggested that the active drug, metipranolol, could be directly implicated.

Eye Diseases↗

PubMedDate not supplied

Ketamine and intraocular pressure in children.

The effect of ketamine on intraocular pressure (IOP) was studied in 10 children. Control IOP values were determined prior to induction of anesthesia, following premedication with atropine alone or in combination with pentobarbital and meperidine. After the IM injection of 8 mg/kg of ketamine, the IOP was determined at 5, 10, 15, and 20 minutes. Mean (+/- SD) IOP values before and after ketamine were 22.2 +/- 4.8 and 16.7 +/- 3.3 torr (p less than 0.001), respectively. The authors believe that the reduction in IOP was not due to ketamine, per se, but rather to lack of patient relaxation and cooperation during control measurements. At the end of 20 minutes, a second dose of ketamine, this time 1 mg/kg IV, was given and measurements were repeated at the same intervals. In 5 patients, the effects on IOP of d-tubocurarine, endotracheal intubation, and N2O inhalation also was evaluated. A significant increase (6.7 torr) in IOP was observed only after endotracheal intubation. The authors conclude that ketamine does not raise IOP in the healthy pediatric patient and, therefore, can be used for ophthalmic procedures requiring sedation or anesthesia.

Anesthesia, Inhalation↗

PubMed2000

Evidence that a gender difference in intraocular pressure is present from childhood.

Routine assessment of intraocular pressure (IOP) is usually confined to the clinical population aged over 40 years, i.e., to those individuals considered to be most at-risk of developing glaucoma. Published IOP data collected from assumed non-glaucomatous adult subjects have shown a gender difference in this parameter, with human females recording a consistently higher value than age-matched males. A recent study has also demonstrated that a diurnal variation in IOP can be recorded in adults across normal consulting hours. IOP material is presented here, as collected in the early afternoon (14.00-14.59 hours) from n = 140 school children aged > or = 9 < 12 years. It is complemented by previously published data, also recorded between 14.00-14.59, from n = 100 middle-aged adults aged 40-59 years, and n = 102 mature adults aged over 60 years. Analysis of these three data sets indicates that a non-statistically significant gender difference in mean IOP (female > male) is present from childhood; it also suggests that, for either gender, the absolute mean level of IOP remains little altered from childhood into and throughout adulthood. However the physiological basis for these observations remains obscure.

Adult↗

PubMed2002

Retinal nerve fiber layer thickness changes after an acute increase in intraocular pressure.

PURPOSE: To determine whether the increase in intraocular pressure (IOP) for 45 seconds during laser in situ keratomileusis (LASIK) suction can induce a decrease in retinal nerve fiber layer thickness (RNFLT) assessed by a confocal scanning laser polarimeter. SETTING: Jules Gonin Hospital, University of Lausanne, Lausanne, Switzerland. METHODS: Eleven normal volunteers were enrolled in the study. The optic disc of each eye was analyzed by the GDx(R) Nerve Fiber Analyzer (Laser Diagnostic Technologies, Inc.), version 1.0.14. Using the standard circle that appears as a 10-pixel green circle on the GDx display, the system assessed the RNFLT at 1.75 disc diameter from the outer edge of the optic nerve head. To further evaluate the possible retinal nerve fiber layer (RNFL) loss, the 360-degree circumference was divided into 36 segments measuring 10 degrees each and the RNFLT was calculated for each sector. All subjects had a GDx assessment before 100 mm Hg ocular compression of 1 eye for 45 seconds and then 2 minutes and 1 month after compression. RESULTS: Before compression, the mean RNFLT was 69.09 microm +/- 10.96 (SD); it was 69.27 +/- 10.98 microm after 2 minutes and 67.00 +/- 10.58 microm after 1 month. No statistically significant difference was found between the before and after measurements. CONCLUSION: A 45-second acute increase in IOP, such as during LASIK suction, did not decrease the RNFLT in normal eyes.

Adult↗

PubMed2005

Long-term physiologic changes of intraocular pressure: a 10-year longitudinal analysis in young and middle-aged Japanese men.

OBJECTIVE: Although the intraocular pressure (IOP) is the most important factor related to the onset and progression of glaucoma, there is little evidence on long-term aging effects on IOP. This article examines the changes of IOP over 10 years in normal eyes to assess physiologic changes related to aging. DESIGN: Population-based long-term longitudinal study. STUDY POPULATION AND OBSERVATION PROCEDURE: Two thousand nine hundred eighty-seven Japanese male aircraft crew members underwent IOP measurement by Goldmann apparatus and received physical and complete ophthalmologic examinations every year for 10 years. A total of 2330 healthy persons (21-49 years; mean age, 35.9+/-6.8 [standard deviation]) who had no history of treatment for ophthalmic diseases, current illnesses, and no missing data for 10 consecutive years were analyzed. MAIN OUTCOME MEASURES: For analysis of the longitudinal index (trend), the linear regression coefficients for 11 points of measurement were determined. Ophthalmologic and physiologic factors affecting the 10-year mean values and a trend of IOP were examined by multivariable linear regression analysis. RESULTS: Intraocular pressure tended to decrease with age in all age groups. The mean linear regression coefficient (right eye/left eye) = -0.076/-0.060 (95% confidence interval [CI]: (-0.094 to -0.057)/(-0.078 to -0.041), -0.073/-0.060 [95% CI: (-0.084 to -0.062)/(-0.071 to -0.049)], and -0.060/-0.050 [95%CI: (-0.075 to -0.046)/(-0.064 to -0.036)] (mmHg/year) in the 20s, 30s, and 40s, respectively). In investigating correlations between the 10-year mean values of IOP and factors examined in this study, multivariate analysis showed a significantly inverse correlation with spherical power (partial regression coefficient [B] = -0.155/-0.144) and positive correlation with esophoria (B = 0.536/0.521), systolic blood pressure (B = 0.021/0.022), heart rate (B = 0.024/0.024), and hematocrit (B = 0.041/0.043) with IOP. The trend of IOP was significantly positively associated with the trends of systemic factors: body mass index (BMI) (B = 0.117/0.119), blood pressure (systolic) (B = 0.020/0.020), and hematocrit (B = 0.057/0.045), but not with any ophthalmologic factor. CONCLUSIONS: The long-term observation clearly demonstrated that, in normal eyes, the IOP decreased with aging. The IOP value was negatively associated with spherical power and positively with esophoria, blood pressure, heart rate, and hematocrit. The change of IOP could be affected mainly by the change of body mas index, blood pressure, and hematocrit.

Adult↗

PubMed2005

Level of disagreement between Proview phosphene tonometer and Goldmann applanation tonometer intraocular pressure readings.

PURPOSE: To evaluate the agreement of intraocular pressure (IOP) readings obtained with the Proview phosphene tonometer and those obtained by Goldmann applanation tonometry as well as the effect of regular use of the Proview on patients' anxiety about their glaucoma. METHODS: One hundred thirty-five consecutive patients with glaucoma, 35 designated as controls, were enrolled in a 10-month randomized prospective clinical trial. The study patients but not the controls used the Proview outside the office. At office visits IOP was measured by an ophthalmologist with the Goldmann applanation tonometer (GAT) as well as by examiners and patients using the Proview. Patients in the treatment group (n = 100) were asked to measure and record their IOP at home as well. Using ANOVA, we examined the relationship between demographic variables and the level of agreement between the Proview readings and those measured by GAT at the final office visit. All participants also were asked to complete a questionnaire regarding their anxiety about their IOP at the baseline and final office visits. The primary outcome measure was the level of agreement of the Proview measurements with those obtained by GAT. Secondary outcome measures included patients' anxiety about their glaucoma. RESULTS: The absolute mean difference between GAT and Proview readings at the final visit was 3.5 +/- 2.9 mm Hg (median, 2.8 mm Hg). The treatment group reported significantly less anxiety about their glaucoma after 4 to 6 weeks of using the Proview (P = .024). CONCLUSIONS: There was considerable discrepancy between Proview and GAT readings. However, regular use of the Proview tonometer significantly reduced patients' anxiety about their glaucoma.

Adolescent↗

PubMed2006

The relationship among race, iris color, central corneal thickness, and intraocular pressure.

PURPOSE: Central corneal thickness (CCT) influences applanation intraocular pressure (IOP) measurement. The present study sought to determine whether iris color might represent a qualitative surrogate for CCT or race, and therefore differential risk for elevated IOP and, consequently, developing glaucoma. METHODS: Eligible patients included those with best-corrected visual acuity (BCVA) better than 20/40 and who had not worn contact lenses within 24 hours. Exclusion criteria were prior ophthalmic surgery, topical ocular or systemic medication that would influence IOP, previous ocular inflammatory conditions, or current treatment for ophthalmic treatment. Data collection included demographic (name, date of birth, race), BCVA, and iris color. Iris color was judged according to a purpose-developed chart (white: blue, green, brown or black: brown) and patients were assigned to one of four groups. Goldmann applanation tonometry and pachymetry measurements were performed consecutively. To attain a power of 90% to find a difference of 40 microm with alpha < 0.05, we examined at least 14 subjects (28 eyes) for each group. RESULTS: Comparing pachymetry measurements among iris colors revealed no statistically significant difference among the three groups of whites: blue (552 microm), green (552 microm), and brown (562 microm). The same held true when comparing IOP and CCT-adjusted IOP with iris color: blue-15.2, 15.1, green-15.4, 15.2, and brown-14.7, 14.0. When comparing CCT between whites and blacks, CCT was significantly thinner in blacks (533 microm), whether evaluating all whites (555 microm, p = 0.03) or comparing only the brown-iris white group with the black group (562 microm vs. 533 microm, p = 0.03). Mean CCT-adjusted IOP was barely significantly different between whites (14.8) and blacks (16.7) (p = 0.04). CONCLUSION: These results suggest that iris color is not associated with CCT and apparently iris color does not influence measured IOP. We were able to establish a relationship between race and IOP when adjusting IOP for CCT. Our data show a significantly higher CCT-adjusted IOP for blacks than whites demonstrating a racial difference in CCT-corrected IOP.

Adolescent↗

PubMed1994

Effects of endothelin-1 on intraocular pressure and aqueous humor dynamics in the rabbit eye.

The effects of endothelin-1 (ET-1) on intraocular pressure (IOP) and aqueous humor dynamics were studied in the rabbit eye. The intravitreal injection of 10(-5) M ET-1 (20 microliters) produced a biphasic IOP response consisting of an initial rise of 1 to 2 hours in duration, and a subsequent prolonged reduction lasting for more than 96 hours. Aqueous humor dynamics were determined 24 hours after the 10(-5) M ET-1 injection. Aqueous humor formation, measured fluorophotometrically, was decreased by 58%. Total outflow facility increased by 94%, according to measurement by two-level constant pressure perfusion. The change of uveoscleral outflow determined by fluorescein-dextran perfusion was not significant. The decrease in aqueous flow and the increase in total facility accounted for most of the IOP reduction after the ET-1 injection. Endothelin, which is endogenously present in the eye, may play a role in the regulation of intraocular pressure.

Animals↗

PubMed2005

The influence of intraocular pressure on the transscleral diffusion of high-molecular-weight compounds.

PURPOSE: To evaluate the effects of intraocular pressure on the permeability of the human sclera to high-molecular-weight compounds. METHODS: Human transscleral permeability to FITC-albumin (70 kDa) and 70-kDa and 150-kDa FITC-dextran was determined at transscleral pressures from 0 to 60 mm Hg. For each compound at each pressure, six to eight experiments were performed. Scleral sections were mounted in a two-compartment perfusion chamber. Temperature was maintained at 37 degrees C. Fractions of choroidal perfusate were collected, and fluorescence was measured with a spectrofluorometer. From these data, scleral permeability K(trans) (in centimeters per second) was calculated. RESULTS: Permeability to FITC-albumin was decreased by approximately one half when pressure was elevated from 0 to 30 mm Hg (P < 0.05). No significant differences in permeability to 70-kDa FITC-dextran were observed at pressures from 0 to 60 mm Hg. Permeability to 150-kDa FITC-dextran decreased by a little more than one half when transscleral pressure was raised from 0 to 15 mm Hg and was approximately 10 times lower at 60 mm Hg than at 0 mm Hg (P < 0.01). CONCLUSIONS: Human sclera was permeable to compounds with a molecular weight of up to 150 kDa at transscleral pressures ranging from 0 to 60 mm Hg. Transscleral diffusion was relatively unaffected by the pressure gradient, although for 150-kDa FITC-dextran at 60 mm Hg a 10-fold decrease was observed compared with that at 0 mm Hg. These experiments suggest that high-molecular-weight compounds (e.g., immunoglobulins and oligonucleotides) could be effectively delivered transsclerally to the intraocular tissues under circumstances of physiological or elevated intraocular pressure.

Dextrans↗

PubMed1998

Factors associated with retrobulbar hemodynamic measurements at variable intraocular pressure.

PURPOSE: The authors determine those clinical variables that influence color Doppler measurements at spontaneous and artificially elevated intraocular pressure (IOP). METHODS: Color Doppler peak systolic velocity (PSV), end diastolic velocity (EDV), and Pourcelot ratio (PR) were measured in the central retinal artery (CRA) and posterior ciliary artery (PCA) at spontaneous IOP and artificially elevated IOP of 30 mmHg, 40 mmHg, and after release of suction-induced pressure elevation in 33 eyes of 33 patients. Those with varied ocular and systemic backgrounds were enrolled to facilitate determination of relationships between these hemodynamic measures at elevated IOP and multiple patient characteristics including the degree of glaucomatous damage. RESULTS: Intraocular pressure elevation reduced velocity and increased Pourcelot ratio in both vessels at 30 mmHg and at 40 mmHg. On release of suction-induced IOP elevation, velocity increased above the velocity measured at spontaneous IOP (hyperemic response). Blood pressure consistently correlated with velocity and with PR in both vessels at all IOP levels tested. The change in velocity with IOP challenge decreased with age, and increased with vertical cup-to-disc ratio in the CRA, and decreased with ocular beta-blocker use in the PCA. CONCLUSION: Because blood pressure and age relate to velocity, studies comparing cohorts with respect to disease or drug effects should be matched for these variables. While it is clear that the presence of glaucoma and use of beta-blockers correlate with vascular parameters, from this study it is not possible to distinguish pathogenic factors from pathologic results of disease or drug effects.

Adrenergic beta-Antagonists↗

PubMed1999

Effect of dorzolamide and latanoprost on intraocular pressure after small incision cataract surgery.

PURPOSE: To evaluate the effect of dorzolamide 2% and latanoprost 0.005% on intraocular pressure (IOP) after small incision cataract surgery. SETTING: Department of Ophthalmology, University of Vienna, Vienna, Austria. METHODS: This prospective study comprised 102 eyes of 102 consecutive patients scheduled for small incision cataract surgery. The patients were assigned preoperatively to 1 of 3 groups of 34 each: dorzolamide, latanoprost, and control (no treatment). One drop of the assigned medication was instilled immediately after surgery. Intraocular pressure was measured preoperatively and 6 and 20 to 24 hours postoperatively. RESULTS: Six hours after surgery, the mean increase in IOP was 1.9 mm Hg +/- 3.9 (SD) in the dorzolamide group (P = .004 versus control), 2.2 +/- 3.0 mm Hg in the latanoprost group (P = .005 versus control), and 4.8 +/- 5.2 mm Hg in the control group. Twenty to 24 hours postoperatively, IOP decreased a mean of -0.9 +/- 3.5 mm Hg in the dorzolamide group (P = .012 versus control) and increased a mean of 0.3 +/- 3.6 mm Hg in the latanoprost group (P = 0.24 versus control) and 1.3 +/- 4.2 mm Hg in the control group. One eye in the dorzolamide group, 1 eye in the latanoprost group, and 4 eyes in the control group had an IOP of 30 mm Hg or higher 6 hours postoperatively. CONCLUSION: Six hours postoperatively, dorzolamide and latanoprost were effective in reducing the IOP increase after small incision cataract surgery; however, at 20 to 24 hours, only dorzolamide was effective. Neither drug prevented IOP spikes of 30 mm Hg or higher.

Aged↗

PubMed2005

Dorzolamide influences the autoregulation of major retinal vessels caused by artificial intraocular pressure elevation in patients with POAG: a clinical study.

PURPOSE: The study investigated whether dorzolamide influences the autoregulatory behavior of major retinal arterioles in glaucoma patients via a moderate perfusion pressure reduction. METHODS: The study included one eye each of 12 untreated patients with a primary open-angle glaucoma (POAG) (age 60.8 +/- 8.3, IOP 22.3 +/- 6.5 mmHg). Changes in the diameter of a retinal artery segment before (120 s), during (100 s), and after (380 s) artificial IOP elevation to 38 mmHg for 100 s were recorded continuously by means of a Retinal Vessel Analyzer. The measurement was repeated after 4-week treatment with dorzolamide eye drops t.i.d. RESULTS: Ocular perfusion pressure (mmHg) was reduced by the intraocular pressure (IOP) elevation from 58 (+/- 10) to 41 (+/- 11) in the pretreatment examination and from 60 (+/- 8) to 40 (+/- 8) posttreatment (differences between the examinations n.s.). Before IOP elevation, the arterial diameter was found to be +1.7 +/- 3.5% greater in the posttreated eyes than in the pretreated eyes (p < 0.02). During IOP elevation, the arterial diameter decreased by -1.8% +/- 3.8 in the pretreated eyes, whereas dilatation by +1.4% +/- 2.5 was observed in the posttreated eyes (p = 0.02). At the end of the observation period following IOP elevation, the vessel diameter in the pretreated eyes had increased by +1.8% +/- 4.2, whereas in the posttreated eyes it had decreased by -1.7% +/- 3.0. On average, dorzolamide reduced IOP by -5.6 mmHg (p = 0.001). CONCLUSIONS: The arterial diameter dilatation during IOP elevation in dorzolamide-treated eyes could be an accelerated counter-regulation on the induced elevated IOP and could constitute an additional therapeutic effect.

Aged↗

PubMed2006

Effects of corneal thickness, corneal curvature, and intraocular pressure level on Goldmann applanation tonometry and dynamic contour tonometry.

PURPOSE: To compare the measurements of intraocular pressure (IOP) with Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT) and the effects of central corneal thickness (CCT), corneal curvature, and level of IOP on these methods. DESIGN: Cross-sectional population-based study. PARTICIPANTS: From the Los Angeles Latino Eye Study, 2157 participants of primarily Mexican ancestry. METHODS: Average GAT measurements were compared to DCT, and both were examined with respect to CCT (< or =500, 501-550, 551-600, >600 microns), corneal curvature (<42, 42-46, >46 diopters), and level of IOP (0-10, 11-20, >20 mmHg). MAIN OUTCOME MEASURES: Mean GAT and DCT IOP levels were compared for the entire population, and then trends for the CCT, curvature, and IOP groupings were analyzed. The magnitude of the difference of GAT minus DCT was compared for these different strata, with special attention to a difference of +/- 3 mmHg or greater, which was defined as clinically significant. RESULTS: Mean IOP for the entire population by GAT was significantly lower (14.4+/-3.2 mmHg) compared with DCT (16.0+/-3.6; P<0.0001). Both GAT and DCT IOP levels were lowest for thin CCT and increased stepwise with increasing CCT, but this difference was more pronounced with GAT than DCT (P<0.0001 and P = 0.0012, respectively). The difference between GAT and DCT was largest for thin CCT and decreased for thicker CCT (P<0.0001). After adjusting for CCT, the corneal curvature affected IOP measured by DCT (P = 0.02) but not GAT (P = 0.3) such that mean DCT IOP increased with increasing corneal curvature. After adjusting for the CCT effect on IOP and stratifying by DCT IOP groups, the greatest difference between GAT and DCT was seen in the lowest IOP group (3.55+/-3.1), became negative in the intermediate group (-1.86+/-2.60), and was most negative in the highest IOP group (-3.88+/-3.3; P<0.0001). CONCLUSIONS: Intraocular pressure measured by GAT was consistently lower when compared with DCT, and this difference was greatest with thinner CCT. Dynamic contour tonometry was also less affected by variations in CCT. Corneal curvature affected IOP measurements with DCT but not GAT, but this effect was less than the CCT effect on GAT. Goldmann applanation tonometry tended to underestimate IOP at higher levels and overestimate it at lower IOP levels when compared to DCT.

Adult↗

PubMed1983

Retinal pigment epithelium: pattern of proliferative activity and its regulation by intraocular pressure in postnatal rats.

The postnatal proliferative activity of retinal pigment epithelium (RPE) cells and its dependence on intraocular pressure were studied using [3H]thymidine and [14C]thymidine autoradiography in normal and experimentally induced microphthalmic pigmented rats. The regulation of RPE growth by intraocular pressure was shown to involve the control of the number of binucleated cells by means of stimulation of cell entry into the S phase of the cell cycle. Binucleated cells in the rat RPE are formed by acytokinetic mitoses between days 2 and 9. The significance of the postnatal proliferation and formation of binucleated cells in the RPE is discussed in terms of the specificity of the G2 phase for melanotropic hormone action on RPE differentiation.

Aging↗