The Ocular Hypertension Treatment Study: baseline factors that predict the onset of primary open-angle glaucoma

A long-term prospective study of risk factors for glaucomatous visual field loss in patients with ocular hypertension

PURPOSE

To evaluate the importance of baseline risk factors for development of glaucomatous visual field loss in patients with high-risk ocular hypertension.

METHODS

In the Malmö Ocular Hypertension Study, 90 patients were randomized to topical timolol or placebo treatment and observed prospectively for up to 10 years. Patients with elevated intraocular pressure (IOP) and with open angles and normal visual fields, plus at least one extra risk factor, were eligible. Risk factors were suspect disc or known disc hemorrhage, positive family history of glaucoma, pseudoexfoliation or pigment dispersion syndrome, diabetes, and mean IOP on DTC > or = 27 mm Hg. These risk factors and also the mean baseline IOP and IOP fluctuation, sex, age, and blood pressure were evaluated as predictors for development of reproducible glaucomatous visual field loss. In addition to the prospective data, post-study data were retrieved from patients' records extending maximum follow-up to 17 years.

RESULTS

Thirty-seven patients developed glaucomatous visual field loss. Of all factors included in the analysis, disc appearance, older age, and higher IOP came out as significant risks. Suspect disc appearance increased the risk approximately three times, with a hazard ratio of 2.90, and CI: 1.34-6.30, the hazard ratio was 1.05 and CI: 1.03-1.09 per year of age, while mean baseline IOP increased the risk with 14% per mm Hg (CI: 1.01-1.28).

CONCLUSION

Patients with ocular hypertension were at higher risk for developing glaucomatous visual field loss if discs were suspect, if IOP was high, and if the patient was older in age.

The validity of a digital eyelid tonometer (TGDc-01) and its comparison with Goldmann applanation tonometry - a pilot study

PURPOSE

To determine the intra- and inter-examiner repeatability of a new eyelid tonometer, and its agreement with Goldmann applanation tonometry (GAT).

MATERIALS AND METHODS

Forty normal subjects were recruited and their intraocular pressure was measured by two examiners using the eyelid tonometer. Examiner 1 carried out the first set of measurement, followed by examiner 2, and then examiner 1 again. Finally, a third examiner was responsible for GAT measurement. Five readings were obtained from the eyelid tonometer by each examiner each time and were masked, and three readings were obtained from GAT. The mean readings from the eyelid tonometer and GAT were used for analysis.

RESULTS

The intra-examiner repeatability for the eyelid tonometer was better (around +/-5 mmHg 95% of the cases) than the inter-examiner repeatability (around +/-8 mmHg 95% of the cases). The mean difference between the eyelid tonometer and GAT was small from examiner 1 (<0.5 mmHg). However, the limits of agreement were greater than the clinically acceptable level of +/-3 mmHg. Examiner 2 gave an even greater difference from GAT.

CONCLUSIONS

Similar to other recent studies, we have found that this eyelid tonometer does not provide good agreement with GAT. Different examiners could position the instrument differently and this eyelid tonometer is suggested for screening purposes only.

Gold standard medical therapy for glaucoma: defining the criteria identifying measures for an evidence-based analysis

BACKGROUND

Over the past decade, several new medical therapies have become available for the treatment of primary open-angle glaucoma (POAG). A systematic evidence-based approach for identifying an optimal therapeutic agent is lacking.

OBJECTIVES

The aims of this review were to critically evaluate published treatment recommendations for POAG and, based on a systematic review of the literature, to develop criteria that would define a "gold standard" medical therapy that reflects new treatment advances and established therapeutic goals.

METHODS

A MEDLINE search spanning the years 1966 to 2002 and using the search terms gold standard, drug of choice, agent of choice, benchmark, ophthalmology, eye, and glaucoma was conducted and the results reviewed by a panel of 15 experts in the field of glaucoma. Published treatment recommendations for POAG were discussed. Criteria, anchored to medical evidence, for distinguishing a standard of medical therapy for POAG were defined.

RESULTS

The terms connoting a gold standard therapy were found in only 258 of approximately 368,000 ophthalmology-related citations and 53 of almost 23,000 glaucoma citations, validating the need to define therapeutic standards. The lack of recommendations for the use of new classes of ocular hypotensive agents was acknowledged. Criteria identified to evaluate intraocular pressure (IOP)-lowering agents as gold standards included the following: efficacy in reducing IOP consistently over a 24-hour period to a level that will preserve the visual field and protect the optic nerve without inducing tachyphylaxis and tolerance, paucity of local and systemic adverse effects, promotion of patient compliance, and applicability in diverse patient populations.

CONCLUSIONS

These criteria should be employed as measures for evidence-based analyses to evaluate available and future IOP-lowering medical therapies for POAG. The conceptual framework presented may be applicable to other therapeutic areas.

Current and emerging medical therapies for glaucoma

Glaucoma is a multifactorial optic neuropathy in which there is a characteristic acquired loss of retinal ganglion cells, at levels beyond normal age-related baseline loss, and corresponding atrophy of the optic nerve. Although asymptomatic in its earlier stages, the disease is nevertheless one of the leading global causes of irreversible blindness. Although elevated intraocular pressure (IOP) is one of the most important risk factors and lowering of IOP is the only proven treatment so far, the definition of glaucoma has evolved from a disease caused by increased IOP to one characterised by an IOP-sensitive, progressive optic neuropathy. In recent years, safer and better tolerated topical medications have been developed to control IOP more effectively, thereby limiting the need for surgery. New research has also noted the importance of diurnal IOP variation as a critical risk factor for progression of glaucomatous optic neuropathy (GON) and subsequent visual field loss. Moreover, new discoveries have further elucidated the basic pathophysiological and genetic mechanisms underlying the elevated levels of IOP, as well as the cellular mechanisms of GON. As our understanding of these complex pathways continues to improve, development opportunities for new therapeutic modalities will be enhanced.

Optic nerve damage in highly myopic eyes with chronic open-angle glaucoma

PURPOSE

To compare the amount of optic nerve damage in relation to intraocular pressure in highly myopic eyes with chronic open-angle glaucoma versus non-highly myopic eyes with chronic open-angle glaucoma.

METHODS

The comparative clinical observational study included 1841 eyes of 1100 patients with chronic open-angle glaucoma. The highly myopic study group consisted of 25 eyes with a myopic refractive error equal to or higher than -8 diopters. It was subdivided into eyes with an optic disc size larger than 2.7 mm2 and eyes with an optic disc smaller than 2.7 mm2. The control group included the remaining, non-highly myopic eyes (n=1816). For all patients, a morphometric analysis of color stereo optic disc photographs was performed. Main outcome measures were morphometric optic disc measurements and intraocular pressure.

RESULTS

In the highly myopic, large-optic-disc study group compared with the control group, maximal and minimal intraocular pressure readings were significantly (p<0.05) lower and neuroretinal rim area corrected for optic disc size was slightly (p=0.16) smaller. Comparing the total highly myopic study group with a control group adjusted for optic disc area, neuroretinal rim area was significantly (p=0.039) smaller in the study group with no significant difference in intraocular pressure measurements between the groups.

CONCLUSIONS

At a given intraocular pressure in chronic open-angle glaucoma, optic nerve damage may be more pronounced in highly myopic eyes with large optic discs than in non-highly myopic eyes. This may suggest a higher susceptibility for glaucomatous optic nerve fiber loss in highly myopic eyes than in non-highly myopic eyes.

The relationship between central corneal thickness-adjusted intraocular pressure and glaucomatous visual-field loss

BACKGROUND

Although measurement of central corneal thickness (CCT) is increasingly becoming an important component of glaucoma risk analysis, significant controversy exists regarding the benefit of calculating a corrected intraocular pressure (IOP) value from measured IOP and CCT data.

METHODS

Three hundred forty-four male subjects were identified from a VA eye clinic with one of the following clinical diagnoses: ocular hypertension (OHT), primary open-angle glaucoma (POAG), normal tension glaucoma (NTG), and normal tension glaucoma suspect (NTGS). Using one eye per subject, multivariate logistic regression and correlational analyses were performed to determine relationships between glaucomatous visual-field loss and several glaucoma risk factors, including adjusted IOP values.

RESULTS

Multivariate logistic regression analysis did not identify CCT-adjusted IOP values as independent risk factors for development of either NTG or POAG-related glaucomatous visual-field loss. CCT, however, was found to be strongly associated with both NTG and POAG-related visual-field loss. Correlational analysis revealed a weak correlation between Ehlers-adjusted pre-treatment IOP and severity of POAG-related visual-field loss, but no other adjusted IOP values significantly correlated with severity of visual-field loss in either POAG or NTG.

CONCLUSIONS

Our results suggest that adjusted IOP, as calculated using current algorithms, is not useful within glaucoma risk analysis, since adjusted IOP was unable to predict either presence or severity of glaucomatous visual-field loss in this study. CCT, conversely, was found to be a robust and independent predictor of glaucomatous visual-field loss. These findings, while supporting routine CCT measurements for all glaucoma suspects, do not support routine clinical computation of adjusted IOP values using current algorithms.

Relationship between corneal thickness and optic disc damage in glaucoma

BACKGROUND

Central corneal thickness (CCT) has been found to be a powerful predictor for the development of glaucoma in patients with ocular hypertension. This study aimed to determine whether CCT was also related to glaucoma severity.

METHODS

The vertical cup/disc ratio (VCDR) was used as a single objective measure of glaucoma severity. Vertical cup diameters and vertical disc diameters were measured using a graticule attached to a 60 D Volk lens, in consecutive patients presenting to a single ophthalmologist. Measurements were corrected for magnification. The difference between corrected VCDR and 95% probability of VCDR normality was compared to CCT, which was measured with an ultrasonic pachymeter.

RESULTS

During the study period 554 eyes from 281 patients with glaucoma were reviewed. The mean CCT was 519.0 microm, with the mean corrected VCDR being 0.71. A univariate linear regression model revealed that an increase of 10 microm in CCT resulted in a 0.009 decrease in the difference between true VCDR and the predicted normal VCDR. The R2 value for the regression was 0.04 (P < 0.0001).

CONCLUSION

There is a highly statistically significant, albeit small, negative correlation between corneal thickness and glaucoma severity. This study supports the notion that CCT should be measured in the assessment of patients with glaucoma. Progressive thinning or presence of a thin cornea may have pathogenic or prognostic roles in some types of glaucoma.

Comparison of intraocular pressure measured by Pascal dynamic contour tonometry and Goldmann applanation tonometry

AIMS

To compare the intraocular pressure (IOP) measurements obtained using the Pascal dynamic contour tonometer (PDCT) with the standard Goldmann applanation tonometer (GAT) and to correlate these with central corneal thickness (CCT) in patients with normal corneas.

METHODS

A prospective, masked, comparative case series of 116 eyes from patients attending a glaucoma clinic. IOP was measured with PDCT by one examiner and with GAT by a masked, independent examiner. A mean of six CCT readings was used for analysis.

RESULTS

IOP measured by the two instruments correlated significantly (r=0.77; P<0.0001). IOP measured by GAT correlated strongly with CCT (r=0.37, P=0.0001) whereas the relationship between IOP measured by PDCT and CCT approached significance (r=0.17, P=0.073). The differences between GAT and PDCT measured IOP also correlated strongly with CCT (r=0.37, P<0.0001). The 95% limits of agreement between GAT and PDCT were +/-4.2 mmHg. Dividing the eyes into three groups on the basis of CCT, demonstrated those in the thickest tertile showed a poorer agreement between instruments and the GAT measured significantly higher IOP in this group (P=0.003) while the PDCT showed no significant differences with different CCTs (P=0.37).

CONCLUSION

Demonstration of the relative independence of PDCT IOP measurements from CCT supports a potential clinical role for this instrument, particularly for subjects with CCT outside the normal range.

Association between corneal thickness, mean intraocular pressure, disease stability and severity, and cost of treatment in glaucoma: a Canadian analysis

PURPOSE

We determined the association between the mean corneal thickness (CT) and visual field mean defect (VF) severity as well as with mean intraocular pressure (IOP), disease stability, and cost of glaucoma therapy in a Canadian setting.

METHODS

Data were collected from charts of patients diagnosed with primary open-angle glaucoma (POAG). CT measures, VF scores, IOP measurements, physicians' impressions, and resources used (physician visits, diagnostic tests, procedures, and medications) were recorded over a minimum of 2.5 years. CT was compared across the three VF severity levels [mild (0 to < 5 dB), moderate (5 to < 12 dB), and severe (>/= 12 dB)] using a Kruskall-Wallis test. Initial VF was regressed on Age, CT, IOP, and Optic Disc Ratio. Stability and Cost were regressed on IOP.

RESULTS

Of the 411 charts, 132 included CT measures. Patients included 50 with mild, 43 with moderate, and 39 with severe disease. The mean CTs of the overall, mild, moderate, and severe groups were 545.9 mum, 554.7 mum, 549.8 mum, and 523.3 mum, respectively. There were statistically significant differences (p < 0.05) between the CT pp of the mild and severe groups as well as between the moderate and severe groups. Regression analyses suggested that CT may be a predictor of disease severity, but not of cost. It was also found that IOP may be a predictor of disease progression.

CONCLUSIONS

Patients with severe VFs tend to be those who have thinner corneas. Further research is warranted, as a result of the limited sample size, to clarify the definitive association among corneal thickness, disease progression, and the cost of therapy.

Assessment of central corneal thickness using optical coherence tomography

PURPOSE

To demonstrate the capability of model OCT3 optical coherence tomographer to evaluate central corneal thickness (CCT) in normal human corneas in vivo and compare the results with the those of standard ultrasound (US) pachymetry and Orbscan.

SETTING

New York Eye & Ear Infirmary Resident Clinic, New York, New York, USA.

METHODS

The CCT in 22 eyes of 11 subjects was determined with the OCT3 (Carl Zeiss Meditec), Orbscan (Bausch & Lomb, Inc.), and US pachymetry (DGH Technology, Inc.). Three central corneal scans of each eye were obtained using the OCT3. First, OCT3 data were processed using the standard OCT software program (OCT3(std)). Second, OCT3 raw data were exported and measurements were repeated using Scion Image for Windows program (OCT3(sci)). The OCT3 and Orbscan results were compared with the mean of 5 US pachymetry measurements in each eye.

RESULTS

The OCT3(std), OCT3(sci), and Orbscan CCT measurements showed high correlations with US pachymetry (r=0.981, r=0.984, and r=0.942, respectively; P<.0001). Bland-Altman analysis showed a high level of agreement between US pachymetry and OCT3 techniques but not Orbscan. High repeatability for OCT3(std) (r(2)=0.05) and OCT3(sci) (r(2)=0.01) was also seen.

CONCLUSION

Results show the OCT3 is an accurate, noninvasive, and reproducible technique for evaluation of CCT.

Ocular structure and function in an aged monkey with spontaneous diabetes mellitus

Diabetes mellitus develops spontaneously in middle-aged, obese rhesus monkeys, thus making them a good model for examining the effects of co-morbid factors on the development of end-organ damage. Changes in structure and function in the eyes of one monkey who spontaneously developed type 2 diabetes are reported here. This animal had concomitant hypertension, high levels of triglycerides and serum cholesterol, and a low fraction of high-density lipoprotein. The eyes showed intraretinal hemorrhages and large areas of retinal capillary nonperfusion. Indo-cyanin green (ICG) angiography revealed a large area of non- or poorly perfused choriocapillaris in one eye, and immunohistochemistry showed loss of viable choriocapillaries in this region. Both basal laminar deposits and hard drusen were present on areas of Bruch's membrane adjacent to nonviable choriocapillaris. Blood flow via the nasal posterior ciliary arteries to this section of choroid was not detectable by color duplex Doppler ultrasound, indicating contribution of extraocular vascular disease to ischemia in this eye. There was a severe decline in number of photoreceptor inner and outer segments, and corresponding reductions in the multifocal electroretinogram (ERG), in the areas of choriocapillaris loss. The ganzfeld ERG indicated loss in both inner and outer retinal function. Much of the ganglion cell layer was absent throughout the retina, possibly reflecting the effect of diabetes as well as chronic open angle glaucoma; the latter diagnosis supported by elevated intraocular pressures and excavated optic disks. In summary, high resolution, enzyme histochemical and histopathological analyses of a diabetic hypertensive monkey retina and choroid after serial functional in vivo analyses have demonstrated the relationship between vascular dysfunction and visual function loss. Choroidal vascular dysfunction in both large and small vessels was associated with age-related macular degeneration-like changes in Bruch's membrane and photoreceptor degeneration.

Results of the European Glaucoma Prevention Study

OBJECTIVE

The European Glaucoma Prevention Study (EGPS) seeks to evaluate the efficacy of reduction of intraocular pressure (IOP) by dorzolamide in preventing or delaying primary open-angle glaucoma (POAG) in patients affected by ocular hypertension (OHT).

DESIGN

Randomized, double-masked, controlled clinical trial.

PARTICIPANTS

One thousand eighty-one patients (age, > or =30 years) were enrolled by 18 European centers. The patients fulfilled a series of inclusion criteria, including: IOP 22 to 29 mmHg; 2 normal and reliable visual fields (on the basis of mean deviation and corrected pattern standard deviation or corrected loss variance of standard 30/II Humphrey or Octopus perimetry); normal optic disc as determined by the Optic Disc Reading Center.

INTERVENTION

Patients were randomized to treatment with dorzolamide or placebo (the vehicle of dorzolamide).

MAIN OUTCOME MEASURES

Efficacy end points were visual field, optic disc changes, or both. A visual field change during follow-up had to be confirmed by 2 further positive tests. Optic disc change was defined on the basis of the agreement of 2 of 3 independent observers evaluating optic disc stereo slides. The safety end point was an IOP of more than 35 mmHg on 2 consecutive examinations.

RESULTS

During the course of the study, the mean percent reduction in IOP in the dorzolamide group was 15% after 6 months and 22% after 5 years. Mean IOP declined by 9% after 6 months and by 19% after 5 years in the placebo group. At 60 months, the cumulative probability of converting to an efficacy end point was 13.4% in the dorzolamide group and 14.1% in the placebo group (hazard ratio, 0.86; 95% confidence interval [CI], 0.58-1.26; P = 0.45). The cumulative probability of developing an efficacy or a safety end point was 13.7% in the dorzolamide group and 16.4% in the placebo group (hazard ratio, 0.73; 95% CI, 0.51-1.06; P = 0.1).

CONCLUSIONS

Dorzolamide reduced IOP by 15% to 22% throughout the 5 years of the trial. However, the EGPS failed to detect a statistically significant difference between medical therapy and placebo in reducing the incidence of POAG among a large population of OHT patients at moderate risk for developing POAG, because placebo also significantly and consistently lowered IOP.

Dynamic contour tonometry versus Goldmann applanation tonometry: a comparative study

BACKGROUND

Various sources of error, including central corneal thickness (CCT) and structural corneal rigidity, have been proposed for Goldmann applanation tonometry (GAT). The Pascal dynamic contour tonometer (DCT) is a novel device designed for intraocular pressure (IOP) measurements assumed to be largely independent of CCT and corneal curvature. We compared DCT with GAT in eyes with normal corneas of various thickness.

METHODS

We prospectively measured IOP using DCT and GAT in random order in 100 eyes of 100 subjects (M:F=46:54; mean age 42+/-19, range 23-88 years).

RESULTS

Mean DCT values were about 1 mm Hg higher than GAT readings (16+/-3 vs 15+/-3 mmHg, p=0.001). Bland-Altman analysis of individual pairs of DCT and GAT measurements revealed a bias of -1.0 mmHg [95% confidence interval (CI): +/-1.2]. Neither GAT nor DCT showed a significant correlation with CCT (533+/-48, range 399-641 microm).

CONCLUSIONS

In eyes with normal corneas, DCT allows suitable and reliable IOP measurements which are in good concordance with GAT. Comparison of DCT with intracameral manometry is desirable in the future.

The Low-pressure Glaucoma Treatment Study (LoGTS)

OBJECTIVE

The Low-Pressure Glaucoma Treatment Study (LoGTS) seeks to evaluate visual field stability in low-pressure glaucoma patients randomized to intraocular pressure reduction in both eyes with topical twice daily brimonidine tartrate 0.2% versus twice daily timolol maleate 0.5%. This article describes the LoGTS design and presents baseline characteristics of the subjects.

DESIGN

Randomized, multicenter, double-masked clinical trial.

PARTICIPANTS

Low-pressure glaucoma patients 30 years of age or older were identified. Exclusion criteria included an untreated pressure of more than 21 mmHg, advanced visual field loss, and contraindications to study medications.

INTERVENTIONS

Randomization of both eyes to double-masked monotherapy with brimonidine or timolol. Follow-up visits included Humphrey 24-2 full-threshold perimetry, tonometry every 4 months, and annual optic disc photography.

MAIN OUTCOME MEASURE

Progression of visual field loss.

RESULTS

One hundred ninety patients were randomized between 1998 and 2000. Mean age (+/-standard deviation) was 64.9+/-10.7 years. Women comprised 59.5% of the patients. Fifty-three patients (27.9%) had unilateral field loss. The 137 patients with bilateral field loss were older than those with unilateral field loss: 65.7 versus 62.3 years of age (P<0.05). Mean untreated diurnal intraocular pressures were similar between the eyes of the bilateral patients (mean, 15.5 mmHg in both eyes) and unilateral patients (mean, 16.0 mmHg in field loss vs. 15.6 mmHg in fellow eyes). Visual field mean deviation for all eyes was -5.4+/-4.7 decibels. Central corneal thickness in 168 phakic patients was 543 +/- 35 microm (range, 435-655 microm); thickness was less than 500 microm in 15 eyes and was more than 600 microm in 11 eyes. Mean vertical cup-to-disc ratio for all eyes was 0.67+/-0.15. Unilateral field loss patients had a larger cup-to-disc ratio in the field loss eye (0.75+/-0.12) than the fellow eye with a normal field (0.60+/-0.17, P<0.0001). Disc hemorrhage was present at baseline in 29 patients (32 eyes).

CONCLUSIONS

The LoGTS was successfully able to recruit and enroll patients with open-angle glaucoma and statistically normal intraocular pressure into a longitudinal, prospective clinical trial comparing 2 different glaucoma medications. Baseline characteristics of note were a preponderance of females, unilateral field loss in 27.9% of participants, and frequent optic disc hemorrhage. Central corneal thickness had a normal distribution and did not account for false low-pressure measurements in LoGTS patients.

Corneal thickness and axial length

PURPOSE

A thin central cornea has been reported to be a risk factor for developing primary open-angle glaucoma among ocular hypertensive eyes. A thin scleral bed of lamina cribrosa seen in deeply excavated optic nerves in glaucomatous eyes is a quintessential finding in advanced glaucomatous eyes. Association between thin cornea and weak sclera contributing to vulnerability of lamina cribrosa has been postulated. The purpose of this study is to determine whether there is an association between corneal thickness and axial length of human eyes in a clinical setting.

DESIGN

This is an observational, retrospective cross-sectional study.

METHODS

The ocular parameters of 1,084 consecutive eyes with both corneal thickness and axial length measurements were analyzed and compared by age, gender, and race.

RESULTS

In the total patient study group, there was no statistically significant association between central corneal thickness and axial length. Subgroup analysis by age, gender, and race also failed to show an association.

CONCLUSIONS

Central corneal thickness and axial length are independent occurrences. Thin corneas are not associated with longer eyes.

Risk of glaucoma in ocular hypertension with and without pseudoexfoliation

PURPOSE

To compare glaucoma conversion rates in patients with ocular hypertension (OH) with and without pseudoexfoliation.

DESIGN

Cohort study, based on 32,918 screening participants.

PARTICIPANTS AND CONTROLS

Ninety-eight patients with OH and pseudoexfoliation and 98 matched controls.

MAIN OUTCOME MEASURE

Perimetric glaucoma conversion.

METHODS

A population-based glaucoma screening of elderly citizens of Malmö, Sweden, was conducted between 1992 and 1997 to recruit participants for the Early Manifest Glaucoma Trial. Screening participants with intraocular pressure (IOP) between 24 and 32 mmHg and pseudoexfoliation were compared to controls among other screening participants without pseudoexfoliation but matched for baseline IOP, age, and gender, and the 2 groups were invited to a reexamination. Computerized visual field tests were performed to identify persons with manifest glaucoma. Visual acuity, refraction, IOP, and central corneal thickness were also measured.

RESULTS

After a mean of 8.7 years (range: 6.3-11.4), 54 of 98 patients (55.1%) with pseudoexfoliation at the baseline examination and 27 of 98 patients (27.6%) without pseudoexfoliation had developed glaucoma. The risk ratio was 2.0 (P<0.0001).

CONCLUSION

The glaucoma conversion rate was twice as high in patients with OH and pseudoexfoliation as in control patients matched for IOP, age, and gender. Thus, pseudoexfoliation was a strong independent risk factor for glaucoma in patients with OH.

Corneal thickness and functional damage in patients with ocular hypertension

PURPOSE

To correlate functional damage over time detected by standard automated perimetry (SAP) and frequency doubling technology (FDT) with central corneal thickness (CCT) in patients with ocular hypertension (OHT).

METHODS

Seventy-eight OHT patients underwent CCT measurements, SAP, and FDT (the latter two also after 12 and 18 months). Patients were divided into three equally sized groups of 26 patients each: thin (< 540 microm), normal (540-580 microm), and thick cornea (> 580 microm). The frequency of abnormal FDT and SAP results was analyzed over time (Pearson chi2 test).

RESULTS

Six of 26 patients with thin corneas (23.1%) presented an abnormal FDT test at baseline, compared to 1 of 26 (3.8%) in the normal thickness cornea group and 1 of 26 (3.8%) in the thick cornea group. After 12 months, the abnormal FDT tests were as follows, respectively: 9 of 26 (34.6%), 2 of 26 (7.7%), and 2 of 26 (7.7%). For SAP the abnormal results were as follows, respectively: 8 (30.1%), 5 (19.2%), and 2 (7.7%). After 18 months, the abnormal FDT tests were as follows, respectively: 16 (61.5%), 5 (19.2%), and 5 (19.2%). For SAP, the abnormal results were as follows, respectively: 10 (38.5%), 5 (19.2%), and 2 (7.7%).

CONCLUSIONS

OHT patients with thinner corneas have a greater risk of developing functional damage over time.

Normative ranges and specificity of the multifocal VEP

PURPOSE

To describe a normative database for the multifocal VEP (mfVEP) and to evaluate specificity for a range of cluster criteria.

METHODS

One hundred persons (62 females and 38 males) with normal visual fields and ranging in age from 21.6 to 92.4 years participated in this study. Self-reported race in 80 of these 100 persons was 'White or Caucasian,' eight were 'Black or African-American,' eight were 'Asian,' and four were 'Hispanic or Latino.' Pattern-reversal mfVEPs were obtained using a dartboard stimulus pattern in VERIS and two 8-min runs per eye were averaged. A bootstrap technique was used to estimate the normal range of mfVEP response signal-to-noise ratio (SNR) and inter-ocular amplitude ratio at each location. Specificity (1 - false alarm rate) was evaluated for a range of cluster criteria, whereby the number and probability level of the points defining a cluster were varied.

RESULTS

There was no overall effect of age on SNR (r2 = 0.16, p = 0.22) nor was the interaction between age and location significant (F = 0.83, p = 0.82, ANOVA). The location with the largest age effect had an r2 of only 0.13. There was a small but significant effect of sex (t = 2.1, p = 0.04) such that SNR was slightly (11%) larger in females than males, but there was no significant interaction between sex and age (t = 0.82, p = 0.41). There was a slight trend toward higher SNR in the Asian group and lower SNR in the African-American group, but the overall effect of race was not significant (F = 1.99, p = 0.12). Specificity depended on the number and probability level of the points defining a cluster. Specificity did not vary by age group in a simple monotonic manner. False positive rates were slightly higher in females than males, and slightly higher in the African-American group as compared with the Asian group.

CONCLUSIONS

Excellent specificity can be achieved for the mfVEP by using particular cluster criteria for monocular and inter-ocular tests. The effects of age, sex, and race were all very small and only the effect of sex was statistically significant. This normative database can be used for analyses of mfVEP results from individual patients with little risk that demographic factors such as age and sex will confound diagnostic accuracy.

Central corneal thickness: Will one measurement suffice?

OBJECTIVE

To evaluate the measurement of central corneal thickness (CCT) in a cohort of glaucoma patients over a 3-month period. Measurements were then applied to the criteria described in the Ocular Hypertension Treatment Study (OHTS).

DESIGN

Cohort study.

PARTICIPANTS AND METHODS

Fifty-one patients were recruited from a glaucoma clinic at Moorfields Eye Hospital. Central corneal thickness was measured using an ultrasonic handheld pachymeter by a trained observer. Patients' CCTs were measured at 2 consecutive clinic visits.

MAIN OUTCOME MEASURE

Mean central corneal thickness.

RESULTS

The readings showed clear fluctuation over the 3-month period, with a mean difference in corneal thickness of 9.6+/-26.9 microm in the right eye and 19.0+/-29.2 microm in the left eye. In addition, there was a systematic bias towards increased corneal thickness being recorded at the second reading in both eyes. This reached statistical significance in both the right eye (P = 0.02) and the left eye (P = 0.0003). The criteria used to categorize the risk of patients developing glaucoma in the OHTS were then applied to these results. On the basis of the second reading, 32% of eyes required recategorization in both the right and left eyes.

CONCLUSIONS

Measurements of CCT taken within a clinical setting by a trained observer may show significant variability. For CCT to become a valuable addition to the assessment of glaucoma suspects, more than one reading may be required. Failure to do so may result in misclassification and, thus, an inaccurate assignment of risk.

Reproducibility of Self-Measured Intraocular Pressure With the Phosphene Tonometer in Patients With Ocular Hypertension and Early to Advanced Glaucoma

PURPOSE

To evaluate the reproducibility of self-measured intraocular pressure with the Proview tonometer in ocular hypertensives and early to advanced glaucoma patients.

PATIENTS AND METHODS

Thirty-three patients with glaucoma and three with ocular hypertension (72 eyes) were prospectively enrolled. History of cornea surgery was the only exclusion criterion. A trainer took a set of three readings first. Subsequently, the patient (after successful training) took one set of three readings and a physician took two sets of three Goldmann readings. One hour later this was repeated.

RESULTS

72% of patients could see the phosphene in both eyes, 8% could see it in one eye, and 19% could not see it in either eye. Patients who could not see the Phosphene had an average mean deviation of -10.9 compared with -3.4 for those who could see it (P = 0.01). Eyes that could not see the phosphene were excluded from further analysis. The average absolute difference between two Proview measurements one hour apart was 1.76 +/- 1.76 mm Hg (r = 0.71). The measurement error (difference between Goldmann and Proview readings) tended to remain constant between sets of measurements taken one hour apart (average error was 2.4 +/- 2.1 mm Hg, r = 0.85). No adverse event was recorded.

CONCLUSIONS

Repeated self-tonometry measurements showed very good reproducibility. The systematic, reproducible error between Proview and Goldmann readings may be clinically acceptable and suggests that a baseline "calibration" should be obtained for each patient before the Proview values are used clinically. Self-administered tonometry can play a role in the clinical care of ocular hypertensive and glaucoma patients with the possible exception of very advanced cases.

Relationship between central corneal thickness and retinal nerve fiber layer thickness in ocular hypertensive patients

PURPOSE

To examine the relationship between retinal nerve fiber layer (RNFL) measurements obtained using scanning laser polarimetry with variable corneal compensation and corneal thickness measurements in ocular hypertension (OHT) patients.

DESIGN

Observational cross-sectional study.

SUBJECTS

The study included 1 eye each from 44 OHT patients and 48 healthy subjects, all of similar age. All subjects had normal optic discs and normal standard automated perimetry (SAP) visual fields. Ocular hypertension patients had intraocular pressure (IOP) measurements higher than 22 mmHg.

METHODS

All patients underwent imaging with the GDx VCC (Laser Diagnostic Technologies, Inc., San Diego, CA) scanning laser polarimeter. We examined the relationship between GDx VCC RNFL measurements and central corneal thickness, a risk factor for development of visual field loss among OHT patients. We also examined the relationship of GDx VCC measurements and age, IOP, SAP pattern standard deviation, and vertical cup-to-disc ratio.

MAIN OUTCOME MEASURES

Central corneal thickness (CCT) and GDx VCC RNFL thickness parameters.

RESULTS

Central corneal thickness measurements in OHT patients were significantly higher than those in healthy subjects (575+/-30 microm vs. 555+/-32 microm; P = 0.002). Higher GDx VCC parameter nerve fiber indicator (NFI) scores, indicating thinner RNFL, were correlated significantly with thinner CCT measurements in OHT patients (r = -0.502; P = 0.001). Ocular hypertension patients with thinner corneas (n = 22; mean CCT, 553+/-21 microm) had significantly higher NFI scores than OHT patients with thicker corneas (n = 22; mean CCT, 598+/-18 microm) and healthy control subjects (NFI mean +/- standard deviation, 26.9+/-9.5, 20.7+/-9.8, and 19.7+/-7.0, respectively; P = 0.004, analysis of variance). The NFI values were not significantly different between OHT patients with thicker corneas and healthy subjects. In multivariate analysis, only age and CCT measurement were associated significantly with GDx VCC RNFL measurements in OHT eyes.

CONCLUSIONS

Ocular hypertension patients with thinner corneas had significantly thinner RNFL than OHT patients with thicker corneas and healthy control subjects. These findings support the notion that RNFL defects as assessed by the GDx VCC may represent early glaucomatous damage in OHT eyes.

Correlation between office and peak nocturnal intraocular pressures in healthy subjects and glaucoma patients

PURPOSE

To evaluate the correlations between office-hour intraocular pressures (IOP) and peak nocturnal IOP in healthy and glaucomatous eyes.

DESIGN

Retrospective review of laboratory records.

METHODS

We reviewed 24-hour data of IOP collected from 33 younger healthy subjects (aged 18 to 25 years), 35 older healthy subjects (aged 40 to 74 years), and 35 untreated older glaucoma patients (aged 40 to 79 years) housed in a sleep laboratory. Measurements of IOP were taken every 2 hours using a pneumatonometer in the sitting and supine positions during the diurnal/wake period (7 AM to 11 PM) and in the supine position during the nocturnal/sleep period. Correlations between average sitting or supine IOP in the right eye between 9:30 AM and 3:30 PM (office hours) and peak right eye IOP during the nocturnal hours were analyzed.

RESULTS

The average values of supine IOP during office hours were found to have the strongest correlation with peak nocturnal IOP in older glaucoma subjects (r = .713, P < .001), whereas the correlation was less in older healthy subjects (r = .523, P < .01) and was absent in younger healthy subjects (r = .224, P = .21). The correlation between average sitting IOP values during office hours and peak nocturnal IOP was also strong in older glaucoma subjects (r = .601, P < .001) and moderate in older healthy subjects (r = .412, P < .05), but absent in younger healthy subjects (r = -.077, P = .672).

CONCLUSION

Using a modification of the diurnal IOP curve, the magnitude of peak nocturnal IOP in untreated glaucoma patients can be estimated during routine office visits. Supine IOP measurements estimate peak nocturnal IOP better than sitting measurements. This estimation may provide the clinician with valuable information regarding the nocturnal IOP peak in glaucoma patients.

Pattern electroretinogram abnormality and glaucoma

PURPOSE

To determine the existence of retinal ganglion cell dysfunction and associated risk factors in glaucoma suspects with increased optic disc cupping and normal visual field.

DESIGN

Cross-sectional, observational study.

PARTICIPANTS

Two hundred glaucoma suspect (GS) patients were identified based on optic disc abnormalities (vertical cup-to-disc ratios [C/D]>0.5; vertical C/D asymmetry >or= 0.2; disc hemorrhages; notching) in association with known glaucoma risk factors (positive family history, African American descent, increased intraocular pressure [IOP]), but normal visual fields. Forty-two patients had early manifest glaucoma (EMG). Sixteen normal black subjects were added to update previous pattern electroretinogram (PERG) normative data and to establish a normal control (NC) group with a racial breakdown comparable with that of the study groups.

METHODS

Pattern electroretinograms were recorded simultaneously from both eyes using skin electrodes and automated analysis; visual fields were monitored with standard white-on-white automated perimetry (SAP) central 24-2 program; vertical C/D was evaluated by an independent reader from stereo disc photographs; and univariate and multivariate statistical analysis between PERG and other outcome measures was evaluated.

MAIN OUTCOME MEASURES

Pattern electroretinogram amplitude (microV), phase (pi rad), and interocular asymmetry in amplitude and phase (%); and SAP mean deviation (MD; decibels), vertical C/D, age (years), IOP (mmHg), and race (black vs. nonblack).

RESULTS

The PERG results were abnormal in at least 1 of the outcome measures in 52% of GS patients and 69% of EMG patients. The PERG amplitude was correlated weakly with both MD (P<0.01) and vertical C/D (P = 0.05). The correlation between PERG amplitude and MD and C/D was stronger (P<0.001) for interocular differences rather than absolute measures. Interocular PERG amplitude asymmetry increased with severity of disease (EMG>GS>NC; P<0.01). The PERG amplitude decline with age was steeper in patients with a more negative MD (P<0.01) and in patients with a more negative MD and a larger vertical C/D (P = 0.06). Black race (but not family history) was associated with lower PERG amplitude (P = 0.005) in GS and EMG patients, but not in normal controls (P = 0.44).

CONCLUSIONS

The correlation between PERG abnormality and known risk factors for glaucoma indicates that PERG has a predictive potential for the development or progression of the disease, or both.

Influence of corneal biomechanical properties on intraocular pressure measurement

PURPOSE

To understand and quantify intraocular pressure (IOP) measurement errors introduced by corneal variables during applanation tonometry using a cornea biomechanical model.

SETTING

Department of Ophthalmology, Biomedical Engineering Center, The Ohio State University, Columbus, Ohio, USA.

METHODS

The model assumed an overall resultant pressure that was based on the summation of the applanation pressure, the true IOP, and the surface tension caused by the tear film to determine the final deformation of the corneal apex during IOP measurement. Corneal resistance was varied according to the cornea's biomechanical properties, thickness, and curvature, and the effect of each variable on the accuracy of IOP tonometry readings was examined quantitatively.

RESULTS

The model demonstrated that tonometry readings do not always reflect true IOP values. They deviate when corneal thickness, curvature, or biomechanical properties vary from normal values. Based on the model, predicted IOP readings have a 2.87 mm Hg range resulting from the variation in the corneal thickness in the normal population and a 1.76 mm Hg range from the variation in the corneal radius of curvature. Considering that Young's modulus of the corneal varies from 0.1 to 0.9 MPa in the normal population, the model predicts tonometry IOP readings will have a range of 17.26 mm Hg because of the variation in this corneal biomechanical parameter alone.

CONCLUSIONS

The simulation based on the model demonstrated quantitatively that variations in each corneal variable cause errors in tonometry IOP readings. The simulation results indicate that differences in corneal biomechanics across individuals may have greater impact on IOP measurement errors than corneal thickness or curvature.

Interleukin-1beta tear concentration in glaucomatous and ocular hypertensive patients treated with preservative-free nonselective beta-blockers

PURPOSE

To evaluate the ocular surface inflammatory response to the presence of preservatives in nonselective beta-blocker eyedrops.

DESIGN

Prospective, crossover, single-masked, randomized clinical study.

METHODS

study population: Twenty primary open-angle glaucoma or ocular hypertensive patients were divided in two groups, one treated with preservative-free timolol 0.5% (group 1) and the other with preserved timolol 0.5% (group 2) eyedrops. After 60 days of therapy and 3 more weeks of washout, the two groups switched to the other therapy. procedure: At each visit, basal tear samples were collected from the inferior conjunctival fornix for the determination of interleukin (IL)-1beta tear concentrations by an enzyme-linked immunosorbent assay. Intraocular pressure measurement, conjunctival hyperemia, superficial punctate keratitis, and tear film breakup time were evaluated. main outcome measure: IL-1beta concentration in tears following the use of preserved eyedrops.

RESULTS

IL-1beta tear concentrations increased significantly in both groups, compared with baseline values, during preserved timolol therapy. There were no statistically significant changes in hyperemia and superficial punctate keratitis throughout the study in either group. A statistically significant breakup time reduction was observed in both groups after 30 days and after 60 days of preserved therapy.

CONCLUSION

The use of preservatives in timolol 0.5% eyedrops leads to tear film instability and ocular surface inflammatory changes documented by a reduction of breakup time and an increase of IL-1beta tear concentrations. Preservative-free beta-blockers are preferable for long-term hypotensive therapy to prevent ocular surface inflammation.

Central corneal thickness and its relationship to intraocular pressure in children

OBJECTIVE

Central corneal thickness (CCT) has emerged as an important predictive factor for the development of glaucomatous damage. Although a child's cornea reaches adult thickness by the age of 3, little has been reported about normal CCT measurements in eyes of children. We wished to test the hypotheses that (1) there is a correlation between increasing CCT and increasing intraocular pressure (IOP) in the eyes of children, (2) the CCT in the eyes of children with ocular hypertension is greater than that in eyes of normal pediatric subjects, and (3) the average CCT of black children is less than that of white children.

METHODS

We performed a retrospective chart review of 69 pediatric patients seen in the office of one ophthalmologist between January 1997 and December 2001 in whom CCT was measured by ultrasound pachymetry. We categorized the subjects into diagnostic groups of controls, glaucoma, glaucoma suspects, and ocular hypertension based on IOP, cup-to-disc ratio, and visual field parameters.

RESULTS

The average CCT for the control patients was 555+/-37 microm; for patients with glaucoma, it was 563+/-33 microm; for glaucoma suspects, 559+/-39 microm; and for those with ocular hypertension, 595+/-39 microm. The difference between the control and ocular hypertensive groups was significant (P<0.02). The difference in CCT between the black control subjects and the white ones (537+/-36 microm vs. 564+/-28 microm) was not statistically significant (P = 0.125).

CONCLUSIONS

Central corneal thickness is greater in children with ocular hypertension than in control subjects or those with glaucoma, and the values for CCT in these children correlate closely with values reported for adults. Corneas of black children may be thinner than the corneas of white children.

Central corneal thickness and measured IOP response to topical ocular hypotensive medication in the Ocular Hypertension Treatment Study

PURPOSE

To determine whether central corneal thickness (CCT) correlates with measured intraocular pressure (IOP) response to topical ocular hypotensive medication in the Ocular Hypertension Treatment Study (OHTS).

DESIGN

Prospective randomized clinical trial.

METHODS

Intraocular pressure measurements were performed by Goldmann applanation tonometry. Central corneal thickness was measured by ultrasonic pachymetry. The following indicators of IOP response to topical ocular hypotensive medication were examined: (1) IOP after an initial four- to six-week one-eyed therapeutic trial of a nonselective beta-blocker (N = 549) or a prostaglandin analog (N = 201); (2) the mean IOP response during 12 to 60 months of follow-up among medication participants (N = 689); (3) the percentage of follow-up visits at which both eyes met the treatment goal; (4). the total number of different medications prescribed to reach treatment goal; and (5) the total number of different medications prescribed multiplied by the number of months each medication was prescribed.

RESULTS

Central corneal thickness was inversely related to the IOP response after the initial one-eyed therapeutic trial and during 12 to 60 months of follow-up (P < .05). Mean CCT was not correlated with the number of different medications prescribed during follow-up, the total medication-months, or the percentage of visits at which IOP target was met.

CONCLUSIONS

Individuals with thicker corneas had smaller measured IOP responses to ocular hypotensive medication than those with normal or thin corneas. We believe that CCT measurements may be useful in patient management and in interpreting clinical trials of ocular hypotensive medication.

Factors Influencing the Need for Enhancement After Laser in situ Keratomileusis

PURPOSE

To confirm that enhancements after primary laser in situ keratomileusis (LASIK) are effective in dealing with residual refractive errors, and to determine if any variables prior to or during the primary LASIK procedure predisposed eyes to require subsequent enhancement.

METHODS

A retrospective study of eyes undergoing primary LASIK with the VISX S2 or S3 laser and Hansatome microkeratome between January 1, 2000 and January 1, 2002 was done. Of the 393 eyes of 207 patients, 58 eyes (14%) underwent enhancement within a 16-month window of the primary procedure. Statistical comparisons were made between enhanced (n = 37) and non-enhanced (n = 148) patients, and enhanced (n = 48) and non-enhanced (n = 303) eyes, treated for myopia only.

RESULTS

In comparing the primary LASIK parameters of enhanced to non-enhanced eyes in myopic patients, no significant difference was found in right vs left eye, season of the primary treatment, preoperative astigmatism, pachymetry, or amount of attempted astigmatism correction. A multivariate logistic regression analysis revealed that male gender, patient age over 45 years, and a history of recent rigid contact lens use within 6 months of primary LASIK were significantly associated with the need for enhancement.

CONCLUSION

Enhancements were an effective way of dealing with residual refractive errors after primary LASIK. Age greater than 45 years or a history of recent rigid contact lens use were significantly associated with the need for enhancement in patients with myopia or myopic astigmatism.

Retinal nerve fiber layer thickness measurements with scanning laser polarimetry predict glaucomatous visual field loss

PURPOSE

To assess whether baseline retinal nerve fiber layer (RNFL) measurements obtained with a scanning laser polarimeter, the GDx Nerve Fiber Analyzer, (Laser Diagnostic Technologies Inc., San Diego, California) are predictive of development of repeatable glaucomatous visual field damage in glaucoma suspect eyes.

DESIGN

Cohort study.

METHODS

Participants were recruited from the UCSD longitudinal Diagnostic Innovations in Glaucoma Study (DIGS). One eye from each of 160 glaucoma suspects with normal standard automated perimetry (SAP) visual fields at baseline was studied. Study eyes were divided into convert and nonconvert groups based on the development of three consecutive glaucomatous visual fields during follow-up. SLP parameters, IOP, vertical cup disk ratio, stereophotograph assessment as glaucoma or normal, corneal thickness, and visual field indices were included in univariate and multivariate Cox proportional hazards models to determine which SLP RNFL and ocular parameters were predictive of visual field conversion.

RESULTS

Sixteen (10%) eyes developed repeatable visual field damage (converts) and 144 (90%) did not (nonconverts). Mean (95%CI) follow-up time until visual field conversion for convert eyes was 2.7 (1.7, 3.6) years. Mean total follow-up of nonconvert eyes was 3.8 (3.5, 4.1) years. Four out of thirteen examined baseline SLP parameters and baseline SAP Mean Deviation (MD), SAP Pattern Standard Deviation (PSD), and glaucomatous stereophotograph assessment were significant univariate predictors of visual field conversion. In multivariate models adjusted for age, IOP and CCT, SLP parameters inferior ratio, ellipse modulation, and UCSD linear discriminant function (LDF) were significant predictors of visual field conversion. When SAP PSD and stereophotograph assessment were also included in the multivariate model inferior ratio and UCSD LDF remained independently predictive of visual field loss.

CONCLUSIONS

Thinner baseline SLP RNFL measurements were independent predictors of visual field damage. In addition to thinner SLP RNFL measurements, higher baseline SAP PSD, and baseline glaucomatous stereophotograph assessment each contributed to an increased risk of the development of abnormal visual fields in glaucoma suspect patients. SLP RNFL measurements were independently predictive of future visual loss even when age, IOP, CCT, vertical cup disk ratio, and SAP PSD were included in the model.

Baseline risk factors for the development of primary open-angle glaucoma in the Ocular Hypertension Treatment Study

PURPOSE

Higher baseline pattern standard deviation (PSD) and larger vertical cup-to-disk ratio (VC/D) were factors in the predictive model for the development of primary open-angle glaucoma (POAG) in the Ocular Hypertension Treatment Study. Because early changes in PSD and VC/D may be indicative of early POAG damage, we repeated the prediction model excluding PSD and VC/D.

DESIGN

Reanalysis of baseline factors for the development of POAG.

METHODS

We compared the hazard ratios for baseline factors predictive of POAG in the multivariate Cox proportional hazards model that included PSD and VC/D and in the model that excluded them.

RESULTS

Hazard ratios for baseline factors predictive of POAG in Ocular Hypertension Treatment Study were not substantially affected by the inclusion or exclusion of PSD and VC/D in the proportional hazards model.

CONCLUSION

Whether PSD or VC/D was included in the Cox proportional hazards model, the same baseline factors were statistically significant and their hazard ratios were essentially similar.

Predictive factors for glaucomatous visual field progression in the Advanced Glaucoma Intervention Study

PURPOSE

To investigate the risk factors associated with visual field (VF) progression in the Advanced Glaucoma Intervention Study (AGIS) with pointwise linear regression (PLR) analysis of serial VFs.

DESIGN

Prospective, multicenter, randomized clinical trial.

PARTICIPANTS

Five hundred nine eyes of 401 patients from the AGIS with a baseline VF score of <or=16, >or=7 VF examinations, and >or=3 years of follow-up were selected.

MAIN OUTCOME MEASURE

Visual field progression.

METHODS

This is a cohort study of patients enrolled in a prospective randomized clinical trial (AGIS). Worsening of a test location on PLR analysis was defined as a change of threshold sensitivity of >or=1.00 decibels a year, with P<or=0.01. Visual field progression was defined as worsening of at least 2 test locations within a Glaucoma Hemifield Test cluster with PLR analysis. Multivariate logistic regression was used to determine risk factors associated with VF worsening. Intraocular pressure (IOP) fluctuation was defined as standard deviation of the IOP at all visits after the initial surgery.

RESULTS

The mean (+/- standard deviation) follow-up time and baseline AGIS score were 7.4 (+/-1.7) years and 7.7 (+/-4.4), respectively. Visual field progression was detected with PLR analysis in 151 eyes (30%). Older age at the initial intervention (P = 0.0012; odds ratio [OR], 1.30; 95% confidence interval [CI], 1.11-1.50), larger IOP fluctuation (P = 0.0013; OR, 1.31; 95% CI, 1.12-1.54), increasing number of glaucoma interventions (P = 0.01; OR, 1.74; 95% CI, 1.14-2.64), and longer follow-up (P = 0.02; OR, 1.19; 95% CI, 1.03-1.38) were associated with increased odds of VF progression. When regression analyses were repeated in eyes with and without a history of cataract extraction, IOP fluctuation was the only variable to be consistently associated with VF progression.

CONCLUSION

Both increasing age and greater IOP fluctuation increase the odds of VF progression by 30% (for each 5-year increment in age and 1-mmHg increase in IOP fluctuation). The higher risk conferred by IOP fluctuation was consistently observed in eyes with and without a history of cataract extraction.

Glaucoma risk factor assessment and prevention: lessons from coronary heart disease

PURPOSE

To determine whether multivariable risk factor assessment can be as successful in developing disease prevention strategies in patients with ocular hypertension as it has been in patients at risk for coronary heart disease (CHD).

DESIGN

From a literature review of the evolution of the global risk assessment model for CHD, parallels are drawn to the evolution of a global risk assessment methodology for glaucoma.

METHODS

This article summarizes the literature on global risk assessment and prevention of CHD in clinical practice, discusses the development of glaucoma risk assessment based on available trial and population data, and reviews the potential for prevention strategies founded on the cardiovascular disease model.

RESULTS

To improve risk assessment in glaucoma and develop disease management strategies for patients with ocular hypertension, it is first necessary to identify and quantify levels of risk associated with factors that predict disease progression. In addition, the incidence of glaucoma and the average person's life expectancy based on his or her age are needed. Finally, it is necessary to quantify how long it takes to develop a visual defect that affects quality of life once a person develops glaucoma.

CONCLUSION

The systematic application of epidemiologic data to CHD risk factor models provides insights into how global risk assessment can be incorporated into treatment recommendations for managing individuals with glaucoma. It is hoped that ophthalmologists can use the results of future clinical trials and long-term studies to develop disease prevention strategies in patients with ocular hypertension based on multivariable risk assessment.

Applying an evidence-based approach to the management of patients with ocular hypertension: evaluating and synthesizing published evidence

PURPOSE

The use of evidence-based medicine in managing patients with ocular hypertension has been constrained by the limited availability of high-quality data from controlled clinical trials and by limited formal training of clinicians in evaluating published evidence. This article will provide strategies and techniques to evaluate critically the quality of published research, synthesize the findings, and integrate published evidence in the care of patients with ocular hypertension.

DESIGN

Review of the published literature and consensus of a panel of experts.

METHODS

The published literature on evidence-based medicine was reviewed. Strategies and techniques in evaluating the quality of evidence and how to integrate evidence into the practice setting using the following three major questions were discussed by a panel of experts: Are the results of the study valid? What are the results? Do the study outcomes apply to individual patient care?

RESULTS

Approaches to assessing study validity and the importance of considering the size of the treatment effect and precision of the effect size were detailed. The importance of using the "number-needed-to-treat" as a tool for translating results of clinical trials to individual patient care and the "number-needed-to-harm" as a method of comparing the potential benefit and harm of a given therapy was acknowledged.

CONCLUSION

As the volume of high-quality data increases, the information provided herein may help ophthalmologists apply evidence-based medicine techniques as they seek to optimize the care of individual patients with ocular hypertension.

Risk assessment in the management of patients with ocular hypertension

PURPOSE

To develop a model for estimating the global risk of disease progression in patients with ocular hypertension and to calculate the "number-needed-to-treat" (NNT) to prevent progression to blindness as an aid to practitioners in clinical decision making.

DESIGN

Development of a mathematical model for estimating risk of glaucoma progression.

METHODS

Population-based studies of patients with ocular hypertension and glaucoma were reviewed by a panel of glaucoma specialists. Measures of disease progression risks derived from three long-term studies and assumptions based on the available data were used to estimate the risk of progression from ocular hypertension to glaucoma and glaucoma to unilateral blindness for untreated and treated patients over a 15-year period. Using these estimates, the NNT (1/absolute risk reduction on treatment) to prevent unilateral blindness in one patient with ocular hypertension was calculated.

RESULTS

In untreated patients, the estimated risk of progression from ocular hypertension to unilateral blindness was 1.5% to 10.5% and in treated patients, the estimated risk of progression was 0.3% to 2.4% over 15 years. From these estimates, between 12 and 83 patients with ocular hypertension will require treatment to prevent one patient from progressing to unilateral blindness over a 15-year period.

CONCLUSION

Global risk assessment that incorporates all available data plays a vital role in managing patients with ocular hypertension. A more precise understanding of long-term vision loss should be factored into decisions pertaining to the initiation of glaucoma therapy. Undoubtedly, these estimates will evolve and change with the availability of new population-based epidemiologic information and improvements in multivariable model testing.

An evidence-based assessment of risk factors for the progression of ocular hypertension and glaucoma

PURPOSE

To critically review the existing literature concerning risk factors for progression of ocular hypertension and glaucoma to assist in assigning levels of risk for individual patients.

DESIGN

Evidence-based review.

METHODS

A panel of physicians specializing in treatment of glaucoma patients was convened to critically analyze published population-based studies of ocular hypertension and glaucoma progression. The strength of evidence in support of reported risk factors was weighed.

RESULTS

Many putative risk factors for progression of ocular hypertension or glaucoma have been reported in the literature. The risk factors most strongly supported by evidence are higher intraocular pressure (IOP), greater cup-to-disk ratio, thinner central corneal measurement, and older age. Black race does not appear to be an independent risk factor, although black individuals tend to have thinner corneas, greater cup-to-disk ratios, and higher IOP, which increase their risk. The limited number of studies in which other suspected risk factors are reported prevents drawing firm conclusions about their importance at this time.

CONCLUSIONS

Only a subset of patients with ocular hypertension will eventually develop glaucoma. Decisions regarding the implementation and extent of therapy for ocular hypertension can be difficult and require an understanding of the relative importance of risk factors for progression. This review discusses the strength of evidence supporting reported risk factors and may be useful in assessing the risk for progression of individual patients.

Using unsupervised learning with variational bayesian mixture of factor analysis to identify patterns of glaucomatous visual field defects

PURPOSE

To determine whether an unsupervised machine learning classifier can identify patterns of visual field loss in standard visual fields consistent with typical patterns learned by decades of human experience.

METHODS

Standard perimetry thresholds for 52 locations plus age from one eye of each of 156 patients with glaucomatous optic neuropathy (GON) and 189 eyes of healthy subjects were clustered with an unsupervised machine classifier, variational Bayesian mixture of factor analysis (vbMFA).

RESULTS

The vbMFA formed five distinct clusters. Cluster 5 held 186 of 189 fields from normal eyes plus 46 from eyes with GON. These fields were then judged within normal limits by several traditional methods. Each of the other four clusters could be described by the pattern of loss found within it. Cluster 1 (71 GON + 3 normal optic discs) included early, localized defects. A purely diffuse component was rare. Cluster 2 (26 GON) exhibited primarily deep superior hemifield defects, and cluster 3 (10 GON) held deep inferior hemifield defects only or in combination with lesser superior field defects. Cluster 4 (6 GON) showed deep defects in both hemifields. In other words, visual fields within a given cluster had similar patterns of loss that differed from the predominant pattern found in other clusters. The classifier separated the data based solely on the patterns of loss within the fields, without being guided by the diagnosis, placing 98.4% of the healthy eyes within the same cluster and spreading 70.5% of the eyes with GON across the other four clusters, in good agreement with a glaucoma expert and pattern standard deviation.

CONCLUSIONS

Without training-based diagnosis (unsupervised learning), the vbMFA identified four important patterns of field loss in eyes with GON in a manner consistent with years of clinical experience.

Association between mean intraocular pressure, disease stability and cost of treating glaucoma in Canada

PURPOSE

A retrospective analysis determined the association between intraocular pressure (IOP) control levels (mean and last IOP) and disease stability, and the association between IOP and yearly treatment cost in primary open angle glaucoma (POAG).

METHODS

Data were collected from POAG patients, referred to a tertiary glaucoma clinic. All IOP measurements, visual field mean deviation (VF) scores, physicians' impressions, and resources used (physician visits, procedures, and medications) were recorded and costed using standard resource unit cost lists from the Ministry of Health's perspective. Patients were categorized by the average VF score of their first three visits [mild (< 5 dB), moderate (> or = 5 dB to < 12 dB) and severe (> or = 12 dB)]. Pearson's r quantified the association between IOP control levels and stability, where stability was defined by the physician's subjective impression of the patient's disease. Spearman's rho was determined to quantify association between mean IOP and yearly treatment cost within VF categories.

RESULTS

Four hundred and eleven charts were reviewed of which 265 were acceptable for analysis. A negative relationship was determined between the probability of reaching stability and mean IOP in all three VF severity groups. Pearson's r was -0.68 (p < 0.001), -0.72 (p < 0.001), and -0.52 (p < 0.001) for the mild, moderate, and severe groups, respectively. A similar correlation was determined between the last measured IOP and stability. Pearson's r was -0.49 (p < 0.001), -0.80 (p < 0.001), and -0.65 (p < 0.001) for the mild, moderate and severe groups, respectively. A positive relationship was reported between mean yearly costs and IOP. Spearman's rho between mean yearly costs and mean IOP was 0.11 (p = 0.28), 0.23 (p < 0.05), and 0.26 (p < 0.05) for each respective VF level.

DISCUSSION AND CONCLUSION

Lower IOP control levels are associated with higher probabilities of stability. In addition, lower IOP control levels are associated with lower costs of managing POAG in patients either with moderate VF loss or with severe VF loss. Economic burden increased with increasing disease severity.

How prostaglandins have changed the medical approach to glaucoma and its costs: an observational study of 2228 patients treated with glaucoma medications

PURPOSE

The aim of the present study was to investigate how the medical treatment of glaucoma changed between 1997 and 2002, since the advent of prostaglandin derivatives, with regard to drug prescriptions and pharmaceutical costs.

METHODS

A study was made of medical prescriptions for 2228 patients with glaucoma and/or ocular hypertension, in order to investigate the following: (i) the antiglaucoma drugs most commonly prescribed in 1997 and 2002, and any differences between the drugs prescribed in these 2 years; (ii) the number of drugs used per patient in 1997 and 2002, respectively, and (iii) any increase in the prescribing of antiglaucoma drugs and their relative costs from 1997 to 2002.

RESULTS

From 1997 to 2002 there was a sharp drop in the prescribing of beta-blockers (79% in 1997 and 55% in 2002). A marked increase in the use of prostaglandin derivatives (0% in 1997 and 18% in 2002) was registered and a marked increase in the prescribing of carbonic anhydrase inhibitors (5% in 1997 and 14% in 2002) was also noted. From 1997 to 2002 there was a trend towards drug addition rather than substitution, so that the number of drugs used per patient increased. The number of patients treated increased enormously (by 98%) from 1997 to 2002. The cost of medical therapy from 1997 to 2002 rose dramatically, with an increase of 148.9% per patient.

CONCLUSION

The availability of prostaglandin derivatives has strongly influenced the medical approach to glaucoma. This class of drugs will soon become the type most commonly prescribed for patients with glaucoma and/or ocular hypertension. The increased number of treatments also suggests that the approach of ophthalmologists towards these diseases has changed. Ocular hypertension, as well as glaucoma, is now treated more aggressively. Given the increase in the prescription of prostaglandin derivatives, the pharmaceutical cost of treatment has risen dramatically.

Confocal scanning laser ophthalmoscopy classifiers and stereophotograph evaluation for prediction of visual field abnormalities in glaucoma-suspect eyes

PURPOSE

To determine whether Heidelberg Retina Tomograph (HRT; Heidelberg Engineering, Dossenheim, Germany) classification techniques and investigational support vector machine (SVM) analyses can detect optic disc abnormalities in glaucoma-suspect eyes before the development of visual field abnormalities.

METHODS

Glaucoma-suspect eyes (n = 226) were classified as converts or nonconverts based on the development of repeatable (either two or three consecutive) standard automated perimetry (SAP)-detected abnormalities over the course of the study (mean follow-up, approximately 4.5 years). Hazard ratios for development of SAP abnormalities were calculated based on baseline classification results, follow-up time, and end point status (convert, nonconvert). Classification techniques applied were HRT classification (HRTC), Moorfields Regression Analysis, forward-selection optimized SVM (SVM fwd) and backward elimination-optimized SVM (SVM back) analysis of HRT data, and stereophotograph assessment.

RESULTS

Univariate analyses indicated that all classification techniques were predictors of the development of two repeatable abnormal SAP results, with hazards ratios (95% confidence interval [CI]) ranging from 1.32 (1.00-1.75) for HRTC to 2.0 (1.48-2.76) for stereophotograph assessment (all P < or = 0.05). Only SVM (SVM fwd and SVM back) analysis of HRT data and stereophotograph assessment were univariate predictors of the development of three repeatable abnormal SAP results, with hazard ratios (95% CI) ranging from 1.73 (1.16-2.82) for SVM fwd to 1.82 (1.19-3.12) for SVM back (both P < 0.007). Multivariate analyses including each classification technique individually in a model with age, baseline SAP pattern standard deviation [PSD], and baseline IOP indicated that all classification techniques except HRTC (P = 0.06) were predictors of the development of two repeatable abnormal SAP results with hazards ratios ranging from 1.30 (0.99, 1.73) for HRTC to 1.90 (1.37, 2.69) for stereophotograph assessment. Only SVM (SVM fwd and SVM back) analysis of HRT data and stereophotograph assessment were significant predictors of the development of three repeatable abnormal SAP results in multivariate analyses; hazard ratios of 1.57 (1.03, 2.59) and 1.70 (1.18, 2.51), respectively. SAP PSD was a significant predictor of two repeatable abnormal SAP results in multivariate models with all classification techniques, with hazard ratios ranging from 3.31 (1.39, 7.89) to 4.70 (2.02, 10.93) per 1-dB increase.

CONCLUSIONS

HRT classifications techniques and stereophotograph assessment can detect optic disc topography abnormalities in glaucoma-suspect eyes before the development of SAP abnormalities. These data support strongly the importance of optic disc examination for early glaucoma diagnosis.

A 6-month randomized clinical trial of bimatoprost 0.03% versus the association of timolol 0.5% and latanoprost 0.005% in glaucomatous patients

BACKGROUND

New effective hypotensive agents have been recently introduced into clinical practice, but often more than one drug has to be used to prevent further visual field loss. The aim of this study was to evaluate the intraocular pressure (IOP)-lowering efficacy and safety of bimatoprost 0.03% compared with the association of timolol 0.5% and latanoprost 0.005% in open-angle glaucoma patients.

METHODS

In this 6-month, prospective, parallel, randomised, investigator-masked clinical trial, 61 glaucomatous patients treated with timolol 0.5% twice in both eyes were enrolled. The timolol 0.5% was replaced by bimatoprost 0.03% once daily (group I) or by latanoprost 0.005% plus timolol 0.5% (group II). IOP measurements were performed at the baseline visit and at days 15, 30, 60, 90, 120 and 180. Digital colour photography was used to evaluate topical side effects.

RESULTS

Fifty-six of the 61 patients were included for the intent-to-treat analysis (28 in group I and 28 in group II). Baseline mean IOP was similar in the two groups (p=0.5). Both treatments lowered the mean IOP at every visit significantly compared with the baseline (p<0.01). Comparing the IOP reductions obtained by the two treatments, no significant differences were found at any time during the study. Conjunctival hyperaemia, skin pigmentation and eyelash growth in group I and headache in group II were the most common side effects observed during the study.

CONCLUSIONS

Bimatoprost and the association of latanoprost plus timolol were equally effective in lowering the IOP in glaucomatous patients previously treated with timolol. Latanoprost plus timolol showed a better ocular safety profile.

Primary open-angle glaucoma

Primary open-angle glaucoma is a progressive optic neuropathy and, perhaps, the most common form of glaucoma. Because the disease is treatable, and because the visual impairment caused by glaucoma is irreversible, early detection is essential. Early diagnosis depends on examination of the optic disc, retinal nerve fibre layer, and visual field. New imaging and psychophysical tests can improve both detection and monitoring of the progression of the disease. Recently completed long-term clinical trials provide convincing evidence that lowering intraocular pressure prevents progression at both the early and late stages of the disease. The degree of protection is related to the degree to which intraocular pressure is lowered. Improvements in therapy consist of more effective and better-tolerated drugs to lower intraocular pressure, and more effective surgical procedures. New treatments to directly treat and protect the retinal ganglion cells that are damaged in glaucoma are also in development.

Frequency doubling technology perimetry abnormalities as predictors of glaucomatous visual field loss

PURPOSE

To determine whether frequency doubling technology (FDT) perimetry results predict glaucomatous visual field defects, as assessed by standard automated perimetry (SAP), in a glaucoma suspect population.

DESIGN

Longitudinal observational study.

METHODS

The study included 105 eyes of 105 glaucoma suspect patients, with a mean follow-up time of 41 +/- 17 months. Glaucoma suspects had either intraocular pressure (IOP) higher than or equal to 23 mm Hg or glaucomatous optic neuropathy by stereophotograph assessment. All patients had normal SAP visual fields at baseline. A baseline FDT test was performed within 3 months of the normal SAP examination. Several baseline FDT parameters and other variables (age, gender, IOP, central corneal thickness, SAP visual field indices, and stereophotograph assessment) were investigated by univariate and multivariate Cox proportional hazards models to obtain hazard ratios (HR) and identify factors that predicted which patients had SAP glaucomatous visual field loss during follow-up.

RESULTS

Seventeen patients (16%) developed repeatable SAP visual field abnormality during follow-up. An abnormal FDT examination at baseline predicted the development of SAP visual field conversion in both univariate (HR = 3.17; 95% confidence interval [CI] = 1.22-8.25; P =.018) and multivariate models (Adjusted HR = 3.68; 95% CI = 1.06-12.8; P =.04). The analysis of FDT examinations during follow-up revealed that in 59% of converters the FDT abnormalities preceded SAP visual field loss by as much as 4 years. Also, the initial development of glaucomatous visual field loss as measured by SAP occurred in regions that had previously demonstrated abnormalities on FDT testing.

CONCLUSION

Functional abnormalities detected by FDT perimetry were predictive of the future onset and location of SAP visual field loss among glaucoma suspect patients.