Int J Clin Exp Med 2018;11(11):11949-11956 www.ijcem.com /ISSN:1940-5901/IJCEM0070339 Original Article A preliminary study on the peripheral retinal refractive status and the development of myopia in RP patients with myopia Shuang-Shuang Zhou1*, Zhou Zhou2*, Qiu-Xia Xie1, Yi Shao3, Zheng Yang4, An-Hua Wu1, Xue-Xiang Zou1, Ying Zhou1, Gang Tan1 1Department of Ophthalmology, The First Affiliated Hospital of University of South China, Hengyang 421001, Hunan Province, China; 2Medical College, University of South China, Hengyang 421001, Hunan Province, China; 3Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Oph- thalmology Institute, Nanchang 330006, Jiangxi Province, China; 4Department of Cardiology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou 510080, Guangdong Province, China. *Equal contributors. Received December 4, 2017; Accepted September 5, 2018; Epub November 15, 2018; Published November 30, 2018 Abstract: Purpose: To study the relationship between peripheral retinal refraction and the development of myopia in retinitis pigmentosa patients with myopia. Methods: A total of 47 subjects (89 eyes) of RP patients with different degrees of myopia underwent peripheral refraction and visual field measurement. The visual field test results were grouped according to the AGIS scoring system, and classified into mild visual field defect group (24 eyes), moder- ate visual field defect group (41 eyes), and severe group (24 eyes). According to shadow moving, neutralization in the open view field condition, relative peripheral refractive errors (RPREs) were measured in the center and at the stare angles of 10°, 20° and 30° in the nasal and temporal fields, respectively. A complete set of data for each eye included one central diopter and six peripheral diopters. The RPREs of the nasal and temporal fields at 10°, 20° and 30° were determined by subtracting each peripheral diopter from central diopter, RPRE = Ma-M0, a is central diopter, o is peripheral diopter. Results: The relative refractive errors of temporal fields between mild and moderate group were significantly different at temporal field eccentricities of 20° and 30° (Independent-samples t-tests,P = 0.01, 0.004). The peripheral hyperopia state was positively correlated with the degree of visual field damage. In mild to moderate group, there was also a positive correlation between peripheral hyperopia state and visual field dam- age degree (P = 0.012, <0.05). Conclusion: For RP patients with myopia, there was a positive correlation between peripheral hyperopia state and retinal damage when the damage was mild. For the severe retinal damaged group, the central diopter did not correlate with the peripheral retinal damage. Keywords: Retinitis pigmentosa (RP), myopia, peripheral refraction, visual field Introduction visual signals from the central retina [4], the peripheral refractive state has a significant With the application of electronic products, impact on emmetropization at the fovea [5]. refractive errors have become the most com- Retinitis pigmentosa (RP) is a group of retinal mon eye diseases. However, the pathogenesis diseases caused by gene mutations that result of myopia is unclear [1]. Genetic studies dem- in retinal atrophy. It has been shown that RP onstrate that, the genomic loci of high myopia patients tend to have high myopic errors and causative genes are proximal to those of RP. high astigmatic errors [11]. The retinal degen- Clinically, genetic RP is usually combined with eration process of RP patients starts from the high myopia [2]. A large number of animal and peripheral retina to the macula, which causes clinical studies demonstrate that peripheral changes of peripheral vision and peripheral refractive state have a substantial impact on refraction state in the beginning, and expands emmetropization, resulting in the onset and to the central retina gradually, similar to the progression of myopia [3-10]. Compared to development of myopia. Whether the change of Refractive status in RP patients D) was 50.6% and mild myo- pia was 17.9% (≤-3.00 D). Refraction examinations All patients were examined with YZ24 ribbon shape light- ing skiascope (Suzhou sixty- six) and Humphrey720i perim- eter (Germany Zeiss). Basic refraction examinations inclu- ded subjective refraction and auto-refraction. The visual ac- tivity, refraction and best-cor- rected visual acuity (BCVA) were recorded. Peripheral re- fraction state was measured by streak retinoscopy, a com- mon method to measure the refractive errors. It is based Figure 1. Outline of study procedures. on shadow moving neutraliza- tion lens selection [12]. Mea- peripheral refraction state of sporadic RP surements with the subjects turning their eyes patients leads to myopia is unclear and war- and fixating on the object in the nasal and tem- rants detailed characterization. Our study retro- poral fields at 10°, 20°, and 30° angles were spectively collected and analyzed data from recorded sequentially, under the condition of sporadic RP patients associated with myopia, an open visual field. Each subject was instruct- and investigated the relationship between the ed to stay steady to avoid any head movement, peripheral retinal refraction state and the open the pupil with diameter greater than 4 development of myopia. mm, and stare at a cross Maltese object at 2.5 m distance (the size of the cross Maltese object Materials and methods was 25 cm×20 cm, contrast was greater than 80%) at 10° intervals from nasal 30° to tempo- Subjects ral 30° visual fields. According to the neutral condition of shadow moving, peripheral refrac- A total of 47 RP patients (89 eyes) with differ- tive errors were measured at the visual angle of ent degrees of myopia who visited the Eye 10°, 20°, and 30°, respectively. Center of the First Affiliated Hospital of University of South China from March, 2014 to Each measurement was calculated as the arith- May, 2016 were recruited in the study. Patients metic mean of three replicates. For each visual with other known ocular diseases such as cata- angle, a complete set of data for each eye ract, glaucoma, corneal diseases or blind and included one CR and six PR. The relative periph- systemic disease or previous surgery history eral refractive error (RPRE) was determined by were excluded. Outline of study procedures subtracting each peripheral refractive (PR) with shown in Figure 1. Among these patients, there central refractive (CR) measurement (RPRE = were 36 patients (76.6%) with binocular RP and M -M , a is CR, o is PR) [13]. 7 patients (7.8%) with monocular RP. Patients a 0 ranged in age from 30 years old to 40 years old, Visual field examination with a mean age of 33.94±2.16 years; 61.7% of the patients were men (n = 29) and 38.2% were Visual field tests were conducted with a women (n = 18). Moreover, there were 58.5% Humphrey720i perimeter using the central patients with uncorrected visual acuity (UCVA) 30-2 threshold test with SITA standard thresh- less than 0.1 and 2.2% greater than or equal to old strategy. Subjects stayed in a darkroom for 0.3. The percentage of high myopia (≥-6.00 D) 5~10 min before examination to ensure the was 31.4%, moderate myopia (-3.00 D~-6.00 pupil diameter greater than 4 mm. Tests were 11950 Int J Clin Exp Med 2018;11(11):11949-11956 Refractive status in RP patients al field defect; 4th stage: 12-17, severe visual field defect; 5th stage: 18-20 points: absolute visual field defect. According to inclusion and exclusion criteria, 24 eyes (26.97%) were mild visual field defect, 41 eyes (46.06%) were moderate visual field defect, and 24 eyes (26.97%) were severe visual field defect. Figure 2. The ratio of different myopic degree in mild, moderate and severe Statistical analysis visual field defect group visual field defect groups. Data were analyzed with the statistical software PASW Statistics 18.0. Independent samples t-tests were used to compare the central refrac- tion, AGIS scores, and the RPRE values between mild visual field defect group and moderate group, and between moderate group and severe visual field defect group. The peripheral refractive state between the nasal fields and temporal fields from two groups were analyzed by Figure 3. The value of refractive errors (M) from mild, moderate and severe Paired t-tests. The difference visual field defect group at temporal field eccentricities of 10° (T10°), 20° was statistically significant (T20°) and 30° (T30°), at the 10° (N10°), 20° (N20°), and 30° (N30°) nasal field eccentricities. when P values were less than 0.05. adjusted with appropriate correction lens Results based on the patient’s refractive status and age. There was a 30 minute break between As illustrated in Figure 2, in the mild visual field examinations. All patients were examined three defect group, mild myopia accounted for about or more times. Excluding two test sites above 50%, moderate myopia was 37.5%, and high and below the physiologic blind spot, there myopia was 12.5%. In the moderate group, mild were a total of 74 test sites for analysis. The myopia was 7.3%, moderate myopia was visual field test results were grouped according 53.6%, and high myopia was 39%. In severe to the Advanced Glaucoma Treatment Study group, mild myopia accounted for 4.2%, moder- (AGIS) scoring system [14]. AGIS system was ate myopia and high myopia was 58.3% and scored by the defect depth and quantity of nor- 37.5%, respectively. In the mild visual field mal threshold in the overall deviation figure defect group, mild myopic was the major form. from the nasal visual field, the upper half visu- And moderate to severe visual field defect al-field and the bottom half visual-field visual group mainly showed moderate myopia. field tests. The scores ranged from 0 (no defect) to 20 (worst).