Electroretinograms (ERGs) elicited by transient, square-wave L- and M-cone isolating stimuli were recorded from human trichromatic (n=19) and dichromatic (n=4) observers. The stimuli were generated on a four primary LED stimulator and were equated in terms of cone modulation (cone contrast=0.11) and retinal illuminance (12,000 trolands). L- and M-cone isolated ERGs had waveforms similar to those observed for luminance responses. However, M-cone ERGs exhibited a phase reversal in their responses to onset and offset stimuli relative to the L-cone responses. This on-off response reversal was observed in trichromats but not dichromats. Simultaneous counterphase and inphase combinations of L- and M-cone isolating stimuli generated responses that reflected chromatic and luminance processing, respectively. We conclude that L- and M-cone specific ERGs provide a measure of how photoreceptors contribute to postreceptoral mechanisms.

We recorded L- and M-cone isolating ERGs from human subjects using a silent substitution technique at temporal rates of 12 and 30 Hz. These frequencies isolate the activity of cone-opponent and non-opponent post-receptoral mechanisms, respectively. ERGs were obtained using a sequence of stimuli with different spatial configurations comprising; (1) circular stimuli of different sizes which increased in 10° steps up to 70°diameter, or (2) annular stimuli with a 70° outer diameter but with different sized central ablations from 10° up to 60°. L- and M-cone isolating ERGs were obtained from five colour normal subjects using a DTL fibre electrode. Fourier analysis of the ERGs was performed and we measured the amplitude of the first harmonic of the response. For 12 Hz ERGs the L:M cone response amplitude ratio (L:M(ERG)) was close to unity and remained stable irrespective of the spatial configuration of the stimulus. The maintenance of this balanced ratio points to the existence of cone selective input across the human retina for the L-M cone opponent mechanism. For 30 Hz the L:M(ERG) ratio was greater than unity but varied depending upon which region of the retina was being stimulated. This variation we consider to be a consequence of the global response properties of M-cone ERGs rather than representing a real variation in L:M cone ratios across the retina.

Aim To determine the absolute and relative ocular protrusion values in normal south Indian population, and its relation to age, gender and type of refractive error. Methods A total of 387 subjects aged 7–70 years were included in this study. Both right and left absolute ocular protrusion values were measured by a single physician using Luedde exophthalmometer in primary gaze. Right eye ocular protrusion data were used for reporting the absolute ocular protrusion values, and difference between right and left eye absolute ocular protrusion values of the same individual was used to report the relative ocular protrusion values. Subject age was grouped as decades. Measurement values were evaluated by descriptive and inferential statistics. Results The mean absolute ocular protrusion of right eye was 14.67 ± 1.70 mm and left eye was 14.32 ± 1.75 mm. The mean right absolute ocular protrusion values from 1st to 7th decade were 12.73 ± 1.21 mm, 14.8 ± 1.25 mm, 15.79 ± 1.31 mm, 15.77 ± 1.36 mm, 15.87 ± 1.28 mm, 15 ± 1.03 mm and 14.36 ± 0.88 mm respectively. One-way analysis of variance showed that there was a significant difference in the ocular protrusion among the age groups ( p < 0.005). The mean relative ocular protrusion was 0.35 ± 0.64 mm. The type of refractive error (up to ±6.00D) has no significant effect on the absolute ocular protrusion values and showed a weak correlation between magnitude of myopia and hyperopia on absolute ocular protrusion. There was a statistically significant difference in absolute ocular protrusion among the female and male subjects. Conclusion Age and gender seems to significantly influence the absolute ocular protrusion and need to be considered for clinical evaluation of bilateral proptosis. The refractive error up to ±6.00D seems to have no significant effect on the absolute ocular protrusion.

A bstract Purpose To assess the optic nerve head (ONH) parameters in normal male Saudi eyes using swept-source optical coherence tomography (SS-OCT). Materials and methods The study included 86 healthy men with a mean age of 23.6 ± 4.82 years. The metrics collected using SS-OCT from each individual was disk area (DA), rim area (RA), cup volume (CV), linear cup–disk ratio (LCDR), vertical cup–disk ratio (VCDR), and total retinal nerve fiber layer (RNFL) thickness, superior RNFL thickness, and inferior RNFL thickness. All the metrics were correlated with the DA. The right eye data were used for the correlation analysis. Results The mean DA in OD was 1.78 mm 2 (range 1.09–2.70 mm 2 ). The mean RA was 1.28 mm 2 (range 0.72–2.47 mm 2 ). The DA showed a significant positive correlation ( p < 0.05) with RA, cup area (CA), CV, VCDR, LCDR, and total RNFL thickness. Conclusion For the first time, using sweeping source OCT (DRI OCT Triton, Topcon Corporation), a normative database of ONH parameters was made accessible to the Saudi male population. While assessing the optic disk for progressive optic neuropathies like glaucoma, disk size should be taken into consideration since the optic DA affects ONH topography, especially in Saudi eyes. How to cite this article Challa NK. Optic Nerve Head Parameters in Saudi Male Young Adults Using Swept-source Optical Coherence Tomography. J Curr Glaucoma Pract 2023;17(2):58-62.

Purpose To report the aetiology, visual outcome, and clinical features of indirect traumatic Optic Neuropathy (TON) patients from the tertiary eye care center, South India. Methods It is aretrospective and observational study. Details of ge, gender, number of days of presentation after injury, Snellen visual acuity at presentation and last follow-up, visual evoked potentials, visual field findings using the Humphrey visual field analyser, associated ocular complications, and mode and time of treatment were obtained from the medical records of all indirect TON patients. Results Indirect TON patients are mainly young males (94%) and the road traffic accident (RTA)(65%) is the main cause of TON , followed by falls (19%) and sport-related activities (11%). Visual acuity loss was severe in more than 50% of the subjects and only 16%% of the patients have shown improvement in visual acuity greater than one line. Pattern visual evoked potentials and visual fields are recordable only in 15% of the subjects. Commonly associated ocular complications in indirect TON patients were orbital fracture (43%), lid tear (16%), sub-conjunctival haemorrhage (13.5%), and angle recession(13.5%) Three out of four patients who received methylprednisolone and oral steroids within a week showed an improvement in visual acuity of greater than three lines, while just one patient out of four who received the same medication after a week improved visual acuity of three lines. Conclusion RTA (road traffic accidents) is the most common cause of indirect TON and mainly young males were the affected individuals. IVMP along with oral steroids within a week would help TON patients for reasonable visual recovery. Presenting Visual acuity of > 6/600 and recordable pattern VEPs would be the prognostic factors for good visual outcome in indirect TON patients.