Faculty Bibliography

OBJECTIVE:The purpose of the study was to evaluate the effect of optic nerve head drusen (ONHD) on nerve fiber layer (NFL) thickness by visual field testing, red-free photography of NFL, and optical coherence tomography (OCT). DESIGN/METHODS:The study design was a prospective clinical study. PARTICIPANTS/METHODS:Twenty-three eyes of 15 consecutive patients with ONHD and 27 eyes of 27 age-matched control subjects participated. INTERVENTION/METHODS:Ophthalmologic examination, color and red-free photography, automated Humphrey visual field testing, and OCT were performed. Each of the drusen study eyes were graded on a scale of 0 to III based on the amount of visible ONHD. Grade 0 represented the absence of clinically visible ONHD, and grade III represented an optic nerve head with abundant drusen. MAIN OUTCOME MEASURES/METHODS:Findings from clinical evaluation and color optic nerve head photographs and NFL evaluation by red-free photography, visual fields, and OCT were measured. RESULTS:The number of study eyes with visual field defects increased with the higher grade drusen discs, corresponding both with progressively thinner NFL measurements by OCT and NFL loss shown by NFL photography. The NFL evaluation showed NFL thinning by red-free photography in 12 (71%) of 17 eyes with visible drusen (grades I-III discs) and visual field defects in 9 (53%) of 17 eyes in this group. By OCT measurements, the superior and inferior NFLs were significantly thinner in the eyes with visible ONHD compared with those of control eyes in the superior quadrant (P < 0.001) and inferior quadrant (P = 0.004). Compared with grade 0 discs, grades I through III discs showed statistically significant thinning of the NFL superiorly (P < 0.001). No statistical significant thinning of the NFL was seen in grade 0 discs compared with those of control subjects. CONCLUSIONS:Optical coherence tomography is able to detect NFL thinning in eyes with ONHD and appears to be a sensitive and early indicator of NFL thinning. Increased numbers of clinically visible ONHD correlated with NFL thinning shown by OCT measurements and both visual field defects and NFL loss seen by red-free photography.

Objective: The purpose of the study was to determine the accuracy of applanation tonometry, pneumatonometry, and TonoPen tonometry in adults and children and the effect of age on tonometer error. Design: The design was divided into four parts: part 1 was prospective and cross-sectional, and parts 2 through 4 were prospective, cross-sectional, and masked. Participants: This study contained 72 patients representing 74 data points. Intervention: This study contained 72 patients representing 74 data points. Tonometry with simultaneous manometry was performed. Main Outcome Measures: Intraocular pressure (IOP) and the tonometric estimate of IOP were obtained. Results: The normal pediatric IOP follows the line Ta = 0.71 age(years) + 10 up to age 10. Applanation tonometry under anesthesia differs from pneumatonometry by an average of -8.6 mmHg and is age related by the equation Ta = Tpn + 2.6 log(age) -10.3. The TonoPen was the most accurate instrument for enucleated eyes, and the pneumatonometer was the most accurate in anesthetized living eyes. Conclusions: Applanation tonometry markedly underestimated IOP in young eyes. TonoPen tonometry performed well with enucleated eyes but was not adequately accurate for clinical use. The pneumatonometer performed the best clinically and the best overall.

Objective: This study aimed to develop a protocol to screen and monitor patients with diabetic macular thickening using optical coherence tomography (OCT), a technique for high-resolution cross-sectional imaging of the retina. Design: A cross-sectional pilot study was conducted. Participants: A total of 182 eyes of 107 patients with diabetic retinopathy, 55 eyes from 31 patients with diabetes but no ophthalmoscopic evidence of retinopathy, and 73 eyes from 41 healthy volunteers were studied. Intervention: Six optical coherence tomograms were obtained in a radial spoke pattern centered on the fovea. Retinal thickness was computed automatically from each tomogram at a total of 600 locations throughout the macula. Macular thickness was displayed geographically as a false-color topographic map and was reported numerically as averages in each of nine regions. Main Outcome Measures: Correlation of OCT with slit-lamp biomicroscopy, fluorescein angiography, and visual acuity was measured. Results: Optical coherence tomography was able to quantify the development and resolution of both foveal and extrafoveal macular thickening. The mean +/- standard deviation foveal thickness was 174 +/- 18 mu m in normal eyes, 179 +/- 17 mu m in diabetic eyes without retinopathy, and 256 +/- 114 mu m in eyes with nonproliferative diabetic retinopathy. Foveal thickness was highly correlated among left and right eyes of normal eyes (mean +/- standard deviation difference of 6 +/- 9 mu m). Foveal thickness measured by OCT correlated with visual acuity (r(2) = 0.79). A single diabetic eye with no slit-lamp evidence of retinopathy showed abnormal foveal thickening on OCT. Conclusions: Optical coherence tomography was a useful technique for quantifying macular thickness in patients with diabetic macular edema. The topographic mapping protocol provided geographic information on macular thickness that was intuitive and objective.

Optical coherence tomography (OCT) is a new diagnostic technology for high resolution, cross-sectional, quantitative imaging of the human retina. OCT is a noninvasive, noncontact technique which uses near infra-red, lowcoherent light passing through a Michaelson interferometer. OCT is essentially analogous to ultrasound B-mode imaging except that optical rather than acoustic reflectivity is measured. OCT is unique, amidst other current technologies, in its cross-sectional scanning of the tissue which provides "anatomic" tomographic representation of the retinal layers and their pathologies, and in its exceptionally high resolution (approximately 10 μm) and reproducibility. OCT provides powerful diagnostic information which is complementary to conventional studies such as fundus photography and fluorescein angiography, and is extremely useful in the diagnosis and monitoring of retinal disorders such as macular hole and macular edema of various origins, and for nerve fiber layer thickness measurement in glaucoma. In addition, OCT has the potential for a wide variety of corneal and anterior segment imaging

PURPOSE/OBJECTIVE:To investigate the biomechanical effect induced by radial keratotomy on outflow facility in paired, enucleated whole porcine eyes. METHODS:Freshly enucleated porcine eyes were perfused at a constant pressure of 10 mm Hg. Radial keratotomy (RK), with a 3.5 mm central clear zone and eight radial incisions, was performed using a diamond knife with the blade length set at 100% of the paracentral corneal thickness, as measured by pachymetry. The fellow eye of each pair received sham RK as a control. RESULTS:Seven pairs of eyes were perfused (RK group n = 7, control n = 7). There was no significant difference in the mean baseline of outflow facility between the paired experimental and control eyes preoperatively (p = 0.5). After RK, outflow facility increased by 46% (p < 0.001) in the treatment group, compared to a 7% (p < 0.04) increase in the control group, resulting in a 39% increase in outflow facility attributed to RK (p < 0.001). CONCLUSIONS:Radial keratotomy produced a statistically significant acute increase in outflow facility in freshly enucleated porcine eyes. We believe that this increase results from steepening of the peripheral corneal curvature and the concomitant stretching of the iridocorneal angle. Further studies are needed to evaluate this effect in human eyes and in vivo.

The purpose of the study was to evaluate the effect of erbium (Er): yttrium aluminum garnet (YAG) laser trabecular ablation with a sapphire optical fiber on outflow facility. After obtaining baseline outflow facility using a computerized differential pressure perfusion system, human cadaver eyes were subjected to Er: YAG laser trabecular ablation using a sapphire optical fiber. Single pulses at varying energy levels (10 to 20 mJ pulse-1) were applied in a nearly contiguous fashion over four clock hours of meshwork. Post-laser outflow facility was then determined utilizing the same perfusion system and histopathologic analysis performed. Of the ten eyes, nine were perfused to steady baseline facility. One eye was excluded from the study because of a leak in our system during the initial perfusion. The mean baseline facility was 0.283+/-0.08 microl min-1 mmHg-1. There was a significant increase in outflow facility after trabecular ablation, with a mean post-laser facility of 0.62+/-0.15 microl min-1 mmHg-1 (P=0.01). Eyes which received a sham treatment showed no increase or a minimal increase in facility. Histopathologic analysis revealed ablation into Schlemm's canal with some thermal damage to the outer wall at all energy levels. Er: YAG laser trabecular ablation with a sapphire fiber is capable of increasing outflow facility in human cadaver eyes.