Diagnostic value of visual evoked potentials for clinical diagnosis of multiple sclerosis.

PURPOSE: Prolonged latency of visual evoked potentials (VEP) has been used to identify clinically silent lesions in multiple sclerosis (MS) suspects. The objective of this study was to determine the reliability of VEP to predict the development of MS in MS suspects. METHODS: Retrospective hospital records of MS suspects were evaluated. VEP was analyzed together with subsequent diagnostic confirmation of MS by McDonald diagnostic criteria for MS-2005. RESULTS: MS developed in 12 of 35 patients (34 %) and 23 (66 %) failed to exhibit diagnostic characteristics. P100 latencies and interocular latency differences were longer in clinically definite multiple sclerosis (CDMS) than non-CDMS patients (p = 0.002, 0.001, respectively). All patients in the subsequent MS group had P100 latencies longer than102 ms, a mean of our MS-free subjects thus providing 100 % of sensitivity. No patient developed MS with a P100 latency <102 ms. Brain MRI lesions associated significantly with developing CDMS (p = 0.001). Predictability of developing CDMS was highest when criteria for P100 latency, interocular latency difference, and brain MRI lesions were combined. CONCLUSION: MS suspects with a P100 latency longer than mean of MS-free subjects are more likely to develop MS than those with lower values. VEP latency combined with MRI could improve the accuracy of MS prediction.

Visual prognostic value of ocular electrophysiology tests in corneal transplantation.

OBJECTIVE: To determine visual prognostic value of electrophysiologic tests in unilateral-eye-disease patients who underwent corneal transplantation. MATERIAL AND METHOD: Retrospective charts of the patients who underwent unilateral optical penetrating keratoplasty at Siriraj Hospital from September 2003-June 2009 were reviewed. The amplitude of a-wave and b-wave in dark-adapted bright flash ERG and the amplitude of major positivity (P2) in flash VEP were recorded and compared with the good fellow eye. Area under receiver operating characteristic curve (AUC) was used to determine the best predictor of good visual prognosis. Positive predictive value (PPV) and negative predictive value (NPV) were used to determine the accuracy of the tests. RESULTS: Thirty-nine patients were included. The present study showed that a-wave amplitude was a good predictor (AUC = 0.83). For a-wave amplitude that was equal to or more than 80% and P2 amplitude that was equal to or more than 67%, PPV was 95.65%. CONCLUSION: The a-wave amplitude and P2 amplitude predict good visual outcome most accurately when changing less than 20% and 33%, respectively, compared to the normal fellow eye.

Achromatopsia: the first case report in Thailand.

Achromatopsia, also known as rod mon-ochromacy, is a congenital and nonprogressive ocular disorder characterized by an absence of functional cone photoreceptors in the retina. Affected subjects usually present in infancy with photophobia, nystagmus, low visual acuity and inability to discriminate colors. Fundus examination is normal, but electroretinography demonstrates absent photopic (cone) responses and normal scotopic (rod) responses. Achromatopsia is rare in the general population and inherited as an autosomal recessive trait. The authors report the first case of achromatopsia in Thailand with complete electrophysiological findings and long-term follow-up (8 years).

Antimalarial-induced maculopathy: accuracy of Amsler grid as a diagnostic tool and risk factors.

OBJECTIVE: To determine the sensitivity, specificity, and agreement of Amsler grid (AG) in detecting antimalarial induced maculopathy (AM) compared to combination of dilated ocular examination and Humphrey visual field (HVF) 10-2 and to estimate the risk factors of AM. MATERIAL AND METHOD: 20 patients with AM and 20 patients with no AM were included between October 1, 2010 and June 30, 2011 in Siriraj Hospital, Thailand. Sensitivity, specificity and unweighted kappa were used to determine accuracy of AG. Logistic regression was used to explore risk factors associated with AM. RESULTS: The sensitivity and specificity of AG were 40% and 100%, respectively. The agreement of AG and HVF 10-2 was poor with kappa of 0.4. Creatinine clearance < 60 ml/min/1.73 m2 and bilateral macular abnormality were associated with AM at the same odds ratio of 8.9 (95% confidence interval: 1.3 to 61.2). CONCLUSION: AG may be used as an additional test between ocular evaluation visits providing the availability and low cost. Patients with renal impairment and bilateral macular abnormality are associated with AM.

A Pooled Assessment of Ocular Surface Disease After Switching from Preserved Prostaglandins to Tafluprost Across Six Countries in Asia.

Background: Preserved prostaglandin analogs (PGAs) have been linked to ocular surface disease (OSD). While the benefits of preservative-low (PL) or -free (PF) Tafluprost (Santen Inc., Japan) were reported in real-world studies in Western countries, this is the first study in Asia to assess the effectiveness and safety of switching from preserved PGA to PL or PF-Tafluprost. Methods: We conducted a meta-analysis on studies that included adults (>18 years of age) with a Corneal Fluorescein Staining Score (CFS) >1. These individuals had switched to PL or PF-tafluprost after using a preserved PGA therapy for at least 3 months for glaucoma and were identified from Santen's tafluprost study database. A total of six studies from South Korea, Philippines, Malaysia, Singapore, Thailand, Taiwan were pooled for analysis. Results: An intraocular pressure (IOP) reduction of 5.9% (0.91 mmHg) was seen in 265 patients. However, this result was not statistically significant (95% CI: -3.64, 1.81; Figure 1). Among 132 patients, a 47.9% reduction in the CFS (95% CI: -3.65, -1.91) was seen. Tear film break-up (n=183) significantly increased by 1.06 seconds (95% CI: 0.65, 1.47). In 88 patients, the bulbar conjunctiva score decreased by -0.46 (95% CI: -0.81, -0.10) and palpebral conjunctiva score decreased by -0.42 (95% CI: -0.67-0.17). One or more new adverse reactions were reported in 3% of the individuals after switching. Conclusion: Tafluprost IOP reduction is comparable to other PGAs, with significant improvements in the ocular surface and minimal adverse reactions which were already previously reported.

Ocular Surface Changes After Switching from Other Prostaglandins to Tafluprost and Preservative-Free Tafluprost in Glaucoma Patients.

PURPOSE: To study ocular surface disease (OSD) changes after switching from preserved prostaglandin analogues monotherapy to preserved tafluprost and preservative-free (PF) tafluprost in primary open-angle glaucoma patients. METHODS: Glaucoma patients treated with preserved prostaglandins (except tafluprost) monotherapy for at least 6 months, intraocular pressure (IOP) ≤22 mmHg, and diagnosed of OSD [≥1 criterion; tear break-up time (TBUT) ≤10 seconds, corneal fluorescein staining ≥grade 1] in both eyes were enrolled in a prospective, randomized, single-blinded study. All eligible patients were switched from preserved prostaglandin analogues monotherapy (latanoprost, bimatoprost, travoprost) to preserved tafluprost in one eye (group I) and PF-tafluprost in the other eye (group II) of the same patient by randomization. The symptoms of OSD were evaluated using the visual analogue scale, and lid inflammation, conjunctival hyperemia, TBUT, corneal fluorescein staining, and Schirmer I test were applied to assess the clinical signs. All parameters were evaluated before and then 6, 12, 24 weeks after switching the medications. RESULTS: Thirty patients (80% women; mean age: 61.2 ±11.5 years) were included. Baseline parameters were not different between the treatment groups. After switching therapies, TBUT was significantly increased in both groups (p = 0.002, p = 0.004, respectively); however, group II had better tear quality. Other symptoms and clinical signs of OSD were improved and IOP was controlled in both groups. CONCLUSION: Treatment with PF-tafluprost improves TBUT better than preserved tafluprost, suggesting that PF-tafluprost should be especially beneficial for patients with pre-existing OSD. Less or no preservative anti-glaucoma eye drops can restore and enhance the ocular surface in glaucoma patients.

Visual electrophysiology in congenital nystagmus with normal fundus.

OBJECTIVE: To identify the ophthalmic causes of congenital nystagmus with normal eye examination by visual electrophysiologic tests. MATERIAL AND METHOD: Medical records of patients who presented with nystagmus and no other neurological sign before 6 months of age with normal eye examination, between February 2004 and February 2005, were reviewed Complete ophthalmic examination and visual electrophysiologic tests were performed to identify the ophthalmic causes of congenital nystagmus. RESULTS: Thirty-four patients had met the criteria. Leber's congenital amaurosis was diagnosed in 13 patients (38.2%) by non-recordable electroretinography (ERG) and normal visual evoked potential (VEP). Idiopathic infantile nystagmus was diagnosed in 12 patients (35.3%) by normal ERG and VEP. Achromatopsia was diagnosed in 8 patients (23.5%) by flat retinal cone ERG but normal rod ERG and VEP. Rod-cone dystrophy was diagnosed in one patient (3%) by abnormal rod and cone ERG CONCLUSION: Visual electrophysiologic study is helpful to identify the ophthalmic causes of congenital nystagmus. Leber's congenital amaurosis is a common cause in congenital nystagmus.

Normative data of optic nerve head in Thai population by laser scanning tomography: Siriraj study.

OBJECTIVE: To study the normative values of topographic optic disc parameters in a Thai population. MATERIAL AND METHOD: Two hundred and six eyes of 103 normal subjects aging from 30-80 years were studied Thirteen topographic disc parameters were analyzed by confocal scanning laser ophthalmoscope using Heidelburg retina tomography (HRT II). The average value of two eyes in the same subject was used as the unit of statistical analysis, and then the normal values and means were statistically calculated at 95% reference interval (95% RI). Ethnic differences of the calculated optic nerve topography were compared with previous studies. The relationship of age, intraocular pressure (IOP), central corneal thickness (CCT), and optic disc parameters were assessed by Pearson correlation. RESULTS: Mean values with 95% RI of all 13 parameters were analyzed Whole parameters except cup volume demonstrated normal distribution. Mean value (95% RI) of disc area in normal Thai people was 2.67 mm2 (1.96, 3.71) which was larger than Caucasian people. Ethnic differences in topographic optic disc parameters were found among Thai and other races including Asians, Caucasians, African-Americans, and Hispanics. The results also revealed that age, IOP, and CCT had no significant relation to all optic disc parameters. CONCLUSION: Thai people had a larger optic disc area than Caucasians. There are marked differences of topographic optic nerve parameters among different ethnic groups. These differences need to be taken into account when evaluating glaucomatous optic neuropathy and when comparing results of studies completed among population of different ethnic and racial origins.

High Prevalence of Ocular Surface Disease Among Glaucoma Patients in Thailand.

PURPOSE: To determine the prevalence of symptoms and signs of ocular surface disease (OSD) among Thai patients with glaucoma receiving topical intraocular pressure (IOP)-lowering therapy. METHODS: Consecutive patients with glaucoma were recruited prospectively for this cross-sectional study from Siriraj Hospital. Subjective symptoms were evaluated using the Ocular Surface Disease Index (OSDI), and objective clinical signs were evaluated using the tear breakup time (TBUT), corneal fluorescein, rose bengal staining, and the Schirmer test. RESULTS: One hundred nine patients (56% women; mean age, 64.0 ± 13.7 years) were included. The mean number of IOP-lowering eye drops instilled daily was 3.2 ± 2.4; the mean duration of treatment was 5.4 ± 3.9 years. Forty-two (38.5%) patients reported symptoms using the OSDI. The TBUT was normal in 1 patient, and the others (99.1%) had abnormal tear quality. Fluorescein and rose bengal staining showed positive results in 35 (32.1%) and 42 (38.6%) patients, respectively. The Schirmer test showed decreased tear production in 80 (73.4%) patients. A greater number of IOP-lowering eye drops daily was associated significantly with 3.8 and 4.4 times higher odds of abnormal corneal fluorescein and rose bengal staining, respectively (95% confidence interval [CI], 1.62-9.34, P = 0.002 and 95% CI, 1.91-10.32, P = 0.001, respectively). A significant (P = 0.03, 0.04) correlation was seen between OSDI and corneal dye staining tests. CONCLUSIONS: A high prevalence of OSD was found among glaucoma patients in Thailand. OSD is more prevalent in Asians than in westerners. Awareness regarding prescribing multiple IOP-lowering eye drops in Asians should be heightened to avoid ocular surface toxicity.

A comparative study of visual evoked potentials in optic neuritis and optic neuritis with multiple sclerosis.

OBJECTIVE: To compare the visual evoked potentials (VEP) in patients with acute optic neuritis, recurrent optic neuritis, and optic neuritis with multiple sclerosis. MATERIAL AND METHOD: The authors retrospectively reviewed VEP latency records of the patients with optic neuritis in Siriraj Hospital from 1995 to 2005 and divided them into three groups, acute optic neuritis, recurrent optic neuritis, and optic neuritis with multiple sclerosis (ON/MS). The patients with non-recordable VEP in the analysis were excluded. Comparison of the mean latency of the VEP in affected eyes among the three groups was statistically analyzed by a nonparametric independent sample test. RESULTS: Twenty-two patients with acute optic neuritis, 8 patients with recurrent optic neuritis, and 22 patients with ON/MS participated in this study. The mean age among the three groups was not statistically significant. The median value of the latency of flash VEP (fVEP) and pattern reversal VEP (PRVEP) in the acute optic neuritis group was shorter than that of the recurrent optic neuritis group, and statistically significant (fVEP p = 0.012; PRVEP, p = 0.004). The median value of the latency of PRVEP in the acute optic neuritis group was shorter than that of the ON/MS group, and statistically significant (PRVEP p = 0.002). The median value of the latency of both fVEP and PRVEP in the recurrent optic neuritis group and ON/MS group were delayed with no statistical significance (fVEP p = 0.458; PRVEP, p = 0.403). CONCLUSION: The VEP can be used to demonstrate the demyelinating mechanism of optic neuritis and optic neuritis with multiple sclerosis, but cannot determine the susceptibility of the patients with acute ON to become MS. The significantly delayed latency of VEP in recurrent optic neuritis is possibly caused by severe damage of the optic nerve conduction from recurrent attacks.

Tonometry after laser in situ keratomileusis treatment: a preliminary study in Thai patients.

OBJECTIVE: To evaluate the change in intraocular pressure (IOP) measurement by Goldmann applanation tonometer after Laser in Situ Keratomileusis (LASIK) for myopia and myopic astigmatism, and to assess the correlation between the changes of lOP reading and the reduction of central corneal thickness (CCT) after LASIK in Thai patients. STUDY DESIGN: Prospective correlational study. MATERIAL AND METHOD: LASIK was performed on 65 eyes of 33 patients for correction of myopia and myopic astigmatism. IOP was measured by Goldmann applanation tonometer before and 3 months after LASIK. The correlation between the change in IOP reading and the change in central corneal thickness were evaluated. RESULTS: IOP reading was significantly reduced by mean of 2.9 +/- 2.5 mmHg (p = 0.0001). The authors used Pearson analysis to study the correlation between the change in IOP and the reduction of CCT. In subgroup analysis the patients were divided by degree of myopia: group 1, myopia less than -3 diopters (D) (n = 14); group 2, myopia -3 to -6 D (n = 31); group 3, myopia greater than -6 D (n = 20)). The result showed more correlation in higher myopia group (Pearson; r = 0.158 in group 3, r = -0.098 in group 2 and r = -0.102 in group 1). CONCLUSION: Goldmann applanation tonometry underestimates the IOP in thin cornea. Variability in CCT is a potent confounder of this tonometry technique. Therefore, it has important implications for considering CCT measurement incorporated with Goldmann applanation tonometry for glaucoma diagnosis especially in myopic patients who undergo LASIK surgery.

Effect of 0.3% Hydroxypropyl Methylcellulose/Dextran Versus 0.18% Sodium Hyaluronate in the Treatment of Ocular Surface Disease in Glaucoma Patients: A Randomized, Double-Blind, and Controlled Study.

PURPOSE: To compare the efficacy and safety of 0.3% hydroxypropyl methylcellulose/dextran (HPMC/dextran) and 0.18% sodium hyaluronate (SH) in the treatment of ocular surface disease in patients using antiglaucoma drugs containing preservatives. METHODS: This was a double-blind, randomized, parallel-group study in 70 glaucoma patients with Ocular Surface Disease Index (OSDI) score greater than 20 points and/or presence of ocular signs. Patients were randomized to receive either preservative-free 0.3% HPMC/dextran (n=35) or preservative-free 0.18% SH (n=35). Treatment was 1 drop in each eye, 4 times a day. Data were collected at baseline, at day 7 and day 28. RESULTS: The groups were homogeneous at baseline. At day 28, both treatments showed significant improvements (P<0.05) in the mean OSDI score, lid skin and lid margin inflammation, conjunctival injection, and expressibility of meibomian glands, corneal staining score, fluorescein tear breakup time (FBUT), and Schirmer I test. However, the mean OSDI score, lid margin inflammation and conjunctival injection showed significant improvements (P<0.05) in the SH group at days 7 and 28, compared to the HPMC/dextran group. FBUT and the Schirmer I test also showed significant improvements (P<0.05) in the SH group compared to the HPMC/dextran group, at day 28. No adverse reactions were observed in either group. CONCLUSIONS: Preservative-free artificial tear, 0.3% HPMC/dextran, and 0.18% SH, caused a significant relief of the ocular surface disease in glaucoma patients. However, 0.18% SH led to a greater improvement in ocular signs and symptoms than 0.3% HPMC/dextran.

Efficacy of brimonidine 0.2 per cent as adjunctive therapy to beta-blockers: a comparative study between POAG and CACG in Asian eyes.

OBJECTIVE: To compare the efficacy and safety profile of brimonidine as adjunctive therapy to beta-blockers between primary open angle glaucoma (POAG) and chronic angle closure glaucoma (CACG) in Asian eyes. DESIGN: Three-months, open-label, prospective study. PARTICIPANTS: Twenty-three patients (35 eyes) with POAG and 25 patients (39 eyes) with CACG were enrolled in the study. INTERVENTION: Patients with POAG or CACG post iridectomy whose IOP was inadequately controlled with topical beta-blocker monotherapy were included. Then, brimonidine 0.2 per cent was added twice daily in both groups. Study visit occurred at weeks 2, 4, 8, and 12. Complete ophthalmic examinations were performed in all visits. MAIN OUTCOME MEASURES: Efficacy was determined by reduction in IOP from baseline and tolerability was assessed by reports of adverse events. RESULTS: After 3 months of brimonidine adjunctive treatment, the mean (+/- SEM) IOP reduction were 4.37+/-0.34 mmHg (19.4%) in POAG and 4.54+/-0.37 mmHg (20.1%) in CACG (p= 0.741). No serious ocular or systemic adverse event was reported. CONCLUSION: Brimonidine was well tolerated, efficacious and provided additive IOP reduction in POAG and CACG.

Evaluation of screening tests and prevalence of glaucoma: integrated health research program for the Thai elderly.

The purposes of this study were to evaluate the accuracy of glaucoma screening tests and to assess the prevalence of glaucoma in an elderly Thai population over 60 years of age. This was a cross-sectional study. 3706 subjects were recruited from 33 communities in the vicinity of Siriraj Hospital. All received an eye examination from ophthalmologists and general practitioners including visual acuity, Schiotz tonometry and optic disc evaluation in their residential communities. Subjects who were suspected of having glaucoma were re-examined at the Glaucoma Clinic, Siriraj Hospital. They were then classified as having definite glaucoma of a specific type or as not having glaucoma. The overall prevalence of glaucoma was 6.1 per cent (128/2092). The percentages of primary open angle glaucoma, primary angle closure glaucoma, normotension glaucoma and secondary glaucoma were 47.7 per cent, 41.4 per cent, 9.4 per cent, and 1.6 per cent respectively. The sensitivity and specificity of the screening tests performed by ophthalmologists were 100 per cent and 97.2 per cent and those performed by general practitioners were 21.7 per cent and 96.5 per cent.

Prevalence and risk factors for chloroquine maculopathy and role of plasma chloroquine and desethylchloroquine concentrations in predicting chloroquine maculopathy.

AIM: To determine the prevalence and to identify the risk factors of chloroquine maculopathy (CM), and to evaluate the association of plasma chloroquine (CQ) and desethylchloroquine (DCQ) levels and CM. METHODS: Rheumatoid arthritis (RA) patients who had taken CQ for at least 6 months and stable CQ dosage for at least 2 months were included. CM was diagnosed by dilated ocular examination and automated visual field. Plasma CQ and DCQ levels were determined by liquid chromatography tandem mass spectrometry method. Logistic regression was used to explore risk factors associated with CM. RESULTS: One hundred and ninety-three patients were included with median CQ duration (range) of 50.2 months (6.0-269.8) and cumulative dose of 137.4 g (16.4-1226.5). The prevalence of CM was 13.5%. Factors associated with CM identified from univariate analysis were age > 60 years, and creatinine clearance with odds ratio (OR) (95%CI) of 5.79 (2.42, 13.84), and 0.98 (0.96, 1.00). In multivariate analysis, older age, usage > 5 years, and current dose from 2.5 mg/kg ideal body weight [IBW]/day were the factors significantly associated with CM with OR of 5.89 (2.38, 14.57), 2.94 (1.10, 7.83), and 3.32 (1.04, 10.60), respectively, while plasma CQ and DCQ showed no association with CM. CONCLUSIONS: The prevalence of CM was 13.5% among RA patients taking CQ for at least 6 months. Age > 60 years, duration of CQ usage > 5 years and current CQ dose ≥2.5 mg/kg IBW/day were the risk factors for CM. The plasma CQ or DCQ levels demonstrated no correlation in developing CM.

The unique characteristics of Thai Leber hereditary optic neuropathy: analysis of 30 G11778A pedigrees.

Leber hereditary optic neuropathy (LHON) is characterized by acute or subacute bilateral visual loss, and affects mostly young males. The most common mitochondrial DNA mutation responsible for LHON worldwide is G11778A. Despite different genetic backgrounds, which are believed to influence the disease expression, most features of LHON are quite common in different populations. However, there seem to be a few ethnic-specific differences. Analyses of our 30 G11778A LHON pedigrees in Thailand showed some characteristics different from those of Caucasians and Japanese. In particular, our pedigrees showed a lower male to female ratio of affected persons (2.6:1) and much higher prevalence of G11778A blood heteroplasmy (37% of the pedigrees contained at least one heteroplasmic G11778A individual). Heteroplasmicity seemed to influence disease manifestation in our patients but did not appear to alter the onset of the disease. The estimated overall penetrance of our G11778A LHON population was 37% for males and 13% for females. When each of our large pedigrees were considered separately, disease penetration varied from 9 to 45% between the pedigrees, and also varied between different branches of the same large pedigree. Survival analysis showed that the secondary LHON mutations G3316A and C3497T had a synergistic deleterious effect with the G11778A mutation, accelerating the onset of the disease in our patients.

Visual electrophysiology in congenital nystagmus with normal fundus.

OBJECTIVE: To identify the ophthalmic causes of congenital nystagmus with normal eye examination by visual electrophysiologic tests. MATERIAL AND METHOD: Medical records of patients who presented with nystagmus and no other neurological sign before 6 months of age with normal eye examination, between February 2004 and February 2005, were reviewed Complete ophthalmic examination and visual electrophysiologic tests were performed to identify the ophthalmic causes of congenital nystagmus. RESULTS: Thirty-four patients had met the criteria. Leber's congenital amaurosis was diagnosed in 13 patients (38.2%) by non-recordable electroretinography (ERG) and normal visual evoked potential (VEP). Idiopathic infantile nystagmus was diagnosed in 12 patients (35.3%) by normal ERG and VEP. Achromatopsia was diagnosed in 8 patients (23.5%) by flat retinal cone ERG but normal rod ERG and VEP. Rod-cone dystrophy was diagnosed in one patient (3%) by abnormal rod and cone ERG CONCLUSION: Visual electrophysiologic study is helpful to identify the ophthalmic causes of congenital nystagmus. Leber's congenital amaurosis is a common cause in congenital nystagmus.

Normative data of optic nerve head in Thai population by laser scanning tomography: Siriraj study.

OBJECTIVE: To study the normative values of topographic optic disc parameters in a Thai population. MATERIAL AND METHOD: Two hundred and six eyes of 103 normal subjects aging from 30-80 years were studied Thirteen topographic disc parameters were analyzed by confocal scanning laser ophthalmoscope using Heidelburg retina tomography (HRT II). The average value of two eyes in the same subject was used as the unit of statistical analysis, and then the normal values and means were statistically calculated at 95% reference interval (95% RI). Ethnic differences of the calculated optic nerve topography were compared with previous studies. The relationship of age, intraocular pressure (IOP), central corneal thickness (CCT), and optic disc parameters were assessed by Pearson correlation. RESULTS: Mean values with 95% RI of all 13 parameters were analyzed Whole parameters except cup volume demonstrated normal distribution. Mean value (95% RI) of disc area in normal Thai people was 2.67 mm2 (1.96, 3.71) which was larger than Caucasian people. Ethnic differences in topographic optic disc parameters were found among Thai and other races including Asians, Caucasians, African-Americans, and Hispanics. The results also revealed that age, IOP, and CCT had no significant relation to all optic disc parameters. CONCLUSION: Thai people had a larger optic disc area than Caucasians. There are marked differences of topographic optic nerve parameters among different ethnic groups. These differences need to be taken into account when evaluating glaucomatous optic neuropathy and when comparing results of studies completed among population of different ethnic and racial origins.

Normative data of electroretinogram and visual evoked potential in Thai population.

Objective : To define normal values of Electroretinogram [ERG] and Visual Evoked Potential [VEP] in different age groups using Viking Select Master Software V7.1. Methods: ERG and VEP values were measured using Viking Select Master Software V7.1 in selected subjects without history of ocular and/or systemic diseases that affect ERG and VEP values. Results were studied in three groups of age: less than 10 years old, 11 to 40 years old and over 40 years old. Results: There were 26 eyes in the first group with age range from 6-10 years old [mean 7.8 + 1.52 years old]. In ERG : the normal values of photopic amplitude of ; a-wave was> 18.57 microvoltage [ตV] and b-wave was> 23.82 ตV, flickering amplitude of b-wave was > 21.93 ตV, scotopic amplitude of b-wave was> 39.12 ตV, mesopic amplitude of ; a-wave was > 60.44 ตV and b-wave was > 96.84 ตV. In VEP : transient flash amplitude was> 20.58 ตV and latency was < 94.10 millisecond[ms], transient pattern size 2 amplitude was > 8.61 ตV and latency was < 100.00 ms. There were 75 eyes in the second group with age range from 11-38 years old [mean 26.8 + 7.35 years old]. The values of photopic amplitude of ; a-wave was > 22.56 ตV and b-wave was > 20.14 ตV, flickering amplitude of b-wave was > 19.35 ตV, scotopic amplitude of b-wave was > 32.29 ตV, mesopic amplitude of ; a-wave was > 45.05 ตV and b-wave was> 78.97 ตV, VEP- transient flash amplitude was > 11.64 ตV and latency was < 96.78 ms, transient pattern size 2 amplitude was > 4.82 ตV and latency was < 88.49 ms. There were 77 eyes in the third group with age range from 41-81 years old [mean 60.1 + 11.54 years old]. The values of photopic amplitude of; a-wave was > 19.12 ตV and b-wave was > 24.59 ตV, flickering amplitude of b-wave was > 18.76 ตV, scotopic amplitude of b-wave was > 35.60 ตV, mesopic amplitude of ; a-wave was > 40.90 ตV and b-wave was > 94.09 ตV, VEP- transient flash amplitude was > 10.07 ตV and latency was < 102.10 ms, transient pattern size 2 amplitude was > 5.34 ตV and latency was < 96.00 ms. Conclusion: We established normal ERG and VEP values in different age group using Viking Select Master Software V7.1 at Siriraj Hospital to distinguish between normal and pathological patients. The values are affected in relation to machine and environmental setting in different laboratory. It is essential for individual laboratories to set their own normal values.

A comparative study of visual evoked potentials in optic neuritis and optic neuritis with multiple sclerosis.

OBJECTIVE: To compare the visual evoked potentials (VEP) in patients with acute optic neuritis, recurrent optic neuritis, and optic neuritis with multiple sclerosis. MATERIAL AND METHOD: The authors retrospectively reviewed VEP latency records of the patients with optic neuritis in Siriraj Hospital from 1995 to 2005 and divided them into three groups, acute optic neuritis, recurrent optic neuritis, and optic neuritis with multiple sclerosis (ON/MS). The patients with non-recordable VEP in the analysis were excluded. Comparison of the mean latency of the VEP in affected eyes among the three groups was statistically analyzed by a nonparametric independent sample test. RESULTS: Twenty-two patients with acute optic neuritis, 8 patients with recurrent optic neuritis, and 22 patients with ON/MS participated in this study. The mean age among the three groups was not statistically significant. The median value of the latency of flash VEP (fVEP) and pattern reversal VEP (PRVEP) in the acute optic neuritis group was shorter than that of the recurrent optic neuritis group, and statistically significant (fVEP p = 0.012; PRVEP, p = 0.004). The median value of the latency of PRVEP in the acute optic neuritis group was shorter than that of the ON/MS group, and statistically significant (PRVEP p = 0.002). The median value of the latency of both fVEP and PRVEP in the recurrent optic neuritis group and ON/MS group were delayed with no statistical significance (fVEP p = 0.458; PRVEP, p = 0.403). CONCLUSION: The VEP can be used to demonstrate the demyelinating mechanism of optic neuritis and optic neuritis with multiple sclerosis, but cannot determine the susceptibility of the patients with acute ON to become MS. The significantly delayed latency of VEP in recurrent optic neuritis is possibly caused by severe damage of the optic nerve conduction from recurrent attacks.