Visual Function in Carriers of X-Linked Retinitis Pigmentosa

Area of Science:

• Ophthalmology
• Genetics
• Retinal Diseases

Background:

• X-linked retinitis pigmentosa (XLRP) is a severe inherited retinal dystrophy.
• Female carriers of XLRP often exhibit variable visual function.
• Understanding carrier visual status is crucial for genetic counseling and management.

Purpose of the Study:

• To assess the frequency and severity of visual function impairment in female carriers of XLRP.
• To investigate the relationship between genotype (RPGR/RP2 mutations) and visual phenotype in carriers.
• To evaluate the utility of electroretinography (ERG) in identifying affected carriers.

Main Methods:

• A retrospective case series involving 276 female carriers of XLRP.
• Analysis of cross-sectional and longitudinal data, including visual acuity, visual fields, dark adaptation, and full-field ERG.
• Genotyping for RPGR or RP2 mutations in a subset of participants.

Main Results:

• 40% of genotyped carriers showed baseline visual function abnormalities.
• Legal blindness due to visual acuity was rare (2%), but some carriers experienced vision loss as early as 35 years.
• Average ERG amplitudes were 50% of normal, with a slower decline rate compared to affected males, consistent with random X-inactivation.

Conclusions:

• Most XLRP carriers have mild to moderate visual dysfunction, with legal blindness being uncommon.
• ERG testing is effective in identifying obligate carriers.
• Carriers with RPGR ORF15 mutations generally exhibit poorer visual function than those with RPGR exon 1-14 mutations.