Intraocular Pressure Pattern Research Articles

Pattern of intraocular pressure reduction following laser trabeculoplasty in open-angle glaucoma patients: comparison between selective and nonselective treatment

ObjectiveTo compare the pattern of intraocular pressure (IOP) reduction following selective laser trabeculoplasty (SLT) versus argon laser trabeculoplasty (ALT) in open-angle glaucoma (OAG) patients, and to investigate the ability of initial IOP reduction to predict mid-term success.MethodsA prospective, nonrandomized, interventional case series was carried out. Consecutive uncontrolled OAG glaucoma patients underwent SLT or ALT; the same preoperative medical regimen was maintained during follow-up. Data collected included age, type of OAG, pre- and postoperative IOP, number of glaucoma medications, and surgical complications. Post-treatment assessments were scheduled at day 1 and 7 and months 1, 3, and 6.ResultsA total of 45 patients (45 eyes) were enrolled [SLT group (n = 25); ALT group (n = 20)]. Groups were similar for age, baseline IOP, and number of glaucoma medications (P ≥ 0.12). We found no significant differences in mean IOP reduction between SLT (5.1 ± 2.5 mmHg; 26.6%) and ALT (4.4 ± 2.8 mmHg; 22.8%) groups at month 6 (P = 0.38). Success rates (IOP ≤ 16 mmHg and IOP reduction ≥25%) at last follow-up visit were similar for SLT (72%) and ALT (65%) groups (P = 0.36). Comparing the pattern of IOP reduction (% of IOP reduction at each visit) between groups, we found a greater effect following SLT compared with ALT at day 7 (23.7% ± 13.7% vs 8.1% ± 9.5%; P < 0.001). No significant differences were observed at other time points (P ≥ 0.32). Additionally, the percentage of IOP reduction at day 7 and at month 6 were significantly correlated in the SLT group (R2 = 0.36; P < 0.01), but not in the ALT group (P = 0.89). Early postoperative success predicted late success in most SLT cases (82%). No serious complications were observed.ConclusionAlthough mid-term results suggest SLT and ALT as effective and equivalent alternatives, a greater initial IOP reduction was observed following SLT. In addition, the initial IOP reduction was a good predictor of mid-term success in patients undergoing SLT, but not ALT.

DIURNAL INTRAOCULAR PRESSURE PATTERNS ARE NOT REPEATABLE IN THE SHORT TERM IN HEALTHY INDIVIDUALS

DIURNAL INTRAOCULAR PRESSURE PATTERNS ARE NOT REPEATABLE IN THE SHORT TERM IN HEALTHY INDIVIDUALS

Short-Term Repeatability of Diurnal Intraocular Pressure Patterns in Glaucomatous Individuals

To evaluate the short-term repeatability of diurnal intraocular pressure (IOP) patterns in eyes with primary open-angle glaucoma (POAG). Observational cohort study. Forty-seven subjects with treated POAG. Subjects underwent assessment of IOP using Goldmann tonometry every 2 hours from 0800 to 2000 on 2 visits 1 week apart. Intervisit agreement of IOP by time point and of IOP change between time points was assessed using intraclass correlation coefficients (ICCs). Diurnal IOP patterns. Between-visit agreement of IOP values at each time point was generally fair to good, with ICCs ranging from 0.45 to 0.71 in right eyes and from 0.51 to 0.71 in left eyes. Between-visit agreement of IOP change over time periods between time points was uniformly poor, with ICCs ranging from -0.08 to 0.38 in right eyes and from -0.11 to 0.36 in left eyes. Treated POAG patients do not manifest a repeatable diurnal IOP pattern from day to day when measured by Goldmann tonometry. Measurement of single-day IOP variation poorly characterized short-term IOP variation.

Circadian Variations in Intracranial Pressure and Translaminar Pressure Difference in Sprague-Dawley Rats

To study the circadian (24-hour) change in intracranial pressure (ICP) in conscious, freely moving rats and to project the circadian change in translaminar pressure difference. Telemetric pressure transmitters were implanted to monitor ICP in the lateral ventricle in nine light-dark-entrained Sprague-Dawley rats. ICP and locomotor activity data were collected. The mean results for the 12-hour light period and the 12-hour dark period were compared. The light-dark change in ICP was also determined in six rats under an acute 24-hour constant dark condition. The circadian translaminar pressure difference was projected based on the ICP data and the previously established circadian pattern of intraocular pressure (IOP). Under the standard light-dark condition, the hourly average ICP was relatively constant (7.47-10.90 mm Hg). The light-dark ICP difference was -0.11 ± 1.45 mm Hg (mean ± SD, P = 0.823), whereas the locomotor activity was significantly higher during the dark period (P < 0.01). Under the acute constant dark condition, the subjective light-dark ICP difference remained small. Compared with a significant light-dark IOP elevation of 5.15 ± 4.47 mm Hg (P = 0.037) in rats housed under the same laboratory conditions, the light-dark ICP variation was considered minimal. The translaminar pressure difference was projected to be 5.26 mm Hg higher in the dark period (mean, 17.10 mm Hg) than in the light period (mean 11.84 mm Hg). There is no significant circadian ICP variation in Sprague-Dawley rats. The translaminar pressure difference is projected to be higher during the dark period because of the change in IOP.

Diurnal Intraocular Pressure Patterns are Not Repeatable in the Short Term in Healthy Individuals

To evaluate the short-term repeatability of diurnal intraocular pressure (IOP) patterns in eyes of subjects without glaucoma. Observational cohort study. Forty healthy subjects without glaucoma. Subjects underwent 12-hour diurnal IOP assessment sessions from 8:00 am to 8:00 pm on 2 visits 1 week apart. Intraocular pressure was assessed by Goldmann applanation tonometry. An analysis was performed to determine the agreement of individual diurnal IOP patterns from the first visit to the second visit. The intraclass correlation coefficient (ICC) was used to analyze both agreement of IOP values at each time point between visits and IOP change over periods between time points between visits. Diurnal IOP patterns. Between-visit agreement of IOP values at each time point generally was fair to good, with ICCs ranging from 0.37 to 0.62 in right eyes and from 0.35 to 0.71 in left eyes. Between-visit agreement of IOP change over time between time points was uniformly poor and often below that expected by chance alone, with ICCs ranging from -0.25 to 0.15 in right eyes and from -0.40 to 0.22 in left eyes. Eyes of healthy individuals do not manifest a sustained and reproducible diurnal IOP pattern when measured by Goldmann tonometry. A single-day assessment of IOP incompletely characterizes the diurnal IOP pattern.

Prevalence of glaucoma suspects and pattern of intra-ocular pressure (IOP) distribution in Ahoada-East local government area of Rivers State

Background: Glaucoma is the commonest cause of irreversible blindness in the world. Some glaucoma patients start out as glaucoma suspects for years. Aim: To determine the prevalence of glaucoma suspects and pattern of intra-ocular pressure distribution in glaucoma suspects. Methods: This survey was carried out in Ahoada-East local government area (LGA) of Rivers State. The study took place in 6 communities in the LGA. Multi-stage sampling technique was used to select the study sample which consisted of 960 persons drawn from the 6 communities. Ocular examination was carried out and consisted of visual acuity, basic eye examination and direct funduscopy. Subjects with pathologically cupped discs or cup/disc asymmetry of ≥ 0.2 had their intra-ocular pressures (IOP) measured. Data was recorded primarily on the WHO/PBL eye examination form and entered into Epi-Info version 6 for analysis. Results: A total of 34 subjects who had vertical cup/disc ratio > 0.5 had their intra-ocular pressures measured. Of this, 23 were glaucoma suspects. There were 15 males (65.2%) and 8 females (34.8%) and those aged 40-79 years made up 69.6% of the study sample. Most eyes (97.8%) had normal intra-ocular pressures (10-21mmHg) while one had an IOP of 8 mmHg. Out of 866 subjects, 23 were glaucoma suspects giving a prevalence of 2.7%. Conclusion: Since glaucoma is a leading cause of irreversible blindness in the world, the availability of data on glaucoma suspects, the type of glaucoma they have and the age groups most at risk would facilitate early diagnosis and follow up thus preventing unnecessary blindness from glaucoma. Keywords: Glaucoma suspects, Prevalence, IOP distribution

Circadian Blood Pressure and Intraocular Pressure Patterns in Normal Tension Glaucoma Patients with Undisturbed Sleep

PurposeTo investigate and compare the circadian pattern of blood pressure (BP), intraocular pressure (IOP) and mean ocular perfusion pressure (MOPP) while experiencing undisturbed sleep in normal-tension glaucoma (NTG) and non-glaucoma control patient groups.MethodsTwenty-four eyes from 24 patients diagnosed with NTG and 22 eyes from 22 control group patients were enrolled. Systolic BP, diastolic BP and IOP were measured every two hours except for the period of time from 1 AM to 7 AM in the NTG group and from 11 PM to 7 AM in the control group over a one-day period. IOP and hemodynamic parameters were then compared between the two groups. NTG patients were subdivided according to the degree of morning BP dip and IOP, and hemodynamic parameters and visual field indices (mean deviation and pattern standard deviation) were also compared among these subgroups.ResultsThere were no significant differences in mean systolic BP, mean diastolic BP and mean arterial pressure (MAP) between the NTG and the control groups. The NTG group showed a significantly large morning BP dip compared to the control group (7.1±4.2% vs. 3.8±3.4%, p=0.022). However, there were no significant differences in mean or fluctuation of MOPP between the two groups. Morning over-dippers showed significantly large MAP and MOPP fluctuations compared to non-dippers and dippers, while there were no significant differences in visual field indices among the three subgroups.ConclusionsNTG patients showed significant morning BP dips compared to the control group. The marked morning BP dip was associated with significantly large MAP or MOPP fluctuations but was not associated with visual field indices.

Visual Acuity and Intraocular Pressure after Descemet's Stripping Endothelial Keratoplasty in Eyes with and without Preexisting Glaucoma

(1) To characterize the pattern of intraocular pressure (IOP) changes after Descemet's stripping endothelial keratoplasty (DSEK) in patients without preexisting glaucoma and in those with preexisting glaucoma, with and without prior glaucoma surgery. (2) To compare vision and IOP outcomes among the 3 groups. A retrospective chart review. A total of 805 DSEK cases performed in 641 patients by a single surgeon from December 2003 to August 2007 were available in the database. Only the first-treated eye of each patient with at least 1-year follow-up was included. Four hundred cases qualified: 315 eyes had no glaucoma (C); 64 eyes had glaucoma with no previous glaucoma surgery (G); and 21 eyes had prior glaucoma surgery (GS). Eyes with preexisting retinal problems were included in the analysis. Data analysis included calculation of incidence of postoperative IOP elevation. The study criteria for postoperative IOP elevation were IOP > or =24 mmHg or IOP increase > or =10 mmHg from baseline. Kruskal-Wallis test was used to compare visual acuity (VA) and IOP among the 3 groups preoperatively and at 1-, 3-, 6-, and 12-month postoperative visits. Visual acuity (Snellen) and IOP (millimeters of mercury). The incidence of postoperative IOP elevation by the study criteria was 35%, 45%, and 43% for groups C, G, and GS, respectively. Elevated IOP was medically managed by initiating or increasing glaucoma medications or reducing steroids in 27%, 44%, and 38% of the patients in groups C, G, and GS, respectively. A subsequent glaucoma procedure was performed in 0.3%, 5%, and 19% of patients in groups C, G, and GS, respectively. Only the control group had statistically significant IOP elevation at 12 months (median increase of 2 mmHg) when compared with baseline (P<0.0001). All 3 groups had statistically significant improvement in vision at 12 months when compared with baseline (12-month median VA = 20/40 for C and G; and 20/50 for GS, P<0.0001). All groups had a substantial incidence of IOP elevation after DSEK. Close monitoring of IOP is warranted. In this cohort, preexisting glaucoma did not seem to have a negative effect on VA after DSEK. Proprietary or commercial disclosure may be found after the references.

Intraocular pressure measurements throughout the 24 h

This review summarizes the relationship of 24 h intraocular pressure (IOP) on the management of glaucoma. The 24 h IOP pattern demonstrates nocturnal elevation in the majority of individuals. Prostaglandin analogs and carbonic anhydrase inhibitors lower both diurnal and nocturnal IOPs. Timolol monotherapy and timolol add-on treatment to a prostaglandin analog does not lower IOP during the nocturnal period. Laser trabeculoplasty can reduce nocturnal IOP elevation in medically treated glaucoma patients, even in those without significant reduction of diurnal IOP. Though both IOP and central corneal thickness display a 24 h rhythm with peaks during the nocturnal period, there is no correlation between central corneal thickness and 24 h IOP variation in normals and glaucoma patients. Corneal biomechanical properties (corneal hysteresis and corneal resistance factor) remain relatively stable during the 24 h period and are not associated with 24 h IOP fluctuation. Antiglaucoma therapies differ in their ability to lower IOP throughout the 24 h day. The 24 h IOP pattern is independent of central corneal thickness, corneal hysteresis and corneal resistance factor.

Relationship of the 24-Hour Pattern of Intraocular Pressure with Optic Disc Appearance in Primary Open-Angle Glaucoma

To study the relationship between the 24-hour pattern of intraocular pressure (IOP) with optic disc appearance in primary open-angle glaucoma (POAG) patients. Observational clinical study. Seventy-five eyes of 45 POAG patients. Patients underwent 24-hour IOP assessment in a sleep laboratory. Two observers classified the optic disc appearance for each eye as either concentric or nonconcentric. The IOP measurements were obtained with the subjects in the supine and sitting positions during the diurnal period and in the supine position during the nocturnal period. The mean, peak, and trough IOP and IOP range (peak through trough) were calculated for the office-hour period (9 am to 4 pm), the diurnal period (7 am to 11 pm), the nocturnal period (11 pm to 7 am), and the 24-hour period. Further, the difference in supine and sitting IOP during the diurnal periods was calculated, and generalized estimating equations were used to compare IOP measurements in both groups. Diurnal and nocturnal IOP measurements. Forty eyes were classified as having concentric optic disc appearance and 35 eyes as having nonconcentric optic disc appearance. The mean nocturnal IOP was significantly greater in the concentric group (mean+/-standard deviation [SD], 24.0+/-3.8 mmHg) compared with the nonconcentric group (mean+/-SD, 21.9+/-1.9 mmHg; P = 0.004). Most IOP peaks of patients with the concentric optic disc appearance occurred during the nocturnal period, as opposed to the diurnal period of patients with the nonconcentric optic disc appearance. Concentric optic disc appearance may be associated with higher nocturnal IOP compared with nonconcentric optic disc appearance. The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Direct effect of light on 24-h variation of aqueous humor protein concentration in Sprague–Dawley rats

Sprague–Dawley rats 10–12 weeks of age were entrained to a standard light–dark cycle with lights turned on at 6 am and off at 6 pm. Variations of 24-h aqueous humor protein concentration were determined. Samples were taken every 4 h ( N = 10–14) under the standard light–dark condition at 8 pm, midnight, 4 am, 8 am, noon, and 4 pm. Under an acute constant dark condition, when lights were not turned on at 6 am, samples were collected at 8 am, noon, 4 pm, and 8 pm. Aqueous humor protein concentrations under the standard light–dark condition were found in the range of 0.305 ± 0.115 mg/ml (mean ± SD, N = 10) at midnight to 1.505 ± 0.342 mg/ml ( N = 14) at noon. The 3 light-phase protein concentrations were each higher than the 3 dark-phase concentrations. Aqueous humor protein concentrations at 8 am, noon, and 4 pm under the acute constant dark condition were each higher than the concentrations at 8 pm (after both 2 h and 26 h in the dark), midnight, and 4 am, demonstrating an endogenously driven 24-h pattern. At 8 am, noon, and 4 pm, protein concentrations were 56–147% higher when exposed to light. Intraocular pressure (IOP) was monitored using telemetry in separate groups of light–dark entrained rats under the standard light–dark condition and the acute constant dark condition. The 24-h IOP pattern was inverse to the 24-h pattern of aqueous humor protein concentration under the standard light–dark condition, and this IOP pattern was not altered by the acute constant dark condition. In conclusion, an endogenously driven 24-h variation of aqueous humor protein concentration occurred in Sprague–Dawley rats with higher concentrations during the light-phase than the dark-phase. This endogenous pattern of protein concentration was accentuated by a direct effect of light, which was unrelated to the 24-h pattern of IOP.

Effects of Aging on Corneal Biomechanical Properties and Their Impact on 24-hour Measurement of Intraocular Pressure

To study the effects of aging on corneal biomechanical properties and their impact on 24-hour measurement of intraocular pressure (IOP). Experimental study. Fifteen older volunteers with healthy eyes (age range, 50 to 80 years) were housed for one day in a sleep laboratory with a 16-hour diurnal or wake period and an eight-hour nocturnal or sleep period. Every two hours, sitting corneal hysteresis, corneal resistance factor, and IOP were measured. Central corneal thickness (CCT) was measured using an ultrasound pachymeter. Data were compared with previous observations in 15 healthy younger volunteers (age range, 20 to 25 years). Variations in 24-hour corneal hysteresis and corneal resistance factor were not significant in the older subjects, but there were time-dependent variations in CCT and IOP. The nocturnal CCT was thicker than the diurnal CCT, but the IOP difference between the diurnal and nocturnal periods was not significant. Cosine-fits of CCT and IOP showed synchronized 24-hour rhythms. The phase timing of CCT rhythm appeared significantly earlier than the phase timing of IOP rhythm. Compared with younger subjects, older subjects had a lower mean 24-hour corneal hysteresis and corneal resistance factor, but not a lower CCT. Phase timings of 24-hour rhythms of CCT and IOP were significantly delayed by aging. Aging may lower corneal hysteresis and corneal resistance factor, but neither parameter shows a significant 24-hour variation. Aging may not change CCT significantly, but can shift its 24-hour rhythm. The 24-hour IOP pattern in this group of older subjects is not an artifact resulting from a variation in corneal hysteresis, corneal resistance factor, or CCT.

The Effect of Sympathectomy on Circardian Rhythm of Intraocular Pressure in Rat

Purpose: The present study was undertaken to determine the 24-hour pattern of intraocular pressure (IOP), and to reveal the effect of unilateral decentralization on circardian rhythm of IOP in eyes of rats. Methods: Nine male Sprague-Dawley rats were exposed to a 12-hour light/dark cycle for 3 weeks. 24-hours IOP pattern was measured at six time points (8, 12, 16, 20, 24, and 4 circardian time) by Tonopen XL tonometer in awake state. After unilateral sympathectomy (cervical ganglionectomy), IOP measurements were performed at the same time points on post-operation 1, 2, 3, and 4 weeks. Results: 24-hour IOP pattern of rats showed a rhythmic pattern that appeared to be sinusoidal with 12-hour light/dark cycle. IOPs were low during the light phase and high during dark phase. After unilateral sympathectomy, the circardian rhythm of IOP was maintained in control eyes. But in sympathecotmized eyes, the circardian thythm of IOP was loss. Conclusions: These results show that sympathetic nervous systems contribute to the circardian rhythm of IOP in rats.

Circadian rhythm of intraocular pressure in healthy subjects and glaucoma patients

Abstract Purpose: Intraocular pressure (IOP) varies and depends on many factors. Intraocular pressure variations throughout the nycthemeron (the full 24‐period of a night and a day) are the most interesting for studying. Methods: With present techniques, it is impossible to measure continuously without waking the subject up. Thus, IOP must be hourly measured during 24 hours with a portable tonometer which allows short measurements in any posture, without requiring the subjects or patients to rise during the night. Results: Intraocular pressure depends on a nyctohemeral rhythm, being higher at night than during the day in healthy subjects, with a nocturnal peak value (acrophase). In the same normal individual, several 24‐hour monitorings are identical. Each individual has his own 24‐hour pattern of IOP.In glaucoma patients, however, the 24‐hour rhythm of IOP was reversed, with values being higher during the day (a midday peak in IOP) than during the night. Conclusions: The time course of the nyctohemeral curve of intraocular pressure is considered to play a role in the prognosis of glaucoma and allows to classify the type of glaucoma (POAG, NTG). Lowering of IOP is still the only option that is available for treating patients with glaucoma. Variations encountered in the individual’s nyctohemeral IOP pattern must be taken into consideration to manage the most efficient treatment.

Awareness of Incident Open-angle Glaucoma in a Population Study: The Barbados Eye Studies

To evaluate factors related to awareness of incident open-angle glaucoma (OAG) in the Barbados Eye Studies. Cohort study with 81% to 85% response rate over 9 years. Four thousand three hundred fourteen participants of African descent, 40 to 84 years old at baseline. Standardized study visits included an interview on demographic, medical, health care, and other factors; various ophthalmic measurements; fundus photography; and comprehensive ophthalmologic examinations for those referred. Definite OAG was defined by both visual field and optic disc criteria after ophthalmologic confirmation, regardless of intraocular pressure (IOP). Definite incident participants without prior OAG diagnosis/treatment were considered unaware. Logistic regression analyses evaluated factors associated with OAG unawareness. Results were expressed as odds ratios (ORs) with 95% confidence intervals (CIs). Over 9 years, 125 participants newly developed definite OAG, of whom 53% were previously unaware. At baseline, the unaware group had significantly lower mean IOP (OR, 0.86; 95% CI, 0.79-0.94) and more hyperopia (OR, 2.69; 95% CI, 1.08-6.69) than those aware. Most unaware and aware participants had > or =2 medical care visits in the previous year (72.7% vs. 83.1%). However, those in the unaware group sought eye care less frequently than those aware (last visit in preceding year, 33.4% vs. 64.4%); these visits were mainly for eyeglasses (71.4% vs. 12.5%), with most having glaucoma tests only during study visits (72.7% vs. 37.3%). The unaware group reported more visits to opticians/optometrists than to private ophthalmologists (OR, 4.20; 95% CI, 1.00-17.66) and fewer visits to a public ophthalmologic clinic (OR, 0.18; 95% CI, 0.04-0.86). Over half of participants with incident OAG were unaware of their diagnosis. Unawareness was related to lower IOP, hyperopia, and eye care utilization patterns. Although persons in the unaware group had regular visits for medical care, visits for eye care and OAG testing were limited. Unawareness was 4 times more likely when opticians/optometrists were the regular eye care source, compared with private ophthalmologists, and about 80% less likely with a public ophthalmologic source. These findings highlight the high frequency of undiagnosed OAG and importance of comprehensive examinations in disease detection.

Comparison of Localized Retinal Nerve Fiber Layer Defects Between a Low-teen Intraocular Pressure Group and a High-teen Intraocular Pressure Group in Normal-tension Glaucoma Patients

To compare the features of localized retinal nerve fiber layer (RNFL) defects between a low-teen intraocular pressure (IOP) group and a high-teen IOP group in normal-tension glaucoma (NTG) patients. Seventy-seven eyes of 77 NTG patients showing localized RNFL defects on RNFL photographs and corresponding visual filed defects at the initial visit to a glaucoma specialist were selected for this study. Patients with range of diurnal IOP within low-teen or high-teen in both eyes were included. All participants completed refraction, diurnal IOP measurement, central corneal thickness (CCT) measurement, stereoscopic disc photography, RNFL photography, and automated perimetry. On RNFL photograph, approximation of the defect to the macula (angle alpha) and width of the defects (angle beta) were measured to represent RNFL defects. The patients were divided into 2 groups according to the level of IOP. A low-teen group had highest IOP of <or=15 mm Hg (group A) and a high-teen group had lowest IOP of >15 mm Hg (group B). Age at diagnosis, percentage of male patients, systemic disease, refraction, CCT, highest IOP, angle alpha, angle beta, and mean deviation and pattern standard deviation of visual field were compared between the 2 groups. Age at diagnosis of NTG, age distribution, percentage of male patients, systemic disease, spherical equivalent of refraction, CCT, mean deviation, and pattern standard deviation were not different between the 2 groups. Highest IOP was 13.8+/-1.2 mm Hg in group A and 19.2+/-1.4 mm Hg in group B (P<0.001). Angle alpha was significantly smaller in group A than in group B (37.0+/-14.0 vs. 56.5+/-21.2 degrees, P<0.001), whereas angle beta was not different between the 2 groups (39.9+/-17.9 vs. 37.5+/-15.9 degrees, P=0.54). There were no significant correlations between spherical equivalent and angle alpha (r=-0.03, P=0.82), between spherical equivalent and angle beta (r=-0.04, P=0.74), and between angle alpha and angle beta (r=-0.21, P=0.07). Localized RNFL defect was closer to the center of the macula in group A than in group B, whereas width of defects was not different between the 2 groups. These findings provide indirect evidence to suggest that more than one pathogenic mechanism may exist in the development of RNFL defects in NTG.

Effect of Light Cycle on 24-hour Pattern of Mouse Intraocular Pressure

The present study was undertaken to determine the magnitude, dynamic pattern, and synchrony of the 24-hour pattern of intraocular pressure (IOP), and to clarify the effect of light cycle on 24-hour pattern of IOP in ddY albino mice. Three groups of ddY albino mice were exposed to a 12-hour light/dark cycle (control group), to constant light and, to constant dark, respectively. Every group was exposed to each condition for 4 weeks before IOP measurements. IOP was measured every 3 hours using a microneedle method. Mice were measured repeatedly at 1-week interval. The 24-hour IOP pattern of the control group showed a rhythmic pattern that appeared to be sinusoidal. This IOP declined in the morning until 9:00, and then increased in the early evening until 21:00. In contrast, IOP of the constant light and dark groups were asynchronous exhibiting multiple peaks and troughs during the 24-hour period. The mean IOP of the constant light group was almost equal to that of control group. The mean IOP measured at the daytime of the constant dark group (light time of control group), was significantly higher than that of the control group, and was almost equal to the mean IOP measurements at the dark time of the control group. These results show that 24-hour IOP pattern in mouse eyes is biphasic and that extended exposure to constant light or dark disrupts this 24-hour IOP pattern.

Pattern of intraoccular pressure in Lagos

Objective: To study the pattern of normal intraocular pressure (IOP) in Lagos, Nigeria.Study Design: Prospective non-randomized uncontrolled hospital-based study.Methodology: Consecutive new patients coming into three different eye clinics between June and August 2001 had their IOP measured by applanation. The demographic characteristics and laterality of the IOP measured were documented. Excluded were: patients with glaucoma, ocular trauma, ocular surgery, ocular inflammation, retinal/choroidal detachment, family history of glaucoma, myopia; patients on corticosteroid or antiglaucoma therapy; patients who had had an anaesthetic administered; and patients with systemic diseases such as hypertension, diabetes and thyroid disease. Statistical testing of significance was done using the student t-test, and level of significance was taken to be p0.1). Mean IOP was 14.81mmHg for the right eye and 15.41mmHg for the left, and was not statistically significant (p>0.055). IOP increased with age from 13.85mmHg in the second decade to 16.21mmHg in the ninth decade.Conclusion: The IOP range and mean IOP values are similar to those from other studies. IOP generally increased with age, tending to drop slightly after the seventh decade in males but rising steadily in females. The sex of the patient and laterality of IOP did not have a significant effect on IOP.Keywords: intraocular pressure, glaucoma, intraocular pressure distributionNigerian Journal of Ophthalmology Vol. 13 (1) 2005: 1-3

Diurnal variation of intraocular pressure and its correlation with retinal nerve fiber analysis in Turkish patients with exfoliation syndrome

The purpose was to evaluate the diurnal variation (DV) of intraocular pressure (IOP) in patients with exfoliation syndrome (XS), to measure retinal nerve fiber layer (RNFL) thickness by using scanning laser polarimetry, and to compare these measurements with those of normal subjects. Forty-five subjects with XS and 40 healthy, age/sex matched subjects were recruited into the study. A detailed ophthalmologic examination was performed. IOP measurements were obtained at 08:00 am, 12:00 pm, 03:00 pm, and 06:00 pm. The XS group was further divided into DV > or = 5 mmHg and DV < 5 mmHg groups and also according to the existence of IOP fluctuation. The IOP measurements and RNFL thickness measurements were compared between the groups. The mean IOP value was found to be highest in the morning both in the XS and control groups. IOP showed a gradual decrease from 8.00 am to 6.00 pm in the control group, whereas a second peak at 03:00 pm was observed in the XS group. There was a fluctuation in 53.3% of the XS group, while none of the healthy subjects showed fluctuation. Superior and inferior ratios were statistically lower in XS patients than those in control subjects (p<0.05). Moreover, in patients with XS showing a DV > or = 5 mmHg and/or a fluctuation, the superior ratio, inferior ratio, the number, superior average and superior integral were significantly different (all p values <0.05) from those of control subjects. As the XS patients with high diurnal IOP variation and fluctuating pattern of IOP had lower RNFL thickness measurements, it is crucial to follow up these patients by performing scanning laser polarimetry in order to discover any possible glaucomatous damage at an earlier stage than with the use of conventional visual field analysis.

Pattern of intraocular pressure in epidemic dropsy in India.

This study was conducted to report on the intraocular pressure (IOP) pattern in patients with epidemic dropsy. Two hundred and thirty proven cases of epidemic dropsy were sent for ocular examination. We measured IOP by applanation tonometry at different intervals. Patients were followed up until 24 weeks. Intraocular pressure of more than 22 mm of Hg was detected in 10.86% patients at the start of the study. However, at 12 weeks only 0.43% patients needed medication for control of IOP. None required medication for IOP control after 20 weeks. The rise of IOP in this case series of epidemic dropsy appeared to be a transient phenomenon and drugs needed to be titrated on a weekly basis.