People with Hermansky-Pudlak Syndrome and other forms of oculocutaneous albinism typically have very light sensitive eyes (‘photophobia’ ). This frequently causes discomfort and can sometimes be painful. People may partly close there eyes to avoid discomfort particularly in sunlight on a clear day or indoors under bright artificial light. It can be very difficult for someone to see where they are going when ‘peeping through a barely open eyelid.
The human eye is similar to an old style film camera (not digital). If too much light enters the camera through the lens then a distorted and over exposed image is produced on the film. If a picture is taken with the sun behind a person then they may appear as a silhouette. This also occurs in the eyes of people with HPS and albinism. To much light can enter the eyes through the pupils and irises (‘irids’). The irids of affected people lack a layer of melanin pigment (Iris pigment epithelium) and so do not filter out excess light as in normal eyes. The excess light is reflected inside the eyes causing distortion and to much light reaches the retinas This can cause a person to see a distorted and ‘over exposed’ image. Under bright light a person may see objects or faces as silhouettes and not be able to see detail or facial features. This can make it difficult for them to recognise people particularly in unfamiliar surroundings.
Light is also reflected back from the inside of the eyes and this sometimes shows as a red hue, or ‘red reflex’ that makes the eye pupils look red to onlookers. This varies with how much melanin is present in the irises (irids). The melanin is contained in a layer called the Iris Pigment Epithelium (IPE).
Eye doctors (ophthalmologists) sometimes use this feature to examine how much pigment is present in IPE. A light is shone into the eyes with either an ophthalmoscope or ‘slit lamp microscope’. When very little pigment is present the irids can appear bright red. Some people with HPS have more pigment and clumps or streaks of pigment can be seen and the iris is described as ‘punctate’. This technique is called globe transillumination.