Prospective, interventional, non-randomized study conducted at the VISSUM Ophthalmology Institute in Alicante, Spain. Ethical committee approval was obtained for the purpose of this prospective investigation. The study followed the tenets of the Declaration of Helsinki , and adequate informed consent was obtained from all patients included in the study.
Adult patients with moderate to severe chronic DED (for 6 months or more)—according to the Dry Eye severity grading scheme proposed by the Dry Eye WorkShop (DEWS)  and Baudouin et al. —were included in the study. This scheme takes into account the following parameters: ocular discomfort, visual symptoms, conjunctival injection, conjunctival and corneal fluorescein staining (CFS), corneal/tear signs, lid/meibomian glands, tear film break-up time (TBUT), and Schirmer test score .
Patients with previous ocular refractive surgery (LASIK, LASEK, or PRK), inability to attend the 6th week follow-up visit and patients who did not complete the follow-up protocol were excluded.
Any topical medication used formerly by the patient for the treatment of the DED was stopped 48 h before starting PRP treatment. Treatment consisted of monotherapy with PRP eye drops used on both eyes, one drop six times per day for at least 6 consecutive weeks (one round). When the improvement was initially poor or not satisfactory enough, some patients needed more than one round of PRP treatment.
Treatment response was evaluated by the results of the subjective questionnaires, the slit lamp examination and BCVA.
Main Outcome Measures
Patients were classified as evaporative DED (EDED) or aqueous deficient DED (ADDED) according to the criteria presented by Lemp et al. , in which by using the most severe measurement of both eyes, subjects were considered to have pure aqueous-deficient dry eye (ADDED) with Schirmer’s test values of <7 mm and MGD grades of ≤5, whereas patients with Schirmer’s values of ≥7 mm and MGD grades of >5 were classified as purely evaporative dry eye .
Subjective symptoms were evaluated based on the ocular surface disease index (OSDI) self-administered questionnaire, which was completed once at the time of enrollment in the study (baseline) and again after treatment with E-PRP. OSDI scores range from 0 to 100 according to the severity of the DED symptoms. Patients were also directly asked to report any change in their perception of ocular redness, foreign body sensation, itching, photophobia, dryness, and pain, based on a five-point scale in which 0 = no change, 1 = slight improvement, 2 = moderate improvement, 3 = very good, and 4 = excellent.
Best corrected distance visual acuity (BCVA) was measured with Snellen charts on a conventional projection screen with far distance correction and without using any eye drops 1 h before measurement. Conversion to decimal scale and lines of vision were posteriorly done to compare results.
Corneal fluorescein staining (CFS) was used to evaluate corneal superficial punctate epithelial keratitis. The modified Oxford scale, ranging from 0 (no staining dots) to 5 (worst staining condition), was used for this purpose. A decrease in CFS scores in at least one quadrant to total disappearance from baseline indicated improvement .
Autologous PRP Preparation
Autologous PRP was prepared according to the protocol described by our group in a previous study . The patient’s blood was extracted into 10-mL sterile tubes containing 1 mL sodium citrate acting as an anticoagulant. Centrifugation of total blood at optimal condition was used to achieve enrichment of platelets in plasma fraction. Under a laminar flow cabin, 3–4 mL of platelet-rich plasma was aspirated and put into sterilized amber glass bottles with eye drop applicators. A haemocytometer (Mythic 18, Domenech, Madrid, Spain) was used to quantify the number of platelets in whole blood after the centrifugation in order to obtain the maximum enrichment. Patients were instructed to maintain good personal hygiene: to wash their hands before the application of the product, keep the area of the application clean and not touch the eye dropper. The bottle in use should be kept at +4–8 °C for 1 week and the remaining bottles at −20 °C.
An independent observer followed up each case. Data were recorded for the purpose of this report at the initial visit, and at the end of each round of 6 weeks of monotherapy treatment. Follow-up visits included an interview with the patient assessing the presence of ocular symptoms, and ophthalmologic examination to register all the clinical findings. Improvement or failure was assessed according to the criteria described above.
Shapiro–Wilk test was used to study the normal distribution of the data. When the parameters analysed were quantitative variables (mean and standard deviations) we used paired 2-tailed Student t test or the Wilcoxon matched-pairs test. For qualitative variables descriptive statistics were used. The statistical significance level chosen was p ≤ 0.05. Correlations were performed using the non-parametric Spearman test. Microsoft Office Excel 2010 and SPSS 13.0 package were used for analysis of data.