Temporal retinal thinning might be an early diagnostic indicator in male pediatric X-linked Alport syndrome

Abstract

Aim: To evaluate temporal retinal thinning changes in retinal layers using spectral-domain optical coherence tomography (SD-OCT) in pediatric X-linked Alport syndrome (XLAS) patients.

Methods: A retrospective case-control study. SD-OCT scans of pediatric patients diagnosed with XLAS and age- and sex-matched healthy control participants were reviewed. Automated segmentation of SD-OCT scans was induced to analyze the retinal thickness (RT) of different layers. The temporal thinning index (TTI) was calculated for each layer and compared between the patients and the control group.

Results: Forty-three pediatric XLAS patients and 60 healthy controls were included. Temporal retinal thinning was present in 33 patients (76.74%), while 28 patients (65.11%) had severe pathological temporal retinal thinning and 5 patients (11.63%) had moderate thinning. The temporal inner sector RT (P<0.0001), the temporal outer sector RT (P<0.0001), and the nasal outer sector RT (P=0.0211) were significantly thinner in the XLAS male patients. The TTI of the total retina was significantly higher in the XLAS group than in the control group (P<0.0001). The TTI of the inner retina layers (P<0.0001), ganglion cell layer (P<0.0001), inner plexiform layer (P<0.0001), inner nuclear layer (P<0.0001), and outer nuclear layer (P<0.0001) were significantly higher in the XLAS group. The central RT of the XLAS group was significantly thinner than that of the control group (P<0.0001).

Conclusion: Temporal retinal thinning appears early in XLAS patients, especially in male patients. The thinning is mainly caused by structural abnormalities of the inner retina. This suggests that temporal retinal thinning could be helpful for the early diagnosis and follow-up of XLAS with noninvasive SD-OCT examination.

Keywords: Alport syndrome; retinal thickness; segmentation; spectral domain optical coherence tomography.

Figure 1. The automated segmentation diagram

Heidelberg software segmented the retina into 11 different boundaries: the inner limiting membrane (ILM), the boundaries between the retinal nerve fiber layer and the ganglion cell layer (RNFL-GCL), the GCL and the inner plexiform layer (GCL-IPL), the IPL and the inner nuclear layer (IPL-INL), the INL and the outer plexiform layer (INL-OPL), the OPL and the outer nuclear layer (OPL-ONL), the external limiting membrane (ELM), two photoreceptor layers (PR1/2), the RPE, and Bruch's membrane (BM). Total retinal thickness (RT), inner retinal layers (IRLs), and outer retinal layers (ORLs).

Figure 2. Retinal thickness map with ETDRS grid

A retinal thickness map of the right eye. The 1-, 3-, and 6-mm diameter grid showing the areas of retina labeled with C (central retina), T1 (temporal inner sector), T2 (temporal outer sector), N1 (nasal inner sector), and N2 (nasal outer sector).

Figure 3. A representative fundus and SD-OCT scan image of an XLAS patient

A 14-year-old boy was diagnosed with AS 6 years ago, and his bilateral corrected visual acuity was 1.0. Dot-and-fleck retinopathy could be seen as yellowish dots around the macula. His lens was normal. SD-OCT scans of his retina revealed temporal retinal thinning. A: The fundus photograph of the patient showed yellowish dots around his macula; B: The B-scan of the patient showing significant temporal retinal thinning; C: The retinal thickness map of the patient.