Steady-state PERG adaptation: a conspicuous component of response variability with clinical significance.

PURPOSE: To investigate within-test variability of the steady-state PERG (SS-PERG). METHODS: SS-PERGs were recorded in response to black-white horizontal gratings (1.6 cycles/deg, 98% contrast, 15.63 reversals/s, LED display, 25 deg square field, 800 cd/sqm mean luminance) using skin electrodes. PERG and noise (± reference) signals were averaged over 1024 epochs (~ 2.2 min) and Fourier analyzed to retrieve SS-PERG amplitude and phase. SS-PERGs were split into 16 partial averages (samples) of 64 epochs each, and corresponding amplitudes and phases combined in polar coordinates to assess their dispersion (within-test variability). To assess time-dependent variability, samples were clustered in four successive time segments of ~ 33 s each. Amplitude adaptation was defined as amplitude difference between initial and final clusters, and PERG phase adaptation as the corresponding phase difference. To determine the dynamic range of SS-PERG adaptation, recording was performed in normal controls of different age (n = 32) and patients with different severity of optic nerve dysfunction (early manifest glaucoma, EMG, n = 7; non-arteritic ischemic optic neuropathy, NAION, n = 5). RESULTS: Amplitude adaptation was largest in younger controls (amplitude adaptation ÷ noise, SNR = 9.5, 95% CI 13.1, 5.9) and progressively decreased with increasing age (older subjects, SNR = 5.5, 95% CI 9.2, 1.8) and presence of disease (EMG: SNR = 2.4, 95% CI 3.5, 1.4; NAION: SNR = 1.9, 95% CI 6.5,-2.2). In 11 young subjects, amplitude adaptation was repeatable (test-retest in two sessions a week apart; intraclass correlation coefficient = 0.59). Phase adaptation was not significantly different from zero in all groups. CONCLUSIONS: SS-PERG adaptation accounts for a sizeable portion of the within-test variability. As it has robust SNR, sufficient test-retest variability, and is altered in disease, it may have physiological and clinical significance. This study suggests that SS-PERG protocols should include adaptation in addition to SS-PERG amplitude and phase/latency.

Altered Blood Flow in the Ophthalmic and Internal Carotid Arteries in Patients with Age-Related Macular Degeneration Measured Using Noncontrast MR Angiography at 7T.

BACKGROUND AND PURPOSE: Age-related macular degeneration is associated with reduced perfusion of the eye; however, the role of altered blood flow in the upstream ophthalmic or internal carotid arteries is unclear. We used ultra-high-field MR imaging to investigate whether the diameter of and blood flow in the ophthalmic artery and/or the ICA are altered in age-related macular degeneration and whether any blood flow changes are associated with disease progression. MATERIALS AND METHODS: Twenty-four patients with age-related macular degeneration and 13 similarly-aged healthy controls participated. TOF and high-resolution dynamic 2D phase-contrast MRA (0.26 × 0.26 × 2mm3, 100-ms effective sampling rate) was acquired at 7T. Vessel diameters were calculated from cross-sectional areas in phase-contrast acquisitions. Blood flow time-series were measured across the cardiac cycle. RESULTS: The ophthalmic artery vessel diameter was found to be significantly smaller in patients with age-related macular degeneration than in controls. Volumetric flow through the ophthalmic artery was significantly lower in patients with late age-related macular degeneration, with a significant trend of decreasing volumetric ophthalmic artery flow rates with increasing disease severity. The resistance index was significantly greater in patients with age-related macular degeneration than in controls in the ophthalmic artery. Flow velocity through the ophthalmic artery and ICA was significantly higher in patients with age-related macular degeneration. Ophthalmic artery blood flow as a percentage of ipsilateral ICA blood flow was nearly double in controls than in patients with age-related macular degeneration. CONCLUSIONS: These findings support the hypothesis that vascular changes upstream to the eye are associated with the severity of age-related macular degeneration. Additional investigation into the potential causality of this relationship and whether treatments that improve ocular circulation slow disease progression is warranted.

A comparison of cup-to-disc ratio estimates by fundus biomicroscopy and stereoscopic optic disc photography in the Tema Eye Survey.

PurposeTo determine if there are systematic differences in cup-to-disc ratio (CDR) grading using fundus biomicroscopy compared to stereoscopic disc photograph reading.MethodsThe vertical cup-to-disc ratio (VCDR) and horizontal cup-to-disc ratio (HCDR) of 2200 eyes (testing set) were graded by glaucoma subspecialists through fundus biomicroscopy and by a reading center using stereoscopic disc photos. For validation, the glaucoma experts also estimated VCDR and HCDR using stereoscopic disc photos in a subset of 505 eyes that they had assessed biomicroscopically. Agreement between grading methods was assessed with Bland-Altman plots.ResultsIn both sets, photo reading tended to yield small CDRs marginally larger, but read large CDRs marginally smaller than fundus biomicroscopy. The mean differences in VCDR and HCDR were 0.006±0.18 and 0.05±0.18 (testing set), and -0.053±0.23 and -0.028±0.21 (validation set), respectively. The limits of agreement were ~0.4, which is twice as large as the cutoff of clinically significant CDR difference between methods. CDR estimates differed by 0.2 or more in 33.8-48.7% between methods.ConclusionsThe differences in CDR estimates between fundus biomicroscopy and stereoscopic optic disc photo reading showed a wide variation, and reached clinically significance threshold in a large proportion of patients, suggesting a poor agreement. Thus, glaucoma should be monitored by comparing baseline and subsequent CDR estimates using the same method rather than comparing photographs to fundus biomicroscopy.

Long-term outcomes of neovascular glaucoma treated with and without intravitreal bevacizumab.

AIMS: To compare the outcomes of neovascular glaucoma (NVG) treated with and without intravitreal bevacizumab in a large case comparison study. METHODS: The study is a retrospective, comparative, case series of 163 eyes of 151 patients with NVG, including 99 treated without and 64 treated with intravitreal bevacizumab. Medical and surgical treatments for NVG were assessed. The main outcome measures were visual acuity (VA) and intraocular pressure (IOP). RESULTS: At the time of NVG diagnosis, the median VA was count fingers (CF) in the non-bevacizumab group and 2/300 in the bevacizumab group. IOP (mean±SD) was 43.1±13.0 mm Hg in the non-bevacizumab group and 40.8±11.5 mm Hg in the bevacizumab group. IOP (mean±SD) decreased to 18.3±13.8 mm Hg in the non-bevacizumab group and 15.3±8.0 mm Hg in the bevacizumab group, and the median VA was CF in both treatment groups at a mean follow-up of 12 months. Panretinal photocoagulation (PRP) substantially reduced the need for glaucoma surgery (P<0.001) in bevacizumab treated NVG eyes. CONCLUSIONS: Although bevacizumab delayed the need for glaucoma surgery, PRP was the most important factor that reduced the need for surgery. Vision and IOP in eyes with NVG treated with bevacizumab showed no long-term differences when compared with eyes that were not treated with bevacizumab. Thus, intravitreal bevacizumab serves as an effective temporizing treatment, but is not a replacement for close monitoring and definitive treatment of NVG. PRP remains the treatment modality that affects the course of NVG in terms of decreasing the need for surgery to control IOP.

Evaluation of baseline-related suprathreshold testing for quick determination of visual field nonprogression.

OBJECTIVE: To evaluate a commercially available means of baseline-related suprathreshold examination designed to detect visual field worsening. DESIGN: Patients for whom results of a baseline series of static-threshold visual field examinations were available underwent both a second static-threshold examination (full-threshold strategy; average time, 15 minutes) and a baseline-related suprathreshold examination ("fast-threshold" strategy; average time, 5 minutes). RESULTS: Most of the 1702 points examined were apparently unchanged from baseline, showing with either method only the degree of variation expected from the measurement inconsistency (short-term fluctuation). For points that did show a change, the changes shown by the two methods were correlated. Change in the field as a whole, represented by a cluster of locations showing deterioration, was evident more frequently with the standard testing strategy: 11 of 37 field examinations showed deterioration by both methods and an additional 11 examinations showed deterioration by the full-threshold method only. CONCLUSIONS: Each examination method identified pointwise changes not detected by the other, the combined effect of false-positive errors (imperfect specificity) and false-negative errors (imperfect sensitivity) with each of the two methods. The findings relating to clusters could represent a better sensitivity of the full-threshold method in detecting visual field deterioration, a better specificity of the suprathreshold method, or both.

Statpac 2 glaucoma change probability.

We compared the traditional intuitive criterion (fixed at 5 dB) with the variable Statpac 2 criterion of the Humphrey Field Analyzer for identifying visual deterioration at individual points within a visual field. The separation of depressed from stable points in 123 follow-up fields of 17 patients, when all points within a field were considered, was reasonably equivalent between the two methods (kappa = 0.55 +/- 0.027 [+/- SE]). Centrally located points within the field demonstrated a stronger agreement (kappa = 0.68 +/- 0.028), because the fixed criterion more often labeled the edge points as having progressed than did the Statpac 2 algorithm. The glaucoma change probability printout is more simply obtained than the manual comparison required for intuitive interpretation with a fixed criterion, and it is potentially more accurate because of its reliance on a database that permits a variable criterion to be applied.

Rebleeding after traumatic hyphema.

We reviewed the medical records of 175 patients who were admitted between 1977 and 1984 with a diagnosis of traumatic hyphema to define the incidence of operative intervention for the treatment of complications related to rebleeding. Of the 156 patients admitted with primary hyphemas, 25 (16%) rebled during hospitalization. Seven of these 25 in-hospital rebleeds required surgical intervention. Nineteen other patients were admitted with ocular histories and examinations strongly suggestive of rebleeding prior to admission (secondary hyphema--presumed preadmission rebleed). Seven of these 19 eyes underwent surgery. Of the 175 eyes studied, only one eye that did not rebleed underwent surgery during the initial hospitalization. Fourteen (32%) of 44 eyes that rebled underwent operative intervention. Nine of these 14 patients were operated on under general anesthesia. Potential benefits of newer hyphema treatments, such as epsilon-aminocaproic acid, designed to prevent rebleeding should be weighed against not only the ocular risks of rebleeding but also the risks of general anesthesia.

The influence of simulated light scattering on automated perimetric threshold measurements.

The effect of light scattering by ocular media opacities on OCTOPUS and Humphrey perimeter threshold measurements was simulated with randomly ordered sequences of six ground-glass diffusers in the right eyes of five subjects. Threshold measurements were performed at 0 degrees, 5 degrees, 10 degrees, 15 degrees, 20 degrees, and 25 degrees nasally along the 180 degrees meridian with the F4 program on an OCTOPUS perimeter, and with twice-repeated profiles on a Humphrey perimeter. The reduction in differential light sensitivity correlated well with the 2.7-dB to 16.7-dB reduction in stimulus intensity caused by the 46% to 98% scattering of incident light by the diffusers. Contrast sensitivity in the presence of a glare source (Miller-Nadler glare test) was also affected by the diffusers, such that a 75% contrast target was not visible through the strongest diffuser whereas a 5% contrast target was visible without a diffuser. Conversely, the diffusers had very little effect on visual acuity measurements that were performed with projected high-contrast targets in a darkened room. Our data suggest that even minimal light scattering, such as might be caused by a cataract that has a relatively insignificant effect on visual acuity, may influence threshold measurements.

Screening for retinopathy of prematurity employing the retcam 120: sensitivity and specificity.

OBJECTIVES: To compare the method of photographic screening using the RetCam 120 to the standard method of screening for retinopathy of prematurity (ROP) by ophthalmologic examination. METHODS: A total of 100 RetCam 120 photoscreening examinations of the retina were performed on 32 premature infants. These were stored in a separate file from which all identifying information was removed. At this same examination, a detailed ophthalmological evaluation, employing the indirect ophthalmoscope with scleral depression, was performed by an experienced examiner. Masked examiners performed an evaluation of the fundus photographs to identify presence or absence of ROP, the location and extent of the disease, and the presence or absence of plus disease. These data were then compared with the results of the ophthalmological examination to determine the specificity, sensitivity, and the positive and negative predictive value (PPV and NPV) of the method. RESULTS: Retinopathy of prematurity was detected in 68 of 100 subjects by ophthalmologic examinations and in 58 of 100 subjects' photoscreening examinations. No ROP was detected in 32 of 100 subjects. The sensitivity of the method was 56 (82.4%) of 68 and the specificity was 30 (93.8%) of 32. The PPV was 96.6%; NPV, 76.9%. CONCLUSIONS: The sensitivity of the method was low. The ROP that was missed was peripheral stage 1 or stage 2 disease in peripheral zone 2 or zone 3. This was largely due to the technical limitations of the speculum-camera interface preventing a better view of the periphery. The ROP cases that were missed by the photographic examination regressed spontaneously on follow-up. No disease more posterior to peripheral zone 2 was overlooked. These results detail the accuracy of the method employing the technique of photoscreening as a potential substitute for detailed ophthalmological examination. At present there are clear technical limitations to such a substitution. The study is part of an ongoing project to determine the feasibility of employing neonatal nurses trained to take digitized images of the premature infant's retina and telemeter the results to be read by an experienced ophthalmologist remote from the site.

Relationships between laser flare photometry values and complications of uveitis.

OBJECTIVE: To determine whether relationships exist between elevated laser flare photometry values and common abnormalities and complications associated with uveitis. METHODS: We retrospectively studied all patients with uveitis on whom laser flare photometry measurements ("flare") were obtained (N = 111) at 2 academic medical centers. The first laser flare photometry values obtained for each patient were compared with the presence or absence of the following abnormalities or complications associated with uveitis: keratic precipitates, posterior synechiae, cataract, macular edema, optic disc edema, and glaucoma. In bilateral cases, the eye with the higher flare was used in primary analyses. RESULTS: Flare was significantly higher in patients with posterior synechiae (P<.001) and in those with macular edema (P =.02) than in patients with uveitis who did not have these complications. Flare was significantly higher in patients with prior cataract surgery or cataract at the study visit than in those without cataracts (P =.001). There was no significant difference in flare between patients with and without keratic precipitates, optic disc edema, or glaucoma. No relationships were found between abnormalities or complications and the level of inflammatory cells or flare as determined by clinical assessment. We also identified an inverse relationship between flare and visual acuity that was not completely explained by the presence of complications in a stepwise regression model. CONCLUSIONS: Although causal relationships were not established, associations between flare and some complications of uveitis suggest that aqueous humor protein may be an important factor in the development of these problems. Consequently, laser flare photometry could play a role in predicting outcomes or monitoring therapy for patients with uveitis.

Iritis and hypotony after treatment with intravenous cidofovir for cytomegalovirus retinitis.

OBJECTIVE: To describe intraocular inflammation due to treatment with intravenous cidofovir dihydrate for cytomegalovirus retinitis. DESIGN: Retrospective cohort. SETTING: Three university outpatient ophthalmology clinics. PATIENTS: All patients treated with intravenous cidofovir therapy before October 31, 1996. INTERVENTION: Treatment with intravenous cidofovir was given according to standardized protocols. Intraocular inflammation was treated according to the best medical judgment. MAIN OUTCOME MEASURES: The presence of new intraocular inflammation, the severity of inflammation, visual acuity, and intraocular pressure. RESULTS: Eleven cases of iritis (26%) occurred among 43 patients. In 6 cases, the iritis was bilateral. Patients who experienced iritis were more likely to have been previously treated for cytomegalovirus retinitis (P = .03), to be diabetic (P = .05), or to be receiving protease inhibitors (P < .001). Four patients and 15 control subjects had also taken rifabutin (P = .70). The onset of iritis occurred at a mean (+/-SD) of 4.9 +/- 1.8 days after a cidofovir dose and after a mean (+/-SD) of 4.2 +/- 1.6 doses of cidofovir. Six eyes of 4 patients had hypotony. Five eyes of 5 patients had a persistent decrease in visual acuity of at least 2 Snellen lines. CONCLUSIONS: Acute intraocular inflammation may occur with or without hypotony after intravenous cidofovir therapy, similar to the reactions seen after intravitreous administration. Although the manifestations may be severe, they are manageable with topical corticosteroid therapy in most cases. Cidofovir therapy can be continued in some patients if medical necessity warrants, but recurrent inflammation or permanent hypotony may occur.

Visual function and quality of life among patients with glaucoma.

This study determines the relation between visual field impairment, visual functioning, and global quality of life in patients with glaucoma. Binocular visual field impairment was calculated from simultaneous Esterman visual field testing using the Humphrey automated perimeter. Visual acuity impairment, defined with the American Medical Association's Guides to the Evaluation of Permanent Impairment; visual functioning, measured with the VF-14 and the field test version of the National Eye Institute-Visual Functioning Questionnaire; and global quality of life, assessed with the Medical Outcomes Study 36-Item Short Form Health Survey, were determined in 147 consecutive patients with glaucoma. None of the Medical Outcomes Study 36-Item Short Form Health Survey domains demonstrated more than a weak correlation with visual field impairment. The VF-14 scores were moderately correlated (r = -0.58). Of the National Eye Institute-Visual Functioning Questionnaire scales, peripheral vision (r = -0.60), distance activities (r = -0.56), and vision-specific dependency (r = -0.56) were moderately correlated with visual field impairment; vision-specific social functioning, near activities, vision-specific role difficulties, general vision, vision-specific mental health, color vision, and driving were modestly correlated with visual field impairment (r value between -0.32 and -0.55); visual pain was weakly correlated with visual field impairment; and general health and vision-specific expectations were not notably correlated with visual field impairment. Statistically adjusting for visual acuity weakened the correlations. The Medical Outcomes Study 36-Item Short Form Health Survey indicated that our patients with glaucoma were comparable with previously studied patients without severe systemic medical problems. However, the Medical Outcomes Study 36-Item Short Form Health Survey scores did not correlate with visual field impairment in our study. Based on the moderate correlation between binocular visual field impairment with the VF-14 and the National Eye Institute-Visual Functioning Questionnaire, these questionnaires may be useful among patients with glaucoma.

External beam radiotherapy in retinoblastoma: tumor control and comparison of 2 techniques.

OBJECTIVE: To investigate eye conservation, local control, and complication rates among children with retinoblastoma treated with 2 different external beam radiotherapy (EBR) techniques. METHODS: Fifty-eight eyes in 42 patients received EBR as the primary treatment modality for retinoblastoma (median follow-up, 37 months). The EBR technique was relative lens-sparing (RLS) in 26 eyes and modified lateral beam (MLB) in 32 eyes. Both groups were comparable in Reese-Ellsworth retinoblastoma classification. If necessary, patients received focal salvage therapy. RESULTS: At 24 months, eye conservation rates were 88.5% and 89.1% among eyes treated with RLS and MLB, respectively (P = .40); tumor control rates without salvage therapy were 84.6% and 53.3% (P = .02), respectively. Among eyes with Reese-Ellsworth stage IV and V disease, eye conservation rates were 88%+/-8% and 83%+/-9% at 36 months in the RLS and MLB groups, respectively, and local tumor control rates were 81%+/-10% and 51%+/-12%. Percentages of eyes without cataract at 36 months were 83.1% and 63.0%, respectively (P = .40). Among patients observed for at least 18 months, midfacial hypoplasia developed in 38.5% and 29.4%, respectively (P = .70). CONCLUSIONS: The EBR technique was associated with high eye conservation and local control rates. Salvage therapy was performed significantly less frequently in the RLS group compared with the MLB group, and complication rates in both groups were similar.

Elevated intraocular pressure and hypotony following silicone oil retinal tamponade for complex retinal detachment: incidence and risk factors.

OBJECTIVE: To evaluate the incidence of and risk factors for persistently elevated intraocular pressure (IOP) and hypotony in patients who have undergone pars plana vitrectomy with silicone oil injection for the management of complex retinal detachment. SUBJECTS AND METHODS: The medical records of 532 patients who underwent silicone oil injection for the management of complex retinal detachments between January 1, 1991, and December 31, 1996, at the Bascom Palmer Eye Institute, Miami, Fla, were reviewed. Elevated IOP was defined as elevated IOP requiring an operation at any time postoperatively or a persistently elevated IOP of greater than 25 mm Hg at or after the 6-month visit. Hypotony was defined as a persistent IOP of 5 mm Hg or less at or after the 6-month visit. Patients with transient perioperative IOP fluctuations were not counted. RESULTS: Survival analysis for patients without cytomegalovirus retinitis (n = 383) revealed that 12.9% had an elevated IOP and 14.1% had hypotony by 6 months, 21% had an elevated IOP and 20.3% had hypotony by 1 year, and 29.5% had an elevated IOP and 27.3% had hypotony by 2 years. Among patients with cytomegalovirus retinitis (n = 149), none had a persistently elevated IOP, 10% had hypotony by 6 months, and 5.9% had persistently elevated IOP and 10% developed chronic hypotony by 1 year. A history of glaucoma before silicone oil retinal tamponade (P = .03), diabetes mellitus (P = .02), and a high IOP on the first postoperative day (P = .006) were risk factors for elevated postoperative IOP in patients without cytomegalovirus retinitis. Risk factors for postoperative hypotony in patients without cytomegalovirus retinitis included preoperative hypotony (P<.001) and aphakia (P = .03). CONCLUSIONS: An elevated or low IOP often develops postoperatively in patients without cytomegalovirus retinitis who undergo silicone oil injection for the management of complex retinal detachment. Risk factors for an elevated postoperative IOP include a history of glaucoma, diabetes mellitus, and a high IOP on the first postoperative day. Risk factors for hypotony include preoperative hypotony and aphakia.

Baerveldt drainage implants in eyes with a preexisting scleral buckle.

OBJECTIVE: To describe the surgical insertion of a Baerveldt drainage implant and postoperative visual acuity and intraocular pressure (IOP) outcomes in patients with a preexisting scleral buckle. METHODS: Medical records of all patients with a preexisting scleral buckle who underwent insertion of a Baerveldt drainage implant at Bascom Palmer Eye Institute, Miami, Fla, from January 1, 1994, through December 31, 1998, were reviewed. Outcome measures included visual acuity and IOP at 1 year. RESULTS: At 1 year postoperatively, 14 (88%) of 16 patients had stable or improved visual acuity. Preoperatively, mean IOP was 30.9 mm Hg and the mean number of antiglaucoma medications was 3.4; at 1 year postoperatively, mean IOP was 12.0 mm Hg and the mean number of antiglaucoma medications was 0.8 (P<.001). Nine patients (56%) achieved an IOP of greater than 5 and no greater than 21 mm Hg without medication, and an additional 7 (44%) achieved this level of IOP control with medication. No patient required further surgery for uncontrolled IOP during the follow-up interval, which ranged from 19. 1 to 45.5 months. CONCLUSION: Baerveldt drainage device insertion behind or over a preexisting encircling band is often successful in managing refractory glaucoma in patients who have undergone previous scleral buckling procedures. Arch Ophthalmol. 2000;118:1509-1513

Peripapillary vasoconstriction in the glaucomas and the anterior ischemic optic neuropathies.

Proximal constriction (retinal arteries narrower near the disk than further down the stream in the retina) was present in 96 of 226 eyes (42%) with classic glaucoma or normal-tension glaucoma, but it was present in only 11 of 206 eyes (5%) that were normal, had ocular hypertension, or had retinal disease not affecting the optic nerve. In cases of glaucoma with proximal constriction over only part of the disk circumference, its location corresponded to the sector with the greatest cupping in 60 of 66 cases (91%) and likewise corresponded to the sector in which the peripapillary zone of absent retinal pigment epithelium was widest in 48 of 55 cases (87%). Proximal constriction was also present in 16 of 45 eyes (36%) with nonischemic types of non-glaucomatous optic atrophy. The nonarteritic form of anterior ischemic optic neuropathy had proximal constriction in 19 of 28 eyes (68%), which was more frequent than in those with glaucoma (P = .017). Only one of nine eyes with the arteritic form of anterior ischemic optic neuropathy had proximal constriction, which was lower prevalence than in those with glaucoma (P = .066). General arterial narrowing (throughout the retinal course) was present in 111 of 204 (54%) of those with moderate optic nerve damage and 100 of 128 (78%) of those with severe optic nerve damage in all categories, compared with 29 of 208 (14%) of the controls with no optic nerve damage. Unlike proximal constriction, the generalized narrowing was related to severity of optic nerve damage and not to the disease category.

The effect of punctal occlusion on tear production, tear clearance, and ocular surface sensation in normal subjects.

PURPOSE: To evaluate the effect of temporary punctal occlusion on tear production, tear clearance, and ocular surface sensation in normal subjects. METHODS: Noncomparative interventional case series. Punctal occlusion with silicone punctal plugs was performed on nine normal subjects without complaints of ocular irritation and no known history of ocular surface disease. The lower punctum of both eyes was occluded in five subjects. The upper and lower puncta of only one eye were occluded in four subjects. Corneal and conjunctival sensations were measured with the Cochet-Bonnet anesthesiometer. Tear fluorescein clearance was evaluated with a CytoFluor II fluorophotometer by measuring the fluorescein concentration in minimally stimulated tear samples collected from the inferior tear meniscus 15 minutes after instillation of fluorescein. Schirmer test was performed without anesthesia. The tests were performed at days 0, 1, 3, 7, and 14 to 17 after punctal occlusion. Relationships were analyzed with linear regressions, and a quadratic term was used to model a return to preocclusion levels. Paired t test was used to study the change in tear fluorescein concentration. RESULTS: In subjects who had the lower puncta of both eyes occluded, conjunctival sensation decreased in both eyes (right eye, P =.008; left eye, P =.003), but there was no change in corneal sensation. Their tear fluorescein clearance did not show a significant change from baseline (P =.90). However, a decrease in Schirmer test scores approached statistical significance (P =.056). In subjects with both puncta of only one eye occluded, we noted a decrease in corneal sensation (occluded eye, P =.042; nonoccluded eye, P =.036), conjunctival sensation (occluded, P =.001; nonoccluded, P =.060), and Schirmer scores (occluded, P =.022; nonoccluded, P =.011). Linear regression did not show a significant change in tear fluorescein clearance for either eye (occluded, P =.28; nonoccluded, P =.44). However, paired t test showed a significant worsening of tear clearance in the occluded eye from day 0 to day 3 (P =.001) followed by a subsequent improvement in tear clearance from day 3 to the end of the study period (P =.045). Paired t test did not reveal any significant changes in tear clearance in the nonoccluded eye. The quadratic term of the linear regression model demonstrated an increase toward preocclusion levels that approached statistical significance for corneal sensation (occluded, P =.053; nonoccluded, P =.099). It was statistically significant for conjunctival sensation (occluded, P =.001; nonoccluded, P =.045) and Schirmer scores (occluded, P =.047; nonoccluded, P =.044). CONCLUSIONS: Temporary punctal occlusion in normal subjects decreases tear production and ocular surface sensation. Our findings suggest that in addition to blocking tear drainage, punctal occlusion may affect the ocular surface/lacrimal gland interaction. These effects were more pronounced in subjects with both upper and lower puncta occluded. In normal subjects, there appears to be an autoregulatory mechanism to return tear production, tear clearance, and ocular surface sensation to preocclusion levels 14 to 17 days after punctal occlusion.

Evaluation of phototoxic retinal damage after argon laser iridotomy.

We performed several visual function tests in 17 eyes (ten patients) before and after argon laser iridotomy in an effort to detect diffuse photochemical damage to photoreceptors caused by exposure to the intense, blue-green light that is transmitted into the posterior segment as the iridotomy is created and enlarged. No change was detected in static threshold sensitivity in the central 30 degrees of the field (Octopus perimeter), color sensitivity (Farnsworth-Munsell 100-Hue test), or visual acuity. Contrast sensitivity showed a small increase at low spatial frequencies and a small decrease at high spatial frequencies. The latter change was small and not necessarily laser related, but precautions to limit laser exposure of the posterior pole are prudent.

The influence of decreased retinal illumination on automated perimetric threshold measurements.

Decreased retinal illumination (such as can be caused by pupillary constriction or light absorption by ocular media opacities) was simulated with a randomly ordered series of neutral density filters in front of the right eyes of five subjects with dilated pupils. Threshold measurements were performed on Humphrey and Octopus perimeters at 0, 5, 10, 15, 20, and 25 degrees nasally along the 180-degree meridian. A 0.6-log unit neutral density filter, which reduces retinal illumination the equivalent of halving the pupillary diameter, decreased the mean Humphrey thresholds by 1.1 +/- 0.8 decibels (dB) (mean +/- standard deviation) and the mean Octopus thresholds by 1.7 +/- 1.4 dB. Statistically significant (P less than or equal to .05, Dunnett's test) threshold depressions were observed at all eccentricities with a 1.5-log unit neutral density filter on the Humphrey perimeter (-4.5 +/- 0.7 dB) and with a 1.0-log unit neutral density filter on the Octopus perimeter (-3.5 +/- 1.0 dB).

Retinopathy of prematurity in multiple-gestation pregnancies.

PURPOSE: To determine differences in incidence of retinopathy of prematurity between neonates of multiple-gestation and single-gestation pregnancies and to analyze differences in severity of retinopathy of prematurity among siblings of multiple-gestation pregnancies. METHODS: We reviewed the records of 149 neonates of multiple-gestation pregnancies and 691 single-gestation neonates screened for retinopathy of prematurity at one hospital from January 1, 1992, through December 31, 1995. The peak stage of retinopathy of prematurity was recorded for all infants. The multiple-gestation infants were then separated into concordant and discordant retinopathy of prematurity groups, with discordance defined as a difference of at least 2 stages of retinopathy of prematurity between siblings. Between siblings with discordant retinopathy of prematurity, multiple factors were compared. RESULTS: Retinopathy of prematurity was present in 69 (46%) of the multiple-gestation neonates. Retinopathy of prematurity was present in 312 (45%) of single-birth neonates. The percentage of multiple-gestation neonates with stages 1, 2, or 3 (prethreshold) or threshold retinopathy of prematurity was similar to that of single-gestation neonates. Stage 4 or 5 retinopathy of prematurity did not occur in either group. CONCLUSIONS: There was no significant difference in stage of retinopathy of prematurity between infants of single-gestation pregnancies vs those of multiple-gestation pregnancies. The majority (84%) of infants of multiple-gestation pregnancies had concordant retinopathy of prematurity. In those infants with discordant disease, zygosity and postgestational factors other than lowest serum glucose were not related to severity of retinopathy of prematurity.