The orbit, a four-sided pyramidal bony space in the skull, measures approximately 45 ml in an adult human. It houses the eyeball along with the ocular adnexa and comprises structures derived from all three germinal layers (ectodermal, mesodermal & endodermal) as well as all the tissues (skin, muscle, connective tissue etc.) in the human body. Therefore it is not surprising that a pathology arising from any of these structures can contribute to the etiology of orbital lesions. But occasionally the orbit is affected by systemic diseases or secondarily by a disorder arising somewhere else in the body. The orbit is surrounded by, and is connected through various foramina and fissures to cranial cavity, nasal cavity and paranasal sinuses; hence diseases arising from the neighborhood can easily infiltrate the orbit and vice versa. The orbit is extensively connected to neuro-vascular system of face, head, neck and brain (particularly dural venous sinuses) and the pathologies of the orbit especially tumors spread quickly via hematogenous route in addition to local spread. True lymphatics have not been found in the orbit but involvement of regional lymph nodes by inflammatory or neoplastic lesion (probably along venous channels) has also been well documented [1] .

Orbital lesions can be classified in many ways depending upon tissue of origin (histological, histopathological or embryonal), anatomical site (eyeball, lacrimal gland, eyelids etc.), and clinical course (acute, chronic etc.). One of the commonest and useful classifications is Primary, Secondary & Metastatic according to the site of origin [2] . The orbital contents include eyeball, optic nerve, main trunks/branches of arteries, veins, and cranial nerves III to VI, lacrimal gland, extraocular muscles, smooth muscles, orbital fat, ligaments, orbital fascia (including periorbita―the periosteal lining of orbit) and skin with its appendages [3] . Orbital lesions can occur in any age group or in either gender, but it has been observed that those arising at a younger age especially malignancies tend to behave more aggressively and an earlier diagnosis and prompt appropriate treatment can result in better prognosis [4] .

This descriptive case series was undertaken to analyze different orbital lesions presented during a period of 17 years. The subjects included those who visited Eye Department of Mayo Hospital Lahore, Pakistan during 17 years from 1996 till 2012. This study was undertaken in accordance with Declaration of Helsinki (1964 including its amendments) after approval from Ethical Committee of King Edward Medical University. Out of 1637 cases, 1246 cases of orbital lesions, who gave informed consent and completed the study with complete clinical records, were included in the analysis; the remaining 391 comprised those who left against the medical advice, were lost to follow up or never reported back after being referred/shifted to other departments like Otolaryngology, Neurosurgery or Oncology departments. After detailed history, examination and routine investigations, necessary investigations like Orbital/Ocular Ultrasonography (B Scan), X Ray Orbit/Paranasal sinuses/Cranium, CT scan and Magnetic Resonance Imaging (MRI) were performed. Surgery (usually orbitotomy) was performed when a definite space occupying lesion was identified during investigations. In some cases only biopsy was done to establish a histopathological diagnosis.

Out of 1246 patients, 57.46% (n = 716) were adults and 42.53% (n = 530) children. Out of all cases 54.57% (n = 680) were neoplastic and 45.42% (n = 566) nonneoplastic lesions. Amongst the neoplastic lesions 86.17% (n = 586) were malignant and 13.82% (n = 94) were benign. These lesions were divided into following four groups based on their site of origin:

§ Primary Orbital Lesions, which originated from the tissues of the orbit. Eye ball being a part of the orbit; therefore its lesions are included in the primary category.

§ Secondary Orbital Lesions, which originated from the adjacent structure like Eyelids, Paranasal sinuses, cranial cavity or nasopharynx and invaded the orbit secondarily.

§ Haematopoeitic Reticuloendothelial system lesions.

§ Metastatic, with primary in the distant organs.

Primary orbital lesions were the most common orbital lesions being 963 (77.29%) (Figure 1; Table 1) followed by secondary orbital lesions 232 (18.62%) (Figure 1; Table 2), hematopoietic reticuloendothelial 47 (3.77%) (Figure 1; Table 3) and metastatic 04 (0.32%) lesions (Figure 1; Table 4).

Orbital lesions can be derived from the structures located in the orbit or from the structures surrounding it. Sometimes a distant lesion such as a malignant tumour somewhere else in the body may seed into it. The most common mode of presentation is displacement of the eyeball or proptosis particularly if the lesion is intra-conal. The displacement could be axial (strictly forwards) or non-axial (upwards or downwards in addition to forward displacement). Other presentations could take the form of a palpable tumour which may become a fungating mass if tumour is malignant and sufficient time has elapsed.

The current study has revealed that orbital lesions are more common in adults 57.46% (n = 716) as compared to children 42.53% (n = 530). Parashkevova found similar distribution according to age in her patients and found that majority (61%) of patients presented in the sixth and the seventh decade [5] .

In our study it was found that neoplastic lesions 54.57% (n = 680) are common than non neoplastic lesions 45.42% (n = 566) and amongst the neoplastic lesions, malignant lesions 86.17% (n = 586) are more common than benign 13.82% (n = 94). Demirci found similar results where malignant tumors were more common than benign tumors. Out of all cases, 63% presented with malignancy and 27% were benign [6] . Similar findings are also reported by Parashkevova who found 56% cases of malignant tumors and 44% cases of benign tumors over the period of 4 years [5] . In contrast to this, another study on analysis of space occupying lesions of orbit showed that out of the 2480 lesions, 1697 (68%) were benign and 783 (32%) were malignant. The most frequent benign tumors were dermoid cyst (14%) and cavernous hemangioma (9%). The most common malignant tumors were non-Hodgkin lymphoma (12%), basal cell carcinoma (3%), and orbital metastases (3%) [7] .

Ohtsuka studied orbital tumors in Japanese patients over a period of 20 years and found that out of all patients, 89% were primary orbital tumors whereas 9% were secondary tumors originating from neighbouring areas of orbit and 2% were metastatic tumors [8] . These findings are well aligned with those of our study where Primary orbital lesions originating from the tissues of the orbit, including eyeball, are the most common orbital lesions followed by the secondary orbital lesions, originating from the adjacent structure (eyelids, paranasal sinuses, nasopharynx & cranial cavity), lesions of the haemopoeitic reticuloendothelial system lesions and metastatic lesions. In 2008, a study conducted by Angotti-Neto reported similar results in 11-year histopathalogical analysis of orbital tumors. He found that out that of the studied 181 orbital space-occupying lesions, 70% were primary, 23% secondary, 6% metastatic and lymphomas, and 1% was not classified [9] .

Orbital lesions are more common in adults 57.46% (n = 716) as compared to children 42.53% (n = 530). Neoplastic lesions 54.57% (n = 680) are more common than nonneoplastic lesions 45.42% (n = 566), and amongst the neoplastic lesions, malignant lesions 86.17% (n = 586) are more common than benign 13.82% (n = 94). Primary orbital lesions originating from the tissues of the orbita, including eyeball, are the most common orbital lesions followed by the secondary orbital lesions, originating from the adjacent structure (eyelids, paranasal sinuses, nasopharynx & cranial cavity), lesions of the haemopoitic reticuloendothelial system lesions and metastatic lesions.

Amongst the primary orbital lesions, retinoblastoma, nonspecific inflammations, fungal and tuberculous granulomas, pseudotumours, dermoid cysts, adenocystic carcinoma & pleomorphic adenoma of lacrimal gland, cavernous haemangioma, optic nerve Glioma and meningioma, neurofibroma, rhabdomyosarcoma are the common orbital lesions. Amongst secondary orbital lesions, squamous cell carcinoma of the eyelid, chronic eth- moiditis and maxillary antrum carcinoma are the common lesions. Lymphomas/leukemias are also seen in good percentage in reticuloendothelial system lesions whereas metastatic lesions are very uncommon.