Central corneal thickness in the Ocular Hypertension Treatment Study (OHTS)

OBJECTIVE

Central corneal thickness influences intraocular pressure (IOP) measurement. We examined the central corneal thickness of subjects in the Ocular Hypertension Treatment Study (OHTS) and determined if central corneal thickness is related to race.

DESIGN

Cross-sectional study.

PARTICIPANTS

One thousand three hundred one OHTS subjects with central corneal thickness measurements.

INTERVENTION

Central corneal thickness was determined with ultrasonic pachymeters of the same make and model at all clinical sites of the OHTS.

MAIN OUTCOME MEASURES

Correlation of mean central corneal thickness with race, baseline IOP, refraction, age, gender, systemic hypertension, and diabetes.

RESULTS

Mean central corneal thickness was 573.0 +/- 39.0 microm. Twenty-four percent of the OHTS subjects had central corneal thickness > 600 microm. Mean central corneal thickness for African American subjects (555.7 +/- 40.0 microm; n = 318) was 23 microm thinner than for white subjects (579.0 +/- 37.0 microm; P < 0.0001). Other factors associated with greater mean central corneal thickness were younger age, female gender, and diabetes.

CONCLUSIONS

OHTS subjects have thicker corneas than the general population. African American subjects have thinner corneas than white subjects in the study. The effect of central corneal thickness may influence the accuracy of applanation tonometry in the diagnosis, screening, and management of patients with glaucoma and ocular hypertension.

Corneal scarring and vision in keratoconus: a baseline report from the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study

PURPOSE

The multicenter Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is a prospective, observational study of 1,209 keratoconus patients. We report on the correlation of corneal scarring with clinical and patient-reported variables at the baseline visit.

METHODS

Patients completed a questionnaire on their vision, effect of glare, contact lens wear, and work-related issues. Clinical examination included high- and low-contrast visual acuity, refraction, assessment of corneal scarring by the clinician and by photography, and measurement of corneal curvature. The correlation of central corneal scarring with visual acuity and patient-reported variables was analyzed using multiple regression analysis and generalized estimating equations.

RESULTS

High- and low-contrast visual acuity with habitual and optimal correction is reduced in scarred eyes. Multiple regression analyses controlling for age, contact lens wear, and disease severity show that central scarring is associated with poorer visual acuity and increased patient-reported symptoms of glare. Restrictions on day-to-day activities do not appear to be associated with corneal scarring above and beyond the effects of keratoconus alone.

CONCLUSIONS

Corneal scarring in keratoconus is significantly associated with decreased high- and low-contrast visual acuity.

Contralateral effect of topical beta-adrenergic antagonists in initial one-eyed trials in the ocular hypertension treatment study

PURPOSE

To evaluate the magnitude of the contralateral effect of topically administered beta-blockers on intraocular pressure.

METHODS

The Ocular Hypertension Treatment Study enrolled 1,636 subjects. Of these, 817 subjects were randomized to receive topical ocular hypotensive medication and 819 subjects were randomized to close observation (i.e., no topical medication). We compared the intraocular pressure of the contralateral eye of subjects at the baseline visit and after an initial one-eyed therapeutic trial of topical beta-blockers. We examined differences between baseline and follow-up intraocular pressure in untreated eyes of subjects randomized to close observation.

RESULTS

The mean reduction in intraocular pressure in the beta-blocker-treated eyes was -5.9 +/- 3. 4 mm Hg (-22% +/- 12%; Student t test, P <.0001). In the contralateral eyes, mean intraocular pressure reduction was -1.5 +/- 3.0 mm Hg (-5.8% +/- 12%; P <.0001). Of the contralateral eyes, 35% showed a reduction of 3 mm Hg or more, and 10% showed a reduction of 6 mm Hg or more. The contralateral effect of the relatively selective beta-blocker betaxolol did not differ from that of any of the nonselective beta-blockers. Factors associated with the magnitude of the contralateral effect were the degree of intraocular pressure reduction in the treated eye and baseline intraocular pressure of the contralateral eye. In the close observation group, no significant reduction in intraocular pressure was noted between the baseline and follow-up visit.

CONCLUSIONS

The contralateral effect is important in clinical practice and in clinical trials when the hypotensive effect of a topical beta-blocker is evaluated by means of a one-eyed therapeutic trial.

Confirmation of visual field abnormalities in the Ocular Hypertension Treatment Study. Ocular Hypertension Treatment Study Group

OBJECTIVE

To determine the frequency with which visual field abnormalities observed on follow-up visual fields for patients in the Ocular Hypertension Treatment Study were confirmed on retest.

METHODS

Between April 1, 1994, and March 1, 1999, 21,603 visual fields were obtained from 1637 patients in the Ocular Hypertension Treatment Study. When follow-up visual fields are outside the normal limits on the Glaucoma Hemifield Test, the Corrected Pattern Standard Deviation (P<.05), or both, subsequent follow-up visual fields are monitored to confirm the abnormality. Abnormalities are confirmed if they are again abnormal on the Glaucoma Hemifield Test, the Corrected Pattern Standard Deviation, or both; if the defect is not artifactual; and if the same index and location are involved. Reliability criteria used by the study consisted of a limit of 33% for false positives, false negatives, and fixation losses.

RESULTS

Of the 21,603 regular follow-up visual fields, 1006 were follow-up retests performed because of an abnormality (n = 748) or unreliability (n = 258). We found that 703 (94%) of the 748 visual fields were abnormal and reliable, and 45 (6%) were abnormal and unreliable. On retesting, abnormalities were not confirmed for 604 (85.9%) of the 703 originally abnormal and reliable visual fields.

CONCLUSIONS

Most visual field abnormalities in patients in the Ocular Hypertension Treatment Study were not verified on retest. Confirmation of visual field abnormalities is essential for distinguishing reproducible visual field loss from long-term variability. Arch Ophthalmol. 2000;118:1187-1194

Factors associated with corneal scarring in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study

PURPOSE

The multicenter Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is a prospective, observational study of 1,209 keratoconus patients. We report on the factors associated with corneal scarring at baseline.

METHODS

We defined corneal scarring as scars that had been detected both by the clinician examining the patient with the slit-lamp biomicroscope and by masked readers of corneal photographs at the CLEK Photography Reading Center. We investigated associations between corneal scarring and patient variables including gender, ethnicity, a family history of keratoconus, a history of ocular trauma, eye rubbing, contact lens wear, rigid contact lens fitting relationships, and corneal findings (such as curvature, Vogt's striae, Fleischer's ring, and central/apical staining). Multiple logistic regression analysis using generalized estimating equations to adjust for the correlation between eyes was used for analysis.

RESULTS

The following factors were found to increase the odds of corneal scarring at baseline in the CLEK Study: corneal staining (odds ratios (OR) = 3.40, 95% confidence interval 2.53-4.59), contact lens wear (OR = 3.51, 95% confidence interval 2.27-5.45), Fleischer's ring (OR = 1.63, 95% confidence interval 1.11-2.40), steeper first definite apical clearance lens base curve radius (per diopter, OR = 1.29, 95% confidence interval 1.25-1.33), and age (per decade, OR = 1.54, 95% confidence interval 1.35-1.75).

CONCLUSIONS

These baseline data suggest that corneal scarring in keratoconus is associated with corneal staining, contact lens wear, Fleischer's ring, a steeper cornea, and increasing age. The factors that imply added risk for corneal scarring that may be affected by practitioner intervention are staining of the cornea, contact lens wear, and the contact lens fitting relationship.

Rigid contact lens fitting relationships in keratoconus. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group

PURPOSE

Although the influence of flat-fitting contact lenses on corneal scarring in keratoconus is frequently debated, the current standard of care with regard to the apical fitting relationship in keratoconus remains undocumented.

METHODS

Patients were examined at baseline in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study (N = 1209). Patients wearing a rigid contact lens in one or both eyes (N = 808) had their habitual rigid contact lenses analyzed, and the fluorescein patterns and base curves were compared to the first definite apical clearance lens (FDACL). The FDACL is the flattest lens in the CLEK Study trial lens set that exhibits an apical clearance fluorescein pattern. For patients wearing a rigid contact lens in both eyes, one eye was selected randomly for analysis.

RESULTS

Twelve percent of the rigid contact lens-wearing eyes were wearing lenses fitted with apical clearance based upon the clinician's fluorescein pattern interpretation. The remainder (88%) was wearing lenses fitted with apical touch. For mild (steep keratometric reading <45 D) keratoconus corneas, the mean estimate of the base curve to cornea-fitting relationship was 1.18 D flat (SD +/- 1.84 D); moderate (steep keratometric reading: 45 to 52 D) corneas were fitted on average 2.38 D flat (SD +/- 2.56 D); and severe (steep keratometric reading > 52 D) corneas were fitted an average of 4.01 D flat (SD +/- 4.11 D).

CONCLUSIONS

Despite the potential risk for corneal scarring imposed by flat-fitting rigid contact lenses, most CLEK Study patients wear flat-fitting lenses. Overall, rigid lenses were fitted an average of 2.86 D (SD +/- 3.31 D) flatter than the FDACL.

The Ocular Hypertension Treatment Study: design and baseline description of the participants

BACKGROUND

The Ocular Hypertension Treatment Study (OHTS) seeks to evaluate the safety and efficacy of topical ocular hypotensive medication in preventing or delaying the onset of visual field loss and/or optic nerve damage in subjects with ocular hypertension at moderate risk for developing primary open angle glaucoma.

OBJECTIVE

To describe the study protocol, the questions to be answered, and the baseline characteristics of the subjects.

DESIGN

Multicenter randomized clinical trial with 2 groups: topical ocular hypotensive medication and close observation.

SETTING

Subjects were enrolled and evaluated at 22 participating clinical centers. Visual fields and stereoscopic optic disc photographs were read in masked fashion.

METHODS

We determined eligibility from a comprehensive eye examination, medical and ocular history, visual field testing, and stereoscopic optic disc photography.

RESULTS

We describe the baseline characteristics of 1637 subjects randomized between February 28, 1994, and October 31, 1996. The mean age was 55 years; 56.9% of the subjects were women; and 25% were African American. The baseline intraocular pressure was 24.9 +/- 2.7 mm Hg (mean +/- SD). Systemic diseases and conditions reported by subjects included previous use of medication for ocular hypertension, 37%; systemic hypertension, 38%; cardiovascular disease, 6%; diabetes mellitus, 12%; and family history of glaucoma, 44%. The mean horizontal cup-disc ratio by contour estimated from stereophotography was 0.36 +/- 0.18. Qualifying Humphrey 30-2 visual fields had to be normal and reliable for entry into the study. Health-related quality of life (36-item short form health survey) scores in the OHTS sample were better than the age- and sex-matched population norms. African American subjects had larger baseline cup-disc ratios and higher reported rates of elevated blood pressure and diabetes than the rest of the subjects.

CONCLUSIONS

The intraocular pressure among enrolled subjects was sufficiently high to provide an adequate test of the potential benefit of ocular hypotensive medication in preventing or delaying glaucomatous damage. The large number of African American subjects enrolled should provide a good estimate of the African American response to topical medication.

Corneal scarring in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study: baseline prevalence and repeatability of detection

PURPOSE

The multicenter Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is a prospective, observational study of 1,209 keratoconus patients. We report on the prevalence of corneal scarring in these patients. We also report on the test-retest repeatability of corneal scar documentation at the slit-lamp biomicroscope by trained clinicians and by masked photograph readers and on the scarring-status agreement at baseline between clinicians and photograph readers.

METHODS

Clinicians and masked photograph readers graded each cornea as to scarring status. Patients were examined by clinicians, and their corneas were photographed at baseline (2,297 nongrafted eyes of 1,209 patients) and at a repeated visit (258 nongrafted eyes of 138 patients). These photographs were evaluated by the masked readers at the CLEK Photography Reading Center (CPRC). Clinicians reported corneal scars in right eyes at baseline as "definitely not present" in 53.9%, "probably not present" in 8.4%, "probably present" in 8.2%, and "definitely present" in 29.4% of patients. A weighted kappa statistic of 0.83 (95% confidence interval from 0.78 to 0.88) indicates that agreement is excellent between baseline and repeated assessments for the presence of a corneal scar by clinicians.

RESULTS

Agreement is very good between baseline and repeated photograph-reader assessments for the presence of a scar, with a weighted kappa of 0.77 (95% confidence interval, 0.72-0.82). The kappa statistic comparing photograph-reader scarring assessments with clinician results was 0.69 (95% confidence interval, 0.66-0.71).

CONCLUSION

The data also suggest better agreement between clinicians and readers when Vogt's striae and corneal nerves were observed. The data also suggest better agreement when corneal staining was not observed by the photograph readers. The CLEK Study protocol for determining the presence of scars is highly repeatable.

Baseline findings in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study

PURPOSE

To describe the baseline findings in patients enrolled in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study.

METHODS

This is a longitudinal observational study of 1209 patients with keratoconus enrolled at 16 clinical centers. Its main outcome measures are corneal scarring, visual acuity, keratometry, and quality of life.

RESULTS

The CLEK Study patients had a mean age of 39.29+/-10.90 years with moderate to severe disease, assessed by a keratometric-based criterion (95.4% of patients had steep keratometric readings of at least 45 D) and relatively good visual acuity (77.9% had best corrected visual acuity of at least 20/40 in both eyes). Sixty-five percent of the patients wore rigid gas-permeable contact lens, and most of those (73%) reported that their lenses were comfortable. Only 13.5% of patients reported a family history of keratoconus. None reported serious systemic diseases that had been previously reported to be associated with keratoconus. Many (53%) reported a history of atopy. Fifty-three percent had corneal scarring in one or both eyes.

CONCLUSIONS

Baseline findings suggest that keratoconus is not associated with increased risk of connective tissue disease and that most patients in the CLEK Study sample represent mild to moderate keratoconus. Additional follow-up of at least 3 years will provide new information about the progression of keratoconus, identify factors associated with progression, and assess its impact on quality of life.

Repeatability and agreement of two corneal-curvature assessments in keratoconus: keratometry and the first definite apical clearance lens (FDACL). CLEK Study Group. Collaborative Longitudinal Evaluation of Keratoconus

PURPOSE

This study was conducted to determine the agreement and test-retest repeatability of two methods for measuring corneal curvature in keratoconus: keratometry and the First Definite Apical Clearance Lens (FDACL). Our interest in the FDACL procedure stems from the important contact lens-fitting information and documentation of disease progression provided by the FDACL trial lenses and observation of fluorescein patterns.

METHODS

The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is an observational study that has enrolled 1,209 keratoconus patients to characterize the progression of keratoconus, to determine factors associated with its progression, and to assess its impact on quality of life. Ten percent of the patients were randomly selected at baseline for a retest examination. The baseline examination, which included keratometry and FDACL, was repeated in this sample. The FDACL is the flattest lens in the standardized CLEK trial lens set that vaults the apex of the cone. FDACL provides an estimate of the sagittal height of the cone.

RESULTS

The correlation of FDACL with the steep keratometric reading (r = 0.89; p = 0.0001) and the flat keratometric reading (r = 0.83; p = 0.0001) were high. Test-retest repeatability as measured by the intraclass correlation coefficient (ICC) was high: FDACL ICC, 0.97; steep keratometric reading ICC, 0.96; and flat keratometric reading ICC, 0.95. Test-retest repeatability of FDACL remained high in advanced disease.

CONCLUSION

FDACL provides a repeatable new procedure for determining disease severity in keratoconus.

Visual acuity repeatability in keratoconus: impact on sample size. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group

PURPOSE

The purpose of this paper is to determine the repeatability of visual acuity measurement in keratoconus and to describe the impact of measurement repeatability on sample size.

METHODS

Approximately 10% of a 1209 patient sample in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study were selected randomly for a Repeat CLEK Study Visit. Patients were tested at the 15 CLEK Participating Clinics. The test-retest sample consisted of 1 34 keratoconus patients who met the entry criteria of the CLEK Study. High and low contrast Bailey-Lovie visual acuity was measured with the patient's habitual visual correction (entrance visual acuity monocularly and binocularly), and with the best correction monocularly (either the patient's rigid contact lens and over-refraction, or with a CLEK Study trial lens and appropriate over-refraction) at two visits separated by a median of 90 days (range 22 to 268 days).

RESULTS

The mean absolute differences between the number of letters correct at the two visits ranged from a low of 3.24 +/- 3.1 for entrance high contrast binocular acuity to a high of 5.48 +/- 5.1 for best corrected low contrast monocular acuity. Intraclass correlation coefficients ranged from 0.757 to 0.853. The visual acuity score was somewhat higher at the Repeat Visit than at the Baseline Visit when the examiners were different between visits.

CONCLUSIONS

Given the variable vision reported by keratoconus patients, visual acuity in this sample was very repeatable. Repeatability was slightly poorer when different examiners tested visual acuity at the Baseline and Repeat Visits.

Feasibility of fitting contact lenses with apical clearance in keratoconus

Despite the wide variety of rigid contact lens fitting philosophies for the visual correction of keratoconus, questions remain, including which approach-flat, divided support, or steep-contributes the most toward the preservation of a clear cornea. One goal of the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Pilot Study was to determine the feasibility of managing early keratoconus patients with apical clearance rigid contact lenses. Of 30 keratoconus patients identified with at least 1 nonscarred cornea, 17 patients (30 eyes) were randomly assigned to a steep lens fitting protocol. After trial fitting with a standardized lens design demonstrating minimum apical clearance, lenses were dispensed whose base curve was 0.2 mm steeper than the minimum apical clearance lens. Patients were re-evaluated on a quarterly schedule concluding at 12 months. Changes in keratometry between baseline and 12 months identified unequal steepening of the flat and steep corneal curvatures, suggestive of corneal molding. Best corrected rigid lens visual acuity measures illustrated no significant changes over the course of the study. Clinically significant corneal compromise was transiently observed in some patients. Only 1 of 22 eyes completing the pilot study and fitted with apical clearance developed mild corneal scarring.

Standardized rigid contact lens fitting protocol for keratoconus

Keratoconus is typically managed by a variety of rigid contact lens fitting techniques and lens designs. The two most fundamental fitting techniques are apical corneal touch (including divided or three-point touch) and apical clearance. In the course of designing a multi-center study of keratoconus patients, a standardized keratoconus fitting protocol was developed. All contact lens parameter options are uniform except for base curve and secondary curve radii, which are determined by interpretation of fluorescein patterns using the CLEK Study trial lens set and protocol. The initial trial lens's base curve is the average keratometric reading; sequentially steeper lenses are applied until definite apical clearance is observed. We have evaluated the feasibility of this standardized fitting protocol on 30 keratoconus patients. Our results suggest that we have developed a standardized contact lens fitting set and fitting protocol to simplify contact lens management in patients with mild to moderate keratoconus.

Photodocumentation of Corneal Scarring

PURPOSE

A standardized system for photodocumenting corneal scars and for evaluating these photographs does not exist and is essential for clinical research. To address this need, we developed a system for photographing and evaluating corneal scars.

METHODS

In the "Development Phase," we tested several procedures in small samples totaling 40 eyes of 20 keratoconus patients. In the "Test Phase," we used an independent sample of 150 eyes of 82 keratoconus patients. Fifty-nine of these 150 eyes had corneal scars, and 91 of the eyes did not as determined by the clinician.

RESULTS

The photography protocol requires four central parallelepiped and two whole cornea oblique photographs after pupil dilation. With the clinician as gold standard, this technique yielded sensitivity of 96% and specificity of 83%. Evaluation of the corneal photographs as to the presence or absence of corneal scarring was performed independently by two masked readers. Agreement between clinicians on the presence of corneal scarring was 0.99 (kappa); agreement between readers for the presence of scarring was 0.80 (kappa).

CONCLUSIONS

The corneal photography protocol we describe is recommended for use in clinical investigations of cicatricizing corneal disease and appears robust enough to be used in multicenter studies.

Biomicroscopic signs and disease severity in keratoconus. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group

The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Survey represents the largest sample of clinic-based keratoconus patients to date. Data were collected at 38 clinical centers on 1,579 keratoconus patients. This article reports demographic variable, ages, self-reported ages at diagnosis, keratometry, slit-lamp findings, systemic disease, family history of keratoconus, and best spectacle-corrected and contact lens-corrected visual acuity of this sample group. The average age of this clinic-based sample group was 37 years (range 10-89 years), with 84% between 20 and 49 years old. Thirteen percent of patients had unilateral keratoconus, defined as unilateral corneal irregularity. More advanced disease (steeper average keratometric reading) was associated with a greater likelihood of Vogt's striae, Fleischer's ring, and/or corneal scarring. Fifty-eight percent of the eyes in this group of patients had > or = 20/40 visual acuity with manifest refraction. Penetrating keratoplasty was reported in 12.3% of eyes. This prospective survey identifies the associates between the presence of Vogt's striae, Fleischer's ring, and/or corneal scarring and increasing steepness, as measured by keratometry.

The effect of poor compliance and treatment side effects on sample size requirements in randomized clinical trials

Treatment side effects and associated noncompliance have methodological implications vital to the testing of new drugs. In this paper, we quantify the impact of these factors on sample size requirements in clinical trials. In the Lipid Research Clinics Trial, side effects caused treatment group compliance (50.8%) to be lower than placebo compliance (67.3%). Cholesterol reduction among treatment noncompliers was 35.2% of the reduction among compliers. Had treatment group compliance been as high as placebo compliance, 41% fewer patients would have been required to achieve the same statistical power and an expected 31% more coronary events would have been prevented. We conclude: Because they discourage patient compliance, treatment side effects can (1) cause large sample size increases, (2) lead to underestimates of true efficacy, and (3) contribute to potentially invalid negative conclusions in clinical trials. The impact of side effects goes well beyond the complications and patient discomforts with which they are associated.

Postcataract ptosis. A randomized, double-masked comparison of peribulbar and retrobulbar anesthesia

PURPOSE

A randomized, double-masked study of 317 patients was conducted to determine if the incidence of postcataract ptosis is greater with retrobulbar or two-injection peribulbar injection anesthesia.

METHODS

Surgery consisted of a planned extracapsular extraction with posterior chamber lens implantation, and no superior rectus bridle suture was used. Ptosis was quantitatively documented preoperatively and postoperatively at 1, 2, 5, and 90 days by the surgeon, photographically at 90 days by a masked observer, and subjectively by the patients. Postcataract ptosis was defined as a drop in the lid margin of 2 mm or greater after correcting for any change in the fellow eye.

RESULTS

The incidence of ptosis at 90 days in patients given peribulbar anesthesia was 5.8% and in patients given retrobulbar anesthesia 5.5%, and this difference was not statistically significant (P = 0.90). Eighteen percent of patients in both groups reported a change in the appearance of their eyelids. There was a moderate, positive correlation among patients who reported a change in their lid position and objective measurements of ptosis. Preoperative clinical measurements of vertical lid fissure width and levator function, and the appearance of the lid crease or superior sulcus were not predictive for the development of postoperative ptosis at 90 days; the best predictor was the presence of ptosis in the immediate postoperative period.

CONCLUSION

The incidence of postcataract ptosis is the same whether two injection peribulbar or retrobulbar anesthesia is used.

Topical timolol administration reduces the incidence of glaucomatous damage in ocular hypertensive individuals. A randomized, double-masked, long-term clinical trial (1)

OBJECTIVES

A randomized, double-masked, 5-year clinical trial was conducted to determine whether topical timolol therapy was more effective than placebo in delaying or preventing the onset of glaucomatous damage in moderate-risk ocular hypertensive subjects.

METHODS

One eye was chosen randomly to receive timolol therapy twice daily; the fellow eye received placebo (timolol vehicle). The primary end point of the study was reproducible visual field loss detected on three consecutive tests. Automated static threshold visual fields were added to the protocol as the study proceeded, and criteria for reproducible defects for the automated fields were developed. The secondary end point was progressive optic disc cupping confirmed by examination of stereoscopic disc photographs. Intraocular pressure was not used as an end point (i.e., eyes were not withdrawn from the study because they reached a predetermined level of intraocular pressure).

Ocular hypertension treatment study: design issues

This report relates the design and conduct considerations in the planning of a large, multicenter clinical trial on the treatment of ocular hypertension. This trial will begin patient enrollment in January 1994.

The dyschromatopsia of optic neuritis is determined in part by the foveal/perifoveal distribution of visual field damage

Most hypotheses of acquired dyschromatopsia invoke the mechanism of selective damage to specific components of the afferent visual system to explain the predominance of red-green and blue-yellow hue-discrimination defects found in neural and retinal disorders, respectively. However, this pattern of hue-discrimination disturbance in ocular disease may vary. There are frequent exceptions which are inadequately explained by existing hypotheses. In an effort to explain the pattern and pathogenesis of acquired dyschromatopsias better, the authors examined patients with nonproliferative diabetic retinopathy (DR) and late-stage retrobulbar neuritis (RBN) using age-corrected Farnsworth-Munsell 100-hue testing and threshold static perimetry. As expected, most DR eyes showed some degree of relative blue-yellow dyschromatopsia (89%) with few showing a greater weighting towards red-green dyschromatopsia (11%). However, an approximately equal number of RBN eyes had a relative blue-yellow (48%) versus red-green dyschromatopsia (52%). For RBN, the authors found a strong association between the spatial distribution of field defect and the type of relative hue-discrimination disturbance. Eyes with greater field depression at the fovea relative to the perifovea showed a relative preponderance of red-green dyschromatopsia (68%) as opposed to blue-yellow dyschromatopsia (32%), whereas eyes with greater relative perifoveal impairment showed a relative preponderance of blue-yellow dyschromatopsia (100%). This relationship between the relative spatial distribution of visual field damage and the relative hue-discrimination deficit in RBN was statistically significant (P = 0.002). Such an association was not found for DR.(ABSTRACT TRUNCATED AT 250 WORDS)

Steady-state pattern electroretinogram following long term unilateral administration of timolol to ocular hypertensive subjects

To determine whether long-term reduction of intraocular pressure leads to a corresponding preservation of the pattern electroretinogram (PERG), PERGs were studied in 21 patients with ocular hypertension who had received unilateral timolol therapy for a minimum of 6 years. The mean difference in intraocular pressure (IOP) between the placebo-treated and the timolol-treated eyes (over 6 years) was 2.4 mm Hg. Steady-state PERGs (16.0 rps) were obtained simultaneously in both eyes of each patient, with four check sizes (0.25, 0.5, 1.0 and 2.0 degrees). Significant (p less than 0.05) steady-state PERG deficits (i.e., amplitude more than two standard deviations below the mean value of age-matched controls) were observed in 16 eyes of 12 patients (10 placebo-treated and 6 timolol-treated eyes). The mean PERG amplitude did not differ significantly between the placebo-treated and timolol-treated eyes. However, a significant correlation (r = -0.423) in the IOP differences between the placebo-treated and timolol-treated eyes and the corresponding PERG amplitude differences was noted in three of the four test conditions (i.e. 0.25, 0.5, and 1.0 degrees). These results suggest that reducing IOP may preserve ganglion cell function in some patients with ocular hypertension.

Glaucomatous visual field damage. Luminance and color-contrast sensitivities

Using a modified Humphrey perimeter, we evaluated 16 eyes with primary open-angle glaucoma and visual field loss (defects 0.5-3.0 log units in depth), and 14 normal eyes. Each eye was tested twice in random order with conventional luminance-increment static perimetry and with the perimeter modified to produce a high-luminance yellow adapting background and a blue test stimulus. The background was a broad-spectrum light of 500 nm and above (yellow), while the stimulus was a broad-spectrum light of 500 nm and below (blue). Paired comparisons were made between conventional and blue/yellow sensitivities for every point examined (1184 points in 16 diseased eyes and 1036 points in 14 normal eyes). Defect depths were determined by using the age-corrected norms distributed in the Humphrey Statpac software. In glaucomatous eyes, blue/yellow sensitivity showed greater impairment than did conventional perimetric sensitivity, in which defect depths were less than 1.0 log unit. However, for defects greater than 1.0 log unit in depth, conventional perimetric sensitivity and blue/yellow sensitivity showed equivalent degrees of damage. Receiver operating characteristic (ROC) analysis was used to compare the ability of blue/yellow and of conventional perimetry in distinguishing between glaucomatous and normal eyes. Results indicated that although blue/yellow color-contrast perimetry may be more sensitive for the detection of incipient glaucomatous damage, in the manifest stages of visual field damage blue/yellow color-contrast perimetry is no more sensitive than is conventional (luminance-increment) perimetry for defining the extent of glaucomatous visual field defects.

Topical timolol administration reduces the incidence of glaucomatous damage in ocular hypertensive individuals. A randomized, double-masked, long-term clinical trial

We conducted a randomized, double-masked, long-term clinical trial to determine whether topical timolol therapy was effective in delaying or preventing the onset of glaucomatous damage in moderate-risk ocular hypertensive subjects. In 62 patients, one eye was chosen randomly to receive timolol therapy twice daily while the fellow eye received placebo. During the course of the study, the mean +/- SD difference in intraocular pressure between the timolol-treated and the placebo-treated eyes was 2.3 +/- 2.6 mm Hg. Reproducible visual field loss developed in 4 timolol-treated eyes and 10 placebo-treated eyes. Progressive optic disc cupping was noted in 4 timolol-treated and 8 placebo-treated eyes. Using a computerized image analysis system, the mean +/- SD increase in optic disc pallor during the course of the study was 0.86% +/- 2.4% in the timolol-treated eyes as opposed to 1.80% +/- 3.6% in the placebo-treated eyes. This study provides evidence that lowering intraocular pressure by medical treatment reduces the incidence of glaucomatous damage in ocular-hypertensive individuals.

Intraocular pressure response to topical dexamethasone as a predictor for the development of primary open-angle glaucoma

In a retrospective study we reviewed the records of 788 subjects who had been corticosteroid tested with 0.1% dexamethasone four times daily to one eye for six weeks. All subjects had normal kinetic visual fields and optic nerve heads in both eyes at the time of testing and were followed up for a minimum of five years. Some subjects had normal baseline intraocular pressures whereas others were considered to have ocular hypertension. Of 276 individuals who were high corticosteroid responders (intraocular pressure greater than 31 mm Hg during dexamethasone administration), 36 (13.0%) developed glaucomatous visual field loss during the follow-up period. Only nine of 261 individuals (3.4%) who were intermediate responders (intraocular pressure 20 to 31 mm Hg during dexamethasone administration) and none of 251 individuals who were low responders (intraocular pressure less than 20 mm Hg during dexamethasone administration) developed glaucomatous visual field loss. However, the ability of the intraocular pressure response to dexamethasone to predict the development of glaucomatous visual field loss was not as good as the predictive power of a multivariate model that included patient age, race, baseline intraocular pressure, baseline outflow facility, baseline cup/disk ratio, and systemic hypertension.

Retinocortical conduction time in diabetics with abnormal pattern reversal electroretinograms and visual evoked potentials

Clinically evident retinal vascular disease in patients with diabetes mellitus may be preceded by an increase in visual evoked potential latency in electrophysiologic testing. This increase may indicate either retinal or optic nerve dysfunction. To determine the origin of the latency increase we initiated a cross-sectional study of simultaneous pattern-reversal electroretinograms and visual evoked potentials. We recorded transient (3.8 reversals/second) pattern electroretinograms and visual evoked potentials using both 15' and 60' high-contrast black-white checks. Fifty-five diabetic patients (34 with no retinopathy and 21 with background retinopathy) and 34 age-matched visual normals (controls) were tested. Group data in diabetics showed significant latency increases in both tests, but not significant differences in retinocortical conduction time were noted. These results suggest that the increases in visual evoked potential latency exhibited by diabetic patients with little or no retinopathy usually reflect altered retinal function rather than optic neuropathy. Two patients with background retinopathy exhibited retinocortical conduction times that exceeded the normal mean by more than two standard deviations, suggesting that optic neuropathy may occasionally occur in diabetic patients with background retinopathy.

The relationship between hue discrimination and contrast sensitivity deficits in patients with diabetes mellitus

In an attempt to elucidate more fully the pathophysiologic basis of early visual dysfunction in patients with diabetes mellitus, color vision (hue discrimination) and spatial resolution (contrast sensitivity) were tested in diabetic patients with little or no retinopathy (n = 57) and age-matched visual normals (n = 35). Some evidence of visual dysfunction was observed in 37.8% of the diabetics with no retinopathy and 60.0% of the diabetics with background retinopathy. Although significant hue discrimination and contrast sensitivity deficits were observed in both groups of diabetic patients, contrast sensitivity was abnormal more frequently than hue discrimination. However, only 5.4% of the diabetics with no retinopathy and 10.0% of the diabetics with background retinopathy exhibited both abnormal hue discrimination and abnormal contrast sensitivity. Contrary to previous reports, blue-yellow (B-Y) and red-green (R-G) hue discrimination deficits were observed with approximately equal frequency. In the diabetic group, contrast sensitivity was reduced at all spatial frequencies tested, but for individual diabetic patients, significant deficits were only evident for the mid-range spatial frequencies. Among diabetic patients, the hue discrimination deficits, but not the contrast sensitivity abnormalities, were correlated with the patients' hemoglobin A1 level. A negative correlation between contrast sensitivity at 6.0 cpd and the duration of diabetes also was observed.

Perioperative control of blood glucose in diabetic patients: a two-step protocol

Perioperative control of blood glucose in patients with diabetes has been difficult due to frequent occurrence of hypoglycemia or hyperglycemia. We developed a two-step protocol for management of insulin-treated patients during general anesthesia. Regular insulin was given intravenously before anesthetic induction according to the step I formula (initial): initial blood glucose - 150/10 = U. Regular insulin was then given during surgery according to the step II formula (hourly): blood glucose 150-250 mg/dl = 2 U; blood glucose greater than 250 mg/dl = 4 U. Fluid replacement of 5% dextrose with lactated Ringer's solution, 3 ml/kg estimated ideal body weight, was given hourly and additional lactated Ringer's solution was given as indicated. Thirty patients received preoperative (long- or intermediate-acting) insulin and were managed by the two-step protocol. Ten patients received preoperative (long- or intermediate-acting) insulin and were managed by a standard method used in the same institution. Thirty patients did not receive preoperative insulin and were managed by the two-step protocol. All patients underwent retinal surgery under general anesthesia. In comparing the two groups pretreated with insulin, patients treated by the standard method had significantly higher (mean) blood glucose levels (360.2 +/- 100.4 mg/dl) than those treated with the two-step protocol (181.2 +/- 50.8 mg/dl) (P = 0.0001) at the end of surgery. Of the two-step protocol patients, those pretreated with one-half the usual morning dose of long- or intermediate-acting insulin had lower (mean) blood glucose levels (225 +/- 87 mg/dl) than patients not pretreated (310 +/- 130.8 mg/dl) (P = 0.0069) the morning after surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Color perimetry of glaucomatous visual field defects

A color video tangent screen has been devised, using microcomputer control of a video display to produce colored perimetric test objects matched in luminance to a white surround at 10-foot lamberts . Perimetric isopters for varying degrees of color saturation were determined by kinetic perimetry. This form of color perimetry was used to examine one eye of each of 40 patients with open-angle glaucoma as well as 20 glaucoma-suspect patients. For the first 23 eyes with manifest glaucomatous visual field defects, a masked comparison was made between the results of color perimetry and conventional perimetry with a Goldmann perimeter. For these 23 eyes, color perimetry did as well as luminance perimetry in 14, was less sensitive in 2, and was more sensitive in 7. All defects that were detectable by conventional perimetry were successfully demonstrated by the color method. Such defects often appeared to be greater in extent when mapped by the color method as compared to conventional luminance perimetry.

Calibration of the Dicon Auto Perimeter 2000 compared with that of the Goldmann perimeter

We empirically evaluated the calibration of the Dicon Auto Perimeter 2000 by comparing the results of threshold static perimetry with those for the same group of normal subjects examined by conventional manual static perimetry with the Goldmann perimeter. At 10 to 20 degrees of eccentricity in the visual field (including the entire Bjerrum region), there was no significant difference between threshold levels expressed as Goldmann equivalent stimuli by the Dicon instrument and the results obtained by examination with the Goldmann perimeter. The slopes of the linear meridional profiles from the two instruments were significantly different, however. The slope of the profile measured with the Dicon perimeter was flatter than that produced by Goldmann perimetry, so that threshold values inside 10 degrees of eccentricity were higher, whereas threshold values outside of 20 degrees of eccentricity were lower. Though statistically significant, these differences were small (2 dB at most). The difference in slopes can be attributed to a difference in stimulus sizes, because the area of the Dicon stimulus is eight times that of the size I Goldmann test object and twice that of the size II test object.