Assessment of a Clinical Test for Detection of Alteration in Visual Perception Due to Astigmatism.

Purpose: Astigmatism blurs the retinal image of a circular spot along a particular orientation rendering it an elliptical shape. Astigmatic patients demonstrate adaptation to residual astigmatic blur that may affect their discrimination between oval and circular targets. The Wilkins Egg and Ball Test (WEBT) was created to detect altered visual perception due to residual astigmatic blur by discriminating a circle within a row of oval elements. This prospective, cross-sectional study examined the utility of WEBT in detecting uncorrected residual astigmatism on the perception of form symmetry in astigmatic and keratoconic participants as well as normal participants with induced astigmatism at four primary meridians. Methods: The mean search time (sT) and number of errors (noE) of 33 non-astigmatic controls (mean age: 24±5, range: 18-43, 6 males), 23 astigmatic participants (mean age: 36±12, range: 18-43, 6 males) and 13 keratoconic participants (N=22 eyes, mean age: 36±12, range: 18-58, 6 males) were measured under baseline, and 2.00 DC induced cylinder at four primary meridians, and for uncorrected, spherical-correction only, and fully corrected conditions, respectively. Mean sT and noE were converted to Z-scores, combined for each condition, and compared using repeated measures ANOVA with post-hoc analysis. Results: Combined Z-scores for the controls were significantly worse (p<0.001) for all induced cylinder conditions. The induced 180° condition was significantly better than 45° and 90° conditions (p=0.04), but not the 135° condition. For both astigmatic and keratoconic cohorts, Z-scores of the uncorrected condition were significantly worse than the fully corrected condition (both p<0.01), but the fully corrected and spherical-only conditions did not differ significantly (p=0.06 and p=0.05, respectively). Conclusion: In accommodating young adults, WEBT detected altered visual perception due to overall blur, and moderate-high amounts of uncorrected induced astigmatism and keratoconus, but is not useful as a tool for detection of altered visual perception due to small residual astigmatic blur.

Refractive error of canine cataract patients following implantation with three types of intraocular lenses.

OBJECTIVE: To evaluate refractive state outcomes following phacoemulsification and implantation of 3 different intraocular lenses (IOLs). ANIMALS: A prospective, randomized, controlled study was conducted on 43 client-owned dogs undergoing phacoemulsification with IOL implantation. METHODS: Eyes were randomized to receive either an-vision Fo-X (n = 26), an-vision MD8 (18), or I-MED I-LENS (24) IOL. Refraction was measured 1 week, 1 month, and 3 months postoperatively using streak retinoscopy by 2 examiners masked to each other's results. RESULTS: Postoperative refractive outcomes were highly correlated and not significantly different between 2 examiners for all time points (r = 0.97, 0.98, and 1.00; P = .76, .94, and .98, respectively). One week postoperatively, the refractive errors (mean ± SD) for Fo-X, MD8, and I-LENS were -0.14 ± 2.02 diopters (D), 0.97 ± 2.01 D, and 0.15 ± 2.55 D, respectively. One month postoperatively, the refractive errors were 0.35 ± 2.04 D, 0.06 ± 2.41 D, and -0.82 ± 2.20 D, respectively. Three months postoperatively, the refractive errors were -0.16 ± 2.67 D, 1.60 ± 2.99 D, and 0.59 ± 1.51 D, respectively. There were no significant differences in refractive error outcomes between Fo-X, MD8, and I-LENS at 1 week, 1 month, and 3 months postoperatively (P = .16; F(df=2,66)- = 1.89). However, the Fo-X was the only IOL to yield nearly emmetropic outcomes (±0.50 D) at all 3 time points. CLINICAL RELEVANCE: The postoperative refractive states of dogs were not statistically different when comparing 3 types of IOLs at 3 postoperative time points, though the Fo-X was the only IOL to yield nearly emmetropic outcomes at all 3 time points.

Contact lens wear and follow-up and its association with signs and symptoms of meibomian gland dysfunction.

INTRODUCTION: This study investigated the equivocal association between contact lens (CL) wear and meibomian gland dysfunction (MGD) by comparing the morphological, functional and subjective outcomes of CL wearers versus control, non-CL wearers. CL wearers were examined as two cohorts based on the annual attendance of follow-up visits (FLU-attended these visits, whereas non-FLU did not). METHODS: Habitual logMAR visual acuity, invasive and non-invasive tear break-up time, Schirmer test, Efron grading scales, meibum quality score (MQS), meibum expressibility score (MES), meibomian gland (MG) loss, lid margin abnormalities and subjective dry eye (DE) symptoms were assessed. RESULTS: Of the 128 participants, 31 were in the FLU cohort, 43 were in the non-FLU cohort and 54 were controls (mean ages: 22.2 ± 3.1, 23.0 ± 4.6 and 22.3 ± 3.5, respectively). Non-FLU CL wearers had more symptoms than controls (3.7 ± 2.4 vs. 2.3 ± 2.1, p < 0.01). Morphologically, FLU (16.9 ± 8.8%, p = 0.02) and non-FLU (18.6 ± 11.3%, p = 0.001) had more MG loss than controls (11.2 ± 6.8%). Functionally, FLU (0.6 ± 0.7, p = 0.01) and non-FLU (0.8 ± 0.9, p = 0.001) had worse MES than controls (0.2 ± 0.5). FLU and non-FLU were both associated with corneal staining (odds ratio [OR] = 3.42, 95% CI: 1.16-10.11, p = 0.03 and OR = 5.23, 95% CI: 1.89-14.48, p = 0.001, respectively) and MG loss (OR = 10.47, 95% CI: 1.14-96.29, p = 0.04 and OR = 16.63, 95% CI: 1.96-140.86, p = 0.01, respectively). Non-FLU CL wear was also associated with abnormal MQS (OR = 12.87, 95% CI: 1.12-148.41, p = 0.04), conjunctival staining (OR = 12.18, 95% CI: 3.66-40.51, p < 0.001) and lid margin telangiectasia (OR = 3.78, 95% CI: 1.55-9.21, p = 0.003). MGD was three times more prevalent in CL wearers (12%) than in controls (4%). CONCLUSIONS: Both CL-wearing cohorts demonstrated significantly more MG abnormalities than controls though the difference was not clinically significant. Non-FLU CL wearers had more DE symptoms. Non-FLU CL wear is an independent predictor for more abnormalities than FLU CL wear, emphasising the importance of follow-ups.

Validation of the DYOP visual acuity test

Purpose: The dynamic optotype (DYOP) visual acuity (VA) test is based on motion detection rather than element resolution and has been proposed for routine clinical assessment. This investigation examined the validity, inter- and intra-session repeatability and subjective preference for the DYOP versus a static letter chart and examined its utility in detecting astigmatic defocus. Methods: VA of 103 participants was measured three times with the letter and DYOP charts and repeated within two weeks in 75 participants who also rated their subjective experience. The VA of 29 participants was measured using DYOP, letter, Landolt C, and Tumbling E charts, with habitual correction and astigmatism induced with +1.00, +2.00 or +3.00 cylinders at 45, 60, 90 and 180°. Results: The charts differed by a mean of 0.02 logMAR, with 81% of the measurements within one line of acuity. Inter-session, intraclass correlation coefficients, within-subject SD and repeatability were 0.03 logMAR, 0.95, 0.11 and 0.30 versus 0.01 logMAR, 0.92, 0.15 and 0.42 for the DYOP and letter charts, respectively. The DYOP was significantly more frustrating (1.79 vs.1.36), with 59% preferring the letter chart. The DYOP was least affected by induced astigmatism. Conclusions: The DYOP and letter charts differed significantly in their mean values with wide limits of agreement. DYOP had better within-subject SD and narrower limits of agreement between sessions, though clinically insignificant, and performed significantly worse for the detection of uncorrected astigmatism. Thus, it is difficult to recommend this test for the clinical determination of refractive error. (AU)

A retinoscopic survey of donkeys and goats.

PURPOSE: Assess the refractive states of donkeys and goats. METHODS: Forty-two donkeys and 28 goats were enrolled. The mean ± SD ages were 7.68 ± 7.33 years for donkeys and 4.26 ± 2.33 years for goats. Seven donkeys and one goat were <6 months old. Retinoscopy was performed in alert animals, following cycloplegia in goats but not in donkeys. Normality was determined using the Kolmogorov-Smirnov test. The two primary meridians and two eyes were compared using Pearson's correlation and paired Student's t-tests. The association between refractive states and age was examined using one-way ANOVA in donkeys and a paired Student's t-test in goats. One-sample t-tests were conducted to assess if the refractive error distributions were significantly different from "0". RESULTS: The mean ± SD spherical equivalent (SE) refractive errors of the right and left donkey eyes were -0.80 ± 1.03 D and -0.35 ± 0.95 D, respectively. The majority (86%) of the donkeys had an astigmatic refraction and eight (19%) had anisometropia. The mean SE refractive errors of the right and left goat eyes were -0.15 ± 1.1 D and -0.18 ± 1.2 D, respectively. The majority (54%) of the goat eyes had an astigmatic refraction and five (18%) had anisometropia. The right and left eye SE refractive errors were positively correlated in both species (both p = .9). Age was not correlated with refractive error in both donkeys (p = .09) and goats (p = .6). CONCLUSIONS: Both goats and donkeys are emmetropic.

Topical review of the relationship between contact lens wear and meibomian gland dysfunction

Contact lens (CL) wearers often suffer from ocular discomfort, which leads to cessation of CL wear. About 30% to 50% of CL wearers complain of dry eye (DE) symptoms. Meibomian gland dysfunction (MGD) is considered the most common cause of evaporative DE. Numerous studies have investigated whether CL wear might affect the meibomian glands. This manuscript reviews studies examining the relationship between CL use and MGD. A PubMed database search was conducted for studies published between 1980-2021 with one or a combination of search terms related to “meibomian gland”, “meibomian gland dysfunction”, “contact lens”, and/or “dry eye”. Of the 115 papers reviewed, 22 articles were identified that examined the association between CL and MGD. Fifteen showed that CL wear affects the morphology and function of meibomian glands (MGs), while seven reported no significant impact of CL wear on MGs. This review provides an overview of these studies, emphasizing the diagnostic tests of MGD and conclusions. The review highlights the need for longitudinal prospective large cohort studies with control non- CL wearers to clarify the ambiguous relationship between MGD and CL wear, with special attention to varying CL material and wear times in order to identify the long-term impact of CLs on MG. (AU)

Topical review of the relationship between contact lens wear and meibomian gland dysfunction.

Contact lens (CL) wearers often suffer from ocular discomfort, which leads to cessation of CL wear. About 30% to 50% of CL wearers complain of dry eye (DE) symptoms. Meibomian gland dysfunction (MGD) is considered the most common cause of evaporative DE. Numerous studies have investigated whether CL wear might affect the meibomian glands. This manuscript reviews studies examining the relationship between CL use and MGD. A PubMed database search was conducted for studies published between 1980-2021 with one or a combination of search terms related to "meibomian gland", "meibomian gland dysfunction", "contact lens", and/or "dry eye". Of the 115 papers reviewed, 22 articles were identified that examined the association between CL and MGD. Fifteen showed that CL wear affects the morphology and function of meibomian glands (MGs), while seven reported no significant impact of CL wear on MGs. This review provides an overview of these studies, emphasizing the diagnostic tests of MGD and conclusions. The review highlights the need for longitudinal prospective large cohort studies with control non- CL wearers to clarify the ambiguous relationship between MGD and CL wear, with special attention to varying CL material and wear times in order to identify the long-term impact of CLs on MG.

Repeatability and reproducibility of Cobra HD fundus camera meibography in young adults with and without symptoms of dry eye.

PURPOSE: The inter-session repeatability (ISR), inter-examiner reproducibility (IER) and within-subject variability (WSV) of the Cobra HD fundus camera meibographer were examined in participants with and without dry eye symptoms. METHODS: Symptoms were determined based on Ocular Surface Disease Index scores (≥13 being considered symptomatic), and subgroups were compared using the Mann-Whitney U-test. Images of meibomian glands (MGs) from the upper and lower right eyelids were captured by two examiners on the same day (S1) to determine IER. One examiner repeated the measurements on a second day (S2) to obtain the ISR. ISR, IER and WSV were calculated using Friedman, correlation tests and Bland and Altman analyses with mean differences (md) and 95% confidence intervals (CIs), within-subject standard deviations (Sw) and intra-class correlation coefficients (ICC). RESULTS: The ISR experiment included 72 participants (mean age: 23 ± 5 years, range: 19-43, 36 symptomatic). Mean MG loss of the upper (S1: 13.5 ± 9.5%, S2: 12.8 ± 8.5%) and lower eyelids (S1: 7.5 ± 6.9%, S2: 7.3 ± 6.3%) was not significantly different between sessions for all participants, symptomatic and asymptomatic subgroups for both eyelids. The ISR Sw for the upper and lower eyelids was 1.3% and 1.0%; md was 0.7 ± 3.5% (CI:-6.25% to 7.62%) and 0.1 ± 2.1% (CI: -3.94% to 4.17%), respectively. The IER experiment included 74 participants (mean age: 23 ± 5 years, range: 19-43, 37 symptomatic). Mean MG loss of the upper (Examiner 1: 12.7 ± 8.2%, Examiner 2: 13.1 ± 8.0%) and lower eyelids (Examiner 1: 7.0 ± 6.2%, Examiner 2: 7.4 ± 6.2%) was not significantly different between examiners for all participants, symptomatic and asymptomatic subgroups for both eyelids. The IER ICC values were >0.86 for all conditions, Sw was 1.3% and 1.2%, with a md of -0.4 ± 3.2% (CI: -6.65% to 5.90%) and -0.4 ± 2.9% (CI: -6.15% to 5.31%), respectively. The WSV Sw values were <1.4%, and ICC values were >0.89 for both eyelids, examiners and experimental sessions. CONCLUSIONS: The Cobra HD fundus camera demonstrates good repeatability, reproducibility and low WSV, and is a reliable clinical instrument for meibography.

Validation of the DYOP visual acuity test.

PURPOSE: The dynamic optotype (DYOP) visual acuity (VA) test is based on motion detection rather than element resolution and has been proposed for routine clinical assessment. This investigation examined the validity, inter- and intra-session repeatability and subjective preference for the DYOP versus a static letter chart and examined its utility in detecting astigmatic defocus. METHODS: VA of 103 participants was measured three times with the letter and DYOP charts and repeated within two weeks in 75 participants who also rated their subjective experience. The VA of 29 participants was measured using DYOP, letter, Landolt C, and Tumbling E charts, with habitual correction and astigmatism induced with +1.00, +2.00 or +3.00 cylinders at 45, 60, 90 and 180°. RESULTS: The charts differed by a mean of 0.02 logMAR, with 81% of the measurements within one line of acuity. Inter-session, intraclass correlation coefficients, within-subject SD and repeatability were 0.03 logMAR, 0.95, 0.11 and 0.30 versus 0.01 logMAR, 0.92, 0.15 and 0.42 for the DYOP and letter charts, respectively. The DYOP was significantly more frustrating (1.79 vs.1.36), with 59% preferring the letter chart. The DYOP was least affected by induced astigmatism. CONCLUSIONS: The DYOP and letter charts differed significantly in their mean values with wide limits of agreement. DYOP had better within-subject SD and narrower limits of agreement between sessions, though clinically insignificant, and performed significantly worse for the detection of uncorrected astigmatism. Thus, it is difficult to recommend this test for the clinical determination of refractive error.

Convergence insufficiency: Review of clinical diagnostic signs

Convergence insufficiency (CI) is a common binocular vision (BV) disorder characterized by difficulty in maintaining motor fusion at near, which affects approximately 7.5 percent of the population. Diagnostic criteria for the disorder are inconsistent, ranging from one to many clinical signs. Methodology for clinical tests is inconsistent in measurement technique, visual targets, required repetitions, and normative values.This manuscript demonstrates the inconsistencies amongst published studies, and highlights the importance of consistent clinical diagnostic signs, measurement techniques, visual targets, and cut-off criteria. For each clinical sign, the recommended methodology for the procedure is described. Several studies do not take age into account when diagnosing CI in their cohorts. As such, the review emphasizes changes in diagnostic signs with age.This manuscript highlights the need for consistent and clear procedures and diagnostic criteria amongst clinicians and provides the basis for future studies in terms of diagnostic testing required for CI of varying age groups. (AU)

Convergence insufficiency: Review of clinical diagnostic signs.

Convergence insufficiency (CI) is a common binocular vision (BV) disorder characterized by difficulty in maintaining motor fusion at near, which affects approximately 7.5 percent of the population. Diagnostic criteria for the disorder are inconsistent, ranging from one to many clinical signs. Methodology for clinical tests is inconsistent in measurement technique, visual targets, required repetitions, and normative values. This manuscript demonstrates the inconsistencies amongst published studies, and highlights the importance of consistent clinical diagnostic signs, measurement techniques, visual targets, and cut-off criteria. For each clinical sign, the recommended methodology for the procedure is described. Several studies do not take age into account when diagnosing CI in their cohorts. As such, the review emphasizes changes in diagnostic signs with age. This manuscript highlights the need for consistent and clear procedures and diagnostic criteria amongst clinicians and provides the basis for future studies in terms of diagnostic testing required for CI of varying age groups.

Agreement and inter-session repeatability of manual and automatic interpupillary distance measurements

Background: Interpupillary distance (IPD) is important in developmental anatomy, genetics, design of optical instrumentation, ocular diagnostics, and optical prescribing. IPD frequently is measured on different days, and by either automatic pupillometers (physiological measurement) or manual ruler (anatomical measurement). Therefore, there is importance in the agreement and inter-session repeatability of manual and automatic IPD measurements.MethodsMonocular distance from the bridge of the nose and binocular distance and near binocular IPD were randomly measured, using a millimeter ruler and the Essilor Pupillon pupillometer. Gender effects were assessed using Wilcoxon and Mann-Whitney tests, respectively. Agreement was assessed using Spearman correlation and Bland-Altman (B&A) plots. Thirty additional participants were tested within 1–2 weeks to determine the inter-session repeatability.ResultsThe agreement study included 199 participants (mean age: 24.1 ± 5.0 range: 19−53, 58 male, 141 female) and the repeatability sub- study included 30 (mean age: 27.9 ± 4.5, range: 23–39, 6 male, 24 female). Males and females significantly differed in age (<2 year mean difference (md)) and IPD (monocular md: < 1 mm, binocular md: < 2 mm). Manual vs. automatic measurements were significantly different for all conditions (md: <1 mm for all) except for distance left eye male PD. There was no significant difference between the session for both methods.ConclusionsBinocular and monocular manual and automatic measurements were significantly different statistically, but not clinically. Distance binocular IPD was approximately 3 mm wider than near IPD. Male binocular IPD was approximately 2 mm wider than the female IPD. Both methods had good inter-session repeatability. (AU)

Agreement and inter-session repeatability of manual and automatic interpupillary distance measurements.

BACKGROUND: Interpupillary distance (IPD) is important in developmental anatomy, genetics, design of optical instrumentation, ocular diagnostics, and optical prescribing. IPD frequently is measured on different days, and by either automatic pupillometers (physiological measurement) or manual ruler (anatomical measurement). Therefore, there is importance in the agreement and inter-session repeatability of manual and automatic IPD measurements. METHODS: Monocular distance from the bridge of the nose and binocular distance and near binocular IPD were randomly measured, using a millimeter ruler and the Essilor Pupillon pupillometer. Gender effects were assessed using Wilcoxon and Mann-Whitney tests, respectively. Agreement was assessed using Spearman correlation and Bland-Altman (B&A) plots. Thirty additional participants were tested within 1-2 weeks to determine the inter-session repeatability. RESULTS: The agreement study included 199 participants (mean age: 24.1 ± 5.0 range: 19-53, 58 male, 141 female) and the repeatability sub- study included 30 (mean age: 27.9 ± 4.5, range: 23-39, 6 male, 24 female). Males and females significantly differed in age (<2 year mean difference (md)) and IPD (monocular md: < 1 mm, binocular md: < 2 mm). Manual vs. automatic measurements were significantly different for all conditions (md: <1 mm for all) except for distance left eye male PD. There was no significant difference between the session for both methods. CONCLUSIONS: Binocular and monocular manual and automatic measurements were significantly different statistically, but not clinically. Distance binocular IPD was approximately 3 mm wider than near IPD. Male binocular IPD was approximately 2 mm wider than the female IPD. Both methods had good inter-session repeatability.

Naturally-occurring myopia and loss of cone function in a sheep model of achromatopsia.

Achromatopsia is an inherited retinal disease characterized by loss of cone photoreceptor function. Day blind CNGA3 mutant Improved Awassi sheep provide a large animal model for achromatopsia. This study measured refractive error and axial length parameters of the eye in this model and evaluated chromatic pupillary light reflex (cPLR) testing as a potential screening test for loss of cone function. Twenty-one CNGA3 mutant, Improved Awassi, 12 control Afec-Assaf and 12 control breed-matched wild-type (WT) Awassi sheep were examined using streak retinoscopy and B-mode ocular ultrasonography. Four CNGA3 mutant and four Afec-Assaf control sheep underwent cPLR testing. Statistical tests showed that day-blind sheep are significantly more myopic than both Afec-Assaf and WT Awassi controls. Day-blind sheep had significantly longer vitreous axial length compared to WT Awassi (1.43 ± 0.13 and 1.23 ± 0.06 cm, respectively, p < 0.0002) and no response to bright red light compared to both controls. Lack of response to bright red light is consistent with cone dysfunction, demonstrating that cPLR can be used to diagnose day blindness in sheep. Day-blind sheep were found to exhibit myopia and increased vitreous chamber depth, providing a naturally occurring large animal model of myopia.

Synchronization of a Removable Optical Element with an Eye Tracker: Test Case for Heterophoria Measurement.

Purpose: Heterophoria describes the deviation of the optical axes in the absence of binocular fusion. Eye trackers (ET) can provide an objective assessment but are not broadly used clinically. We examined the feasibility of combining an infrared (IR) pass-filter, IR detector, and an off-the-shelf ET. The proposed setup was validated against the broadly used cover test (CT). Furthermore, the setup was used to examine whether testing conditions can affect the measurements. Methods: An IR detector was attached to a handheld IR-pass filter that blocks visible light to provide occlusion while passing IR light for eye tracking. The detector senses the IR illumination of the eye tracker, creating a recordable signal of the occluder position synchronized with eye positions acquired by the SMI Red250 tracker. The mean of three measurements of each condition, three versus ten seconds occlusion, the occluded eye, and ET versus CT results were compared using the Wilcoxon test, correlation and Bland and Altman plots. Differences between measurements that were within 2Δ were considered clinically insignificant. Results: Thirty normally-sighted subjects (mean age 24.50 ± 2.20, range 20-28) with heterophoria ranging between 14Δ exophoria and 4Δ esophoria were recruited. There was no significant difference between the occluded eyes. However, there was a difference between 3 and 10 seconds' cover duration. The CT data were more similar to the 10 seconds cover duration, although differences were less than the clinical resolution of 2Δ. Conclusions: An inexpensive off-the-shelf ET can be used to measure heterophoria with controlled testing parameters. Translational Relevance: Our study demonstrated a robust technique for synchronization of an optical element such as an IR cover, with an off-the-shelf commercial eye tracker. The synchronization of optical elements with eye tracking, which has been described here for heterophoria, can be adapted for other clinical measurements.

Analysis of Alphabet Patterns of Deviations Found in Patients Without Strabismus in Primary Position.

AIM: To detect alphabet patterns in a group of patients without strabismus and to determine whether they induced any convergence insufficiency type symptoms. METHODS: Data on subjective refraction, distance and near heterophoria, distance and near positive fusional vergence (BO), near point of convergence (NPC), measurements of upgaze and downgaze made 45° above and below the primary position with alternate cover test and a prism bar at a distance of 37.5 cm, were collected from participants of two clinics. Symptoms were assessed using the 15-item Convergence Insufficiency Symptoms Survey (CISS) to determine a symptom score. Association between alphabet patterns and the other variables was analyzed using parametric and non-parametric tests. RESULTS: Out of 122 patients, 14 were found to present an alphabet pattern. Defining a V pattern exophoria ≥15-prism dioptre or ≥10-prism dioptre deviation, three patients (2.5%) and 12 patients (9.8%) were identified, respectively. In addition, one case resembled an X pattern and another a diamond pattern. The refraction, distance and near heterophoria, positive fusional vergence and CISS scores were not significantly different in the participants with V pattern compared to those without V pattern. CONCLUSION: Alphabet patterns, especially V type, were demonstrated in approximately 11.5% of a sample of 122 non-strabismus patients. These alphabet patterns were found not to be associated with convergence insufficiency-like symptoms.

Reading speed of patients with infantile nystagmus for text in different orientations.

Two case studies in the literature report on patients with infantile nystagmus (IN) who preferred to read text that is oriented vertically rather than horizontally. The current study systematically evaluated the effect of text orientation (-60 to +90 deg with respect to horizontal) on reading speed in nine individuals with IN associated with albinism at Hadassah Academic College (HAC), seven individuals with IN at the University of Houston (UH), and a total of 17 normal control observers. Observers at HAC read 40-character passages of Hebrew text from standardized 2nd grade level reading material and observers at UH read MNRead acuity chart sentences. Letter size was two to six lines larger than each observer's measured visual acuity. In both individuals with IN and normal observers reading speed was fastest for horizontally oriented text and decreased for other orientations. However, reading speed decreased significantly more for non-horizontally orientated text in the observers with IN, compared to controls. In general, it is recommended that to achieve best reading performance patients with IN read horizontally oriented text.