Rebecca J McLean

Publications (11)112.25 Total impact

• Article: Reading Performance in Infantile Nystagmus.

  Niraj Barot, Rebecca J McLean, Irene Gottlob, Frank A Proudlock
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  ABSTRACT: OBJECTIVE: To characterize reading deficits in infantile nystagmus (IN), to determine optimal font sizes for reading in IN, and to investigate whether visual acuity (VA) and severity of nystagmus are good indicators of reading performance in IN. DESIGN: Prospective cross-sectional study. PARTICIPANTS AND CONTROLS: Seventy-one participants with IN (37 idiopathic, 34 with albinism) and 20 age-matched controls. METHODS: Reading performance was assessed using Radner reading charts and was compared with near logarithm of the minimum angle of resolution (logMAR) VA, nystagmus intensity, and foveation characteristics as quantified using eye movement recordings. MAIN OUTCOME MEASURES: Reading acuity (smallest readable font size), maximum reading speed, critical print size (font size below which reading is suboptimal), near logMAR VA, nystagmus intensity, and foveation characteristics (using the eXpanded Nystagmus Acuity Function). RESULTS: Using optimal reading conditions, maximum reading speeds were 18.8% slower in albinism and 14.7% slower in idiopathic IN patients compared with controls. Reading acuities were significantly worse (P<0.001) in IN patients compared with controls. Also, the range of font sizes over which reading speeds were less than the optimum were much larger in IN patients compared with controls (P<0.001). Reading acuity was correlated strongly to near VA (r2 = 0.74 albinism, r2 = 0.55 idiopathic), but was better than near VA in participants with poor VA. Near VA was a poor predictor of maximum reading speed. Nystagmus intensity and foveation were poor indicators of both reading acuity and maximum reading speed. CONCLUSIONS: Maximum reading speeds can be near normal in IN when optimal font sizes are provided, even in individuals with poor VA or intense nystagmus. However, reading performance in IN is acutely sensitive to font size limitations. Font sizes for optimal reading speeds in IN may be as much as 6 logMAR lines worse than the near VA. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
  Ophthalmology 02/2013; · 5.45 Impact Factor
• Article: Reading strategies in infantile nystagmus syndrome.

  Mervyn G Thomas, Irene Gottlob, Rebecca J McLean, Gail Maconachie, Anil Kumar, Frank A Proudlock
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  ABSTRACT: The adaptive strategies adopted by individuals with infantile nystagmus syndrome (INS) during reading are not clearly understood. Eye movement recordings were used to identify ocular motor strategies used by patients with INS during reading. Eye movements were recorded at 500 Hz in 25 volunteers with INS and 7 controls when reading paragraphs of text centered at horizontal gaze angles of -20°, -10°, 0°, 10°, and 20°. At each location, reading speeds were measured, along with logMAR visual acuity and nystagmus during gaze-holding. Adaptive strategies were identified from slow and quick-phase patterns in the nystagmus waveform. Median reading speeds were 204.3 words per minute in individuals with INS and 273.6 words per minute in controls. Adaptive strategies included (1) suppression of corrective quick phases allowing involuntary slow phases to achieve the desired goal, (2) voluntarily changing the character of the involuntary slow phases using quick phases, and (3) correction of involuntary slow phases using quick phases. Several individuals with INS read more rapidly than healthy control volunteers. These findings demonstrate that volunteers with INS learn to manipulate their nystagmus using a range of strategies to acquire visual information from the text. These strategies include taking advantage of the stereotypical and periodic nature of involuntary eye movements to allow the involuntary eye movements to achieve the desired goal. The versatility of these adaptations yields reading speeds in those with nystagmus that are often much better than might be expected, given the degree of foveal and ocular motor deficits.
  Investigative ophthalmology & visual science 08/2011; 52(11):8156-65. · 3.43 Impact Factor
• Article: The clinical and molecular genetic features of idiopathic infantile periodic alternating nystagmus.

  Mervyn G Thomas, Moira Crosier, Susan Lindsay, Anil Kumar, Shery Thomas, Masasuke Araki, Chris J Talbot, Rebecca J McLean, Mylvaganam Surendran, Katie Taylor, Bart P Leroy, Anthony T Moore, David G Hunter, Richard W Hertle, Patrick Tarpey, Andrea Langmann, Susanne Lindner, Martina Brandner, Irene Gottlob
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  ABSTRACT: Periodic alternating nystagmus consists of involuntary oscillations of the eyes with cyclical changes of nystagmus direction. It can occur during infancy (e.g. idiopathic infantile periodic alternating nystagmus) or later in life. Acquired forms are often associated with cerebellar dysfunction arising due to instability of the optokinetic-vestibular systems. Idiopathic infantile periodic alternating nystagmus can be familial or occur in isolation; however, very little is known about the clinical characteristics, genetic aetiology and neural substrates involved. Five loci (NYS1-5) have been identified for idiopathic infantile nystagmus; three are autosomal (NYS2, NYS3 and NYS4) and two are X-chromosomal (NYS1 and NYS5). We previously identified the FRMD7 gene on chromosome Xq26 (NYS1 locus); mutations of FRMD7 are causative of idiopathic infantile nystagmus influencing neuronal outgrowth and development. It is unclear whether the periodic alternating nystagmus phenotype is linked to NYS1, NYS5 (Xp11.4-p11.3) or a separate locus. From a cohort of 31 X-linked families and 14 singletons (70 patients) with idiopathic infantile nystagmus we identified 10 families and one singleton (21 patients) with periodic alternating nystagmus of which we describe clinical phenotype, genetic aetiology and neural substrates involved. Periodic alternating nystagmus was not detected clinically but only on eye movement recordings. The cycle duration varied from 90 to 280 s. Optokinetic reflex was not detectable horizontally. Mutations of the FRMD7 gene were found in all 10 families and the singleton (including three novel mutations). Periodic alternating nystagmus was predominantly associated with missense mutations within the FERM domain. There was significant sibship clustering of the phenotype although in some families not all affected members had periodic alternating nystagmus. In situ hybridization studies during mid-late human embryonic stages in normal tissue showed restricted FRMD7 expression in neuronal tissue with strong hybridization signals within the afferent arms of the vestibulo-ocular reflex consisting of the otic vesicle, cranial nerve VIII and vestibular ganglia. Similarly within the afferent arm of the optokinetic reflex we showed expression in the developing neural retina and ventricular zone of the optic stalk. Strong FRMD7 expression was seen in rhombomeres 1 to 4, which give rise to the cerebellum and the common integrator site for both these reflexes (vestibular nuclei). Based on the expression and phenotypic data, we hypothesize that periodic alternating nystagmus arises from instability of the optokinetic-vestibular systems. This study shows for the first time that mutations in FRMD7 can cause idiopathic infantile periodic alternating nystagmus and may affect neuronal circuits that have been implicated in acquired forms.
  Brain 02/2011; 134(Pt 3):892-902. · 9.46 Impact Factor
• Article: Corrigendum: Mutations in FRMD7, a newly identified member of the FERM family, cause X-linked idiopathic congenital nystagmus.

  Patrick Tarpey, Shery Thomas, Nagini Sarvananthan, Uma Mallya, Steven Lisgo, Chris J Talbot, Eryl O Roberts, Musarat Awan, Mylvaganam Surendran, Rebecca J McLean, [......], Sarah O'Meara, Adrian Parker, Claire Stevens, Jon Teague, Richard Wooster, P Andrew Futreal, Richard C Trembath, Michael R Stratton, F Lucy Raymond, Irene Gottlob
  Nature Genetics 01/2011; 43(7):720. · 35.53 Impact Factor
• Article: Clinical and oculomotor characteristics of albinism compared to FRMD7 associated infantile nystagmus.

  Anil Kumar, Irene Gottlob, Rebecca J McLean, Shery Thomas, Mervyn G Thomas, Frank A Proudlock
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  ABSTRACT: Previous studies have found no difference between nystagmus characteristics associated with idiopathic infantile nystagmus (IIN) and that associated with albinism. The present aim is to compare the oculomotor characteristics and other associated clinical features of albinism and a genetically homogenous group of IIN volunteers where the nystagmus is associated with FRMD7 mutations. Oculomotor characteristics and related clinical features between albinism (n = 52) and idiopathic nystagmus associated with FRMD7 mutations (FRMD7-IIN, n = 83) were compared. The nystagmus characteristics compared included amplitude, frequency, intensity of nystagmus, foveation characteristics, and waveform type. Other clinical features compared were strabismus, stereopsis and anomalous head posture. The FRMD7-IIN group contained a higher proportion of pendular waveform types compared with the albinism group (P < 0.0001). Nystagmus frequency was significantly lower in albinos (mean = 3.3 Hz, SD = 0.13 Hz) compared with the FRMD7-IIN group (mean = 4.3 Hz, SD = 0.18 Hz) (F = 14.5, P < 0.0001). Strabismus and anomalous head posture was seen in higher proportions in the albinism group, and stereopsis was worse compared with the FRMD7-IIN group (P ≪ 0.0001). Differences in nystagmus characteristics associated with albinism and those associated with FRMD7 mutations leading to IIN are described for the first-time. These findings may provide useful information in the future elucidation of mechanisms underlying the nystagmus associated with albinism and idiopathic infantile nystagmus.
  Investigative ophthalmology & visual science 01/2011; 52(5):2306-13. · 3.43 Impact Factor
• Article: Vertical optokinetic nystagmus in Parkinson's disease

  Christopher M. Knapp MD, Irene Gottlob MD, Rebecca J. McLean MD, Yusuf A. Rajabally MD, Richard J. Abbott MD, Suzanne Rafelt BSc, Frank A. Proudlock PhD, Christopher M. Knapp, Irene Gottlob, Rebecca J. McLean, Yusuf A. Rajabally, Richard J. Abbott, Suzanne Rafelt, Frank A. Proudlock
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  ABSTRACT: Parkinson's disease (PD) is associated with a number of oculomotor deficits; however, little is known about changes in vertical optokinetic nystagmus (OKN) associated with PD. We recorded eye movements in 14 PD patients and 14 age-matched controls in response to large field OKN stimulation using stimulus velocities of 20°/second and 40°/second. We compared asymmetry of horizontal and vertical responses in the two groups. We found vertical OKN to be strongly asymmetric in PD with reduced gains for downward-moving stimuli. This asymmetry was significantly greater than that recorded in control volunteers. We postulate that this could result from an abnormal pursuit/early OKN system in PD leading to greater influence of the delayed OKN system. © 2009 Movement Disorder Society
  Movement Disorders 07/2009; 24(10):1533 - 1538. · 4.51 Impact Factor
• Article: Vertical optokinetic nystagmus in Parkinson's disease.

  Christopher M Knapp, Irene Gottlob, Rebecca J McLean, Yusuf A Rajabally, Richard J Abbott, Suzanne Rafelt, Frank A Proudlock
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  ABSTRACT: Parkinson's disease (PD) is associated with a number of oculomotor deficits; however, little is known about changes in vertical optokinetic nystagmus (OKN) associated with PD. We recorded eye movements in 14 PD patients and 14 age-matched controls in response to large field OKN stimulation using stimulus velocities of 20 degrees /second and 40 degrees /second. We compared asymmetry of horizontal and vertical responses in the two groups. We found vertical OKN to be strongly asymmetric in PD with reduced gains for downward-moving stimuli. This asymmetry was significantly greater than that recorded in control volunteers. We postulate that this could result from an abnormal pursuit/early OKN system in PD leading to greater influence of the delayed OKN system.
  Movement Disorders 07/2009; 24(10):1533-8. · 4.51 Impact Factor
• Article: The prevalence of nystagmus: the Leicestershire nystagmus survey.

  Nagini Sarvananthan, Mylvaganam Surendran, Eryl O Roberts, Sunila Jain, Shery Thomas, Nitant Shah, Frank A Proudlock, John R Thompson, Rebecca J McLean, Christopher Degg, Geoffrey Woodruff, Irene Gottlob
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  ABSTRACT: Nystagmus, which can be infantile (congenital) or acquired, affects all ages. The prevalence of nystagmus in the general population is unknown. New genetic research and therapeutic modalities are emerging. Previous estimates have been based on wider ophthalmic epidemiologic studies within specific occupational or age groups. The authors carried out the first epidemiologic study to specifically establish the prevalence of nystagmus in Leicestershire and Rutland in the United Kingdom. Three independent data sources identified persons with nystagmus from the hospital and community. The first was a hospital-based questionnaire and clinical survey (n = 238). The visually impaired services (n = 414) and education services (n = 193) in Leicestershire provided the second and third separately obtained community-based sources of information. Capture-recapture statistical analysis was used to estimate prevalence. The prevalence of nystagmus in the general population was estimated to be 24.0 per 10,000 population (95% confidence interval [CI], +/-5.3). The most common forms of nystagmus were neurologic nystagmus (6.8 per 10,000 population; 95% CI, +/-4.6), nystagmus associated with low vision such as congenital cataracts (4.2 per 10,000; 95% CI, +/-1.2), and nystagmus associated with retinal diseases such as achromatopsia (3.4 per 10,000 population; 95% CI, +/-2.1). Within ethnic groups, nystagmus was significantly more common in the white European population than in the Asian (Indian, Pakistani, other Asian backgrounds) population (P = 0.004). The findings suggest that nystagmus is more common in the general population than previously thought. This may be of significance in resource allocation and health care planning.
  Investigative ophthalmology & visual science 06/2009; 50(11):5201-6. · 3.43 Impact Factor
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  Available from: arvo.org

  Article: Effect of distance upon horizontal and vertical look and stare OKN.

  Christopher M Knapp, Irene Gottlob, Rebecca J McLean, Suzzane Rafelt, Frank A Proudlock
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  ABSTRACT: Previous reports suggest that distance influences horizontal stare OKN gains; however, the effect of distance on vertical OKN and look OKN is unknown. Horizontal and vertical look and stare OKN gains were recorded in 16 healthy volunteers (velocity 38.4 degrees /s) at three distances (0.3 m, 1 m, and 2.5 m) and two different stimulus sizes. Asymmetry of responses and correlation of gains in different directions were compared. Measurements at near were compared with and without glasses. Distance did not significantly affect horizontal look and stare OKN or vertical look OKN, however, downward stare OKN gains were reduced at greater distances (p = 0.002). Mean downward stare OKN gains recorded in each individual were strongly correlated to leftward and rightward gains but not upward gains. In contrast, upward OKN gains were not correlated to gains in leftward, rightward, or downward directions. Downward stare OKN responses are significantly sensitive to the effects of distance, whereas stare OKN in other directions and look OKN responses in all directions are not. Individual mean downward stare OKN gains are more closely related to horizontal responses rather than upward responses. This suggests that the downward OKN system is more functionally related to the horizontal system rather than the upward OKN system.
  Journal of Vision 01/2009; 9(12):23.1-9. · 3.38 Impact Factor
• Article: Horizontal and vertical look and stare optokinetic nystagmus symmetry in healthy adult volunteers.

  Christopher M Knapp, Irene Gottlob, Rebecca J McLean, Frank A Proudlock
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  ABSTRACT: Look optokinetic nystagmus (OKN) consists of voluntary tracking of details in a moving visual field, whereas stare OKN is reflexive and consists of shorter slow phases of lower gain. Horizontal OKN is symmetrical in healthy adults, whereas symmetry of vertical OKN is controversial. Horizontal and vertical look and stare OKN symmetry was measured, and the consistency of individual asymmetries and the effect of varying stimulus conditions were investigated. Horizontal and vertical look and stare OKN gains were recorded in 15 healthy volunteers (40 degrees /s) using new methods to delineate look and stare OKN. Responses with right and left eye viewing were compared to investigate consistency of individual OKN asymmetry. In a second experiment, the symmetry of stare OKN was measured in nine volunteers varying velocity (20 degrees /s and 40 degrees /s), contrast (50% and 100%), grating contrast profile (square or sine wave), and stimulus shape (full screen or circular vignetted). There was no horizontal or vertical asymmetry in look or stare OKN gain for all volunteers grouped together. However, individual vertical asymmetries were strongly correlated for left and right eye viewing (look: r = 0.77, P = 0.0008; stare: r = 0.75, P = 0.001) and for look and stare OKN (r = 0.66, P = 7.3 x 10(-5)) because of a strong correlation for downward moving stimuli (r = 0.73, P = 0.002). Horizontal and vertical asymmetries were not significantly affected by variations in stimulus parameter. Although no horizontal or vertical OKN asymmetries existed for volunteers grouped together, vertical OKN was characterized by idiosyncratic asymmetries that remained consistent for an individual. Look and stare OKN gain is strongly associated for downward moving stimuli.
  Investigative Ophthalmology &amp Visual Science 03/2008; 49(2):581-8. · 3.60 Impact Factor
• Article: Mutations in FRMD7, a newly identified member of the FERM family, cause X-linked idiopathic congenital nystagmus.

  Patrick Tarpey, Shery Thomas, Nagini Sarvananthan, Uma Mallya, Steven Lisgo, Chris J Talbot, Eryl O Roberts, Musarat Awan, Mylvaganam Surendran, Rebecca J McLean, [......], Sarah O'Meara, Adrian Parker, Claire Stevens, Jon Teague, Richard Wooster, P Andrew Futreal, Richard C Trembath, Michael R Stratton, F Lucy Raymond, Irene Gottlob
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  ABSTRACT: Idiopathic congenital nystagmus is characterized by involuntary, periodic, predominantly horizontal oscillations of both eyes. We identified 22 mutations in FRMD7 in 26 families with X-linked idiopathic congenital nystagmus. Screening of 42 singleton cases of idiopathic congenital nystagmus (28 male, 14 females) yielded three mutations (7%). We found restricted expression of FRMD7 in human embryonic brain and developing neural retina, suggesting a specific role in the control of eye movement and gaze stability.
  Nature Genetics 12/2006; 38(11):1242-4. · 35.53 Impact Factor