الفهرس 
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Abstract
Retinitis pigmentosa (RP) is a group of inherited disorders characterized by progressive peripheral vision loss and night vision difficulties (nyctalopia) that can lead to central vision loss.
RP is typically thought of as a rod-cone dystrophy in which the genetic defects cause cell death (apoptosis), predominantly in the rod photoreceptors; less commonly, the genetic defects affect the RPE and cone photoreceptors. RP has significant phenotypic variation, as there are many different genes that lead to a diagnosis of RP, and patients with the same genetic mutation can present with very different retinal findings. The final common pathway remains photoreceptor cell death by apoptosis in the mid-peripheral retina. The first histologic change found in the photoreceptors is shortening of the rod outer segments, followed by loss of the rod photoreceptor. This occurs most significantly in the mid periphery of the retina. These regions of the retina reflect the cell apoptosis by having decreased nuclei in the outer nuclear layer.
With advances in molecular research, it is now known that RP constitutes many retinal dystrophies and retinal pigment epithelium (RPE) dystrophies caused by molecular defects in more than 40 different genes for non-syndromic (isolated) RP and more than 50 different genes for syndromic RP.
We aim in this study to measure corneal parameters in patients of retinitis pigmentosa by use of pentacam for detectionof keratoconus and myopia which are some of ocular associations in RP and regular follow-up of patients with RP is ssentials to evaluate vision-threatening complications, some of which may be amenable to treatment.
One hundred and sixty eyes of eighty randromely selected Egyptian healthy subjects, 44 males and 36 females, ranging from 25 to 56 years old, were included in the study during the period from March 2017 to May 2018 at the Al Rowad Eye Center and Roaa Eye Center. All participants were informed of the goals and implications in which they were taken part and their verbal consents were taken.
All participants in this study had been examined by full ophthalmological examination and Measurement of their corneal parameters by using PentacamScheimpflug Camera
The Pentacam is a combined device consisting of a slit illumination system and a Scheimpflug camera which rotates around the eye. A thin layer within the eye is illuminated through the slit. Being not entirely transparent the cells scatter the slit light. In doing so they create a sectional image which is then photographed in side view by a camera. This camera is oriented according to the Scheimpflug principle, thus creating an image of the illuminated plane which appears completely sharp from the anterior surface of the cornea right up to the posterior surface of the crystalline lens.
Data were available for 80 patients of retinitis pigmentosa included in the study which entered into statistical analysis and this analysis showed that studied patient’s age ranged between 25 and 56 years with mean of 39.4 years and standard deviation of 8.4, 55% were males,45% were females
We found as regard pentacam data of studied patients that OD K1 ranged between 41 and 45 with mean of 42.9 and standard deviation of 1.3, K2 ranged between 41 and 46.1 with mean of 43.9 and standard deviation of 1.5 and as regard pachymetry ranged between 486 and 534 with mean of 510.4 and standard deviation of 14.5.
As regard OS characteristics it was found that K1 was ranged between 40 and 45.4 with mean of 43 and standard deviation of 1.4, K2 ranged between 41 and 47.1 with mean of 44.3 and standard deviation of 1.7 and as regard pachymetry ranged between 487 and 536 with mean of 513.3 and standard deviation of 15.2.
We found as regard OD corneal anterior surface elevation ( front elevation) characteristics that it was normal in 97.5% of studied patients and abnormal in 2.5% and Corneal posterior surface elevation( back elevation ) was normal in 93.8% and abnormal in 6.2%. It was found that OS corneal anterior surface elevation ( front elevation) was normal in 93.8% and abnormal in 6.2% and OS corneal posterior surface elevation( back elevation ) it was abnormal in 21.2% of studied patients and normal in 78.8%.
The majority of cases of this study have normal pentacam corneal parameters; so it is concluded from this study that keratoconus is uncommon in RP.