Fixation characteristics in macular disease. Relationship between saccadic frequency, sequencing, and reading rate.

The relationship between reading rate and saccadic frequency in patients with macular degeneration was studied to determine if this simple measure of eye movements would be helpful in explaining the reduction in reading rates. Nineteen subjects and five controls were tested for visual acuity, reading rate, and saccadic frequency for intended stationary, simple left-to-right, and sequencing step tasks. Eye movements were recorded using an electro-oculography technique. Absolute eye position was not known. The results demonstrated that, using a 2 degree threshold for a stationary target, patients refixated a mean of 42.7 times per min, and controls refixated 0.00 times per min. For a two-letter left-to-right task, patients averaged 3.57 times more saccades than an ideal response, and controls had 1.14 times more saccades than ideal (P less than 0.01). For a five-letter left-to-right sequencing task, patients refixated a mean of 2.10 times more than ideal, and controls refixated 1.15 times more than ideal (P less than 0.05). Regression analysis demonstrated that sequencing task scores of saccadic frequency and visual acuity were the best predictors of reading rate (r2 = 0.705). These results indicate that higher saccadic frequencies are associated with lower reading rates and that there appears to be a relationship between the sequencing of visual information and reading rate.

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.

X-linked recessive retinitis pigmentosa. Clinical characteristics of carriers.

We evaluated 46 carriers of X-linked recessive retinitis pigmentosa for the prevalence of fundus changes, refractive errors, central visual impairment, and electroretinographic abnormalities. Of the 46 carriers, 40 (87%) could be identified by characteristic fundus changes and 37 (86%) of 43 by reductions in electroretinographic amplitude. Interestingly, 36 carriers (78%) had a refractive cylindrical correction of +1.50 diopters (D) or greater in at least one eye, while 25 (54%) had a best corrected visual acuity of 20/30 or less in at least one eye. Fundus examination coupled with an electroretinographic recording was diagnostic of the carrier state in virtually all 46 patients. The presence of a refractive cylinder of +1.50 D or greater should appreciably increase the index of suspicion when assessing the possibility of the carrier state in X-linked retinitis pigmentosa.

Treatment of low vision in fundus flavimaculatus.

Twenty-eight patients with fundus flavimaculatus were evaluated retrospectively after they had undergone examination for and treatment of low vision. Despite poor distance acuity, 27 (96%) of the patients could read 1M (20/50 reduced Snellen) or smaller print with a spectacle lens, and all patients could read standard-sized print (1M text) with some optical aid. Because such uniform improvement is uncommon among patients with low vision, we recommend examination for and trial of low-vision aids for those patients with this disorder who are having visual difficulties.

Characteristics of normal corneal topography using the EyeSys corneal analysis system.

PURPOSE: To study the parameters of corneal topography of normal eyes using the Corneal Analysis System (CAS, EyeSys Technologies) to determine the types and frequency of patterns and parameters. SETTING: University of Illinois Eye Center, Chicago, Illinois, USA. METHODS: Three independent, masked judges, using a forced-choice paradigm, classified corneal topography patterns into six categories on one randomly selected, normal eye of 100 persons who did not wear contact lenses. The patterns were defined by using the midpoint dioptric bin and a 0.50 diopter (D) steeper bin. RESULTS: The pattern frequency using the mid-dioptric bin was teardrop (6%), amorphous (11%), round (11%), symmetric bow tie (17%), asymmetric bow tie (1 %), kidney (22%), and oval (32%). Mean refractive and keratometric cylinders, respectively, were teardrop (0.13 and 0.15 D), amorphous (0.15 and 0.49 D), round (0.18 and 0.56 D), oval (0.21 and 0.56 D), kidney (0.51 and 0.72 D), and bow tie (1.18 and 1.82 D). Pattern frequency using the 0.50 D steeper bin was round (2%), oval (5%), teardrop (6%), kidney (15%), amorphous (17%), asymmetric bow tie (17%), and symmetric bow tie (37%). Mean refractive and keratometric cylinders, respectively, were round (0.13 and 0.32 D), amorphous (0.25 and 0.38 D), kidney (0.11 and 0.42 D), oval (0.40 and 0.59 D), teardrop (0.08 and 0.75 D), and bow tie (0.65 and 1.09 D). Mean flat and steep contours were 41.76 D (95% confidence interval [CI], 38.68 to 44.84 D) and 44.15 D (95% CI, 41.00 to 47.31 D), respectively. Mean contour range was 2.40 D (95% CI, 0.61 to 4.17 D). CONCLUSION: The data suggest that for 95% of normal corneas, corneal contours will be steeper than 38.50 D, flatter than 47.50 D, and have a contour range less than 4.25 D when using the EyeSys CAS.

Twenty-five years of contact lenses: the impact on the cornea and ophthalmic practice.

PURPOSE: The history of contact lenses has occurred in the latter half of the 20th century. In particular, events in the 1970s through the 1980s related to the invention of soft, hydrogel contact lenses have revolutionized the contact lens industry and the eye care attached to it. This article recounts that history from the perspective of market forces, inventions, and discoveries about the physiologic functioning of the cornea. METHODS: The relevant literature is critically reviewed. RESULTS: Discoveries about the oxygen needs of the cornea and consumer pressure for clear, comfortable, around-the-clock vision have resulted in a history of rigid gas permeable and soft lenses that leads to today's contact lens picture. The short-term and long-term effects of chronic hypoxia and the levels of lens oxygen transmissibility necessary to avoid them have been well-described. The advent of the soft lens, followed by the "human experiment" with initial extended-wear modalities, led to the advent of the disposable soft contact lens. CONCLUSIONS: In the past 25 years, the development and wide acceptance of soft contact lenses have revolutionized the management of refractive error and corneal diseases.

Discordance for keratoconus in two pairs of monozygotic twins.

PURPOSE: We present two pairs of monozygotic twins discordant for keratoconus. METHODS: Two pairs of twins, each with one twin with keratoconus, and available family members were examined clinically and with computer-assisted videokeratography. Polymerase chain reaction-based zygosity assays using between nine and 11 unique, anonymous DNA markers were performed on blood obtained from the twins and surviving parents to assess the probability of genetic monozygosity. RESULTS: DNA probes showed a >99% probability that each of the two sets of twins was monozygotic. One twin from each pair had clinically diagnosed keratoconus. The remaining twins were normal by clinical examination and corneal topography. Clinical results for all family members examined were normal except that five of 13 from one family and one of six from the other family demonstrated "suspicious" corneal topography. CONCLUSION: Recent advances in knowledge and understanding of the twinning process suggest that monozygotic twins discordant for keratoconus does not preclude the possibility of a significant genetic component.

Corneal trauma: I--Classification and management.

Ocular trauma is common and frequently impairs vision. Injuries to the cornea account for approximately two thirds of ocular trauma. Appropriate detection, diagnosis, triage, and treatment decisions are needed in cases of corneal trauma to achieve maximum benefit for the traumatized patient. In this article, the prominent features of corneal trauma are reviewed, and a practical method of classification is presented to assist in management decisions.

Effects of long term extended wear of PMMA lenses on corneal function: a case report.

BACKGROUND: Recent studies have shown that some long-term PMMA contact lens wearers who are presumably exposed to hypoxia can develop modest but permanent changes in corneal structure and function. What is not known is the corneal effects that may result from severe and long-term exposure to an hypoxic environment. This case report is presented to illustrate an extreme example of the effects of the cornea from prolonged exposure to hypoxia. METHODS: A 37-year-old male who had worn PMMA lenses on a 2-week extended wear basis for 20 years was examined in the laboratory to assess changes in corneal structure and function. Function was determined by monitoring the rate at which the cornea recovered from induced edema and is expressed as a percent recovery per hour (PRPH). Morphology was studied via specular microscopy. RESULTS: For this subject, the PRPH was 39.6 percent/hr and 40.5 percent/hr for right and left eyes respectively; these values are substantially reduced compared to the reported 55.3 percent/hr for an age-matched, non-contact lens wearing population. Specular microscopy demonstrated reduced cell counts of 1,052 cells/mm2 OD and 1,741 cells/mm2 OS compared to an age adjusted normal population with 2,853 +/- 320 cells/mm2. CONCLUSIONS: This case example appears to represent an extreme case of contact lens abuse and the effects of long-term hypoxic contact lens wear on corneal function.

NoIRs and low vision.

Records of three hundred and eighteen low vision patients from three low vision centers were reviewed to determine patient preferences for NoIR light filters based on ocular disease and visual acuity. Eighty-nine percent chose the #101 and #102 filters. Patients with dry macular degeneration, chronic open angle glaucoma, and retinitis pigmentosa showed a greater preference for the #101 NoIRs. When visual acuity dropped below 20/400, no patients selected the darker filters (#108 & #109).

X-linked juvenile retinoschisis.

X-linked juvenile retinoschisis is an infrequently occurring inherited disease affecting males. Female carriers are phenotypically normal. A stellate or wheel-spoke macular cystic appearance is considered by some to be pathognomonic for the disease in early stages. One half of the cases also have peripheral retinal and vitreal defects. We review the fundus changes, histologic characteristics, visual course and electrophysiologic findings of the disease, and describe an illustrative case and its low vision management.

Hypertensive choroidopathy.

Ocular manifestations of hypertension involve both retinal and choroidal circulation. Clinical and pathological studies suggest that choroidal changes are present in benign and malignant hypertension, though significantly greater in the later. Lesions classically described as Siegrist and Elschnig spots are described. Clinical evidence of choroidopathy from hypertension and arteriosclerosis has a significant prognostic value for life.

Treatment of low vision in the progressive cone dystrophies.

Twenty-three patients suffering from the progressive cone dystrophies (PCD) were evaluated retrospectively, after they had undergone treatment for low vision. All patients were able to read 1 M or smaller print with magnification, despite poor central acuity. Eighteen (78%) patients achieved their primary rehabilitation goal, and 86% of the low vision devices prescribed were used at follow-up. Photosensitivity was reported by a large number of patients. Seven patients indicated that alleviating this problem was their primary rehabilitation goal. Eight (35%) found sun filters to be helpful. Our successful experience with patients with these disorders suggests that examination for, and trial of, low vision devices is warranted.

Multivariate assessment of computer-analyzed corneal topographers.

Methodological aspects of multivariate statistical models to describe and to assess data from computer-analyzed corneal topographers (CACT) are considered. The data generated by repeated curvature mappings of calibrated steel balls are discussed in detail with the objective of formulating the basic questions and suggesting directions to assess data from clinical applications of CACT. The interpretation of seemingly straightforward concepts such as accuracy and precision is revisited with the objective of understanding its meaning in future clinical and experimental applications of CACT. Some of the statistical problems related to the analysis of corneal astigmatism based on CACT data are also discussed.

Saccadic eye movements as a measure of the effect of low vision rehabilitation on reading rate.

We assessed saccadic eye movements and reading capabilities in individuals with macular disease by a masked clinical study to determine whether changes in saccadic frequency were correlated to changes in reading rates or number of errors for a reading task. We used a measure of eye movement characteristics in the form of a saccadic frequency score (SFS). Twelve subjects with macular disease were tested before and after an intense 6-week inpatient vision rehabilitation program. The mean age was 70.9 years (63 to 77 years). Mean visual acuity was 10/100 (10/40 to 10/200). Mean reading rates at entry and discharge were 8.5 words/min and 20.9 words/min, respectively (p = 0.02). SFS improved from 2.709 to 2.022 (p = 0.07). Reading errors improved from 5.60 to 4.00 (p = 0.03). Reading rates and SFS's were highly inversely correlated both pre- and post-treatment (Pearson r = -0.892 and -0.896, respectively). SFS and the number of reading errors were highly correlated with both pre- and post-treatment as well (Pearson r = 0.782 and 0.601, respectively). Interestingly the data appeared to cluster into two groups, one showing improvement and the other showing none. Cluster analysis revealed a strong association among reading rate, saccade scores, and reading errors. Membership in the two clusters is consistent pre- and post-rehabilitation in all but one case. Clustering is most evident for reading rate and reading errors and less so for saccade scores.(ABSTRACT TRUNCATED AT 250 WORDS)

The spectrum of topography found in keratoconus.

In order to more completely understand the topographic changes associated with keratoconus we performed computer-analyzed, digitized, videokeratoscopy (CADVK) on 23 patients with clinically documented keratoconus, using the EH-270 Corneal Topographer (Visioptic, Houston, TX). The majority of analyzed eyes demonstrated the classic picture of a well defined zone of inferior to inferotemporal steepening. However, several other topographic patterns were noted, including: nasal, superior, and central steepening, as well as extension of the inferior steepening superiorly. Additionally, significant flattening was found in some portions of the cornea away from the cone, particularly in the superonasal quadrant. In all cases, the precise location and degree of steepening could be easily defined. Interestingly, for both typical and atypical topographic patterns, marked symmetry between eyes in each patient was noted. The use of CADVK may allow for a more thorough appreciation of the diverse and complex topographic abnormalities associated with keratoconus, information which could aid in contact lens management and design.

Precision of three topography instruments in keratoconus subjects.

PURPOSE: To determine the test-retest reliability of three popular and commercially available Placido-ring videokeratography instruments in subjects with keratoconus. METHODS: Nine subjects (16 eyes) with keratoconus of varying degrees of severity had up to four images per eye generated, in random order, from the EyeSys Model II, Dicon CT 200 and the Keratron Corneal Analyzer. Test-retest analyses for the images were sampled at four locations: 1.5 mm nasal, inferior, temporal, and superior from center. The average standard deviation of all points was used to determine the short-term variability of the measurements. RESULTS: The short-term variability (in diopters) of the Dicon, EyeSys, and Keratron was 0.61 to 3.31 D, 0.94 to 1.51 D, and 0.58 to 2.85 D, respectively, for axial distance maps and 1.07 to 6.82 D, 0.79 to 1.77 D, and 1.23 to 3.03 D for tangential curvature maps. CONCLUSION: Results support the notion of a loss in repeatability for all three instruments when corneal irregularity is present, which reduces test-retest reliability.

Nonulcerating bacterial keratitis associated with soft and rigid contact lens wear.

OBJECTIVE: An unusual presentation of contact lens-related bacterial keratitis is that of epithelial nodular infiltrates and stromal inflammation without epithelial ulceration. The authors study the initial diagnosis, clinical features, causative organisms, and outcomes of corneal infections presenting in this manner. DESIGN: The study design was a 20-month retrospective chart review. PARTICIPANTS: Five patients with culture-proven bacterial keratitis who had predominantly nodular epithelial lesions were studied. RESULTS: Four infections were associated with soft contact lens wear and one with rigid lens wear. All patients had largely intact epithelium; typical gray-colored epithelial nodules, some with underlying anterior stromal haze; and diffuse, fine, cellular stromal inflammation. Two patients were referred with the tentative diagnosis of Acanthamoeba infection and two as contact lens-related sterile keratitis. Epithelial cultures from three cases yielded Serratia sp., one yielded Corynebacterium, and one Streptococcus pneumoniae. All responded to antibacterial medication; final corrected visual acuity in all cases was 20/30 or better. CONCLUSIONS: Bacterial infection associated with contact lens wear can be established within the corneal epithelium without initially producing an ulcer. A wide range of both gram-positive and gram-negative organisms can be involved. Early recognition and treatment appear to result in a favorable outcome.