Biomedical subjects

H A Quigley

Publications and source records attributed to H A Quigley.

At least 19 recordsLinked to original sources

PubMed1997

Estimating progression of visual field loss in glaucoma.

PURPOSE: The authors estimated the prevalence and rates of progressive visual field loss in glaucoma patients followed annually for a median of 6.3 years. METHODS: Linear regression was used to estimate rates of progression of mean deviation, corrected pattern standard deviation (CPSD), clusters of locations based on the Glaucoma Hemifield Test (GHT), and location specific changes in C-30-2 fields of the Humphrey Analyzer. RESULTS: Sixty-seven eyes of 56 patients whose first two consecutive fields were abnormal on GHT were included. Almost all patients were under treatment or had undergone surgery for glaucoma. Visual field deteriorated in 19 (28%) eyes based on worsening of one or more CPSD, GHT clusters, or individual test locations (regression slopes significantly different from zero). Corrected pattern standard deviation deteriorated in 5 eyes, at least one GHT cluster deteriorated in 17 eyes, and one or more individual test locations deteriorated in 15 eyes. For those whose visual field deteriorated, CPSD increased by 0.9 dB/year. Glaucoma Hemifield Test clusters declined by between 1.4 and 2.4 dB/year. Deterioration at individual locations ranged from 1.0 to 5.0 dB/year. Age, but not baseline visual field severity, was predictive of further visual field loss. The odds ratio for the association between progressive visual field loss and thinning of the nerve fiber layer was 1.81 (95% confidence interval: 0.52, 6.33), and 3.78 (95% confidence interval: 0.80, 18.16) for the association between progressive visual field loss and optic disc changes during follow-up based on masked photograph readings. CONCLUSIONS: Less than one in three eyes of patients with glaucoma had any progressive field loss. Average changes in threshold sensitivities of less than 1 dB/year could not be detected with seven fields done over 6 years. Larger changes or increased frequency of visual field testing would need to occur before smaller changes could be detected statistically.

Disease Progression↗

PubMed1997

Models of open-angle glaucoma prevalence and incidence in the United States.

PURPOSE: To estimate the prevalence and incidence of open-angle glaucoma among black and white persons in the United States and to characterize quantitatively their life experience with glaucoma using a life table approach to estimate disease duration. METHODS: Review of published data on glaucoma combined with statistical models to estimate prevalence and incidence. RESULTS: The association of open-angle glaucoma with age was examined separately for white and black persons. By the year 2000, the number of persons in the United States with primary open-angle glaucoma is estimated to be 2.47 million (1.84 million white and 619,000 black Americans). A model using derived incidence rates for open-angle glaucoma (OAG) and United States mortality data indicated that the average black American has OAG 27% longer than the average white American (16.3 years compared to 12.8 years). CONCLUSIONS: Meta-analysis to obtain pooled prevalence estimates for glaucoma provides useful information on length of disease and age distribution of those affected. It may assist in estimating treatment effects and associated costs to derive data that effect health care decisions.

Adult↗

PubMed1996

Rate of progression in open-angle glaucoma estimated from cross-sectional prevalence of visual field damage.

PURPOSE: To estimate the rate of visual field loss in persons with open-angle glaucoma. METHODS: The visual field data obtained by Goldmann perimetry from 151 persons with open-angle glaucoma from the Baltimore Eye Survey were graded on a nine-level severity scale. Approximately one half of these persons had previously diagnosed glaucoma and were being treated. Using regression analysis, their scores were compared to other features, including age, vertical cup/disk ratio, treatment status, gender, race, and intraocular pressure. These data were used to estimate the average rate of progressive field loss and blindness in glaucoma. RESULTS: Among 112 black subjects, the severity of visual field damage was significantly associated with age (P < .02), history of glaucoma treatment (P < .04), and intraocular pressure (P < .0001). Using the relationship between age and damage, we estimated that the rate of deterioration of black glaucoma subjects was two grading levels per decade, which is consistent with previous reports. For 39 white subjects, the inclusion of age improved the model relationship between damage score and other variables. The best estimate of individual damage rate for whites was similar to that in blacks. However, the statistical association of age and damage in whites was less strong than in blacks, possibly because of fewer white subjects in the sample. CONCLUSIONS: While glaucoma is a frequent cause of visual disability, rate of progressive visual field loss is not sufficient to lead to bilateral blindness in the majority of those affected. Aggressiveness of glaucoma therapy should be related to the rate of visual field loss stressing confirmation of field progression.

Adult↗

PubMed1996

Quantitative studies of elastin in the optic nerve heads of persons with primary open-angle glaucoma.

PURPOSE: To compare quantitative and qualitative differences in elastin content in the optic nerve heads of glaucomatous and control human eyes. METHODS: Transmission electron microscopy and quantitative histomorphometry on ten control and ten glaucomatous eyes. RESULTS: Elastin fiber complexes in the control lamina cribrosa were smaller and more numerous than in the insertion zone of the sclera immediately surrounding the lamina. Although the density of elastin fibers in the normal lamina was twice that of the insertion zone (P = 0.004), the percent area of the connective tissue matrix occupied by elastin was the same for both zones (P > 0.4). There was no difference between control and glaucomatous eyes in the quantified parameters of elastin content or in the ultrastructure of elastin between control and glaucomatous eyes. CONCLUSIONS: The authors demonstrated for the first time that elastin in the normal lamina consists of fibers of smaller diameter than in the adjacent sclera, although the total amount of elastin is similar in both locations. This may provide maximum viscoelasticity within the limited connective tissue beam area of the lamina. Despite using a large number of specimens, the authors again found no differences between normal and glaucomatous eyes in the number or ultrastructural appearance of elastin fibers.

Aged↗

PubMed1996

Detection of incident field loss using the glaucoma hemifield test.

PURPOSE: To examine different definitions of incident visual field loss among patients with elevated intraocular pressure and varying numbers of abnormal glaucoma hemifield test results over an average of 6 years of follow-up. METHODS: A cohort of patients with annual C-30-2 Humphrey visual fields were followed for a minimum of 5 years. Three different definitions of field loss were compared: 1, 2, or 3 consecutive annual abnormal glaucoma hemifield test results. RESULTS: Of 253 subjects, 506 eyes were followed for 5 to 9 years. If incident field loss was defined as one or more normal fields followed by one abnormal glaucoma hemifield test result, the incidence of field loss was 63.6 per 1000 person-years of follow-up. For two or three consecutive abnormal glaucoma hemifield test results, the rates were 27.6 and 19.2 per 1000 person-years of follow-up, respectively. Among patients with field loss in one eye at the start of the study, the incidence of field loss in the fellow eye using 1, 2, or 3 consecutive abnormal fields as the definition of incident field loss was 60.9, 55.5, and 25.5 per 1000 person-years of follow-up, respectively. Three years after incident field loss, 31.9% (1 abnormal test result), 76.5% (2 abnormal test results), and 88.5% (3 abnormal test results) of eyes with incident field loss had an abnormal hemifield test result. For eyes with one, two, and three consecutive abnormal glaucoma hemifield test results at the start of the study, 59.2%, 83.6%, and 89.1%, respectively, had an abnormal field 3 years later. CONCLUSIONS: One abnormal glaucoma hemifield test result is not a consistent criterion for defining incident field loss. The use of two or three consecutive abnormal fields to define incident field loss makes it more likely that subsequent test results will be abnormal.

Adult↗

PubMed1996

Screening techniques for angle-closure glaucoma in rural Taiwan.

562 residents of Jin Shan aged 40 years and above underwent examinations to compare the sensitivity and specificity of oblique flashlight, peripheral slit beam and ultrasonographic evaluation of the anterior chamber depth to gonioscopy in detecting cases of PACG. Among 5441 eligible individuals aged 40 and above, 562 (10.3%) underwent screening for PACG, of whom 17 (3.02%) were defined as cases, and 10 (1.78%) as suspects. Home visits indicated that respondents for screening were similar to the population as a whole. Only 35% of PACG cases reported symptoms consistent with acute angle closure, and only 18% were previously diagnosed. When compared to gonioscopy, only ultrasonographic measurement of AC depth provided an adequate mix of sensitivity and specificity. Ultrasonography in combination with tonometry provided a sensitivity of 88% with a specificity of 92%. Sensitivity and specificity for ultrasonography in combination with refractive status were 84% and 83% respectively. Shallower AC depth (p = 0.0001), shorter axial globe length (p = 0.001), greater than 2D of hyperopia (p < 0.001), high grades of nuclear sclerotic cataract (p < 0.0001) and an increased cup-to-disc ratio (p = 0.002) were significantly correlated with a diagnosis of PACG.

Adult↗

PubMed1996

Number of people with glaucoma worldwide.

AIM: To estimate the prevalence of glaucoma among people worldwide. METHODS: Available published data on glaucoma prevalence were reviewed to determine the relation of open angle and angle closure glaucoma with age in people of European, African, and Asian origin. A comparison was made with estimated world population data for the year 2000. RESULTS: The number of people with primary glaucoma in the world by the year 2000 is estimated at nearly 66.8 million, with 6.7 million suffering from bilateral blindness. In developed countries, fewer than 50% of those with glaucoma are aware of their disease. In the developing world, the rate of known disease is even lower. CONCLUSIONS: Glaucoma is the second leading cause of vision loss in the world. Improved methods of screening and therapy for glaucoma are urgently needed.

Adult↗

PubMed1996

Analysis of progressive change in automated visual fields in glaucoma.

PURPOSE: To detect and estimate the rate of progression of visual field loss in subjects with glaucoma who undergo long-term automated perimetric visual field testing. METHODS: Automated visual field data were obtained for subjects with glaucomatous visual field loss and a minimum of seven threshold field tests over at least 4.5 years. Univariate linear regression was performed with respect to mean deviation (MD), corrected pattern standard deviation (CPSD), mean thresholds of clusters corresponding to the Glaucoma Hemifield Test (GHT), and thresholds of 52 individual test locations. Subjects were classified as progressive or stable (unchanged or improved) based on the slope and statistical significance of these parameters. Adjusted P values were used to maintain the overall type 1 error at 5%. RESULTS: One hundred ninety-one subjects with a mean follow-up period of 7.1 years (range, 4.5 to 10.5 years) and a mean number of visual field tests of 9.5 (range, 7 to 16) were included. Twenty-four subjects (12.6%) showed progression in MD (mean slope [95% confidence interval], -1.26 [-1.50, -1.01] dB/year), and 27 (14.1%) showed progression in CPSD (mean slope [95% confidence interval], 0.71 [0.58, 0.84] dB/year). Thirty-five subjects (18.3%) had > or = 1 progressive GHT cluster. The mean slope in progressive clusters ranged from -1.51 [-1.82, -1.20] to -2.84 [-3.39, -2.29] dB/year. Thirty-six subjects (18.8%) had > or = 1 progressive individual test locations. Fifty-two subjects (27.2%) were classified as progressive based on progression of CPSD, > or = 1 cluster and/or > or = 1 point. CONCLUSIONS: Fewer than 1 in 3 subjects progressed by any one of the criteria for progression over an average of 7.1 years. Rates of progression that could be statistically confirmed were in the range of approximately 1 to 5 dB/year, depending on the number of fields, the variability over time, and the parameter assessed (global indices, GHT clusters, or individual points). No correlation between initial visual field status and the rate of progression was found. A minimum of approximately 5 years of follow-up with annual perimetry would be required to detect significant changes in the visual field by linear regression.

Adolescent↗

PubMed1996

Study of central retinal ganglion cell loss in experimental glaucoma in monkey eyes.

PURPOSE: The objective of this research was to compare the loss of retinal ganglion cells subserving the fovea to that of the ganglion cells in the surrounding perifoveal region in eyes with experimental glaucoma. METHODS: Ganglion cell nucleoli were counted using light microscopy from vertically oriented retinal, strips and the cell density was calculated using the modified Abercombie formula. Percent ganglion cell loss in glaucomatous eyes from five monkeys was determined for each of up to five contiguous areas within the central 12 degrees of the retina by comparison to normal fellow eyes. RESULTS: Loss of central ganglion cells was present even in eyes with mild glaucomatous damage. The percent ganglion cell loss in glaucomatous eyes at five adjacent areas within the central 12 degrees of the retina did not differ significantly (ANOVA, p = 0.77, n = 8). Cell loss in areas nearest to the fovea was indistinguishable from that in more peripheral perifoveal areas. CONCLUSIONS: Foveal ganglion cells appear to be susceptible to experimental glaucoma injury. Psychophysical testing of foveal functions may deserve renewed attention in glaucoma diagnosis and follow-up.

Analysis of Variance↗

PubMed1996

Change in the optic disc and nerve fiber layer estimated with the glaucoma-scope in monkey eyes.

PURPOSE: The purpose of this research was to measure quantitatively changes in the position of the optic disc and nerve fiber layer during acute and chronic experimental conditions simulating glaucoma in monkey eyes. METHODS: The positions of the surface of the optic disc and peripapillary nerve fiber layer were imaged in cynomolgus monkey eyes with the Glaucoma-Scope. Acute intraocular pressure changes was produced by anterior chamber cannulation. Chronic change was induced by trabecular laser scarring leading to chronic experimental glaucoma and by orbital transection of the optic nerve. RESULTS: Mean backward movements of the disc surface of 50-60 microns were detected when intraocular pressure was elevated to 45 mm Hg for 45 min. The disc position reverted in viscoelastic fashion toward its original location on normalization of pressure. Loss of nerve fibers induced by elevated intraocular pressure was more closely related to change in the mean position of the disc (MPD) than to change in cup/disc ratio. Chronic glaucoma led to much deeper excavation of the disc than experimental optic atrophy, but peripapillary atrophy was similar in the two conditions with the index, nerve fiber layer area, whose values correlate well with the number of nerve fibers in an eye that is estimated histologically (r2 = 0.75, p = 0.003, n = 9). CONCLUSION: The optic disc behaves in visco-elastic manner with change in intraocular pressure Composite data indices that represent the mean surface topography of the disc and peripapillary region can be used to estimate the degree of glaucoma damage.

Acute Disease↗

PubMed1996

Determination of the real size of fundus objects from fundus photographs.

PURPOSE: The purpose of this research was to study the accuracy of measurements that rely on Littmann curves to determine the real size of fundus images. METHODS: Retinal tacks of known dimensions were placed near the optic disc in one eye of each of two cynomolgus monkeys. Images of the retinal tack and optic nerve head of these two eyes were then obtained with a Zeiss Fundus camera. The dimensions of the retinal tacks and optic discs were measured directly on the film from the Zeiss fundus camera. These measurements were then corrected with Littmann's mathematical approximations. RESULTS: In the cynomolgus eye with 19.9 mm axial length, Littmann's mathematical approximations of the real sizes of the retinal tack and optic disc from measurements on the Zeiss film had median percent bias [(calculated size-real size)/real size] of -0.2% (range, -3.2% to 3.9%). In the other eye with 17.9 mm axial length, the median percent bias was 14.7% (range, 5.1% to 29.7%). CONCLUSION: The estimation of the real size of fundus images with Littmann's mathematical approximations from images on Zeiss film have < 4% bias if the eye's dimensions fall in the range over which Littmann's curves were produced.

Animals↗

PubMed1995

Hypertension, perfusion pressure, and primary open-angle glaucoma. A population-based assessment.

OBJECTIVE: To evaluate the association of vascular factors with primary open-angle glaucoma (POAG). DESIGN: A population-based prevalence survey of ocular disease among black and white residents. SETTING: Communities of east Baltimore, Md. PARTICIPANTS: A stratified cluster sample of 5308 residents 40 years of age or older. MAIN OUTCOME MEASURES: Primary open-angle glaucoma as defined by demonstrable glaucomatous optic nerve damage based on visual fields and/or optic disc findings. Intraocular pressure level was not a criterion for diagnosis. RESULTS: Systolic and diastolic blood pressure showed modest, positive association with POAG. The effect of blood pressure on POAG was modified by age, with a stronger association among older subjects. Lower perfusion pressure (blood pressure-intraocular pressure) was strongly associated with an increased prevalence of POAG, with a sixfold excess for those in the lowest category of perfusion pressure. CONCLUSION: These results suggest that POAG is associated with an alteration in factors related to ocular blood flow and a breakdown of autoregulation.

Adult↗

PubMed1995

Neural rim area declines with increased intraocular pressure in urban Americans.

OBJECTIVE: To determine intraocular pressure (IOP)-related differences in the neural rim area among urban Americans without known optic nerve disease. DESIGN: Population-based prevalence study conducted in 16 cluster areas in East Baltimore, Md. PARTICIPANTS: A population-based sample of 1521 black and 1851 white individuals aged 40 years and older without evidence of optic nerve disease. MAIN OUTCOME MEASURE: Intraocular pressure-related differences in neural rim area, neural rim area-to-disc area ratio, and cup-to-disc ratio. RESULTS: We analyzed optic disc photographs using the Imagenet system (Topcon Instrument Corp of America, Paramus, NJ). After adjusting for age and disc area, white Americans had a 6% decrease in neural rim area for every 10-mm Hg increase in IOP (P = .0001). In black Americans, there was a quadratic relationship between neural rim area and IOP, with little decline with IOP up to approximately 17 mm Hg, after which neural rim area declined significantly with higher IOP (P = .001). Similarly, the neural rim area-to-disc area ratio decreased and the vertical cup-to-disc ratio increased with increasing IOP in both black and white Americans. CONCLUSIONS: The higher the level of IOP, the smaller was the amount of neural rim tissue in the optic disc for both black and white Americans. However, the relationship between IOP and neural rim area was different in whites and blacks.

Adult↗

PubMed1995

Impact of age, various forms of cataract, and visual acuity on whole-field scotopic sensitivity screening for glaucoma in rural Taiwan.

OBJECTIVE: To evaluate the impact of age, various forms of cataract, and visual acuity on whole-field scotopic sensitivity screening for glaucoma in a rural population. DESIGN: Clinic-based study with population-based recruitment. SETTING: Jin Shan Township near Taipei, Taiwan. SUBJECTS: Three hundred forty-six residents (ages, > or = 40 years) of Jin Shan Township. INTERVENTIONS: Whole-field scotopic testing, ophthalmoscopy with dilation of the pupils, cataract grading against photographic standards, and screening visual field testing in a random one-third subsample. MAIN OUTCOME MEASURES: Whole-field scotopic sensitivity (in decibels) and diagnostic status as a case of glaucoma, glaucoma suspect, or normal. RESULTS: Participants in Jin Shan Township did not differ significantly in the rate of blindness, low visual acuity, or family history of glaucoma from a random sample of nonrespondents. Scotopic sensitivity testing detected 100% (6/6) of subjects with open-angle glaucoma at a specificity of 80.2%. The mean +/- SE scotopic sensitivity for six subjects with open-angle glaucoma (32.78 +/- 1.51 dB) differed significantly from that of 315 normal individuals (38.51 +/- 0.22 dB), when adjusted for age and visual acuity (P = .05, t test). With linear regression modeling, factors that correlated significantly with scotopic sensitivity were intraocular pressure, screening visual field, best corrected visual acuity, presence of cortical cataract, and increasing age. CONCLUSIONS: Although cataract affects the whole-field scotopic threshold, it appears that scotopic testing may be of value in field-based screening for glaucoma.

Adult↗

PubMed1995

Comparison of clinician judgment with digitized image analysis in the detection of induced optic disk change in monkey eyes.

PURPOSE: To compare the ability of clinicians to detect change in the photographic appearance of the optic disk with the performance of a system for digitized image analysis. METHODS: In 11 monkey eyes, a Topcon Imagenet System was used to acquire eight digitized image pairs and four stereoscopic photographs at an intraocular pressure of 10 mm Hg, and then, again, 45 minutes after intraocular pressure was increased to 45 mm Hg. We recently reported detection of global (ten of 11 eyes) and regional (11 of 11 eyes) change in the digitized images of these eyes by using two new statistical strategies for optic disk analysis. For the current study, we evaluated the ability of three clinicians (the authors) to detect a change within the stereoscopic photographs of these 11 optic disks. For each eye, the eight stereoscopic photographs (four at intraocular pressure of 10 mm Hg and four at intraocular pressure of 45 mm Hg) were developed as stereoscopic slides and arranged into four pairs (10/10, 45/45, 10/45, and 45/10 mm Hg). Thus, two pairs represented no change in intraocular pressure (10/10 and 45/45 mm Hg) and the other two pairs represented either an increase or a decrease in intraocular pressure (10/45 and 45/10 mm Hg). The 44 pairs of stereoscopic slides (four pairs for each of 11 eyes) were masked then randomly mixed. On two separate occasions, each clinician evaluated each pair of stereoscopic slides for the presence of absence of optic disk change. RESULTS: Reproducibility between the two readings of each clinician ranged from .50 to .64 (kappa statistic). Clinicians correctly detected change (as detected by image analysis) within 45% to 64% of the 10/45 and 45/10 pairs of stereoscopic slides. Clinicians correctly indentified no change within 86% to 100% of the 10/10- and 45/45-mm Hg pairs of stereoscopic slides. Clinicians correctly identified no change significantly more often than change (P < .01, chi 2 test). Change was not detected consistently by all three clinicians in any of the 11 eyes. CONCLUSION: In a controlled experimental setting, digitized image acquisition with extensive secondary statistical analysis more sensitively detected small short-term changes in the surface of the optic disks of monkeys than did three masked clinicians.

Animals↗

PubMed1995

Comparison of ganglion cell loss and cone loss in experimental glaucoma.

PURPOSE: To compare the loss of ganglion cells to cone loss in the macular area of monkey eyes with experimental glaucoma. METHODS: Experimental glaucoma was induced in eyes of three cynomolgus monkeys by argon laser applications to the trabecular meshwork. The average duration +/- S.D. of glaucoma in the experimental animals was 3.8 +/- 0.5 months. Glaucomatous damage was estimated, before the animals were killed, by evaluating stereoscopic photographs of the optic disk and red-free photographs of the nerve fiber layer. Ganglion cell nucleoli and cone pedicles were counted by using light microscopy from slides containing strips of retinal tissue. Cell density was then calculated by using the modified Abercrombie formula. Percent loss of ganglion cells and cones was determined from three eyes of three monkeys in 300-micron segments that were 900 to 1,200 microns superior and inferior to the foveal center. RESULTS: Cone loss was not found at 4.5 to 6 degrees eccentricity above and below the fovea, whether damage was mild or severe. The average loss +/- S.D. of ganglion cells was 81.1% +/- 10.7%, whereas the average cone loss was only 3.5% +/- 6.4%. CONCLUSIONS: Marked parafoveal cone loss was not found in experimental glaucoma in which extensive damage to ganglion cells occurred.

Animals↗

PubMed1995

Incidence of acute angle-closure glaucoma after pharmacologic mydriasis.

PURPOSE: To study the incidence of acute angle-closure glaucoma secondary to pupillary dilation and to identify screening methods for detecting angles at risk of occlusion. METHODS: We studied 5,308 respondents to the Baltimore Eye Survey, a cross-sectional, population-based survey conducted in a multiracial urban community. We measured incidence of acute angle-closure glaucoma after pharmacologic mydriasis and the specificity and sensitivity associated with three screening criteria in identifying those with potentially occludable angles. The screening factors were presence of shallow anterior chamber on penlight examination, history of glaucoma, and blindness. RESULTS: Of the 4,870 subjects whose eyes were dilated on screening examination, none developed acute angle-closure glaucoma. However, 38 patients of the 1,770 who were referred for definitive eye examination were judged to have occludable angles on the basis of gonioscopic methods. Of note, subjects aged 70 years and more were three times more likely to have occludable angles than those aged 40 to 69 years (P < .004) In 14 black subjects with occludable angles, six were detected by history of glaucoma and not by shallow anterior chamber configuration; alternatively, in 24 white subjects, 11 (46%) were detected on the basis of shallow anterior chambers (Fisher's exact test, P = .014). When the three screening factors were considered alone and in combination, the most effective combination for predicting a potentially occludable angle was to use shallow anterior chamber on penlight examination and history of glaucoma. These criteria provide 60.5% sensitivity and 93.3% specificity. CONCLUSION: If screening is performed accurately and the results are negative, the risk of dilating a potentially occludable angle was less than one in 333 subjects (negative predictive value, 0.997) in this population.

Acute Disease↗

PubMed1995

Early changes in optic disc compliance and surface position in experimental glaucoma.

PURPOSE: To detect changes in the compliance and baseline position (position at the baseline time point of a compliance test) of the monkey optic disc after the onset of chronic experimental glaucoma. METHODS: Sixty-six compliance tests were performed on 26 eyes of 13 monkeys. Longitudinal Study. In seven normal monkeys, compliance tests were performed three times in one eye (study eye) and once in the contralateral eye. In the study eye of five of these monkeys, chronic experimental glaucoma was then induced and compliance tests were performed at some or all of the following postglaucoma testing intervals: 1 to 2 weeks, 3 to 4 weeks, 5 to 8 weeks, 9 to 12 weeks, 13 to 18 weeks, and more than 18 weeks after the onset of elevated intraocular pressure (IOP). In the study eye of the remaining two monkeys, the optic nerve was transected, and compliance was tested at 5, 9, and 13 weeks after transection. An analysis of variance (ANOVA) was performed to detect an increase (hypercompliance) or decrease (rigidity) in the compliance of the glaucomatous eyes at each testing interval. A second ANOVA was performed to detect the onset of chronic posterior deformation of the baseline position of each disc. Cross-Sectional Study. In six additional monkeys with pre-existing experimental glaucoma, the glaucomatous study eye was compliance tested at one of the postglaucoma testing intervals used in the longitudinal study. The contralateral normal eye was compliance tested once. These data were then added to the data from the five longitudinally studied monkeys at the appropriate preglaucoma and postglaucoma testing intervals. A third ANOVA was done to compare the compliance of the expanded group of glaucomatous eyes at each postintervention testing interval with the compliance of the 13 normal contralateral eyes. RESULTS: Compliance. In the longitudinally (Pr > F = 0.0005) and cross-sectionally (Pr > F = 0.0001) studied glaucomatous eyes, optic disc compliance increased significantly by 1 to 2 weeks and then returned to a level statistically indistinguishable from normal within 13 to 18 weeks after the onset of glaucoma. In the transection eyes, the optic discs were significantly less compliant (more rigid) at 5 and 9 weeks after transection compared with the discs in either the normal or the glaucomatous eyes (Pr > F < 0.05). Baseline Optic Disc Position. Chronic posterior deformation of the disc was detected in one of three eyes tested 1 to 2 weeks and three of four eyes tested 3 to 4 weeks after the onset of glaucoma (Pr > F < 0.05). Chronic posterior deformation was not detected in the discs of either of the transection eyes at any of the post-transection testing intervals. CONCLUSION: Changes in optic disc compliance and surface position were detected by digitized image analysis within 2 to 4 weeks of the onset of experimental glaucoma in the monkey eye. These findings are unlikely to be due to axon loss alone, because they did not occur in optic nerve transection eyes (which constitute a model of axon loss in which intraocular pressures remain normal). The results suggest that IOP-related damage to the load-bearing connective tissues of the optic nerve head may occur early in the course of experimental glaucoma.

Analysis of Variance↗