|Year : 2020 | Volume
| Issue : 1 | Page : 94-96
Department of Ophthalmology, GMC, Thrissur, Kerala, India
|Date of Submission||24-Feb-2020|
|Date of Acceptance||24-Feb-2020|
|Date of Web Publication||17-Apr-2020|
Dr. Deepthi John
Department of Ophthalmology, GMC, Thrissur, Kerala
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
John D. Journal Review. Kerala J Ophthalmol 2020;32:94-6
| Analysis of Macular, Foveal, and Retinal Nerve Fiber Layer Thickness in Children With Unilateral Anisometropic Amblyopia and Their Changes Following Occlusion Therapy|| |
Kavitha V, Heralgi MM, Harishkumar PD, Harogoppa S, Shivaswamy HM, Geetha H. Analysis of macular, foveal, and retinal nerve fiber layer thickness in children with unilateral anisometropic amblyopia and their changes following occlusion therapy. Indian J Ophthalmol 2019;67:1016-22.
Amblyopia is defined as decrease of visual acuity in one eye when caused by abnormal binocular interaction or occurring in one or both eyes as a result of pattern vision deprivation during visual immaturity, for which no cause can be detected during the physical examination of the eye (s) and which in appropriate cases is reversible by therapeutic measures. Occlusion therapy has long been the mainstay of amblyopia treatment. Various studies are available documenting changes in macular thickness (MT), foveal thickness (FT), and retinal nerve fiber layer thickness (RNFLT) in amblyopic eyes. The purpose of this study was to analyze the structural changes in the retina (MT, FT, and RNFLT) in unilateral anisometropic amblyopic eyes and compare the same with the normal fellow eyes and the normal eyes of normal children and also to understand the same following occlusion therapy.
This was a prospective, interventional, comparative, longitudinal study carried out at a tertiary care eye hospital in South India between 2015 and 2017. Sixty children between 5 and 18 years were divided into two groups: Group 1 comprising thirty children with unilateral anisometropic amblyopic eyes and normal fellow eyes (nonamblyopic eyes) (difference in best-corrected visual acuity (BCVA) of ≥0.2 Logarithm of the Minimum Angle of Resolution (LogMAR) between two eyes); Group 2 included the normal eyes of thirty normal children. Children with previous history of spectacle wear/occlusion therapy/ocular surgery, refractive error correction >6 diopter spherical power and 3 diopter cylindrical power, presence of strabismus/nystagmus/hearing impairment/developmental delay, not compliant for spectacle wear and/or occlusion therapy, children who had poor fixation cooperation for spectral-domain optical coherence tomography (SD OCT) test, due to poor vision or lower age, and children who have come for less than three follow-ups were excluded from the study.
Detailed history, uncorrected visual acuity, and BCVA for distance and near vision were recorded by a single person. All tests to rule out strabismus were done. Intraocular pressure was measured using noncontact tonometry wherever possible. Fundus examination and cycloplegic refraction using appropriate drug according to age were carried out in all children. Other visual function tests such as color vision, contrast sensitivity, visual fields, and electrophysiology tests were recorded wherever it was required and possible. Detailed ophthalmological examination both anterior and posterior segment was carried out in all children. OCT examinations were performed using a SD OCT by the same operator through dilated pupils of at least 5 mm in diameter. “Fast RNFL map protocol” along with the “MT Map” was carried out. MT and FT were measured. In RNFLT measurement, total RNFL thickness was taken in the study. All findings were recorded for both the groups. The average of the right eye and left eye values was taken for all the parameters in Group 2. One month after the first visit (postspectacle wear), amblyopic children (Group 1) were asked to patch the normal fellow eye for 4 h per day and perform near activities such as reading, writing, drawing, mobile games, and computer work. Parents were insisted upon maintaining a diary regarding the same to check for compliance. Group 1 children were followed up with BCVA, MT, FT, and RNFLT at 3, 6, 9, and 12 months along with patch diary for children's compliance. Data were analyzed.
At the first visit, the difference in mean BCVA, MT, and FT between amblyopic eyes and normal eyes of normal group was statistically significant (P < 0.001). Similarly, the difference between amblyopic eyes and nonamblyopic eyes was statistically significant (P < 0.001). However, the difference in the mean RNFLT between amblyopic eyes and normal eyes and nonamblyopic eyes was statistically not significant. On analyzing the effectiveness of occlusion therapy on BCVA, MT, FT, and RNFLT at 3, 6, 9, and 12 months, an improvement in BCVA was seen in all patients following occlusion therapy at the end of 1 year. A weak-negative correlation between change in MT amblyopic eye and change in BCVA amblyopic eye was noted. There is also a weak-negative correlation between change in FT amblyopic eye and change in BCVA amblyopic eye.
Following occlusion therapy, the mean BCVA change was the greatest in the hypermetropic group (five children) which is revealed by the maximum change in FT, although least change was seen on MT. Univariate linear regression analysis showed baseline BCVA and baseline MT values to have statistically significant association with change in MT. Multivariate linear regression analysis showed baseline BCVA to be negatively associated with change in MT and baseline MT to be positively associated with change in MT.
Independent association between various factors such as age, gender, and type of refractive error and severity of refractive error could not be assessed due to small sample size. Hence, it is a limitation of the study.
In conclusion, MT and FT which were more in amblyopic eyes as compared to the normal fellow eyes and the normal eyes of normal children, decreased with improvement in BCVA after occlusion therapy. However, there was no difference in RNFLT between amblyopic eyes and the normal fellow eyes and the normal eyes of normal children before and after occlusion therapy. Hence, it is hypothesized that occlusion therapy can help in restoring the process of postnatal reduction of ganglion cells as evidenced by the reduction in MT and FT on OCT.
| Factors Affecting Generalization of Ocular Myasthenia Gravis in Patients With Positive Acetylcholine Receptor Antibody|| |
Apinyawasisuk S, Chongpison Y, Thitisaksakul C, Sariyakosol S. Factors affecting generalization of Ocular Myasthenia Gravis in patients with positive acetylcholine receptor antibody. Am J Ophthalmol 2020;209:10-17.
Ocular myasthenia gravis (OMG) is an autoimmune disorder characterized by fatigable weakness of extraocular muscles, levator palpebrae, and orbicularis oculi, resulting in fatigable ptosis and binocular diplopia. Approximately 30%–80% of patients with OMG experience a conversion to generalized myasthenia gravis (GMG) within 2 years. These patients not only have ptosis and diplopia but also limb weakness, bulbar symptoms, or even respiratory failure. Previous studies reported that risk factors of conversion included being female, having older age of onset of OMG, seropositivity to acetylcholine receptor antibody (AchR Ab), higher levels of seropositivity to AchR Ab, presence of autoimmune disorders, thymic hyperplasia, thymoma, and single ocular symptom (having either isolated ptosis or diplopia). Protective factors included longer duration of remaining OMG.
The purpose of this study was to evaluate the risk and protective factors of having a conversion to GMG, determine time to conversion, and assess factors influencing the time to conversion in patients with AchR Ab–seropositive OMG. It was hypothesized that patient's characteristics and health-related behavior, OMG initial clinical presentation, and medications received might affect the conversion.
This was a retrospective cohort study of patients with OMG who had positive AchR Ab. Patients were selected from the database of Neuroscience Laboratory, Thai Red Cross Emerging Infectious Disease Health Science Center, King Chulalongkorn Memorial Hospital. The charts of all patients who were aged 18 years or older and had positive AchR Ab test during July 2009 and December 2016 were retrospectively reviewed. Patients who first presented with GMG, were unable to identify the time of onset of OMG or GMG, were unable to provide the information about previous treatments before the onset of GMG, and had incomplete or lost medical records were excluded from the study.
A diagnosis of OMG, made based on the presence of fluctuating ptosis and/or diplopia and positive AchR Ab test, was reviewed. The AchR Ab serology test was performed using enzyme-linked immunosorbent assay. Demographic and clinical characteristics were obtained from medical records. Demographic data included sex and date of birth. GMG diagnosis was determined by experienced neurologists based on the signs and symptoms of generalization (i.e. swallowing difficulty, altered speaking, chewing problem, limited facial expression, proximal muscle weakness, fatigue, and respiratory failure).
Risk factors evaluated were sex, history of smoking, status of autoimmune disease, use of pyridostigmine or immunosuppressive agents (e.g. systemic corticosteroids or other immunosuppressive agents) before GMG conversion, and status of thymic abnormality.
A total of 184 patients had positive AchR Ab test result during the study period. After excluding patients who did not fit the inclusion criteria, 71 patients with complete data were included in analyses. Among the analysis set (N¼71), 35 OMG patients remained without change toward the end of the study (remained OMG group) and 36 patients experienced a conversion to GMG (GMG group). The median duration of follow-up was 4.91 years (interquartile range [IQR]: 2.98, 6) in the remained OMG group and 0.78 years (IQR: 0.18, 2.47) in the GMG group.
Over 258 patient-years of follow-up, 36 patients developed GMG. The overall incidence of GMG was 14 per 100 patient-years. The median time of conversion from OMG to GMG in all patients was 4.97 years. Female sex, history of smoking, and presence of thymic abnormalities were associated with shorter median conversion time (2.94, 1.85, and 1.25 years, respectively) and higher probability of conversion, whereas patients who received immunosuppressive agents and pyridostigmine had longer median conversion time (12.49 years for both groups) and lower probability of conversion at 2, 4, and 6 years.
This study is the first to show that smoking is a risk factor for a conversion to GMG. This might be explained by increased autoimmune activities through the recruitment of various types of immune cells and inflammatory cytokines induced by smoking as seen in many autoimmune disorder models. An alternative possible explanation is systemic AchR desensitization caused by long contact of blood nicotine to the whole-body AchR. Myasthenia patients should be recommended to stop smoking to reduce the chance of conversion to GMG and improve both ocular and systemic symptoms. In this study, it was found that pyridostigmine use was associated with lower rates of conversion to GMG. Pyridostigmine may provide immunomodulatory effects that prevent the conversion of OMG to GMG through a cholinergic anti-inflammatory pathway.
The strength of this study is that only definite myasthenia gravis patients diagnosed by positive AchR Ab were included. On the other hand, the results from this study might not be generalizable to AchR Ab–seronegative myasthenia gravis, which is one of the limitations of this study. The other potential limitations include the small number of participants and missing data from old medical records.
In conclusion, pyridostigmine, currently used as a symptomatic treatment of OMG and immunosuppressive agents, showed a protective effect from conversion to GMG, and smoking, in addition to the presence of thymic abnormalities and female gender, may accelerate conversion to GMG.
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