Axial Length in Patients with Myopia and Interpretation of Pattern Electroretinogram Recordings

Correlations between Steady-State Pattern Electroretinogram and Humphrey Visual Field Analyzer Global Indices and Their Associations with Retinal Ganglion Cell Layer-Inner Plexiform Layer Thickness in Glaucoma Suspects

Purpose

The purpose of this study was to investigate the utility of steady state pattern electroretinogram (ss-PERG) in detecting retinal ganglion cell (RGC) dysfunction in glaucoma suspects (GS) who had normal 24-2 Humphrey Visual Fields (HFA).

Materials and Methods

This was a prospective cohort study of GS patients who were identified based on optic disc appearance with normal HFAs. Patients received a complete eye examination, standard automated perimetry (SAP), optical coherence tomography (OCT), and ss-PERG measurements. The ss-PERG parameters, Magnitude (Mag), Magnitude D (MagD), and MagD/Mag ratio, were examined, along with their relationships between HFA and OCT measurements.

Results

Twenty-five patients were included in this study, with a total of 49 eyes. Fifteen eyes had abnormal ss-PERG parameters and when compared to GS eyes with normal ss-PERG parameters, there were significant differences in HFA 24-2, retinal nerve fiber layer (RNFL) thickness, and ganglion cell layer and inner plexiform layer (GCL + IPL) thickness. All ss-PERG parameters were significantly correlated with 24-2 VF mean deviation (MD) and visual field index (VFI), as well as 10-2 VF MD after controlling for age, sex, intraocular pressure, central corneal thickness, and spherical equivalent. When controlled for age, spherical equivalent, and IOP, MagD/Mag ratio significantly contributed to the variance in average GCL + IPL thicknesses, whereas 24-2 VF MD and 10-2 VF MD did not. MagD/Mag ratio also significantly accounted for variance in all macular GCL + IPL sectors, while 10-2 VF MD did not.

Conclusions

ss-PERG has significant correlations with HFA global indices and was predictive of GCL + IPL thickness in GS patients. Clinical Significance. ss-PERG may serve as a useful functional tool for detecting and measuring RGC dysfunction in GS. It appears to be more sensitive than HFA in the detection of early changes in GCL + IPL thicknesses and may be helpful to use in conjunction with current diagnostic studies to improve the ability of monitoring GS progression.

Pattern electroretinography response in amblyopic adults

INTRODUCTION

Amblyopia is generally a unilateral disorder, defined by at least a difference of two lines of visual acuity between both eyes with the best-corrected visual acuity, a decrease in contrast sensitivity, and a decrease in stereopsis. Pattern electroretinogram (PERG) is a noninvasive technique that provides a retinal biopotential and is a highly sensitive indicator of changes in the macular area. Our aim was to evaluate if there are differences in the retinal response of an amblyopic eye compared with a normal eye (NE).

METHODS

We evaluated twenty-four adult volunteers, twelve amblyopes (mean 43.42 ± 12.72 years old), and twelve subjects with NE (mean 35.58 ± 12.85 years old). None of the subjects in the two groups had comorbidities. A complete optometric examination was performed including parameters such as visual acuity (VA) by far and near with ETDRS chart, eye alignment with cover test, and evaluation of retinal cells response with PERG.

RESULTS

The refractive error found in the NE group of subjects had a mean of - 0.95 ± 1.65D, while the amblyopic group showed a mean of - 2.03 ± 4.29D. The VA in amblyopic eyes had a mean of 0.38 ± 0.20 logMAR. Analyzing PERG data, we observed significant differences in the P50-N95 amplitudes of the amblyopic group compared with the NE group (p < 0.0001-amblyopic eye vs. NE; p = 0.039-fellow eye vs. NE).

DISCUSSION

These findings suggest that amblyopic patients may also present other impairments beyond the visual cortex. PERGs seem to be an important complementary examination in the diagnosis of other impairments in amblyopia.

Macular function in patients with medium myopia

Purpose

This work aims at assessing whether electrophysiological functional changes in the macular region appear in medium myopia, even in the presence of a normal macular OCT scan and how axial length correlates with macular OCT parameters in medium myopia.

Methods

The study included right eyes of 17 patients with myopia of medium degree (SE <  − 6D to >  − 3D). Control group consisted of 20 eyes of patients of age and sex that matched healthy controls with normal macular and optic nerve OCT results and normal axial length. Full ophthalmic examination (the distance best-corrected visual acuity, intraocular pressure, refractive error, the anterior and posterior segment of the eye in a slit lamp, the axial length of the eyeball) with OCT of the macular and optic disk and the PERG test were performed in the study and control groups. Only the patients with normal ophthalmic and OCT examination results were qualified. The interview covering questions on risk factors of myopia onset and progression such as prematurity, family history of myopia was carried out in both groups. In myopic group, the question relating to time of near work was also asked. Study and control groups were tested with the use of Shapiro–Wilk, Mann–Whitney, Student’s t test, Pearson and Spearman's rank correlation tests.

Results

AL was significantly longer in myopia group (p < 0.01), and SE value was lower (p < 0.01). Longer implicit time of P50 was found in the study group, but amplitudes of P50 and N95 waves were not significantly reduced (p < 0.05). AL showed correlations with P50 implicit time (p < 0.05) and with reduction in retinal fiber nerve layer and ganglion cells and inner plexus layer (p < 0.05).

Conclusion

Patients with myopia of medium degree have a dysfunction of retinal cone system of the macular region even when OCT scans show no abnormalities. Elongation of AL correlates with reduction in retinal fiber nerve layer and ganglion cells and inner plexus layer. Longitudinal follow-up studies may answer the question whether this increase in implicit time may be indicative of a faster myopia progression or of myopic retinal pathology, i.e., whether it may help to determine which patient would benefit from earlier or more intensive management of myopia progression.

Steady-State Pattern Electroretinography in Eyes with Glaucoma and High Myopia

Purpose

To investigate features of the steady-state pattern electroretinogram (ssPERG) in subjects with glaucoma (G), high myopia (HM; spherical equivalent ≤-6D) and glaucoma with high myopia (GHM).

Patients and Methods

Our study included 48 participants divided into 3 groups (G, HM, and GHM) who each underwent monocular ssPERG testing with Diopsys NOVA PERG protocols. The ConStim protocol detects distinct topographic patterns of dysfunction 16° and 24° around the central macula. MagD is the amplitude of the average signal and MagD/Mag ratio indicates the consistency of the response. ssPERG indices were compared between groups and correlated with functional (ie, visual field mean deviation (VFMD)) and structural (ie, average retinal nerve fibre layer (RNFL) thickness; Cirrus optical coherence tomography) features.

Results

Participants had an average age of 59.4±7.6 years. Mean Humphrey VFMD was -14.22 ± 2.88dB, -2.62 ± 1.18dB and -12.80 ± 2.60dB for G, HM and GHM groups, respectively. Mean RNFL thickness was 63.0 ± 8.20μm, 69.5 ± 15.7μm and 60.6 ± 5.0μm for G, HM and GHM groups, respectively. For the 24° setting, no significant differences were noted for any of the parameters. For the 16° setting, MagD was lower in the GHM group compared to the HM group (0.29µV vs 0.52µV; p = 0.02). Significant differences were noted for the MagD/Mag ratio between HM and G groups (0.58 vs 0.40; p = 0.02) and between HM and GHM groups (0.58 vs 0.35; p = 0.002). There were positive correlations between both MagD 16° and MagD/Mag ratio 16° with VFMD (correlation coefficient [r]=0.37, p = 0.009; and r = 0.44, p = 0.002, respectively) and RNFL (r = 0.43, p = 0.002; and r = 0.48, p = 0.001, respectively).

Conclusion

MagD/Mag ratio at 16° was significantly lower in glaucomatous eyes (with or without high myopia) compared to those with high myopia without glaucoma, suggesting that glaucoma has a distinct impact on MagD/Mag ratio at 16° irrespective of the presence of myopia.