Cone Dystrophies: An Optical Coherence Tomography Angiography Study

Abstract

Background: This study investigates the relationship between retinal vascularization and macular function in patients with cone dystrophies (CDs). Methods: Twenty CD patients (40 eyes) and 20 healthy controls (20 eyes) were enrolled in this prospective case-control study. Patients underwent full ophthalmological examination, microperimetry, full-field, pattern and multifocal electroretinogram (ERG, PERG, mfERG) and optical coherence tomography angiography (OCTA). Main outcome measures were as follows: foveal and parafoveal inner and outer retinal thickness; microperimetry sensitivity in the central 4° and 8°, ERG b wave amplitudes and peak times, PERG P50 and N95 amplitudes and latencies, and mfERG N1 to P1 amplitudes; and superficial capillary plexus (SCP), deep capillary plexus (DCP) and choriocapillary (CC) plexus vessel densities, divided into foveal and parafoveal region. Results: Retinal thickness, SCP and DCP densities were significantly related to PERG. A significant relationship was found between foveal and parafoveal retinal thicknesses and foveal SCP density (p < 0.001 and p = 0.018, respectively) and between parafoveal retinal thickness and parafoveal SCP density (p = 0.002). Foveal and parafoveal retinal thicknesses were significantly related to parafoveal DCP density (p = 0.007 and p < 0.001). Foveal and parafoveal retinal thicknesses, foveal SCP and parafoveal DPC densities were significantly reduced in CD patients compared to controls (p < 0.001; p = 0.010 and p = 0.008, respectively). PERG and mfERG amplitudes were significantly reduced in CD patients compared to controls (p < 0.01). Conclusions: CD eyes showed reduced retinal thickness significantly related to reduced vessel density, possibly caused by a decreased metabolic demand. In addition, vessel density significantly correlated with loss of function.

Case Report: Multimodal Imaging Features of an ABCA4 Cone Dystrophy

“…In ABCA4-associated cone dystrophy/ cone-rod dystrophy, symptomatic onset usually occurs in childhood with a rapidly progressing macular atrophy, and the majority of patients have rod involvement at presentation (cone-rod dystrophy), which is associated with a worse prognosis. 3,5 Our patient differed from this typical phenotype associated with ABCA4 in that her onset symptoms started at her late twenties without rod involvement and her macular atrophy is progressing slowly.…”

“…Full-field photopic white flash electroretinogram is considered the criterion standard for its diagnosis because this testing protocol reveals marked depression of cone responses with normal rod function; the test can also reveal the onset of late rod involvement. 1,5 The age of onset, degree of cone/rod dysfunction, and funduscopic appearance are diverse, partly because many genetic causes are related to this disorder. The disease-causing gene identified in 56.3% of the affected patients shows that the most frequent form of inheritance is autosomal recessive, with variants in the ABCA4 gene accounting for 62.2% of autosomal recessive cone dystrophy/cone-rod dystrophy cases.…”

Optical Coherence Tomography Angiography in CRB1-Associated Retinal Dystrophies

“…Interestingly, the severity of the vessel density reduction was similar across the different phenotypical manifestations, which ranged from mere RPE mottling up to large atrophic changes, suggesting that this peripapillary vascular impairment is independent of the stage of the disease. Even though the comparison of the OCTA findings described in other IRDs is hard due to the different pathogenesis of each subform, we have to underline that DCP is always involved, often also showing a correlation with BCVA [12][13][14][15][16][17][18][19][20][21]. Thus, DCP may represent an important biomarker to better characterize the stage of the disease and the extent of functional damage.…”

“…Optical coherence tomography angiography (OCTA) has been used in several IRDs to characterize the vascular anatomy in the macula and to identify vascular patterns associated with a faster progression. In particular, a reduction in vessel density at the level of the deep capillary plexus (DCP) has been described in several IRDs, including Stargardt disease [12], cone dystrophies [13], Best vitelliform macular dystrophy [14], X-linked retinoschisis [15], choroideremia [16], occult macular dystrophy [17], congenital stationary night-blindness [18], retinitis pigmentosa [19,20], and Bietti crystalline dystrophy [21]. This study aimed to describe the OCTA features in eyes affected by CRB1-associated retinal dystrophies, as no prior study has explored the vascular alterations in these disorders.…”

Choroidal and Retinal Vascular Findings in Patients with COVID-19 Complicated with Pneumonia: Widefield Imaging

“…The projection-resolved algorithm was used to eliminate projection artifacts. This algorithm retains flow signals from blood vessels and suppresses projected flow signals in deeper layers [ 24 ].…”