This study was planned to investigate the relationship between Electro-physiological diagnostic studies (EDTs) as an assessment of visual function and the clinical findings and measurements of eyes in patients with Microphthalmia. In this retrospective study of case notes, we included 62 patients (81eyes) in which a diagnosis of Microphthalmia was established. These patients were reviewed and followed in Ophthalmology and Electrophysiology departments at Great Ormond Street Hospital and Moorefield’s Eye Hospital-London during the period from 2001 to 2010. The following data was recorded for each patient: age, gender, visual acuity (V/A) at presentation and last review, axial length (A/L), horizontal corneal diameter (HCD), anterior/posterior segments findings, associated systemic Problems/syndromes, genetic background and EDTs outcome. The study was approved by the Research and Development department, and followed the official ethical regulations for clinical research and patients’ data protection. There were 62 patients (81 eyes): 34 females and 28 males. The mean age at presentation was 26.04 months (range 1 week-11 years) (6 above age of 3 years). 20 (32%) of them had bilateral Microphthalmia and 42 (68%) had unilateral Microphthalmia. The mean age at presentation in the bilateral group was 45.53 months and that for the unilateral group, 17.43 months. Formal measurement of visual acuity was difficult due to the young age of the patients especially in those below the age of 18 months. In these younger children the majority V/A was recorded as fixing and following light (79%). AL was recorded in 24 affected eyes of 20 patients (30%) with range 5.2mm to 20 mm in affected eye. HCD value was obtained in 30 patients (48%) with range 4.5mm to 10.5mm. As for all the patients, the clinical findings were compared to EDTs outcome. Based on the results, we can conclude that in microphthalmic eyes, there is no correlation between how small the eye is and the corneal diameter especially that in some cases the pathology can be confined to the posterior segment sparing the anterior segment completely. Our results show that ERG have strong positive association with AL; Patients with normal ERG tend to have AL of ≥14mm, which can be considered as suggestive axial length of indication of vision potential in the microphthalmic eye.