Hurshell H. Hunt

Factors Associated With Visual Loss in Patients With Advanced Glaucomatous Changes in the Optic Nerve Head

We evaluated factors associated with decreased or stable visual function in 72 patients with primary open-angle glaucoma and complete cupping of the optic disk who were followed up five years or more. We found a significantly lower mean (15.4 +/- 2.7 mm Hg) and peak (24.5 +/- 6.9 mm Hg) intraocular pressure in those patients whose vision remained stable vs those whose vision decreased (21.3 +/- 3.2 and 39.2 +/- 11.0 mm Hg, respectively) (t-test, P < .001). Additionally, the variance of each patients individual intraocular pressure readings measured during the follow-up period was lower in the group with stable vision (4.5 mm Hg) than in those in whom vision decreased (9.0 mm Hg) (F test, P < .001). Stepwise discriminant analysis disclosed that mean intraocular pressure, variance of an individuals intraocular pressure measurements over time, history of argon laser trabeculoplasty, and compliance with therapy discriminated 92.9% of patients (52 of 56) whose vision remained stable and 87.5% of patients (14 of 16) whose vision decreased. Reduction of intraocular pressure and compliance with therapy are important in patients with complete glaucomatous cupping of the optic disk.

Threshold variability using different Goldmann stimulus sizes

Abstract. We tested 10 healthy subjects on the Humphrey Field Analyzer using Goldmann stimulus sizes I‐V to determine the effect of varying the area of the stimulus upon threshold fluctuation. Our results show similar components of fluctuation for the size III stimulus as in past studies. However, an increased total fluctuation was observed for Goldmann stimulus sizes I (3.69 decibels) and II (3.17 decibels) and a similar fluctuation for stimulus sizes IV (2.64 decibels) and V (2.51 decibels) as compared to stimulus size III (2.52 decibels). The study suggests no advantage results in reduced threshold fluctuation by changing the Goldmann stimulus from a size III when testing normal individuals on the Humphrey Field Analyzer.

Static threshold variability in the peripheral visual field in normal subjects.

We assessed the variability of point-wise static threshold values and the components of fluctuation outside the central 30° field in 20 normal individuals tested on the Humphrey field analyzer. We found a mean short-term fluctuation of 2.37 dB, a long-term heterogeneous fluctuation of 5.28 dB, and a long-term homogeneous fluctuation of 1.10 dB. All components of fluctuation were greatest superiorly. Point-wise variation was highest superiorly and nasally and increased with greater eccentricity from fixation in all but the temporal quadrant. Also, point-wise variation was greater between individual than between tests in a single individual. This study suggests that outside the central 30° field, changes in individual threshold measurements in the superior and nasal quadrants should be greater than those in the temporal or inferior quadrants before they can be distinguished from normal variation.

Threshold variation in automated perimetry.

A physiologic fluctuation in threshold levels exists in automated perimetry, which is greater in glaucoma and ocular hypertensive patients than in normal subjects. Fluctuation increases with greater eccentricity from fixation and in areas of reduced retinal sensitivity. Other factors related to automated perimetry testing potentially may influence threshold fluctuation including: a learning effect, reliability, pupil size, age, and the mode of stimulus presentation. Statistical software may aid in analyzing both the single field and the changes between successive fields. However, statistical programs cannot replace physician judgment, and all factors that may influence threshold levels should be considered when interpreting automated visual fields.

The correlation coefficient between the smallest and largest observations when (N-1) of the n observations are iid exponentially distributed

A random sample of size n is obtained from two exponential populations in the following manner: (n-1) observations are selected from one of these populations and a single observation is selected from the other population. The correlation coefficient for Y1and Yn, the first and n-th order statistics is obtained. More ngenerally, it is shown in the course of the derivation that Yj-Yi is independent of YK-Y1 for all i, j, l and k such that I < j < l < k. This result is weil known when all the observations are iid exponentially distributed.

Intraoperative Intracameral Carbachol in Phacoemulsification and Posterior Chamber Lens Implantation

PURPOSE To evaluate the use of intraoperative intracameral carbachol in association with phacoemulsification and posterior lens implantation. METHODS We prospectively randomly assigned 41 eyes (41 patients) to receive either placebo or a 50:50 dilution of carbachol 0.01% after intraocular lens insertion and phacoemulsification. RESULTS Twenty-one eyes of 21 patients treated with intracameral carbachol showed a statistically significant (P = .0373) reduction in intraocular pressure (15.9 mm Hg) at 6 hours postoperatively compared with 20 eyes of 20 patients who had received placebo (20.4 mm Hg). At day 1, the carbachol group measured 15.0 mm Hg vs 17.6 mm Hg for placebo (P = .0376), and a 1.5-line improvement in visual acuity in the carbachol vs the placebo group was noted (P = .0263), which was maintained on glare testing. On quality of life testing using a modified SF-36 test, carbachol-treated patients within the first postoperative week more often attempted to descent stairs in both bright (P = .007) and dim (P = .037) light than did patients treated with placebo. At month 2, no difference was observed between groups except that depth of focus was statistically greater in the carbachol group (P = .025). Safety was similar between the two groups in terms of ocular and systemic adverse events. CONCLUSIONS Patients treated with carbachol intracamerally after phacoemulsification and posterior chamber lens implantation demonstrate lower intraocular pressure within the first day postoperatively. These findings are associated with improved visual acuity and potentially greater ambulation in bright light within the first postoperative week.

Association of reliability with reproducibility of the glaucomatous visual field

Abstract We studied 207 glaucoma patients (207 eyes) who had two successive visual tests on the Humphrey Field Analyzer to determine the association of unreliability (> 10% incidence of a missed catch trial test) with threshold variation. We found that in patients where one visual field showed > 30% false negative or positive errors, and the other visual field also was unreliable, a significant increase in the variance of the mean defect existed from reliable patients (p < 0.05). Of patients who had only one of two visual fields which was unreliable (from false negative errors), only those with marked glaucomatous visual field loss (< ‐15 dB depth of defect) showed a greater variance in mean defect between examinations over reliable patients (p < 0.05). In total, 41 patients (19.8%) had unreliable visual fields associated with statistically increased threshold variation. This study suggests that patient reliability should be considered when interpreting changes in threshold between automated visual field examinations.

Histologic differences in the conjunctiva of black and white glaucoma patients.

We compared perioperative conjunctival biopsy specimens from 31 consecutive trabeculectomy patients to determine if there were any histologic differences between black and white glaucoma patients. We found a statistically significantly greater mean and distribution of mast cells and neutrophils in the white patients. No significant difference was found in the mean number of goblet cells, eosinophiles, macrophages, fibroblasts, plasma cells, or lymphocytes; or in thickness of the epithelium, vascular density, or collagen or mucopolysaccharide staining. We conclude that histological conjunctival factors that could be evaluated preoperatively probably are not related to the poor results in black patients of filtration surgery noted by some investigators.

Long-term and Short-term Fluctuation in Pattern Discrimination Perimetry

We studied threshold fluctuation with the pattern discrimination perimeter in 24 healthy subjects at 56 locations within the central 30 degrees. This perimeter evaluates a subjects ability to discriminate a patterned stimulus measured by a percentage scale. We found an intraindividual fluctuation of 10.52% and an interindividual fluctuation of 8.78%. A statistically increased intraindividual, but not interindividual fluctuation was noted with increasing eccentricity from fixation (P less than .05, Bartletts test). However, no correlation in fluctuation was noted with advancing age or increasing false-positive errors (P greater than .05, correlation coefficient). Also, no difference in fluctuation between superior or inferior hemifields was observed (P greater than .05, Students t-test). The average threshold across all subjects was 54.3%, which provided an upper limit of normal, two standard deviations from the mean, of less than 80% for most locations. This study indicates that fluctuation should be considered when interpreting pattern discrimination fields, but that the extent of fluctuation generally allows for an adequate separation between normal and abnormal measurements.

The effect of stimulus duration upon the components of fluctuation in static automated perimetry.

We studied the effect of varying the stimulus duration time on the components of fluctuation in static automated perimetry by testing 20 healthy subjects on the Humphrey Field Analyser within the central 20° of vision. We found the total fluctuation at a stimulus duration of 0.065 s, to be 3.22 decibels (dB); 0.1 s, 3.22 dB; 0.2 s, 3.34 dB;0.3 s,2.95 dB;0.4 s,3.24 dB; and 0.5 s,3.22 dB. Little difference was observed in the individual components (short-term, long-term homogeneous, long-term heterogeneous and inter-individual) or total fluctuation with an increasing stimulus presentation time when evaluated over the entire visual field or in a pointwise fashion. This study suggests that the stimulus duration within the range of times studied has little effect on the components or total fluctuation in healthy individuals.