Retinal Thickening and Photoreceptor Loss in HIV Eyes without Retinitis

Functional and structural neuroretinal disorders in HIV Controllers. Prospective cohort study

OBJECTIVE

To estimate the prevalence and cumulative incidence of neuro-retinal-disorders (NRD) in HIV-controllers.

DESIGN

Prospective, single-centre, cohort study of people living with HIV (PLWH): elite-controllers, long-term-non-progressors and early diagnosed.

METHODS

The study compared "HIV-controllers" (including elite-controllers and long-term-non-progressors), who were not on antiretroviral therapy (ART), and "HIV-treatment" (HIV-infected subjects with a recent diagnosis and on ART). A matched cohort of "non-HIV subjects" was created. NRD was defined as at least one altered (not normal) ophthalmological parameter (functional or structural). Functional (visual acuity, contrast sensitivity, chromatic vision, visual field) and structural parameters (ganglion cells, macular nerve fibre layer, peripapillary nerve fibre layers, vascular calibre) as well as quality of life (Medical Outcomes Study-HIV Short Form-30) were assessed.

RESULTS

Between March 2012 and November 2015, the study included all HIV-controllers (16 elite-controllers, 1 long-term-non-progressor), 11 HIV-treatment and 16 non-HIV. Prevalence of NRD at baseline was 88.2% (15/17, 95% CI: 65.7%-96.7%), 90.9% (10/11, 95% CI: 62.3%-98.4%) and 56.3% (9/16, 95% CI: 33.2%-76.9%), respectively. Cumulative incidence at 3 years was 50% (1/2), 100% (1/1) and 33.3% (2/6), respectively. None of the participants manifested ocular clinical symptoms. Three years later, prevalence of NRD was 92.3% (12/13, 95% CI: 66.7%-98.6%), 75% (6/8, 95% CI: 40.9%-92.9%) and 50.0% (7/14, 95% CI: 26.8%-73.2%), respectively. Contrast sensitivity and structural parameters were globally the most affected among PLWH. Quality of life (total score) [median (interquartile range)] at baseline and 3 years was 82 (71-89) and 74 (63.5-79.25) in HIV-controllers and 80 (73-88) and 88 (83-92) in HIV-treatment.

CONCLUSIONS

HIV-controllers and those individuals on ART presented a higher percentage of NRD than non-HIV. Our results suggest that NRD could be a biomarker of ocular aging among PLWH.

Comparison of Retinal Structure Using Optical Coherence Tomography Angiography between Persons with and without HIV Infection

HIV retinal microangiopathy is an important predictor for increased risk of mortality. Optical coherence tomography angiography (OCTA) can investigate microvascular changes resulting from retinal diseases. Study included 25 persons with HIV and 25 healthy persons. OCTA evaluated the vascularization of retinal layers, choriocapillary, and optic disk. HIV group had lower vessel flow density (VFD) in superficial plexus. No difference was observed in the deep plexus. VFD of the optic disk and peripapillary region showed no difference between the groups. HIV group showed a thinner retinal nerve fiber layer and smaller area of the optic disk rim. HIV infection is associated with VFD reduction in superficial retinal plexus, neural rim area reduction, and retinal nerve fiber layer thinning in individuals without microangiopathic alterations on fundus examination. Therefore, OCTA can find retinal changes before clinical evidence of retinopathy.

Inflammatory mechanisms contributing to retinal alterations in HIV infection and long-term ART

People living with HIV (PLWH) may face an increased risk of eye complications associated with ageing, chronic inflammation, and the toxicity arising from long-term antiretroviral therapy (ART). This review aims to understand how inflammatory pathways contribute to retinal alterations observed in PLWH on long-term ART. This review was conducted using four electronic database searches, namely Scopus, Hinari, Google Scholar, and PubMed; from 1996 (when ART became available) until January 2022, without language restriction. Sources from clinical trials, meta-analyses, randomised controlled trials, and systematic reviews were used. Dysregulated para-inflammation (chronic inflammation) damages the blood-retina barrier, resulting in the altered retinal immune privilege and leading to the development of retinal and blood vessel changes. There is an interplay between the effects of the disease versus ART. ART causes mitochondrial toxicity, which affects the retinal ganglion cells and retinal pigment epithelium (RPE) due to oxidative stress. Infection by HIV also affects retinal microglia, which contributes to RPE damage. Both of these mechanisms affect the blood vessels. Assessing the integrity of the inner and outer blood-retina barrier is a pivotal point in pinpointing the pathogenesis of inner retinal alterations. Optical coherence tomography is a valuable tool to assess these changes. There is a paucity of research to understand how these structural changes may affect visual function, such as contrast sensitivity and colour vision.

Early inner plexiform layer thinning and retinal nerve fiber layer thickening in excitotoxic retinal injury using deep learning-assisted optical coherence tomography

Excitotoxicity from the impairment of glutamate uptake constitutes an important mechanism in neurodegenerative diseases such as Alzheimer's, multiple sclerosis, and Parkinson's disease. Within the eye, excitotoxicity is thought to play a critical role in retinal ganglion cell death in glaucoma, diabetic retinopathy, retinal ischemia, and optic nerve injury, yet how excitotoxic injury impacts different retinal layers is not well understood. Here, we investigated the longitudinal effects of N-methyl-D-aspartate (NMDA)-induced excitotoxic retinal injury in a rat model using deep learning-assisted retinal layer thickness estimation. Before and after unilateral intravitreal NMDA injection in nine adult Long Evans rats, spectral-domain optical coherence tomography (OCT) was used to acquire volumetric retinal images in both eyes over 4 weeks. Ten retinal layers were automatically segmented from the OCT data using our deep learning-based algorithm. Retinal degeneration was evaluated using layer-specific retinal thickness changes at each time point (before, and at 3, 7, and 28 days after NMDA injection). Within the inner retina, our OCT results showed that retinal thinning occurred first in the inner plexiform layer at 3 days after NMDA injection, followed by the inner nuclear layer at 7 days post-injury. In contrast, the retinal nerve fiber layer exhibited an initial thickening 3 days after NMDA injection, followed by normalization and thinning up to 4 weeks post-injury. Our results demonstrated the pathological cascades of NMDA-induced neurotoxicity across different layers of the retina. The early inner plexiform layer thinning suggests early dendritic shrinkage, whereas the initial retinal nerve fiber layer thickening before subsequent normalization and thinning indicates early inflammation before axonal loss and cell death. These findings implicate the inner plexiform layer as an early imaging biomarker of excitotoxic retinal degeneration, whereas caution is warranted when interpreting the ganglion cell complex combining retinal nerve fiber layer, ganglion cell layer, and inner plexiform layer thicknesses in conventional OCT measures. Deep learning-assisted retinal layer segmentation and longitudinal OCT monitoring can help evaluate the different phases of retinal layer damage upon excitotoxicity.

Development of retinal structure in perinatally HIV-infected children and adolescents: A longitudinal and cross-sectional assessment

In perinatally HIV-infected (PHIV) children, cross-sectional studies reported on subtle structural retinal differences and found associations between the retina and structural brain changes. Our objective is to investigate whether neuroretinal development in PHIV children is similar to the development in healthy matched controls and to explore associations with the brain structure. We measured RT using optical coherence tomography (OCT) on two occasions in 21 PHIV children or adolescents and 23 matched controls-all with good visual acuity-with a mean interval of 4.6 years (SD 0.3). We also included 22 participants (11 PHIV children and 11 controls) together with the follow-up group for a cross-sectional assessment using a different OCT device. Magnetic resonance imaging (MRI) was used to assess the white matter microstructure. We used linear (mixed) models to assess changes in RT and its determinants (over time), adjusting for age and sex. The development of the retina was similar between the PHIV adolescents and controls. In our cohort, we found that changes in the peripapillary RNFL was significantly associated with changes in WM microstructural makers: fractional anisotropy (coefficient = 0.030, p = 0.022) and radial diffusivity (coefficient = -0.568, p = 0.025). We found comparable RT between groups. A thinner pRNFL was associated with lower WM volume (coefficient = 0.117, p = 0.030). PHIV children or adolescents appear to have a similar development of the retinal structure. In our cohort, the associations between RT and MRI biomarkers underscore the relation between retina and brain.

Reference Database of Inner Retinal Layer Thickness and Thickness Asymmetry in Healthy Thai Adults as Measured by the Spectralis Spectral-Domain Optical Coherence Tomography

INTRODUCTION

The study aimed to determine a reference database of the thickness and intraocular thickness asymmetry of total retina, retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), and inner plexiform layer (IPL) in healthy Thai subjects measured by the Spectralis spectral-domain optical coherence tomography.

METHODS

This cross-sectional study recruited the healthy subjects age ≥18 years, having spherical refraction within ±6 diopters and cylindrical refraction ±3 diopters, from a hospital's personnel and the people visiting the ophthalmology department. Only 1 eye of each subject was randomly selected for an analysis. Macular images were obtained using posterior pole thickness scan protocol over a 24° × 24° area at the center of the fovea. The automated retinal thickness segmentation values of total retina and three inner retinal layers were calculated for the mean and the mean intraocular thickness difference between superior and inferior retinal hemispheres. The influence of age, gender, and axial length on thickness and thickness asymmetry of individualized retinal layer was evaluated.

RESULTS

252 subjects were included in study with a mean (SD) age of 46.7 (15.8) years, and 120 (47.6%) were males. According to the Early Treatment Diabetic Retinopathy Study map, the inner ring area was the thickest location of the total retina (range; 326.0-341.5 µm), GCL (range; 47.7-52.7 µm), and IPL (range; 39.9-42.1 µm), whereas the thickest location of RNFL was at the outer ring area (range; 18.8-47.5 µm). For posterior pole intraocular thickness asymmetry, the greatest mean ± SD difference was observed for total retina (9.0 ± 2.2 µm), followed by RNFL (9.9 ± 3.2 µm) and GCL (2.7 ± 0.6 µm), and the lowest mean difference was noted for IPL (2.4 ± 0.5 µm). The thickness and thickness asymmetry of each retinal layer were variably influenced by age, gender, and axial length; however, these factors had a minimal influence on the thickness asymmetry maps of GCL and RNFL.

CONCLUSION

The reference database of the macular thickness and thickness asymmetry from this study would be beneficial in determining physiologic variations of the OCT parameters in the healthy Thai population.

The Integrity of Retinal Morphology in Non-immunocompromised People Living with HIV on Antiretroviral Therapy

SIGNIFICANCE

Non-immunocompromised people living with HIV (NIPLHIV) share a similar immunocompetence to non-HIV (HIV) people with an elevated cluster of differentiation 4 (CD4) count in the era of antiretroviral therapy (ART). This has reduced the incidence of HIV retinopathy, thus raising the question of the integrity of the retinal morphology in NIPLHIV with longer life expectancy.

PURPOSE

The study assessed the retinal thickness and volume of NIPLHIV without retinitis on ART and attempted to find associations with linear parameters of cerebral atrophy.

METHODS

The study was conducted at a public hospital in South Africa. All people living with HIV were on ART with CD4 counts above 350 cells/mm3 and viral loads less than 10,000 copies/mL. The Heidelberg Spectralis ocular coherence tomographer assessed the retinal thickness and volume for comparison between 30 NIPLHIV and 30 HIV-negative participants. A subset of the HIV group obtained a computed tomography scan to determine the bicaudate ratio and the sylvian fissure ratio to assess cerebral atrophy. Independent t tests were performed to identify differences in retinal thickness and volume. Multivariate linear regressions measured associations between retinal thickness and volume with cerebral atrophy.

RESULTS

The NIPLHIV group had a thicker mean global temporal subfields at Early Treatment Diabetic Retinopathy Study (ETDRS) 3 mm (P = .047) and ETDRS 6 mm (P = .03). The mean global temporal subfield volume at ETDRS 3 mm was also increased in the NIPLHIV group (P = .02). Nasal macula retinal nerve fiber layer thickness and the inferior inner nuclear layer macula volume were directly related to the bicaudate ratio, whereas the volumes at the outer retinal layer subfields of the macula were inversely related to sylvian fissure ratio in NIPLHIV.

CONCLUSIONS

Macula thickness and volumetric differences do exist in NIPLHIV. Practitioners should keep NIPLHIV under retinal morphometric surveillance because they live longer. Associations of cerebral atrophy with retinal morphology may be used to monitor cerebral atrophy in NIPLIV on ART.

THE THICKNESSES OF CHOROID, MACULAR SEGMENTS, PERIPAPILLARY RETINAL NERVE FIBER LAYER, AND RETINAL VASCULAR CALIBER IN HIV-1-INFECTED PATIENTS WITHOUT INFECTIOUS RETINITIS

PURPOSE

To evaluate choroidal, macular, peripapillary retinal nerve fiber layer (RNFL) thicknesses and retinal vascular caliber alterations in HIV-1-infected patients without opportunistic infections.

METHODS

This cross-sectional study included 45 HIV-1-infected patients and 47 healthy subjects. Spectral domain optical coherence tomography was used for assessment of choroidal, macular, peripapillary RNFL thicknesses and retinal vascular caliber alterations.

RESULTS

The mean CD4 count was 426 ± 226 cells per milliliter and the mean HIV-1 RNA level was 1.8 × 10 ± 3.6 × 10 copies/mL in HIV-infected group. Central inner plexiform, superior photoreceptor, superior and nasal retinal pigment epithelium layers were thinner in HIV-infected patients compared with control subjects (P < 0.05). The differences in sectoral retinal thicknesses lost their significance after Bonferroni correction (P < 0.01). The average thickness of pericentral retina within 3 mm was thinner in the photoreceptor layer in HIV-infected patients compared with control subjects (P = 0.033). The differences in peripapillary RNFL thickness, choroidal thickness, and retinal vascular caliber were not significant between the groups. Choroidal thickness and pericentral outer plexiform were thinner, whereas peripapillary RNFL was thicker in newly diagnosed cases (16 patients) compared with patients having treatment for at least 4 months or longer (27 patients, P < 0.05, Mann-Whitney U test). HIV-1 RNA showed negative correlation with choroidal thickness (r = -0.435, P = 0.003) and positive correlation with peripapillary RNFL in central (r = 0.323, P = 0.032) and superonasal (r = 0.369, P = 0.014) sectors.

CONCLUSION

Choroidal thickness was thinner in newly diagnosed patients compared with patients on treatment. Viral load showed negative correlation with choroidal thickness. Retinal segmental alterations occurred in HIV-infected patients compared with control subjects.

Dominant mutations in mtDNA maintenance gene SSBP1 cause optic atrophy and foveopathy

Mutations in genes encoding components of the mitochondrial DNA (mtDNA) replication machinery cause mtDNA depletion syndromes (MDSs), which associate ocular features with severe neurological syndromes. Here, we identified heterozygous missense mutations in single-strand binding protein 1 (SSBP1) in 5 unrelated families, leading to the R38Q and R107Q amino acid changes in the mitochondrial single-stranded DNA-binding protein, a crucial protein involved in mtDNA replication. All affected individuals presented optic atrophy, associated with foveopathy in half of the cases. To uncover the structural features underlying SSBP1 mutations, we determined a revised SSBP1 crystal structure. Structural analysis suggested that both mutations affect dimer interactions and presumably distort the DNA-binding region. Using patient fibroblasts, we validated that the R38Q variant destabilizes SSBP1 dimer/tetramer formation, affects mtDNA replication, and induces mtDNA depletion. Our study showing that mutations in SSBP1 cause a form of dominant optic atrophy frequently accompanied with foveopathy brings insights into mtDNA maintenance disorders.

The long-term effect of human immunodeficiency virus infection on retinal microvasculature and the ganglion cell-inner plexiform layer: an OCT angiography study

PURPOSE

To investigate the long-term effect of HIV infection on the ganglion cell-inner plexiform layer and retinal capillary network.

METHODS

This prospective, cross-sectional case-control study included 45 HIV-infected patients and 45 healthy individuals. Optical coherence tomography angiography (OCTA) was used for the assessment of macular, peripapillary retinal nerve fiber layer (RNFL) thicknesses, ganglion cell-inner plexiform layer, vessel density, perfusion density, and foveal avascular zone.

RESULTS

The mean disease duration was 7.3 ± 1.9 years (range, 5-12 years) in the HIV group. The mean CD4 count (nadir) for all the patients was 147.09 ± 122 cells/mm³ and the mean RNA was 173.6 ± 913.8 copies/ml. No statistically significant difference was determined between the groups in respect of the average and foveal MT (p = 0.05). A significant difference was found between the two groups in respect of the mean VD and PD parameters (p < 0.05). Peripapillary PD was significantly decreased in the HIV group. There was a significant difference between the average and superior and inferior half-region of GC-IPL values. Using Pearson's correlation analysis, no significant correlation was determined between the duration of HIV infection and mean GC-IPL, MT and VD, and PD values (r - 0.223, p 0.141; r - 0.223, p 0.141; r - 0.169, p 0.268; r - 0.105, p 0.491; r - 0.095, p 0.535 respectively).

CONCLUSIONS

The results of this study provide evidence of microvascular and neuroretinal loss in individuals with well-suppressed HIV infection, compared with healthy control subjects. OCTA is an important test for the screening of retinal microvascular changes over time in HIV-infected cases.

Absence of peripapillary retinal nerve-fiber-layer thinning in combined antiretroviral therapy-treated, well-sustained aviremic persons living with HIV

Purpose

To compare peripapillary retinal nerve-fiber–layer (pRNFL) thickness, total retina macular volume, and ganglion-cell-layer (GCL) macular volume and thickness between persons living with HIV (PLHIVs) with well-controlled infections and good immune recovery, and sex- and age-matched HIV-uninfected controls (HUCs).

Methods

This prospective cross-sectional study (www.clinicaltrials.gov identifier: NCT02003989) included 56 PLHIVs, infected for ≥10 [median 20.2] years and with sustained plasma HIV-load suppression on combined antiretroviral therapy (cART) for ≥5 years, and 56 matched HUCs. Participants underwent spectral-domain optical coherence tomography (SD-OCT) with thorough ophthalmological examinations and brain magnetic resonance imaging (MRI). Their overall and quadrant pRNFL thicknesses, total macular volumes, and GCL macular volumes and thicknesses were compared. Cerebral small-vessel diseases (CSVD) complied with STRIVE criteria.

Results

Median [interquartile range, IQR] ages of PLHIVs and HUCs, respectively, were 52 [46–60] and 52 [44–60] years. Median [IQR] PLHIVs’ nadir CD4+ T-cell count and current CD4/CD8 T-cell ratio were 249/μL [158–350] and 0.95 [0.67–1.10], respectively; HIV-seropositivity duration was 20.2 [15.9–24.5] years; cART duration was 16.8 [12.6–18.6] years; and aviremia duration was 11.4 [7.8–13.6] years. No significant between-group pRNFL thickness, total macular volume, macular GCL-volume and -thickness differences were found. MRI-detected CSVD in 21 (38%) PLHIVs and 14 (25%) HUCs was associated with overall thinner pRNFLs, and smaller total retina and GCL macular volumes, independently of HIV status.

Conclusions

SD-OCT could not detect pRNFL thinning or macular GCL-volume reduction in well-sustained, aviremic, cART-treated PLHIVs who achieved good immune recovery. However, CSVD was associated with thinner pRNFLs and GCLs, independently of HIV status.

The role of optical coherence tomography in therapeutics and conditions, which primarily have systemic manifestations: a narrative review

Optical coherence tomography is designed to evaluate in vivo qualitative and quantitative changes of the anterior segment, optic nerve and the retina. Initial applications of this technology were confined mainly to ophthalmic diseases. However recently, numerous studies have evaluated its use in systemic conditions and in therapeutics where, optic nerve and retinal architecture can be assessed to monitor progression of systemic conditions and its response to treatment. This is a narrative review aimed at evaluating the debate surrounding the role of spectral domain optical coherence tomography, in systemic conditions where optic nerve affection can be measured and be used in the diagnosis, monitoring and assessment of treatment effect as a non-invasive, quick, novel technique.

Correlation between inner retinal layer thickness and cognitive function in HIV: new insights from an exploratory study

OBJECTIVE

To compare retinal layer thickness in HIV-infected subjects with (CI-HIV) and without (NCI-HIV) cognitive impairment, with a control population and to correlate this with the cognitive status of the patient and other clinical parameters.

DESIGN

Single-center cross-sectional study.

METHODS

Participants with controlled HIV infection aged between 40 and 70 years and sex-matched and age-matched controls were enrolled. Retinal nerve fiber layer (RNFL), ganglion cell layer (GCL) and inner plexiform layer (IPL) thickness were assessed using optical coherence tomography. These measurements in HIV patients were compared with those in controls. Age-related and sex-related changes were compared in both groups. Other variables studied in HIV patients included: duration of HIV infection, CD4 cell count nadir, antiretroviral therapy regimen and cognitive status using the Montreal Cognitive Assessment (MoCA) test.

RESULTS

Sixty-nine individuals, 34 with and 35 without cognitive impairment, and 70 controls were enrolled. GCL was significantly thinner in CI-HIV patients compared with NCI-HIV patients and controls (P = 0.01 and P = 0.02, respectively). GCL and IPL thickness significantly decreased with age in patients with HIV (P = 0.0003, P = 0.02, respectively, for the entire cohort). This change was not seen in controls. MoCA test score significantly decreased with age in HIV patients and controls. GCL thickness positively correlated with cognitive function across the entire HIV cohort (P = 0.02).

CONCLUSION

GCL was thinner in HIV patients with cognitive impairment. GCL thickness correlated positively with cognitive function and negatively with age in HIV patients. GCL thickness may reflect accelerated cognitive aging in HIV.

Normative Data for Retinal-Layer Thickness Maps Generated by Spectral-Domain OCT in a White Population

PURPOSE

(1) To collect a dataset of normative Early Treatment Diabetic Retinopathy Study (ETDRS) thickness map values for single retinal layers automatically segmented by Spectralis (Heidelberg Engineering, Heidelberg, Germany) spectral-domain OCT (SD-OCT) in a healthy white population. (2) To test the effect of age, sex, and axial length (AXL) on such values.

DESIGN

Cross-sectional study.

SUBJECTS

Healthy adult emmetropic white subjects with no history of ongoing or past conditions known to affect retinal anatomy.

METHODS

SD-OCT scans (30 × 25-degree volume) centered on the fovea were collected. Retinal-layer automatic segmentation was performed. Mean thickness values of 9 ETDRS sectors were calculated for each layer in 1 eye from each subject. The effect of age, sex, and AXL on the thickness of the central subfield, inner ring (IR), and outer ring (OR) of the ETDRS grid was tested. Scans were performed twice on a subset of patients to assess the repeatability of measurements.

MAIN OUTCOME MEASURES

Retinal-layer thickness.

RESULTS

Two hundred eyes from 200 subjects (110 females, mean age 39.9±13.9 years [range 20-74 years]) were used for this study. The mean AXL was 24.30±1.07 mm (range 22.23-27.14 mm). Full retinal thickness was higher in males regardless of the subfield (all P < 0.05). Ganglion cell layer thickness correlated positively with AXL in the C (P = 0.02) but negatively in the OR (P = 0.0001). The inner plexiform layer was thicker in males in the IR (P = 0.01) and thinner in longer eyes in the OR (P = 0.002). The inner nuclear layer was thicker in males in the C and the IR (P = 0.002 and P = 0.0009, respectively). The outer plexiform layer thickness did not change with age and gender but correlated positively with AXL in the C (P = 0.009). Males had thicker outer nuclear layers in all subfields (all P < 0.05). The thickness of the nerve fiber layer and retinal pigment epithelium was not affected by the studied variables in any subfield. The intraclass correlation coefficient ranged from 0.872 for the outer plexiform layer to 0.990 for the retinal nerve fiber layer and the ganglion cell layer.

CONCLUSIONS

The thickness values of each retinal layer in a large white population are provided. The thickness of retinal layers is influenced by gender, sex, and AXL, with a variable extent depending on the analyzed ETDRS map ring.

Study of Retinal Nerve Fibre Layer Thickness and Visual Contrast Sensitivity in HIV Positive Individuals

INTRODUCTION

Measurement of Retinal Nerve Fibre Layer Thickness (RNFLT) by Optical Coherence Tomography (OCT) is a sensitive, non invasive and cheap method of detecting early retinal changes in a variety of diseases. In HIV infection, RNFLT is altered and this may have effect on other visual functions like Contrast Sensitivity (CS) and visual acuity. Such ocular pathology can affect the daily life and profession (especially driving) of HIV infected individuals. However, studies on this topic in HIV infected population are rare from India.

AIM

To study RNFLT, CS and their correlation in a sample of HIV positive Indian population.

MATERIALS AND METHODS

The present cross-sectional study was done in a tertiary care medical college hospital of Eastern India between May 2016 and September 2016. We did this study on HIV positive subjects with no clinically apparent ocular infection or other pathology. In this study, we have measured the RNFLT using the HRA-OCT Spectralis machine. The CS was tested using a smartphone version of the Pellie-Robson chart. CD4 count, visual acuity and colour vision were also tested. The data was analysed using SPSS version 20.0 for any correlation between these parameters. Pearson coefficient was used for continuous data and Spearman rank correlation was used for categorical data. A p-value <0.05 was considered significant.

RESULTS

We had 17 patients, that is 34 eyes. RNFLT loss was found in 21% of the eyes and borderline thinning was found in a further 26%. Predominantly, the temporal quadrant was involved. The mean of log CS was 1.33±0.38. Taking 1.5 as the cut-off value for normalcy, 47% of the eyes tested showed decreased CS. Log CS showed significant correlation with RNFLT of the temporal quadrant only (r=0.37; 95% C.I. 0.041 to 0.631; p=0.02). Temporal RNFLT also showed statistical correlation with the CD4 count. The low CS was also significantly correlated with low visual acuity (r=0.5).

CONCLUSION

In HIV infected persons, subtle ocular changes may occur and this may affect visual functions quite early. Hence, a comprehensive eye check-up should include parameters like CS and OCT.

Hessian-LoG filtering for enhancement and detection of photoreceptor cells in adaptive optics retinal images

Automated analysis of retinal images plays a vital role in the examination, diagnosis, and prognosis of healthy and pathological retinas. Retinal disorders and the associated visual loss can be interpreted via quantitative correlations, based on measurements of photoreceptor loss. Therefore, it is important to develop reliable tools for identification of photoreceptor cells. In this paper, an automated algorithm is proposed, based on the use of the Hessian-Laplacian of Gaussian filter, which allows enhancement and detection of photoreceptor cells. The performance of the proposed technique is evaluated on both synthetic and high-resolution retinal images, in terms of packing density. The results on the synthetic data were compared against ground truth as well as cone counts obtained by the Li and Roorda algorithm. For the synthetic datasets, our method showed an average detection accuracy of 98.8%, compared to 93.9% for the Li and Roorda approach. The packing density estimates calculated on the retinal datasets were validated against manual counts and the results obtained by a proprietary software from Imagine Eyes and the Li and Roorda algorithm. Among the tested methods, the proposed approach showed the closest agreement with manual counting.